Willis, John

John Willis is a speaker at WEFTEC 2026.

Titles from this speaker

Description: A Bigger-Picture Look at Florida's Nutrient-Loading and the Relative Insignificance...

A Bigger-Picture Look at Florida's Nutrient-Loading and the Relative Insignificance of Biosolids-Derived Products

Abstract

The State of Florida suffers from location-specific, surface-water eutrophication that has been principally attributed to excess nutrient loading. The Saint John's River basin and Lake Okeechobee have been noted among others, as problem areas. Excessive nutrient loading to the everglades and seasonal toxic red tides are related problems. In response to these challenges, the Florida Department of Environmental Protection (FDEP) has proposed new Class-B land application rules (FDEP, 2019a) restricting application to below agronomic loading rates for phosphorus (P) and prohibiting application to sites where the water tables encroaches within 15 centimeters of the surface on a seasonal basis. In FDEP's own analysis (FDEP, 2019b) they estimate that between 4 and 10 times more land would be needed to handle the State's current Class-B biosolids production. This paper will provide nutrient accounting for significant sources of nutrients within agricultural and urban settings. These sources include Class-B biosolids land application; Class-AA biosolids (the State of Florida's term for Class-A biosolids that also meet the State's more-restrictive-than-Part-503 metals requirements) that have been registered as 'fertilizers'; other fertilizers; agricultural manures; water resource recovery facilities' (WRRF) surface-water discharges; and WRRF effluent used as reuse water. County-based nutrient loads by source are compared with nutrient removal rates by harvested crops and net over and under loads are identified geographically using color-indexed maps. These combined data suggest that additional regulatory targets will be required if Florida is to solve its surface-water impairment issues, since contributions of nutrients from the regulated sources, namely Class-B biosolids and POTW surface-water discharges represent only 5 to 10% of the total relative Nitrogen (N) and P loads. Finally, while this paper is Florida-specific, many observations are not unique to that state and will have relevant analogs in other geographies. Figure 2 shows an FDEP map (FDEP, 2020) of the state's nutrient impaired waters. Impairment sources shown include nitrogen (N), P, algal mats, and chlorophyll. Highlighted locations include areas immediately offshore from major metropolitan centers, Lake Okeechobee and its surroundings, the gulf offshore from the Everglades, and the Georgia-fed Suwanee and Ochlockonee watersheds, among others. The nutrient sources included in this analysis include the following, in order of decreasing relative significance: 1) Chemical Fertilizers; 2) Carbon-Based Fertilizers, which include Class-AA biosolids; 3) Recovered Manures; 4) Reuse Water; 5) Legume-Fixed Nitrogen; 6) Class-B Biosolids; and 7) Surface Water Discharges & with only some of these covered in this abstract. These nutrient sources and their relative impacts will be detailed in the full paper. For this abstract, the following are of note: 1. Fertilizers. Fertilizer manufacturers are required to report sales of fertilizer to the Florida Department of Agriculture and Consumer Services' (FDACS). Individual manufacturer reports are consolidated by FDACS into a statewide Tonnage Report, by county; data in Table 1 summarize 2018 fertilizer sales. Figures 3A and 3B show a map of Florida with chemical fertilizer purchases by county using the resulting chemical fertilizer loading for N and P, respectively in 2018. The Figure-3 maps are typical of Figures 3 and 4. Each map uses the same color-weighting for each county's annual N loading: ranging from white (representing 0), through yellow (at 6 million pounds per year, 'Mppy'), to red (at 12 Mppy). Similarly, each county's annual P loading is scaled from white (for 0), through yellow (3 Mppy), to red (6 Mppy). The maps further differentiate between predominantly urban counties (those with heavier-weight borders). These 9 most populous counties represent over 58% of the state's population and include: Miami-Dade (2,761,581); Broward (1,951,260); Palm Beach (1,485,941); Hillsborough (1,436,888); Orange (1,380,645); Pinellas (975,280); Duval (950,181); Lee (754,610); and Polk (708,009). 2. Class-AA Biosolids Fertilizers. In the State, Class-A products are registered as fertilizers with FDACS and are no longer subject to FDEP regulation and included in the Tonnage Report. FDCAS rules run contrary to FDEP water-quality objectives however; with requirements that fertilizer N and P labeling amount to 'guaranteed minimums' (that are subject to fines if and only if actual concentrations are found to be below labeled concentrations). As such, FDCAS rules encourage nutrient-loading under-reporting for Class-AA biosolids; and every fertilizer listed in the Tonnage Reports. 3. Class-B Biosolids. Figure 3 shows the loading from Class B biosolids which are centered in two counties immediately south of Orlando & while land application is of little significance elsewhere. These two heavily loaded counties do contribute to Lake Okeechobee's impairment. Class-B biosolids, however, only represent roughly 1/3 of the N and 1/2 of the P applied locally, so that there is more demand than what is met by biosolids alone. 4. WRRF Surface-Water Discharges. Figure 4 shows N and P loads attributable to effluent discharge. As shown by the white maps, it is apparent that the state's nearly uniform 5, 5, 3, and 1 mg/L effluent limits for TSS, BOD, TN, and P, respectively have made this category insignificant with respect to nutrient loading. There are two exceptions to the limits: one in Tampa (for P) and another in Jacksonville (for P and N). 5. State Total Nutrient Loading, Uptake, and Net Loading. Figures 5, 6, and 7 all have different scales than the earlier maps (as shown on each). Figure 4 shows the total nutrient loading from all sources while Figure 5 shows the estimated, potentially-offsetting total crop nutrient uptake. Figure 6 shows the net nutrient overloads (red) or underloading (blue) for each county. SUMMARY This assessment shows how an overall and complete inventory of nutrient loads, while rarely undertaken, can provide insight into the almost certain causes of surface water impairment. It also suggests that geography-specific regulation; and more specifically that stricter regulation of farm entities is warranted, especially for nutrient-overloaded jurisdictions. From the nutrient accounting performed, the wastewater treatment industry is only responsible for 12 to 13% of Florida's N and between 9 and 10% of the State's P, in the forms of surface-water discharges, Reuse Water, Class-B Biosolids and Class-AA Biosolids-Derived Fertilizers. The industry has been highly regulated for decades and has performed very well. Finally, to truly address eutrophication and impaired waters in Florida, it is suggested that the commercial fertilizer and farm industries be monitored closely and potentially regulated to ensure that their contributions to nutrient loading are better understood and then almost certainly curtailed on specific sites, as warranted. Additionally, between one quarter and one third of chemical fertilizer use occurs in Florida's 9 most-populous urban counties (although there is considerable agricultural activity in some of these counties that would reduce the loading attributable to the 'general public'). Creative options are similarly warranted to limit what the general public can buy and apply in specific geographies where runoff contributes to surface-water impairment. The paper discusses these and other issues within Florida. Opportunities for improving the State's surface water quality and regulatory framework are also discussed.

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

SpeakerWillis, John

Presentation time

14:30:00

15:00:00

Session time

13:30:00

16:45:00

Session number15

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicAgriculture, Biosolids, nutrients

Author(s)

J. Willis

Author(s)J. Willis1; T. Chouinard2; R. Gaylord3

Author affiliation(s)Brown and Caldwell; 1Brown and Caldwell; 2Residuals and Biosolids Speaker; 3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158437

Volume / Issue

Content sourceResiduals and Biosolids

Word count14

A Bigger-Picture Look at Florida's Nutrient-Loading and the Relative Insignificance of Biosolids-Derived Products

Abstract

The State of Florida suffers from location-specific, surface-water eutrophication that has been principally attributed to excess nutrient loading. The Saint John’s River basin and Lake Okeechobee have been noted among others, as problem areas. Excessive nutrient loading to the everglades and seasonal toxic red tides are related problems. In response to these challenges, the Florida Department of Environmental Protection (FDEP) has proposed new Class-B land application rules (FDEP, 2020) restricting application to below agronomic loading rates for phosphorus (P) and prohibiting application to sites where the water tables encroach within 15 centimeters of the surface on a seasonal basis. In FDEP’s own analysis (FDEP, 2019) they estimate that between 4 and 10 times more land would be needed to handle the State’s current Class-B biosolids production. This paper provides nutrient accounting for significant sources of nutrients within agricultural and urban settings. These sources include Class-B biosolids land application; Class-AA biosolids (the State of Florida’s term for Class-A biosolids that also meet the State’s more-restrictive-than-Part-503 metals requirements) that have been registered as “fertilizers”; other fertilizers; agricultural manures; legume “fixing” of nitrogen (N); publicly owned treatment works’ (POTW) surface-water discharges; and POTW effluent used as reuse water. The overall nutrient loads are compared with nutrient removal rates by harvested crops and net over and under loads are identified on a county-by-county basis. These combined data suggest that additional regulatory targets will be required if Florida is to solve its surface-water impairment issues, since contributions of nutrients from the regulated sources, namely Class-B biosolids, POTW effluent, and reuse water are inconsequential (only 5 to 10% of the total) relative to the overall mass nutrient loads. Finally, while this paper is Florida-specific, many observations are not unique to that state, and will have relevant analogs in other geographies.

