EPA/600/R-18/280 | June 2019 | www.epa.gov/research Life Cycle Assessment and Cost Analysis of Distributed Mixed Wastewater & Graywater Treatment for Water Recycling in the Context of an Urban Case Study Office of Research and Development Washington, D.C. United States Environmental Protection Agency Life Cycle Assessment and Cost Analysis of Distributed Mixed Wastewater and Graywater Treatment for Water Recycling in the Context of an Urban Case Study Ben Morelli and Sarah Cashman Eastern Research Group, Inc. 110 Hartwell Ave Lexington, MA 02421 Prepared for: Cissy Ma, Jay Garland, Diana Bless, Michael Jahne U.S. Environmental Protection Agency National Exposure Research Laboratory National Risk Management Research Laboratory Office of Research and Development 26 W. Martin Luther King Drive Cincinnati, OH 45268 Date: June 7, 2019 Draft Report: EPA Contract No. EP-C-16-015, Task Order 0003 Report Revisions: EPA Contract No. EP-C-15-010, Work Assignment 3-32 Although the information in this document has been funded by the United States Environmental Protection Agency under Contract EP-C-16-015 to Eastern Research Group, Inc. (Draft Report) and EPA Contract No. EP-C-15-010 to Pegasus Technical Services, Inc. (Report Revisions), it does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Abstract ABSTRACT Communities such as San Francisco, California are promoting decentralized wastewater treatment coupled with on-site, non-potable reuse (NPR) as a strategy for alleviating water scarcity. This research uses life cycle assessment (LCA) and life cycle cost assessment (LCCA) to evaluate several urban building and district scale treatment technologies based on a suite of environmental and cost indicators. The project evaluates aerobic membrane bioreactors (AeMBRs), anaerobic membrane bioreactors (AnMBRs), and recirculating vertical flow wetlands (RVFWs) treating both mixed wastewater and source separated graywater. Life cycle inventory (LCI) data were compiled from published, peer reviewed literature and generated using GPS-X™ wastewater modeling software. Several sensitivity analyses were conducted to quantify the effects of system scale, reuse quantity, AnMBR sparging rate, and the addition of thermal recovery on environmental and cost results. Results indicate that the volume of treated graywater is sufficient to provide for on-site urban NPR applications, and that net impact is lowest when the quantity of treated wastewater provides but does not considerably exceed NPR demand. Of the treatment options analyzed, the AeMBR and RVFW both demonstrated similarly low global warming potential (GWP) impact results, while the AeMBR had the lowest estimated system net present value (NPV) over a 30-year operational period. The addition of thermal recovery considerably reduced GWP impact for the AeMBR treatment process it was applied to, and similar benefits should be available if thermal recovery were applied to other treatment processes. The AnMBR treatment system demonstrated substantially higher GWP and cumulative energy demand (CED) results compared to the other treatment systems, due primarily to the need for several post-treatment processes required to prepare the effluent for disinfection. When the quantity of treated wastewater closely matches NPR demand, the environmental benefit of avoiding potable water production and distribution (for non-potable applications) leads to net environmental benefits for the AeMBR and RVFW treatment systems. The same benefit is possible for the AnMBR if intermittent membrane sparging can successfully prevent membrane fouling. i List of Acronyms LIST OF ACRONYMS AeMBR Aerobic membrane bioreactor ALH Administrative labor hours AnMBR Anaerobic membrane bioreactor BOD Biological oxygen demand BV Bed volume CAS Conventional activated sludge CED Cumulative energy demand CHP Combined heat and power CPI Consumer price index COD Chemical oxygen demand COP Coefficient of performance CSTR Continually stirred tank reactor CT Contact time CV Coefficient of variation DHS Downflow hanging sponge EOL End-of-life EPA Environmental Protection Agency (U.S.) ERG Eastern Research Group, Inc. GE General Electric GHG Greenhouse gas gpm Gallons per minute gpd Gallons per day GW Graywater GWP Global warming potential HDPE High-density polyethylene HHV Higher heating value HRT Hydraulic retention time IPCC Intergovernmental Panel on Climate Change ISO International Standardization Organization LCA Life cycle assessment LCCA Life cycle cost assessment LCI Life cycle inventory LCIA Life cycle impact assessment LMH Liters per m2 per hour LRT Log reduction target LRV Log reduction value MBR Membrane bioreactor MCF Methane correction factor MGD Million gallons per day MLSS Mixed liquor suspended solids NPR Non-potable reuse