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INFR4SG09d

A REVIEW OF ADVANCED SEWER SYSTEM DESIGNS AND TECHNOLOGIES

by: Simon Lauwo Dr. Sybil Sharvelle (PI) Dr. Larry Roesner (Co-PI)

Colorado State University

2012

The Water Environment Research Foundation, a not-for-profit organization, funds and manages water quality research for its subscribers through a diverse public-private partnership between municipal utilities, corporations, academia, industry, and the federal government. WERF subscribers include municipal and regional water and utilities, industrial corporations, environmental engineering firms, and others that share a commitment to cost-effective water quality solutions. WERF is dedicated to advancing science and technology addressing water quality issues as they impact water resources, the atmosphere, the lands, and quality of life.

For more information, contact: Water Environment Research Foundation 635 Slaters Lane, Suite G-110 Alexandria, VA 22314-1177 Tel: (571) 384-2100 Fax: (703) 299-0742 www.werf.org [email protected]

This report was co-published by the following organization.

IWA Publishing Alliance House, 12 Caxton Street SW1H 0QS, Tel: +44 (0) 20 7654 5500 Fax: +44 (0) 20 7654 5555 www.iwapublishing.com [email protected]

© Copyright 2012 by the Water Environment Research Foundation. All rights reserved. Permission to copy must be obtained from the Water Environment Research Foundation. Library of Congress Catalog Card Number: 2011931423 Printed in the of America IWAP ISBN: 978-1-78040-025-9/1-78040-025-X

This report was prepared by the organization(s) named below as an account of work sponsored by the Water Environment Research Foundation (WERF). Neither WERF, members of WERF, the organization(s) named below, nor any person acting on their behalf: (a) makes any warranty, express or implied, with respect to the use of any information, apparatus, method, or process disclosed in this report or that such use may not infringe on privately owned rights; or (b) assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method, or process disclosed in this report.

Colorado State University

The research on which this report is based was developed, in part, by the United States Environmental Protection Agency (EPA) through Cooperative Agreement No. CR-83419201-0 with the Water Environment Research Foundation (WERF). However, the views expressed in this document are not necessarily those of the EPA and EPA does not endorse any products or commercial services mentioned in this publication. This report is a publication of WERF, not EPA. Funds awarded under the Cooperative Agreement cited above were not used for editorial services, reproduction, printing, or distribution.

This document was reviewed by a panel of independent experts selected by WERF. Mention of trade names or commercial products or services does not constitute endorsement or recommendations for use. Similarly, omission of products or trade names indicates nothing concerning WERF's or EPA's positions regarding product effectiveness or applicability.

ii

ACKNOWLEDGMENTS

Research Team Principal Investigators: Sybil Sharvelle, Ph.D. Larry Roesner, Ph.D. Colorado State University – Department of Civil and Environmental Engineering

Project Team: Simon Lauwo Colorado State University – Department of Civil and Environmental Engineering

WERF Project Subcommittee Michael Borst U.S. Environmental Protection Agency Richard Field, P.E. U.S. Environmental Protection Agency Thomas O’Connor U.S. Environmental Protection Agency Mary Stinson U.S. Environmental Protection Agency (retired) Daniel Murray U.S. Environmental Protection Agency Swarna Muthukrishnan, Ph.D. American Water Jian Yang, Ph.D., P.E. American Water

Innovative Infrastructure Research Committee Members Steve Whipp United Utilities North West Daniel Murray U.S. Environmental Protection Agency Stephen P. Allbee U.S. Environmental Protection Agency Michael Royer U.S. Environmental Protection Agency Kevin Hadden Orange County District Kendall M. Jacob, P.E. Cobb County Water

A Review of Advanced Sewer System Designs and Technologies iii Frank Blaha Water Research Foundation David Hughes American Water Peter Gaewski, MS, P.E. Tata & Howard, Inc. Jeff Leighton City of Portland Water Bureau Walter L. Graf, Jr. WERF Program Director Daniel M. Woltering, Ph.D. WERF Director of Research – IIRC Chair

Water Environment Research Foundation Staff Director of Research Daniel M. Woltering, Ph.D. Program Director Walter L. Graf, Jr. Senior Program Director Jeff Moeller, P.E.

iv ABSTRACT AND BENEFITS

Abstract: This document seeks to collect into one place current and new technologies about system design. The document organizes the information found in the 295 documents that were reviewed into six subject areas: Advanced Onsite Technologies; Alternative Wastewater Collection System Designs and Technologies; System Design and Technology; Detection and Control Technologies; Sewer Construction/Rehabilitation Technologies; and Materials and Joints. Each of the six subject areas is further subdivided into three technology levels: Established Technologies; Proven Technologies; and Experimental and Foreign Technologies. The results are summarized in tabular form for easy review and comparison, followed by descriptions of each of the listed technologies. The descriptive section contains information on how the various designs and technologies work, their cost and performance, advantages and disadvantages, locations where the design or technology is in use, and identification of manufacturers of various technologies.

Benefits:  Provides a single, comprehensive summary of advanced sewerage system design and technology.

Keywords: Advanced sewerage design, overflow, overflow, inflow and infiltration, onsite wastewater.

A Review of Advanced Sewer System Designs and Technologies v

TABLE OF CONTENTS

Acknowledgments...... iii Abstract and Benefits ...... v List of Tables ...... viii List of Figures ...... viii List of Acronyms ...... x Executive Summary ...... ES-1

1.0 Introduction ...... 1-1 1.1 Introduction ...... 1-1 1.2 Objective of this Document ...... 1-1 1.3 Document Organization ...... 1-2 1.4 Overview of Sewer Systems ...... 1-3 1.4.1 Gravity Sewer Systems ...... 1-3 1.4.2 Pressure Sewer Systems ...... 1-3 1.4.3 System ...... 1-3 1.4.4 Small Diameter Gravity Sewer ...... 1-4 1.4.5 Hybrid Sewer System ...... 1-4 1.5 Performance Issues in Gravity Sewer Systems ...... 1-4 1.5.1 Performance and Cost Issues in Combined Sewer Systems (CSS) ...... 1-5 1.5.2 Performance and Cost Issues in Sanitary Sewer Systems (SSS) ...... 1-5 1.6 Performance and Cost Issues in Alternative Wastewater Collection Systems .... 1-6 1.7 Comparison between Gravity and Alternative Wastewater Collection Systems ... 1-7 1.8 Summary ...... 1-7

2.0 Summary of Advanced Sewer System Design and Technologies ...... 2-1 2.1 Sewer Conveyance System Design and Technologies Literature Selection and Classification Criteria ...... 2-1

3.0 Onsite Technologies ...... 3-1 3.1 Designs and Technologies ...... 3-1 3.2 Water Efficient Toilet Designs and Technologies ...... 3-1 3.2.1 Established Water Efficient Toilet Designs and Technologies...... 3-2 3.2.2 Waterless Toilet Designs and Technologies ...... 3-3 3.2.3 Foreign and Experimental Water Efficient Toilet Designs and Technologies ...... 3-8 3.2.4 Source-Nutrient Control Designs and Technologies ...... 3-12 3.2.5 Onsite Disposal Sewer System Designs and Technologies ...... 3-16 3.2.6 Septic System Innovative Designs and Technologies ...... 3-21

4.0 Alternative Wastewater Collection System Design and Technologies ...... 4-1 4.1 Pressure Sewer System Designs and Technologies ...... 4-1 4.1.1 Established Pressure Sewer System Designs and Technologies...... 4-1 4.2 Innovative Designs and Technologies in Pressure Sewer Systems ...... 4-7

vi 4.2.1 Foreign and Experimental Designs and Technologies for Pressure Sewer Systems ...... 4-7 4.3 Vacuum Sewer System Designs and Technologies ...... 4-7 4.3.1 Old Vacuum System Designs and Technologies ...... 111 4.3.2 Innovative Proven Vacuum Designs and Technologies ...... 4-12 4.3.3 Foreign and Experimental Designs and Technologies for Vacuum Sewers ...... 4-16 4.4 Small Diameter Gravity () Sewer System (SDGS) Designs ...... 4-17 4.4.1 Established Designs and Technologies ...... 4-17 4.4.2 Innovative Proven Designs and Technologies ...... 4-18 4.4.3 Foreign and Experimental Designs and Technologies ...... 4-19 4.5 Hybrid Sewer System Designs...... 4-21

5.0 Gravity Sewer System Design ...... 5-1 5.1 Combined Sewer System (CSS) Established Designs and Technologies ...... 5-1 5.2 Proven Designs and Technologies for CSS ...... 5-4 5.3 Experimental and Foreign CSS Designs and Technologies ...... 5-6 5.4 Separate Sanitary Sewer (SSS) System Design and Technology ...... 5-6 5.4.1 Established SSS Designs and Technologies ...... 5-7 5.4.2 Proven Design and Technologies in SSS ...... 5-9 5.4.3 Experimental and Foreign Technologies ...... 5-10

6.0 Techniques for Infiltration Detection and Control ...... 6-1 6.1 Conventional techniques for infiltration detection and Control ...... 6-1 6.2 Advanced Techniques for Infiltration Detection and Control ...... 6-3 6.2.1 Infiltration Detection Techniques ...... 6-4 6.2.2 Infiltration Control Techniques...... 6-5 6.3 Experimental and Foreign Infiltration Detection and Control Technologies ...... 6-5 6.3.1 Infiltration Detection Techniques ...... 6-5 6.3.2 Inflow Reduction Technologies ...... 111 6.4 Sediments and Solids Control Techniques in Sewer Collection System ...... 6-12

7.0 Sewer Construction/Rehabilitation Technologies To Control I&I And SSOs ... 7-1 7.1 Established Sewer Repair, Rehabilitation, and Construction Technologies ...... 7-1 7.2 Proven Advanced Sewer Rehabilitation/Construction Technologies ...... 7-2 7.2.1 Trenchless Technologies ...... 7-6 7.3 Experimental and Foreign Technologies in Sewer Construction and Rehabilitation ...... 7-10

8.0 Pipe Materials and Joints for Sewer Systems Designs ...... 8-1 8.1 Established Sewer Pipe Materials ...... 8-1 8.2 Innovative Proven Pipe Materials and Joints ...... 8-2 8.3 Experimental and Foreign Pipe Materials and Joints ...... 8-4 8.4 Synthesis of the Pipe Materials and Joints in Sewer Collection System Design ... 8-5

References ...... R-1

A Review of Advanced Sewer System Designs and Technologies vii

LIST OF TABLES

2-1 Advanced Sewerage System Design and Technology Summary Table ...... 2-3 4-1 Countries with Vacuum Sewer Systems ...... 4-16 4-2 Installation Cost for Valve Pit and Appurtenances (4th quarter 2006) ...... 4-16

LIST OF FIGURES

3-1 Ultra Low-Flow Toilet ...... 3-3 3-2 ...... 3-4 3-3 An Electric ...... 3-6 3-4 Oil Recirculating Toilet ...... 3-7 3-5 Urine Separation Toilet ...... 3-9 3-6a Conventional ...... 3-10 3-6b Waterless Urinal ...... 3-10 3-6c Depiction of How Waterless Oil Barrier Work ...... 3-10 3-7 Graywater and System Plumbing ...... 3-13 3-8 Drip System ...... 3-13 3-9 Subsurface Irrigation ...... 3-13 3-10 Graywater for Toilet Flushing ...... 3-14 3-11 Components and Layout for the Recommended Graywater Irrigation System in the U.S...... 3-15 3-12 Components for the Recommended Graywater Reuse System for Toilet Flushing in the U.S...... 3-15 3-13 A Septic System ...... 3-17 3-14 and Absorption Trench Field ...... 3-17 3-15 Conventional Drain Field Designs ...... 3-19 3-15a Mound ...... 3-19 3-15b Intermittent Sand Filters ...... 3-19 3-15c Evapotranspiration System ...... 3-19 3-15d Free Water Surface Wetland ...... 3-20 3-15e Shallow Trench ...... 3-20 3-15f UV Disinfection System ...... 3-20 3-16 Dual-Compartment Septic Tank with Sanitary Tees and Gas Deflector ...... 3-22 3-17 Septic Tank Effluent Screen ...... 3-23 3-18 Low Pressure Pipe System ...... 3-24 3-19 Sand Filter Control Panel ...... 3-26 3-20 Advanced Enviro Septic® System Treatment Components ...... 3-27 3-21 Advanced Enviro Septic® Pipe Design: 10 Steps of Treatment ...... 3-28 4-1 Grinder Package System ...... 4-2 4-2 System ...... 4-3

viii 4-3 STEP System ...... 4-5 4-4a Vacuum Sewer System ...... 4-9 4-4b Vacuum Sewer Pipeline ...... 4-9 4-5 Components of a Vacuum Station ...... 4-10 4-6 Reform Pocket Sewer Collection Pipeline Design ...... 4-11 4-7 New Saw Tooth Sewer Collection Pipeline Design ...... 4-12 4-8 New In Sump Breather System with Air Intake Pipe ...... 4-13 4-9 Modern Collection Pit ...... 4-14 4-10 Small Diameter Gravity (Effluent) Sewer ...... 4-17 4-11 Small Bore SewerTM System Access Point ...... 4-20 5-1 Typical Combined Sewer System Design Layout ...... 5-2 5-2 Locations with CSS in the United States ...... 5-4 5-3 SSO Occurrence by Cause ...... 5-7 5-4 Separate Sanitary Sewer System (SSS) Configuration ...... 5-8 6-1 Infiltration Sources...... 6-1 6-2 Infiltration in Sewer Pipeline ...... 6-2 6-3 Root Intrusion ...... 6-3 6-4 Root Removal by Root Cutter...... 6-3 6-5 Epoxy Lining ...... 6-5 6-6 Optical and Sensor Equipment in the KARO Robot ...... 6-7 6-7 Panoramo Unit System ...... 6-9 6-8 A View of Digital Scanning Elevation Technology (DSET) ...... 6-10 6-9 Wave Impedance Probe (WIP) Unit Lowered into the ...... 6-11 6-10 The Sequence of Hydrass® Sewer Flushing Gate in Operation… ...... 6-13 7-1 Sliplining Technique ...... 7-3 7-2 Cured in Place Procedure ...... 7-4 7-3 Fold and Form Technique…………………………… ...... 7-4 7-4 Chemical Grouting to Seal the Manhole ...... 7-5 7-5 Grouting ...... 7-6 7-6 Horizontal Directional Drilling ...... 7-7 7-7 Pipe Ramming ...... 7-8 7-8 Pipe Bursting Technique ...... 7-9 7-9 Robotic Repair of Sewer Joint ...... 7-10 7-10 Lateral Connection Before, During and After Robotic Repair ...... 7-10 7-11 Pipe Rehabilitation Process Using VARTM ...... 7-11

A Review of Advanced Sewer System Designs and Technologies ix

LIST OF ACRONYMS

ASCE American Society of Civil Engineers AWWA American Water Works Association CIPP Cured-in-Place Pipe DIP Ductile Iron Pipe CCTV Close Circuit Television CSS Combined Sewer Systems CSO Combined Sewer Overflows EPA Environmental Protection Agency FRP Fiberglass-Reinforced Pipe GRP Glass-Reinforced Plastic HDPE High-Density Polyethylene HPPE High-Performance Polyethylene I&I Infiltration and Inflow PCCP Prestressed Concrete Cylinder Pipe PE Polyethylene PE X Cross-Linked Polyester PRP Polyester-Reinforced Pipe RCP Pipe SDGS Small-Diameter Gravity/ SSO Sanitary Sewer Overflows SSS Separate Sanitary Sewer U.S. EPA U.S. Environmental Protection Agency VCP Vitrified Clay Pipe WEF Water Environmental Federation WERF Water Environmental Research Foundation WWTP Plant

x EXECUTIVE SUMMARY

The manner in which urban wastewater systems are designed and operated has not changed much since the time of the Roman civilization. By the beginning of the 18thth century, street sewers were being replaced with gravity sewer systems in Europe, and eventually around the world. The basic design protocol for sewer systems has changed little in the last two centuries. But as our cities grow, the (treated) wastewater loads from these systems places greater and greater pressure on our , , and estuary receiving water systems, and environmental agencies are tightening the wastewater treatment plant (WWTP) effluent water quality requirements in response to these increasing loads. In addition, the aging sewer system infrastructure has resulted in increased wet weather related raw overflows from the sewer systems to the receiving waters. So, we begin to wonder if there might be a better way to manage wastewater in the urban environment. Over the years, a number of new and advanced technologies have been developed for wastewater collection and for rehabilitation of existing systems. But the new technologies have not been widely applied due to their higher capital and/or operating cost, and the lack of knowledge and experience with these systems by wastewater utilities. Rehabilitation technologies are now big business in the wastewater management industry, but these techniques are not much cheaper than sewer replacement. Perhaps their biggest advantage is reduced disruption of surface activity as the sewer lines are repaired. So the question remains, is there a better way? This document seeks to gather the current and new technologies about, or related to sewerage system design so that wastewater professionals can easily learn about them. The document summarizes the information found in 295 documents that were reviewed for this study, characterizing them under the following categories:  Advanced Onsite Technologies  Alternative Wastewater Collection System Designs and Technologies  Gravity Sewer System Design and Technology  Infiltration Detection and Control Technologies  Sewer Construction/Rehabilitation Technologies  Pipe Materials and Joints The categories are further subdivided into: 1. Established Technologies 2. Proven Technologies; 3. Experimental and Foreign Technologies Technologies are divided as such in Chapter 2.0, in tabular form. In the remainder of the document, these technologies are described in detail, providing functionality and cost, as well as advantages and disadvantages. In some cases, information on repair, replacement, and best management practices for extending technology’s life expectancy are also incorporated into the discussion.

A Review of Advanced Sewer System Designs and Technologies ES-1 Reflecting on the results of this literature search, there are many interesting approaches to design of wastewater collection systems, yet gravity sewer systems have been adopted almost exclusively by municipalities, small and large, around the world. In the United States alone, gravity sewer systems number over 21,000 and comprise more than 1.2M miles of pipe. The number and extent of alternative wastewater collection systems in the United States is an insignificant fraction of this number. The only new technologies that have been used extensively are those applicable to gravity sewer rehabilitation brought about by regulatory agency enforcement actions in response to problems. The implementation of the other technologies seems to be limited to urban developments for which a gravity system is not technically feasible, such as cluster developments in remote areas far from the treatment plant, and in hilly terrain. Why is this? The principal reasons seem to be that conventional gravity sewer systems are a more cost-effective and energy efficient method of collecting and conveying sewer water in large, densely populated areas compared to alternative wastewater collection systems. Under normal circumstances a conventional gravity sewer will be favored because the alternative sewer collection system design requires several additional components which are not required in conventional gravity sewer systems, including septic tanks, elevation pumps, vacuum pumps, valves and other components. In some cases these additional costs may create a tradeoff with the excavation cost for conventional sewer system installation, but probably not enough to justify going to a different system in view of other factors. Alternative sewer systems usually require electrical power to operate, resulting in additional energy costs compared to a conventional gravity sewer system, which, if well designed, can operate entirely by gravity flow. Another disadvantage of alternative sewer systems is that sewer service disruption can occur due to power outages or mechanical breakdown of a component. Another significant, albeit undocumented, driver is that the design, maintenance, and operation of these systems are well understood by municipal and regulatory agencies. They know how these systems behave and have confidence that they can be made to reliably meet water quality regulatory criteria. On the other hand, the lack of knowledge on the performance reliability of the advanced wastewater collection systems by most municipal and regulatory agencies makes them uncomfortable with these systems. So, it seems that these advanced technologies will not receive more attention in the future than they have in the past unless there is some economic or regulatory incentive to do so. But perhaps some other drivers will develop as a result of new water management strategies being looked at by municipal utilities, especially measures for indoor water use. Toilet manufacturers have recently begun producing that use 1.28 gallons per flush (gpf), and very recently, some manufacturers are offering toilets with 0.8 gpf; and water utilities are offering rebates for customers to retrofit these devices in developed areas where the sewers were designed to handle toilets with 5 gpf. This means that solids in the toilet water have potential to increase by a factor of 6. Furthermore, as the movement for graywater reuse for toilet flushing and irrigation grows in popularity, the potential exists to reduce existing residential wastewater flows by about 50%, increasing blackwater solids concentrations by a factor of 2. Experience in indicates that existing sewers designed for higher flows and lower solids concentrations cannot handle the high solids loads, and some municipalities are installing vacuum sewers to move wastewater flows to the treatment plant. The problem is that large vacuum systems have a lot of moving parts and are high maintenance. So it seems that some new out-of-the-box thinking with regard to how advanced wastewater collection systems might be

ES-2 cost-effectively brought to bear on this problem is in order. For example, a municipality might consider a standard gravity system at the neighborhood scale to bring wastewater to a central point; then a force main system might be used to move the wastewater from the neighborhood collection points to the treatment plant. If the neighborhood gravity system will not work, perhaps a vacuum system could be used at the neighborhood scale, and be coupled to a force main system from the neighborhood to the treatment plant. It might be argued that the solids be removed at the neighborhood scale and gravity sewers could then handle the cleaner flow, but then solids must be handled at a neighborhood scale. Yet another factor to consider is that as the solids concentrations increases in the wastewater, it becomes more amenable to anaerobic treatment, which produces energy rather than consuming it as does aerobic treatment. Perhaps the energy production from will more than offset the cost of the new system. It is recommended that the evolution of the quantity and quality of sewer flows that will result as a consequence of the implementation of residential water conservation practices by water utilities be examined in light of how wastewater will be collected and treated. The researchers suggest that the answer will be found in some combination of the advanced wastewater collection systems inventoried here, perhaps in combination with a gravity system.

A Review of Advanced Sewer System Designs and Technologies ES-3

ES-4 CHAPTER 1.0

INTRODUCTION

1.1 Introduction Sewer system design and application date back to ancient times, and many of the technologies used in past centuries are still seen in today’s sewer systems, partially because some of these systems are centuries old, and secondly, there has been no real economic incentive to change the way we provide sewerage services. Since the beginning of the 18thth century, gravity sewer systems have been commonly applied in the United States (U.S.). Gravity sewer systems are used in both developed and developing countries. Gravity sewer systems are generally classed as either Separate Sanitary Sewers (SSS) or Combined Sewer Systems (CSS). Both SSS and CSS have major performance and cost issues. The main problems reported are sanitary sewer overflows (SSO’s), combined sewer overflows (CSOs), infiltration and inflows (I&I), and high construction and maintenance/rehabilitation costs. Sewer overflows from these systems are a major source of resulting in issues and aquatic life concerns. High cost of rehabilitation and/or replacement has deterred sewer utilities from mobilizing resources and replacing these old technologies with new technologies. Nevertheless, the development of better sewer systems that can meet a variety of community and municipal needs has been ongoing. Demand for advanced scientific innovations and techniques in collection sewer systems continues to increase as the urban population increases, new contaminants emerge, and effluent standard requirements become more stringent. Some of these alternatives for sewer system designs have been developed and some of these new innovative systems are in full operation, while others are still evolving. New innovative sewer systems, commonly referred to as alternative wastewater collection system designs, include pressure sewer systems, vacuum sewer systems, and small diameter gravity sewer systems. U.S. EPA has been particularly interested in advanced sewer system design approaches because of the negative environmental impacts that current state of practice designs cause. Adverse impacts, including human health threats and pollution of receiving surface waters, result from combined sewer and sanitary sewer system overflows and exfiltration from the systems to the groundwater due to structural failures in the sewer systems. To respond to these critical challenges facing the U.S. sewer infrastructure, the EPA’s Office of Research and Development (ORD) is supporting a Sustainable Infrastructure Initiative research program in the area of advanced design and engineering concepts related to the application or adoption of new and innovative infrastructure design and technologies (EPA-ORD-NRMRL-CI-08-03). This report is one of the tasks being conducted under this program. 1.2 Objective of this Document For the past 100 years, technical knowledge about how to handle wastewater to minimize its impact to human health and environment has substantially increased. In today’s world, public expectation on wastewater system performance has become very high. Stringent discharge standards for wastewater systems have been set by regulatory authorities and utilities across the U.S. are struggling to meet these high standards. To address existing sewer design problems and

A Review of Advanced Sewer System Designs and Technologies 1-1 meet 21st century discharge standards, and to insure sustainability of urban water resources, a number of technologies have been developed but few of them have been widely adopted in the sewer industry. The objective of this work is to conduct a detailed valuation of applicability of new and developing wastewater collection system designs and technologies. Ultimately, the goal is to summarize what we know and what we don’t know, what seems practical for near term implementation, and which technologies look promising but need more research and development. Focus will be on how advanced sewerage system designs and technology can be applied to improve new and existing sewer system performance, energy consumption, operation cost, construction cost, life expectancy, and environmental quality. 1.3 Document Organization This report includes the following chapters: Chapter 1.0 – Introduction to the main topics associated with advanced sewer system designs and technologies covered in this document. Chapter 2.0 – Summary tables present all advanced sewer system designs and technologies that were collected from the literature review. The summary table classifies the advanced sewer system designs and technologies into three main groups: established technologies, proven technologies, and experimental and foreign technologies. The references for each technology are included as a number in parenthesis which indicates the reference number of the literature cited. Chapter 3.0 – Advanced Onsite Technologies are described and include water efficient toilet designs, source/nutrient control in fixture designs, and onsite wastewater system designs and technologies. The descriptions may include how a particular technology is designed, how it works, what the advantages and disadvantages of that technology are, known performance issues, where a particular technology is in use in the U.S. and around the world, how much it costs to install and the manufacturers for a particular design or technology. Chapter 4.0 – Alternative Wastewater Collection System Designs and Technologies are covered in this chapter. Systems include pressure, vacuum, small diameter gravity, and hybrid sewer designs and technologies. The information for a particular technology is organized by providing a short description of its design, how it works (diagrams are provided when possible), advantages and disadvantages of a particular design, reported performance successes and limitations, cost of that system to a household, compatibility of the alternative sewer system design with the existing sewer systems, and where in the U.S. and outside the U.S. a particular technology is currently in use. Chapter 5.0 – Gravity Sewer System Design and Technology is divided into Combined Sewer System (CSS) Designs and Separate Sanitary Sewer (SSS) System Designs and Technology. Chapter 6.0 – Infiltration Detection and Control Technologies focuses on sewer infiltration control, inflow reduction, private sewer lateral management and sediment control or solids control in sewer system designs. Technologies discussed include . Chapter 7.0 – Sewer Construction/Rehabilitation Technologies addresses sewer system repair, rehabilitation, replacement and construction designs and technologies. Chapter 8.0 – Pipe Materials and Joints in sewer system designs and technologies are reviewed. This includes established sewer pipe materials, innovative proven pipe materials, foreign, and experimental materials.

1-2 1.4 Overview of Sewer Systems This report assumes that the reader has a basic understanding of the state of practice related to sewerage system design, operation and maintenance. This section is not intended to be a comprehensive review of current practice, but rather, to define the baseline for current practice in order to properly put into context “advanced sewer system design and technologies.” 1.4.1 Gravity Sewer Systems Gravity sewer systems have been adopted almost exclusively by municipalities, small and large, around the world. In a gravity sewer system, pipes are installed on a slope that causes wastewater to flow by gravity from the household to the wastewater treatment plant. Pipes are sized with straight alignment and a uniform gradient to maintain self-cleansing velocities. Gravity sewers are typically installed at a depth of one meter (three feet) and to a maximum of 7.6 meters (25 feet). [222] Gravity sewer systems can be designed as CSS, or SSS; however, in the U.S. construction of new CSS is prohibited. Material used for gravity sewer conveyance system includes reinforced concrete pipes (RCP), reinforced concrete boxes, concrete pipes, ductile iron pipes, vitrified clay pipes (VCP), brick arches, asbestos cement pipes (ASP), plastic pipes, polyvinyl chloride pipes (PVC), and Centrifugally Cast Fiberglass Reinforced Polymer Mortar (CCFRPM) pipes. Spacing of sewer maintenance ranges from 400-900 ft. Manholes are also provided under the following conditions: at both ends of horizontal curves, at the intermediate point of a curve with angle greater than 90°, at the point of reverse curve, at abrupt change in vertical alignment, at changes in pipe size, and the confluence of three or more pipes. The minimum inner diameter of manholes ranges between four feet and six feet. 1.4.2 Pressure Sewer Systems A pressure sewer system comprises a small diameter pipeline, shallowly buried, and follows the ground profile. Sewerage flows through this system under pressure head generated by a pump. Typical main pipe diameters range between two inches to six inches. Polyvinyl chloride (PVC) is the common piping material. The pipelines are buried at a 30-inch minimum depth. A grinder pump system with one to two horsepower serves individual homes, and grinds solids prior to discharge to the main sewer system. Alternatively, a septic tank effluent pump (STEP) system can be used instead of a grinder pump system to push the wastewater through the system. In a STEP system, the operating pressure can be over 100psi. Pressure sewer systems are often used in rocky areas, areas with high groundwater table, around lake areas where homes are built fronting the lake, and in flat terrains. Examples of pressure sewer systems in United States are Horseshoe Bay, TX, Kingsland, TX, Saw Creek, PA, Anne Arundel Co., MD, Port St. Lucie, FL, Buckeye Lake, OH and Palm Coast, FL.[209] 1.4.3 Vacuum Sewer System The vacuum sewer system was first invented by Adrian LeMarquand in 1888; however, the first commercial application was not developed until 1959 by Electrolux of Sweden. The vacuum sewer system consists of three major components: a service holding tank/valve pit, a collection piping/vacuum main and a vacuum station. In vacuum sewer systems, wastewater flows by gravity away from the building through a small diameter PVC pipe to a sump and valve pit. A vacuum valve located inside the valve pit provides the interface between the collection main (vacuum main) and the sump, which is under atmospheric pressure. When 10 gallons of sewerage accumulates in the sump, the interface valve opens automatically and the sewerage is immediately sucked into the collection main. This is done without the use of electricity by the

A Review of Advanced Sewer System Designs and Technologies 1-3 vacuum valve. At the vacuum station a negative pressure is created by a sump which maintains a vacuum inside the collection main pipes, relative to atmospheric pressure. [215] The collection system pipes range in size between three and 10 inches. Pipe material is generally solvent welded PVC, HDPE, and O-ring rubber gasketed pipes. The vacuum station creates a negative pressure between 16-20in of mercury. This negative pressure provides the energy that moves the sewerage at a velocity of 15-18fps. This system can be used in areas with unstable soils, flat terrain, high water table, semi-urban/rural areas, rocky ground, and when the wastewater is of higher solids concentration. [209] The vacuum sewer was first used in the Bahamas in the 1960s. In 1991, there were approximately 45 communities the U.S. that had adopted the vacuum sewer system, including St. Michaels, MD, Martinsville, IN, and Greenback, VA. 1.4.4 Small Diameter Gravity Sewer The small diameter gravity sewer (SDGS) is another advanced sewer system that provides primary treatment of the wastewater at each connection and releases pretreated wastewater to the collection main. SDGS was first used in Australia in the 1960s and is considered to be cost-effective compared to other sewer system designs as the construction cost is reduced by 30-65%. This system consists of a house connection, interceptor tank, service laterals, collection mains, cleanouts, manholes, vents and lift stations. An interceptor tank or septic tank, with a detention time of 12-24 hours, collects the suspended solids from the house connection and then releases the pretreated wastewater to the service lateral which connects to the collection main. A well-designed septic tank can remove up to 50% of biological oxygen demand (BOD5), 75% of suspended solids, 90% of grease, and all grit. The typical diameter of service main pipes is three to four inches, with a slope of two percent. The collection main is also three to four inches in diameter and it maintains a 1.5 fps velocity compared to a 2.5 fps velocity requirement for conventional gravity sewers. If no heavy earth or vehicle loading is expected, the buried pipe depth is 2-2.5 feet. In the U.S, small diameter gravity sewers were first introduced in the mid-1970s in Mt. Andrew, AL and Westboro, WI. Due to low cost of installation and operation of this system, many small communities adopted the technology. In 1986, over 100 systems were constructed in the U.S. following the Australian guidelines. In the 1990s, about 200 small diameter pipe sewer systems were fully operational. [209] By 2000, approximately 250 SDGS systems had been financed by the U.S. EPA’s construction program and many more had been financed by local and private funding. [222] 1.4.5 Hybrid Sewer System The hybrid sewer system is a design that combines two or more of the above sewer system designs into one functional system. Examples of hybrid sewer systems are a combination of pressure sewer and gravity sewer, vacuum sewer and gravity sewer or a combination of vacuum sewer, pressure sewer and gravity sewer. 1.5 Performance Issues in Gravity Sewer Systems The EPA’s Office of Water (OW) conducted a study in 2002 to assess the challenges facing U.S. water and wastewater utilities. [247] Major issues reported were aging infrastructure, deteriorating infrastructure, and raw sewer overflows from the conventional gravity sewer system. The U.S. has more than 16,200 wastewater treatment facilities and 21,200 sewer systems comprising approximately 725,000 miles of publicly owned pipes and 500,000 miles of privately owned pipes. The age of these sewer systems range from new to more than 100 years old.

