Williams, Matthew

Matt Williams is a Regional Sales Manager and Anaerobic Product Manager at Thermal Process Systems and has worked in the water and wastewater industry for nearly 20 years, serving in various roles in manufacturing and consulting with an emphasis on biosolids and Anaerobic Digestion. He is a Professional Engineer licensed in Utah, New York and Maryland. He was the lead author for the Stabilization chapter of the WEF Manual of Practice 8 - Design of WRRFs. Matt earned his Bachelor of Science and Master of Engineering degrees in environmental engineering from Cornell University. An avid birdwatcher and nordic ski-dad, he currently lives in the mountains of Utah with his wife and 4 kids.

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)