Fiorino, Dante

Dante has a bachelor's in Civil Engineering from Ohio University and a master's in Environmental Engineering from Youngstown State. He's a licensed...

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About Fiorino, Dante

Dante has a bachelor's in Civil Engineering from Ohio University and a master's in Environmental Engineering from Youngstown State. He's a licensed professional engineer and practices in the Brown and Caldwell Columbus office. Dante serves as project manager on several biosolids and digestion projects locally for the City of Columbus. He's also the Midwest PFAS and research lead for BC and sits on several OWEA committees.

Fiorino, Dante

Titles from this speaker

Description: Acid+ A Novel Treatment Process Configuration for Simultaneous Process...

Acid+ A Novel Treatment Process Configuration for Simultaneous Process Intensification and Struvite Management

Abstract

Acid/gas anaerobic digestion process is based the premise of environmental phasing, such that the conditions with the digestion process are first optimized for hydrolysis, acidogenesis and acetogenesis followed by a methanogenic phase for conversion of the solubilized organics to methane. The City of Columbus Southery WRF in Columbus, OH has operated an acid/gas system for more than a decade, treating a mixture of primary and secondary sludge. Over this period of time the City has conducted research surrounding improving process stability and reliability. One factor that has played a significant role in the operational reliability of the process, for Columbus, is the operation of the acid phase digestion. Reducing the acid phase operation to 1.8 days or less eliminated chronic foaming in the methane phase with the addition of thickened waste activated sludge. The addition of TWAS to the digestion process, reduced the solids disposal costs but increased the production of struvite, which fouls dewatering equipment and return lines. Acid reactors or fermenters have demonstrated very effective release of phosphorus from sludge. This likely make struvite production from the digestion process at Columbus a magnesium limited system. Based on operating observations, there is sufficient magnesium in the water to create a nuisance levels of struvite in the system. Concurrent with the struvite issues, there is a desire on the City's part to better understand the process limits and increase capacity, as Southerly moves into a facilities expansion project. Based on these operational issues, process interests and an impending capital program Columbus wanted to explore the novel process concept of Acid+, a process flow of which is shown in Figure 1. Acid+, modifies a base acid/gas system through the addition of a harvesting digester and recuperative thickening on the methane phase digesters. The harvesting digesters are designed to create an environment where struvite precipitation can be forced and managed. By recycling a flow of neutral pH sludge to the incoming acidified sludge and adding magnesium hydroxide the conditions are set for struvite formation. Using a high-rate gas mix system creates the micro-environment where pH is further increased and granular struvite can be formed, collected and harvested, as show in Figure 2. A collaborative research project was created between the City of Columbus, NYCDEP, University of Massachusetts- Amherst and City College of New York and Brown and Caldwell with funding provided by the Water Research Foundation under project WRF-5108. The project plan looks to understand the different process elements of Acid+, in sequence, such that a controlled approach process evaluation could be conducted. The phase 1 work focused on optimization of the acid phase both in batch and continuous operation, phase 2 looks to evaluate the continuous operation of acid/gas with the findings of phase 1 and then finally phase 3 would integrate the harvesting reactor on the optimized acid gas system, creating an Acid+ configuration. The phase 1 work is complete and the phase 2 is on-going. Figure 3,4 and 5 summarizes the influence of temperature and sludge type on key factors to struvite control for acid plus and overall acid phase digester performance. The fermentation/acidification process, as shown in Figure 4, demonstrates that temperature primarily impacted the rate of acidification, as measured by total VFA. This observation while not unexpected, did also show that the extent of conversion, maximum VFA produced did not appreciably change over the course of the full study period. This suggests that from an intensification strategy, temperature elevation can successfully deployed to reduce reactor size or increase throughput without a loss in performance. However, the degree of acidification achieved will be very sludge specific, for waste activated sludges. This would suggest that the sludge composition and/or biology has an influence of the acidification process. This is demonstrated by the shape of the acid production curves, with different sludges having different rates and time to onset of VFA production. This also holds true for both ammonia release and phosphorus release. Thermophilic operation appears to provide significant benefit to both. A key consideration for Acid+ would be the impact of operating at thermophilic temperatures and and need to reduce temperature to improve struvite precipitation. Based on these data it could be assumed that the treatment process would impact that performance, however when secondary treatment type was considered there was not a clear correlation. Other actors such as EPS content and metals may be influencing the performance as well as wastewater source. These will be explored in greater detail. In the associated paper.