1-4 1.5.1 Performance and Cost Issues in Combined Sewer Systems (CSS) A CSS carries sewage from residential as well as industrial and commercial locations, plus runoff through a single pipe to a wastewater treatment plant during dry weather periods. During wet weather the treatment plant capacity is insufficient to treat the combined flow and the excess flow (called combined sewer overflow or CSO) is discharged untreated to receiving waters at designed overflow points. There are approximately 746 communities with CSS serving 40 million people in 32 states in the U.S. at present. [267] Most of these sewer systems were built in the 19th and early 20th centuries. Many of the CSS are located in the northeastern U.S. and around the Great ; they include the District of Columbia, Illinois, Indiana, Maine, , New York, Ohio, Pennsylvania, and West Virginia. However, states such as Oregon and Washington also use CSS. An EPA report to congress, released in 2000, estimates that CSOs released annually into U.S. receiving waters may be about 850 billion gallons. Polluted water discharged by CSOs into the receiving waters has been reported to be one of the major sources of environmental pollution and disease for human, fish, and wildlife. [267] While CSS are considered more cost effective in terms of providing wastewater collection and storm , the resulting untreated CSOs are environmentally unacceptable. The cost to provide treatment of CSOs is extremely expensive, and outweighs the cost of implementing a separated sanitary and storm sewer system. Treatment measures for excess flows in CSS systems include additional storage at strategic points in the system, through tanks or in deep tunnels, until there is sufficient capacity at the WWTP to treat the combined sewage, satellite treatment systems at CSO locations, and reduction of stormwater runoff into the combined sewer system. 1.5.2 Performance and Cost Issues in Sanitary Sewer Systems (SSS) A SSS is designed to collect and convey only sanitary wastewater from residential, industrial and commercial centers to the treatment plant, while the stormwater is carried by a separate pipe system that is not connected to the sanitary wastewater system. One of the first SSS in the U.S. was constructed in Memphis, Tennessee following the yellow fever outbreak of 1873. SSS have become more widely accepted in new and developing cities because they are capable of reducing raw sewage overflows and providing a safer, higher quality discharge to surface waters than CSS, even though construction of an additional storm drainage system increases capital cost. However, SSS experience overflows as well. These overflows are termed Sanitary Sewer Overflows (SSOs) and are a result of structural and mechanical failures. Capacity exceedance occurs as a result of groundwater and stormwater infiltration and inflows (I&I) as well as blockages caused by the accumulation of solids and/or debris in the sewer conveyance system. When the capacity of the sanitary sewer is exceeded, the resulting overflow is discharged through manholes and flows onto public and private property. This overflow of sanitary sewage and wastewater can find its way to receiving waters or it can stay stagnant on the land. A U.S. EPA report[247][267] estimated SSOs incidences around the U.S. to be between 23,000 and 75,000 per year, which results in a discharge of between three and ten billion gallons of untreated sewage each year. Both CSOs and SSOs discharge raw sewage that carries pathogens, solids, debris, and toxic pollutants that can be transported to receiving waters by runoff. In addition to SSOs, sewage can also be discharged into the groundwater through pipe fractures and leaks due to pipe deterioration and age. If the groundwater in a particular area is

A Review of Advanced Sewer System Designs and Technologies 1-5 used for human consumption, contamination from sewer leaks can result in serious public health problems. The discharge of raw sewage into the ground can originate from both CSS and SSS pipe leakages. As sewer infrastructure ages and deteriorates, high volume leaks can be experienced at pipe fractures, corroded pipe, and at deteriorated pipe joints and manholes. Cost issues associated with SSS come mainly from maintenance of the system. Maintenance costs average approximately 2% of the system construction cost per year (for a design life of 50 years). Unfortunately, few U.S. cities have made the investment to provide system maintenance over the years since these systems were constructed and they now find themselves facing extremely high repair costs. The most common approach to controlling SSOs is a combination of rehabilitation of deteriorating pipes to reduce I&I, adding relief sewers to conduct excess flows to a convenient location, and storage of excess flows at satellite locations until there is capacity at the WWTP. These plans are considered “immediate action” plans, which will significantly reduce the frequency of the most serious SSOs. The long term plan is rehabilitation of the SSS with an annual budget of 3-4% of the estimated total cost of system replacement (resulting in total system rehabilitation in 25-35 years). 1.6 Performance and Cost Issues in Alternative Wastewater Collection Systems As mentioned previously, alternative wastewater collection systems include vacuum, pressure, and small diameter gravity (effluent) sewers. These sewer collection systems include electrical and mechanical components plus other appurtenances that require constant inspection and maintenance. Failure of the grinder pump, septic tank effluent pump, or vacuum pump at a household will result in disruption of sewer service until the problem is fixed. There may be odor problems from septic tanks, grinder pumps and solids handling pump basins. When the raw sewage is retained in the basin it becomes septic and produces hydrogen sulfide gas, which is odorous, hazardous to human health, and corrosive. Odor problems can be more serious in systems installed in warmer climates compared to cold climates. High temperatures accelerate anaerobic microbiological activities in the basin while cold temperature slows the activities down. Methane gas is also produced in the basins. This gas is flammable so caution should be taken when the basin is opened for maintenance or inspection to avoid a fire incident. Grease accumulation in the basin can affect the functionality of the float switches and pumps and hence cause malfunction of the sewer system. Since alternative sewer collection systems are buried shallower than conventional systems, freezing can become a problem in very cold climates. Alternative wastewater collection systems use electrical and mechanical parts that require constant inspection and maintenance. These electrical and mechanical components carry a significant initial investment cost. In addition, running the mechanical parts consumes electricity. If we consider the pressure sewer system, the average unit cost for a grinder pump and appurtenances ranges from $3000 to more than $5000. The installation cost ranges between $500 and $2000. The septic tank effluent pump (STEP) package costs between $4000 and $7000. The price is lower if the pump is a low-head pump and higher if the pump is a high-head pump. Monthly O&M charges for pressure sewer systems are between $35 and $100 per month per household. On average, the total capital cost incurred by new customers for the equipment and installation of the vacuum sewer is between $5000 and $8000. [268] For the vacuum sewer system, the utility will need to develop the sewer system and charge a service connection fee. The cost for a new service connection is between $1200 and $5300, which includes a vacuum valve, valve pit/sump, fittings, pipe, and labor charges. A vacuum station for 50-1000 connections will cost $250,000-650,000. [268]

1-6 For small diameter gravity sewers, existing customers are usually provided the interceptor tank and service lateral with no additional charge at the time of construction. The interceptor tank, ranging in size from 1000 to 1200 gallons, is installed for each home. However future customers must pay for the septic tank and lateral in additional to a hookup fee. The septic tank costs between $1000 and $3000, the connection lateral is about $10-20 per foot of pipe. The user charge for small diameter sewer is between $20 and $40 per month per house connection. The average capital cost per house connection for new customers is between $7000 and $7900. [268] 1.7 Comparison between Gravity and Alternative Wastewater Collection Systems Conventional gravity sewer systems are a more cost-effective and energy efficient method of collecting and conveying sewer water in large, densely populated areas compared to alternative wastewater collection systems.[209] However, many small towns have clustered housing located far from the more densely populated areas. These clustered homes may be located far away from a conventional municipal sewer collection system. Homes may also be located in low lying areas near a waterbody, such as a lake, areas with a high water table, areas with rocky ground, hilly terrain, or poor soil conditions. Conventional gravity sewers are not available in these areas or it may not be cost effective to connect such houses to a conventional gravity sewer system. Alternative sewer systems can be considered as a technically and economically viable solution to fulfill the health and environmental goals of these types of communities. Alternative sewer systems use plastic pipes with much smaller diameter compared to conventional gravity sewer systems. These small plastic pipes are less expensive and easy to install compared to the conventional gravity pipes. Alternative sewer system can be buried at shallow depths, just below the frost line and installation can be done using trenchless technology. Conventional sewers are buried deeper and require more open-cut excavation, which is more expensive and environmentally unfriendly. Design and construction techniques for alternative sewer technologies minimize I&I problems, so additional flow into the sewer system is limited. For less populated areas located away from the conventional sewer system lines, and in difficult terrain, alternative wastewater collection systems can lower the construction cost and minimize I&I problems. The question remains however, when considering the lifetime cost of the two systems whether an alternative system is cheaper for small developments than a conventional system with a small capacity WWTP. Under normal circumstances a conventional gravity sewer will be favored because the alternative sewer collection system design requires several additional components which are not required in conventional gravity sewer systems, including septic tanks, elevation pumps, vacuum pumps, valves and other components. Additional costs associated with these parts may create a tradeoff with the excavation cost in conventional sewer system installation. Alternative sewer systems usually require electrical power to operate, resulting in additional energy costs compared to a conventional gravity sewer system, which, if well designed, can operate entirely by gravity flow. Another disadvantage of alternative sewer systems is that sewer service disruption can occur due to power outages or mechanical breakdown of a component. These types of problems may not exist in conventional gravity sewer system designs. [216] 1.8 Summary Despite the advantages and disadvantages of each sewer collection system design briefly discussed in this chapter, the design engineer will need to consider cost and benefit analysis together with other factors that may affect or promote a particular choice for a sewer collection

A Review of Advanced Sewer System Designs and Technologies 1-7 system design. These other factors may include social, cultural and environmental factors, and the acceptability of a particular design to a particular community. The assessment will need to be conducted during the planning and design phase of a project and decision will need to be made on a case by case basis. The rest of this document will explore different sewer collection system designs and technologies that are in use at different locations in the U.S. and around the world. Focus will be given on how a particular design or technology works, its cost, performance, advantages, disadvantages, location where a design or technology is in use and who is behind a design or manufacturing of a particular component of sewer collection system.

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CHAPTER 2.0

SUMMARY OF ADVANCED SEWER SYSTEM DESIGN AND TECHNOLOGIES

2.1 Sewer Conveyance System Design and Technologies Literature Selection and Classification Criteria Literature on advanced sewer system design and technologies was collected from a plethora of sources, the principal sources of which were the United State Environmental Protection Agency (U.S. EPA), Water and Environmental Research Foundation (WERF), Elsevier, America Society of Civil Engineers (ASCE), Australia Water Association, Hunter Water Corporation of Australia, and National Small Flows Clearinghouse. The information gathered from the literature review is summarized in Table 2-1 below. The literature is grouped under the following subject headings:  Onsite Technologies  Pressure and Vacuum Sewer Technologies  Small Diameter Gravity Sewers  Gravity Sewer System Design  Techniques for Infiltration Detection and Control  Sewer Construction/Rehabilitation Technologies to Control I&I and SSO  Pipe Material and Joints for Sewer Systems Designs

Within each of these subject areas the information is further categorized as Established Technologies and Innovative/New Technologies. Innovative/New Technologies are further subdivided into Proven Technologies, and Experimental & Foreign Technologies. The Established Designs and Technologies subgroup identifies sewer design and technologies that are fully adopted in the United States and are commonly used by many municipalities and sewer utilities. Selection of a design or technology to be listed in the table was based on whether the particular innovation has been introduced into the existing sewer systems for the purpose of improving performance, or reducing the cost of sewer operations. Literature was collected from a variety of publication years. The Proven Designs and Technologies subgroup comprises sewer design and technologies that have been introduced into the sewer industry but have only been adopted on a limited scale in the U.S. These technologies have been proven to work in some areas around the U.S, but their application in other areas around the country is not widespread. Most of the literature used for proven technologies was published between the years 1999 and 2010. The Experimental and Foreign Technologies subgroup summarizes sewer designs and technologies that are either at the experimental stage in the U.S. or outside U.S, and/or are

A Review of Advanced Sewer System Designs and Technologies 2-1 proven to work in other countries but have not been used much in the U.S. More focus was given to technologies and designs used in Australia, Germany, UK and . Most of the literature used for this group was published between 2000 and 2010. A number of these designs and technologies identified in Table 2-1 were selected, based on their potential for application in the near future, for detailed discussed in Chapters 3.0 through 8.0. These chapters are organized in the same fashion as Table 2-1. NOTE: In order to make Chapters 3.0 through 8.0 more readable, most of the references from which the discussion is developed have been omitted; but the reader can easily find the references by looking back at the appropriate section of Table 2-1.

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Table 2-1. Advanced Sewerage System Design and Technology Summary Table.

Onsite Technologies – Chapter 3.0 Innovative/New Technologies Established Technologies Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Conventional water efficiency toilets: Advanced waterProven efficiency Technologies toilets: ExperimentalExperimental Advanced & Foreign water efficiency Technologies toilets: Convecti onalPortable Gravity toil Septicets[219] system: Advanced The Septic Vacuum/ System Designs System and [218]  Low diluting toilets[218]  ModifiedSingle and Gravity Multiple Flow chambers. Toilets[13][1, 2, Components Compositing: toilets [3, 219, 260]  Heating and Drying toilets[218]  Pressure7, 9, 10, 11, 12, Assisted 14, 19, 21, 31,Toilets 32, 35][13]  IncineratingEnviro-Septic toilets System [15, 219](Canada) [26]  Automatic Vacuum flushing[43, 44, 45] [1, 2, 5, 6, 24, 28, 34] Water Efficient Toilet Designs Alternative Ultra Drainfield Low-flow designs Toilets [219]  OilSeptic re-circulating Tank Filters toile [36]ts [20] Water efficient toilets (Australia) [39]  Low Pressure Pipe (LPP) System  Use of Control Panels in Septic  Dual flushing toilets[39] (Application of Siphons and Systems[29]  Urine separator[39] Onsite Sewer System designs Pumps) [12, 18]  Septic Tank Polishing[30]  Air assisted flush toilets[39] and technologies  Serial Distribution systems [12]  Septic Tank Leaching Chamber[33]  Waterless Urinals and Ultra-low flush  Shallow Trenches [27] Urinal Systems [38]  Mound Systems [12, 17]  Construction wetlands, Lagoon System [5, 37, 220]  Sand Filters [16, 23] Advanced Source and Nutrient control toilets: Oil Separator for vehicle repair shops (Australia) [160]  Evapotranspiration system [8]  Gray and Black water separation  Oil water Separator[160]  Disinfection System [4, 22] technologies [40, 41]  Car wash Bay[160]  Septage Treatment[25]  Graywater for toilet flushing [40, 41] Food Wastewater Pre-Treatment - Source/Nutrient Control Sewer Guidance Manual for Separation of Graywater from  Urine Sorting System [42] Facilities(Australia) [158, 159] Designs Blackwater[264]  Sloping Bottom Grease Arrestor[158, 159]

 Flat Bottom Grease [158, 159] Using Household Graywater for Landscape  Air Flotation Separator[158, 159] Graywater Separation Irrigation[265, 266]  Silt Trap[158, 159]  Straining Pit[158, 159] 

A Review of Advanced Sewer System Designs and Technologies 2-3 Alternative Wastewater Collection System Design and Technology – Chapter 4.0[287] Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies System Designs and Components: Advanced System Designs and Components: Inspection Technologies for Pressure Sewer Pipe  Use of Septic tank effluent pump  Use of Gasketed PVC Pressure pipe[162, Conditions: (STEP) [209, 211, 216] 215]  SAHARA (UK Technology) [203]  Uses Low horsepower sump  Use of Submersible Semi-Positive  Magnetic Flux Leakage[203] pump [208] Displacement Grinder Pump[227]  Advanced Engineering Service[203]  Use of Centrifugal Grinder  Submersible Centrifugal Grinder  Eddy Current Probe[203] Pump[209, 210, 213, 216, 226] Pump[228]  Hydroscope[203] Pressure Sewer System  Use of Cleanout instead of  Low Pressure Sewer System[229] [203] Design [65, 208, 209, 212, 213]  Broadband Electromagnetic manholes [212]  Advanced Submersible Grinder [203]  TESTAU (Australia Technology)  Uses of sensors to monitor the Pump[230] operation of effluent pump [208]  Submersible Sewage Grinder Pump[231] Pressure Sewer Installation Using Directional Drilling  Use of PVC pipe with Solvent-  Submersible Grinder Pump[232] (Australia) [214] weld-type fittings[209] Components of grinder pump system: [211, 216]  (Control panel, buried electrical cable, shut off valve, lever sensor, check valve, grinder pump, and wet well). [211, 216] Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies System Design and Components: Advanced System Designs and Components: Use of Horizontal Directional Drilling (HDD) for  AIRVAC Valve Pit package, main  Use of Gauge taps (essential for sewer pipe Installation[233] components (Valve pit, Vacuum vacuum sewer system Advanced Experimental System Components: interface valve, Suction and troubleshooting)[215]  Use of Fiberglass Valve pit[233] Sensor pipes) [209, 215, 216, 233]  Use of Electronic Air Admission Control  Use of Pig-Tail connection for generator Vacuum Sewer System Design [233] [233] [156, 209, 217, 233, 236, 241]  Division valves (Plug valve, and (EAAC) valve hookup at the vacuum station wedge gate valves)[209, 215, 233]  Use of Integral Valve Pit[233]  Use of Fiber-optical SCADA System[233]

 Use of Solvent welded PVC  Use of Gate valves as division Sound control at the Vacuum station pipes[215] valves[233]  Use of Soundproofing features installation  Use of Reformer Pocket design  Use of O-ring rubber gasketed pipes[233] at the vacuum station[233] concept[241]  Use of Saw-tooth profile design  Use of Buffer tanks for large concept[215,233, 241]

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customers[233]  Use of dual Buffer Tanks for large  Use of External Breather[209] customers[233]  Use of Bio-mass for  Use of In-Sump Breather[233] Odor control[233]  Installation of Cycle Counter[233]  Use of Auxiliary Vent[209]  Use of Cleanouts[209] Use of pipe identification methods during construction:  Magnetic trace tape[215]  Metal toning wire[215]  Utility frequency based electronic markers[215]  Color cording of the pipe[215] Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Vacuum station components: Odor Control at Vacuum Station  Collection Tank[233]  Use of Chemical neutralization[233]  Vacuum Pump (Liquid ring or  Use of Activated Carbon Absorption Sliding vane type)[233] system[233]  Sewage Pump (Dry pit pumps – Use of Manufactured Bio-mass filters[233] Non clog type)[233]  Check valves[233] Continued:  Electricity stand by Generator[209, Vacuum Sewer System Design 233] [156, 209, 217, 233, 236, 241]  Vacuum Switches[233]  Vacuum system control panel (SCADA) and [233]  Vacuum Gauges[233]  Motor Control Center[209]  Use of Level Controls[209] Use of Vacuum Gauges and Sump Valve[209]

A Review of Advanced Sewer System Designs and Technologies 2-5

Alternative Wastewater Collection System Design and Technology Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies System Design and Components: Advanced System Design and Components: Use of Small Bore Sewer (Canada experience) [225]  Uses Septic tank to provide  Use of Septic Tank Effluent Pumps pretreatment of sewer water[209, (STEP) for below grade Service 216, 222] areas[209, 221]  Use of Surcharging process  Application of lift pumps[221] (hump) to limit excavation [216]  Use of air release/vacuum and check  Uses HDPE pipes joined by heat valves[209] fusion[225]  Use of Carbon filters for Odor control[209] Small Diameter Gravity Sewer  Provision of Ventilation system  Use of Drop inlets for Odor control[209] System Design [209, 216, 222, 224] through service connection house  Use of On-Lot Balancing tank system vent stacks[222] for hydrogen sulfide stripping  Treatment of Effluent is done by  Use of Soil beds for odor control[209] Lagoons, Stabilization ponds or  Use of Fiber reinforced plastic (FRP) or by Sub surface Infiltration[235] High Density Polyethylene (HDPE)  Use of Precast reinforced Tank.[209] concrete and Coated steel tanks as Septic tanks[209]  Uses Cleanouts instead of Manholes [209] Innovative Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Advanced System Design and Components: Hybrid Sewer System Design  Combining small diameter gravity sewer with conventional gravity sewer[234] Combining pressure sewer with conventional gravity sewer [65]

2-6

Gravity Sewer System Design – Chapter 5.0 Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Conventional System Designs and Advanced System Design and Components: Experimental Advanced System Components: Components: Optimizing sewer system design:  Hydrodynamic Vortex Separator [83, 94]  Sewer Collection System  Use of Generic Algorithm (GA) and,[108, Designed to convey both 131] Advanced Foreign Technologies: sewerage and stormwater.[237, 238]  Use of Quadratic Programming (QP)  High Speed Fiber Filter ( Solids and Floatable Controls: [108, 131] experience) [114]  Use of Baffles[243]  Use of Scattergraph [67]  Use of tank (Spain Lab  Use of Trash Racks[201, 243] Wet-weather Flow Control: experiment) [115]  Use of Static Screens[243]  Sewer Separation Technologies  Invert Sediment Trap (CSO) sediment  Use of Catch Basin (Separate stormwater from sewer water removal technique. (UK, , Scotland Modifications[243] in Combined Sewer Systems) [57, 60, 74, 96, )-European experience.  Use of End-of-Pipe Nets[243, 247] 125, 242, 244, 247]  Sewer Flushing [60, 172] Advanced Sewer system operation control Other Experimental Technologies:   Netting Systems for floatable  SCADA Technology [93, 103, 113, 248] CSO Satellite Treatment technologies [48, 51] (Automatic physical process with remote Combined Sewer System controls  Real Time Flow Control (RTF) [66, 79, 82, 91, 103, 113, 135, 136, 139, monitoring) [86, 113, 245] (CSS) Design. Floatable Removal Techniques: Technologies 247, 248] [168]  Booms[243]  In Sewer Sediment Trap  Skimmer Boats[243]  Use of Neural – optimal Control  Use of Weather Radar for CSO [88] Odor Control Techniques: Algorithm [169] monitoring and control  Use of Wet Scrubbers[57]  Use of Inflatable dams control Logic for  Use of Street Surface Storage[87, 132]  Use of Active Carbon Adsorption RTC [126]  Use of Micro or Macro BMP retrofits Unit[57]  Use of Nine Minimum Controls [59, 60, 111] (Kansas City example) [127] Flow, Sediment and Solids control:  Application of advanced vortex and  Satellite Sewer System Modeling [142]  Use of Helical Bend Regulator [172] other solids removal techniques [83, 94,  Use Storage in Seawater [166]  Use of Impregnated Concrete 199]  Use of Decentralized Wireless Sensor pipe [172]  Bottom slot outlet [95] Network [89]  Polymer injection into sewage [60,  CSS operation optimization techniques  Use of Virtual Gauge [93] 172] [103, 108, 170]  Use of Embedded Sensor Network Inflow and Sediments control: CSO Tank technologies:[199] Technology [98]  Use of Hydrobrake [149, 172]  Fluidsep-German Design, Grit King  Use of Optimal Control system  Use of Fluidic Regulator [172] Design, and Storm King (from H.I.L  Feed-Forward Back-Propagation Artificial [57]  Swirl/Vortex Technologies (EPA Technologies) Neural Network [58] Swirl Separator, EPA Swirl  End of weir stilling pond Digritter) [57, 60, 72, 92, 173, 199, 207, 247]  High side weir chamber [149] Other Foreign Advanced Technologies:

A Review of Advanced Sewer System Designs and Technologies 2-7 Wet Weather Flow Control: [54, 78, 106]  US Swirl regulator [72]  First Flush pipe-type-in-line CSO-tank  Retention Basins [54, 78, 106]  Hydrodynamic Separation [149] (German Model) [104]  Use of Inflatable Dam[57] Other Advanced CSO control Techniques:  Use of Wirbeldrossel and  System Based Approach [70]  SPIRIT 21 – Japanese Technologies Wirbelvalves [57]  Watershed management [109, 246] (debris removal, high rate , Other Wet Weather for CSO Control: [50, 57,  Solids Separation Techniques in a CSO coagulation/separation, and 113, 242, 247] Chamber [84, 94] measurement/control disinfection) [105]  Maximization of In-System Computer Modeling for sewer Hydraulics:  In-line-Circular CSO tank (German Model) control/In Line Storage [57, 247]  (XP-SWMM, TRANSPORT) [59, 74, 81, 85, [104]  Removal of obstructions, 93]  Off line Rectangular CSO-tank (German  Maintenance and repair of tide  Combining WinSLAMM & SWMM Model) [104] and control gates, Models[59]  Installation and adjustments of  Use of LIFETM Dynamic Simulation  Use of Integrated Catchment Simulation regulators, Model (ICS) Model – example.  Reduction and retardation of in-  STORM, EXTRAN Models[59]  Self regulating movable weir for water flows, upgrade/adjustment of pumps GPS and GIS Technologies: level control (German Model) [104] and rising of existing weirs and  Application of GPS and Remote sensing  Horizontal fine screen for removing of installation of new weirs). [50, 57, 113] Technologies in CSO control[122] gross solids at CSO tanks (German  Near Surface Off-Line  Application of GIS Technologies[116, 122] Model) [104] Storage/Sedimentation[57, 69, 71, 242, Other Advanced CSO Control Techniques:  Rotating Dram Sieve at the CSO tank 247]  Use of Cross Flow Microfiltration[57] (German Model) [104]  Deep Tunnel Storage [57, 60, 61, 128,  Sediment, Corrosion, and Pollution  Near Bed Solids (NBS) Modeling in CSS – 247] Control [143, 171] Europe example [133]  Course Screening [55, 57, 68, 92, 201]  Use of CAD in Sewer system  Use of Vertical Dropshaft[57] designs[251]  Pre-fabricated polyethylene Vortex  Use of Sluice Gates[60]  Maximizing WWTP Treatment Capacity Separator (German Model) [104]

 On-Site Storage[247] (Unit expansion and retrofitting). [86, 113, CSO Treatments Techniques: 144, 242, 247]  Frontal Weir with Varying Crest – France [110]  Chlorine disinfection[47,57, 60]  Capacity Management Operations and example (Chlorine gas, Sodium Maintenance (CMOM) [141, 144]  CSO control by using stormwater reservoir hypochlorite, and Calcium  Use of High Gradient Magnetic (Japan example) hypochlorite) Separator (HGMS)  Use of Movable weir at CSO-tank (Japan  Alternative Disinfection [46, 60, 92,  Use of Powdered activated carbon-alum Example) 247] (chlorine dioxide, ozonation, coagulation unit (static mixing/reaction  Ring Shaped Floating Plastic Net media. ultraviolet radiation, peracetic pipeline) (Tokyo – Japan) [167] acid, and electron beam  Chemically enhanced high rate  Metering a CSS [134] irradiation). sedimentation [92, 128]  Use of Cross Flow Ceramic Membrane  Dissolved Air Flotation [92, 199, 207]  Continuous deflective screens Microfiltration [101, 151]  Fine Screens and Microstrainers  Fuzzy Filters [92]  Transient Control in CSS [121] [55, 69, 201, 207, 247]  Ultraviolent Irradiation [92]  Detention Basin for CSO control (South

2-8

 Dual Media high-rate filtration  High Rate Disinfection [120] Korea) [165]  Biological Treatment [107]  Combined Sewer Overflow (CSO)  Japan Fine CSO Screen[102] Pollution Prevention techniques Chamber/Tank modification. [112, 149] Use of Embedded Sensor Network[148]  Waste reduction and recycling[53, 243]  CSO Control using Storage in seawater  Street cleaning[53, 60, 243] (Flow Balance Method-FBM Facility)[166]  Catch basin maintenances[53, 60]  CSO Control using LID System[174]  and control[53] CSO Control through Decentralized Urban  Erosion and sediment control Sormwater Control [200] techniques[53, 60]  Public Education[243]  Product Ban/Substitution[243]  Control of Product use[243]  Control Illegal Dumping[243]  Bulk Refusal Disposal[243]  Hazardous Waste Collection[243]  Water Conservation[243]  Commercial/Industrial Pollution prevention[243] Other CSO Control Techniques:  Operation and Maintenance Techniques [52]  End of Pipe Storage[57]  Use of Fluidic Regulator [172] Dry Weather CSO Controls:[243]  Collection System Inspections[243]  Repair and Rehabilitation of Regulators[243, 247]  Maintenances of Tide Gates[243]  Interceptor Cleaning[243] Adjustment of Regulator settings[243]

A Review of Advanced Sewer System Designs and Technologies 2-9 Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Conventional System Designs and Advanced System Designs and Technologies Advanced Experimental Technologies. Technology.  Sewer Collection system Computer Modeling for sewer hydraulics capacity Use of Fixed Media Bioreactor (Biofilters): designed to convey only assessment  Sand[164] sewerage.[237, 238]  XP-SWMM, [81, 85, 146]  Felt (Textile)[164]  TRANSPORT, [81, 85, 146]  Peat[164]  MACRO model [81, 85, 146]  Felt/Sand or Peat/Sand[164] Sanitary Sewer Overflow (SSO) Control Sanitary Sewer overflow (SSO) control Techniques: technologies: Other advanced experimental technologies:  Floatable control technology  Storage/Surge/ Equalization facility [146,  Virtual Dynamic Computer Model (VDCM) (Baffles, Screens and trash racks, 157] [93] catchment basin modification,  Use of interceptor flow carrying  Use of Neural Networks [80] netting, containment booms, and capacity[247]  Use of Computerized Maintenance [48, 68, 199, 247] Separate Sanitary Sewer skimmer vessels). Management System (CMMS) [123, 239] (SSS) System Design.  Sanitary Sewer Sediment Root control: Detecting SSO by combining Pipe flushing. [75, 247]  Chemical Cleaning to reduce root hydraulics, Real time monitoring, and  Elimination of Hydraulic inestation [157] Neural Network [80] bottlenecks[239] SSO detection techniques Sewer flow monitoring techniques:  Visual inspection[247, 250]  Use of WSI NEXrad [93]  Smoke testing[247, 250]  Use of SCADA Technologies [157, 239, 256]  Aerial Monitoring[250]  Mapping, [93, 122, 155, 239]  Manhole inspection [123, 250]  GPS and[93, 122, 155, 239]  Building inspection[247, 250]  GIS techniques[93, 122, 155, 239, 250]  Soil moisture and temperature  Use of Data Bases [93] monitoring[250]  Use of Internet and Intranet [93]  Surface settling monitoring[250]  Spot repair techniques[162, 239]

2-10

SSO control at the Sewer :  Hydrogen Sulfide Control in Sanitary  Provide Additional Storage[157] Sewer Systems [190]  Installing Additional Pumps[157]  Application of Nitrate [190]  Upgrading the Pumps[157]  Use of Microbial Fuel Cell (MFC) [190]  Provide additional Power supply[157]  Use of Novel Inhibitors such as Slow  Upgrade Alarm systems[157] released solid phase Oxygen  Bypass facility for pumping stations[157] (MgO2/CaO2) and Formaldehyde [190] SSO control in the Collection systems: FOG removal/interceptor techniques  Collection system Capacity  Use of Chemicals[247] Management, Operation, and  Use of Mechanical techniques[247] Maintenance (CMOM) approach. [141, 147,  Use of Bioremediation[239] 239]  Use of De-greasers[239]  Amplifying Sewer Trunk [157]  Use of Enzyme additives[247]  Removal of blockage by rodding [157]  Grease Interceptor[247]  Eliminating Cross Connections[157]  Automatic [247]  Public Outreach on Fats, Oils, and  Passive Grease Traps[247] Grease (FOG) Control[247] Odor Control Technologies (Gas Phase) [62, 204]  Host of pipe joints  Chemical Scrubbers [204] Odor control Technologies (Liquid phase) [62, 204]  Activated Carbon Adsorbers[204]  Aeration and Oxygeneration: [183]  Biofilters [204] . (Air injection, Venturi Aspirators,  Biological Scrubbers [204] Air Lift Pumps, U-tube Aeration,  Ionization Systems [204] Pressure Tank Air Injection,  Hydroxyl Ion Fog [204] Hydraulic Fall Injection, Downflow  Cold Plasma and Photocatalystic Reactors Bobble Contractors, and Oxygen [204] [183] injection) Collection system Ventilation Models  Chemical Oxidation (Chlorine gas,  Empirical Model [197] , Sodium Chlorite,  Fluid Dynamic Model [197] Permanganate, Magnesium Hydroxide,  Thermodynamic Model [197] and Hydrogen Peroxide) [180, 204]

 Sulfur Precipitation (Using Iron Coagulated in Sewers, and Potassium Ferrate). [204]  pH Adjustment (pH Stabilization, Caustic Shock Loading, Biological treatment, Bioaugumentation, and Enzymatic treatment.[204]

A Review of Advanced Sewer System Designs and Technologies 2-11 Techniques for Infiltration Detection and Control – Chapter 6.0 Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Conventional Techniques: Advanced Techniques: Experimental Techniques:

Infiltration control: Advanced Infiltration control: Infiltration control  Rehabilitation Techniques (Fixing  Use of Basin Characterization to control  Robotic inspection and rehabilitation of defective pipe joints, cracked and I&I [90, 137] sewer lines [179, 188, 192] broken pipes, seal the manholes  Grouting (fill cracks and joints defects)  Non Circular Pipe Lining [182, 185, 186] cracks). [76, 85, 86, 123, 145] [157]  Preventive Installation techniques[205]  Cement motor coating[76, 85, 86, 123,  Corrosion control techniques i.e.,  Fiberglass rehabilitation of manholes [162, 145] Cathodic protection technique)[205] 177] Infiltration Reduction control:  Polymer Slurry injection[205]  Glass reinforced plastic (GRP) Insert [162]  Rainfall-derived inflow and  Epoxy Grout/Patching [162]  Fiber glass reinforced cement (FRC) lining infiltration (RDII) flow rate control.  Mechanical joint seals [162] [179] [49, 64, 77, 86, 97, 99, 202, 206, 247, 255]  Regional I&I control[250]  Polyester resin concrete (PRC) lining[263] Infiltration detection techniques:  Use of flexible liners[205]  Insituform Technology[263]  Dye Test for leakage detection  Fold and Formed Pipe (FFP) or Closely  Precast Gunite[263] [198, 249] Fitted Liner[263]  Chemical grouting[263] [247] Infiltration Control  Air Testing  Private sewer lateral repair and Leakage detection technique: [181] [99, 247] Technologies [49, 64, 97, 99, 100, 198,  Smoke Testing rehabilitation [157, 198]  Focused Electrode Leak Location System 202, 249]  Hydrostatic Testing[247]  Sewer main repair and rehabilitation [157] (FELL – 41) – Europe technology [181]  Visio Inspection[247] Root Removal Techniques (Australia) [161] Locating leaks and Infiltration is Sanitary sewer New technologies in sewer inspection: [175, 203] Root Removal Techniques [157, 198, 249] system techniques:  KARO and MACRO (German Innovation),  Mechanical Methods [198]  Closed Circuit Television (CCTV) [99, 157, based on 3D optical sensor, ultrasonic . Rodding[198] 175, 203, 250, 256] sensor, and microwave sensor. [175, 176, 179, . Hydraulic Cleaning (jetting)  Ground Penetrating radar [163, 162, 175, 203] 203] [198, 247]  Radar Tomography (RT) [203]  PIRAT (CSIRO-Australia), based on new [198]  Chemical Methods  Infrared Thermography [163, 175, 203] qualitative multi sensor technology. [175, 176, [198] . Acid and Solvents  Air Pressure Test[247] 179] [198] . Copper Sulfate  Water Test  SSET – Sewer Scanner and Evaluation . Dicholbenil[198]  Manual Surveys Technology (developed by TOA Grout, . Metam Sodium / dichlobenil[198]  Digital Camera inspection[162] CORE, and TGS – Japan Tech) this . Diquat dibromide[198] [162, 203, robotic system contain CCTV, video . Herbicides[247]  Laser Profiling/3D Scan/Sonar 247] record, full circumference scanner and gyroscope technology. [175, 176, 203, 250]  Use of Bio-Filters and Barriers[239]  Totally Integrated Sonar & CCTV Integrated Technique (TISCIT)[162]