Florida’s Governor recently signed new Class-B Biosolids Rules adding agronomic-phosphorus-loading limits and prohibiting use on seasonally-high-groundwater sites (FDEP estimates 4 to 10 times more required than currently-permitted land) drove this review. This paper provides a unique overview of all major nitrogen and phosphorus sources from wastewater sources (biosolids, reuse and surface discharge), agriculture (manures from CAFOs and grazing livestock and legume-fixed nitrogen), and purchased fertilizers – and compares by-entity-type-controlled loading to crop uptake to make a case that regulation of agriculture is required to ever solve the State’s surface water impairment, cyanobacteria, and red tide public-health hazards

SpeakerWillis, John

Presentation time

14:36:00

14:58:00

Session time

13:30:00

15:00:00

SessionLess Nutrient Loading and Phos-For-Us

Session number311

TopicNutrients, Policy and Regulation, Watershed Management, Water Quality, and Groundwater

Author(s)

John Willis

Author(s)T. Chouinard3; R. Gaylord4; J.L. Willis1; J.B. Barksdale2;

Author affiliation(s)Brown and Caldwell, Atlanta, GA1Carollo Engineers, Tampa, FL 2Brown and Caldwell, Andover, MA3Woodard and Curran, Orlando, FL4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825158054

Volume / Issue

Content sourceWEFTEC

Word count14

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: Advanced Quantification of Fugitive Methane Emissions in Wastewater Treatment...

Advanced Quantification of Fugitive Methane Emissions in Wastewater Treatment Plants

Abstract

Introduction
Greenhouse gas (GHG) emissions, such as carbon dioxide (CO2) and methane (CH4), represent a major contributor to climate change with significant environmental implications (Gautam et al., 2021). These emissions are produced from different anthropogenic activities, including wastewater treatment plants (WWTPs) (Varon et al., 2021). CH4 emissions are particularly critical due to its high global warming potential. In WWTPs, CH4 is generated during the biological processes that involve breaking down the organic matter during anaerobic digestion (Elsayed et al., 2024). A key challenge facing methane quantification in WWTPs is its fugitive nature. While leakage from anaerobic digesters can be a key hotspot, there might be additional unexpected sources of CH4 emissions that may contribute to the overall emissions from these WWTPs. As these emissions can be episodic and location-specific, multi-level sensing is essential for capturing the temporal and spatial emission patterns and variabilities from these different sources. Therefore, the use of advanced sensing technologies, such as ground and drone-mounted sensors, has been gaining greater attention during recent years. These technologies generally assist in more precise and continuous monitoring, allowing for effective detection of fugitive methane emissions and identification of the hotspots.

Objectives
The main objectives of the current study are to: (1) demonstrate the employment of multi-level sensing techniques to monitor the fugitive methane emissions from WWTPs using ground sensors, drone, and Optical Gas Imaging (OGI) camera; (2) identify the hotspots of methane emissions within the wastewater treatment facility based on the deployed sensing techniques; and (3) determine the suitability and applicability of each sensing technique in detecting and quantifying methane emissions from the WWTP.

Methods
In the current study, sixteen ground sensors were installed in a Canadian WWTP with typical configuration to continuously monitor the fugitive methane from the treatment processes for more than five months. In addition, drone and OGI sensing campaigns were carried out to determine detailed insights about the methane emissions from different treatment processes. During the campaign, the drone was flown to isolate each treatment process through creating flight paths upwind and downwind each process and building. The drone featured a quantification sensor (i.e., open-path laser spectrometer (OPLS)) that can detect methane levels as low as 10 parts per billion (ppb). Moreover, a hand-held OGI camera was used to access the areas that cannot be assessed using the drone including the indoor spaces and chambers.

Results
Based on the drone and OGI campaigns, the anaerobic digesters, gas burner facility, and sludge handling facilities yielded high emissions that ranged from 2 to about 20 kg-CH4/hr based on wind characteristics. For example, the anaerobic digesters had an emission rate of approximately 9 kg-CH4/hr. (Fig. 1a). Interestingly, additional hotspots for methane emissions were identified during the campaigns. For example, the primary treatment process emitted approximately 8 kg-CH4/hr. More surprisingly, it was observed that there were some methane emissions around the aeration tanks where the methane emission rate was approximately 4 kg-CH4/hr/tank. (Fig. 1b).

A major limitation in drone-based measurements is its dependence on wind conditions. In cases where very slow winds or inconsistent/turbulence in wind directions, drones' measurements become invalid and inaccurate. In such a case, the use of OGI camera was more reliable which underscores the value of the adopted multi-level sensing approach. As shown in Fig. 2, a major hotspot in sludge holding tanks with more than 5 kg-CH4/hr was observed by the OGI camera, while multiple drone attempts failed due to the very slow wind conditions.

Using the ground sensors, it was observed that there are multiple hotspots for methane emissions within the WWTP. For example, the average methane concentration over the observation period ranged from 7.0 to 11.0 ppm for the sensors surrounding the aeration tanks (Fig. 3), indicating high methane emissions which agrees with the observations of the OPLS drone (Fig. 1b). The on-going research focuses on converting the time-series of methane concentrations into emissions which can assist in better correlation with the other sensing techniques (e.g., OGI camera).

Conclusions
The results of this study showed different methane hotspots near the primary tanks, aeration basins, sludge processing, and anaerobic digestion units. This encompasses both anticipated and unexpected emissions sources which can enhance our understanding about the sources of fugitive methane emissions in WWTPs. The advantages of the aerial drone, coupled with the OGI camera, allowed for rapid and comprehensive coverage of the facility, providing accurate spatial emission data. The ground sensors generally can underscore the variability of methane emissions and emphasize the importance of continuous monitoring to capture short-term spikes and long-term trends with high affordability compared to other sensing techniques. Ultimately, employing different sensing techniques can enhance our understanding about the methane emissions from WWTPs and assist in recommending effective emission mitigation strategies in the operation and management of these systems.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

09:00:00

09:15:00

Session time

08:30:00

10:00:00

SessionDecarbonizing Water: Across Space and Time - Techniques for CH4 and N2O Monitoring

Session locationMcCormick Place, Chicago, Illinois, USA

TopicBiogas & Energy Recovery

Author(s)

Elsayed, Ahmed, AlSayed, Ahmed, Abdelrahman, Omar, Khalil, Mostafa, Kakar, Farokh Laqa, Bell, Katherine, Le, Trung, Cavanaugh, Shannon, Willis, John, Elbeshbishy, Elsayed

Author(s)A. Elsayed1, A. AlSayed2, O. Abdelrahman1, M. Khalil3, F. Kakar6, K. Bell5, T. Le6, S. Cavanaugh6, J. Willis6, E. Elbeshbishy1

Author affiliation(s)Toronto Metropolitan University1, Northwestern University2, Stantec Inc.3, Sundt4, Hazen and Sawyer5, Brown and Caldwell6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825159981

Volume / Issue

Content sourceWEFTEC

Word count11

Description: Advancing Our Understanding of Sewer Methane: Early Results from Sewer Methane...