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

SpeakerMuller, Christopher

Presentation time

16:15:00

16:45:00

Session time

15:45:00

16:45:00

SessionNutrient Management Innovations

Session number20

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicAdvanced Treatment, Anaerobic Digestion, Struvite

Author(s)

Muller, Christopher

Author(s)C. Muller1, A. Abouhend2, C. Park2, D. Fiorino1, N. Perez3, K. Ramalingam4, J. Willis1, G. Schweinfurth5, A. Dhanasekar6

Author affiliation(s)Brown and Caldwell 1; University of Massachusetts 2; Brown and Caldwell 1; NYCDEP 3; The City College of New York 4; Brown and Caldwell 1; City of Columbus 5; The Water Research Foundation 6;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159469

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count14

Description: Acid+ Digestion - How Columbus fixed their Acid Phase Digesters and is Researching a...

Acid+ Digestion - How Columbus fixed their Acid Phase Digesters and is Researching a New Process that Intensifies Digestion and Recovers Phosphorus

Abstract

Introduction Today, utilities are being increasingly asked to balance highly sustainable operations while keeping impacts to rate payers to a minimum. Solids stabilization is one area that utilities have used increasingly to achieve that balance, however, there is no integrated solution currently on the market that intensifies digestion while providing nutrient recovery in the same process. This research project will optimize acid gas digestion and develop an improved understanding of acid-gas digestion that will be leveraged to develop a novel process called, Acid+ Digestion. This research was recently selected by the Water Research Foundation (WRF) for a $100,000 matching grant for a total budget of $455,000. The Southerly Wastewater Treatment Plant (WWTP) is the larger of two WWTPs that serve the City of Columbus and the greater Central Ohio sanitary sewershed. Figure 1 shows the existing Dual Phase Digestion System at the Columbus Southerly WWTP. The Methane Phase Digesters have foamed periodically since the system was started in 2009. Foam builds up in the annular space between the digester covers and the tank wall. During severe foaming episodes, foam spills over the tank walls. Foam is a byproduct of the surface chemistry gas, liquid, and solids phases. Foaming robs a system of capacity, which in turn hinders the production of methane gas. Figure 2 shows foaming episode at a Methane Phase Digester. Research Overview Research is expected to begin in early January 2022, and we expect to have preliminary results by May 2022 to be presented for the WEF Biosolids Conference. We also performed preliminary calculations and BioWin modeling as part of the successful WRF proposal that can be presented. Our initial objective is to optimize acid gas digestion ('AG') of wastewater biosolids for clear direction for facilities currently equipped with that process. Our larger objective is to build on optimized AG to develop a novel advanced digestion process called 'Acid+ Digestion' (or simply 'Acid+'). Acid+ would offer water resource recovery facilities (WRRFs) an option to roughly double digester capacity; enhance nutrient resource recovery as struvite; protect digestion, dewatering, and centrate handling from struvite fouling; and reduce biosolids phosphorus (P) by half, with configurations that offer other as-needed site-specific benefits. The optimized-AG and Acid+ processes will each be run in separate controlled, laboratory-scale experiments with conventional Methane Digestion as a control. The research will explore each of the processes benefits as retrofits upstream of existing Methane Digesters. Benefits to both process upgrades are anticipated to include reduced foaming, reduction of H2S in biogas (by wasting acid-phase digester gas), and enhanced process stability. Acid+ is expected to additionally provide controlled production of struvite at lower chemical demand (for resource recovery, protection of methane-phase digesters and piping/equipment from struvite fouling, and reduced biosolids P) while possibly increasing existing digester capacity by 75% to 150%. Figure 3 shows a high-level overview of BC's research objective and project. Acid Phase Digestion The original promise of AG digestion was to create separate environments idealized for hydrolysis and acidogenesis and methane formation; with distinct microbial populations in separate reactors performing better than in a conventional mixed culture. While the underlying fundamentals of acid gas digestion are strong, implementation has been limited to only 10 to 20 facilities in North America due to full-scale performance not matching promised improvements. Our sponsoring utility, City of Columbus failed to realize AG's promised benefits during the initial years of AG operation at the Southerly WWTP. Because the process failed to reduce (and even increased) foaming, Waste activated sludge (WAS) had