Williams, Matthew

Matt Williams is the Business Development Manager at TPS and has been involved with digestion and biosolids for over 20 years. Most recently, he...

Joined:

About Williams, Matthew

Matt Williams is the Business Development Manager at TPS and has been involved with digestion and biosolids for over 20 years. Most recently, he served as lead author for the stabilization chapter of the 7th edition of Design of Water Resource Recovery Facilities, MOP 8. Matt is an avid birdwatcher, Nordic skier, runner-and Dad. He lives in the mountains of Utah with his wife and four kids.

Williams, Matthew

Titles from this speaker

Description: Anaerobic Digestion with Nutrient Control - What if your Digesters were the...

Anaerobic Digestion with Nutrient Control - What if your Digesters were the Sidestream?

Abstract

Traditional Anaerobic Digestion processes can create undesirable challenges at WWRFs. Nitrogen recycle from dewatering can have a significant impact on the overall loading to the facility and Phosphorus released under anaerobic conditions can negatively impact dewatering performance. These problems increase chemical and energy costs and create many operational challenges. These proven processes are well-established and employed (independently) at several facilities but, when they are used in concert with the addition of a recycle loop, the solids process effectively becomes sidestream nutrient removal. Managing these nutrients in solids processes that are optimized for the desired biology has other side-effects including decreased H2S production, reduced odor and more robust digester performance. Mesophilic Anaerobic Digestion (MAD) is commonly used in larger wastewater treatment plants in order to stabilize solids and generate biogas for heat and energy. While various staged digestion approaches have been understood for years and implemented at some facilities, the added complexity (often with only marginal benefits) has caused many WRRFs to stick with conventional MAD. The benefits of post-aerobic digestion (PAD) following anaerobic digestion and and Acid reactor ahead of MAD have been generally understood, if not widely used. However, those two 'add-ons' had traditionally been viewed as independent. Data from a PAD-only facility that has been in operation for 10 years will be discuss in conjunction with recent pilot testing at several facilities that consistently confirms significant results when both an Acid reactor and PAD are added to conventional MAD digesters with a recycle loop to capitalize on the biology and chemistry resulting from the conditions in those reactors. H2S concentration in the biogas was significantly reduced, without the addition of ferric chloride or other chemicals, which would significantly extend the life of H2S removal systems and reduce odor and corrosion challenges and lower chemical costs. Because the process better controls the pH and Ammonium concentration (through nitrification-denitrification) through the anaerobic digester system, ammonia toxicity to methanogens is reduced and the stoichiometry is not conducive to struvite formation. In addition, this nutrient control within the solids process has the ability to eliminate the need for additional sidestream tankage and processes. Dewatering significantly improved with added VS destruction and because aerobic biology more effectively breaks down the Extracellular Polymeric Substances (EPS) the cells form during anaerobic digestion. In one pilot study, coagulant was eliminated and polymer dose dropped to achieve 32% TS in the dewatered cake. Through reduced chemical use, optimized digester chemistry, increased solids destruction and other consequential benefits, the capabilities of this system offer savings and solutions for several common MAD challenges that outweigh the costs and drawbacks.

This paper was presented at the WEF Residuals and Biosolids Conference, June 18-21, 2024.

SpeakerWilliams, Matthew

Presentation time

14:30:00

15:00:00

Session time

13:30:00

15:00:00

SessionNutrient Considerations and Digestion

Session number16

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicAerobic Digestion, Anaerobic Digestion, Nutrient Removal

Author(s)

Williams, Matthew

Author(s)M. Williams1, J. Wippo1

Author affiliation(s)Thermal Process Systems 1; Thermal Process Systems 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159459