Advancing Our Understanding of Sewer Methane: Early Results from Sewer Methane Methods for Everyone (WRF #5220)

Abstract

This technical session will provide a forum for knowledge exchange in our understanding and modeling of sewer generated methane that has occurred within the last 1-2 years. Speakers will discuss lab/pilot research, advanced modeling, and full-scale measurement campaigns that are improving our understanding of the key contributing factors to methane generation in sewers, how to quantify it, and where our industry should continue to put our future research efforts.

This paper was presented at WEFTEC 2026 in New Orleans, Louisiana.

Presentation time

13:30:00

15:00:00

Session time

13:30:00

15:00:00

SessionAdvancing Our Understanding of Sewer Methane

Session locationErnest N. Morial Convention Center

TopicCollection Systems

Author(s)

Willis, John, Nielsen, Asbjorn, Gutierrez, Oriol, Cavanaugh, Shannon

Author(s)J. Willis1, A. Nielsen2, O. Gutierrez3, S. Cavanaugh1

Author affiliation(s)Brown and Caldwell, 1Aalborg University, 2Catalan Institute for Water Research, 3Brown and Caldwell, 1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2026

DOI10.2175/193864718825160341

Volume / Issue

Content sourceWEFTEC

Word count17

Description: Beyond One-Size-Fits-All: How Operational Patterns and Compliance Limits Shape...

Beyond One-Size-Fits-All: How Operational Patterns and Compliance Limits Shape Fugitive GHG Emission Variability in Wastewater Treatment Plants

Abstract

Introduction:
Amid the accelerating impacts of climate change, the urgent need to mitigate greenhouse gas (GHG) emissions is more critical than ever, yielding commitments from developed countries aimed at achieving net-zero emissions by 2050. Wastewater treatment plants (WWTPs), a major source of direct emissions, contributes approximately 5% of global non-CO2 GHG emissions, largely in the form of methane (CH4) and nitrous oxide (N2O)[1]. Thus, there has been growing academic and industrial interest in the quantification of the direct, or Scope 1, emissions from WWTPs [2]. The standard method for estimating GHG emissions relies on the current IPCC guidelines, which use a simplified global emission factor (EF). However, this approach lacks the granularity required to capture the actual dynamics of GHG emissions from WWTPs [3]. To better quantify GHG emissions, prior studies have focused on investigating GHG emissions in relation to adopted technologies, received wastewater flows, and/or treatment level [4,5].

Therefore, the current study leverages a multi-level GHG quantification framework to demonstrate how operational patterns, compliance limits, and influent characteristics not only influence the total emissions but also their profile and distribution within the plant. This work is part of an ongoing NSERC project monitoring GHG emissions from Canadian WWTPs in which a multi-level approach is utilized combining various advanced measurement techniques, including gas/liquid sensors, optical gas imaging (OGI), drone-based sensing, aircraft imaging, and satellite imaging.

Methods:
The Canadian wastewater treatment plant featured in this study operates with a typical activated sludge treatment configuration. To monitor nitrous oxide, two Unisense® sensors were strategically installed to capture possible variation across the aeration tank. Methane (CH4) emissions were quantified using 16 ground-based sensors, complemented by a 3-day intensive measurement campaign employing drone-based and OGI techniques.

Results and discussion:
For over six months, liquid N2O concentrations were monitored at two locations in the aeration basin. The system typically is operated as a step-feed, with primary effluent entering the bioreactor through eight gates distributed along the aeration tank and regulated via gate openings. During the study, the reactor was tested under various modes; for example, Figure 1 shows the N2O emissions during typical operation with standard gate settings. Median daily N2O emissions were recorded at only 2.91 KgN-N2O/day, with occasional spikes exceeding 10 KgN-N2O/day. This corresponds to an N2O emission factor (EF) of 0.005 ± 0.0012 kg N2</Sub>O-N per kg TN, significantly lower than the IPCC EF of 0.016 kg N2O-N per kg TN [6]. This reduced EF can be attributed to the plant's compliance limits, which do not require nitrogen removal. Accordingly, the reactor operated near nitrifier washout conditions, with an average SRT of 3.4 days and median ammonia removal of less than 25% (Figure 1). It is worth noting that while non-BNR activated sludge systems typically exhibit higher emissions [5], the lower emissions observed in this plant can be attributed to operation at a washout SRT.

The average methane emissions from the plant were quantified at 1385 ± 871 kgCH4/day. This corresponds to 3.9—4.4 gCH4/m3 of treated wastewater and 3.2—3.5% of the influent COD load. These values are relatively high but fall within the typical range reported in the literature [4]. The distribution of methane emissions across the plant revealed unexpected insights. As shown in Figure 2, the aeration tanks and primary clarifiers were the largest contributors, accounting for approximately 60% of the total methane emissions. In contrast, digesters and gas burners combined contributed only 25%. The use of a handheld OGI camera proved instrumental in diagnosing emission sources and quantifying emissions from locations where drone-based measurements were unreliable due to adverse wind conditions. The handheld camera confirmed low emissions from the digesters, with no detectable leaks from covers or structural cracks. However, leaks detected in the dewatering building contributed approximately 6% of the plant's total methane emissions.

The resulting total daily GHG emissions of the plant are estimated to be equivalent to 47.727 metric tonnes of CO2. Interestingly, as shown in Figure 3, methane constituted more than 80% of the plant's emissions. This finding contrasts with typical literature reports, where N2O often accounts for more than 50% of plant GHG emissions [3,7]. This divergence can be attributed to (i) compliance limits that do not require ammonia removal, (ii) operational practices such as TWAS return and operation at a short sludge age, which promotes nitrifier washout, and (iii) the received influent, which contained elevated dissolved methane and high TSS concentrations.

Conclusion:
This study demonstrates how influent characteristics, operational patterns, and compliance limits shape GHG emissions in WWTPs. Methane contributed over 80% of total emissions, with aeration tanks and primary clarifiers identified as major sources-contrasting with typical findings where N2O predominates. These results highlight the importance of site-specific GHG monitoring and tailored mitigation strategies for effective emissions reduction in wastewater treatment.

This paper was presented at WEFTEC 2025, held September 27-October 1, 2025 in Chicago, Illinois.

Presentation time

13:30:00

13:40:00

Session time

13:30:00

15:00:00

SessionDecarbonizing Water: GHG Measurement vs Estimates

Session locationMcCormick Place, Chicago, Illinois, USA

TopicClimate Change Adaptation and Resilience

Author(s)

AlSayed, Ahmed, Elsayed, Ahmed, Khalil, Mostafa, Zaghloul, Mohamed, Kakar, Farokh Laqa, Bell, Katherine, Willis, John, Elbeshbishy, Elsayed

Author(s)A. AlSayed1, A. Elsayed2, M. Khalil2, M. Zaghloul3, F. Kakar4, K. Bell4, J. Willis4, E. Elbeshbishy2

Author affiliation(s)Northwestern University1, Toronto Metropolitan University2, United Arab Emirates University3, Brown and Caldwell4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2025

DOI10.2175/193864718825160134

Volume / Issue

Content sourceWEFTEC

Word count18

Description: Biogas Harvester Recovers Dissolved Biogas for Energy Production, GHG Reduction, and...