2-12

 Wireless monitoring System[162] New Technologies for Gravity Sewer Inspection :  Tree Species Selection[239]  Smart Sewer Assessment Systems[162]  Radiax Vector Orphée (French) [203]  Acoustic technologies [163]  Triscan (German) [203]  Electrical and Electromagnetic methods  ClearLine (New Zealand) [203] [163]  CoolVision (Canada) [203]  Laser profiling [163]  ISAAC (European Union) [203]  Ultrasonic testing system [163, 203]  Panoramo (German) [203]  Micro Deflection [163, 203]  Sonar Profiler (UK) [203]  Gamma-Gamma Logging [163, 203]  Focus Electrode Leak Locator[203]  Impact Echo/Spectral Analysis of  Coolvision Laser Inspection by surface waves (SASW) [163, 203] Colmatec[203]  Sonic Distance Measurement [175]  Digital Scanning and Evaluation  Rotating Sonic Caliper [179] Technology (DSET) [203]  Wave Impedance Probe[203]

Amtec’s Sonar Inspection[203]

Sewer Leakage detection technique:  Using Quantification of Exifiltration from Sewers by Artificial Tracers with Continuous Dosing (QUEST – C Tracer Method) [178, 187] Application of Aerial Infrared Thermography[257] Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Inflow Reduction Techniques [149] Inflow Source Investigation Techniques [150, 157, 198]  Seal the manhole covers/manhole  Flow monitoring[150, 157,198] rehabilitation [123, 150, 157, 247]  Nighttime flow isolation[150, 157,198]  Roof drain reduction [150, 198, 249]  Smoke Testing[150, 157,198]  reduction  Manhole visual inspection[150, 157,198] Inflow reduction Technologies [150, 162, 198]  Pipeline inspection[150, 157,198] [149, 198, 202]  Disconnect Footing Drains[198, 239,  Door to door basement inspection[150, 249] 157,198]  Stormwater infiltration pumps [162]  Operation and Maintenance record. [150,  Interconnection removal/Cross 157,198] connection elimination [150, 157, 239, 247, 256] Cleanout Cap Replacement[198

A Review of Advanced Sewer System Designs and Technologies 2-13 Sewer Lateral Locating and Inspection Sewer Lateral Locating and Inspection Sewer Lateral Locating and Inspection Technologies[198] Technologies[198] Technologies[198]  Walkover Sonde[198]  Lateral CCTV Inspection[198]  Ground Penetrating Radar (GPR) [198]  Rod Probing from surface[198]  Vacuum Excavation[198]  Radar Tomography (RT) [198] Technologies for Private Sewer  House to House inspection[198]  Pressure Testing[198]  Electro Scanning[198] Laterals [198, 239]  Smoke Testing and Dye Water Testing[198, 247, 250] Sewer Lateral Marking Technologies [198]  Plumber’s Snake[198]  Magnetic Tapes[198]  Sewer Balls[198] Conventional Sediment cleaning Sewer Sediment Flushing Systems: Techniques:  Hydrass[240] Design technique:  Hydroself[240]  Provision on self-cleansing  Biogest Vacuum Flushing System[240] gradient[252, 253]  Small Diameter Pipe Flushing using a  Provision of self-cleansing Dosing Siphon[240] velocity (velocity > 3.3ft/s or 1m/s)[252, 253] Hydraulic Modeling Simulation of Flushing  Provision of adequate pipe Technologies capacity[252, 253]  SWMM [240]  Provision of Proper Junction  EXTRAN[240] angle[254] Mechanical cleaning  Power Rodding[240, 256]  Pigging[240] Sediment and Solids Control in  Power Bucket[240] Sewer Systems[240]  Silt Trap[240] Hydraulic cleaning  Jetting[240, 247]  Balling[240, 247]  Kites [247]  Scooters [247]  Flushing[247]

2-14

Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Tree Planting and Green ways[247] LID, and BMPs [117, 119]  Urban water retrofit (Decentralized  Retention Basins [122] controls) [200] Water Conservation technologies:  Detention Basins [122]  Water Recycling[247]  Green Roofs [118, 129, 130, 247] Experimental LID  Waterless Technologies[247] [247]  Infiltration Basins[259] Green Infrastructure  Green filters [247] [259] Technologies to control CSO   Rain Gardens  Infiltration Trenches  Water efficiency fixtures and (Kansas City)[119, 128] appliances[247]  cell [130, 247, 259]  Pervious Pavement[60, 127, 129, 247, 259]  replacement[247]  Rain Barrel [119]  Vegetative Swales [127]

A Review of Advanced Sewer System Designs and Technologies 2-15

Sewer Construction/Rehabilitation Technologies to Control I&I and SSO – Chapter 7.0 [123, 124, 157] Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies  Open-cut Method [154, 192, 239, 247]  Trenchless Technology[152, 153, 189, 191, 195]  Use of Rubber Seals[239]  Slip-lining of Non circular pipe with new  Renovation of Brick Sewer[185] noncircular pipe [162, 192]  Guided Drilling system[205]  Pipe removal and replacement  Lateral Pipe Busting [124, 154, 162, 192, 223,  CIP Resin Technology[205] techniques[223, 239, 247] 247]  CIP Felt Fiber Technology[205] Coating  Glass Reinforced Plastic[162, 205]  Rolldown Polyethylene pipe insertion  Cement Motor Coating [179]  Slug Grouting [198, 247] system[205, 263]  Reinforced Gunite [179]  Cured In Place Pipe(CIPP)[140, 152, 153, 179,  Impact Moling[162, 205]  Resin coating [179] 193, 223, 239, 247]  Spirally wound in situ lining[205, 239]  Epoxy coating [193]  Directional Drilling[239]  Lateral sliplining[247]  Shortcrete coating [193]  Microtunnelling [192, 196, 239]  Vacuum Assisted Resin Transfer Molding  Polyester coating [193]  Horizontal Directional Drilling (HDD) [192, (VARTM) with glass fabric or unsaturated  Silicon coating [193] 196] polyester. ( Technology) [194]  Urethane coating [193]  Auger Boring [192, 239]  HDPE Studded Tube[205]  Vinylester coating [193]  Pipe Jacking [162, 177, 184, 192, 196]  Woven, circular, polyester-reinforced (Fold  Pipe Ramming [162] and form) Liner[205, 239]  Open-cut Method [154, 192, 239, 247]  Moling Technology [177]  Robotic Repair [198, 205]  Use of Rubber Seals[239]  Chemical Grouting [179, 205, 223, 239, 247]  Renovation of Brick Sewer[185]  Spray lining/coating[205]  Guided Drilling system[205]  Pipe removal and replacement  Fold and Form Pipe [193, 223]  Interactive Liners[205] techniques[223, 239, 247]  Deformed Pipe [179]  Panel or Segment Lining[205]  In-situ liners [177, 193]  Percussive Horizontal Boring[205]  Flood Grouting[198]  Segmental Lining[239]  Epoxy Lining[162, 247]  Trenchless Technology[152, 153, 189, 191, 195]  Poured in Place concrete liners[205]

2-16

Pipe Material and Joints for Sewer Systems – Chapter 8.0 Innovative/New Technologies Established Technologies Proven Technologies Experimental & Foreign Technologies Traditional Material for Sewer Pipes: Advanced Pipe and joints material and Advanced experimental pipe materials: components:  Application of Flexible pipe joints in Concrete Pipes:  Use of Combined Lip and Compression Earthquakes prone areas and in  None reinforced concrete Seal for Concrete Pipes[205] expansive soils[205] Pipes[205,250, 258]  Application of Silica-fume (Micro-Silica)  Fiber Glass reinforced concrete pipe [179,  Reinforced Concrete Pipes [205, as additive to concrete to produce  Use of Stainless Steel sleeve with 250, 258] stronger and more durable concrete elastomeric seal for jointing.[205]  Prestressed Concrete pipes and joints.[205]  Use of Flush-jointed VCP[205]205] Cylinder Pipe (PCCP)[205]  Concrete pipe joints Advanced experimental and foreign plastic pipe  Reinforced Concrete  Bell and Spigot[205] materials: Cylinder Pipes[205]  Tongue and Groove[205]  Manufacturing of PVC Alloys[205]  Bar wrapped Steel Cylinder  Modified Tongue and  Manufacturing of Molecular Oriented PVC[205] Concrete Pipe[205] Groove[205]  Use of Recycled PVC material[205]  Rubber gasketed and sealants:  Use of Electro-fusion welding[205] Vitrified Clay Pipe (VCP) and (Use of Bell  Flat[205]  Manufacturing of High Pressure PE[205] [63, 205, 250, 258] and Spigot joints in VCP)  O-ring[205]  Cross Linked PE (PEX)[205]  Spigot[205]  Coated PE Pipe[205] [63, 205] Pipe Material and Joints[63, 205] Cast Iron pipes  Use of Polyester and O-ring joint for  Manufacturing of Circular and Semi-elliptical VCP[205] liner Polymer concrete pipes[205] Ductile Iron Pipes [179, 205, 258]  Use of No-bell joint for VCP[205]  Fiber Glass Reinforced Plastics [179, 205]  Use of Push-on-joints,  Use of Fiberglass-reinforced polyester  Filament-wound GRP Pipes[205] mechanical joints, threaded bells[205]  Closed-wall PVC Pipe forms with in-wall flanges, ball and socket joints,  Use of Jacking Coupling[205 joints[205] and welded joints [63, 205]  Use of Cement Mortar or Bituminous [205] Steel Pipes and joints[205]  In situ PE X Line Liner[205] [205 Asbestos Cement Pipes (AC) [205  In factory PEX diameter reduction  Manufacturing of Ductile Iron Jacking pipes[205]  Use of Polyethylene encasement[205]  Use of Bonded Coating[205]  Other lining materials are Calcium aluminates’ cement, polyethylene or polyurethane, coal tar epoxy, ceramic epoxy, cement epoxy, and thermoplastic coal tar.[205]  Use of field welded joints[205]

A Review of Advanced Sewer System Designs and Technologies 2-17  Ductile Iron Push Pipe[205] Plastic Pipe Material  Polyvinyl Chloride (PVC) [179, 205]  Polyethylene (PE)  HDPE [179, 205]  MDPE[205]  LDPE[205]  Glass reinforced plastics (GRP)[205]  Glass reinforced concrete (GRC)[205]  Polypropylene (PP)[205]  Acrylonitrile Butadine Syrene (ABS)[205] Polymer Concrete[205] Structured Wall Pipes (Profiled Pipes)[205] Composite Pipes:  Concrete-PVC Composite Pipes[205]  GRP-Polymer Concrete Pipes[205]  Concrete-Ceramic Pipes[205]

Manhole Materials:- Innovative technologies in Manholes construction  Bricks[250] materials[205, 247]  Concrete[205, 250]  Application of fiberglass [162, 177]  Plastics [205]  Polymer concrete manholes[205, 247]  HDPE[205] Manhole repair technologies:  Stones[205]  Use of water tight manholes[205] Manholes [63, 205]  Cast in place[205]  Cementitious Lining[239]  Profile PVC or PVC[205]  Cast/Pored in Place, CIP (Concrete and Epoxy)[205]  Fiberglass insert placed inside existing manholes[205]  Coating, or Grouting[239]

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CHAPTER 3.0

ONSITE TECHNOLOGIES

3.1 Toilet Designs and Technologies There are two main types of toilet designs, those designed to use water to flush and those that do not use water. Toilets that use water are known as flush toilets and those that use no water are known as waterless toilets. Flush toilets are the most commonly used toilet design. Waterless toilets are gaining some popularity as society becomes more aware of the importance of water conservation. The history of designs and their use dates back to the 31st century BC in Skara Brae village in the United Kingdom where a flushing toilet was designed using Neolithic hydraulic technology. Flush toilets used today have evolved from this basic concept with such improvements as the ‘S’ trap, invented in 1775 by Alexander Cummings, which uses standing water in the toilet bowl to seal the outlet of the bowl and prevent odor from the sewer from entering into the restroom through the toilet. In 1819, Albert Giblin invented the siphon discharge system; in 1906, William Elvis Sloan invented the Flushometer; in 1907, Thomas MacAvity invented the vortex flushing toilet bowl providing a self-cleaning mechanism; and in 1980, Bruce Thompson developed the Duoset cistern which controls flush volumes for water conservation purposes. [269] Another innovation in the modern toilet system has been the use of sensor technology for toilet and urinal flushing. The three main types of flush toilets in use around the world are the western or cistern flush toilet, squat flush toilet, and dual-flush toilet. 3.2 Water Efficient Toilet Designs and Technologies The conventional western or cistern flush toilets and squat flush toilets use 13-20 liters (3.4-5.3 gal) of water per flush. Water conservation goals have challenged the industry to develop more water efficient toilet designs. To support water conservation efforts, U.S. Congress passed the Energy Policy Act of 1992, requiring all manufacturers in the U.S. to produce and sell toilets that use 1.6 gallons (6.1 liters) per flush. [13] Manufacturers responded and produced “low flush” toilets. However, technical design flaws by many of the manufacturers resulted in poor flushing of solids from the bowl or plugging, turning consumers away from purchasing them. These flaws have been largely eliminated and now all new construction installs low flush toilets, and many consumers have retrofitted low flush toilets when upgrading the plumbing in their homes. Of course rebate incentive programs by water utilities for purchasing low-flush toilets have been a great incentive for the retrofit program. The industry is now producing toilets that use even less water, about 4.8 liter (1.28 gallons) or less per flush. These high efficiency toilets are designed both as single flush or dual flush. The dual-flush toilet allows the user to select half flush for urine or a full flush. High-efficiency toilets can be modified gravity flow or pressure assisted toilets. Pressure assisted toilets can be power assisted, pump assisted or vacuum assisted. U.S. EPA uses a maximum performance score (MaP) to measure the performance of the high efficiency toilets. The lower end of MaP is 250 and the upper end in 1000. The U.S. has set a standard for the high efficiency toilet to be at the score of 350 or higher. [262]

A Review of Advanced Sewer System Designs and Technologies 3-1

3.2.1 Established Water Efficient Toilet Designs and Technologies This section will look at the advantages and disadvantages of water flush toilet designs. 3.2.1.1 Modified Gravity Flow Toilets and Pressure Assisted Toilets The modified gravity flow toilet uses about 1.6 gpf (6 liters), which is much less than the conventional gravity flow toilets that use 3.5 gpf (13.3 liters). Modified gravity flow toilets achieve the same flushing power compared with a conventional gravity toilet. A technology breakthrough occurred by changing the design of the toilet from one that removed waste based on flush water volume, to a new design that removes waste based on flush water velocity. Under the high flush water velocity design, the toilet bowl contour becomes more vertical to achieve the required velocity and this design tends to have less swirl action compared to conventional designs. Another modification included improving the siphoning feature of the fixture. Earlier models had problems with clogging due to designs that increased siphoning by chocking down on the trap size. To fix this problem, manufacturers resized the trap diameter closer to its original size and implemented the modification on rim dimensions, bowl contour, and trap size to make the whole system work together, enhancing the velocity of water and the siphoning functionality. [13] Pressure assisted toilets consists of an inner air sealed tank. When water is fed from the water line, the air inside the sealed tank is compressed and when the toilet is flushed, pressurized water (a mixture of air and water) is forced out of the tank, thus cleaning the toilet using less water per flush. [39] Advantages: These systems use less water, and are preferred more by customers and city planners compared to conventional gravity toilets because of their water savings (and thus cost savings). Pressure assisted toilets are noisier modified gravity toilets, but are more effective at flushing waste from the bowl. For this reason they are often preferred for installation in hotels and commercial establishments. Disadvantages (modified gravity flow toilets): One of the biggest customer complaints is that a double flush is often required to remove the waste from the toilet. Clogging problems have been reported in homes with cast iron sewer drains and or sewer laterals due to the increased roughness of cast iron pipe compared to other materials. A home with a cast iron drain pipe may need to be retrofitted with PVC pipes, which is expensive. Some toilet models have a taller seat which may not be suitable for children and some manufacturers recommend that cleaning chemicals not be added into the flushing water because they tend to change the specific gravity of water and affect the flushing velocity. Disadvantages (pressure-assisted toilets): The most significant complaint regarding pressure assisted flushing is the noise from the pressure tank. Because of the noise problem, installation should be away from bedrooms, which is difficult in a single family residence or apartment. Additional considerations include insuring the availability of electricity for models that require electricity, and a skilled plumber is required to ensure proper installation of the system. Performance and application: Reviews conducted from 1995-1998, in metropolitan areas that use modified gravity flow and pressure-assisted toilet, reported that many customers are satisfied with the performance of their toilet system. In San Diego, CA, Austin, TX, and Tampa, FL about 90%, 95%, and 91%, respectively, were satisfied or very satisfied with the modified gravity flow and pressure assisted toilets performance [13]

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Cost: Most units cost more than $100. Cheaper, imported units may not carry U.S. standard certification, but it has been reported that, generally, all systems perform well. [13] 3.2.1.2 Ultra Low-Flow Toilets The main difference between the low-flow and ultra-low-flow toilets has less to do with cosmetic appeal and more to do with efficiency. In most cases, the tank still holds about 13 liters of water, but only six are flushed at a time. [270] Additionally, some ultra-low-flow toilets don’t have traditional flappers on them and offer the option of a half flush for liquid waste and a full flush for heavier waste. Some models removed the ‘S’ trap to enable waste to be washed down using less water. Other models use a hinged flap which allows waste and water to enter the lower chamber, followed by pressurized air and water that force the waste to the collection line. Another model has a narrow bowl with a smaller water surface and a manually operated foot pedal that facilitates flushing of water into the bowl to empty the toilet (Figure 3-1).

Figure 3-1. Ultra Low-Flow Toilet. Reprinted with permission from Microphor[219][296]

Advantages: This system reduces water demand. Disadvantages: Sometimes more than one flush is required to clean the toilet and discharge the waste into the collection main. Application: Used in public parks, restaurants, hotels, road rest areas, and other public facilities. [219] Cost: $200-1000. 3.2.2 Waterless Toilet Designs and Technologies This section will look at the advantages and disadvantages of waterless toilet designs.

3.2.2.1 Composting Toilets Composting toilets were commercialized in Sweden more than 30 years ago. This system is still new and rarely used in the U.S. The system consists of a composting reactor connected to

A Review of Advanced Sewer System Designs and Technologies 3-3 a dry or micro-flush toilet, a screened air inlet and a fan to remove odor and provide heat exchange. The toilet drains liquid to the sewer and has an access door to remove the compost material (Figure 3-2). Advantages: The system does not use water for flushing, solid waste is reduced by 10-30% of its original volume through biological decomposition, suitable for remote area without a conventional system, very low power consumption, waste can be recycled and used as a soil fertilizer, it can process kitchen waste, and it prevents pathogens and nutrients from contaminating surface and groundwater. Disadvantages: User is responsible for maintaining the system, compost removal is unpleasant work, these toilets are sometimes used in conjunction with a graywater systems, may pose health risk if not well maintained, may have odor problems, and most system may require power source in cold regions.

Figure 3-2. Composting Toilet. [270] Reprinted with permission from Enviro Options, Ltd [271]

Performance issue: Compost toilets require specific conditions in order to maintain performance including presence of microorganisms, temperature, moisture, pH, carbon to nitrogen ratio, aeration, antibiosis, and time of exposure to severe conditions. Due to the difficulty in maintaining ideal conditions, performance issues with composting toilets are a problem. Application: Compost toilets are commonly used in Sweden, Netherland, , Australia, and South Africa. In the U.S, reports indicate that they have been installed in Colorado at Colorado parks, and are commonly known as waterless toilets or solar toilets. [260]

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Cost: For the household size compost toilet system the cost is from $1200-6000. Cottage systems for seasonal use cost between $700 and $1500. Larger capacity system for public facility may cost up to $20,000. The price of these systems depends on manufacturer and the system type. [3] Manufacturer: Clivus Multrum Inc, Enviro Options (PTY) Ltd, Sun – Mar Corp, BioLet, BIO WC, Gough Hybrid Flush/Composting toilets, and Solar Composting Toilets.

3.2.2.2 Incinerating Toilets Incinerating toilets are a self-contained system, consisting of a regular toilet seat connected to a tank. Some incinerating toilets consist of a special paper-lined upper bowl to hold the waste and a release of the waste is done by pressing the pedal (Figure 3-3). Heat is supplied to the tank from an electric source or from a gas fired heating system. The waste is heated and steam water and ash is produced as the final product. About a tablespoon full of ash is produced per use. Advantages: The technology is considered to be pollution free technology, it uses no water, a sterile ash is produced that can be thrown into the trash, the toilet system is portable, simple to install, and easy to use, it is considered an odorless system compared to other systems, and it can be used in both cold and warm climates. Disadvantages: There is a loss of important soil nutrients from the waste after burning, a high energy requirement, propane burning pollutes the air, and some model types can’t be used while the incineration cycle is in progress. In addition, the need to use liners is distasteful to most U.S. consumers. Performance and application: Approximately six onsite incinerating toilets were installed in private homes in Kentucky during 1970-1971. After one year, the incinerating systems in Kentucky were abandoned by the users due to high energy cost and incomplete incineration of the waste. Another study was conducted in Alaska by Alaska Native Area Service and the University of Alaska. Waste was collected over a month and Storburn propane was used to burn the waste at an ambient temperature of -11°C. Storburn Propane successfully reduced the waste to ashes. The ash was about 2.23% of the original weight of the waste. Examination of the ash showed no fecal contamination. [15] Cost: A four-user incinerating toilet unit costs about $2300, an eight-user toilet costs $2700. The propane Storburn unit costs $2550 and natural gas burning unit cost $2590. Electricity costs per month for a family of four using a unit is $160 per month, about $1920 annually. The annual maintenance cost is about $828. [3]

A Review of Advanced Sewer System Designs and Technologies 3-5

Figure 3-3. An Electric Incinerating Toilet. Reprinted with permission from Incinolet® [277]

3.2.2.3 Oil Recirculating Toilets This technology is not produced any more, but is included here because some people are still using it, and it is still listed as an available technology in EPA documents. Oil recirculating toilets are designed to operate using oil instead of water for waste flushing. This type of toilet system comprises a , typically 53 cubic feet in volume which is used to store the oil media and the waste materials, and an oil recycling system which consists of a pump, coalescer, Fuller’s Earth filter, chemical bath and activated carbon media (Figure 3-4). The toilet flushing bowl is normally coated with Teflon or similar coating material to minimize friction between the bowl and the waste material during flushing. The flushing system consists of a closet reservoir with oil refilling mechanisms. In the waste receiving tank, the solids waste settles to the bottom and the oil flushing medium floats to the top of the tank. The flushing oil is then drawn from the top by a pump into the coalescer where it undergoes treatment through several steps.

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Figure 3-4. Oil Recirculating Toilet. Figure from U.S. EPA[20]

Water droplets present from urine and suspended particles mixed in the pumped oil are removed at the coalescer and returned back into the receiving tank. The oil from the coalescer undergoes treatment through Fuller’s Earth filter, chemical bath and activated carbon. After treatment the oil is refilled into the closet reservoir and is ready for reuse. Waste products collecting in the receiving tank must be removed periodically from the tank to avoid accumulation. The system must be designed is such a way that it allows eight minutes of settling time between uses. Advantages: The system does not require water for flushing, and this system is approved by the Coast Guard for marine use. Disadvantages: Mixing of oil and urine can cause an incomplete separation, odor problems and discoloration of the oil medium has been reported. The flushing medium requires replacement after deterioration, the system components require large space for installation and the system requires constant maintenance. It also has oil leakage problems due to vibration of the pipes during flushing, and finding a disposal for the separated waste product can be difficult due to its oil content. Applicability: In rural areas, rest areas located on remote roads, large marine vessels, areas with water scarcity, and sensitive environmental areas. This system has been used in the U.S. since the 1970s by the Commonwealth of Virginia Department of Transportation (VDOT) in four locations along Interstate Highway 64 (I-64). Due to many operational problems experienced in Virginia, VDOT is planning to replace this system with a conventional system that uses water for flushing. All U.S. companies that made the oil- recirculation toilets have terminated manufacturing of this toilet and its parts. [20] Cost: Due to termination of manufacturing of this toilet system, no cost values were available.

A Review of Advanced Sewer System Designs and Technologies 3-7 3.2.3 Foreign and Experimental Water-Efficient Toilet Designs and Technologies This section will look at the advantages and disadvantages of several foreign-designed water-efficient toilet systems. 3.2.3.1 Dual-Flushing Toilets The dual-flushing toilet designs are water efficiency toilet systems. A leading manufacturer in the dual-flushing toilet industry is Caroma®, an Australian company. [278] This company has produced four dual-flushing models, classified based on the volume of water released per flush. These models are the 4.5/3L dual-flush toilet, the 4.5/3L dual-flush toilet with integrated hand basin, the 4/2L dual-flush toilet, and 3/2L dual-flush toilet. The dual-flushing toilets have been modified to maximize the energy generated from less water applied during flushing and the pan has been modified to streamline the flow of flushed water to achieve the required cleaning waste efficiency. The dual-flush toilet with integrated hand washing basin uses graywater that was produced during hand washing to flush the toilet. The tap and wash basin sit on top of the toilet cistern and fill the cistern with graywater as it is generated. Caroma® and other toilet manufacturing companies have released toilets that use less water per flush, but under Australian toilet standards, only toilets that use 4.5/3L per flush or less are allowed for use. In Europe, the company Ifö, has introduced a toilet type called Cera dual flush 4/2L model. Since 1996, it has been installed in more than 5 million locations in Europe. In Scandinavia, a 3/2L dual-flush model with adjustable flush volume has been introduced to the market by Ifö Company but no such a model is in use in Australia. [39] Advantages: Water conservation, water recycling, and water cost savings. Disadvantages: Expensive compared to convention system – costs range between $500 and $1500. Manufacturers: Caroma Inc., Ifö, Laufen, Parisi, Imperial, Vista, American Standard, Gemini, Johnson Suisse, Pubco, and Fowler. [40] 3.2.3.2 Urine Separators Urine separating or urine diverting toilets are designed with two bowls within one pan (Figure 3-5). One of the bowls collects the urine and the other bowl collects the fecal material. To flush only urine, the toilet uses only 0.2 liter per flush. For a full flush of both urine and fecal material, the toilet uses between 4 and 6 liter of water per flush. The collected urine can be used as soil fertilizer and in most case it does not require any treatment. Separating urine from fecal matter provides an opportunity for nutrient recycling and reduction of nutrients in treated wastewater and hence protects lakes from eutrophication.

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Figure 3-5. Urine Separation Toilet. Reprinted with permissions from Dubbletten[297] and Roevac[217]

Another modification is to include waterless urinals within the urine separator system. This will help to reduce the water used for flushing the urine. No system is in the market at this time that combines the urine separator with waterless urinals. The urine separator can also include an ultralow flush system for fecal matter removal. The combined system will require use of vacuum or dry fecal flushing system. Advantages: Water conservation, removal of nutrients from sewer water and the production of struvite from urine which can be used as a soil fertilizer. Disadvantages: Users will need to change their behavior (i.e., both men and woman will be required to sit while using the toilet and no toilet paper can be flushed out during urinal flushing), there is a high cost for retrofitting, a need for regular maintenance, changes in wastewater composition, and need for change in technical and plumbing designs. Application: Urine diverting toilets have been in use in Sweden. Reports indicate that by 1999 there were about 3000 urine diverting toilets installed at different locations in Sweden. Manufacturers: BB Innovation & Co AB, Gustavsberg, Roediger Vakuum + Haustechnik, and Wost Man Ecology. [39] 3.2.3.3 Air-Assisted Flush Toilets The-air assisted flush toilet is a UK product that uses water and pressurized air for toilet flushing. The air is displaced by a small electric motor. The user is required to close the toilet lid before flushing the toilet to form an air seal. During flushing, about 1.5 liters of water is released to clean the bowl followed by displaced air. The displaced air cannot exit the bowl and as a result it forces the fecal matter into the sewer draining pipe systems. The flushing takes about three seconds. [273] The air-assisted toilet does not mix water and air in a tank before flushing. Mixing only occurs during flushing when a small quantity of water enters first followed by displaced air. This makes the toilet different from pressure assisted toilets which mix water and air inside a sealed tank.

A Review of Advanced Sewer System Designs and Technologies 3-9 Advantages: The air-assisted toilet can be retrofitted to existing standard toilets. The toilet system can also be connected to the existing plumbing sewer system and it uses 84% less water than standard toilets. There is no need for double flush. This results in reduction of generated wastewater. They are easy to clean, reduce bathroom odors, and they provide a quiet flush every time. [273] Disadvantages: This type of toilet is still at pre-production stage and is not yet available or tested for commercial use. It will require changes in Australia’s standards to allow the use of this toilet in that country. Application: This technology is at prototype stage, the Water Research Center of UK has conducted successful field tests. [273] Manufacturer: Propelair, Ltd of UK. 3.2.3.4 Waterless Urinals Conventional water flush urinals consume about 5-20 liters per flush (Figure 3-6a). In commercial buildings in Sydney, Australia, conventional urinals consume up to 20% of the total commercial indoor water use and are considered to use up to 2% of the total supplied to the city. In the case that a conventional urinal uses an automatic flushing system and a malfunction of the automatic sensors occurs, the result is very high water loss resulting in a large to cost to the water user. [38] In the U.S, conventional urinals consume more than 3.8 liter per flush.

Figure by M. Hollowed Photo by B. Hodgson byB. Photo Reprinted with permission from Sydney Water

Figure 3-6a. Conventional Urinal. Figure 3-6b. Waterless Urinal.[38] Figure 3-6c. Depiction of How Waterless Oil Barrier Urinals Work.

The waterless urinal has been applied mostly in Australia, although there are a number of installations in the U.S. It comes in three design types: oil barrier, mechanical design, and microbial blocks. The oil barrier design comes with either a refillable or replaceable cartridge. The refillable or replaceable oil cartridge is designed to create a barrier between the user and the urinal plumbing system (Figure 3-6c). The density of urine is higher than that of the oil barrier, so the oil floats on top of the urine and as more urine comes in it moves under the oil. The oil barrier system is designed as a regular ‘S’ trap, so as the volume of urine increases, it overflows into the plumbing collection system. The oil layer prevents odors from the urine and the plumbing system from entering the restroom. Mechanical designs consist of a one way valve that allows urine to enter the plumbing system, but stops odors from returning back into the restroom.

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The microbial block design comprises a water soluble large sugar like block placed in the urinal to release odor preventing agents and that breakdown the components of urine thus eliminating odor and scaling. This system requires a small amount of water to maintain activity of bacteria which breakdown urine. Advantages: The waterless urinal provides a physical barrier between users and plumbing systems. The oil cartridge is easy to replace, and little or no water is required to keep the system clean. Only minimal waste is created, which is collected by the regular drain pipe. The mechanical design allows different types of cleaning products to be used and will not breakdown when a large water volume is dumped in by janitors. The microbial block design can be most easily retrofit to an existing conventional urinal. Waterless urinals may be more streamline, making them easier to clean and reducing the areas where bacteria breed. Disadvantages: For the oil cartridge system, there is a cost associated with cartridge replacement and disposal of oil cartridges creates waste. The oil seal may be lost if inappropriate cleaners or water are introduced into the oil barrier system, therefore, a skilled maintenance staff is required. The mechanical design is very new to the market so durability is unknown; the one way valve in the mechanical design may require regular replacement and corrosive cleaners must be avoided. Use of the microbial block system with older plumbing that has corroded or scaled pipes may produce unpleasant odors. In addition, the microbial block may break down and block the draining system, causing urine to pool and creating odor. [38] Changing the cleaning chemicals may be required to avoid harming the bacteria. Application: Waterless urinals have been widely implemented in Australia. A pilot project, underway at the University of New South Wales (UNSW), uses oil barrier or oil seal trap urinals for new installations and microbial blocks to retrofit existing urinals at the university. Results from UNSW have shown that each waterless urinal saves 95,000-140, 000 liters of water per year on average. Westfield, an Australian company has installed different brands of waterless urinals (microbial cubes, mechanical and oil barrier designs) in shopping centers across Australia. Studies conducted by the Westfield Company have found that all brands tested have similar service lives, but the oil barrier and mechanical design have lower maintenance costs. [38] Cost: In Australia, waterless urinals cost between $350-1500 per unit depending on manufacturers and design. Manufacturers: Britex (www.britex.com.au/arid.htm); Caroma Industries (www.caroma.com.au/products); Enviro-fresh Sani Sleeve (www.enviro-fresh.com.au); Falcon Waterfree Technologies (www.waterless-urinals.com) and Urimat (www.urimat.com) 3.2.3.5 Ultra-Low Flush Urinal Systems The ultra-water efficient urinal or ultra-low flush urinal system uses very little water for flushing. The unit may use less than one liter of water per flush and can also be equipped with urine sensing technology that can help increase water efficiency. One example of the ultra-low flush system in Australia is “The Cube”. The cube system uses only 0.8 liter per flush. The ultra- low flush urinal system can be retrofitted into an existing plumbing system. However, inspection will be required to assess the condition of the existing sewer pipes. Old pipes with corrosion and scale inside will need to be replaced by PVC pipe to avoid excessive odor production if an ultra- low flush urinal is installed.