to be bypassed around digestion to prevent the methane digesters from overflowing through floating-cover annular spaces. WAS bypass cost an extra $1M annually. Two and a half years ago, Darin Wise and Columbus conducted a self-directed study based on results from a University of Wisconsin, Madison masters' thesis (Siebels, 2011) that found maintaining AG solids retention time (SRT) at 1.8 days under all sludge production conditions eliminated foaming. All Southerly WAS is now digested. Figure 4 shows a period of daily and rolling annual, monthly, and weekly average Acid-phase feed at Southerly. These data will later highlight challenges with AG digestion related to consistent SRT maintenance. The Columbus experience described above is not unique and several utilities with AG digestion either eliminated their Acid digesters or have found that the process 'only works' at lower SRTs. Optimize Acid Gas Digestion Our initial investigative track will explore AG digestion with both batch and continuous-feed testing to determine the actual kinetics, operational parameters, and biological consortia that allow a less than-1.8-day AG digester to work well and that cause greater-than-1.8-day SRTs to fail. Our AG testing plan will investigate: - Foaming potential, hydrolysis kinetics, soluble products generation, biogas quantity and quality, and microbial consortia profiles & all at three different operating temperatures. - Response to Short-Term Stressed Conditions. The AG feed volumes highlight actual peak and minimum feed volumes. If an AG tank is operated at 1.4D SRT at average feed of 240,000 gpd, what happens during peak- or minimum- week loading when SRTs become 1.2 days or 1.7 days for a sustained period? - It has been seen that exceeding a maximum SRT (currently set at 1.8 days for southerly) induces problems & but why? Our research will answer that question. - H2S Evolves in Acid-Phase Biogas. Digester gas H2S is often removed by iron sponge, activated carbon, or other finite-life media. The potential to divert the Acid-phase H2S to waste could double the life between media replacements or reduce maintenance on gas use systems like boilers which typically have limited gas treatment. - Inform Acid+ Research. Acid+ effectiveness is dependent on the effectiveness of the 1st-stage Acid digester; not just for hydrolysis and VFA production, but also for P release and solubilization of WAS P, Mg, Ca, and other cations. Acid+ Digestion Figure 5 shows how Southerly's three AG digesters could be redeployed under an Acid+ configuration. The table also summarizes the role of each tank/stage within the process. BC also developed an EnviroSim BioWin process model of Acid+ implementation for a 20-mgd WWTP with Bio-P. The existing digesters were resized to provide 20-day SRTs at average load (0.07mgd and 38,100ppd at 86% volatile solids, or 'VS'). Acid-phase (Figure 5) and Harvesting Digesters (D2 and D3, in same figure) were sized to provide 1.5-day SRTs at average, sludge feed (QF). Finally, two parallel models were also run for Methane-only (without D1 through D3) and AG (without D2 and D3), both without recycles or recuperative thickening. Each process was run to failure by increasing the feed flow and solids proportionally until the VFA to alkalinity ratio exceeded 0.20. Table 5-3 summarizes the loading at which each process failed as well as the capacity and total tank-volume increases for each process. There are a few aspects of this BioWin modeling that are inconsistent with our team's digestion experience. Because these digestion-model modules are relatively new and rarely calibrated fully to actual digester operation (by liquid-stream process engineers), we expect our Acid+ testing to provide data for first-of-its-kind, digestion-process model calibration at a variety of extreme conditions. This alone will provide tremendous value to the industry. The benefits of this new process are as follows (numbered as a continuation of the earlier AG benefits): - Cost-effective nutrient recovery through production of high-P struvite or brushite products with reduced struvite fouling on downstream piping and equipment. Most other struvite recovery systems target nutrient collection on thickening or dewatering side streams, preventing nutrient recycles that either require retreatment or that may be discharged in the WRRF effluent. - Lowers biosolids P content by 40-60%, which allows for increased per-acre land application rates with greater carbon and more-balanced N benefits for sites with agronomic P limits. - Improves biosolids dewaterability by alleviating cation imbalances, for less polymer and energy. - Increases downstream digestion capacity by up to 160%, with an only 20-25% increase in digester volume (see Table 5-3). This is comparable to capacity increases with commercially available THP systems, without complex mechanical and thermal requirements. - Reduces chemical demand over other struvite-recovery processes.

