Wippo, Justin

After graduating from Purdue University with a bachelors degree in chemical engineering, he took the lead role in researching PAD processes with the assistance of the company’s extensive history and knowledge of aerobic digestion. He has since worked his way to the role of Engineering Manager where he oversees the development and implementation of municipal digestion projects. He is certified as an EIT and is actively working towards his PE.

Titles from this speaker

Description: Alternate: Optimizing Energy and Nutrient Control with Two-Stage Anaerobic...

Alternate: Optimizing Energy and Nutrient Control with Two-Stage Anaerobic Digestion

Abstract

Anaerobic digestion is used in larger wastewater treatment plants in order to generate energy rather than consuming it. However, operating in a reducing environment limits biodiversity and can create undesirable consequences. As such, research has started taking a harder look into the benefits of post-aerobic digestion (PAD) following anaerobic digestion. One of the common issues faced by anaerobic digesters is becoming overloaded with volatile fatty acids (VFAs). This is a result of the acidogens producing VFAs faster than the methanogens can convert the VFAs to methane; limiting the energy produced by the process. Two-stage anaerobic digestion was used to separate out the more rapid stages of hydrolysis and VFA formation from the much slower step of methane production in order to improve the conversion of organic material to usable energy. Optimizing and stabilizing the anaerobic digesters significantly reduces the oxygen demand in a post-aerobic digester, increasing the energy output while reducing the energy requirements. The methanogen reactor consistently achieved 55-60% VSR with the recycle in effect. Dewatering results from the centrifuge manufacturer showed a significant improvement to the dewatering characteristics of the digested biosolids, as the aerobic cultures used are capable of breaking down the extracellular polymeric substances often produced by anaerobic digestion. No coagulant and only 18 active pounds of polymer per dry ton of biosolids were required to achieve 32% TS in the dewatered cake. Gas chromatography results confirmed draeger tube measurements with a reported H2S concentration of 5.6 parts per billion while also confirming the methane concentration at 62% in the biogas. Further research discovered previously published discussions of the ability of nitrates to inhibit the activity of sulfate-reducing bacteria (SRBs) that produce H2S by offering a more thermodynamically favorable electron receptor. This allowed the recycle from the aerobic process step to effectively inhibit the SRBs, reducing the SRB population from the fermentation stage to the methane-producing stage as well as the H2S present in the biogas. This allowed the system to decouple the nitrification and denitrification processes by shifting denitrification to the acid-phase tank This pilot demonstration showed the capabilities of coupling two-stage anaerobic digestion to a conditioning aerobic digester that recycled material through the system. The recycle supplied by the aerobic digester offset variations in the feed material, improving the stability and energy output of the anaerobic digestion process. High volatile solids reduction combines with the reduction of dewatering chemical requirements and higher cake solids to offer substantial cost savings for facilities. The ability of the recycle to reduce the struvite potential in the methanogen reactor reduces maintenance concerns that often accompany anaerobic digestion. This is linked to the elimination of hydrogen sulfide (H2S) in the biogas, thereby removing the necessity for more expensive forms of H2S treatment and continuous maintenance of boilers and CHP units. The removal of H2S allows facilities to more effectively utilize the energy produced through anaerobic digestion on a more consistent basis. The capabilities of this system offer cost savings and solutions for problems that many anaerobic digestion facilities face.

This paper was presented at the WEF Residuals and Biosolids Conference in Columbus, Ohio, May 24-27, 2022.

SpeakerWippo, Justin

Presentation time

8:30:00

11:15:00

Session time

8:30:00

11:15:00

Session number19

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicAnaerobic Digestion, Biogas desulfurization, Energy Conservation/Management

Author(s)

J. Wippo

Author(s)J. Wippo1

Author affiliation(s)Residuals and Biosolids Speaker; 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May, 2022