A Review of Advanced Sewer System Designs and Technologies 3-11 Advantages: It is possible to retrofit these systems into an existing plumbing and sewer system without major system change. The system uses less water, supporting water conservation and reducing water cost, and the system does not require intensive cleaning practices. Disadvantages: Existing sewer pipe will need to have sufficient slope to allow easy draining of urine if ultra-low flow urinals are retrofitted into the old sewer system. Bacteria can cause chemical reactions in older, copper plumbing systems. The production of ammonia, which is corrosive, may lead to serious structural and odor problems. Bacteria can also precipitate calcium from human urine and cause scale formation inside the plumbing system, so it is recommended that copper plumbing systems be replaced by PVC. Cost: The cost of ultra-water efficient urinals ranges from $350-1500. [38] Manufacturers: Caroma Industries (www.caroma.com.au/products); and Urimat (www.urimat.com). 3.2.4 Source-Nutrient Control Plumbing Designs and Technologies This section will look at the advantages and disadvantages of source-nutrient control plumbing designs. 3.2.4.1 Innovative Proven Designs and Technologies Graywater separation technologies Graywater (called greywater or in the British Commonwealth) is water from laundry, showers, wash basins, and baths plus kitchen sinks in Europe and Australia. Blackwater is that water from toilets. However, in the U.S, graywater is generally defined as excluding kitchen water since it has high organic content and potential pathogens from meat preparation (Figure 3-7). Since graywater in Australian/European systems contains kitchen water, it is generally treated to a greater extent than that proposed for U.S. systems. [40][265] In both cases, existing plumbing systems can be retrofitted or installed in new buildings to collect all graywater on site and make it available for reuse at the household level. Separate plumbing is required to collect blackwater from toilets and urinals (plus kitchens in the U.S.). The blackwater is transported through sewer collection lines to the wastewater treatment plant. Graywater is captured on site and can be reused with minimal treatment for landscape irrigation and/or toilet flushing. Graywater reuse for irrigation generally requires minimal treatment, and graywater is supplied through drip irrigation (Figure 3-8) or submerged irrigation systems (Figure 3-11). Disinfection is recommended when graywater is reused for toilet flushing and even more extensive treatment of graywater is required when graywater is used in washing machines and for car washing. [40] A graywater system generally consists of a separated plumbing system, treatment system, pumps, storage tank(s) and valves (Figure 3-7). Treated graywater supply pipes need to be labeled differently from the potable water supply lines and warning signs should be posted at the supply points to prevent someone from drinking the graywater mistakenly. [40]

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Figure 3-7. Graywater and Blackwater System Plumbing. Diagram prepared by J. Bergdolt

Figure 3-8. Drip Irrigation System. Diagram prepared by J. Bergdolt[264]

Figure 3-9. Subsurface Irrigation. Diagram prepared by J. Bergdolt[264]

A Review of Advanced Sewer System Designs and Technologies 3-13

Graywater Systems in Australia/Europe Adoption of graywater reuse for toilet flushing and irrigation have been widespread in Australia and Europe and there are several commercially available systems on the market for graywater reuse in these countries. In general, these graywater systems include extensive treatment of the graywater since kitchen water is included. In Australian and European graywater reuse systems for toilet flushing, treated graywater is supplied from a storage tank located within or outside the home. The toilet tank is supplied by both graywater and municipal water (Figure 3-10). Toilet tank isolating valves, one for the graywater and one for municipal water are recommended and graywater fittings to the cistern should be marked and pipes should be labeled. Backwater prevention is recommended to prevent contamination of drinking water supply (Figure 3-10).

Figure 3-10. Graywater for Toilet Flushing. Diagram prepared by J. Bergdolt

Developing Technology in the U.S. Graywater reuse systems under development in the U.S. vary slightly from systems implemented in Australia and Europe. Graywater Reuse for Irrigation In practice, graywater reuse for irrigation can vary from very simple (a hose attached to a washing machine) to systems which include sand filtration and application of graywater through submerged emitters (such as the system developed by ReWater). In the U.S, kitchen water is generally not included in the graywater definition, and therefore graywater irrigation systems are simpler than those recommended in Australia and

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Europe (Figure 3-7). The recommended system in the U.S. consists of storage, coarse filtration, and pumping of graywater to a drip or submerged irrigation system (Figure 3-11). [264]

Figure 3-11. Components and Layout for the Recommended Graywater Irrigation System in the U.S. Diagram prepared by J. Bergdolt[264]

Graywater Reuse for Toilet Flushing Graywater reuse systems for toilet flushing under design in the U.S. vary from those recommended in Australia and Europe (Figure 3-10) in that the potable supply line is connected to the graywater storage tank (Figure 3-12) rather than directly to the toilet. This way, there will be only one supply line to the toilet, and two supply lines to the storage tank (graywater and potable water). When there is an insufficient amount of graywater in the tank, and the level drops below a minimum, the system can use potable water to fill the tank to a depth adequate for safe pumping operations. A set of valves can be installed to allow the potable water supply to turn on when it is necessary.

Figure 3-12. Components for the Recommended Graywater Reuse System for Toilet Flushing in the U.S. Diagram prepared by J. Bergdolt[264]

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Advantages: Water conservation, nutrient recycling, water cost savings, availability of more water for outdoor activities, and minimizing the wastewater entering treatment plants. In addition, removal of graywater from wastewater results in blackwater which is amendable to anaerobic digestion for the production of biogas. Disadvantages: Health risks from exposure to pathogens, odor problems, risk of groundwater contamination, effects to plant health and soil quality, risk of cross connections that may result in drinking water contamination, wastewater drain pipe clogging due to low flows containing high solids, source of power required for the pumps, and the user needs to understand proper operation and maintenance of the system. [40] Long-term effects of graywater irrigation on soil quality and plant health are currently being addressed through a study by Colorado State University. [266] Application: Graywater separation from blackwater for reuse has been on the frontier of water conservation in the developed world. Countries with arid climates, like Australia, have been working on this approach for years. In the U.S, separation of graywater from blackwater and graywater reuse have been implemented in many states and it is now estimated that about 7% of household in the U.S. use graywater. [261] The leading states on graywater reuse are California (13.9% of its population use graywater), Pennsylvania (7.9%), Florida (6.1%) and New York (4.9%). [261] 3.2.5 Onsite Disposal Sewer System Designs and Technologies This section will look at the advantages and disadvantages of onsite disposal sewer designs. 3.2.5.1 Established Septic System Designs and Technologies Septic systems are commonly applied for decentralized wastewater management in the U.S. A septic system collects, treats, and disposes of wastewater from homes and businesses on site. A common septic system will consist of two major components: the septic tank, and the drain field, or sometimes called a leaching-field or soil absorption field (Figure 3-13). The septic system can provide service to a single house or a cluster of residences. In the case of multiple residences, the septic tank consists of multiple units, combined with multiple drain fields. Septic systems provide wastewater treatment for many communities in rural areas of the U.S. According to U.S. EPA, septic systems provide service to about 26 million homes and businesses in the U.S. [5] The percentage of use varies from state to state. The highest number of users is in Vermont, where roughly 55% of residents use septic systems.

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Figure 3-13. A Septic System. Diagram prepared by M. Hollowed

3.2.5.2 Septic Tank The septic tank will be made of either concrete, plastic (polyethylene), or fiberglass material. Older systems may have used brick and blocks for construction of the septic tank. The septic tank is buried shallowly to allow access for operation, repair and maintenance and is designed to be water tight to avoid groundwater and surface water from infiltrating the system. Wastewater flushed from the home or business remains in the tank for at least 24 hours to promote settling of solids and separation of oil, fats and grease by flotation to the top of the tank. Effluent from the center of the wastewater layer is allowed to flow out of the tank to the soil absorption system for further treatment and disposal (Figure 3-14).

Figure 3-14. Septic tank and Absorption Trench Field. Figures from U.S. EPA [5][14][32]

The septic tank provides facultative treatment of the wastewater. About 50% of the solids entering the septic tank from the house are digested inside the septic tank, and the remaining 50% accumulates inside the tank. The accumulated solids must be removed every two to five years for the tank to work effectively. The septic tank inlet and outlet pipes should be at least four inches in diameter and may be constructed of PVC, cast iron, or other approved material. A 4-inch diameter PVC pipe is commonly used to connect the septic tank with the house wastewater plumbing. Septic size depends on the number of bedrooms in the house. For one to

A Review of Advanced Sewer System Designs and Technologies 3-17 three bedrooms a 1000 gallon tank is required; for five bedrooms a 1500 gallon tank is required. The following formula is commonly used to estimate septic tank volume[30]: Tank volume = (1.5 x Daily sewer flow) + 500 Advantages: It is considered a low-cost technology for wastewater collection and treatment in rural areas and in areas without access to conventional sewer collection systems; minimal technical skills are required to manage and operate the system, and in most cases a septic system does not require energy to operate. Septic systems do not require regular maintenance; they are less disruptive to the environment during installation and maintenance, and less expensive to operate than centralized treatment system. If the system is functioning properly it can recharge the groundwater significantly. If well designed, installed and maintained, the septic system can have a minimum life expectancy of 20-30 years. [219] Disadvantages: Perhaps the biggest disadvantage of septic systems is that it is the responsibility of the property owner to maintain them, and, in most cases, there is usually no monitoring or oversight of maintenance by a municipal, county or state agency. Routine maintenance carries a risk of exposure to pathogens and viruses from human waste; in addition, septic systems can be a source of flammable and toxic gases so care must be taken during opening of the septic manholes for maintenance or inspection. Sludge must be pumped out every two to five years, and safe disposal of the septic sludge is an issue. The discharge of strong cleaning chemicals into household drains may disrupt the septic tank treatment process and cause system failure; excessive use of pharmaceuticals and personal care products may affect septic system treatment ability, water from hot tubs/whirlpools should not be discharged into the septic tank to avoid excessive water into the system, and water treated by water softeners should not be discharged into the septic system. It is difficult for home owners to know if their systems are failing thus there is a risk of groundwater pollution from dysfunctional systems. Leakage from septic systems can increase E. coli bacteria in surface water bodies and may cause closure of swimming pools, lakes and . Untreated effluent from failing septic systems can adversely impact wildlife and aquatic populations; nutrients from septic effluent can cause eutrophication of lakes. Septic systems should not be used in areas with high chance of flooding. Finally, septic systems are not very effective in cold climates, Performance issues: As solids accumulate inside the septic tank, the residence time of the wastewater in the septic tank decreases and the settling efficiency is reduced. This will result in solids escaping from the tank and getting discharged into the soil absorption system. Excess solids affect the treatment ability and will eventually clog the absorption system, causing sewer overflows. This may also cause effluent to be released to the groundwater and surrounding environment without proper treatment posing health risks to both humans and other living organisms in the area. To correct this problems sludge accumulating in the septic tank needs to be pumped out periodically. Tank capacity, quantity of wastewater discharged into the tank, misuse of the tank as a garbage disposal, and performance of the final treatment system are the factors that control the required pumping frequency of septic sludge. [32] Cost: A general cost assumption for septic tanks is $1.00-4.00 per gallon, so a common 1000- gallon tank will cost around $2000 on average. Other costs involved are site dependent and include the cost of the drain field, cost to transport the septic tank, excavation cost, and other material costs.

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3.2.5.3 Conventional Drain Field or Absorption Field The conventional drain field/absorption field receives effluent from the septic tank by gravity. The absorption field receives septic tank effluent through perforated drain pipes or through a closed pipe. The perforated pipe releases wastewater into a buried gravel trench, while the closed pipe release wastewater into a free water surface lagoon or wetland. The gravel and soil surrounding the perforated pipe provides filtration necessary for removing suspended solids, bacteria and viruses. The absorption field soil matrix also facilitates microorganism growth which assists in the removal of dissolved toxic and organic pollutants present in the wastewater. Some absorption fields consist of a distribution box located just after the septic tank to provide even distribution of effluent to the absorption field. Wastewater released into a free water surface lagoon or wetland undergoes treatment through natural attenuation provided by the system which may be covered with vegetation to enhance the evapotranspiration process. Figure 3-15. Conventional Drain Field Designs. Figures from U.S. EPA.

Figure 3-15a. Mound. [17]

Figure 3-15b. Intermittent Sand Filters. [16]

Figure 3-15c. Evapotranspiration System. [8]

A Review of Advanced Sewer System Designs and Technologies 3-19

Figure 3-15d. Free Water Surface Wetland. [280]

Figure 3-15e. Shallow Trench. [28]

Figure 3-15f. UV Disinfection System. [279]

In general, the drain field provides an area for safe disposal of effluent as it undergoes biological treatment at the disposal site. The perforated pipes can be surrounded by filtering media such as gravel, sand, activated carbon media, chipped tires, geotextiles, and others filtering materials. The drain field that receives water underground is covered by loamy soil. For conventional drain fields, established technologies include the use of a mound system, sand filtration (buried and intermittent), evapotranspiration, wetlands, lagoons, shallow trenches, narrow trenches, continuous trenches, vegetated submerged beds, stabilization ponds, land application, UV disinfection, aerobic treatment, fixed film processes, sequencing batch reactors,

3-20 enhanced nutrient removal – phosphorus, enhanced nutrient removal – nitrogen, and recirculating sand filters (Figures 3-15 a-f). [5][14] A detailed description of each treatment technique for onsite disposal is beyond the scope of this study. Advantages: Conventional drain field systems require less mechanical equipment, less energy consumption, minimal operational attention, lower construction and operational costs, and they provide better quality effluent. Treatment occurs year round; however, treatment is higher in warm and moderate climates. No sludge is produced at the drain field, it provides , and no chemicals are required, making it a more environmentally friendly technology. Disadvantages: Requires a large area of land, nutrients such as phosphorus and nitrogen accumulate in the soil over time and can cause pollution of groundwater and surface water, the conventional systems are not suitable in cold climates, failing drain fields may be a source of bacteria, viruses and other harmful microorganisms that can cause serious health problems to both humans and aquatic life if one comes in contact with the drainage, unpleasant odors can be associated with the treatment system area, the treatment system has a limited storage capacity, salts may accumulate in the soil at the treatment site, with time clogging of the media filter is possible, access to the treatment field needs to be restricted for small children to avoid the risk of exposure, mound system construction costs can be higher than other conventional systems, the system may affect the natural drainage pattern in the area, and a pump or siphon may be required in some conventional systems, such as the mound treatment system. Performance: Design of conventional absorption fields is determined by the number of bedrooms per house, specified as 150 gallons per bedroom. Systems have been over-designed to account for periods of high flow to reduce failure from overloading. Conventional systems cannot treat certain toxic liquids such as , paint thinners, photographic film chemicals, and other hazardous chemicals. These chemicals kill the beneficial bacteria found in the septic system and in the treatment drain field and as a result disrupt the system’s treatment process. Freezing temperatures may severely hinder the system’s performance, so in most cases conventional absorption field treatment systems should not be used in colder climates. While in areas with excessive evapotranspiration the effluent concentration may increase, areas with high precipitation may see dilution of the pollutant concentrations. Regardless, normal performance of the system is largely dependent on climatic conditions at the site. 3.2.6 Septic System Innovative Designs and Technologies Experience has shown that if a septic system is well designed, installed and maintained it can provide an effective permanent solution to onsite collection and treatment of wastewater at very low cost compared to conventional wastewater collection and treatment facilities. A well- functioning septic tank can reduce BOD5 by 40% and suspended solids by 70%. As experience and knowledge have developed, innovative ideas have evolved on how to improve the performance of septic systems. Some of these new technologies can be added to existing septic systems and some can only be implemented in new systems or during replacement of the septic tank or drain field. [10] 3.2.6.1 Septic Tank Innovations Concrete tanks are still in use in septic systems, although polyethylene and fiberglass tanks are gaining popularity because they are light weight, which makes them portable and easy to install. However, these light weight tanks will need to be anchored in the ground to withstand the flotation force during times of high groundwater. To ensure effective use, a length to width

A Review of Advanced Sewer System Designs and Technologies 3-21 ratio of 3:1 is recommended for septic tanks and the outlet pipe should be at least three feet from the bottom of the tank. Original septic tanks had only a single chamber, but now multiple chambers are preferred as they provide a longer settling time and prevent effluent with solids from short circuiting through the tank to the outlet. The multi-chamber tank consists of two or more compartments created by an internal separation wall with an opening to allow wastewater to flow from one compartment to another (Figure 3-16). The first chamber should be larger than the other chambers to ensure good performance. Studies suggest the first chamber should be two- thirds of the total tank volume. [10]

Cover

Outlet tee Inlet tee

Liquid Gas deflector

Sludge

Figure 3-16. Dual-Compartment Septic Tank with Sanitary Tees and Gas Deflector. Diagram prepared by M. Hollowed

At the inlet and outlet of the septic tank, T-shaped pipes are used to control the direction of inflow to the tank and outflow from the tank. These tees are commonly known as sanitary tees. At the inlet, the sanitary tee directs the influent to the bottom of the tank with minimum disturbance of the tank contents and also limits the possibility of short circuiting of incoming wastewater. The outlet sanitary tee is located in such a way that only the settled effluent will be allowed to enter and be discharged to the drain field. In some designs a gas deflector is placed near the outlet tee to divert gases from entering the discharge tee, thereby minimizing the odor problem as the effluent is discharged out of the septic tank. These sanitary tees also prevent scum from entering the pipe by allowing it to float above the mouth of the outlet. Modern septic tanks may be equipped with gas vents near the top of the tank which connect to an odor treatment system or back to the house vent and discharge hydrogen sulfide gas and methane gas generated inside the septic tank. In some septic systems, the inlet and outlet sanitary tees are open at the top to allow gases to escape from the tees. Another innovative component is the use of risers on new and existing tanks. One small riser is placed at the location of the inlet sanitary tee and the other small riser is placed at the outlet sanitary tee. These small risers provide easy access for maintenance of the sanitary tees and also for filter replacement or inspection. One big riser, usually larger than 24 inches wide, is placed at the manhole to provide access to the tank for maintenance, solids removal from the tank, and for rehabilitation and other renovation activities.

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Figure 3-17. Septic Tank Effluent Screen. Figure from U.S. EPA[7]

A septic tank effluent screen installed inside the outlet sanitary tee, or outside the septic tank, is another modification placed on modern septic systems to remove solids that may otherwise escape from the septic tank through the outlet pipe. Providing filtration of the effluent before it is released to the drain field (Figure 3-17) helps to protect the drain field from clogging and hence maintains good functionality of the drain field over an extended period of time. The effluent filters are designed to retain suspended solids with a size greater than 3mm (1/8 in) in diameter. The septic tank can be equipped with a smart filter switch with a smart filter alarm to alert the user about filter condition. [7] In some situations, a thin layer of organic growth, called biomat, may develop on the screen’s surface and provide removal of some viruses and pathogens that would otherwise end up in the drain field. The installation of effluent screens is required in more than 50 counties within the U.S. and it is mandatory in the state of Florida, Georgia, North Carolina, and Connecticut. Septic systems used in cafeterias, restaurants, hospitals, schools and other commercial buildings that may generate excessive grease during food processing or cooking are now also equipped with grease traps. [10] The grease trap is placed before the septic tank collection compartment. This prevents fat, oil, and grease (FOG) from entering the septic tank and accumulating there. It also minimizes the chance for FOG to escape from the tank and be released to the absorption field. Modern septic systems can be equipped with siphons and effluent pumps depending on site topography or soil condition. [9] Advantages: Septic systems discharge an improved quality of effluent and prevent solids and other non-degradable materials from clogging the drain field. The improvements are easy to install in existing septic tank systems and installation of low cost filters further assists in removing harmful viruses, bacteria and solids particles that can cause deterioration of the absorption field. Multiple chambers increase the solids settling time, minimize odor problems and remove FOG from the effluent, thereby increasing the life span of the system. The use of risers on the septic tank provides easy access to the tank for inspection and maintenance. Disadvantages: Multiple compartment septic tanks require more frequent pumping compared to single compartment tanks, filters and other innovative components must be purchased and installed, adding cost to the system. Filter clogging can result in sewer overflow and backflows;

A Review of Advanced Sewer System Designs and Technologies 3-23 regular cleaning of the effluent filter is required. A source of power may be required for smart filter alarm systems, pumps, and other components that may use electricity. These added components will require routine inspection and maintenance. Performance: There is enhanced performance over conventional septic tank systems when using multiple chambers and effluent screens. As a result, the quality of effluent discharged to the absorption field is also enhanced. 3.2.6.2 Absorption Field Innovations To design a well-functioning absorption field, a thorough site examination needs to be conducted during the planning phase of the project. A number of site condition factors need to be examined including: sufficient land area is available for the absorption field, soil type, vertical soil profile to determine the presence of obstructions or impermeable layers, soil permeability, soil structure and texture, site slope, groundwater table, and natural drainage pattern and landscape features, and the presence of water wells in the area. Climatic conditions of the area (temperature, rainfall, solar radiation, wind, etc.) are also required. This valuable information about the characteristics of a particular site will provide useful information regarding a suitable drain field system and it will also provide information about site limitations. As more lessons are learned about the performance of onsite treatment systems, new and innovative features and techniques have been added in existing and newly constructed site treatment systems. The distribution box and drop box has been added to new and existing distribution drain field systems to provide even distribution of effluent to the distribution lines. Both the distribution box and drop box use gravity to distribute wastewater through the drain field by placing the drain field lower than the inlet pipe. [9] A Low-Pressure Pipe (LPP) system is a septic system innovation for use in areas where the distribution system is located at a higher elevation than the septic tank, or in areas with unsuitable soil conditions. A low-pressure effluent pump is connected to a system of small diameter perforated pipes placed 25.4-45.7 cm (10-18 inches) deep in narrow trenches, approximately 30.5-45.7cm (12-18 inches) apart. The effluent pump is used to control the dosing of effluent to the drainfield (Figure 3-18).

Figure 3-18. Low-Pressure Pipe System. Figure from U.S. EPA[18]

The LPP system was introduced in North Carolina and Wisconsin to eliminate clogging of the soil media that was caused by gravity system overloading, continuous saturation of the soil and a high water table.

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The main parts of the LLP system are the septic tank, a pumping chamber, an effluent pump, level control, high water alarm, supply manifold and small diameter distribution laterals constructed with small perforated pipes. The effluent pump pushes the wastewater through the supply distribution line to the distribution laterals in trenches with a pressure of 0.91-1.5 meters (3-5 feet of pressure head). Small PVC pipes of 0.4-0.64 cm (0.16-0.25 inches) diameter are used to distribute the wastewater in the drain field. The level controls are set for specific pumping sequence one to two times per day. A minimum of 0.3 meters (12 inches) of suitable soil is required below the bottom of the absorption field followed by underlying bedrock or some form of impermeable layer. About 0.5-0.76 meters (20-30 inches) of soil is required for the total depth of the drainage trench, and about 93-465 square meters (1,000-5,000 square feet) of land is required for the drain field area.[18] Advantages: The system can be used in shallow soils to promote evapotranspiration. The drain field can be located in higher ground than the septic tank, and the pump provides a well- controlled dosing of effluent flow into the drainfield. The additional cost is small compared to other alternatives, and the system is not affected by peak flows as is a gravity system, requires less gravel at the drain field, can be applied in sloping grounds, and the drain field area required is smaller compared to other treatment systems. Disadvantages: Efficiency is easily affected by soil conditions, possibility of clogging in small diameter pipes with small holes by soils and roots, very limited storage in the drain field, effluent pump requires source of energy to operate, cost of electricity, and regular inspection and maintenance is required for mechanical and electrical parts. Cost: In North Carolina where this system is in use the average cost for the system installation is between $1,500 and $5,000. A Septic Tank Leaching Chamber is another innovation in septic system design. This onsite wastewater treatment technology has been developed by Infiltrator System, Inc. [24] The septic system consists of a septic tank and an absorption field system known as a leaching chamber. A leaching chamber comprises a high density polyethylene arch-shaped pipe with an average internal width of 5-102 cm (20-40 inches) and a length between 1.8 and 2.4 meters (6 to 8 feet). The polyethylene leaching chamber is open at the bottom to allow free movement of water over the soil surface inside the trench system. Leaching chambers may be laid over soil or gravel. [33] Using gravel may improve the soil absorption rate in areas with low permeability soils. Advantages: A leaching chamber is much easier to install, no soil compaction is required at the trenches, no gravel is required for areas with moderately permeable soils, the leaching chamber provides temporary storage of wastewater during high effluent loading, maintenance and inspection of the chamber is simple, the system requires little maintenance to function properly, useful life of the leaching chamber is 15-25 years, and no clogging problems are expected to occur in the leaching chamber. Disadvantages: Not suitable in areas with soils of very low permeability unless used in combination with gravel to increase the infiltration rate, can be expensive if a low cost source of gravel is not available in the area, higher chance of groundwater pollution compared to a standard gravel drain field, not suitable in areas with very high permeability soils that are directly connected to the groundwater aquifers or surface water bodies, and not suitable in areas with very steep slopes.

A Review of Advanced Sewer System Designs and Technologies 3-25 Performance: The following factors affect the performance of the leaching chamber: soil characteristics, ground slope, available land area, depth to groundwater table, and presence of other waterbodies and water wells in the area. Cost: The cost of single family septic tank/leaching chamber drain field was $2000-5000 in 1993. [33] Control Panels are another feature added in modern onsite treatment systems. A control panel consists of controls and sensors that keep the system functioning properly and sound an alarm whenever a system failure occurs (Figure 3-19). Control panels used in septic systems consists of circuit breakers, automatic/manual/off toggle switches for each pump, automatic motor control operation, an audio/visual high level alarm, and automatic reset control system. [274] Control panels monitor the dosing of influent to the treatment system to ensure effective treatment and protect the treatment system from overloads. Control panels are capable of providing remote control and monitoring of the system. [29]

Figure 3-19. Sand Filter Control Panel. Reprinted with permission from Orenco Systems® [274]

Advantages: Control panels can protect the treatment system from overload, alert the operator in case of system malfunction, provide remote control and monitoring, prevent failures and reduce time spent for data gathering about system failure, improve system manageability and reliability, and lower energy consumption. Disadvantages: A skilled operator is required to maintain the system, capital cost of the onsite treatment system is increased, it requires an energy source to operate, and it requires regular maintenance for mechanical and electrical components. Application: This system has been installed in River Rock Landing, Michigan and is currently serving 29 homes outside of Lansing; it has also been installed in Island City Academy, Michigan outside Eaton Rapids, Michigan. The control panel system can be used to control a septic tank effluent pump, low pressure effluent dispersal system, aerobic treatment system, recirculating sand filters and drip dispersal systems. Cost: The price of control panels was $1500-3000 in 2000.

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Enviro-Septic Treatment System is another innovative septic treatment system that has been introduced to the market by Make-Way Environmental Technologies, Inc. of Ontario, Canada. However, Presby Environmental, the inventor of this technology, is a U.S. based company. This system was designed to optimize both aerobic and anaerobic bacterial treatment of septic tank effluent prior to discharging to the surrounding soil. Optimizing treatment prior to dispersal into the natural soils reduces the size requirement and increases longevity of the system. The Enviro-Septic treatment system consists of a distribution box, offset adaptor, Enviro-Septic pipes and bio-acceleratorTM fabric, pipe couplings, ventilation pipes, piezometers, and system sand (Figure 3-20).

Figure 3-20. Advanced Enviro Septic® System Treatment Components. Reprinted with permission from Presby Environmental[290]

The Enviro-Septic pipe is the notable design component for this treatment system. The pipe contains a 30cm diameter high density plastic pipe which is corrugated and perforated with skimmer tabs that extend into the pipe at the point of each perforation. Warm effluent enters the pipe and is cooled to ground temperature. Suspended solids and grease that remain in the effluent separate from the liquid effluent as it cools. The skimmer tabs assist in separation of solids and scum from the liquid layer in the corrugated pipe. A bio-acceleratorTM fabric layer sits below each pipe, partially covering a layer of coarse fibers (Figure 3-21). The bio-accelerator fabric screens solids from the effluent and develops a biomat. The layer of coarse fibers, which extends around the circumference of the pipe, further assists in removing solids. A non-woven geo-textile layer holds all the components in place and provides a protected surface on which another layer of biomat develops. Liquid exiting the geo-textile fabric is wicked away from the piping by the surrounding system sand. This assists in cooling the effluent and enables air to transfer to the bacterial surfaces. Anaerobic bacteria utilize the effluent to form biomat layers on the provided surfaces during high flows and during low flows, aerobic bacteria consume the biomat. Bacterial efficiency is increased by the large air supply and fluctuating liquid levels which provide large food supplies. [26][290]

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Figure 3-21. Advanced Enviro-Septic Pipe Design: 10 Steps of Treatment. Reprinted with permission from Presby Environmental[290]

Advantages: It is a natural, non-mechanical system, does not require an input of electricity, adapts to difficult sites by way of a smaller treatment field and easy blending on sloping terrain, it requires less fill and is easier to install compared to traditional septic systems, there is no need for expensive washed stone, it adapts easily to both commercial and residential sites, provides a stable pH and protected surface for bacterial growth which increases septic system performance and longevity by facilitating a naturally balanced, that utilizes both aerobic and anaerobic bacteria, it more effectively reduces CBOD5, fecal coliforms and TSS when compared with conventional drain field technology and recharges the groundwater with better quality effluent than conventional septic systems. [26] All of these advantages contribute to a cost- effective system. Performance: Effluent quality after treatment with Enviro-Septic is expected to meet U.S. EPA Tertiary Treatment guidelines, NSF Standard 40 Class 1 requirements and BNQ Secondary and Advanced Secondary requirements (Quebec).

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CHAPTER 4.0

ALTERNATIVE WASTEWATER COLLECTION SYSTEM DESIGN AND TECHNOLOGIES

It was realized in the late 1960s that developing conventional sewer systems for rural communities, with such dispersed populations, was not economically feasible. The high cost for conventional collection system development was due to long lengths of pipeline required to connect homes to the main collection system and the cost of lift stations required by some communities to move the wastewater to the treatment plant. [208][233][287] Operation and maintenance costs for the conventional system in rural communities, with limited resources and skilled technical personnel to operate the system, was another challenge. Transporting solids from a single household through a long pipeline to the main collection system could result in solids deposition inside the pipeline due to low flow and could cause pipe blockage. For many years, the use of septic systems has been the technology of choice for many rural communities. Septic tanks provided low-cost wastewater collection, treatment, and disposal. However, septic system failure has been a major source of groundwater and surface water pollution in many areas across the U.S. and around the world. To improve the existing wastewater collection system designs and technologies for rural communities, a new era of rethinking was required. To address these challenges, researchers in the U.S. went back to the late 19th century to review technologies that had been in use in other countries, but were not popular in the U.S. In 1991, U.S. EPA published an alternative wastewater collection system manual with detailed information on how to install, operate, and maintain alternative systems as well as locations in U.S. where these systems are in use. Three alternative sewer collection systems were addressed including pressure sewer systems, vacuum sewer systems, and small diameter gravity sewer systems (also called effluent sewer systems). Application of these alternative sewer collection systems is not limited to rural communities; they can be used in small towns and in selected areas of major urban centers. [209] 4.1 Pressure Sewer System Designs and Technologies Pressure sewer systems are designed to convey wastewater under pressure created by a pump. There are two main pressure sewer system designs; these are the grinder pump system and the septic tank effluent sewer (STEP) system. 4.1.1 Established Pressure Sewer System Designs and Technologies A grinder pump system is a type of pressure sewer system that consists of a 0.75 kW (1 hp) to 3.75 kW (5 hp) grinder pump placed in a chamber, namely a wet well, that has a capacity of approximately 30 gallons. Other components of a grinder pump system include a control panel, a buried electrical cable, an electrical junction box, sewage pipe from the house to the wet well, plumbing disconnect, a shut off valve, service line to the main, a level sensor, and check valves (Figure 4-1). Solids from wastewater are ground into small pieces and then pumped out into a pressurized sewer pipeline. The diameter of the service line from the grinder pump to

A Review of Advanced Sewer System Designs and Technologies 4-1 the sewer collection main is 25-38 mm (1-1.5 in). Polyvinyl chloride (PVC) and high density polyethylene (HDPE) are the most common pipe materials. In cold regions, pipes are buried below the frost line, considered to be about 75 cm (30 in) minimum in depth. Selection of an operating pressure for the grinder pump system depends on the operating head that needs to be overcome by the grinder pump; some grinder pumps can provide a head of up to 30m (100 ft). Additionally, a check valve can be provided at the junction between the service line, from the grinder unit, and the collection main to prevent sewer backflow into the house. To develop a design for a grinder pump system, a preliminary study should be conducted to evaluate its suitability to the particular area. The following information is required prior to installation of the grinder pump system: the area topography, soil conditions, climatic conditions, water table depth, applicable codes, discharge location, lot layout and total number of lots, dwelling type, use and flow factors and the area development sequence. Selection of a grinder pump system is based on the occupancy per household and the quantity of flow expected to be generated from the household. For an average single-family home, the expected flow is up to 700 gpd. The most common location for a grinder pump installation is in the basement of the building it will serve. Waste from the toilet flows by gravity into the wet well. When the wet well fills to a certain level a sensor is triggered and the pump is switched on, grinding and pumping the waste from the wet well into the discharge line (Figure 4-1). The grinder pump can also be installed outdoors; however, it is recommended to install the unit as close as possible to the building. This will help reduce the chance of groundwater infiltration into the system; it will also keep the cost of pipes and electrical wiring cables low. Power to run the pump should be supplied from the house. When multiple families need to be served more than one pump may be required. [275] A common 1hp grinder pump, operating at a pressure head 0-80 psig, will have a total dynamic head of 0-180 feet with a discharge range of 7-15 gpm.

Figure 4-1. Grinder Package System. Figure from the Florida Department of Environmental Regulation[212]

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Different pipe materials can be used for the main sewer system; however common types of pipe used are PVC and HDPE. A continuous coil of small diameter HDPE pipe can easily be installed with an automatic trenching machine or by a horizontal drilling machine to lower the installation cost. Discharge from the grinder pump is connected to the main by a small diameter pipe (Figure 4-2). An air/vacuum valve needs to be installed in the main sewer at each high point along the system. Cleanouts and/or flushing stations should be installed every 1000-1500 feet of line.