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

SpeakerFiorino, Dante

Presentation time

9:00:00

9:30:00

Session time

8:30:00

11:15:00

Session number19

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicIntensification, Ohio, Phosphorus recovery; struvite; electrochemical

Author(s)

D. Fiorino

Author(s)D. Fiorino1; D. Wise2; G. Schweinfurth3; J. Willis4; C. Muller5

Author affiliation(s)Brown and Caldwell; 1City of Columbus Department of Public Utilities; 2City of Columbus Department of Public Utilities; 3Brown and Caldwell; 4Brown and Caldwell; 5

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May, 2022

DOI10.2175/193864718825158391

Volume / Issue

Content sourceResiduals and Biosolids

Word count23

I Spy Fugitive Methane: A Look at 3-years of Leak Detection Surveys

Abstract

Bioenergy programs at municipal water resource recovery facilities (WRRF) are centered around anaerobic digestion, beneficial use of biogas, and opportunities for co-digestion. These programs can help to can provide avenue for climate positive action and cost offsets or revenue generation. Although bioenergy programs provide major benefits, they can also be an unsuspecting major source of greenhouse gas (GHG) emissions. Fugitive methane is the unintended release of methane typically from anaerobic digestion and solids handling systems but can also come from upstream processes as well. Fugitive emissions are often one of the sources of GHG emissions from WRRFs along with energy use and nitrous oxide emissions. Methane is a major contributor to climate change, accounting for 45 percent of current net warming. As a potent GHG, methane is 84 times more effective at trapping heat in the atmosphere compared to carbon dioxide over a 20-year timeframe. WRRFs are estimated to contribute 5-8% of global anthropogenic methane emissions (Ocko, 2021). The significance of methane and its impacts on the climate, coupled with burgeoning interest and attention of WRRFs as a source, creates considerable opportunities within the wastewater sector to address both local and global climate action goals by reducing these emissions. The adoption of leak detection and repair (LDAR) programs can provide a means to substantially reduce emissions while addressing odors, safety, asset renewal, and other drivers. This presentation will provide an overview of LDAR programs and summarize data collected from optical gas imaging (OGI) fugitive methane surveys from 15 WRRFs over the course of two and a half years. To date, most of the fugitive emissions detection and quantification efforts have been focused on the oil and gas (O&G), landfill, and mining sectors. Additionally, only the O&G sector have mandates for LDAR programs. A vast majority of WRRFs do not deploy regular leak detection efforts as part of route maintenance or are reliant on rudimentary leak detection methods. New detection technologies and methods developed in O&G provides the significant opportunities to implement effective LDAR programs. Leak detection methods include audio, visual, and olfactory (AVO) inspections, portable monitoring instruments, or OGI cameras. Many of these methods are established as part of the Environmental Protection Agency (EPA) Reference Method 21 (40 CFR Part 60, Appendix A). The direct appropriation of some of these methods by the wastewater sector may present challenges due to the unique nature of emissions from WRRFs. WRRF emissions have high variability, broad range of quantities, and types of leaks that can deviate from O&G calibration and detection settings. However, OGI technology has translated well to its use at WRRFs where it has been effective at detecting biogas leaks and could potentially be a key component of LDAR programs. OGI relies on thermal imaging spectrometry to isolate gases that are invisible to the human eye by detecting the infrared radiation that passes through the gases. As infrared radiation travels through certain gases, energy