Biogas Harvester Recovers Dissolved Biogas for Energy Production, GHG Reduction, and H2S Collection

Abstract

KEY TAKEAWAY
Biogas Harvester, when installed to treat raw sewage upstream of a pumping station or WRRF could recover more biogas energy and virtually eliminate fugitive CH4, H2S, and other volatile sulfur compounds released during wastewater collection and treatment or during digested-biosolids dewatering. With less H2S, worker safety is improved, and headworks/other equipment would last much longer even without odor control. As a final benefit, almost all dissolved CH4 would be recovered, solving an identified challenge for anaerobic-mainstream sewage treatment, enabling use of such industry-transforming processes.
INTRODUCTION
#A Water Research Foundation (WRF) project (#5045) will test a new process called 'Biogas Harvester' (also 'BH', patent pending) for extraction of dissolved gasses from sewage and sludge flow streams in conveyance systems and at Water Resource Recovery Facilities (WRRF). The demonstration, sited at Miami-Dade Water and Sewer Department's (WASD) Central District Wastewater Treatment Plant (CDWWTP) is scheduled for testing during the winter of 2021/22. BH uses a primed siphon (shown schematically in Figure 1) to reduce the headspace pressure at its apex to between 0.3 bar of absolute pressure [bar(a)] and a complete vacuum: 0.0 bar(a). The process is predicted to reduce the concentration of dissolved gases to between 10 and 30% of saturation at ambient conditions (or nominally 1.01 bar(a) at the test site). BH is intended to address a variety of needs within the centralized wastewater-treatment industry and other sectors. More specifically, the following primary applications are envisioned: 1. On Raw Sewage upstream of Pumping Stations or Preliminary/Primary Treatment. BH application at these locations would collect collection-system-produced methane (CH4) for mitigation of direct greenhouse gas (GHG) releases (Primary Author, 2017); offering a extremely-easy mitigation approach to the industry's likely largest (albeit unacknowledged) source of Scope-1 GHG emissions. Additionally, dissolved hydrogen sulfide (H2S) concentrations would be reduced to levels which should eliminate the need for odor control, improve worker safety, and dramatically extend the useful life of installed equipment. 2. On Digested Sludge/Biosolids. Biosolids discharged from anaerobic digesters are saturated or supersaturated with CH4 (Primary Author, 2018) which is largely released during storage or dewatering. 3. Mainstream Anaerobic Treatment Processes. Mainstream anaerobic treatment system [e.g., up-flow anaerobic sludge blankets (UASB), up-flow anaerobic filters (UAF), and anaerobic membrane bioreactors (An-MBR)] research has identified collection of dissolved CH4 from process effluent as a major challenge to the otherwise GHG-reducing benefits of these processes.
DEMONSTRATION DETAILS FOR CDWWTP
The 3D design of the BH demonstration facilities was completed in June 2021 and parts have been on order since that time. The team is awaiting delivery of poly-vinyl chloride (PVC) pipe components that have been delayed by supply-chain issues. Otherwise, all mechanical and instrumentation components are on site and assembly is planned for the end of 2021 or early in 2022; with commissioning and testing beginning once the system is assembled. Figure 2 shows an isometric of the 4-inch, flow-metered, supply piping to the BH manifold located on top of CDWWTP Headworks #2. The 4-inch line is tapped off the crown of a 54-inch forcemain that crosses Biscayne Bay from Miami Beach. Free gases are expected and will be collected at a simulated forcemain high point; collected free gas is conveyed in 1Â½-inch PVC piping and driven under slightly negative gauge pressure by a vacuum pump on the west side of Headworks #2 (shown in Figure 3). Figure 3 depicts other details to the immediate east of the Headworks #2 building while Figure 4 shows an enlarged view of the roof, BH manifold, and connecting piping. The following aspects are also shown: - Two biogas monitoring stations that are under positive pressure with: sample collection taps, flow meters, and insertion taps for biogas-quality instrumentation. Each monitoring station discharges collected gas at a vent that extends above the building roof. - A progressive cavity pump located within the building will prime the BH and collect the formerly dissolved biogas recovered by the BH. Once the siphon is primed, the required pumping energy is dictated by the energy required to compress the collected biogas from 0.2 bar(a) back to atmospheric pressures or ~1.05 bar(a), but because the mass of the biogas is low, power draw less than 0.25 Hp is expected. - A third pump, a small centrifugal rated at approximately 100gpm at 30 feet of head, is located downstream of the biogas harvester, and is intended to move more flow through the BH without increasing the pressure at the top of the manifold. This pump can either be used or bypassed. - Sewage samples can be collected after free gas removal but under positive gauge pressure in the vault with the 54-inch forcemain and after BH treatment and discharge from the small motive centrifugal pump described above. - Views of the roof show a straight section of hard-piped approach to the BH. A second pipe alignment with multiple 90-degree bends is also shown; this second pipe section would replace the straight section for testing of how additional approach turbulence affects BH performance.
SUMMARY
The testing is planned to take less than one month after the demonstration system has been assembled. As such, it is envisioned that testing results will be shared. The value and impact of this innovation for GHG-emissions reduction, odor prevention, worker safety, and increased equipment longevity should be significant. The invention also solves a critical challenge to mainstream anaerobic sewage treatment â€“ enabling that field of study's implementation which should be disruptive, but in only the very best possible way!

Biogas Harvesters use extreme vacuums to 'boil off' dissolved gases from wastewater flows. Application to sewers or headworks collect H2S and CH4 and can thereby eliminate need for odor control, allow extended equipment life, improve safety, enhance renewable biogas recovery, and eliminate fugitive GHGs. They can solve similar issues for digested biosolids dewatering and mainstream-anaerobic effluent. Status and results from a WRF demonstration at Miami-Dade's CDWWTP are discussed.

SpeakerWillis, John

Presentation time

16:30:00

16:55:00

Session time

15:30:00

17:00:00

TopicIntermediate Level, Energy Production, Conservation, and Management, Facility Operations and Maintenance, Municipal Wastewater Treatment Design

Author(s)

Willis, John

Author(s)John Willis1; Ashwin Dhanasekar2; Robert Fergen3; Debbie Griner3; Melissa Jauregui1; Sydney Salit1

Author affiliation(s)Brown and Caldwell1; Water Research Foundation (WRF2); Miami-Dade Water and Sewer Department3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158739

Volume / Issue

Content sourceWEFTEC

Word count14

Description: Continuous Monitoring of Fugitive Methane in Wastewater Treatment Plants Using...

Continuous Monitoring of Fugitive Methane in Wastewater Treatment Plants Using Ground Sensors