Figure 4-2. Grinder Pump System. Reprinted with permissions from NESC[216]

Advantages: Grinder pump systems are easy to install compared to conventional sewer systems. Solids are ground at the source, thereby reducing chances of pipe blockage, no residual is pumped out of the wet well, and there are no odor problems. The system provides sewer service in low lying areas (i.e., lake communities), pipes are buried at shallow depths which reduce excavation costs and increase ease of repair, small diameter pipes lower the capital cost, no manholes are required, the system is water tight so there is no problem with infiltration and inflow as in conventional sewers and no septic tank is required. It seems that these systems could be retrofit into existing I/I dominated conventional sewer systems by running the main collection pipes within the existing pipes. This would minimize open trench excavation and the concomitant disruption of community life. Disadvantages: Grinder pumps increase capital cost to the household and require an energy source – electric bill increases by $10-30 per year per household. Grinding sewage produces high concentrations of organics and solids that can easily become anaerobic (odor problems), a skilled operator is required to maintain the functionality of the system, annual inspection is required for the mechanical and electrical components, and shallowly buried small diameter pipes can easily be damaged by traffic loading. Cost: In many communities connecting to an existing pressure sewer requires buying the grinder pump and paying the connection cost. The capital cost ranges from $1000-2500, the operation

A Review of Advanced Sewer System Designs and Technologies 4-3 and maintenance cost for grinder pump and power is $20-25 per year, and sewer use fee is approximately $130 per quarter. [213] WEF reported that the retail price is $3500-5000 per unit, but by buying 50 or more grinder pumps, the cost may be as low as $2000-2500 per unit. [233] The price of installation is $1,500-2000 for a new home. Monthly service fees for maintenance and management of the system are $35-100. Connection fees for a homeowner, which include paying for the existing piping system, infrastructure and treatment facility, are $4000-8000. Performance: Failure of the grinder pump means failure of the household system. A reliable maintenance operator is required for quick repair of the system to insure continuous sewer service at the household. Accumulation of grease has been reported to be a problem, interfering with the operation of float switches in the wet well, so enzymes need to be applied in the pump vault to reduce the grease accumulation. Flushing of solid materials into the toilet such as disposable paper towels, baby dippers, sanitary napkins, underwear, kitty litter, cigarette filters, and other items should be avoided because they have been reported to damage the grinder pump. Moisture has been reported to be a problem to some electric control panels; a sealant should be applied inside the conduit to prevent the flow of moisture and gases into the control panel. Groundwater infiltration into the pump vault is another reported issue; routine inspection needs to be conducted to insure that no groundwater infiltrates into the pump vault. Pump guide rail systems and close up valves need to be used to insure proper functionality and avoid malfunctioning. To insure self-cleaning velocity and prevent solids accumulation in the sewer pipes an average velocity of 60-90cm/s (2-3 ft/s) is required. Application: In the U.S, the use of pressure sewers has grown significantly since its initial implementation in 1970s and can now be found from Florida to Alaska and from California to New York. Most of the systems serve between 50 and 200 homes, with few systems serving more than 10,000 homes. [287] Septic Tank Effluent Pump (STEP) system is another type of pressure sewer system. This system comprises a septic tank that collects household wastewater and a low horsepower pump to transfer the wastewater from the septic tank into the collection main. Wastewater from the household flows into the septic tank by gravity just like a conventional septic system. Settling and natural flotation within the septic tank creates three separate layers with solids at the bottom, FOG and floatables at the top and partially clear water in the middle of the tank, similar to a conventional septic tank. A filter can be applied to remove any floatable solids in the effluent before pumping. An effluent pump is located in a pump vault that is separate from the septic tank (Figure 4-3). Water at mid-height in the septic tank enters the pump chamber through perforations in the pump vault wall. The pump is controlled by level sensors in the vault; as wastewater enters the pump vault, it accumulates to a certain level, triggering the pump, which discharges all the wastewater inside the pump vault to the main sewer system, providing room for a new batch of wastewater to enter the vault from the septic tank. The pumped effluent enters the collection system which transports the effluent to the wastewater treatment plant. [216] The STEP tank is designed to provide a sewage retention time of 24 hours before being pumped to the collection main.

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Figure 4-3. STEP System. Reprinted with permissions from NESC[216]

Other components of the STEP system are the small diameter plastic pipe, which connect the septic tank to the collection main, isolation valves, cleanouts, air release valves, pipe fittings, and pump accessories such as the pump vault, level sensors, vent, control panel, and a junction box. The building’s sewer pipe is about 10-15cm (4-6 in) in diameter; the pipe material can be cast iron, vitrified clay, PVC or HDPE. Sludge in the tank must be pumped out in every two to five years to maintain proper functionality of the system. The pipe from the STEP to the collection main is 25-38mm (1.0-1.5 in). The capacity of most STEP tanks ranges is 3785-11,360 liter (1000-3000 U.S. gal). Material used for the tank can be , fiberglass, or plastic (PVC). The concrete tank can weigh up to 3600 kg (4 tons) and has a life expectancy of more than 25 years. Light weight tanks made up of plastic or fiberglass will need to be anchored into the ground to prevent buoyant forces from lifting the tank during high groundwater conditions. [287] The STEP system can be applied in areas with low housing density, hilly or undulating terrain, areas with significant underlying rock formations, standard flat sites, areas with a high water table, areas removed from existing conventional sewer infrastructure, areas where avoiding infiltration and inflow is critical and in areas with acid sulfate soils. It could also be retrofitted to conventional wastewater systems being overtaxed with I/I. Just like the grinder pump system, the STEP system does not require modification of the existing plumbing in the house. Thus, a house plumbing system formerly used with a conventional sewer system can be transformed into a STEP system with minimal effort. The only new installation required will be a septic tank with a pump that is connected to a collection service line. The retrofitting of existing septic tanks in areas formally served by septic tanks and drain field systems presents an advantage if the septic tank is of sufficient capacity and it is in

A Review of Advanced Sewer System Designs and Technologies 4-5 good condition, but large numbers of these existing septic tanks will need to be replaced with new septic tanks because of insufficient capacity, the presence of leaks and fractures on the walls of the tank and deterioration of the tanks due to age. [5][14] Advantages: The septic tank provides pretreatment of the sewage by removing solids and FOG. This reduces the required size of the main wastewater treatment facility and potentially eliminates the need for primary clarification; the occurrence of sewer blockage is eliminated since the effluent from the septic tank is free of solids, and grease coating the sewer walls is greatly reduced; the septic tank removes about 50% of BOD, 75% of TSS, and 90% of FOG; material and trenching costs are significantly reduced due to the use of small diameter pipes buried at shallow depths, cleanouts are used instead of manholes which reduce the construction cost significantly, the system has minimal infiltration due to small pipe size used with water tight joints (except where STEP systems are retrofit to existing systems), they are cost effective in low density areas and in high density areas where the right of way is challenged, and they can be applicable in terrains where gravity sewer is not practical. Disadvantages: The operation and maintenance cost for a STEP system is higher than that of a conventional sewer due to the need for electrical and mechanical components. The septic tank requires sludge pumping every two to five years; initial capital cost for the pump, septic tank, and connection fee can be higher for a household than a conventional system; power outages can result in septic tank overflows if no standby generator is available; the household will need to pay for electricity used by the pump which may increase the monthly household electricity bill, the life expectancy of the STEP system is lower than that of conventional sewer system, odors and corrosion are potential problems because the sewage is usually septic; and public education is required to prevent disposal of chemicals into the septic system which can adversely affect the functionality of the microorganisms inside the tank. Performance: The effluent from the septic tank has zero dissolved oxygen and can be septic as it enters the collection main, this can cause serious corrosion to the sewer main at the junction, however, the quality of effluent from the septic tank is better than that of a conventional system because it has an average BOD of 110 mg/L and TSS of 50 mg/L. Disposal of hazardous chemicals such as pesticides, paints, photographic solutions, varnishes, thinners, and waste oils can kill the microorganisms inside the tank and affect the performance of the system; solids such as coffee grounds, dental floss, disposable diapers, napkins, paper towels, cigarette butts and condoms should not be flushed into the STEP system because they can block the septic tank effluent filters and cause septic overflow. To insure STEP system longevity the homeowner needs to have the septic tank inspected annually, have the septic tank sludge pumped regularly, consult professionals whenever a problem occurs, and be mindful of the quantity of water entering the system at once (i.e., from the laundry). Homeowners should avoid flushing water that contain softeners into the STEP system, avoid driving or parking on any part of the STEP system, and they should not open the septic tank in the absence of a professional to avoid release of toxic gases into the air which can cause air quality problems around the house – these gases are extremely toxic and may result in death if inhaled in large quantities. Application: The STEP system is very popular in Australia and it is gaining popularity in the U.S. The small community of High Island, Texas, replaced its failing septic tank system in the late 1990s with a pressure sewer system equipped with a large STEP unit. With this system they expect to achieve an effluent BOD concentration of 20mg/L, 20 mg/L of TSS, less than 8 mg/L of ammonia, and greater than 4 mg/L of dissolved oxygen. In 1996, Village of Browns, Illinois,

4-6 implemented a STEP system to replace its deteriorating septic tank sewer system. The system has eliminated the public health risk that was posed by septic tank overflows and leakages. [5][14] Cost: The capital cost for STEP systems in rural and suburban areas is lower compared to conventional sewer systems. Total O & M cost is $100-200 per year, on average. The total capital cost of the STEP unit, on average, is $7900. [287] 4.2 Innovative Designs and Technologies in Pressure Sewer Systems Pressure sewer systems are still considered a new technology in the U.S. Many larger cities still use conventional systems to convey their wastewater to the treatment plant. The pressure sewer remains an option in areas where a conventional sewer system is problematic due to population density or terrain; however, technical wastewater system personal and engineers are reluctant to use pressure sewer systems because they have limited experience and knowledge about the capabilities of these systems. Conventional systems are more established and engineers have good technical knowhow on their capabilities and limitations. Possibly one of the largest drawbacks and potential inconveniences of pressure sewer systems is the possibility of pump failure at the residence – a drawback not present with gravity systems. However a number of innovations have been adapted in the components manufacturing industry that attempt to address pressure sewer system issues and make them a more reliable option. More powerful and durable pumps are on the market including the submersible semi positive displacement grinder pump, submersible centrifugal grinder pump, low pressure sewer system pump, and submersible sewer grinder pump. 4.2.1 Foreign and Experimental Designs and Technologies for Pressure Sewer Systems In Australia, pressure sewers are installed using directional boring technology. This method is preferred because it does not require open trenches which are more difficult in urban areas. 4.3 Vacuum Sewer System Designs and Technologies The vacuum sewer collection system was first introduced in Europe in 1882, but for many years it was treated as the last option, used only if a conventional sewer system were impractical or too expensive. Vacuum sewer technology has been used more around Europe during the last 100 years; however, this technology has only been introduced commercially in the U.S. since the late 1960s. They were first introduced by Electrolux Corporation of Sweden. In the U.S, the vacuum sewer and other alternative sewer collection systems were funded by the U.S. EPA and the USDA’s Rural Utilities Service. More funds were provided after the innovative and alternative (I&A) technical provision of the U.S. of 1977 was passed. Under the I&A program more than 500 alternative collection systems were installed in rural and small communities around the U.S. In the 1990s, the I&A program was terminated and replaced by the State Revolving Fund (SRF) which continues the legacy of the I&A program. When the vacuum sewer was introduced in the U.S, they faced many technical problems because only a few engineers knew how to install and operate them properly. In addition, components used in the early vacuum sewer collection systems were still evolving. Advancement in components technologies and increased awareness of this technology by many engineers has caused vacuum sewer to become a reliable and efficient system.[241] Today, vacuum sewers are used in aircraft, space shuttles, ships, trains, as well as in public and private buildings. [286]

A Review of Advanced Sewer System Designs and Technologies 4-7 A vacuum sewer collection system uses the differential pressure between atmospheric pressure and the partial vacuum maintained inside the pipeline to transport sewage from household collection pits to a central vacuum station. From the central vacuum station, wastewater is conveyed to the treatment plant. The main components of a vacuum sewer collection system are the collection chamber and vacuum unit, the vacuum sewer line, the central vacuum station (Figure 4-4a-b) and a force main system that moves wastewater discharged from the vacuum station to the treatment plant. A traditional gravity line transports wastewater from the household to a collection pit, which can accommodate up to four homes, but it is recommended to be used for only two adjacent homes. The collection pit is made of Polyethylene pipe (PE) material and it is divided into two parts; the upper chamber, called the valve pit, houses the vacuum interface valve and level sensors. The lower chamber, known as the sump, is an air tight chamber to which the gravity service line from the house flows; it also contains a suction pipe and a flexible connector that connects the collection pit outlet pipe to the vacuum sewer main. These two chambers are sealed from one another. The collection pit also comes with an anti-buoyancy collar and has an H-20 traffic load rating. As wastewater fills the collection pit, it also rises inside a 50mm (2in) diameter sensor pipe, forcing trapped air to push a diaphragm attached to a sensor in the valve pit. When the wastewater volume reaches 38 liters (10 gallons), a vacuum valve opens and the differential pressure forces the wastewater into the vacuum main. The vacuum interface valve is pneumatically controlled. The vacuum inside the sewer line generated by vacuum pump at the vacuum station opens the valve and the outside air from a breather pipe located inside the valve pit closes the vacuum interface valve. The interface valve is 75 mm (3 in) and it can handle up to 75 mm (3 in) solids. The “sawtooth” profile of the vacuum main (Figure 4-5b) consists of small diameter pipes, typically 100mm (4 in), 150 mm (6 in), 200 mm (8 inc), or 250 mm (10 in) of SDR 21 gasketed PVC pipe or PE pipe. The PVC pipes are installed in shallow trenches at a depth of 300-600mm (1- 2ft). The vacuum main slopes at 0.20% towards the vacuum station; only a 0.20% slope is required to attain a sufficient self-cleaning velocity because the pressure difference produces velocities between 15 to 18 ft/sec. The maximum allowable length of the vacuum main to the vacuum station is 3 km (10,000 ft) in flat terrain. This length is restricted due to vacuum losses associated with every lift in the saw tooth profile.

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Figure 4-4a. Vacuum Sewer System. Reprinted with permission from AIRVA

Figure 4-4b. Vacuum Sewer Pipeline. Reprinted with permission from AIRVAC

A Review of Advanced Sewer System Designs and Technologies 4-9

The vacuum station consists of two or more vacuum pumps, two sewage discharge pumps, a collection tank, control panel, vacuum pump exhaust, vacuum supply main to the collection pipe, forced main to the treatment plant and a standby generator (Figure 4-5). [215] A standby generator may be required at the vacuum station to keeps the vacuum system in operation during power shortages.

Figure 4-5. Components of a Vacuum Station. Reprinted with permission from AIRVAC

The vacuum pump maintains a vacuum of -0.5 to -0.7 bars (16-20 in of mercury) throughout the collection system. The vacuum pumps do not run continuously but operate in cycles; in total they run 2-3 hours per pump per day. As wastewater from the collection pit enters the collection main pipe, atmospheric air enters the collection main and the vacuum pressure decreases from -0.7 bar (20 in) to -0.5 bar (16 in) of mercury. When this happens, the vacuum pumps at the vacuum station are triggered and bring the pressure back to -0.7 bar (20 in of mercury) within 3 minutes. Rotary pumps are typically used and they come in sizes of 7.5, 11, and 18.7 KW (10, 15, and 25 horsepower). Wastewater, from the vacuum main, discharges to the collection tank, located in the vacuum station. The collection tank is made of steel or fiberglass and its size is based on the

4-10 expected design flows. Common tank sizes are 3.8-22.7 m3 (1000-6000 gallons). When the tank fills to a predetermined level, a sensor/control triggers the sewage pumps, which pump the tanks content to the treatment plant via a force main. The typical discharge pump system contains two, non-clog, dry pit, horizontal, centrifugal sewage pumps, each with a capacity of pumping design peak flows, that pump sewage from the collection tank in the vacuum station into a force main that connects to the wastewater treatment plant. One pump will be fully operational while the other will remain on standby for emergencies or peak flow pumping. These two pumps can also work together by alternating pumping cycles. A dry pit can be used to perform the same task as the centrifugal sewer pump. The electric controls are housed in a NEMA Type 12 enclosure and can use either relay or PLC logic. The panel consists of motor starter, control relays, pilot lights, hand off auto (HOA) switches and hour run meters. A seven day chart is installed in the enclosure to monitor system performance, and an automatic telephone alarm dialer is provided to alert the operator of alarm conditions. [215] 4.3.1 Old Vacuum System Designs and Technologies The earlier vacuum sewer collection systems were equipped with a single compartment collection pit with an external air breather. The early collection main joints were also designed with solvent welded PVC pipe joints. Joining the pipes was time consuming and there was a high risk of pipe leakage and loss of vacuum. Early collection main designs were based on liquid plug flow concept, assuming that the sewer water forms a complete plug and seals the pipe during static conditions. Following a flush from the collector pit, the pressure difference behind and in front of the plug created a driving force that carried the plug through the pipe. It was found, however, that pipe friction caused the plug to disintegrate after travelling for a short distance, breaking the seal between the leading and trailing edge of the plug. To deal with this problem the collection main was redesigned with reformer pockets to allow the plug to reform by gravity and restore the pressure difference (Figure 4-6).

Figure 4-6. Reform Pocket Sewer Collection Pipeline Design. Reprinted with permission from AIRVAC[241]

A Review of Advanced Sewer System Designs and Technologies 4-11 4.3.2 Innovative Proven Vacuum Designs and Technologies In the newest design, the old saw tooth pipe profile with reformer pockets was replaced by a saw tooth design that allows the wastewater to occupy part of the pipe without filling the pipe completely (Figure 4-7). Air is allowed to flow over the wastewater surface and as a result, the vacuum created at the vacuum station can be transferred easily to each collection pit in the network. This design ensures maximum pressure differential at each collection pit. When sewage enters the vacuum main from a collection pit it travels as far as the inertial force can carry it before the friction force of the pipe brings it to rest. When other valves in the system open additional sewage and energy enters the pipe moving the wastewater already in the line closer and closer to the vacuum station. When no vacuum valve is in operation there is no sewage movement inside the pipe. The ability of the vacuum to recover quickly during a new flush is a function of pipe diameter, pipe length, number of connections and the lift force in the system.

Figure 4-7. New Saw Tooth Sewer Collection Pipeline Design. Reprinted with permission from AIRVAC[241]

In the 1980s, welded PVC pipe joints were replaced by O-ring PVC pipe joints equipped with a double lipped gasket. This new joint eliminated leakage at the pipe joints significantly. New materials have been used successfully in the vacuum sewer collection mains including thermoplastic PVC (typically Class 200 and SDR 21 PVC), MDPE, HDPE, DIP and ABS. In the 1990s, AIRVAC introduced a new innovative device to replace external breathers. This new device, called an in-sump breather, uses atmospheric air inside the sump (bottom compartment) of the collection pit to provide the air and atmospheric pressure required to operate the vacuum valve. A new air intake was installed in the household gravity sewer (Figure 4-8). An air intake pipe, with a screen, was placed at the outside of the house connected to the existing plumbing pipe that carries wastewater to the valve pit. Most vacuum sewer systems installed after 2000 employ an in-sump breather.

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Figure 4-8. New In Sump Breather System with Air Intake Pipe. Reprinted with permission from AIRVAC[233]

In the early 1970s, collection pits were designed to have side by side arrangement of the valve pit and the sump with rigid piping connecting the two chambers. This design had two major problems: differential settlement led to pipe breaks resulting in vacuum leaks, and the glue connecting the piping failed frequently resulting in vacuum leakage. The new design of the collection pit consists of top/bottom arrangement without the connecting piping (Figure 4-9). The top compartment houses the vacuum valve, in-sump breather, and the service line. The bottom compartment, known as sump, consists of the sensor line and the suction line. This bottom compartment also holds the wastewater temporarily before it is pumped into the service line. The early valve pits were made of PVC or concrete but today fiber glass material is used as it is highly resistant to hydrogen sulfide and other corrosive agents. The new collection pit is also equipped with a flotation collar that keeps the valve pit in the ground in case of a high water table, and prevents the buoyancy effect on the tank that can force the tank out of the ground.

A Review of Advanced Sewer System Designs and Technologies 4-13

Figure 4-9. Modern Collection Pit. Reprinted with permissions from AIRVAC[233]

More recently, buffer tanks have been used with vacuum sewer collection systems. They are used instead of collection pits in high density buildings such as schools, apartments, nursing homes, and hospitals to provide a larger capacity for wastewater collection before pumping. The buffer tanks are constructed from concrete, and are 132 cm (4 ft) in diameter, allowing for more storage compared to conventional collection pits. The buffer tank is equipped with a sump pump to discharge the waste into the collection main. Buffer tanks can also be designed as dual tanks to provide additional storage and are equipped with two vacuum valves to provide more pumping capacity. Each dual buffer tank is 165 cm (5 ft) in diameter and made of concrete. Other innovative ideas used in today’s vacuum sewers include using gate valves to isolate different service zones to allow for maintenance without shutting down the whole system, use of cycle counters to monitor the number of valve cycles, use of electronic air admission controls to monitor the vacuum inside the pipeline, use of gauge taps for vacuum sewer troubleshooting, and use of division valves to isolate sewer collection main sections (typically division valves are installed every 450-600 meters (1500-2000 ft)). Forms of identification on vacuum pipe have included the use of magnetic trace tape, metal toning wire on top of the pipe, use of utility frequency based electronic markers, and use of color cording of the vacuum pipeline. [215] Advantages: Vacuum sewer systems use small, low cost pipe sizes, typically 10-25 cm (4-10 inches), manholes are not required, unforeseen obstacles can be easily bypassed during installation of the vacuum mains and pipes are buried in shallow trenches which helps save on cost. There is no residential power requirement; power is only required at the vacuum station

4-14 where the vacuum system ties in to the force main system. The collection pit is more concealable on the customer’s property than the grinder pump station. A vacuum system is a more suitable system for high-efficiency toilets than gravity-flow systems. The high velocity in vacuum sewer mains eliminates sewer blockage and keeps the wastewater aerated and mixed, minimizing the production of hydrogen sulfide and reducing the problems associated with hydrogen sulfide; there is no significant odor problem reported in vacuum sewer systems, and grease has not been reported to create problems. Corrosion problems are minimized because the vacuum sewer components are made of corrosion resistant material. Leaks are easily detected because abnormal changes in pressure do not go unnoticed; infiltration, a common problem in conventional sewers, is eliminated. Finally, the vacuum sewer system can provide service in areas where a conventional sewer system is impractical or too expensive (i.e., areas with unsuitable soils, flat terrain, undulating land, a high water table, restricted construction, rocky ground, new urban development in rural areas, and in areas with sensitive ecosystems). [241] Disadvantages: The system will not operate during power outages or a malfunction at the vacuum station. A good air to liquid ratio is necessary to avoid water logging but may be difficult to maintain, grease can cause problems at the collection pit if a vacuum sewer is used at a restaurant without installing a grease trap. Performance: Vacuum sewers are designed not to exceed 3.9 meters (13 ft) of static head and 1.5 meter (5 ft) of friction loss. The preferred maximum length of a vacuum line is 3 km (10,000 ft) for flat terrain and the distance is shorter for hilly topographies. Long pipe runs with no house connection should be avoided to prevent sewer transport problems due to lack of energy input; experience has shown that a vacuum sewer system works best if there are many small energy inputs. Vacuum sewers should not be used as an intermediate collection system (i.e., collecting wastewater by gravity and then using a vacuum sewer as an interceptor will not work). The use of buffer tanks should be limited to 25% of the total peak flow of the entire system (water logging may occur if too many buffer tanks are used). The house vent should not be used as the air intake; this may result in evacuation of house plumbing traps during a valve cycle. [215] Application: Vacuum sewers are used worldwide. The U.S. alone has more than 250 vacuum sewer systems. Based on data from 2006, there are more than 35 countries with vacuum sewer systems and a total projected number of more than 1000 vacuum sewer systems used worldwide (Table 4-1). In the U.S, states with highest number of vacuum sewer systems are Florida (35), Indiana (34), West Virginia (26) and Virginia (21).

A Review of Advanced Sewer System Designs and Technologies 4-15

Table 4-1. Countries with Vacuum Sewer Systems. [241]

North America Europe Canada United States England Netherlands Mexico Scotland Poland

South America and the Wales Germany Brazil Bahamas Ireland Check Republic Puerto Rico West Indies Italy Slovakia Asia Spain Slovenia Japan Brunei France Lithuania Korea Oman Greece Hungary Malaysia Qatar Other Thailand UAE Australia New Zealand South Africa

Cost: The cost for installation of a new collection pit and appurtenances is shown in the table below. For a single household the cost is $4000-4500. Manufacturers: AIRVAC, ISEKI, ROEVAC, Vac-Q-Tec, and EVAC. EVAC and Vac-Q-Tec are not operational in the U.S; however, the rest still operate in the U.S. Table 4-2. Installation Cost for Valve Pit and Appurtenances (4th quarter 2006). Table from WERF[268]

Item Unit cost (US$) Standard valve pit (1.8 m [6ft] deep $3500 to $4000 Deep valve pit (2.4 m [8ft] deep $4000 to $4500 Single buffer tank $4500 to $5000 Dual buffer tank $5500 to $6000 Optional anti-flotation collar $160 to $185 Optional flexible connector $90 to $110 Optional cycle counter $250 to $300

4.3.3 Foreign and Experimental Designs and Technologies for Vacuum sewers Horizontal Directional Drilling (HDD) has been introduced for the installation of vacuum sewers pipelines; however, the adoption of this technology to its full capacity is still evolving due to some difficulties in implementation. The main problem has been with current installation machines. They are unable to maintain a slope less than of 0.5% when a slope of 0.2% is desired. Use of Supervisory Control and Data Acquisition (SCADA) at vacuum stations has increased. Through SCADA the operator need not be at the vacuum station to regulate the pumps or valves. Operators can review real time information on system performance from the office. Soundproofing installation has been used at vacuum stations in close proximity to homes and businesses and standby generators have been added to vacuum stations in case of power outage.

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4.4 Small Diameter Gravity (Effluent) Sewer System (SDGS) Designs The use of small diameter sewer system designs in the U.S. has been limited to small communities without access to a conventional sewer systems and urban areas where a conventional wastewater collection system is not feasible including areas with high groundwater, very flat terrain and rocky ground. Using small diameter, gravity sewer systems allow agencies to avoid high excavation and construction costs. However, in other parts of the world, specifically Australia, small diameter, gravity sewer systems are well developed and have gained wide spread use in both small and larger communities. 4.4.1 Established Designs and Technologies Small diameter gravity sewer (SDGS) systems receive effluent from a collection tank or septic tank and convey it to a conventional conveyance system, to a pump station or to a treatment plant. Wastewater, from the household, flows by gravity into a septic tank, which separates settleable solids and FOG from the wastewater. Treatment performed by the septic tank in SDGS systems is similar to a conventional septic tank; however, there is no onsite disposal facility for SDGS. The partially treated effluent flows out of the septic tank by gravity through the service lateral pipe to a main collection pipe which transfer the effluent to a pump station or to a centralized wastewater treatment plant (Figure 4-10).

Figure 4-10. Small Diameter Gravity (Effluent) Sewer. Figure from U.S. EPA[222]

The settleable solids and FOG are collected inside the septic tank and only clear effluent is released to the collection main. This allows for the use of small diameter pipes to transport effluent long distances without clogging problems since the solids content of the wastewater is low. Cleanouts are used instead of manholes for repair, maintenance or adding new connections. Solids and FOG that accumulate inside the tank require removal at least every two to five years, depending on the septic tank size and number of households connected to it. Regular solids removal will ensure high quality effluent is discharged into the collection main and prevent the small diameter pipes used in effluent conveyance from clogging. Effluent released from the septic tank is septic so it can result in odor and pipe corrosion. To eliminate this

A Review of Advanced Sewer System Designs and Technologies 4-17 problem, all components used in SDGS must be corrosion resistant. If a SDGS discharges to a concrete pipe collection main the SDGS pipe must be connected through an inlet below the liquid level in the collection main to minimize odor and provide mixing with less corrosive flow in the main pipe. The recommended minimum pipe diameter for the SDGS is 80 mm (3 in). This size is not commercially available so it would need to be custom ordered. However, commercially available, 101.6 mm (4 in) pipe is commonly used in practice. Pipes are buried at shallow depths, 600-750 mm (24-30 in). Cleanouts are spaced 120-300 meters (400-1000 feet) apart. The common interceptor/septic tank size installed at the household is 1,000-1200 gallons. Advantages: Construction costs are significantly reduced for SDGS because of low excavation cost, use of small diameter pipes (which are easy to transport and install, reduces material cost, and construction time). Pipes are buried at shallow depths so they can easily be replaced and elimination of manholes minimizes infiltration and inflow. Minimal skill is required to run the collection system because solids transport through the pipe system is reduced, decreasing the possibility of sewer blockages, and the collected wastewater requires less treatment at the wastewater treatment plant because the organic loading carried by the effluent is significantly reduced after solids removal at the septic tank. [222] Disadvantages: Septic tank solids need to be removed every two to five years; this is the responsibility of the homeowner. If the homeowner is not conscious about cleaning their tank, significant problems with sedimentation can occur in the collection mains. The sewer effluent is septic so there is high potential for odor generation and high potential for corrosion of both metal and concrete. Good ventilation is necessary to reduce the danger of hydrogen sulfide gas at the treatment plant. SDGS systems are not suitable for commercial wastewater collection due to high FOG generated at restaurants which may interfere with the function of the septic tank, disposal of solids from the septic tank remain a challenge for SDGS, and in areas where freezing temperatures are common during winter months pipes must be buried deeper. Application: SDGS have been commonly used in Australia since the 1960s, and applications in the U.S. have grown substantially since they were first introduced in the 1970s. It is estimated that about 250 SDGS systems are now in operation in the U.S. This system design has been adopted by many small towns and rural communities in the U.S. as they are considered to be more cost effective wastewater collection systems in low population density areas, in areas with terrain not conducive to conventional sewer installation, and in areas where conventional system development in not feasible. Construction of many of the systems in the U.S. was financed by U.S. EPA’s Construction Grant Program. 4.4.2 Innovative Proven Designs and Technologies Some components have been added to the original SDGS design to improve performance and provide better quality effluent discharged from the septic tank. These components include the application of effluent filters to eliminate the discharge of solids into the collection main, and other enhancements noted in Section 4.1 regarding enhancement of septic tank performance. Another technological advancement introduced in SDGS systems is the application of pumps inside the septic tank to lift effluent from areas of low elevation to the sewer collection main located at a higher elevation. Design specifications for pumped septic tanks are covered under the STEP specifications (see Section 4.1). Another innovation is the application of air release/vacuum valves and check valves at different locations along the pipeline to control pressure buildup and negative pressure that can

4-18 develop within the conveyance system. If a pump station is used in areas of low grade, odor problems may occur as a result of conveying septic wastewater through the SDGS to the pump station. To address odor problems at pumping stations several techniques are in use including use of carbon filters to clean the air released from the sewer at the pump station vent, buried gravel trenches at the end of the air vent, and drop inlets from the influent sewer pipe to the pumping station. Odor problems can also be experienced at the onsite septic tank. To minimize odor problems at the septic tank an on-lot balancing tank system for hydrogen sulfide stripping can be applied. Corrosion problems are minimized at the lift station through the use of corrosion resistant materials. For the conveyance system, corrosion is prevented by selecting corrosion resistant materials for the pipes and the septic tank. Fiber reinforced plastic and high density polyethylene (HDPE) materials are used for the septic tank. PVC and HDPE pipes are used for sewer conveyance to minimize I&I, and control corrosion. [209] 4.4.3 Foreign and Experimental Designs and Technologies Small diameter gravity sewers (SDGS) were first introduced in Southern Australia, in 1962, to reduce onsite septic system overflows and malfunctioning effluent drain fields and to address the health risks posed by these overflows to the communities in Australia. In Australia, SDGS are known as Septic Tank Effluent Disposal (STED) systems. There were more than 100,000 people in Southern Australia (SA) served by the SDGS in 1998. The SDGS in Southern Australia (SA) were originally designed by the Engineering and Water Supply Department (EWS) now known as SA Water Corporation with Health Department approval. Design criteria for the SDGS in SA includes the peak dry weather flow of 140 L/c/d, a minimum pipe size of 100 mm and a grade of 0.4% for the conveyance pipelines. In conventional sewers the dry weather peak flow is 250 L/c/d, minimum pipe size is 150 mm and the grade required is 0.5%. Low flow, small pipe size and a lower grade provides an advantage to SDGS over conventional sewerage collection systems. The SDGS system in SA uses flushing points instead of manholes, and flexible plastic pipes instead of concrete or vitrified clay pipes. In SDGS conveyance pipelines, PVC pipes are used to transport the septic tank effluent to the treatment facility. Desludging of the septic tanks is carried out every four years; some of the sludge is used beneficially to rehabilitate the Brukunga pyrites mine in the Adelaide Hills of Australia, and some of the solids are composted for use as pasture fertilizer. In SA, the most common wastewater treatment applied is a centralized oxidation lagoon. The oxidation lagoon treatment system comprises two or three lagoons with a water depth of 1.2 m and a hydraulic retention time of 60 days. Recent treatment facility innovations include the use of the high rate algal ponds designed to have a simple paddle wheel mixer and baffles to improve performance and reduce lagoon size. In the U.S, the construction cost for SDGS is $2000-7900 per connection, which was found to be one-half of the estimated cost for the conventional sewer system. [268] SA has introduced the SDGS effluent reuse after additional treatment. Treated wastewater reuse in SA includes broad acre, recreational and landscape irrigation. To insure public health the effluent from the lagoon is disinfected by chlorination, filtration, and UV disinfection. [281] The Small Bore Sewer System (SBSTM) is an evolution of the SDGS system that was introduced in Canada in 1989 and was used in pilot projects in 2000. SDGS in Canada are sometimes called Small Diameter Variable Gradient sanitary collection systems. The main design innovation in SBSTM was to create a conveyance sewer system with jointless pipelines, sewer effluent free of solids, and no I&I. To achieve jointless pipelines the SBSTM design used thermally fused HDPE pipes that were installed by directional drilling with variable alignment and variable gradients. Septic tanks were modified from a single compartment to two chambers