is absorbed at specific wavelengths and changes the infrared radiation transmittance. The OGI camera is equipped with a spectral filter that limits the type of infrared radiation that can pass into the detector. This spectral filter is designed to uniquely match the gases' infrared fingerprint. A cryogenically cooled detector then translates the signal into a thermographic image of the gas. Many OGI cameras are also capable of quantification or QOGI which allows the camera to compute mass and volumetric flow rates of gases. A Konica Minolta GMP02 OGI camera was used to identify and record methane emissions at solids and liquid treatment processes. Figure 1 depicts the Konica Minolta GMP02 OGI camera and illustrates the process through which OGI detects gases. The fugitive emissions surveys took place between 2022 and 2024 at 15 WRRFs to capture unintended leaks from equipment, structures, piping, and other assets. The following locations were typical of most surveys: - Headworks, preliminary treatment - Aeration tanks and primary clarifiers - Solids thickening - Biogas/natural piping and appurtenances - Biogas system (boilers, condensate traps, co-generation, gas conditioning/upgrading) - Digesters (walls, covers, appurtenances) - Dewatering equipment, building, and cake storage - Odor control Over two hundred emissions leaks were classified in three broad arbitrary categories of small (1 - 200 g CH4/hr), moderate (201 - 1000 g CH4/hr), and large (>1000 g CH4/hr). Quantifications of methane emissions occurred at most locations, but some emissions were qualitatively classified. Photos and video were documented at all leak locations. Example sources of leaks are shown in the following figures. Additional data summaries will be provided in the presentation and the final proceedings. The outcomes of the survey found that the most common sources of leaks included pressure vacuum release valves (PVRV), floating covers, digester cover safety appurtenances, biogas compressors, biogas condensate and drip traps. One of the more common leak points were from PVRVs which were attributed to lack of maintenance, manufacturing quality control issues, and system operating pressure. PVRV are designed to be leak tight up to 75% of the setpoint and less 1 scfm at 90% of the setpoint. However, many of the PVRV leaks reflected greater than 1 scfm of biogas even when below the setpoint. Several plants had significant leaks due to corrosion and failure of the PVRVs while others were venting per normal operation where system pressures exceeded the set point. During the course of the survey, several leaks were corrected by plant staff and resurveyed to verify mitigation of the leaks. When considering methane emissions, they can be classified as either venting and fugitive methane leaks. Venting is the intentional operational and maintenance actions that leads to emissions of methane typically for system operation, safety, and performance. Fugitive methane is the unintended emissions of methane due to damage, wear, corrosion, and human error. Both fugitive leaks and venting can potentially be addressed with design improvements and innovations. Some elements include redesigning digesters for higher pressures allowing for greater buffer between PVRV setpoint and operating pressure. This study indicated that voluntary LDAR programs may be effective at identifying and reducing fugitive emissions. They also play a vital role in ensuring the safety and health of plant staff and reduction of nuisances to the surrounding communities. LDAR programs can lead to considerable cost savings by preventing the loss of biogas. Additional studies are needed to develop the framework of LDAR program included recommended technologies, frequency of inspections (annual, quarterly, monthly), documentation and workflow, and other key factors.

This paper was presented at the WEF Residuals & Biosolids and Innovations in Treatment Technology Joint Conference, May 6-9, 2025.