DOI10.2175/193864718825158389

Volume / Issue

Content sourceResiduals and Biosolids

Word count11

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

Optimizing Energy and Nutrient Control with Two-Stage Anaerobic Digestion

Abstract

INTRODUCTION Anaerobic digestion is often used in larger wastewater treatment plants (WWTPs) in order to generate energy rather than consuming it. However, operating only in a reducing environment limits biodiversity and can create undesirable consequences. As such, research has started taking a harder look into the benefits of post-aerobic digestion (PAD) following anaerobic digestion. Having a long history of researching and improving aerobic digestion methods, Thermal Process Systems (TPS) sought to apply its existing technologies and knowledge of aerobic digestion to a two-stage anaerobic digestion system. One of the common issues faced by anaerobic digesters is becoming volatile fatty acid (VFA) overloaded. This occurs as a result of the acidogens making VFAs faster than the methanogens can convert the VFAs to methane, limiting the energy produced by the process. Two-stage anaerobic digestion was used to separate out the more rapid stages of hydrolysis and VFA formation from the much slower step of methane production in order to improve the conversion of organic material to usable energy. Optimizing and stabilizing the anaerobic digesters significantly reduces the oxygen demand in a post-aerobic digester, increasing the energy output while reducing the energy requirements. The primary goal of coupling aerobic digestion to anaerobic digestion with a recycle stream was to improve the stability of the anaerobic digester and resulting product by increasing the volatile solids reduction (VSR), improving biogas production and quality, reducing the overall hydraulic retention time (HRT) for the digestion process, and improving the dewatering characteristics. This was primarily achieved by establishing process control parameters around the pH of the anaerobic digester by varying the recycle rates. METHODOLOGY Operation of the pilot unit commenced without utilizing a recycle from the aerobic digester to establish a baseline of operations. During the initial phase of the pilot demonstration, the operational liquid levels of each tank was set so the fermentation tank, methanogen reactor, and aerobic digester operated at 2-, 15-, and 8-day hydraulic retention times (HRTs), respectively. Each phase of the pilot demonstration lasted for three sludge ages of steady-state operation. After the first phase of operating in a plug-flow fashion, the recycle was initiated at 60% of the daily feed amount. The recycle rate was later increased to 80%, 100%, and 150% of the daily feed amount to observe the ability of the system to reduce the struvite precipitation potential in the anaerobic digester by decreasing the ammonia and pH. Continuous monitoring of the system was carried out with the use of Endress & Hauser temperature/ORP/pH probes, liquid level pressure transducers, and vacuum/pressure gauges. The routine liquid analysis of each digesters' contents was carried out with the use of Hach colorimetric test kits. The routine biogas analysis was conducted with the use of Sensidyne gas detection tubes. Theoretical calculations of the potential for struvite formation were performed with the 'Struvite Tool' Microsoft Excel plug-in produced by the Office of Water Programs at CSU Sacramento. Dewatering results were obtained by sending samples to Centrysis Centrifuge Systems in Kenosha, Wisconsin. RESULTS The plug-slow operation of the pilot unit resulted in the methanogen reactor becoming VFA overloaded. This was accompanied by a decrease in the VSR, biogas production, and methane concentration in the biogas. Initiating the recycle rapidly lowered the VFA to alkalinity ratio (VFA/ALK) in the reactor; bringing it to literature values that designate a healthy anaerobic digester. The VFA/ALK was maintained at proper values without spikes in the VFA concentration or foaming events in the methanogen reactor for the remainder of the pilot demonstration. The methanogen reactor consistently achieved 55-60% VSR with the recycle in effect. Dewatering results from the centrifuge manufacturer showed a significant improvement to the dewatering characteristics of the digested biosolids, as the aerobic cultures used are capable of breaking down the extracellular polymeric substances often produced by anaerobic digestion. No coagulant and only 18 active pounds of polymer per dry ton of biosolids were required to achieve 32% TS in the dewatered cake. Not having a requirement for standard metal salt coagulants reduced the amount of phosphorus in the biosolids cake; bringing the nitrogen to phosphorus ratio in the cake to the range that agronomic studies suggest makes up a healthy soil. Increasing the recycle through the system effectively allowed the aerobic digester to remove a larger mass of ammonia from the methanogen reactor daily. The decreasing ammonia was accompanied by a controlled pH adjustment in the reactor. The methanogen reactor maintained less than 500 mg/L of ammonia and a pH of 6.8 throughout the steady-state portion of this phase of the pilot; levels that theoretically eliminate the production of struvite. The actual data obtained during the pilot demonstration showed the decreasing ammonia and pH subsequently led to an increase in the soluble ortho-phosphate present in the digester. These effects were not accompanied by a decrease in the VSR or biogas production. Another observed result that was observed was the H2S in the biogas became non-detectable with the 1 part per million gas detection tubes. The GC results confirmed this observation with a reported H2S concentration of 5.6 parts per billion while also confirming the methane concentration at 62% in the biogas. Further research discovered previously published discussions of the ability of nitrates to inhibit the activity of sulfate-reducing bacteria (SRB) that produce H2S by offering a more thermodynamically favorable electron receptor. The nitrates supplied by the recycle from the aerobic digester inhibited the SRBs while promoting a sulfur-oxidizing, nitrate-reducing bacteria (Lomas, 2005). This allowed the system to decouple the nitrification and denitrification processes by moving denitrification to the fermentation tank. DISCUSSION AND CONCLUSIONS This pilot demonstration showed the capabilities of coupling two-stage anaerobic digestion to a conditioning aerobic digester that recycled material through the system. The recycle supplied by the aerobic digester offset variations in the feed material, improving the stability and energy output of the anaerobic digestion process. Maintaining high VSR increases the total amount of methane produced through anaerobic digestion. High VSR combines with the reduction of dewatering chemical requirements and higher cake solids to offer substantial cost savings for facilities. The ability of the recycle to reduce the struvite potential in the methanogen reactor reduces maintenance concerns that often accompany anaerobic digestion. This is linked to the elimination of H2S in the biogas which removes the need for more expensive forms of H2S treatment and continuous maintenance of boilers and CHP units. The removal of H2S allows facilities to utilize the energy produced through anaerobic digestion on a more consistent basis. The capabilities of this system offer cost savings and solutions for problems that many anaerobic digestion facilities face.

This paper was presented at the WEF/IWA Residuals and Biosolids Conference, May 16-19, 2023.

SpeakerWippo, Justin

Presentation time

13:30:00

14:00:00

Session time

13:30:00

16:45:00

SessionSession 07: Intensifying Digestion

Session number07

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicDigestion & Stabilization