A Review of Advanced Sewer System Designs and Technologies 4-19 to increase solids removal efficiency. The first chamber was extended to 82% of the total length to provide more solids settling time and a larger biodegradation window. The modified septic tank provided more efficient removal of greasy scum and solids than the conventional septic system. The tank was designed with an outlet flow attenuation device to provide constant discharge even during peak inflows. To create a system free of I&I, the septic tank was designed to be water tight with Polylok III High Pressure Closed End Boot Seals cast into the wall during the casting of the tank for use as inlet and outlet connections. In the collection system, access points or cleanouts are provided every 150 meter (500 feet) along the graded piping sections and at critical intersections. The cleanouts or system access points are designed to function as air release valves by placing an air valve at the air filter location (Figure 4-11). [225]

Manual of

, p 4, © 2008, WEF,

12

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Reprinted with permission from Practice FD Alexandria, Virginia

Figure 4-11. Small Bore SewerTM System Access Point. [225]

One of the pilot projects was conducted in Wardsville, Canada, a small rural community in southern Ontario with approximately 170 homes, businesses and a golf course. The project provided a cost-effective solution to the community by reducing the capital cost by 47% compared to a conventional sewer system. No major internal plumbing was necessary, only a collection main was installed at the back of the SBSTM septic system at household level. Pipes were installed using horizontal boring technology and the project was completed in eight months with no road closure or traffic interference. The average suspended solids at the treatment facility were measured to be 39mg/L, compared to 237mg/L at a conventional facility. The pipe diameter used was 75mm (3 inches) throughout the project. Total peak design flow was reduced by 77% compared to the conventional sewer, I&I was essentially eliminated compared to conventional sewer with 100 L/cap/day as I&I. were reduced by 83%, BOD5 experienced a 45% reduction compared to a

4-20 conventional sewer. Sludge holding capacity for the tanks used in the Wardville project was theoretically estimated to be seven years. After seven years the sludge will need to be pumped out to allow the system to function efficiently as per design. Overall, the project was perceived to be successful. [225] 4.5 Hybrid Sewer System Designs Hybrid Sewer Systems present a new design theory that combines alternative wastewater collection systems with conventional waste water collection systems. Wastewater collected from an alternative sewer collection system (i.e., SDGS, vacuum sewer or a pressure sewer) is discharged into a collection main which then transports the wastewater to the centralized municipal wastewater treatment facility. This may be the most cost-effective approach for communities located too far from conventional sewer systems to justify connection to those systems. [234] However, care must be exercised when connecting alternative sewer systems with conventional sewer systems. The main concern is the septic nature of the sewer water from some of the alternative sewer collection systems. For example, sewer water from SDGS is considered septic. Proper mixing with the flow in the sewer main will need to be assured before connecting these two systems together. On the other hand, sewage discharged by a pressure sewer is considered to have high suspended solids due to the use of a grinder at the household, so proper mixing with the larger municipal sewer flows is required to meet the TSS acceptable at the conventional wastewater treatment facility. Odor problems associated with alternative sewer designs can cause problems at the treatment facility. Proper ventilation must be provided at the treatment plant to prevent buildup of hydrogen sulfide gas. However, if the flow from the alternative sewer is very low compared to that carried by the conventional main, this problem may not be a significant concern. Studies, including demonstration projects, need to be conducted to assess the challenges that may exist by combining the alternative sewer collection system with the conventional system. Literature on hybrid sewer system design was not available. Hybrid sewer design approach seems to be a gray area for research and development in sewer collection systems. One hybrid sewer (LPS and Gravity) was proposed in 2007 for La Canãda, a housing area of Flintridge, California. About 1801 household connections were proposed to be connected to this hybrid system. The gravity sewer was proposed for the part of the city with gently sloping ground and the low-pressure sewer was proposed for the area of the city with hilly, rocky, and more complex topography. [282]

A Review of Advanced Sewer System Designs and Technologies 4-21

4-22

CHAPTER 5.0

GRAVITY SEWER SYSTEM DESIGN

The conventional sewer systems comprise two main types; the Combined Sewer System (CSS) and Separate Sanitary Sewer (SSS) System. The CSS is designed to convey both stormwater and sanitary sewage in the collection system, while SSS conveys only sanitary sewage. During low precipitation periods, CSS convey only the sanitary sewage to the treatment plant where it undergoes treatment and is subsequently discharged to receiving water bodies such as , lakes, groundwater, or to the sea. During storm events stormwater fills the CSS pipes and the capacity of the wastewater treatment plant may be exceeded. When this happens, the excess wastewater is released into receiving waters without treatment. These events are referred to as combined sewer overflows (CSOs). The CSO wastewater contains an untreated mix of stormwater and sanitary sewage water. Discharging CSOs into receiving waters has been associated with human health problems and environmental degradation. On the other hand, SSS also experience overflows as a result of pipe structural failure, solids blockage or pump failure. The overflows from SSS are called sanitary sewer overflows (SSOs). SSOs contain concentrated sewage with high suspended solids and, because it is collected from toilets, high potential to carry harmful pathogens and other pollutants. Both CSOs and SSOs contain bacteria from human and animal fecal material that can cause illness, oxygen demanding pollutants that deplete oxygen in receiving water bodies and harm aquatic organisms, carry high concentrations of suspended solids which increase in water bodies, carry high levels of nutrients that may cause eutrophication in slow moving receiving waters, and carry floating litter that may become a health and aesthetic nuisance in receiving waters. 5.1 Combined Sewer System (CSS) Established Designs and Technologies The CSS collection system conveys both sewage and stormwater, typically by gravity flow from the collection sites to the treatment plant or disposal site (Figure 5-1). Because CSS collection sewers are also storm drains, they must be designed to provide drainage for infrequent storms, typically the 10-year storm. However, the wastewater treatment facility is generally designed to treat only two to five times the average sanitary flow. If the sewage generation rate of a typical property is computed in gallons/day/ac, the result is about 0.01 in/hr. If the interceptor capacity is five times the sanitary flow, it has a capacity of 0.04-0.05 in/hr. This means that oftentimes there is insufficient capacity in the interceptor to accommodate runoff for treatment. As a result, a CSS system can be expected to overflow 20-60 times per year. The impact of these overflows on receiving waters is great and includes organic sediment accumulation on the bottom of receiving water bodies, oxygen stress in the overlying waters and increases in nutrients and toxic materials. In addition, sanitary debris and floating trash in the area of are aesthetically unpleasant. Attempts to mitigate CSOs have included screening overflows at discharge points, capturing CSOs using floating booms with hanging curtains in the receiving waters, treatment of overflows using vortex removal devices or sedimentation tanks prior to discharge, and storing overflow in detention tanks, then slowly releasing it into the interceptor after the storm for

A Review of Advanced Sewer System Designs and Technologies 5-1 treatment at the WWTP. Variations on these basic approaches include controlling solids and floatables using baffles, trash racks, screens, netting, sewer flushing, outfall booms, and skimmer boats. Injection of polymer into the sewer, use of hydrobrakes to control flows, use of swirl separators and vortex degritters are also commonly applied. Storage controls include retention basins, use of inflatable dams, use of wirbeldrossel and wirbelvalves, maximizing the in-line storage, use of off-line storage, sedimentation ponds, deep tunnel storage, onsite storage, vertical drop-shaft, and the use of weirs in the collection system. Real Time Automatic Control (RTAC) systems have been used to optimize sewer system performance in Europe, but experience in the U.S. has not been good. Other wet weather control techniques includes routine inspection of the collection system, conducting collection system repair, rehabilitation and replacement of damaged pipes and pump station units or any other damaged components within the collection systems, and reduction and retardation of inflows.

Figure 5-1. Typical Combined Sewer System Design Layout. Diagram prepared by L. Roesner

For source controls in CSS, the following techniques have be implemented within a watershed: waste reduction and recycling, street cleaning, catchment basin maintenance, controlling the use of and pesticides within the catchment, erosion and sedimentation control through structural and non-structural techniques, public education, product restriction, banning or substitution, controlling the illegal dumping of solids and chemicals into the catchment, bulk refuse disposal, implementing hazardous waste collection programs, introduction of water conservation programs, implementation of commercial and industrial pollutant discharge prevention.

5-2

CSO supplementary or “satellite” treatment techniques are used worldwide to minimize the impact of CSO discharge into receiving waterbodies. The CSO wastewater that overflows at the regulator is diverted to a small treatment facility and treated before being discharged into the receiving waters. The CSO supplementary treatment may involve complete treatment or a partial treatment process. CSO established treatment techniques include the use of chlorine disinfection (chlorine gas, sodium hypochlorite, and/or calcium hypochlorite) or alternative disinfection such as chlorine dioxide, ozonation, ultraviolent radiation, peracetic acids, and electron beam irradiation. Other established CSO treatment techniques are the use of dissolved air flotation, fine screens and micro strainers, dual media high rate filtration, and biological treatment. Odor control for CSOs is accomplished through the use of wet scrubbers and activated carbon adsorption units. Advantages: If one ignores the public health and environmental impacts of CSO, it is easy to understand why engineers originally designed these systems for cities on the coast and in the Midwest. In the U.S. and around the world most CSS are more than 100 years old which indicates that if the system is well maintained it can last for a very long time. Depending on topography the CSS conveyance network can operate entirely by gravity flow and thus uses minimal energy. These systems provide transport of both stormwater and sanitary sewer water and eliminate the need for constructing two separate wastewater collection systems. Moreover I&I, a very big issue in sanitary sewer systems, is not a problem in CSS. Using one system for both sewer and stormwater reduces the operation costs by minimizing the number of staff required to operate and maintain the system as well as minimizing construction of the infrastructure that is often required in both sanitary separate systems and systems; because there is only one pipe, there is no chance of cross connecting a sanitary sewer line into a storm drain and vice versa. The system uses manholes which are easily accessed for cleaning, repair, and maintenance. CSS transports both solids and liquid from the household and no solids are stored onsite that might require pumping like in septic systems; in most cases no electrical or mechanical parts are required at the household level; the system does not require routine maintenance or inspection at the household level which saves the homeowner from routine maintenance fees often required with alternative sewer systems. The connection fee is lower compared to other wastewater collection systems, and the household pays only one bill for storm drainage and wastewater. Typically, in a CSS, pipes are buried deep to prevent the sewer from contaminating the drinking water supply networks, and rendering them free from freezing. The pipes are of large diameter and are not easily blocked by sediments and solids, and the pipes are made up of high strength materials such as prestressed concrete or reinforced concrete so they are not easily damaged by traffic loadings compared to PVC and plastic pipelines used in alternative sewer systems. The CSS is a very suitable collection system for larger cities compared to alternative sewer collection system because sudden increases in population may not necessarily affect the capacity of the CSS. When combined with wet weather control, structural and non-structural, programs, existing CSS can provide a very reliable sewer collection system without expansion of the facilities for many years to come. Maintenance and repair work in most cases does not require the system or the collection line to be taken out of service as is often the case in alternative collection sewer systems. Since wastewater is in constant motion septic conditions resulting in formation of odorous and toxic gases are minimized. Stormwater pollution to receiving waters is reduced if a city operates a CSS since both sanitary sewer and stormwater will be processed by a treatment facility or plant before release.

A Review of Advanced Sewer System Designs and Technologies 5-3 Disadvantages: The major problem in CSS is CSOs, which can become a source of health concern and environmental degradation in areas served by CSS. Wastewater treatment plant facilities must be designed to accommodate sanitary sewage as well as wet weather flows. Aging CSS infrastructure is a big problem in the U.S. since most of the CSS where constructed in 19th or early 20th century and they now require rehabilitation and partial replacement, but most municipalities do not have sufficient funds to replace them and therefore only repair, and rehabilitate, failing sewers; however, this is probably not a sustainable practice. Application: In the U.S. alone, about 772 communities, or approximately 40 million people, are served by CSS. Most of the communities served by this system are located in the New England and regions as well as in the (Figure 5-2). [247]

Figure 5-2. Locations with CSS in the United States. Figure from U.S. EPA

5.2 Proven Designs and Technologies for CSS Providing knowledge and techniques for control of CSOs and solids accumulation in CSS has been an ongoing process. Many engineers, researchers and vendor companies have developed different designs and technologies to address CSOs and solids control in CSS. Designs and technologies listed here have been in use at different places around the world but are not considered common because only a few utilities have adopted them. Detailed descriptions of these proven technologies are presented in the following paragraphs. The use of green infrastructure technologies is a fast growing CSO control technique that has been in application around the world for a few decades. The idea is to control surface water runoff from a rain event before it enters the CSS. This approach minimizes the quantity of stormwater that is allowed to enter the conveyance system. Green infrastructure technologies include the use of Low Impact Development (LID) techniques and Best Management Practices (BMPs) that capture, treat and then direct the water to surface waters, or they capture the stormwater and release it at a slow enough rate that CSOs are avoided in the system. The BMPs and LID techniques include the use of retention basins, detention basin, green roofs, vegetative swales, rain gardens, bioretention cells, pervious pavement, rain barrels, green filters, rainwater harvesting techniques and aquifer recharge from stormwater runoffs. Optimizing sewer design and operation through the use of computational software is a fast growing field in practice. Optimization techniques include the use of generic algorithms and

5-4 quadratic programming. Generic algorithms predict sequences that minimize CSO volume for 3 hour rainfall events over a hypothetical sewer system. [111] Quadratic programming is used to optimize system design cost, pipe slopes, size, and pipe buried depths. Use of this approach enables thorough understanding of the capacity of the sewer system for new designs and also for the assessment of an existing sewer’s capacity. [134] Optimizing sewer designs and operation can lead to reduction of CSOs by directing more flow to larger pipes during a storm or redirecting runoff to a portion of the system where it is not raining, thus providing temporary storage and preventing small pipes from surcharge. Use of computer simulation models for sewer design and operation assessment is another growing field. In recent decades many software packages have been developed include the SWMM5, XP-SWMM, WinSLAMM, EXTRAN, among others. These computer models are used to simplify the complex municipal sewer network into a manageable network model that can predict the real condition that is happening in the actual network. Using computer models, the capacity of the CSS can be well assessed and measures can be taken to control CSO problems. The use of advanced sewer system operation control techniques is another growing area for better improvement in CSS performance and control of CSO. These include the use of Real Time Automatic Control (RTAC) techniques, Supervisory Control and Data Acquisition (SCADA), use of neural optimal control algorithms, GPS, remote sensing technologies, and GIS technology to present the variation of CSO in space and time. Other CSO control techniques include the use of cross flow microfiltration, high gradient magnetic separator, chemically enhanced high rate sedimentation, continuous deflecting screens, fuzzy filters, ultraviolent irradiation, high rate disinfection, and powdered activated carbon-alum coagulant unit. Modification techniques on the CSO tank are used to direct more concentrated sewage to the treatment plant and allow less concentrated sewer to flow above the regulator at the CSO tank. Techniques used are fluidsep-German design, Grit King design, Storm King, end of weir settling pond, high side weir chamber, U.S. Swirl regulator, Hydrodynamic separator, and a bottom slot outlet. Advantages: LID techniques and BMPs, if well designed, can substantially reduce the amount of entering the CSS and hence minimize CSO volume/frequency. These technologies also reduce the amount of flow to the municipal treatment plants and reduce energy consumption and other operational costs. LID techniques and BMPs also remove sediments that could otherwise enter into the CSS and can cause settling that may result in sewer blockage. Removal of sediments also minimizes the concentration of pollutants carried by the runoff into the receiving water bodies (i.e., zinc, mercury, copper, gasoline, sulfur, and lead). Rain water harvesting can reduce the demand for treated municipal water used for irrigation hence preserve source waters. Rainwater harvested in these BMP and LID practices can also be used for toilet flushing, car washing and other non-potable uses. LID and BMPs remove nutrients (nitrate, nitrogen, and phosphorus) in surface runoff which would otherwise enter receiving waters. LID and BMPs provide a more environmentally friendly solution to urban water runoff, and may reduce urban flooding problems. LID and BMPs increase surface runoff travel time and hence reduce the peak flow in streams and nearby rivers thereby reducing stream bed and bank erosion. Green roofs reduce roof runoff and provide thermal insulation to buildings in warm climates. Green infrastructure may provide a medium for plant growth and habitat for animals.

A Review of Advanced Sewer System Designs and Technologies 5-5 Other advantages of proven CSO control are the use of optimization design techniques to provide maximum utilization of CSS storage capabilities in the existing system and hence reduce CSO events, computer models can help to optimize the operation of CSS and hence reduce CSO. Application of Real Time Control allows the CSS operator to observe events at real time and conduct necessary operation procedures to control CSOs. Disadvantages: BMPs requires large open surface area which may not be available in developed urban environment. Using the CSS pipeline as a storage area promotes settling of solids in the pipeline that could cause pipe blockage and sewage septicity, accelerating corrosion in concrete pipes and causing odor problems. Buying, installing, and operating new equipment and components in the CSS to control CSOs will add extra cost to municipalities. BMP and LID may require large capital investment which may not always be available. Operational devices in CSS will need skilled individuals to operate the system to insure proper operation practices. 5.3 Experimental and Foreign CSS Designs and Technologies Experimental and foreign technologies include the use of high speed fiber filters (developed in Japan) and a first flush tank (developed in Spain lab experiments); use of inverted traps (a sediment removal technique applied in UK, Scotland, and France), and other experimental technologies including the use of CSO satellite treatment technologies which use an enhanced physical process with remote monitoring; use of in sewer sediment traps; weather radar for CSO monitoring and control; use of street surface storage, use of micro and macro BMP retrofits; use of decentralized wireless sensor networks; use of virtual rain gauges; embedded sensor network technology, and use of feed-forward-back propagation artificial neural networks. Other foreign and experimental technologies include the use of first flush pipe type in line CSO tank developed in German, use of SPIRIT 21 developed in Japan for debris removal, high rate filtration, coagulation/separation, and measurement/control disinfection, use of inline circular CSO regulator tank and offline rectangular CSO tanks considered as German model for CSO control, other techniques includes the use of self-regulating movable weir for CSO control, use of horizontal fine screen for removing gross solids in CSO (German) design, use of rotating drum sieve at CSO regulator tank location a German model, use of pre-fabricated polyethylene vortex separator a German design, use of front weir with varying crest (France) model, use movable weir at CSO tank for flow regulation, use of ring shaped floating plastic net media a Japan model, use of cross flow ceramic membrane microfiltration, and use of metering in CSS. 5.4 Separate Sanitary Sewer (SSS) System Design and Technology The SSS system is the most used sewer collection system design in U.S. and around the world. SSS system designs collect and transport only sanitary wastewater to the treatment or disposal site. No stormwater is carried by SSS system. A city served by SSS will need to have a separate stormwater collection and treatment or disposal system. Depending on topography, SSS collection systems are designed to operate under gravity. Pump and lift stations may be required in areas where topography is prohibitive. If possible, SSS collection systems should be designed to flow under gravity force entirely as this will minimize operation and energy costs. The SSS system can overflow due to system capacity exceedance during wet weather, which increases infiltration and inflow into the SSS system. SSS can also overflow due to system blockage, system mechanical failure and structural failure (Figure 5-3). The SSS system overflow is called Sanitary Sewer Overflows (SSO). Pipe blockage is the main cause of SSO with 43% occurrence and infiltration and inflow is the second cause of SSO with 27% occurrence. Pipe break and

5-6 power failure cause SSO with 12% and 11% occurrence, respectively. Insufficient system capacity is the last cause of SSO with 7% occurrence. [283]

Figure 5-3. SSO Occurrence by Cause. Figure from U.S. EPA[283]

U.S. EPA’s report to congress in 2004 estimated that 23,000-75,000 SSOs occur each year in the U.S. alone, which results in 3-10 billion gallons of untreated wastewater discharged into the U.S. receiving waters. [247] 5.4.1 Established SSS Designs and Technologies The SSS system collects seweage from residential, commercial, industrial and public institutions and conveys the sanitary wastewater to a treatment facility or disposal site. Only sewage is carried by this system. The stormwater is collected by a separate system (Figure 5-4). SSS systems collect and convey sewage under gravity force with the exception of low laying areas that require a lift pump station to pump the sewage to higher collection mains. The minimum pipe size that collects water from residential sites is typically 15cm (6 inches) and for commercial and industrial sites minimum pipe size is about 20cm (8 inches). The minimum slope of the pipeline is 0.005 m/m or ft/ft for 15cm (6inches) pipe and 0.0012 for 45cm (18 inches) pipe. All sewers are designed for a minimum scour velocity (usually 0.61m/s (2ft/s) at peak flow) to provide solids transport and prevent settling. Maximum design flow velocity should not exceed 3.03m/s (10ft/s) while the depth of sewer mains with service laterals should not exceed 4.55m (15ft). Maximum spacing of manholes is 151m (500ft) for straight lines and 60.6-121m (200-400ft) for curved sections (City of Roseville Design standards, 2010).

A Review of Advanced Sewer System Designs and Technologies 5-7

Figure 5-4. Separate Sanitary Sewer System (SSS) Configuration. Diagram prepared by J. Bergdolt and M. Hollowed

SSO problems in SSS are controlled using different techniques compared to CSOs. These include increasing system capacity, implementing proactive operation and maintenance programs, conducting system condition assessment, and implementing repair, replacement, and rehabilitation (RRR) programs. Operation and maintenance programs are used to correct pipe problems and pump station mechanical problems. These may include sewer cleaning or flushing, cutting and removing roots, FOG removal and bioremediation of FOG inside the pipe and at the pump stations. Condition assessment techniques provide information about the nature and cause of SSOs. Condition assessment is achieved through the use of Closed Circuit Television (CCTV), sewer scanner, and sonar technology. Condition assessment may provide useful information on the structural and hydraulic condition of the pipe interior (such as pipe cracks, solids and sediments accumulation, pipe breaks, missing pieces, sags, displaced pipe joints, and illegal connections) and address the degree of infiltration and inflow into the SSS. Other established condition assessment techniques include visual inspection, smoke testing, aerial monitoring, manhole inspection, private property (sewer laterals) inspection, soil moisture and temperature monitoring, and monitoring of surface settling. Repair of pipe or pipeline may include replacement of pipe or pipe section, rehabilitation of the collection system to control excessive I&I, increasing collection system capacity, and providing structural integrity of the system. RRR techniques may include simple joint and crack filling, spot repair, or they may include more advanced techniques such as cured in place pipe (CIPP), internal pipe lining, spot repair using chemical grouting, manhole rehabilitation through surface coating, crack sealing and chimney repair. Advantages: This system minimizes wet-weather flow conveyed to the WWTP, there is no intentional release of raw sewage to receiving water bodies as is the case of CSS, stormwater is collected and conveyed by a separate system, and smaller pipe and appurtenances are used in SSS compared to CSS.

5-8

Disadvantages: As the population expands the sewer system will need to expand also. This system can easily surcharge with minor blockage compared to CSS. In addition, two collection and conveyance systems will be required for the sewerage and stormwater, which increases the investment and operation costs to the city. 5.4.2 Proven Design and Technologies in SSS To deal with SSOs, some of the CSO control techniques can be adopted. The proven techniques used in SSO control includes wet weather structural controls such as storage of excess flows at key locations in the system until the WWTP has the capacity to treat them. Nonstructural control measures include the use of green infrastructures to control wet weather flows. These may include the establishment of LID and BMPs in the watershed to control the stormwater runoff so that it has minimal opportunity to enter the SSS. The BMPs and LID techniques include the use of retention basins, detention basins, green roofs, previous pavement, and vegetative swales. Green infrastructure technologies are used to minimize the surface runoff that may enter the manholes or infiltrate into the pipe through groundwater. Other CSO control techniques used in SSO control are floatable controls (baffles, screens, and trash racks) to provide good flow of stormwater and prevent local flooding in the watershed that can eventually flow into the sewer manholes. Application of computer models for design and operation of SSS is a being increasingly used. Hydraulic characteristics of a municipal SSS collection system can be evaluated and results obtained from the model can be used to find the best solutions for the challenges faced by a SSS collection system. Examples of available software are XP-SWMM, EPASWMM, and MACRO models, etc. Model results obtained from the hydraulic analysis model can provide information about the capacity of the SSS, the available storage, areas of high flows and low flows, surcharge problems, and other hydraulic condition of the sewer system. The use of software during the design of new sewers can help the municipal to optimize the system performance and minimize the capital cost, and energy cost. Other proven technologies implemented by municipalities around the world for sewer flow monitoring include the use of Supervisory Control and Data Acquisition (SCADA) system, application of GIS and GPS technologies for sewer mapping and information organization in databases. To control SSOs municipalities and service providers are implementing different tools including structural oriented and managerial approaches. At the pump stations techniques being implemented include provision of additional storage in case of excessive inflow, provision of standby pumps and generators, installation of alarm systems, and bypass facilities from the pumping station to off-line storage facilities. Other technical approaches includes expanding the sewer trunks, removing blockage in the pipeline by rodding, eliminating cross connections, and conducting sewer repair, replacement and rehabilitation programs. On the managerial side the utilities are implementing collection system capacity management, operation, and maintenance (CMOM) approach, conducting public outreach on FOG control at the source, and setting regulations on illegal stormwater discharge into the SSS. To deal with the odor problems the following techniques are applied: the use of aeration and oxygenation which includes air injection, venture aspirators, air lift pumps, pressure tank air ejection and hydraulic fall injection at the pump station. Other odor control technique includes the use of chemical oxidation using chloride gas, sodium hypochlorite, sodium chlorite,

A Review of Advanced Sewer System Designs and Technologies 5-9 magnesium hydroxide, and hydrogen peroxide. Use of sulfur precipitation is another technique to control odor in SSS which includes the use of iron coagulated sludge in sewers and potassium ferrate. Another technique is pH adjustment which involves the pH stabilization through caustic shock loading, biological treatment, bioaugumentation and application of enzyme treatment. 5.4.3 Experimental and Foreign Technologies Hydrogen sulfide formation in sanitary sewers has been a source of odor and cause of corrosion to concrete pipes and other concrete structural components used in SSS. Advanced techniques used to control hydrogen sulfide formation include the application of nitrate, use of microbial fuel cells (MFC) and the use of novel inhibitors. Odor control techniques in SSS include the use of chemical scrubbers, activated carbon absorbers, biofilters, biological scrubbers, ionization systems, hydroxyl fog, cold plasma, and photocatalystic reactors. Another area of innovation in SSS system has been on fat, oil, and grease (FOG) control. Techniques implemented to control FOG include the use of mechanical removal techniques, use of chemicals, bioremediation, de-greasers, use of enzyme additives, use of grease interceptors, automatic grease traps, and passive grease traps.

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CHAPTER 6.0

TECHNIQUES FOR INFILTRATION DETECTION AND CONTROL

6.1 Conventional Techniques for Infiltration Detection and Control Infiltration in sewer collection system occurs when groundwater intrudes into the sewer collection system through defective joints, broken pipelines, pipe fractures, fractured manhole walls, fractured septic tanks, fractured pump station storage tanks, and fractured groundwater storage tanks (Figure 6-1). Infiltration in sewer collection systems is influenced by the groundwater level, annual rainfall over the area, previous construction techniques, soil type, etc.[76] Sewer conveyance system components can be damaged or fractured, due to tree root intrusion, aging of the sewer lines, corrosion, ground settlement, earthquakes, ground excavation, traffic loading, loading from nearby buildings, etc.[86] Infiltration of groundwater into the sewer conveyance system can significantly increase the quantity of sewer water reaching the disposal site or the treatment plant. Infiltration water can cause excessive discharges through the pipeline which can exceed the design capacity of the sewer system and hence cause SSOs (Figure 6-2).

Figure 6-1. Infiltration Sources. Reprinted with permission from King County, Washington[284]

A Review of Advanced Sewer System Designs and Technologies 6-1

The quality of wastewater carried by the pipeline can be altered depending on the quality of water infiltrating the conveyance system. Groundwater may contain toxic compounds, and industrial contaminants that may result in very different chemical characteristics compared to the domestic sewer water. These contaminants may complicate the process. Increased sewer water from infiltration will require larger disposal or treatment facilities; it will also limit the design life of the sewer collection systems.

Figure 6-2. Heavy Groundwater Infiltration in Sewer Pipeline. Reprinted with Permission from Niagara Region[288]

To control the infiltration of groundwater into the sewer collection systems, different control techniques can be implemented depending on the physical condition of the sewer collection system. A sewer system may require repair, rehabilitation or a complete replacement. To determine the condition of the collection system, a sewer condition assessment will be required. Condition assessment will determine the level of repair and/or rehabilitation that will be required. This condition assessment can also determine if the economic life of the sewer collection system has been reached and if a completely new system is required. Sewer collection system inspection is part of condition assessment procedure. Conventional sewer inspection can be conducted by using dye test, air testing, smoke testing, hydrostatic testing and visual inspection for leakage or intrusion location detection. Different techniques are used to reduce infiltration of groundwater into the sewer system, including repair and rehabilitation of the sewer collection system. This may include fixing the defective pipe joints, sealing of fractured pipelines, using cement, mortar, grouting or epoxy coating to seal the fractured manholes. To remove and prevent roots from damaging the pipes several conventional methods exist including the use of mechanical methods (i.e., rodding or hydraulic cleaning); use of chemical methods (i.e., injection of acids or solvents, copper sulfate, dicholbenil, diquat dibromide, or herbicides); other techniques involve the use of bio-filters and careful selection of tree species planted near the sewer collection system. If tree roots are not controlled in sewer systems they can clog the pipe and restrict the flow in the sewer. The roots can expand an existing opening, allowing soil to enter the pipe, weakening the structure and ultimately causing the pipe to break or collapse. The roots themselves can change the hydraulic conditions in the

6-2 pipe by creating local flow restrictions. The tree roots act as a filter, restricting the flow of solids and causing blockages that can cause sewer overflows.[86] Excessive growth of roots in the sewer can completely block the flow of sewer through the pipe (Figure 6-3).

Figure 6-3. Root Intrusion. Reprinted with permission from Trenchless Technology of TN [291]

The most effective root control method is to prevent roots from entering the sewer in the first place. This can be achieved by installing watertight lines that will be free of cracks, and resist deterioration, breaks, and structural failures through the economic life of the sewer system. Another method is to avoid planting trees too close to the sewer line. A selection of trees with root systems that will not damage the infrastructure can be implemented but trees with long extending roots should be avoided near sewer lines.

Patriot Root and Grease Cutter (Model WJ-49P)

Reprinted with permission from Sewer Equipment Co of America

Figure 6-4. Root Removal by Root Cutters.[292]

Root removal can be achieved by using a root cutter (Figure 6-4). Soil deposits in a pipe can also be removed by using a long rotating cable or hydroscrubs.[298] 6.2 Advanced Techniques for Infiltration Detection and Control Visual inspection is limited to large sewers that a utility worker can walk through. Many health risks are involved if visual inspection is used. Sewer water may produce hydrogen sulfide which is hazardous to humans. Working inside sewer pipes will increase the exposure of the

A Review of Advanced Sewer System Designs and Technologies 6-3 utility worker to pathogens and viruses in the sewage that can be hazardous to the workers and their families. More advanced techniques can be used in today’s industry that does not require a person to get inside the sewer line. 6.2.1 Infiltration Detection Techniques To locate a leak and infiltration inside a sewer system, the following advanced techniques can be implemented: Closed Circuit Television (CCTV), ground penetrating radar, Radar Tomography (RT), infrared thermography, air pressure testing, water testing, digital camera inspection, laser profiling/3D scan/sonar, Totally Integrated Sonar & CCTV Integrated Technique (TISCIT), wireless monitoring system, smart sewer assessment system, acoustic technologies, electrical and electromagnetic methods, laser profiling, ultrasonic testing system, micro deflection, gamma-gamma logging, impact echo/spectral analysis of surface waves (SASW), sonic distance measurement and rotating sonic clipper. Closed Circuit Television (CCTV) is a common and cost-effective sewer inspection technology that consists of a camera mounted on a moving device that can be stopped to provide more precise information. Commonly used mounting devices to transport the CCTV camera through the line are a crawler, wheeled tractors or floats. A footage meter can be used with the CCTV to keep track of the location of the defects along the pipe. It is now possible to buy a CCTV unit for small diameter sewers for less than $1,500. Limitations of CCTV technology include its ability to capture only images above the sewer water level and it does not provide quantitative dimensions of the pipe dimension, deformation, or the debris level. For larger pipes CCTV units can cost up to $140,000, which may be too expensive for small utilities. Manufacturers of CCTV are the Aeries, Cues, Hydrovideo, IBAK, and Pearpoint. Ground Penetrating Radar (GPR) uses electromagnetic radiation in the microwave band of the radio spectrum and detects the reflected signal from subsurface structures. Ground reflected signals are recorded and anomalies are interpreted to access the location of different features below the ground surface. This method is rarely used for pipe defects assessment. Rather, it is used for locating the lateral or pipeline main in areas where a map does not exist. Sonar Technology uses reflected high frequency sound waves to locate and map discontinuities along the wall of a pipeline. This technology, which uses a sonar head inside the pipe, is capable of providing sewer conditions above and below the wastewater level. The sonar technology has been used to determine the depth of debris and sediments in the sewer. Produced images can be interpreted to detect irregularities in a pipe including cracks and deformations. Manufacturers of Sonar equipment are the Aemtec TISIT, Sonex, and R&R Visual, Inc. Laser or Light Profilers are used to assess dimensional variations along a dry pipeline. A narrow ring of white or laser light is directed at the pipe wall and is viewed by the camera to show the profile of the pipe at any cross section. The image produced can be calibrated to allow accurate on-screen measurement of the pipe bore. Systems used under laser or light profilers are ClearLine manufactured by Cues, CoolVision and Laserline manufactured by Colmatec, and Amtec’s Light manufactured by Amtec. Other technologies, identified in the following section, are not commonly used in the U.S; however, detailed information about them can be found in the sited literature in Table 2-1.

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6.2.2 Infiltration Control Techniques Results from sewer system inspection are used to determine the required repair or rehabilitation procedure that can be used to control the infiltration into the sewer collection system. To control the infiltration, advanced infiltration control techniques are implemented. Rehabilitation and repair techniques used to eliminate the infiltration problem include grouting (to fill the cracks and joint defects), corrosion control techniques such as cathodic protection, application of a polymer slurry to fill the cracks and defects, use of epoxy grouting or patching, mechanical joint seals, flexible liners, fold and form pipe (FFP) or closely fitted liner, and use of the Cured In Place (CIP) technique. These repair and rehabilitation technologies can be used for both private sewer laterals and sewer mains. Epoxy lining has been introduced in water supply pipeline rehabilitation is also proving useful in sewer rehabilitation. Epoxy lining can protect a pipeline from corrosive water and corrosive compounds carried by sewer water. It can also be used to seal pipe joints, manhole cracks, and other sewer collection system components. The life span of the sewer pipe can be increased by protecting it from having direct contact with the sewer water (Figure 6-5).