SpeakerLe, Trung

Presentation time

16:25:00

16:45:00

Session time

13:30:00

16:45:00

SessionCase Studies for Optimizing THP, Dewatering, and Digestion

Session number7

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAnaerobic Digestion, Biosolids, Dewatering Optimization, Energy and Carbon Neutrality, fugitive methane emission, Full-scale Optimization, Greenhouse Gases, Mesophilic Anaerobic Digestion, Odor/Air Emissions, Operations And Maintenance, Process modeling, Reliability, Sludge Digestion, THP, THP, CAMBI

Author(s)

Le, Trung, Cavanaugh, Shannon, Nangle, Tom, Fiorino, Dante

Author(s)T. Le1, S. Cavanaugh1, T. Nangle1, D. Fiorino1

Author affiliation(s)Brown and Caldwell, 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159811

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Next Generation Digestion for the Fugitive Methane Era

Abstract

The Intergovernmental Panel on Climate Change (IPCC) found that anthropogenic methane emissions are responsible for 45 percent of current net warming (IPCC, 2023). The EPA estimates that centralized WWTPs in the United States are responsible for 14 percent of waste methane emissions. At WWTPs, methane emissions are most prevalent in the solids handling areas, as methane is produced as a byproduct from the microbial breakdown of organic waste during anaerobic treatment of wastewater and sludge. Reducing WWTP methane emissions plays a vital role in reducing our near-term greenhouse gas emissions, which is necessary to avoid climatic tipping points and reduce environmental impacts. This manuscript will summarize: 1.Why utilities should care about fugitive methane emissions at their WWTPs. 2.Approaches to identify and quantify sources of fugitive methane emissions at WWTPs. 3.Strategies for mitigating these fugitive methane emissions, and 4.How to fund these mitigation strategies. In addition to the summary, the manuscript will dive into the details on mitigation strategies, specifically: 1.Describing fugitive methane emission pathways around solids handling processes, primarily anaerobic digestion, biogas handling, and digestate processing and storage. 2.How to update our designs and O&M practices to mitigate these emissions. The City of Columbus's (Ohio) is at the forefront of identifying, quantifying, and mitigating fugitive methane emissions. This manuscript will use the work around their Southerly WWTP Bioenergy Project as a case study that other utilities with anaerobic digestion can learn from. The goal is for our industry to design better digestion systems to do our part in mitigating the worst impacts of climate change and provide the best value for our communities. City of Columbus's Southerly WWTP Bioenergy Project The City of Columbus (Ohio) has embarked on a Bioenergy program to transform the solids handling process at the Southerly WWTP (SWWTP). The project includes a 60,000 gallon per day organics receiving facility (ORF) to prepare waste organics for co-digestion, a 6 MG digestion process expansion to increase solids capacity and convert organics and sludge into biogas, and a 8MW cogeneration facility to make renewable electricity and recover heat from the biogas. Further, to expand on the City's cutting-edge work to identify and quantify fugitive methane emissions at the SWWTP, the project includes upgrades to the existing digestion system and redirecting foul air from the solids handling processes to the new waste gas burner facility. These improvements are projected to reduce identified fugitive methane by 91 percent and captures additional biogas for use within the cogeneration facility. Why Care About Fugitive Methane Emissions The capture and utilization of the fugitive methane identified at Columbus' SWWTP is equivalent to taking 18,000 cars off the road and saving the city $350,000 annually in combined heat and power savings that otherwise would have been lost to the atmosphere. Reducing methane emissions also: - Helps meet climate goals -As part of its Climate Action Plan, the City of Columbus (City) has set ambitious goals for the Columbus community to be carbon neutral by 2050, in alignment with the Paris Climate Agreement. An interim goal to reduce GHG emissions by 45 percent by 2030 was set to help meet the 2050 target. - Protects against Future Regulations-The U.S. Environmental Protection Agency (EPA) has moved to include GHGs, particularly methane, as regulated air pollutants under the Clean Air Act. This has led to the development of GHG reduction standards for the power, and oil and gas industries. For example, the Inflation Reduction Act includes provisions that indicate designated petroleum and natural gas facilities must calculate baseline methane emissions and be subject to a fee on excess methane emissions (Murphy, 2022). Similar regulations may eventually be adopted in the municipal wastewater sector. - Improves Public Perception - Methane emissions are gaining additional scrutiny from the public and climate activists. There is currently publicly available satellite imagery that can pinpoint large emitters of methane (including WWTPs) with many more satellites coming online in the next 12-24 months. Proactively