NPV Net present value ii List of Acronyms O&M Operation and maintenance P Phosphorus psi Pounds per square inch PVDF Polyvinylidene fluoride RVFW Recirculating vertical flow wetland SCFM Standard cubic feet per minute SOTE Standard oxygen transfer efficiencies SRT Solids retention time TKN Total kjeldahl nitrogen TSS Total suspended solids TRACI Tool for the Reduction and Assessment of Chemical and Environmental Impacts U.S. LCI United States Life Cycle Inventory Database UV Ultraviolet VSS Volatile suspended solids WW Wastewater WRRF Water resource recovery facility iii Table of Contents TABLE OF CONTENTS Page 1. STUDY GOAL AND SCOPE ................................................................................................ 1-1 1.1 Background and Study Goal ................................................................................ 1-1 1.2 Functional Unit .................................................................................................... 1-2 1.3 Case Study Building and District Scenarios ........................................................ 1-2 1.4 Case Study Water Reuse Scenarios ..................................................................... 1-4 1.5 Water Quality Characteristics .............................................................................. 1-6 1.6 System Definition and Boundaries ...................................................................... 1-7 1.6.1 Aerobic Membrane Bioreactor ............................................................... 1-7 1.6.2 Aerobic Membrane Bioreactor with Thermal Energy Recovery ................................................................................................. 1-8 1.6.3 Anaerobic Membrane Bioreactor ........................................................... 1-9 1.6.4 Recirculating Vertical Flow Wetland ................................................... 1-10 1.7 Background Life Cycle Inventory Databases .................................................... 1-11 1.8 Metrics and Life Cycle Impact Assessment Scope ............................................ 1-12 2. LIFE CYCLE INVENTORY METHODS ............................................................................... 2-1 2.1 Pre-Treatment ...................................................................................................... 2-1 2.2 Aerobic Membrane Bioreactor ............................................................................ 2-2 2.2.1 Thermal Energy Recovery for the AeMBR ............................................ 2-5 2.3 Anaerobic Membrane Bioreactor ......................................................................... 2-8 2.3.1 Membrane Fouling and Sludge Output ................................................. 2-12 2.3.2 Biogas Utilization ................................................................................. 2-13 2.3.3 Post-Treatment ...................................................................................... 2-13 2.4 Recirculating Vertical Flow Wetland ................................................................ 2-17 2.5 Disinfection ........................................................................................................ 2-20 2.5.1 Ozone .................................................................................................... 2-23 2.5.2 Ultraviolet ............................................................................................. 2-25 2.5.3 Chlorination .......................................................................................... 2-26 2.6 Water Reuse Scenarios ...................................................................................... 2-26 2.6.1 Wastewater Generation and On-site Reuse Potential ........................... 2-27 2.6.2 Recycled Water Distribution Piping ..................................................... 2-28 2.6.3 Recycled Water Distribution Pumping Energy .................................... 2-30 2.6.4 Displaced Potable Water ....................................................................... 2-34 2.6.5 Centralized Collection and WRRF Treatment ...................................... 2-35 2.7 District-Unsewered Scenario ............................................................................. 2-35 2.7.1 Dewatering – Screw Press .................................................................... 2-35 2.7.2 Composting ........................................................................................... 2-36 2.7.3 Compost Land Application ................................................................... 2-36 2.8 LCI Limitations, Data Quality & Appropriate Use ........................................... 2-38 3. LIFE CYCLE COST ANALYSIS METHODS .......................................................................