Abstract

Introduction Greenhouse gas (GHG) emissions, primarily comprising carbon dioxide (CO2), methane (CH), and nitrous oxide (N2O), are a major contributor to climate change, driving global warming and environmental instability (Gautam et al., 2021). These gases originate from various human activities, including energy production, transportation, agriculture, oil and gas industry, wastewater treatment, and waste management (Varon et al., 2021). Among these sources, methane is particularly potent, having a global warming potential significantly higher than CO2 over a 20-year period. This makes methane emissions a critical target for mitigation efforts, as reducing them can have an immediate impact on curbing climate change and its negative influence on the environment (Liu et al., 2019). Wastewater treatment plants (WWTPs) are considered an active source of GHG emissions, especially methane, which is generated during the biological processes that involve breaking down the organic matter during the anaerobic digestion processes (Khalil et al., 2024). There are multiple key emission hotspots within WWTPs including the sludge treatment areas, anaerobic digesters, and equalizer tanks, where anaerobic conditions can lead to significant methane release. In addition, there might be additional unexpected sources of GHG emissions that may contribute to the overall emissions from these WWTPs such as aeration tanks. As these emissions can be episodic and location-specific, continuous monitoring is essential for capturing real-time data on emission patterns and variabilities. Despite its significance, a major limitation in the wastewater sector is developing an affordable and continuous methane monitoring systems. Therefore, the use of advanced sensing technologies, such as ground and drone-mounted sensors, has been gaining greater attention during recent years. These technologies enable more precise and continuous monitoring, allowing for effective detection of fugitive methane emissions and identification of the hotspots that might otherwise go unnoticed. Continuous monitoring not only provides critical insights into emission dynamics but also supports timely interventions, helping to reduce the carbon footprint of WWTPs and contribute to broader climate goals. Objectives The main objectives of the current study are to: (1) install a group of ground sensors to isolate the methane emissions from different wastewater treatment processes; (2) identify the hotspots of methane emissions within the wastewater treatment facility based on continuous timeseries of fugitive methane emissions from different sources; and (3) compare the methane emissions from the ground sensors with other sensing technologies such as drone-based techniques. Methods and Materials In the current study, 16 ground sensors were installed in a local wastewater treatment facility (WWTF) in Ontario, Canada. The WWTF comprises the typical treatment processes including the primary and secondary treatment, anaerobic digesters, and solids management facilities. In addition, this WWTF receives high organic loading rates which can contribute to the fugitive methane emissions. The ground sensors were distributed around the treatment processes and building to continuously monitor the fugitive methane from these processes. For example, four ground sensors were installed around the aeration tanks to continuously monitor the methane concentrations and emissions from the basins. It should be noted that the observation period started in June 2024 where the ground sensors observed the methane concentrations on a 15-minute interval. Besides the ground sensors, a drone and Optical Gas Imaging (OGI) sensing campaigns were carried out in the WWTF in Summer 2024 to compare the methane concentrations and emissions from different monitoring levels including the ground and aerial sensing techniques. Results According to the preliminary insights from the time-series of methane concentrations using the ground sensors, it was observed that there are multiple hotspots for methane emissions within the WWTF. The average methane concentration at each ground sensor varied according to the location of sensor, the isolated process, and wind properties that play a crucial role in conveying the methane plume. For example, the average methane concentration over four months (i.e., from beginning of June until the end of September) ranged between 7.2 to 11.4 ppm for the sensors surrounding the aeration tanks (Fig. 1), indicating that these basins are a potential source of methane emissions. In addition, the average methane concentration was approximately 10.3 ppm near the primary clarifiers (Fig. 2a). Moreover, the range of the average methane concentration of the sensors installed around the sludge treatment facilities was 5.7 -- 11.2 ppm. Based on these observations, it can be emphasized that most of the treatment processes are considered hotspots for fugitive methane emissions with the WWTF. These findings were validated using the drone and OGI sensing approaches where the drone flights and OGI camera confirmed the locations of the hotspots for emitting methane within the treatment processes (Fig. 2). Conclusions and summary The deployment of ground-based sensors for the quantification and detection of fugitive methane emissions at the WWTF provided valuable insights into the spatial and temporal distribution of emissions. The sensors, strategically placed near the expected and unexpected emitters such as sludge handling units, anaerobic digesters, and aeration tanks, captured real-time data on methane concentrations, enabling the identification of persistent emission sources. Over the monitoring period, fluctuations in emission levels were observed that were linked to the operational activities and environmental conditions. This data underscored the variability of methane emissions and emphasized the importance of continuous monitoring to capture short-term spikes and long-term trends. Ultimately, the ground sensor campaign highlighted the potential for such technology to complement aerial sensing, providing granular, location-specific data critical for effective emission mitigation strategies in wastewater treatment operations.

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

SpeakerElsayed, Ahmed

Presentation time

09:30:00

09:50:00

Session time

08:30:00

10:00:00

SessionDrones, Satelites, Sensors, Oh My!: Advances in Fugitive Methane Monitoring

Session number11

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicBiosolids To Energy, Climate Change Mitigation, Energy and Carbon Neutrality, Greenhouse Gases, Odor/Air Emissions, Regulatory Requirements, Sensors, wastewater

Author(s)

Alsayed, Ahmed, Elsayed, Ahmed, Abdelrahman, Omar, Khalil, Mostafa, Zaghloul, Mohamed, Kakar, Farokh, Bell, Katherine, Le, Trung, Willis, John, Elbeshbishy, Elsayed

Author(s)A. Elsayed1, A. Alsayed2, O. Abdelrahman1, M. Khalil1, M. Zaghloul3, F. Kakar4, K. Bell4, T. Le4, J. Willis4, E. Elbeshbishy1

Author affiliation(s)Toronto Metropolitan University, 1Northwestern University, 2United Arab Emirates University, 3Brown and Caldwell, 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159805

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Description: Drone-Based Imaging and Sensing: Quantification of Fugitive Methane Emissions from...

Drone-Based Imaging and Sensing: Quantification of Fugitive Methane Emissions from Full-Scale Wastewater Treatment Facility

Abstract

Introduction Greenhouse gas (GHG), such as methane (CH4), nitrous oxide (N2O) and hydrofluorocarbons (HFCs), emissions are considered a major contributor to global climate change which has a substantial impact on the public and environmental health (Hopwood et al., 2008; Gautam et al., 2021). Multiple sources, including the Intergovernmental Panel on Climate Change (IPCC), highlighted that global temperatures have increased between 0.3 - 0.74 degrees Celsius in the past century due to the natural and anthropogenic sources including the GHG emissions (Solomon et al, 2010; Liu et al., 2019). Methane as a GHG has been reported to have 27-29 times higher global warming potential compared to carbon dioxide. According to EPA's 2022 report, the wastewater sector is the fifth largest methane source. For example, the methane emissions from domestic sewage in WWTPs can reach up to 25 Tg-CH4/yr (Wallington et al. 2019). Such estimations were developed based on top-down approaches where average emission factor is used to estimate such emissions. However, a major contributor to such emissions is direct process and fugitive methane emissions such as anaerobic digesters and waste gas burners. Such emissions may vary significantly according to operational conditions and infrastructure integrity. Moreover, there might be additional unexpected sources of GHG emissions that may contribute to the overall emissions from WWTPs. Therefore, the application of sensing technologies can aid in accurate quantification of the methane emissions from the WWTPs where these emissions can be correlated to specific treatment processes. Objectives In the current study, the main objectives are to: (1) utilize a multi-platform sensor approach to detect and quantify the fugitive methane emissions from a WWTP using drone and Optical Gas Imaging (OGI) sensing; (2) identify the hotspots of methane emissions within the wastewater treatment facility based on these different sensing technologies; and (3) determine the overall methane emissions from the treatment facility. Methods and Materials A drone and OGI sensing campaigns were carried out in a local WWTP in Ontario, Canada during the Summer of 2024. The WWTP contains the typical treatment processes including the primary treatment, secondary treatment, anaerobic digesters, biosolids loading facilities, and sludge settling tanks. Worth noting, this WWTP receives high organic loading rates which can significantly increase the methane emissions from the WWTP. During the campaign, the drone was flown to isolate each treatment process through creating flight paths upwind and downwind each process and building. These flight paths are known as the wind curtains where they are selected to be perpendicular on the wind direction at different altitudes around the potential process sources. To effectively capture the methane plumes from emission sources, the wind curtains were flown between 30 to 150 ft upwind and downwind the potential sources and treatment processes. The drone sensing approach generally features a quantification sensor (i.e., open-path laser spectrometer (OPLS)) that can detect methane levels as low as 10 parts per billion (ppb). In general, the flight conditions of the drone require a wind speed range of 4 and 20 mph while maintaining a consistent drone speed approximately 3.0 to 4.0 mph for optimal performance. In addition, an OGI camera was mounted on the drone for detecting the potential leakage within the treatment processes. A hand-held OGI camera comprising a cooled infrared sensor was used to access the areas that cannot be assessed using the drone including the indoor spaces and chambers. The OGI camera detects the methane using three factors: the infrared absorption of the gas aligning with the camera's spectral response, the temperature difference between the gas and background, and the gas concentration meeting the camera's sensitivity threshold. The OGI camera is connected with a gimbal which enables the OGI camera to rotate freely without restrictions. Results According to the outcomes of the drone and OGI campaigns, it was found that there are multiple hotspots for methane emissions within the WWTP. For example, the primary treatment process emitted approximately 8.0 kg-CH4/hr. This can be referred to the high organic loads received in such a treatment plant and mixing primary sludge with thickened waste activated sludge. In addition, the anaerobic digesters, gas burner facility, and sludge handling facilities yielded high emissions that ranged from 2.0 to 19.8 kg-CH4/hr. based on the sludge treatment stages and wind characteristics. For example, the anaerobic digesters had an emission rate of approximately 8.9 kg-CH4/hr. (Fig. 1a). Interestingly, considerable methane emissions were observed around the aeration tanks where the methane emission rate was approximately 3.8 kg-CH4/hr. (Fig. 1b). The activated sludge process in this plant does not entail any anoxic or anaerobic zones. Hence, the high emissions from the aeration basins can be attributed to unideal aeration and mixing conditions (coarse bubble aeration used for mixing and aeration), and/or the circulation of the centrate which is anticipated to be saturated with dissolved methane. A major methane emission spot was found to be the sludge holding tanks. Methane concentrations from such tanks reached more than 60 ppm, highlighting a major fugitive methane emission in the facility. However, there were some challenges in estimating the actual methane emission rates due to low wind speed at this area which ranged between 0.7 to 2.0 m/s that were lower than the recommended values of wind speed for accurate quantification of methane emissions using drone-based sensing techniques. In general, these hotspots were also surveilled using either the drone-based or hand-held OGI camera where the methane plumes were detected and recognized (Fig. 2). Conclusions and summary The current study aimed to accurately quantify the methane emissions from a WWTP using drone-based sensing approach to assist in calculating the methane emissions rates from various treatment processes. The methane emission quantification campaign at the WWTP demonstrated the efficacy of drone-based sensing combined with OGI cameras for detecting and measuring fugitive methane emissions where it provided important insights into the interplay between the treatment processes and methane emissions. The results showed significant methane hotspots near the primary tanks, aeration basins, sludge processing and anaerobic digestion units. This encompasses both anticipated and unexpected emissions sources which can enhance our understanding about the sources of fugitive methane emissions in WWTPs. The advantages of the aerial drone, coupled with the OGI camera, allowed for rapid and comprehensive coverage of the facility, providing accurate spatial emission data. Overall, the campaign underscored the potential of drone and OGI technology as a powerful tool for enhancing fugitive methane monitoring and supporting emission reduction strategies in wastewater operations.