Figure 6-5. Epoxy Lining. Reprinted with Permission from CuraFlo[293]

6.3 Experimental and Foreign Infiltration Detection and Control Technologies The most common internal sewer system inspection technique is the use of CCTV. The quality of the information collected from traditional CCTV depends on the experience of the technical personnel using the equipment and the reliability of the TV picture. These limitations have pushed the industry to develop more advanced technologies. Some of these technologies have been introduced into the market around the world, but they are still not very commonly used by U.S. utilities. 6.3.1 Infiltration Detection Techniques Advanced technologies include infrared thermography, sonic distance measurement method, and ground penetration radar technique. Other new advanced multi-sensory systems are the KARO and MACRO (developed in Germany), the PIRAT (developed by CSIRO of Australia), and the Sewer Scanner and Evaluation Technology (SSET) which was developed in Japan. Infrared thermography system operation is based on the energy transfer theorem where by energy flows from warmer to cooler areas. The infrared thermography scanner is capable of

A Review of Advanced Sewer System Designs and Technologies 6-5 scanning the entire internal pipe area and provides data on temperature variation within the interior of the pipe. Areas of different temperatures are displayed with different gray color tones on a black and white image, or a symbolic color range is displayed on colored images, depending on the type of the device used. The infrared thermography system consists of the following scanning and analysis components: the infrared scanner head and detector with interchangeable lenses, a real-time microprocessor coupled with a display monitor, the data acquisition and analysis equipment, and various image recording and retrieving devices for visual and thermal images. The testing rate is 3-100 miles of pipeline per day. This method can locate leaks, erosion voids, and infiltration cracks. It can be used during the day and night. Disadvantages of this method are it relies on a single sensor for inspection and data collection, it does not provide information about the depth of the cracks and the interpretation of results requires a well-skilled and experienced technician.[175, 176, 179, 203] Sonic distance measurement method involves measurement of the time needed for a blast of sound to travel from the source to the intended target. The time of travel changes as the velocity changes through different mediums. The sonic velocity varies depending on density and elasticity of the transmitting medium. This method is used to inspect plastic pipes, concrete pipes, clay pipes, and brick pipes. It can operate in water and in air, it defines the cross sections of the pipe, measures pipe wall deflections, corrosion loss, volume of debris, and it has a high field production rate. However, this method cannot operate in both air and water at the same time; it also relies on a single sensor for data collection. [175] Ground penetrating radar (GPR) method transmits electromagnetic waves into the ground using antenna. The reflected wave represents the change in electrical properties of the subsurface material at the boundary interface. The GPR records a sewer pipeline’s structure condition, the condition of the surrounding soil, and the condition of sewer pipeline soil interface. Limitations to this method include difficult data interpretation, which requires a highly skilled and experienced individual, and an incomplete picture of the sewer from results due to the reliance of GPR on one mode of data collection. [175] Foreign experimental techniques using KARO, PIRAT, and SSET (multi-sensory systems) provide more reliable data, a continuous profile of pipe walls; the systems have a robot module, and they have a high long term benefit-cost ratio. Shortcomings of these technologies are: they are still considered to be in the testing stage (prototype) and they require further development before field implementation. These technologies are considered expensive or have high initial cost. The KARO innovation is based on the 3D optical sensor, ultrasonic sensor, and microwave sensor. This technology applies a sensor fusion based fuzzy-logic system for conducting pipe inspection. The KARO robotic mode is controlled remotely but it contains cable that supplies power and transmits data to the station. The current prototype model is 80cm long, 16cm in diameter and can be operated in 20cm diameter pipe for a distance of 400m in a single pass. The robot is equipped with a color TV camera, 3D optical sensor, and an ultrasonic sensor, as well as a microwave sensor attached to its tail (Figure 6-6). The PIRAT innovation is also based on new qualitative multi-sensor technology. The PIRAT system consists of two semi-independent systems, one is the instrument system which collects the geometry data, the other is the interpretation system that analyzes the geometry data to detect and identify the magnitude of each defect. With its capability, PIRAT is superior to CCTV technology. This system consists of a mobile device that can travel through the pipe

6-6 carrying the scanners and other instruments. The mobile device carries two scanners: a laser scanner for drained pipe inspection and a sonar scanner for full pipe flow. This device weighs about 90kg and can be operated from a distance of 250m. The current PIRAT mobile device uses a cable that supplies power and transmits the collected pipe data. The Sewer Scanner and Evaluation Technology (SSET) uses a robotic system that contains CCTV, video recorder, full circumference scanned image of the entire pipe and gyroscope technology. SSET fixes the deficiencies of the CCTV and provides an image of the total surface of the pipe, from one end to the other end. The SSET requires an external winch to propel the device through the pipeline. The main benefit of the SSET is that field work is significantly decreased; the high quality data produced during the field inspection allows the engineer to assess the defect at a later time.

Figure 6-6. Optical and Sensor Equipment in the KARO Robot. Figure from WERF[203]

Other New Foreign Technologies for gravity sewer inspection includes the Radiax Vector Orphée from France, Triscan and Panoramo from Germany, ClearLine from New Zealand, Cool Vision from Canada, ISAAC from the European Union, Sonar Profiler from the UK, Focus Electrode Leak Locator from Germany (developed by a Seba Dynotronic and Mess-und Ortungstechnik GmbH), Coolvision Laser Inspection manufactured by Colmetec of Canada, Digital Scanning and Evaluation Technology (DSET) from Japan (produced by OYO Corporation), Wave Impedance Probe developed by Rock Solid Research Pty. Ltd, and Professor James Philip Cull of Monash University in Australia, and Amtec’s Sonar Inspection

A Review of Advanced Sewer System Designs and Technologies 6-7 manufactured by Amtec.[203] A description of the functionality and limitations of a few of the listed foreign inspection technologies are presented below. Radiax Vector Orphée (RVO) is an innovative technology from France, initially introduced in 1993, with the capability of combining the digital CCTV with laser scanning/profiling capabilities to provide more digital data such as the inclination of the pipe line, size of a crack or defect, and real time visual imaging of the pipe interior. The RVO can conduct inspection on sewer pipes of 150-1200 mm (6-48 inches) in diameter. The system can operate using the CCTV mode or the combined CCTV/Laser scanning mode. The laser scanner provides the ability to measure the size of the defect directly on the pipe. Advantages of RVO includes ease of use, it can be used with the analysis software package Orphée to create a report for the client, closer measurement can quantify the depth and width of the cracks to one millimeter accuracy and the laser also provides pipe circumference measurements. The instrument is equipped with an inclinometer that is capable of providing the pipe profile and detection of sinks or rises along the pipe. No person is required to enter the sewer pipeline to launch the RVO, and gravity flow sewer lines can be in service during the inspection. Disadvantages of RVO are that pressure sewer section needs to be removed during inspection time, a water depth greater than 8 cm (3 inches) will obscures the lens, wheel slippage can hinder the movement of the machine inside PVC and PE pipes and it is limited to sewers of 150-1200 mm (6-48 inches) diameter; image clarity is reduced for pipes greater than 1200 mm (48 inches). A well-trained and experienced operator is also needed. Cost: Purchase price in 2004 was $76,100 for the RVO unit and $1945 for the software license fee. [203] Panoramo technology was introduced in 2002 and a production model was released in 2003 by IBAK Helmut Hunger GmbH, a German company. The Panoramo system consists of a 3D optical scanner with the capability of producing a pair of linked images, one looking forward and one looking backward, providing a 360° image of the pipeline. It produces a full pan/tilt image of every point along the line with a moving camera which makes the inspection much quicker compared to CCTV. A unit is normally connected to the vehicle that provides power and transmits the digital data captured by the cameras to a computer installed inside the service vehicle to provide real time data (Figure 6-8). The Panoramo system can operate in a sewer with a diameter of 200-2000 mm (8-80 inches). The digital view of the pipe interior is provided in a full 360° pan allowing for close inspection of different types of defects including joints failure, cracks, structural failure, pipe corrosion, etc.

6-8

Figure 6-7. Panoramo Unit System. Figure from WERF[203]

Advantages: Panoramo provides a clear 360° digital image of the whole length of the pipeline between manholes, it can operate in gravity sewer without interrupting the sewer service, the pipe interior condition inspection and measurement of the defect size is provided on the image. Disadvantages: Pressure sewers must be taken off-line during inspection, wheel slippage can hinder the movement of the unit through new PVC and PE pipes, and it is only suitable for circular pipe inspection; for non-circular pipes, the produced image is distorted. Training is required for operation of Panoramo. Cost: Purchase price of the Panoramo unit, in 2004, was $275,000, and there is no license fee for the software, however operator training for three days is about $4600. Digital Scanning and Evaluation Technology (DSET) was originally used in the oil and gas industry to scan the borehole. In 1990, OYO Corporation developed the first DSET unit. The DSET model was later improved by Blackhawk PAS with high resolution image capabilities and a software package that allows the user to enter code defects, identify the extent of a defect, and produce a report. The DSET model is used for sewer pipes with a diameter of 6-54 inches to detect cracks, misalignments, root intrusion, infiltration, debris, and pipe corrosion (Figure 6-8).

A Review of Advanced Sewer System Designs and Technologies 6-9

Figure 6-8. A View of Digital Scanning Elevation Technology (DSET). Figure from WERF[203]

Advantages: The DSET model is equipped with an inclinometer and gyroscope to determine x-y- z coordinates along the pipe segment, evaluate pipe grades, alignment, and points of potential sewer overflows. The DSET model can detect defects more accurately than the CCTV. The DSET digital data are easy to retrieve, easy to acquire and compatible with GIS and other computerized data storage software packages. Disadvantages: For pipes with a diameter greater than 54 inches, the image clarity and resolution is reduced, cleaning of the pipe before inspection is required, and the tractor is limited to a cable length of 900 inches. The digitally scanned image cannot be used to determine pipe ovality or deformation; the DSET is not suitable for ductile irons and HDPE pipes due to the black background pipe color that limits the view of pipe defects, and a highly experienced person is required to operate the DSET. Cost: The basic cost of a DSET unit in 2004, with no additional devices such as a gyroscope, was $80,000. In addition, the price of the software package was $20,000. Wave Impedance Probe (WIP) is a technology developed by Rock Solid Research Pty. Ltd., and Professor James Phillip Cull of Monash University in Australia (Figure 6-9). This technology is used for nonmetallic pipes such as bricks, clay, concrete, and plastic. The WIP detects anomalies in the soil surrounding the pipe. The WIP device can detect and map the voids, caverns, varying degrees of consolidation, and soil saturation. The principle functionality of WIP is based on the electromagnetic field or eddy current.

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Figure 6-9. Wave Impedance Probe (WIP) Unit Lowered into the Manhole. Figure from WERF[203]

The WIP can be used in pipes with a diameter of 50-5000 mm (2 inches-16.5 feet), battery life and the length of the cable can limit the application, the pipeline must be clear of larger obstacles, and a highly skilled operator is required. Cost: The cost of basic equipment and license is $25,000. 6.3.2 Inflow Reduction Technologies Inflow to sanitary sewer pipes originates from rainfall water that enters the sewer pipe through point sources. These point sources can be the opening in manholes cover, cross connections of leaking stormwater sewer, leaking manhole chimney, roof drain connections into the sanitary sewer, direct connection of sump pumps into the sanitary sewer, and foundation or basement drains connected directly into the sanitary sewer. Control of inflow can be achieved by sealing manhole covers, removal of roof drains, and disconnection of sump pumps from , disconnecting stormwater infiltration pumps, cross connection elimination, and replacing cleanout caps. Inflow identification techniques generally include monitoring flow through the pipe by isolating the pipeline at night and conducting flow measurement, conducting pipe lateral and main inspection, and reviewing operation and maintenance records. The inflow inspection techniques are similar to infiltration inspection techniques.

A Review of Advanced Sewer System Designs and Technologies 6-11 6.4 Sediments and Solids Control Techniques in Sewer Collection System Sediments and solids accumulation in sewer collection systems are considered to be one of the main source of sewer blockage that cause sewer overflows. In the UK, the required combined sewer design self-cleansing velocity during a two-year storm event is 1m/s (3.3ft/s). This self-cleansing velocity is achieved by providing a minimum pipe gradient of 1/N, where N is the nominal pipe diameter. If a sewer system is well designed and constructed to maintain the required self-cleansing velocity, sediment accumulation problems will be minimized. However, large solids that may have been accidentally or intentionally introduced into the sewer system from domestic or other sources will have an increased chance of initiating sewer blockage problems. The self-cleansing velocity used during design of a sewer system does not consider the sediment concentration. It has been suggested in literature that design based on a critical shear stress of 1-4 N/m2 would provide better results and prevent sewer blockages. [255] Other design techniques used to minimize sediment and solids accumulation is the provision of adequate pipe capacity, and provision of obtuse angles at pipe junctions to allow a smooth transition of flow and sediments. Conventional techniques for sediment and solids removal in sewer systems include the use of mechanical cleaning techniques such as the use of power rodding devices, pigging, power buckets, and silt traps. Another conventional technique used is hydraulic cleaning which involves the use of jetting, balling, kites, scooters, and flushing. Jetting involves the application of high pressure water at the deposition site; balling involves the insertion of a rubber ball with a diameter slightly smaller than the pipe interior, creating an increased flow, equal to the scouring velocity, around the rubber ball; kites involves the use of a cone like device, which functions similarly to balling; scooter comprises a metal shield attached to a self-propelled wheeled framework. The flushing technique involves introduction of large volume of water into the sewer capable of removing floatables and loose debris to the downstream of the pipeline. Chemical grouting is another conventional method used to remove roots and FOG that may have accumulated inside the pipeline. Chemical grouting involves the use of herbicides for root removal and enzyme additives for FOG break up and control of odors in the sewer system. [247] Advanced sediment removal techniques involve the use of Hydrass® (a French innovation), Hydroself® (a German innovation), Biogest vacuum flushing and U.S. EPA’s Automatic vacuum flushing system. Hydrass® uses a hinged gate with the same cross section as the sewer it serves. This technology works by building up a volume of water behind the gate at low flows until the force is great enough to turn up the gate. The sudden release of high flows cleans sediments and solids that may have accumulated downstream of the gate (Figure 6-10).

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Figure 6-10. The Sequence of Hydrass® Sewer Flushing Gate in Operation. Figure from U.S. EPA[240]

Hydroself® technology was first introduced by Steinhardt Wassertechnik in 1986 for cleaning a tank in Bad Marieberg in Frankfurt, German. However, its popularity has increase in recent years with the most applications in Germany and Switzerland. Around Europe, this system has been installed in more than 284 locations with over 600 units in operation. The Hydroself® system consists of a hydraulically operated flap gate, a flush water storage area created by construction of a concrete wall section, a float or pump to supply the hydraulic pressure and valves controlled by either a float system or an electronic control panel. The actual installation is site dependent. This system is designed to operate automatically; when the water level in the storage area unit reaches a designed level, the valve is activated and releases a wave of fast moving water that cleans sediments and debris downstream of the gates.[240] Biogest® Vacuum Flushing system consists of a concrete storage basin, a diaphragm valve, level switches, control panel and a vacuum pump system. Water level in the storage unit increases to a pre-defined level to activate the vacuum pump which automatically activates the diaphragm valve and releases a flush wave of water to clean sediments and debris downstream of the sewer pipeline.[240] U.S. EPA’s Automatic Vacuum Flushing System is an innovative technology developed by U.S. EPA in 2003. This system consists of a storage reservoir installed in line with the sewer system; the system also comprises an air release valve, an ingress-egress port, and an air intake conduit. The system is designed in such a way that as water accumulates inside the storage reservoir the air valve releases all the air. When the reservoir is full the air valve closes and the water release gate opens, as water starts to discharge out of the reservoir a vacuum condition is created inside the reservoir. The vacuum increases as water slowly drains out of the storage reservoir to a pre-determined level. When that level is reached, air is drawn into the reservoir via the air intake conduit, which breaks the vacuum condition inside the storage reservoir. When this happens, water in the reservoir is suddenly released through the outlet port to downstream of the sewer system and cleans sediments and debris. [240]

A Review of Advanced Sewer System Designs and Technologies 6-13

6-14

CHAPTER 7.0

SEWER CONSTRUCTION/REHABILITATION TECHNOLOGIES TO CONTROL I&I AND SSOS

7.1 Established Sewer Repair, Rehabilitation, and Replacement Technologies New sewer lines are constructed to provide service to developing areas or to replace existing sewer lines that have exceeded their economical service life or have been damaged. Sewer rehabilitation can be conducted in deteriorated systems to restore them to the required level of service. Rehabilitation can be conducted specifically to minimize infiltration and inflow, to remove root intrusion, to control sewer leakages, to improve structural strength of the sewer line, to improve hydraulic characteristics of the sewer flow, to eliminate CSOs and SSOs, to control air pollution, to control corrosion and to increase the life span of the existing sewer. For many years sewer construction, repair, rehabilitation, and replacement were done through open cut methods. This involves removal of the soil that covers the pipe using mobile excavation equipment and manual labor. The technology is suitable in areas where surface obstacles and underground infrastructure are not an issue. However, in today’s urban areas open cut excavation methods are becoming impractical due to the inconvenience it creates for nearby residents or businesses and the risk of damage to other buried infrastructure such as water mains, communication cables, power lines, gas lines, and other service lines. Maintenance and rehabilitation of buried infrastructure creates a unique challenge because their condition is not known until failure occurs. Utilities around the world are implementing different buried pipe condition assessment techniques to determine the service condition of their buried sewer infrastructure and assess the need for repair, rehabilitation, and replacement. To repair or rehabilitate a pipeline from its exterior, an open cut excavation method can be used in areas where ground and surface infrastructure are not an issue to access the buried pipe. However, for large diameter pipes, repair or rehabilitation in areas where open-cut excavation is prohibitive, maintenance can be conducted without excavation. Conventional internal pipe repair and rehabilitation methods include the use of pipe interior coating techniques such as the use of cement, mortar, resin, epoxy, shortcrete, polyester, silicon, urethane, or vinylester coating. The coating process can be performed manually by humans entering the pipe or it can be conducted by mobile devices that can travel through the pipe and perform the coating process. Depending on the degree of pipe deterioration, pipe replacement may be required. Under conventional pipe replacement we will only consider the excavation and replacement method. Other pipe replacement methods such as trenchless technology will be discussed later under the advanced pipe construction and replacement section. Pipe replacement through excavation is performed if a pipe or a section of a pipe is severely damaged (i.e., a pipe piece is missing, section of the pipe has collapsed, or there is a large longitudinal pipe fracture) and repair or rehabilitation will not restore the service capabilities of the pipe. [179] Application of conventional coating to the pipe interior will require selection of a material that can create a good bond between the coating material and the interior of the pipe. Durability of the coating material to the corrosive nature of sewer water needs to be taken into

A Review of Advanced Sewer System Designs and Technologies 7-1 consideration to avoid premature failure of the coating material. Descriptions of three common coating techniques are presented in the following paragraphs. Cement mortar involves the application of a mixture of cement and mortar to seal the defective parts and improve the structural integrity of the concrete, steel or iron pipes. Advantages of this method are that it can increase the life span of the pipe by as much as 30-50 years, it is applicable to a range of pipe diameters, it is cost effective, does not require highly skilled workers, and a large area of the pipe length can be repaired or rehabilitated in a short period of time. Disadvantages of this method include limited application when pipes have too many bends, if the area experiences very low temperatures or extreme temperature variations. Reinforced gunite is a method that involves application of mixture of cement, sand, and water applied under pressure to the defective area. This method is used to repair and rehabilitate brick sewers. It is also considered a cost-effective method, however, this method is limited to large pipe diameters that can allow human entry, it can only be performed when the pipe line is taken out of service, and a highly skilled worker with good experience is required to achieve the best results. Resin coating method is a non-solvent hybrid polyurethane resin or epoxy that can be used if a pipe interior is suffering from corrosion or erosion. This coating performs well in concrete and steel pipes. The major limiting factor of this method is that it is not suitable for materials other than concrete or steel. [179] 7.2 Proven Advanced Sewer Rehabilitation/Construction Technologies Challenges resulting from the use of open cut excavation in urban areas have forced the sewer construction and rehabilitation industry to consider advanced methods such as the use of trenchless pipe construction and rehabilitation techniques. For well-developed urban areas trenchless technology can offer several advantages such as minimizing disruption of other services in the area, avoiding surface obstacles, minimizing traffic disruption, and reducing the amount of surface reinstatement required after completion of excavation. Also, it is more cost effective than open cut excavation in most cases. It allows for deeper installation of pipeline, which may be too expensive if the open cut method was used, and it is a more environmentally friendly technology as it minimize environmental disturbance. The most common trenchless technologies adopted by the industry today include: sliplining, cured-in-place-pipe, fold and form lining, spirally wound pipe, segment lining, online replacement, chemical grouting, flood grouting, slug grouting, and robotic repair. Other trenchless technologies used in the industry are horizontal directional drilling (HDD), auger boring, pipe jacking, pipe ramming, pipe bursting, and poured in place concrete lining. To determine which method will be most cost effective, an engineering analysis needs to be conducted, considering the capital and operation cost, pipe size, pipe length, existing pipe condition, gravity versus pressure flow conditions, degree and volume of the rehabilitation required, access conditions, right of way restrictions, soil conditions, groundwater conditions, site location, traffic conditions, environmental impact, social and economic impacts, and availability of qualifying contractors. [203] Description of some of the proven advanced sewer rehabilitation technologies are presented below. For more detailed descriptions of and additional information on other mentioned technologies in this report the reader is advised to read the sited literature. Sliplining technique involves placing a flexible liner pipe, slightly smaller in diameter than the existing pipe, inside the damaged section of the sewer pipeline. The most commonly

7-2 used materials for sliplining are HDPE, PVC, polymer concrete, and fiberglass-reinforced plastic pipes (FRP). The new pipe is inserted inside the existing pipeline through a manhole by using a device that can push or pull a short or a continuous pipe segment into the existing pipeline. Pulling machines can be used to accomplish this goal (Figure 7-1).

Figure 7-1. Sliplining Technique. Figure from WERF[203]

The existing pipe must be cleaned and repaired to insure durability of the newly repaired pipe before the sliplining procedure is conducted. The advantages of this method are: it is a quick insertion method, it can accommodate pipe bends, there is minimal disruption to services, different pipe diameters can be rehabilitated by selecting the appropriate pipe size that will fit tightly to the existing pipe (common range of pipe diameters where sliplining is applied is 8-366 cm), and it can significantly increase the lifespan of the existing sewer line. Disadvantages include: it can only be applied in circular cross section pipes, tight curves and bends create difficulties during installation, the new pipe material can be damaged during the installation, large pipe diameters may require grouting for temporary support during sliplining, it reduces the existing pipe’s interior diameter, and the new pipeline may involve labor intensive jointing work. [179][203] Cured-in-Place-Pipe (CIPP) this technique is performed by inserting a resin-impregnated felt tube into the existing pipe line. The tube is placed against the wall of the existing pipe and allowed to cure. Once cured it provides a protective layer to the interior of the pipe (Figure 7-2). The lining is inserted through manholes. Common materials used for CIPP are polyester, epoxy, and vinylester. This method is more suitable to repair pipes located under existing structures or busy streets where disruption of traffic should be minimized. This method is applicable for pipes of 10-175 cm in diameter. The cost of rehabilitation using this method is about 50-70% of the replacement cost. It provides a long term repair, no excavation is required, access to private property is not required, it provides structural repair, and can rehabilitate deep pipelines which would be expensive if other methods were used. This method has been successfully used in Boston, Massachusetts. Disadvantages: It requires that the pipe surface be clean to provide proper adhesion, it does not protect the pipe from root problems, pipes connecting to the main line need to be repaired separately, it is not suitable for pipes with large offset joints or many bends or if the pipe is highly corroded; it reduces pipe size, and it cannot upsize pipes or removal sags.

A Review of Advanced Sewer System Designs and Technologies 7-3

Figure 7-2. Cured in Place procedure. Figure from U.S. EPA[294]

Fold and Form techniques involve the insertion of a folded polymer liner into the existing pipe and expanding it using pressure, heat, or mechanical means to match the pipes original interior shape (Figure 7-3). Common material used for this method includes PVC and HDPE.

Figure 7-3. Fold and Form Technique. Figure from WERF[203]

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Before installation of the folded liner the pipe must be scraped and cleaned of any deposits or debris. All existing pipe lateral connections need to be located. The procedure involves placing a folded liner inside the existing pipe. Steam is fed into the folded liner to soften the liner and allow for reforming. After the liner is well heated, pressure is applied to force the polymer liner to expand and conform to the existing pipe walls. Pressures of 170-240 kPa (25-35 lb/in2) are used. Instead of using a polymer liner, a plasticized PVC pipe can be used with the same procedure. This method can reduce the problem of infiltration and leakage, and increase the life span of the pipeline. It is easy to install, no access pit is required and it conforms well to the shape of the existing pipe. Limitations of this method include a tendency of trapping water and debris between the outside of the expanding pipe and the interior wall of the host pipe, the pipe needs to be taken out of service for some time to allow the new liner to stabilize, it is difficult to install if the pipe has many bends, it reduces the internal diameter of the host pipe, it is relatively expensive, and specialized equipment is required for the installation. [193] Chemical Grouting involves the application of chemical grout, under pressure, into the joint, crack or surrounding soil. The grout seals off pipeline joints, cracks in manhole walls, and leaking pipes or other structures within the sewer collection system (Figure 7-4). Chemical grouting is commonly used in materials such as precast concrete, bricks and clay.

Figure 7-4. Chemical Grouting to Seal the Manhole. Figure from U.S. EPA[113]

Chemical grouting is the most cost-effective method for sewer rehabilitation when the pipeline is structurally sound. Common types of chemical grouting material include acrylamide, acrylic and acrylate, urethane grout, and urethane foams. However, these materials are susceptible to shrinkage and cracking. [179] Advantages of this method include elimination of groundwater infiltration, control of root problems, and no excavation is required. This method is inexpensive, and there is minimal disturbance to the environment. Limitations of this method include no additional structural enhancement to the existing sewer pipe or structure, grouts may form cracks under some groundwater conditions, toxic chemicals are used in this method, and the life span of the grouting is 5-25 years. [113]

A Review of Advanced Sewer System Designs and Technologies 7-5 Flood Grouting Method involves injection of two different chemical solutions consecutively into an isolated section of the sewer line to cause flooding. The chemical solution exfiltrates through the defects in the pipeline, or manholes, into the soil where it chemically reacts with soil particles to form a watertight, sandstone-like silicate (Figure 7-5). This method is used to seal manholes, mainlines, and laterals, simultaneously. The pipe must be cleaned prior to the procedure. Plugs are installed to seal a small section of the system and the first chemical solution is applied, filling the isolated section; then the chemical is pumped out and a jet of water is applied to clean the sewer line. A second chemical solution is then applied and allowed to exfiltrate into the soil, similar to the first chemical. The two chemicals mix in the soil and react with the soil particles. The second chemical solution is then pumped out and the sewer is again flushed with water. [113]

Figure 7-5. Flood Grouting. Figure from U.S. EPA[113]

Advantages: No excavation is required, it eliminates infiltration in an entire section of both the mainline and laterals, it minimizes root problems, it is applicable to all types of pipe materials, sizes and shapes, it is less disruptive to traffic and other services, and the chemicals used are environmentally friendly. Disadvantages: The sewer line needs to be taken out of service for at least a day during the rehabilitation, it does not provide structural enhancement, no pipe diameter upsizing is possible, and chemicals are hazardous if spilled or splashed on the skin or in the eyes. The technology has been successfully applied in the U.S, Europe, and Australia. In the U.S, Sanipor® offers a flood grouting system. In Europe, this flood grouting system is offered by Tubogel®, and Geochemie Sanierungssysteme GmbH offers this service in Germany. 7.2.1 Trenchless Technologies Horizontal Directional Drilling (HDD) involves the use of a horizontal boring bit which drills a hole horizontally from the inlet pit to the exit pit. At the exit pit, the drilling bit is replaced by a reamer which is connected to the utility pipe string and pulled back through the borehole while enlarging the boring hole by 120-150% (Figure 7-6). If a polyethylene pipe material is used, the joints are fused together through heat to create a fusion joint that is stronger than the pipe material. The operator determines the progress of the drilling bit by using a hand held tracking devise. The tracking device gathers data from the sonde located in the drill head just behind the drilling bit. Data gathered by the sonde includes the location, depth, roll angle, pitch, and temperature which assist the driller in adjusting the direction of the bit and controlling

7-6 the bore path. This method was developed in the early 70s by Titan Construction of Sacramento, California. It has been used in the oil, gas, electricity, and telecommunication industries. [276] Today, this method has found application in the sewer industry and has been used in the U.S, Europe, and Asia. In , by 2008, there were more than 200 contractors involved in HDD using more than 2000 horizontal directional drilling machines. This technology was used to install a 406 mm diameter pipe 1688 m across the famous Yangtze River in China in 2002. [196] Advantages: No major excavation is required, equipment requires a relatively short time to set up, labor requirements are minimal, surface disruption is minimized, and there is little disruption to homes and businesses. The method is cost effective for drilling under rivers, busy highways, rail tracks or an active runway, and there is minimum risk of damage to other underground infrastructures. [276]

Figure 7-6. Horizontal Directional Drilling. Figure by M. Hollowed

Disadvantages: A skilled operator is required to conduct the drilling, a drilling machine is required which may require high initial capital investment, the technology is not suitable for deep pipe installation, and a proper site investigation is required before using this technology to avoid damaging any existing infrastructure. Pipe Ramming is a method used to install steel casing under roads, highways, rail bends, and other structures using a ramming tool (Figure 7-7). It is a cost-effective method compared to open cut method. Advantages: It is a trenchless technique, soil is not removed until the casing is installed, it minimizes voids across the road and railways, and reduces soil compaction. Disadvantages: It is difficult to use in some soils such as free flowing sand, cobble, large rock formations, and when there is excessive groundwater.

A Review of Advanced Sewer System Designs and Technologies 7-7

Figure 7-7. Pipe Ramming. Figure by M. Hollowed

Auger Boring Method is similar to the pipe ramming method. The auger boring method uses an auger boring machine to drill a hole through the ground as the casing is installed[276] . This was the first trenchless technology used by construction companies. The auger is rotated using one or two power sources. The torque exerted by the auger, which varies by machine size, is 1000-170,000ft-lbs of torque. The diameter of the machine is determined by the largest casing the unit can push, however, the machine can push smaller casing by using adapter kits. Diameters of bore casings start at six inches and increase in size, depending on the size needed for the project. An auger boring machine can drill in different soil types including clays, sand, shale, and even rock by installing a special bit. Advantages and disadvantages of this method are similar to pipe ramming with the exception that auger boring machines can drill in almost any type of soil. Pipe Bursting Technique involves the use of a cone-shaped tool (bursting head) which is forced through an existing pipe, fracturing the pipe into small pieces which are forced into the surrounding soil. The pipe cavity is expanded to allow a simultaneously pulling of a new replacement pipe (Figure 7-8). The most common material used in replacement is HDPE. [198]

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Figure 7-8. Pipe Bursting Technique. Figure from WERF[198]

There are two main types of pipe bursting methods, static pull and pneumatic bursting. Static pull uses a bursting head that has no moving internal parts but it is pulled through the old pipe by a powerful device and is commonly used for replacing ductile pipes such as lead, galvanized iron, and cast iron. Pneumatic busting uses repeated impact of the bursting head with a cone shaped soil displacement hammer driven by compressed air. The main advantage of static pull over the pneumatic bursting is the ability of static pull to get through curves and angles. Advantages: New pipe is installed, replacing the old pipe without major excavation, no cleaning or root removal is required, infiltration problems are controlled, and increasing the pipe size is possible. It can eliminate minor sags and root problems, there is minimal disruption to the environment, and no chemicals are used. Disadvantages: Pits are required during pipe bursting; it is difficult to operate in hard clay ground, or in high groundwater areas. It is not suitable for pipelines with many sharp curves and bends, and there is a risk of damaging objects when bursting in shallow ground. [198] Microtunneling uses a microtunneling boring machine (MTBM) which drills a hole through the soil using the cutting head to remove the ground in front of the MTBM. [289] The soil is mixed with water to form a fine slurry, which is pumped to the surface; the water is recycled and reused again in the drilling process. As the cutting head removes the soil in front of it, the pipe to be installed is inserted behind the MTBM and everything is jacked forward under hydraulic pressure.The MTBM is capable of drilling through very soft silts, hard clay, gravel, and cobble. Microtunneling is suitable in soils where other trenchless technologies such as auger boring cannot operate effectively. Microtunneling can install pipe with internal diameters of 250-3000mm (24-90 inches) over distances of up to 300 meters in one drive. This method can be used to install different types of materials including reinforced concrete, steel, fiberglass, polymer concrete, clay, and ductile iron. Advantages: It is remotely operated, no open excavation is required, environmental impact is minimized, and it is highly accurate. It is designed for a variety of soils; it is cost effective, and it

A Review of Advanced Sewer System Designs and Technologies 7-9 can be used in areas where the water table is high. The excavation rate depends on soil type, and proper inspection is required after pipe installation to insure joint integrity. Disadvantages: It can be stopped by a large quantity of cobble or large rock, it requires site preparation before installation, and it requires a skilled operator. 7.3 Experimental and Foreign Technologies in Sewer Construction and Rehabilitation Robotic rehabilitation technique involves the use of mortar (resin) or special epoxy to rehabilitate damaged pipe spots or joints between laterals and the mainline. The resin cures into a material similar to the host pipe and it becomes part of the original pipe. [198] The robotic sewer repair system originated in Switzerland in the early 1980s. It is able to repair pipe made up of different materials such as concrete, reinforced concrete, fiber-reinforced cement, and clay. It can perform repairs such as removal of protruding laterals (Figure 7-9), recessed laterals, cracks, laterally displaced joints, and root intrusions. [179]

Figure 7-9. Robotic Repair of Sewer Joint. Figure from WERF[198]

Laboratory experiments in Reze, France have shown that the robotic method can bring the pipe back to a watertight state and cure infiltration problems. Robotic repair methods have been used in Europe, Australia, and the Far East. Currently in the U.S, there are two companies that manufacture the robotic system; the Janssen Process, LLC, originally from Germany, manufactures the Janssen Lateral Rehab System, and SAF-r-DIG Utility Surveys, Inc, originally from Switzerland, manufactures the KA-TE robotic system. The cost per connection for repair depends on the degree of preparation required, and the quantity and type of resin used. The cost ranges from $1000-1500 for KA-TE system and is about $2000 per connection for the Janssen system. [198]

Figure 7-10. Lateral Connection Before, During and After Robotic Repair. The protruding pipe joint was ground and resin was applied. Figure from WERF[198]

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Advantages: No excavation is required, the method provides structural repair with no reduction of pipe nominal diameter, and infiltration and root problems are eliminated. This method provides a cost-effective solution to sewer rehabilitation, it has minimal environmental impact, no noise, minimal traffic interference, and it is a very suitable method for repairing protruding laterals (Figure 7-10). Disadvantages: A skilled, experienced operator is required to perform the rehabilitation, specific condition assessment is required for the proper selection of robotic rehabilitation technology, and the method is not economical for extensively damaged pipes. The pipe section under repair must be taken out of service during repair, and chemicals used (resins) are hazardous to human skin or eyes. Vacuum Assisted Resin Transfer Molding (VARTM) is a method of rehabilitating sewers that uses E-glass fiber fabric and unsaturated polyester resin with vacuum assisted resin transfer molding. The internal pipe diameter range that can be rehabilitated by this method is 150-1000 mm and the length of pipeline can be up to 50 m.

