Conference Agenda

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Session Overview
Session
Session 04A: Resource Recovery
Time:
Monday, 13/Sept/2021:
10:30am - 12:00pm

Location: 410ABC
East Building

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Presentations
10:30am - 11:15am
ID: 235 / Session 04A: 1
Main Technical Program
Topics: Treatment Innovation and the Future, Recycled Water & Resource Recovery, Resiliency, Planning, Climate Science
Keywords: Biogas, co-digestion, combined heat and power (CHP), energy neutrality, liquid organic waste

Beyond Net Zero – Reaching the Next Level of Renewable Energy through Beneficial Use of Food Waste

Kristen Jackson1, Alan Johnston2, Matt Noesen1, Jodie Binger1, Dave Parry1

1Jacobs; 2The City of Gresham, Oregon; , ,

The City of Gresham (City) Wastewater Treatment Plant (WWTP) is a 15 MGD facility located east of Portland, Oregon. The plant accepts and co-digests fats, oil, and grease and beneficially uses their biogas to fuel a combined heat and power system to achieve energy neutral status and they are evaluating how to go beyond net zero. The existing two mesophilic anaerobic digesters at the facility are currently at capacity and in need of an expansion to accommodate projected future loadings for city growth as well as to provide redundancy.

A recently adopted policy by Metro (regional entity) requires mandatory segregation, collection, and alternate processing (not landfilling) of food waste that is generated by businesses within the Portland metropolitan area. The City conducted a study to explore the financial payback options for a digestion expansion project that could fulfill the City’s capacity needs, accept food slurry from Metro’s food waste program (or other liquid organic waste sources), and beneficial use of the additional biogas produced.

The study assessed potential cost and non-cost benefits and impacts associated with additional liquid organic waste loading on the WWTP, digestion alternatives, sidestream recycle loading to the liquids treatment, solids dewaterability, biogas production, and biosolids end use. The study included a business case evaluation considering economic, environmental, social, and operational impacts to assess the favorability of pursuing the selected alternative. Finally, the study included a conceptual design for the selected alternative.

The study has shown that the City could spend 16 million dollars and construct a third mesophilic digester for capacity needs and not accept additional feedstocks nor receive a payback on the investment. Alternatively, the City could spend approximately 30 million dollars to convert two existing digesters to thermophilic technology, construct a third thermophilic digester, expand feedstock receiving, expand cogeneration, and obtain a payback on investment under 10 years by utilizing State incentive programs. The City is planning to conduct a predesign to further refine liquid organic waste availability, revenues and costs, and funding sources for the project.

Brief Biography and/or Qualifications
Kristen Jackson is a Wastewater Treatment Engineer and Project Manager with over 10 years of professional experience and 5 years of expertise in treatment plant process mechanical design, hydraulics, alternative delivery, startup and commissioning, and construction inspection services. She is personally passionate about energy conservation and protecting the environment as she spent three years in the Peace Corps solving rural water and sanitation problems.

Alan Johnston is Senior Engineer and has worked for over 30 years for the City of Gresham. He manages the Wastewater Treatment Plant program. This includes planning, design and construction of capital projects, managing plant operations and maintenance contracts, implementing ongoing asset management strategies, preparing annual operations and capital budget, etc.

Jodie Binger has 10 years of experience focused on renewable natural gas, beneficial use of biogas, and wastewater projects based on a lifelong love of water and outdoor recreation. She thrives on managing project production and coordinating team members to innovatively create solutions to inevitable societal issues in a way that is sustainable and economically viable.


11:15am - 12:00pm
ID: 211 / Session 04A: 2
Main Technical Program
Topics: Wastewater Treatment Process, Recycled Water & Resource Recovery
Keywords: Anaerobic Digestion, FOG, Co-Digestion, Microbial Community

Linking Anaerobic Digester Microbiomes With Resistance To Organic Overloads

Ashley Berninghaus, Tyler Radniecki

Oregon State University, United States of America;

Anaerobic co-digestion has become a popular option to increase biogas production, thus increasing recapture potential, with grease trap waste, or FOG (fats, oils, and greases), showing the highest methane production potential. In order to ensure reactor stability and optimal performance, the correct microbiome composition is essential. However, it is currently unknown what microbiome compositions are optimal for co-digestion nor what operational parameters are most effective at creating these optimal structures. This work monitored nineteen full-scale anaerobic digesters, at six separate facilities, monthly for one year to link operational characteristics with microbiome composition. Of the nineteen digesters studied, three perform FOG co-digestion, four perform co-digestion with biodiesel wash water, one is fed only TWAS (thickened waste activated sludge), and the remaining eleven are fed primary sludge and TWAS. Microbiome composition was analyzed using 16S rRNA amplicon sequencing. Operational data from each of the full-scale facilities (including pH, alkalinity, volatile fatty acids, detention time, temperature, total and volatile solids, free ammonia, organic N, dissolved P, organic P, chemical oxygen demand, and gas production) was examined to determine their influence on microbiome compositions.

Batch resistance assays were created to link microbiome compositions with digester functionality in response to organic over loadings. For each full-scale anaerobic digester tested, twenty-five 100 mL batch anaerobic digesters were used for batch resistance assays. Five batch anaerobic digesters were ran as digestate-only controls, and the remaining twenty were fed 1 mL, 5 mL, 10 mL, and 20 mL of canola oil (in quintuplet). The rates of methane production and methane content of the biogas were used to calculate the functional resistance of each full-scale anaerobic digester. The batch resistance assays were performed in winter and summer to account for seasonal variations in full-scale plant operation and microbiome compositions.

Brief Biography and/or Qualifications
Ashley Berninghaus is a 5th year Ph.D. candidate in the School of Chemical, Biological, and Environmental Engineering at Oregon State University where her work is centered on biologically based renewable energy and water treatment systems. She earned a B.S. in both Chemical and Biological Engineering at Montana State University in 2015 and plans to finish her Ph.D. in Environmental Engineering in the spring of 2022.


 
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