You Have Co-Digestion Now What? WERF Research Into the Operational Impacts of Co-Digestion 95 TH Annual Conference | November 2015 | Raleigh Convention Center, Raleigh, NC

Acknowledgements Lauren Fillmore – WERF Lori Stone – LA Stone Tim Muster – CSIRO Hazen and Sawyer –Jared Hostetler –Wendell Khunjar –Irene Chu –Mike Bullard

Agenda Why Energy Neutrality Project Background Survey Approach and Methodology Survey Responses Survey Results Example Case Study Q&A

Why Energy Neutrality

Just Ask Wally and Dilbert…

A New Paradigm Has Emerged

Objective Energy self sufficiency for wastewater treatment plants Two pathways: –Reduction of energy consumption –Increase in energy capture Anaerobic digestion a significant pathway for energy capture

Research Pathways For Energy Improvements

Co-Digestion Related Projects Three interrelated projects –Hazen and Sawyer team –Carollo team –Kennedy-Jenks team Combined goal to best account for the operational impacts of co-digestion Hazen and Sawyer project focuses on a survey to document real world experiences with co-digestion

Project Background

Team Members Principal Investigator: Matt Van Horne, Hazen and Sawyer CSIRO LA STONE LLC Lori Stone Other Partners > 20 utilities confirmed for partnership (leveraging over $600,000 of previous work) 2 university research programs

Tasks 1.Characterize the potential HSWs for co-digestion Utility Survey Database of substrates and operational knowledge 2.Identify/quantify co-digestion implications Economic tool development (treatment, sidestream, biosolids, biogas) Build on OWSO5R07 3.Provide operational solutions Identify key monitoring elements Identify recommended preventative actions

Deliverables and Outcomes Objective 1 –Database of survey results –To be shared among all 3 teams –Include utility partners from all teams and interested participants Objective 2 –Economic assessment tool –10 case studies Objective 3 –List of key parameters –Compendium of corrective actions

Survey Methodology

Survey Question Flow Question 1: General Demographics Question 2: What is the status of your co-digestion program? A) Currently active program B) Study completed, implementation forthcoming C) Study completed, implementation not forthcoming D) Future program possible, study(ies) not yet completed E) No program under consideration at this time Specific general questions for each category to gauge availability of information and magnitude of program. Option to continue into Phase 2 level of study or come back at a later time or be contacted by a research team member for “face to face” information transfer

Current Status Survey publicized on December 1, 2014 Survey closed March 15, 2015 Results were received globally Analysis of responses Case study identification Economic tool development

Survey Responses

Phase 1 Survey Plus 2 anonymous submittals

Phase 2 Survey

Phase I Survey Results

Phase I Q11 – Program Status

Phase I Q12 – Type of HSW Collected *Percentage of 21 respondents who are actively co-digesting. “Other” wastes included glycerin and biodiesel.

Phase I Q15 – HSW addition to process

Phase I Q17 – Co-digestion drivers No impact Minor impact Moderate impact Strong impact

Phase I Q19 – Amount of HSW Collected in 2013 Estimated Range of HSW Volume of 20 Respondents –0.25 MG/year to 200 MG/year Estimated Average of HSW Volume of 20 Respondents –20 MG/year Estimated Median of HSW Volume of 20 Respondents –3.5 MG/year

Phase I Q21 – Types of Digestion Of facilities that have co- digestion –18 of 21 respondents use Mesophilic –3 of 21 respondents use Thermophilic Of facilities that do not have co-digestion –1 of 4 respondents have no anaerobic digestion –3 of 4 respondents use Mesophilic

Phase II Survey Results

Phase II Q8 – How Respondents Identified Acceptable HSW Streams Of 10 respondents, all: –Had HSW locally available in large quantities –Decided the waste would be easy to process and only cause minimal changes to the existing process A vast majority of respondents: –Have a steady supply of HSW –Are already receiving HSW elsewhere –Bench/pilot tested with favorable results –Had nuisance HSW in the collection system

Phase II Q11 – Pilot Testing Of 12 respondents: –5 did run a pilot test before accepting waste –7 did not run a pilot test before accepting waste Of the respondents who did run a pilot test: –3 are willing and able to share pilot test data/summary reports

Phase II Q15 – HSW Sourcing Of 11 respondents: –3 process HSW for free –7 charge a tipping fee –2 both accept HSW for free and charge a tipping fee –1 accepts HSW for free with the intention of charging a tipping fee in the future –None pay for HSW

Phase II Q18 – HSW Sourcing *Others: “Both”, “Waste producers have nowhere else to go”

Phase II Q19 – HSW Sourcing *10 “No”, 2 “Yes”

Phase II Q27/28 – HSW Pretreatment *1 other: FOG aerobic pretreatment

Phase II Q63 – Digester Loading *1 other: proprietary software

Phase II Q67 – Volatile Solids Reduction

Phase II Q72 – Enhanced VSR Reduction Only 3 of 8 respondents said “Yes”

Phase II Q73 – Enhanced Digester Gas Production 8 of 9 respondents said, “Yes” Reported gas increases ranged from 15% to over 300%

Phase II – Effects of Co-digestion 9 of 9 respondents said that co-digestion had no effect on the quality or quantity of centrate from the dewatering facility 9 of 9 respondents said that co-digestion had no effect on dewatering 7 of 8 respondents said that co-digestion had no effect on the biosolids quantity or quality produced; the other 1 respondent said that co- digestion enhanced the biosolids quality

Phase II – Operation & Maintenance

Phase II Q87 – Odor Control Changes

Phase II Q89 – Receiving & Pretreatment

Phase II Q90 – Receiving & Pretreatment

Phase II Q91 – Receiving & Pretreatment

Example Co-Digestion Case Study F. Wayne Hill WRF, Gwinnett County, GA

F. Wayne Hill, System Overview Placed in service in January 2012 Receives up to 30,000 gpd of pre- screened grease trap waste and sugar processing waste

Overview of Receiving and Pretreatment Hauler offload by pressurizing tanks (no wear /tear on unloading pump) Access controlled by keypad Records delivery, flow & pH to billing system Integral grinder and rock trap (overwhelmed by high debris loads)

4 tanks - 20,000 gallons/ea Insulated and jacketed Radar level sensor on top Pressure level sensor at bottom Tank Configuration Access for cleaning and to top of tank

Summary Findings Limit or preheat any kind of pretreatment High debris loads are a problem – need separate rock trap Haulers using air assist offloading works well Concentric tube heat exchangers are effective and appear to not be a maintenance issue (over initial duration) Hose pumps not recommended Do NOT feed grease upstream of digester heat exchangers Integrated odor control works for Gwinnett County

Matt Van Horne, P.E