Waterborne Sanitation TT 481/11 Waterborne Sanitation Design Guide Design Sanitation TTWaterborne 481/11 Design Guide SJ van Vuuren & M van Dijk TT 481/11 WATERBORNE SANITATION DESIGN GUIDE Report to the WATER RESEARCH COMMISSION By S J van Vuuren and M van Dijk University of Pretoria WRC REPORT NO. TT 481/11 MARCH 2011 Obtainable from: Water Research Commission Private Bag X03 Gezina 0031 The publication of this report emanates from a project entitled: Development of a South African Guide for the Design and Operation of Waterborne Sewerage Systems (WRC Project No. K5/1744) DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. ISBN 978-1-4312-0078-8 Set no 978-1-4312-0080-1 Printed in the Republic of South Africa Executive Summary The general health of the population improves when people have access to basic clean water supply and sanitation. The safe disposal of human excreta and greywater is vitally important in the control of infectious and other communicable diseases and the design and construction of appropriate sanitation systems is of paramount importance in contributing to the safe disposal of human excreta. However, on its own, the proper planning and construction of sanitation systems does not provide a guarantee that the general health of the population will improve. A holistic approach to health care is required, with the provision of suitable sanitation being just one of the necessary components thereof. A three-pronged approach was followed to source the information required to produce this guide. At the outset, the authors collaborated with a number of local authorities in South Africa and gathered information regarding the design and operation of their sewer systems. The main concerns raised by the managers of the various sewer networks in South Africa were also noted and were addressed in compiling this report. Secondly, the standards and guidelines used in practice in the design and operation of waterborne sanitation systems were reviewed. Thirdly, many sources of information were consulted and a synthesis of the material was tailored to South African conditions to produce a comprehensive guide on waterborne sanitation systems. In particular, the following documents were heavily relied on: Guidelines for the Provision of Engineering Services and Amenities in Residential Township Development (CSIR, 2003); Alternative Sewer Systems (WEF Manual of Practice, 2008); the USEPA (1991) manual entitled Gravity Sanitary Sewer Design and Construction; and the Sewer Design Manual (ASCE, 1982). This report summarizes the available knowledge, information and advancements of all waterborne sanitation systems used in South Africa. The objective of the report is to provide a concise guide for the analysis and design of waterborne sanitation systems. In order to streamline the planning and design process in South Africa a three-tier philosophy is proposed for sewage collection system planning and design. As described by Jacobs and Van Dijk (2009) the philosophy used originates from the field of transport engineering where three different ‘solution levels for design procedures’ are documented in the South African Code of Practice for the Design of Highway Bridges and Culverts (Department of Transport, TMH 7). Adopting this concept for the planning and design of sewage collection systems leads to three technical tiers. This three-tiered philosophy could be used as a basis to derive a best management practice for sewer system planning and design. General information Detailed design Specialized/Advanced design Throughout this guide the information provided is partitioned into these three tiers. Waterborne sanitation design guide i The four main waterborne sanitation systems which are described in this guide are: Conventional gravity sewer Vacuum sewer systems Small-bore sewer Simplified sewerage A summary description with advantages and disadvantages of these systems is provided. A technical design criterion for designing each of these systems is given with a worked example guiding the designer through the process to be followed. To provide further classification and background information photos, videos, software and additional literature were included on the accompanying DVD. Where this icon is shown in this report movie clips, photos, additional literature or software are available in the SewerAid DVD to visually enhance the understanding of the specific concept. Waterborne sanitation design guide ii ACKNOWLEDGEMENTS The research presented in this report/guide emanated from a