identifying and mitigating fugitive methane transforms a negative publicity risk into a positive story of how the city is reducing emissions, improving health, and recovering resources. - Maximizes biogas beneficial use-To ensure the cogeneration facility is sized properly and biogas use, and related renewable energy production is maximized, it is critical to identify locations where fugitive methane can be captured. - Maximizes EPA GHG reduction grants-For the City to position for GHG reduction grants through the Inflation Reduction Act for future improvements, the City needs to justify and demonstrate the need to reduce GHG emissions at SWWTP. - Identify methane leaks posing safety risks-Leaking methane, along with associated constituents in biogas (i.e. hydrogen sulfide), pose a health and safety risk for plant staff. Identifying and mitigating these emissions will reduce the risks of potentially fatal accidents. How to Identify and Quantify Fugitive Methane Emissions Multiple measurement technologies were researched and deployed to identify and quantify fugitive methane emissions at the SWWTP; this included drone flux measurement (DFM), an optical gas imaging (OGI) camera, a gas analyzer, and a biogas capture box. A comparative analysis of the resulting data from these approaches was used to produce the emissions for the SWWTP. As expected, most of the methane emissions were associated with the solids handling parts of the facility, as outlined in Figure 1. How to Mitigate Fugitive Methane Emissions The field investigation helped to identify sources of fugitive methane in the solids handling and treatment processes that are associated with biological activity under anaerobic conditions, entrained biogas in the sludge, and dissolved methane in the sludge. Sources of fugitive methane identified at SWWTP are summarized in Figure 2, and include: - Annular space between floating covers and digester wall - Digester Pressure relief valves - Gaskets of digester cover hatches and manways - Flanges of digester gas piping - Leaks through concrete digester walls - Gas handling equipment - Exhaust stacks of odor control systems serving solids handling processes - Waste gas burners The manuscript will summarize evaluation of different mitigation strategies. The selected improvements share a common theme, which is to: 1.Maximize production and extraction of biogas in the anaerobic digesters, which reduces the potential for biogas to be emitted in downstream solids handling processes. 2.Improve biogas capture of the digestion and biogas systems. Some of the improvements include in the Bioenergy project are: - Improve digester feeding, mixing and withdrawal to maximize biogas production and extraction within the digesters. - Replace floating covers with fixed concrete covers rated for 60-inch water column gas pressure and embedded liner for corrosion protection and gas imperviousness. - Overhaul the biogas handling system to provide a larger delta between the operating pressure range and the safety pressure setpoints (waste gas burner backpressure control valves, pressure relief valves, emergency relief hatches, etc.). - Capturing the solids handling foul gas and combusting it in a vapor combustion unit (VCU), which is uniquely capable of combusting low percent methane gases. - Other miscellaneous advancements (liner penetration details, gasket specifications, instrumentation and control strategies, O&M practices). Most of these improvements have already been implemented and proven effective separately on previous digestion projects. Case studies of some of these examples will be highlighted to make the case that combining these improvements can provide an example of a new standard of care for designing and operating digestion facilities. How to Fund Fugitive Methane Mitigation Improvements A summary of how the Bioenergy project was structured to maximize the potential funding available from the Inflation Reduction Act (IRA); it is estimated that this project will receive over $50M from this program alone. Closing The City of Columbus's (Ohio) is at the forefront of identifying, quantifying, and mitigating fugitive methane emissions. This manuscript will use the work around their SWWTP Bioenergy Project as a case study that other utilities with anaerobic digestion can learn from. The goal is for our industry to design better digestion systems to do our part in mitigating the worst impacts of climate change and provide the best value for our communities.

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

SpeakerNangle, Tom

Presentation time

10:45:00

11:15:00

Session time

08:30:00

11:45:00

SessionGreenhouse Gas Emissions at Wastewater Treatment Plants

Session number11

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicAnaerobic co-digestion, Biogas, fugitive methane emission

Author(s)

Nangle, Tom

Author(s)T. Nangle1, G. Schweinfurth2, D. Fiorino1

Author affiliation(s)Brown and Caldwell 1; City of Columbus 2; Brown and Caldwell 1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159475

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count9

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