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

SpeakerAbdelrahman, Omar

Presentation time

08:50:00

09:10:00

Session time

08:30:00

10:00:00

SessionDrones, Satelites, Sensors, Oh My!: Advances in Fugitive Methane Monitoring

Session number11

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicBiosolids To Energy, Climate Change Mitigation, Energy and Carbon Neutrality, Greenhouse Gases, Odor/Air Emissions, Regulatory Requirements, Sensors, wastewater

Author(s)

Abdelrahman, Omar, Elsayed, Ahmed, Alsayed, Ahmed, Khalil, Mostafa, Zaghloul, Mohamed, Kakar, Farokh, Bell, Katherine, Le, Trung, Willis, John, Elbeshbishy, Elsayed

Author(s)O. Abdelrahman1, A. Elsayed1, A. Alsayed 2, M. Khalil1, M. Zaghloul3, F. Kakar4, K. Bell4, T. Le4, J. Willis4, E. Elbeshbishy1

Author affiliation(s)Toronto Metropolitan University, 1Northwestern University, 2United Arab Emirates University, 3Brown and Caldwell, 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159804

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count15

Description: Evaluation of Hydrothermal Liquefaction at the Great Lakes Water Authority Using a...

Evaluation of Hydrothermal Liquefaction at the Great Lakes Water Authority Using a Pilot-Scale System

Abstract

Hydrothermal liquefaction (HTL) is a promising technology that can recover nutrients, remove emerging contaminants, and convert sludge into biocrude oil, a precursor for biofuels.[sup]1-4[/sup] A recent study has shown that 576 WRRFs in the U.S. could deploy financially viable HTL.[sup]5[/sup] We have submitted an abstract about a feasibility study performed to evaluate HTL implementation at the Great Lakes Water Authority (GLWA). This abstract presents results from the operation of the Genifuel HTL demonstration unit deployed at the GLWA for three months (Figure 1). The unit processed 50 L/day of wet feedstock per run and completed six successful runs with different feedstock blends (table 1). HTL operated at 350 °C and 200 bar. Because GLWA sludge was hard to pump, dried biosolids pellets produced at GLWA's biosolids drying facility were diluted with deionized water to approximately 15% total solids and used as feedstock to ensure stable operation of the demonstration unit. GLWA operates a combined sewer system and is currently in the process of upgrading its grit removal facilities. Until the new grit removal is in service, the sludge used during the demonstration exhibited substantially higher ash content than anticipated and significantly lower lipid content compared to assumptions used in the feasibility study (Table 2). These differences resulted in lower biocrude yields than predicted. A complete mass balance was conducted for the sludge-only run, but biocrudes from all runs were characterized (Tables 3). Biocrudes derived from sludge were characterized by relatively low carbon content, high moisture, and elevated inorganic concentrations, particularly silica, which exceeded 1000 ppm in all cases. Biocrudes from the 3% FOG run was selected for upgrading. Water was removed using multiple cooling–heating cycles to separate aqueous and organic phases, followed by a 1% formic acid wash at 80 °C to remove filterable solids. The cleaned biocrude was hydrotreated using a continuous fixed-bed downflow reactors (Figure 2) under 1500 psig hydrogen with a two-step catalytic system (Table 4 and 5). During hydrotreatment of the 3% FOG biocrude, a pressure drop developed after approximately 40 hours, leading to reduced flow and complete reactor plugging after 92 hours (Figure 3). ICP analysis of the recovered plug showed very high silicon content (16,955 ppm). Distillation of upgraded products yielded approximately 60 wt% diesel-range product for the 3% FOG run. The diesel fraction for the 3% FOG run exhibited cetane numbers around 40, acceptable for refinery co-processing but below conventional diesel specifications, with elevated cloud and pour points suggesting the presence of long-chain or mildly polar components (Figure 4). HTL aqueous by-products (HTL-aq) were analyzed by HPLC and ICP-OES to quantify organic and inorganic constituents generated during HTL (Tables 6 and 7). The HTL-aq was dominated by low-molecular-weight oxygenates, primarily acetic acid (0.16–0.24 g/L), glycerol (0.07–0.19 g/L), ethanol, and acetone, with minimal phenolic and furanic compounds. Sodium and potassium were the dominant inorganic species, with moderate silicon and sulfur concentrations, while calcium, magnesium, and transition metals remained below 2 mg/L, indicating effective phase separation and minimal ash carryover. Overall, the HTL-aq remained organics-rich with moderate salinity, supporting evaluation for downstream treatment or resource recovery. Two treatment options for HTL-aq were evaluated, anaerobic digestion (AD) and supercritical water oxidation (SCWO). Two AD configurations were assessed: a continuously stirred tank reactor (CSTR) and an expanded granular sludge bed (EGSB) (Table 8 and Figure 5). The EGSB was inoculated with the seed sludge from an industrial grade EGSB system and the CSTR was inoculated with the effluent of a WRRF mesophilic digester. The EGSB achieved 60–80% chemical oxygen demand (COD) removal after a short acclimation period, with stable methanogenesis and no volatile fatty acid accumulation (Fig. 6). In contrast, the CSTR initially exhibited inhibition at higher HTL-aq loadings, likely due to nitrogen heterocyclic compounds,[sup]6[/sup] but achieved approximately 45% COD removal after dilution and operational adjustments (Fig. 7 and 8). Based on the low calorific content of the HTL-aq, samples were mixed with methanol before running SCWO. SCWO batch tests showed limited oxidation of methanol in HTL-aq mixtures, indicating suppression of oxidation reactions under the tested conditions (Fig. 9 and 10). Overall, this demonstration confirms that, if HTL is to be implemented at GLWA, it is necessary to improve grit removal to enable reliable biocrude upgrading. Co-processing with low ash wastes (e.g. FW) could also reduced ash-related challenges. HTL-aq products can be managed through AD with sufficient dilution or SCWO, supporting integration of HTL into water resource recovery facilities under evolving regulatory constraints.

This paper was presented at WEFTEC 2026 in New Orleans, Louisiana.