Figure 7-11. Pipe Rehabilitation Process using VARTM. Reprinted with permissions from Elsevier Science, Ltd[194]

A Review of Advanced Sewer System Designs and Technologies 7-11 To conduct the VARTM process the pipeline section under rehabilitation will need to be cleaned and after cleaning a wire is placed through the pipe section by a mobile robot (Figure 7-11a). The wire is used to install the reinforcing element by using a winding machine (Figure 7-11b). The adhesive material is coated on the outer part of the reinforcing element, but during installation the material is still fresh and slippery to allow it to be dragged through the pipe section under rehabilitation. After the reinforcing element is installed at its correct location, both ends of the pipe are sealed (Figure 7-11c). After sealing, compressed air or nitrogen gas is supplied inside the reinforcement to expand the inner protection layer. This compressed air forces the outer part of the reinforcement element to attach to the interior of the pipeline (Figure 7-11d). The air pressure is then removed and a predetermined amount of unsaturated polyester resin is injected into the fiber using a RTM machine (Figure 7-11e). After injection of the resin, compressed air or nitrogen gas is pumped again into the pipeline to attach the reinforcement element, the fiber, and the existing pipe interior together. Then a vacuum is applied simultaneously at the outer part of the reinforcement cover to remove any air that may have been entrapped during installation (Figure 7-11f). To accelerate the curing time the air inside the cavity is maintained and a device is used to increase the temperature inside the cavity. After the resin is cured, the covers on both ends of the pipeline are removed and the air is released and the rehabilitation process is completed. [194] Advantages: It is suitable for pipelines located under roads with high traffic, it is possible to extend the range of materials used in the rehabilitation, there is a possibility of cost savings, it save time for rehabilitation, it prevent infiltration, increases the lifespan of the pipeline, and it increases the structural strength of the pipeline. Disadvantages: This technology is very new and it is still in the experimental stage, several different pieces of installation equipment are required which may increase the capital cost of the equipment; also, a skilled operator is required to perform the rehabilitation process.

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CHAPTER 8.0

PIPE MATERIALS AND JOINTS FOR SEWER SYSTEMS DESIGNS

The history of using pipes to collect and transport wastewater dates back to ancient times. Common materials used in sewer collection systems include clay, concrete, cast iron, ductile iron, steel, and asbestos cement. New pipe materials that are gaining more application in sewer collection system are PVC, PE, and glass-reinforced plastics (GRP). Pipe materials that are new, but used less in sewer collection systems are glass-reinforced concrete (GRC), polypropylene (PP), acrylonitrile butadine styrene (ABS), polymer concrete, and composite pipes (concrete- PVC, GRP-polymer concrete, and concrete-ceramic pipes). Established pipe materials used for sewer pipe manufacturing are discussed in the next section. Descriptions of the most commonly applied new pipe materials and joints in sewer systems will be presented in the following sections. 8.1 Established Sewer Pipe Materials Clay, concrete, and cast and ductile iron are the most common pipe materials used to collect and transport sewage to the treatment plant or to the disposal site. Clay pipe is the oldest material that was used for water supply and sewer collection. It is reported that 4000 years ago clay pipe was used to supply water and collect wastewater at the Palace of Knosso in Crete. Concrete sewer pipes were used around 800 B.C. at Cloaca Maxima in Rome to collect and transport sewer to the disposal site. [63] Asbestos pipes have been used to collect and transport sewer in the past, however, due to health concerns, installation of asbestos pipe in new sewer collection systems has been abandoned in most countries around the world, including the U.S. Clay pipes There are two main types of clay pipes: the normal clay pipe, and vitrified clay pipe. Normal clay pipe is manufactured by mixing clay with water. The mix is poured into a mold and a pipe is formed. The pipe is then heated to a high temperature to create a rigid clay pipe. Vitrified clay pipe are made up of one-third clay and two thirds shale ground together then mixed with water in a pug mill. Vacuum is used to remove air and then the mix is subjected to high pressure to form the required pipe shape. The formed pipe is then heated at 1,100°C to create a rigid vitrified clay pipe. Vitrified clay pipe is available in nominal diameter ranging from 100 mm-1,400mm (4 to 56 inches) in lengths ranging between 300mm-3000mm (1-10 ft.). Advantages of vitrified clay pipe: They are available in variety of nominal pipe diameters, they have been in use for many years, their longevity is great, they are chemically inert material and thus not affected by internal or external corrosion; they have high abrasion resistance, and have a very high compressive strength. Disadvantages: They are heavy and brittle, so they can get damaged during transportation and during installation if hit by a hard object, old clay pipe had problems of leaking joints, they have a short segment length, low tensile strength, and they cannot be used for pressurized flow. Concrete pipes There are two main types of concrete pipes: non-reinforced concrete and reinforced concrete pipe. Cement that can be used in concrete sewer construction is divided into

A Review of Advanced Sewer System Designs and Technologies 8-1 five types: normal Portland cement, modified Portland cement, early-cured Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement. Non-reinforced concrete pipes are manufactured by mixing cement, sand, and aggregates. Non-reinforced concrete pipe range in size between 100-900 mm (4-36 inches), with a standard length of 2.5 meters (8 feet). Reinforced concrete pipe is manufactured in three types: prestressed concrete cylinder pipe (PCCP), reinforced concrete cylinder pipe, and bar wrapped steel-cylinder concrete pipe. The load bearing capacity of reinforced concrete is 1,500-22,500 lbs/lineal ft and they can withstand pressures up to 55 psi. Concrete pipes are rigid with high compressible strength. Due to their ability to withstand earth loads and live loads, concrete pipes have been widely used in the U.S. for collecting and transporting sewer water to the disposal or treatment site, they are available in a variety of different diameters and lengths, and they can be installed by open cut or pipe jacking methods. Disadvantages: There is a possibility of deterioration on the inside of the pipe due to the presence of acid, sulfate, and biological activities inside the sewer that can cut short its service life. Septic sewage can produce hydrogen sulfide (H2S) which is oxidized by bacterial to produce sulfuric acid (H2SO4) which is the main cause of internal corrosion in concrete pipe. To prevent internal corrosion concrete pipes are lined with a corrosion resistance layer. Concrete pipes are heavy, they can easily crack if installed in hot soils or corrosive soils, and they have low tensile strength. [63] Iron pipe Cast iron, ductile iron, and steel pipe are the main types of iron pipe. Cast iron and ductile iron have been commonly used in sewer systems. Ductile iron replaced cast iron in the late 1940s and has been used commercially since 1955. Ductile iron requires internal coating to protect direct contact of the iron with the corrosive sewer water. In the past, materials such as bituminous coal, tar, or asphalt were used to coat the interior and exterior of the pipe. In 1922, cement mortar lining for ductile iron was introduced. Since then most of the ductile iron pipes used in the water industry are coated with cement mortar or bituminous liners, to prevent direct contact of the sewer water with the interior of the pipe. Ductile iron is considered a flexible pipe material which has been used for both gravity and pressure sewer system. Ductile iron is manufactured by mixing scrap iron with magnesium. The pipe is available in nominal diameters ranging from 75-1600mm (3-64 inches) and varying lengths. It is manufactured to withstand pressure between 150 and 350 psi. Advantages of ductile iron: Can be used for both pressure and gravity sewer collection systems, they are available at different nominal diameter and lengths, have high beam strength, high impact strength, high load bearing strength, they are considered flexible pipes, and different liners can be applied. Disadvantages: Vulnerable to corrosive water and environment; they are expensive compared to other pipe materials, and they are heavy. [63] 8.2 Innovative Proven Pipe Materials and Joints New developments and innovations in clay, concrete, and iron pipes have been reported. Emphasis has been given to improving concrete and iron pipe to withstand corrosion and on how to improve the pipe joints so as they can be used in trenchless technologies. Innovations addressing joints are discussed below. For concrete pipes, available joints now include the bell and spigot, tongue and groove, modified tongue and groove, use of combined lip and

8-2 compression seal, and application of silica-fume (micro-silica) as an additive to improve the quality and robustness of the concrete pipe and joints. For PVC pipes, the joints available include the use of polyester and O-ring joints, the use of No-bell joints, fiberglass-reinforced polyester bells, and use of jacking coupling. For ductile iron different types of liners are used to control internal and external corrosion; these include bituminous, cement mortar, calcium aluminates, cement polyethylene, polyurethane coal tar epoxy, use of ceramic epoxy, cement epoxy, and thermoplastic coal. To improve the quality of the pipe and joints the following techniques are used: manufacturing of ductile iron jacking pipes; use of polyethylene encasement, bonded coating, field welded joints, and use of ductile iron push pipe. [63] On the other hand, plastic materials have been introduced into the sewer industry and are gaining more application than ever before in the U.S. Plastic materials have been in use for sewer collection systems in Europe for many years. Common plastic materials that are in use for sewer collection systems and rehabilitation are PVC, PE and GRP. Other plastic materials used in the sewer industry but with less regularity are PP, ABS, and polymer concrete. Development and innovations in plastic materials over the past 20 years have allowed plastic pipe materials to be used for both gravity and pressure sewer collection systems. Polyvinyl chloride (PVC) pipe is manufactured through polymerization of vinyl chloride monomer in a suspension process. Different compounds are mixed with the polymer which may include stabilizers, lubricants, fillers, and pigments. With the application of heat, shear force, and pressure a homogeneous mass of PVC pipe is formed. The commonly manufactured PVC pipe has a nominal diameter of 100-400 mm (4-16 inches), with length of 6 m (20ft), they use bell and spigot joints and elastomeric ring, the frictional coefficient (Manning’s n ) of PVC is 0.008-0.01, and PVC pipe soften at 80°C. Polyethylene (PE) pipes are manufactured in three common types: high density polyethylene (HDPE), medium density polyethylene (MDPE), and low density polyethylene (LDPE). These pipes are manufactured by mixing pre-compounded granules of polymer antioxidants, pigments, and ultraviolet stabilizers. The mix is heated to produce well mixed melt which is processed under pressure to produce the PE pipe. The density range between LDPE and HDPE is between 0.910 T/m3 (56.8 lb/cu.ft) and 0.959 T/m3 (59.8 lb/cu.ft). PE pipe strength ranges between 8 MPa (1160 psi) and 10 MPa (1450 psi). Common diameters for PE are 12- 1500 mm (0.5-60 inches). They have a Hazen-Williams friction factor (C) of 155 and Manning’s n of 0.008-0.01. They use different types of joints including butt-fusion welding, electrofusion welding, and bell and spigot joint with a sealing gasket. They come in various lengths with the small diameter that can be produced on a coil or a role. Glass-reinforced plastic (GRP) are manufactured using either centrifugal casting or the filament winding. Centrifugal casting involves feeding in layers of liquid thermosetting resin, chopped glass fibers, and aggregates into a horizontal mold rotating at low speed. The speed is then increased and centrifugal force compresses the material layers against the outer casing to form a well dense pipe wall. The layers are heated together to form a GRP pipe. Filament winding produces GRP pipe by winding tensioned glass fiber around a rotating mandrel and adding a thermosetting resin directly to the rotating mandrel to form a pipe that can be continuously formed and cut to the required length. GRP pipe is available from 25-3600mm (1-144 inches). Resins are applied to improve the pipe resistance to corrosive water or environments. These resins include polyester, vinylester, and epoxy. The pipe is available at different lengths depending on customer needs. Different types of joints are available including

A Review of Advanced Sewer System Designs and Technologies 8-3 the fiber-wound collar coupling, low-profile bell and spigot, pressure relining, flush bell and spigot, and closure coupling. They can handle pressure up to 17 bars (250 psi). The Hazen William C value is between 145 and 155, and Manning’s n value is between 0.008 and 0.01. [63] Advantages: Plastic pipes are light weight, easy to handle and install, high resistance to corrosive sewer water and environment, flexible joints, easy to bend for small diameters, less friction to sewage flow, good abrasion resistance, low cost, low leakage at the joints, low microbiological activity growth inside the pipe. They are easy to replace during rehabilitation, they have low maintenance cost, and are available in different diameters and lengths. Disadvantages: There is a risk of large plastic pipes floating on high water tables, they have low compressibility strength compared to other materials, difficult to locate compared to metal pipe, the quality varies a substantially even from the same manufacturer. In addition, they have a very short history of application in sewers compared to other materials such as concrete and clay. Some plastic pipe are degraded by been exposed to UV radiation, plastics can be permeable to certain contaminants, and they can be corroded if placed under high acidic conditions. 8.3 Experimental and Foreign Pipe Materials and Joints Improvement and innovations in materials used for pipes and joints manufacturing is a fast growing industry around the world. The driving forces is the idea of producing durable pipes made up of durable material, developing material resistant to corrosive nature of the sewer water and the surrounding soils, developing lightweight pipes with high bearing load capacity, and developing pipe and joints that can be installed using trenchless technologies. Advanced experimental and foreign techniques that are new to the sewer collection system design industry includes the use of PVC alloys, manufacturing of molecular oriented PVC, use of recycled PVC material, use of electro fusion welding, manufacturing of high pressure PE pipe, cross linked PE (PEX), manufacturing of circular and semi-elliptical liner polymer concrete pipes, in-situ PEX liner, and closed wall PVC pipe forms with in-wall joints. Innovations are also taking place with conventional pipe materials such as clay, concrete, and iron pipes. PVC pipes can now be installed using microtunneling technology. The diameters installed with this method range between 30-90cm (12-36 inches). They are designed with stainless steel sleeve with elastomeric seals for the joints and have a minimum compressive strength of 7,000 psi. Flush joints are now used for the VCP pipes when they are installed using auger boring, and pipe bursting trenchless technologies. Successful projects have been conducted in the U.S, German, and UK. Development in concrete pipes has resulted in better quality concrete pipes through the application of additives to the concrete mix such as micro-silica. The American Ductile Iron Pipe Company has developed a bell-less ductile iron with a pressure push pipe joint developed by counter boring the plain ends of adjacent pipes and installing independent internal couplings. This pipe is available in diameters between 100 and 600 mm (4- 24 inches) and length of 19.5 feet. [63] Compared to other pipe materials more innovations and development has been conducted on plastic pipes in the past 10 years. They include improvement of existing plastic pipe products and introduction of new pipe types in the industry. These innovations have resulted in plastic pipes finding application in gravity sewers, pressure sewers, and in the communication, power, and chemical industries. Descriptions of some of the innovations and improvements that have taken place in the plastic industry are presented below.

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PVC alloys are manufactured by mixing PVC polymer with elastomeric additives such as chlorinated polyethylene (CPE), ethylene copolymer resin or mixing all the two additives with the PVC polymer. The pipe produced has a higher strength than a regular PVC and thinner pipe wall which makes it more portable for transport and installation. Since this material is new, information about its performance under different conditions is not well known. Molecular Oriented PVC pipe is manufactured by placing a pipe length in a long mold up against the bore of the mold to allow the PVC molecules to be reoriented to lay parallel in a hoop or loop direction. Another procedure for producing this type of pipe is by pulling the pipe over a conical die which increases the pipe diameter, decreases wall thickness, and orients the PVC molecules in the hoop direction. This process produces high strength PVC pipes almost as twice as strong as regular PVC, and the new pipe can withstand high deformation loads. The molecular oriented PVC is still new in the market since it was introduced in 1998, so data and information about its performance is limited. A known limitation is that the production cost is higher than the manufacturing of regular PVC pipe. Recycled PVC reuses PVC pipes after their service life ends, by blending the old PVC with new PVC polymer to produce a new pipe. Currently manufacturers do not recycle the old PVC to produce new pipes. This has been a concern to many environmental organizations. This idea is still new to the industry and it is still in trial production. High-pressure PE (PE100) is a new PE pipe that has found application in the gas and water distribution industry. Its introduction to sewer water collection system still needs more investigation. The reason is the cost of production of PE100 which is almost 20% higher than the regular PE pipes, which hinders its application in sewage systems. Use of other PE or PVC pipe material for sewer collection will provide the same service level as the PE100, but some application might be found in pressure sewer system due to its better strength. Cross Linked PE (PEX) is a new pipe material that provides a better pipe than the PE80 or PE100. It has more heat stability as it operate well at temperature beyond 100°C as well as at low temperatures. It has high abrasion resistance, provides long-term strength, and has high resistance to chemical attack. It has some limitations too. The cost of production is higher compared to other PE pipes, only electro-fusion can be used for pipe joints, and PEX cannot be recycled. [63] 8.4 Synthesis of the Pipe Materials and Joints in Sewer Collection System Design For many years, pipes manufactured by using traditional materials such as clay, concrete, and iron have provided service to the sewer collection system industry and contributed significantly to human civilization. As customer expectation increases and new laws and regulation are introduced. The existing material has faced challenges to improve its performance and in some cases they have been forced out of service and been replaced by other pipe materials such as plastics. Over the years, significant improvements have been made on the performance traditional materials including improvement to pipe joints, and design and installation to prevent leakage, root intrusion, and groundwater infiltration. This innovation also extends to manufacturing with experimentation with the material used in pipe production. Through experiments manufactures have been able to improve the quality of the pipe produced by increasing the pipe load bearing strength, minimizing corrosion effects, limiting chemical attacks, and increasing pipe durability. In today’s industry traditional materials are still most commonly used and their application will continue as more and more innovations are introduced to make them better and adapt them with new pipe installation technologies such as pipe jacking

A Review of Advanced Sewer System Designs and Technologies 8-5 and micro tunneling. Innovations in traditional pipe materials have made them part of cutting edge technologies such as the installation of traditional pipes using trenchless technologies. Despite of the great achievement in traditional material improvement, challenges still exist. The main problem that still hinders the traditional pipe material from achieving its full potential is the heavy weight of the pipes products. The weight of the pipes and its accessories make them difficult to transport and to install; as a result they add cost to the utility when they opt for using traditional pipe materials. Reduction in weight of the finished pipe product, manufactured using traditional material such as clay, concrete, and iron is considered to be an area that needs more research and development. New thinking about pipe design around the world has offered an opportunity for improvement on traditional materials and provides alternative solution for sewer collection system designs. New materials have also provided solution to traditional sewer pipe material limitations. Plastic pipes in large have been able to capture the imagination of the industry by providing light weight pipe products that are easily to transport and install. Plastic materials provide a cost effective method for pressure sewer system development and operation compared to traditional material. Plastic pipes joints are more effective at preventing groundwater infiltration, sewer leaks, and root intrusion as they provide a water tight joint. Plastic pipes are more resistive to corrosion compared to traditional materials. Plastic materials also provide low friction to the flowing wastewater as a result they minimize blockage within the sewer line and prevent CSOs or SSOs. However, challenges exist on these new pipe materials. Plastic pipes are still considered new to the sewer industry. Their long-term performance has not yet been established. Plastic pipes can easily be damaged by impact loads and traffic loads, large diameter plastic pipe face risk of flotation in high ground water tables, the quality of pipe product still varies, and no external observer is in charge of examining their performance to prove or disapprove their high quality as claimed by pipe manufacturers. More research is required from independent researchers on pipe product quality through experimental testing.

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212. Kreissl, J.F., Kuhn, P.A., Vaughan, R.D., and a Technical Advisory Committee (1981) Design and Specification Guidelines for Low Pressure Sewer Systems, Florida Administrative Code, State of Florida—Department of Environmental Regulation.

213. Fuss and O’Neill (2008) Bolton Lake Sewer Project: Low Pressure Sewers and Grinder Pumps, Town of Bolton, CT. www.blrwpca.com.

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215. AIRVAC (2007) Vacuum Sewers: Components, Operation, and Advantages, Government Engineering. www.govengr.com.

216. NSFC (1996) Alternative Sewers: A Good Option for Many Communities, Pipeline, Fall 1996, Vol. 7, No. 4, NSFC, Alexandria, VA.

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218. Otterpohl, R., Braun, U., and Oldenburg, M. (2002) Innovative Technologies for Decentralized Wastewater Management in Urban and Per- Urban Areas, International Water Association (IWA) 5th Specialized Conference on Small Water and Wastewater Treatment Systems, Istanbul, Turkey. www.iwahq.org.

219. NSFC (2000) Alternative Toilets: Options for Conservation and Septic Site Conditions, Pipeline, Summer 2000. Vol. 11, No. 3, NSFC, Alexandria, VA. www.nesc.wvu.edu.

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223. Vipulanandan, C. and Gurkan Ozgurel H. (2004) Methods to Control Leaks in Sewer Collection Systems, CIGMAT, University of Houston.

224. Simmons, J.D. and Newman, J.O. (1985) Small-Diameter, Variable Grade Gravity Sewer, WEF, Journal of Water Pollution Control Federation Vol. 57, No. 11, pp 1074- 1077. www.jstor.org/stable/25042792.

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226. Delta Environmental Products, Inc. (2005) Installation and Service Manual with Parts List. 2- Horsepower Centrifugal Grinder Pump for Residential and Pressure Sewer Applications, Pentair Water. www.deltaenvironmental.com.

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227. Delta Environmental Products, Inc. (2005) Pump Installation and Service Manual: Submersible Semi-Positive Displacement Grinder Pump, Pentair Water. www.deltaenvironmental.com.

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229. Delta Environmental Products, Inc. (2009) Installation and Service Manual: Low Pressure Sewage System, Pentair Water. www.deltaenvironmental.com.

230. Hydromatic® (2009) Pump Installation and Service Manual: Advanced Submersible Grinder Pump, Pentair Water. www.hydromatic.com.

231. Hydromatic® (2009) Commercial, Residential, Resort Area: Submersible Sewer Grinder Pump, Pentair Water. www.hydromatic.com.

232. Hydromatic® (2007) Pump and Installation Service Manual: Submersible Grinder Pump, Pentair Water. www.hydromatic.com.

233. Decatur Professional Development, LLC (2008) Vacuum Sewer: Design and Installation Guidelines, PDHengineer Course No. C-8015, Reprinted with permission from WEF, Alexandria, VA. www.PDHengineer.com.

234. Jones, D., Bauer, J., Wise, R., and Dunn, A. (2001) Small Community Wastewater Cluster Systems, Purdue University Cooperative Extension Service. www.agcom.purdue.edu/AgCom/Pubs.

235. NSFC (1997) Lagoons Systems Can Provide Low Cost Wastewater Treatment, Pipeline, Spring 1997, Vol. 8, No.2, NSFC, Alexandria, VA. www.nsfc.wvu.edu.

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239. Black and Veatch Corporation (2004) Sanitary Sewer Overflow Solutions: Guidance Manual, America Society of Civil Engineers, EPA Cooperative Agreement No. 828955- 01-0.

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241. Decatur Professional Development, LLC (2007) Vacuum Sewer 101: Alternative Sewer System, PDHengineer Course No. C-4028, www.PDHengineer.com, WEF, Alexandria, VA.

242. U.S. EPA (2007) The Long-Term Control Plan-EZ (LTCP-EZ) Template: A Planning Tool for CSO Control in Small Communities, Report No. EPA-833-R-07-005, U.S. EPA Office of Water, Washington, D.C.

243. U.S. EPA (1995) Combined Sewer Overflows: Guidance for Nine Minimum Controls, Report No. EPA-832-B-95-003, U.S. EPA Office of Water, Washington, D.C.

244. U.S. EPA (1999) Combined Sewer Overflow Management Fact Sheet: Sewer Separation, Report No. EPA 832-F-99-041, U.S. EPA Office of Water, Washington, D.C.

245. Fortdiani, R. (2006) CSO Control Technologies: Omaha CSO Control Program, PowerPoint Presentation, November 9, 2006.

246. U.S. EPA (2002) Evaluation Report – Wastewater Management: Controlling and Abating Combined Sewer Overflows, Report No. 2002-P-00012, Office of Inspector General, U.S. EPA, Washington, D.C.

247. U.S. EPA (2004) Report to Congress: Impact and Control of CSO’s and SSO’s, Report No. EPA 833-R-04-001 U.S. EPA, Washington, D.C.

248. Ruggaber, T. (2007) High Density CSO Monitoring Using an Embedded Sensor Network in South Bend, IN, Emnet, LLC. www.emnet-cso.com.

249. Lukas, A., Merrill, M.S., Palmer, R., and Van Rheenan, N. (2000) In Search of Valid I/I Removal Data: The Holy Grail of Sewer Rehab, WERF Project No. 99-WWF-8. Water Environment Research Foundation, Alexandria, VA.

250. Black and Veatch Corporation (2000) Protocols for Identifying Sanitary Sewer Overflows, America Society of Civil Engineers, EPA Cooperative Agreement # CX 826097-01-0.

251. Carollo Engineers (2003) Sanitary Sewer Master Planning: Comprehensive Solution for Sanitary Sewer Systems, www.corollo.com.

252. Arthur, S., Crow, H., and Pedezert, L. (2008) Understanding blockage formation in Combined Sewer Networks, Proceeding of the Institute of Civil Engineers – Water Management, Vol.161, No.4, p.215-221, ICE Publishing.

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253. Pardee, L.A. (1966) Hydraulic Properties of Pipes, Boxes, and Rectangular Channels: Office Standards No. 116 and 117, Bureau of Engineering, City of Los Angeles Storm Drain Design Division.

254. Pardee, L.A. (1968) Hydraulic Analysis of Junctions: Office Standards No. 115, Bureau of Engineering, City of Los Angeles Storm Drain Design Division.

255. U.S. EPA (2008) Review of Sewer Design Criteria and RDII Prediction Methods, Report No. EPA/600/R-08/010, U.S. EPA, Washington, D.C.

256. Natural Resource Management Ministerial Council (2004) National Water Quality Management Strategy: Guidelines for Sewerage System – Sewerage System Overflows, Australian Water Association, NSW, Australia.

257. Stockton, G.R. (2003) Application and Methodology for Locating Sormwater Discharge using Aerial Infrared Thermography, InfraMation: The Thermographer’s Conference.

258. Tafuri, A.N. and Selvakumar, A. (2002) Water Collection System Infrastructure Research Needs, Report No. EPA/600/JA-02/226, U.S. EPA, Washington, D.C.

259. Decatur Professional Development, LLC (2009) Green Stormwater: Low Impact Design – Managing Stormwater Through Infiltration, PDHengineer Course No. EN – 3009, Reprinted with permission from WEF, Alexandria, VA. www.PDHengineer.com.

260. NSFC (1998) Environmental Technology Initiative Fact Sheet: Composting Toilet System, U.S. EPA Assistance Agreement No. CX824652, NSFC, Alexandria, VA. www.nsfc.wvu.edu.

261. NDP Group (2008) Custom Research Service: Grey water Awareness and Usage Study, Soap and Detergent Association.

262. Gauley, W. and Koeller, J. (2009) Maximum Performance (MaP) Testing of Popular Toilet Models: 15th Edition. Veritec Consulting Inc. and Koeller and Company.

263. Najafi, M. (2010) Trench Less Technology Piping, Installation and Inspection. McGraw Hill, WEF Press and ASCE Press.

264. Bergdolt, J., Sharvelle, S., and Roesner, L. (2011) Guidance Manual for Separation of Graywater from Blackwater for Graywater Reuse. WERF Project #INFR4SG09a. Water Environment Research Foundation, Alexandria, VA.

265. Roesner L.A, Qian Y, Criswell M., Stromberger M. and Klein S.L. (2006) Long-term Effects of Landscape Irrigation Using Household Graywater-Literature Review and Synthesis.

266. Sharvelle, S., Roesner, L.A, Qian, Y., and Stroberber, M. (2010) " Interim Report: Long- term Study on Landscape Irrigation Using Household Graywater – Experimental Study,

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267. U.S. EPA (2000) Report to Congress: Implementation and Enforcement of the CSO Control Policy, Report No. EPA 833-R-01-003, U.S. EPA, Washington, D.C.

268. Buchanan, J., Deal, N., Lindbo, D., Hanson, A., Gustafson, D., and Miles, R. (2008) Cost of Individual and Small Community Wastewater Management Systems, WERF, Alexandria, VA.

269. Schladweiler, J.C. (2011) Tracking down the Roots of our Sanitary Sewers, www.sewerhistory.org.

270. ConnexusCorp (2011) Plumbers Directory.com, http://www.plumbersdirectory.com/improvements/low-flow-toilets.

271. Enviro Options, Ltd (2011) Enviro Loo: Model BP1040, http://www.enviro- loo.com/index.php?option=com_content&task=view&id=17&Itemid=33.

272. Edmonds, M. (2011) How green is a self-contained composting toilet? Discovery Communications, LLC. http://tlc.howstuffworks.com/home/composting-toilet1.htm.

273. Propelair® (2011) Propelair® Sanitary Systems, Phoenix Product Development Ltd, http://www.propelair.com/.

274. Orenco Systems® (2011) Sand Filter Control Panels Submittal Data Sheet, Orenco Systems®, http://orenco.com/documents/systems/SSF1PTRO%20submittal.pdf.

275. Environment One Corp (2011) E/One Sewer Systems: Environmentally Sensitive, Economically Sensible, http://www.eone.com/sewer_systems/intro/index.htm.

276. Northeast Trenchless Association (2011) Northeast Trenchless Association, Inc, http://www.northeasttrenchless.com/.

277. Incinolet® (2006) Electric Incinerating Toilet, Research Products/Blankenship, Inc, http://www.incinolet.com/aboutus_2.htm.

278. Caroma® (2011) Toilet Suits, GWA and Kitchens, http://caroma.com/.

279. U.S. EPA (1999) Wastewater Technology Fact Sheet: Ultraviolet disinfection, Report No. EPA 832-F-99-064, U.S. EPA, Washington, D.C.

280. U.S. EPA (2000) Wastewater Technology Fact Sheet: Free Water Surface Wetlands, Report No. EPA 832-F-00-024, U.S. EPA, Washington, D.C.

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281. Palmer, N., Lightbody, P., Fallowfield, H., and Harvey, B. (1998) Australia’s Most Successful Alternative to Sewerage: South Australia’s Septic Tank Effluent Disposal Schemes, Neil Palmer, North West Water.

282. Archer Engineers (2007) Evaluation and Analysis of Sanitary Sewer Collection Systems for Proposed Sewer District No. 5: City of La Canada Flintridge, California, Archer Engineers.

283. U.S. EPA (1996) Sanitary Sewer Overflows: What are they and how can we reduce them? Report No.EPA 832-K-96-001, U.S. EPA, Washington, D.C.

284. King County, WA (2011) What is infiltration and inflow? http://www.kingcounty.gov/environment/wastewater/II/What.aspx.

285. Myers® (2011) Submersible Grinder Pump Systems, Pentair Water. http://www.femyers.com/Grinder%20Packages.htm.

286. Wikipedia (2011) Vacuum Sewer, Wikipedia, http://en.wikipedia.org/wiki/Vacuum_sewer.

287. Water Environment Federation (2008) Alternative Sewer Systems, 2e: Manual of Practice FD-12, WEFPress, Alexandria, VA.

288. Niagara Region (2011) Closed Circuit Television Inspection of Regional Trunk Sewers, Niagara Region.

289. nodig-construction.com (2011) Cement Mortar Lining: Wet Spray Process and Microtunneling, http://www.nodig-construction.com/index.cfm.

290. Presby Environmental, Inc. (2011) Design Technical Information, http://presbyeco.com/.

291. Trenchless Technology of Tennessee, Inc. (2008) The Problem, Trenchless Technology of Tennessee, http://www.nuflowtech.com/products/structurallining.aspx.

292. Sewer Equipment Company of America® (2010) Jetting Root Cutters (Model WJ-49P), http://www.sewerequip.com/jetting_rootcutters.htm.

293. CuraFlo, Inc (2011) Erosion and Corrosion, CuraFlo, Inc. http://new.curaflo.com.

294. U.S. EPA (1999) Collection Systems O&M Fact Sheet: Trenchless Sewer Rehabilitation, EPA Report No. EPA 832-F-99-032, U.S. EPA, Washington, D.C.

295. K&R Plumbing (2011) Pipe Ramming, K&R Plumbing, OR. http://www.kandrplumbing.net/pipe_ramming.html.

296. Microphor (2011) Ultra Low Flush Toilet, Wabtec Company. http://www.microphor.com/index.shtml.

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297. BB Innovation & Co AB (2011) WC-Dubbletten, http://www.dubbletten.nu/english- presentation/WCdubbletteneng.htm.

298. Mr. Rooter (2011) Clogged drain cleared with cable and HydroScrubTM , http://www.mrrooterci.com/hydroscrub-service/.

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