study funded by the Water Research Commission (WRC), whose support is acknowledged with gratitude. The Reference Group made an important contribution in steering and guiding this study to obtain the format and results reflected in this report. The support of the Chairman and Manager of this study, Mr Jay Bhagwan, as well as the staff of WRC, is greatly appreciated. The members of the Reference Group and Project Team are: Mr JN Bhagwan : Water Research Commission – Chairman Ms C Dladla : Water Research Commission – Project co-ordinator Mr NS Ireland : City of Cape Town Mr CS Crawford : DWAF Mr M Ristic : SRK Dr HE Jacobs : University of Stellenbosch Prof NP Armitage : University of Cape Town Mr JL Harrison : eThekwini Water and Sanitation Mr K Moodley : PD Naidoo and Associates Prof SJ van Vuuren : University of Pretoria (Project leader) Mr M van Dijk : University of Pretoria Mr A Otterman : PULA We also acknowledge with thanks the inputs made by a number of students from the University of Pretoria, who conducted some of the personal interviews and assisted in compiling this report. They are: Messrs A Oosthuizen, A Beck, JP Velloen and GL Coetzee, as well as Miss M Peens. Waterborne sanitation design guide iii Waterborne Sanitation Design Guide Table of Contents Page Executive Summary i Acknowledgements iii Table of Contents iv List of Tables ix List of Figures x Appendices xii Glossary of Terms xiii List of Symbols xix Abbreviations xx 1. INTRODUCTION 1 2. PLANNING CONSIDERATIONS AND POLICIES 4 3. WATERBORNE SANITATION SYSTEMS 9 3.1 Introduction 9 3.2 Classification of sanitation systems 10 3.3 History of design standards and criteria 11 3.4 Conventional gravity sewer system 13 3.4.1 General description 13 3.4.2 Technical design criteria 15 3.4.3 Construction 20 3.4.4 Advantages and disadvantages 22 3.5 Vacuum sewer systems 24 3.5.1 General description 24 3.5.2 Technical design criteria 25 3.5.3 Construction 30 3.5.4 Advantages and disadvantages 31 3.6 Small-bore sewer 33 3.6.1 General description 33 3.6.2 Technical design criteria 35 3.6.3 Construction 37 3.6.4 Advantages and disadvantages 40 3.7 Simplified sewerage / shallow sewerage / condominial sewerage 41 3.7.1 Background and general description 41 3.7.2 Technical design criteria 41 3.7.4 Construction 45 3.7.5 Advantages and disadvantages 46 3.8 Other systems 48 3.8.1 Conservancy tank system 48 3.8.1.1 General description 48 3.8.1.2 Technical design criteria 48 3.8.1.3 Advantages/disadvantages 50 3.8.2 Septic tanks 51 3.8.2.1 Background 51 Waterborne sanitation design guide iv 3.8.2.2 General description 51 3.8.2.3 Technical design criteria 52 3.8.2.4 Advantages and disadvantages 56 3.8.3 Anaerobic digester 56 3.8.4 Aqua-privies 56 3.9 Summary 57 4. COSTING OF WATERBORNE SANITATION SYSTEMS 58 5. DESIGN GUIDELINES FOR CONVENTIONAL GRAVITY SEWER 61 5.1 Sewer system planning 61 5.2 Gravity sewer system design (reticulation, link and main) 62 5.2.1 General 62 5.2.2 Design of sewers 62 5.2.2.1 Design criteria 62 5.2.2.2 Design-flow calculations 63 5.2.2.3 Extraneous flows 66 5.2.2.4 Hydraulics of sewers 70 5.2.2.5 Pipe material 76 5.2.2.6 Alignment of sewers 78 5.2.2.7 Pipe cover 81 5.2.2.8 Loading conditions 82 5.2.2.9 Bedding and backfill 84 5.2.2.10 Corrosion 86 5.2.3 Maintenance holes and transitions 87 5.2.3.1 Manhole location and spacing 87 5.2.3.2 Shape and dimensions 88 5.2.3.3 Construction material 90 5.2.3.4 Fall through manhole 92 5.2.3.5 Terminal cleanouts 93 5.2.4 Erf connections 94 5.2.5 Field testing and inspection 95 5.3 Sewer pump station design criteria 96 5.3.1 General requirements 97 5.3.2 Facility capacity and hydraulic design criteria 98 5.3.3 System design and pump selection 100 5.3.4 Piping and appurtenances 105 5.3.5 Sumps 107 5.3.6 Net positive suction head 109 5.3.7 Electrical, controls, and instrumentation 109 5.3.8 Ancillary equipment 111 5.3.9 Wet and dry well installations 113 5.3.10 Rising/force main 115 5.3.11 Pump-station building and site 117 5.4 Siphon design 117 5.5 Silt trap 118 5.6 Standard drawings and schedule of quantities 118 5.7 House connection pipe 118 5.7.1 Step-by-step design procedure (house connection pipe) 118 Waterborne sanitation design guide v 5.7.2 Worked Example #1: House connection pipe 126 5.7.3 Design hints and tips (house connection pipe design) 128 5.8 Main sewer line 129 5.8.1 Step-by-step design procedure (conventional main sewer design) 129 5.8.2 Worked Example #2: Conventional gravity sewer line design 135 5.8.3 Design hints and tips (conventional sewer design) 140 6.