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count14

Follow The Nitrate Pathway To Cleaner Digestion & More Biogas

Abstract

Introduction Mesophilic Anaerobic Digestion (MAD) is commonly used in larger WRRFs to stabilize solids and generate biogas for heat/energy (CHP) or injection into natural gas pipelines (RNG). The benefits of acid digestion ahead of MAD and post-aerobic digestion (PAD) after MAD have been generally understood and implemented at several facilities to improve operations. Those two MAD 'add-ons' had traditionally been only used independently. However, some very interesting and useful outcomes develop when a recycle loop is employed to send nitrite from the nitrifying PAD to the Acid Reactor for denitrification. Process Background More frequently discussed in the nutrient removal world, the presence of nitrate makes a reactor 'anoxic' not 'anaerobic'. The nitrate-laden recycle from the PAD helps the Acid Reactor by increasing pH, reducing corrosivity and creating optimal conditions for hydrolyzing bacteria. Because of this, the methanogens in the anaerobic digester are more efficiently able to produce more biogas with a higher methane content. The nitrates present in the Acid Reactor are denitrified in a reaction that is biologically and energetically preferred over sulfate reduction. Nitrate has been used to control odors within sewers, at headworks and elsewhere by suppressing the population of sulfate-reducing bacteria (SRBs). Within the world of anaerobic digestion, the nitrate pathway serves to significantly decrease the concentrations of Hydrogen Sulfide (H2S) in the biogas. Because of the recycle, the effects of the nitrification-denitrification occurring within the biosolids treatment process decreases the concentration of ammonia within the anaerobic digester. Since both ammonia and H2S can be inhibitory to methanogens, lower concentrations contribute to increased biogas production. Pilot Studies Recent pilot studies at several facilities in Indiana, California, Arizona and Michigan have shown some consistent and significant results that are summarized here. Additional data and discussion will be provided in the paper and presentation: H2S concentration in the biogas was consistently reduced by at least 90%, without the addition of ferric chloride or other chemicals, which would significantly extend the life of H2S removal systems and reduce odor and corrosion challenges and lower chemical costs. Biosolids mass (and hauling costs) are reduced in at least four cumulative ways: Increased volatile solid (VS) destruction, No metal salt precipitates, improved dewatering, and decreased liquid-stream solids production (through reduced loadings in dewatering return flow). Since pH is lowered and ammonia concentrations are lower, the stoichiometry is not conducive to struvite formation. Ammonia and H2S toxicity on methanogens is reduced. The combined effect of increased VS destruction and a richer (higher methane %) in the biogas results in a significant (~10%) increase in the net energy yield from the digesters. Dewatering significantly improved with added VS destruction and because aerobic biology more effectively breaks down the Extracellular Polymeric Substances (EPS) produced by cells during anaerobic digestion. In one pilot study, coagulant was eliminated, polymer dose dropped and the dewatered cake achieved 32% total solids. Nutrient control within the solids process eliminates the need for additional sidestream tankage, heating and additional processes. Conclusion The recycle from the PAD to the Acid Reactor promotes the nitrate pathway over less favorable (sulfur) pathways. Through reduced chemical use, optimized digester chemistry and biology, increased solids destruction, enhanced methane production and other consequential benefits, the capabilities of this process offer savings and solutions for several common MAD challenges. By harnessing the power of biology in creative ways, the entire anaerobic digestion system becomes more robust and resilient: less reliant on chemicals and external inputs.

The nitrate pathway provides numerous benefits in an Anaerobic Digestion system including enhanced biogas production, reduced H2S & less struvite via nitrogen removal in the digesters. By producing nitrate in an Aerobic Digester and recycling flow back to an Acid Digester, denitrification occurs upstream of the Anaerobic Digester. This process increases pH and optimizes conditions for hydrolyzing bacteria, boosting VSR and biogas methane content.

SpeakerWilliams, Matthew

Presentation time

09:30:00

09:50:00

Session time

08:30:00

10:00:00

SessionEnhancing Digestion to Improve Operations and Resource Recovery: Capture of Control

Session number501

Session locationRoom 256

TopicBiosolids and Residuals, Energy Production, Conservation, and Management, Facility Operations and Maintenance, Intermediate Level

Author(s)

Williams, Matthew, Wippo, Justin, Pressley, Richard

Author(s)M.J. Williams1, J. Wippo2, R. Pressley3

Author affiliation(s)1Thermal Process Systems, UT, 2, IN, 3Thermal Process Systems, IN

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159626

Volume / Issue

Content sourceWEFTEC

Word count11

Description: The Sameâ€¦But Completely Different: Thermophilic Aerobic Digestion...

The Sameâ€¦But Completely Different: Thermophilic Aerobic Digestion Overhaul(s) in the Pacific Northwest