Presentation time

11:30:00

11:45:00

Session time

10:30:00

12:00:00

SessionInnovative Approaches to Resource Recovery and Carbon Reduction in Wastewater

Session locationErnest N. Morial Convention Center

TopicBiosolids and Residuals, Circular Water Economy, Energy Production, Conservation, and Management, Resilience, Safety, and Disaster Planning

Author(s)

Fonoll Almansa, Xavier, Wehner, William, Norton, John, Marcus, Andrew, Li, Shuyun, Jiang, Yuan, Santosa, Daniel, Oyler, James, Willis, John

Author(s)X. Fonoll Almansa1, W. Wehner1, J. Norton2, A. Marcus2, S. Li3, Y. Jiang3, D. Santosa3, J. Oyler4, J. Willis5

Author affiliation(s)University of Texas At Austin, 1University of Texas At Austin, 1Great Lakes Water Authority (GLWA), 2Great Lakes Water Authority (GLWA), 2Pacific Northwest National Laboratory, 3Pacific Northwest National Laboratory, 3Genifuel Corporation, 4Brown and Caldwell, 5

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2026

DOI10.2175/193864718825160553

Volume / Issue

Content sourceWEFTEC

Word count15

How Columbus Used Fugitive Methane Quantification to Implement Fugitive Methane Abatement Solutions as Part of a Major Bioenergy Program

Abstract

Methane is a major contributor to climate change, accounting for 45 percent of current net warming. As a potent greenhouse gas (GHG), it is 84 times more effective at trapping heat in the atmosphere compared to carbon dioxide over a 20-year timeframe. A global effort to reduce methane emissions was inaugurated by the Global Methane Pledge (GMP) with 150 countries committing to reduce methane emissions by at least 30 percent from 2020 levels by 2030. Its reduction is crucial to mitigate near-term warming and to avoid the worst effects of climate change. Municipal water resource recovery facilities (WRRFs) have been estimated to contribute around 5-8% of global anthropogenic methane emissions (Ocko, 2021) which are largely attributable to fugitive, or unintended, releases. These emissions are associated primarily with anaerobic digestion and associated solids handling. The significance of methane and its impacts on the climate, coupled with burgeoning interest and attention to WRRFs as a source, creates considerable opportunities within the wastewater sector to address both local and global climate action goals by reducing these emissions. Recently, new measurement technologies developed in other sectors (oil, gas, and landfill) have provided WRRFs with the ability to more accurately quantify and identify sources of emissions. In addition, new abatement technologies and knowledge to reduce fugitive methane has emerged that allows solutions to be implemented. This abstract covers one of the first efforts to reduce fugitive methane as part of a major bioenergy program based on new technology quantification and represents the second part of a two part presentation. As part of the Bioenergy Project at Southerly Wastewater Treatment Plant (SWWTP), the City of Columbus embarked on a field campaign to quantify fugitive methane emissions. The field campaign was the first US multi-technology effort to quantify fugitive methane at a WWTP using commercial services and products. This included drone flux measurement (DFM), an optical gas imaging (OGI) camera and discrete sampling with a flame ionization detector (FID). The field investigation spanned several days and included an evaluation of the solids handling facilities, waste gas burner (WGB), digestion facilities, and the BLAF. The OGI camera was used as a qualitative method for source identification. The DFM is an ISO 17025-accredited top-down method and was used as the primary method for quantification. The DFM was used to collect area emissions from various parts of the plant and a representative DFM. The total amount of fugitive methane measured via drone at SWWTP at the time of the investigation was approximately equal to 15 percent of the total biogas production or 70 kg/hr as seen in Figure 1. The outcomes of the campaign lead to an alternatives evaluation looking at a comprehensive list of abatement options. A fugitive methane model was developed to estimate fugitive methane emissions based on the quantification campaign results and future flows and loads for years 2028 and 2048 see Figure 2 and Figure 3. In the no-action scenario, the total FM would increase 87 percent. Due to the severity of the FM issue, the City decided to take initial actions to reduce fugitive methane emissions by developing a beneficial biogas program, implementing digestion system improvements, and replacing the methane phase digester floating covers with concrete fixed covers. These actions would result in a fugitive methane reduction of 74 percent based on 2048 flows and loads see Figure 4. The remaining FM needed to be mitigated were from the solids handling facilities and the BLAF (see Figure 1). Solutions that were evaluated included augmented biofiltration, vapor combustion units (VCUs), regenerative thermal oxidizers (RTOs), an Elovac system, and replacing the BLAF cover to capture the gas. A cost-benefit analysis based on cost per metric ton (MT) CO2e reduced was used to evaluate the alternatives. RTOs were selected for the BLAF and VCUs for the solids handling facilities as shown in the costs in Table 1 and 2. The end solution resulted in a 96 percent decrease in FM emissions from the solids handling and treatment processes at SWWTP see Table 3.

Methane is a major contributor to climate change and a major source of GHG emissions for WRRFs. As part of the Bioenergy Project, the City of Columbus embarked on a field campaign to quantify FM emissions. The campaign measured FM via drone at Southerly WWTP that was equal to 15 percent of the total biogas production or 70 kg/hr. An alternatives evaluation was conducted on FM abatement solutions and integrated into the bioenergy to reduce fugitive methane up to 95 percent.

SpeakerLe, Trung

Presentation time

14:30:00

14:50:00

Session time

13:30:00

15:00:00

SessionGreenhouse Gas Strategies in Action: Measure to Mitigate

Session number402

Session locationRoom 344

TopicBiosolids and Residuals, Energy Production, Conservation, and Management, Intermediate Level

Author(s)

Le, Trung, Schaad, Katie, Weidman, Emily, Andrews, Nancy, Willis, John, Bronstad, Embrey, Schweinfurth, Geoffrey

Author(s)T. Le1, K. Schaad2, E. Weidman3, N. Andrews4, J.L. Willis5, E. Bronstad6, G.T. Schweinfurth7, D. Fiorino3

Author affiliation(s)1Brown and Caldwell, VA, 2, OH, 3Brown and Caldwell, OH, 4, MN, 5Brown and Caldwell, GA, 6Brown and Caldwell, WA, 7City of Columbus Department of Public Utilities, OH

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159710

Volume / Issue

Content sourceWEFTEC

Word count20

How WSSC Water Gets the Biggest Return for Digester Gas Energy

Abstract

As part of WSSC Water's (Laurel, MD) BioEnergy Program digester gas will be upgraded to renewable natural gas (RNG). While many wastewater utilities consider RNG projection as non-core business and therefore outsource or 'public-private-partnership' the subcontracting, operation, and maintenance of these activities; WSSC is contracting, negotiating, and managing the entire RNG/RINs program in-house. This presentation will discuss three aspects of the RNG program scheduled for start-up in the first quarter of 2024: 1) Equipment start-up and pre-injection gas quality testing prior (allowed) injection to the WGL pipeline; 2) Actual trades, revenue, and cost for selling RNG to Montgomery County Transit and RINs to a yet-to-be-identified obligated party (refinery); and 3) An updated summary of program economics based on these first actual transactions (that WSSC administers in-house, so as to maximize the net return to their rate base). It is believed that the details of each of these will be of tremendous interest to other utilities considering digester gas upgrading to RNG for transportation fuel uses and RIN revenue. Additionally, the firsthand accounts of equipment commissioning, and mandated gas testing (and possibly test failures and associated responses/equipment tuning/adjustments) will be very informative. The sum total of which will hopefully encourage other utilities to administer these projects themselves and clear up the 'blurry opaqueness' offered by vendors, public-private-partnership (P3) contractors, and other third parties who stand to make all the profits themselves by delivering turn-key projects/programs and taking the unknowns out of wastewater utility's responsibility. The most recent program accounting (without financing) projects WSSC net revenues of between $1,200,000 and $4,800,000/year (at RIN prices of $1.00 to $3.50/D3-RIN). Which compares very favorably to a net operating cost of roughly $500,000/year had they instead used a conventional P3 to deliver the same project. If the costs of WSSC's bond financing are considered, WSSC revenues are reduced to between $300,000 and $3,800,000/year. But P3 costs would increase even more to $3,500,000/year (including P3 financing of the gas upgrading system and associated infrastructure and WGL's financing of the RNG 'gate station'). As a further point of clarification, none of these values include grant funding obtained by WSSC that would have made (and did make) all presented economics more attractive.