Abstract

The McMinnville Water Reclamation Facility (WRF), located in Oregon's Willamette Valley, has long relied on thermophilic aerobic digestion to manage biosolids while supporting a community known for tourism, agriculture, and environmental stewardship. The facility previously operated a first-generation Autothermal Thermophilic Aerobic Digestion (ATAD) system consisting of three digesters with proprietary mixer-aerators and foam 'cutters'. Since startup in 1996, the legacy system (with some innovative aeration and mixer upgrades in 2006) was usually capable of achieving thermophilic conditions, but experienced persistent operational challenges, including poor oxygen transfer, incomplete digestion, odors, solids loading limitations and difficulty maintaining stable thermophilic temperatures-issues that became more pronounced during seasonal production of tertiary sludge. Despite these challenges the WRF staff was proactive, persistent, and resourceful, which enabled them to improve, tweak and operate their first generation ATAD system for nearly 30 years - much longer than many others. Ultimately, it was time to address these limitations and improve long-term reliability, so McMinnville evaluated options and ultimately selected a second-generation ThermAer ATAD system. ThermAer utilizes jet aeration (pumps, blowers and jet headers), instrumentation, and integrated process control to deliver consistent solids reduction, Class A biosolids production without offensive odors. This technology has been refined through more than three decades of full-scale operating experience and had been in use for 15 years at another facility in the Pacific Northwest - another upgrade of a first-generation ATAD system in Douglas County, Washington. The construction and phasing process was unique in that the existing steel ATAD tanks were to remain and would be operated until the new ThermAer system was completed. There were modifications to the odor control air handling systems to incorporate other nearby processes. The existing post-digested, Class A liquid biosolids storage tank remained in place with some minor (though exciting) modifications. The new tanks were all concrete with an equipment room placed between the ThermAer and SNDR. New odor control biofilters were added. At McMinnville, the ThermAer process was started up in the spring of 2025. Unlike Anaerobic Digester startups that often require extensive planning, seeding and phased feeding, the fast-growing aerobic biology established very quickly, and the first tank was at operating temperatures in just over a week. These digesters achieve sustained thermophilic temperatures of approximately 59-63 °C (140-150°F) without supplemental heat input. Like a compost pile, in this aerobic process, heat is generated internally through exothermic microbial oxidation of organic matter. Evaporative heat losses are minimized through high-efficiency jet aeration and precise oxygen delivery. Oxidation Reduction Potential (ORP), temperature, and pH are continuously monitored to dynamically match oxygen supply with biological demand, ensuring complete oxidation while conserving energy. The variable-flow jet aeration system provides high-shear mixing, excellent oxygen transfer efficiency at low air-to-liquid ratios and effective foam control via hydraulic splash cones. The ThermAer upgrade increased biosolids processing capacity at McMinnville by approximately 20% while achieving total solids reductions of 48-55% and volatile solids destruction of 60-65 %. Improved cell lysis under thermophilic conditions, reduces hauled biosolids volumes, and enables digestion of tertiary sludge streams that previously strained the original system. The combination of time, temperature, and isolation meets USEPA Part 503 requirements for Class A biosolids, expanding reuse and land application options. %. The specifications required specific performance criteria to be met and some of this data will be shared. Ammonia released during thermophilic digestion is managed through integration with a Storage Nitrification Denitrification Reactor (SNDR). Following the ATAD, biosolids are transferred to the SNDR, which operates under mesophilic conditions where nitrification and denitrification can occur. Process control based on pH, temperature, and ORP enables conversion of ammonia to inert nitrogen gas without the need for external alkalinity. Carbon dioxide generated during ThermAer digestion provides sufficient bicarbonate alkalinity to support nitrification, reducing chemical consumption. In addition, ATAD off-gas is routed through the SNDR headspace, where cooler temperatures and lower pH promote ammonia absorption back into the liquid phase, significantly reducing ammonia loading to downstream odor control systems. Final off-gas polishing is provided by a natural media-based biofilter designed for high ammonia removal efficiency, minimal headloss, and low energy demand. The integrated ATAD-SNDR-biofilter configuration delivers near-zero odor emissions, a critical performance requirement for McMinnville and any facilities located near residential, commercial areas. Operational experience at McMinnville mirrors experiences installations, including the Douglas County, Washington ThermAer system commissioned in 2009. Together, these facilities illustrate how second-generation thermophilic aerobic digestion can reliably overcome the limitations of first-generation ATADs while increasing capacity, improving odor control, and simplifying operation and maintenance. This presentation will focus on McMinnville WRF as a detailed case study allowing an opportunity for the plant to share their story while placing the project within the broader regional and national context of multiple ATAD facilities in the Pacific Northwest and nationwide. Operational data, design considerations, startup experiences, and operator perspectives will be shared to demonstrate how modern ThermAer systems have become a reliable Class A biosolids solution (where that still matters) and a viable solution to sludge mass and volume reduction challenges where land application and other beneficial use has been restricted.

This paper was presented at the WEF Residuals, Biosolids, and Treatment Technology Conference in Kansas City, MO, May 11-14, 2026.

Presentation time

13:30:00

13:45:00

Session time

13:30:00

15:00:00

SessionDiscussions on Thermophilic Digestion for High-Quality Biosolids

Session locationKansas City Convention Center

TopicDigestion

Author(s)

Williams, Matthew, Grimstad, Erik, Velez, Maria, Wippo, Justin

Author(s)M. Williams1, E. Grimstad2, M. Velez1, J. Wippo

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2026

DOI10.2175/193864718825160254

Volume / Issue

Content sourceResiduals, Biosolids and Treatment Technology Conference

Word count13

Base text size -

Williams, Matthew

Site admin

About Williams, Matthew

My Recent Activity