WSSC Water has managed and contracted for their RNG program themselves with limited consultant support instead of using a P3 for financing, designing, building, operating, subcontracting, and maintenance. Recent accounting projects WSSC net revenues of between $1.2 and $4.8 million/yr at D3-RIN prices of $1.00 to $3.50/RIN instead of paying a P3 $600,000/yr. This paper shows how/why P3 economics 'get bad' quickly, hopefully encouraging others to self-perform their own RNG/RINs programs.

SpeakerWillis, John

Presentation time

16:00:00

16:20:00

Session time

15:30:00

17:00:00

SessionWhat Will You Make of Your Biogas?

Session number430

Session locationRoom 346

TopicBiosolids and Residuals, Energy Production, Conservation, and Management, Intermediate Level, Sustainability and Climate Change, Utility Management and Leadership

Author(s)

Willis, John, Taylor, Robert

Author(s)J.L. Willis1, R.B. Taylor2

Author affiliation(s)1Brown and Caldwell, GA, 2WSSC Water, MD

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159713

Volume / Issue

Content sourceWEFTEC

Word count12

Description: Not Every Utility is Equal: How Operational Patterns, Influent Characteristics, and...

Not Every Utility is Equal: How Operational Patterns, Influent Characteristics, and Compliance Limits Shape Fugitive GHG Emission Variability in Wastewater Treatment Plants

Abstract

Introduction Amid the accelerating impacts of climate change, the urgent need to reduce greenhouse gas (GHG) emissions is more critical than ever, yielding commitments from developing countries aimed at achieving net-zero emissions by 2050. While energy sector decarbonization is underway, less attention has been given to direct GHG emissions from essential infrastructure. To this end, the wastewater sector alone contributes approximately 5% of global non-CO2‚ GHG emissions, largely in the form of methane (CH) and nitrous oxide (N2O), which have global warming potentials of 28 and 298 times higher than CO2, respectively [1]. As a prerequisite to mitigation, there has been growing academic and industrial interest in the quantification of the direct, or scope 1, emissions from wastewater treatment plants (WWTPs) -- emissions generated through bioprocesses [2]. The standard method for estimating emissions relies on the current Intergovernmental Panel on Climate Change (IPCC) guidelines, which use a simplified global emission factor (EF). However, this approach lacks the granularity required to capture the actual dynamics of GHG emissions from WWTPs [3]. Recent studies document substantial discrepancies, with observed CH emissions reaching up to 100 times the IPCC's estimated EF [4], and N2O emissions varying over six orders of magnitude [5]. These findings underscore the critical need for site-specific investigations to better understand emissions behavior, identify the factors driving variability, and pinpoint the specific sources contributing to these emissions. Therefore, in this research, we present findings from an ongoing Canadian project monitoring greenhouse gas (GHG) emissions from three full-scale wastewater treatment plants (WWTPs) across Canada. Our multi-level approach combines various advanced measurement techniques, including gas/liquid sensors, optical gas imaging, drone-based sensing, aircraft imaging, and satellite imaging. While previous studies have largely examined emissions variability in relation to treatment technology [5] and plant's size [4], this research attempts to link plant's GHG emissions with influent characteristics, compliance limits, and operational patterns. Treatment plant description and measurements campaign The Canadian wastewater treatment plant featured in this study operates with a typical treatment configuration. The plant comprises primary treatment, followed by the activated sludge (AS) process and, finally, disinfection. Given that there are no nitrogen compliance requirements, the AS process does not incorporate anaerobic and anoxic zones. Secondary sludge undergoes thickening, which is then combined with primary sludge for anaerobic digestion. The digested sludge is subsequently dewatered, and the centrate is returned to the AS process. To enhance settling efficiency, thickened waste activated sludge (TWAS) is mixed with primary sludge (PS) before digestion. To monitor nitrous oxide, two Unisense® sensors were used and located strategically to capture possible variation across the aeration tank. Methane (CH) emissions are quantified using 16 ground-based sensors, complemented by a 3-day intensive measurement campaign employing drone-based and optical gas imaging techniques. Results and discussion For over six months, liquid N2O concentrations were monitored at two locations in the aeration basin: the first and third quarters. As illustrated in Figure 1, median daily N2O emissions were recorded at 2.22 KgN-N2O/day and 2.91 KgN-N2O/day, with only occasional instances exceeding 10 KgN-N2O/day. This corresponds to an N2O emission factor (EF) of 0.005±0.0012 kg N2O-N per kg TN which is substantially lower than the IPCC EF of 0.016 kg N2O-N per kg. This can be referred to the limited nitrogen removal in the plant, Figure 1. This is because the plant does not have ammonia or total nitrogen compliance limit. While prior studies reported higher N2O emissions with incomplete nitrification [6], the present plant was operated at sludge age (3.34±0.65 day) close to the washout of nitrifying biomass which resulted in lower EF. Results of the methane emissions quantification are shown in Figure 2. The average methane emissions from the plant equal to 1293±807 kgCH4/day. This is equivalent to 3.5-4% of gCH4/m3 treated and 2.9-3.1% of the influent COD load. These values are relatively high but are within the typical range reported in literature [4]. Yet, emissions distribution within the plant is interesting. As seen in Figure 2, the highest contributors to methane emissions are the aeration tanks and primary clarifiers which combined contributed to almost 60% of total plant's methane emissions, whereas Digesters and gas burners contributed only 25% of such emissions. The low emissions from the digesters were confirmed by the handheld OGI camera which indicated no detected leakage either from covers or structural cracks. The high emissions from aeration tanks can be referred to several potential reasons. One possible reason can be unideal aeration and mixing, given that coarse bubble aeration is used to do both. This is supported by the low DO levels observed at the first quarter of the tank (below 0.5 mg/L). Another potential source is the centrate return after digesters which can contain high dissolved methane concentrations. Similar observation were reported in prior studies [7]. The high emissions from the primary clarifiers can be potentially explained by (i) high methane concentrations in the received influent, (ii) high TSS concentrations in the influent, (iii) the return of the TWAS and associated high sludge blankets in the primary sludge. The resulting total daily GHG emissions of the plant are estimated to be equivalent to 43.57 metric tonne of CO2. Interestingly, as shown in Figure 3, methane constituted more than 80% of the plant's emission. This is opposing the typical results in the literature where N2O contributes to more than 50% of plant's GHG emissions [3,8]. This is due to (i) compliance limits that do not mandate ammonia removal, (ii) operational decisions such as centrate return, operating at short sludge age washing out nitrifiers, TWAS return, and (iii) received influent that contained high dissolved methane concentrations and high TSS concentrations. Conclusion In conclusion, this study highlights how influent characteristics, operational patterns, and compliance limits can influence GHG emissions from wastewater treatment plant processes. Methane accounted for over 80% of the total emissions, contrasting with typical findings where Nâ‚‚O dominates. These findings emphasize the need for site-specific GHG monitoring and targeted mitigation strategies in wastewater treatment.

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

SpeakerAlsayed, Ahmed

Presentation time

10:45:00

11:05:00

Session time

10:45:00

11:45:00

SessionAcademic Advancements in Digestion and Fugitive Greenhouse Gas Emissions

Session number2

Session locationBaltimore Convention Center, Baltimore, Maryland, USA

TopicAnaerobic co-digestion, Biomethane, Lipids/proteins/carbohydrates ratio, TWAS, Manure, SSO, Anaerobic Digestion, Biogas, Biogas Production, Energy recovery, food waste, Greenhouse Gases, Membrane bioreactor, Nitrous oxide, Resource Recovery, Sustainability And Social Responsibility

Author(s)

Alsayed, Ahmed, Elsayed, Ahmed, Khalil, Mostafa, Zaghloul, Mohamed, Kakar, Farokh, Bell, Katherine, Willis, John, Elbeshbishy, Elsayed

Author(s)A. Alsayed1, A. Elsayed2, M. Khalil2, M. Zaghloul3, F. Kakar5, K. Bell5, J. Willis5, E. Elbeshbishy2

Author affiliation(s)Northwestern University, 1Toronto Metropolitan University, 2United Arab Emirates University, 3Brown and Caldwell, 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2025

DOI10.2175/193864718825159802

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count23

School House Rock: How a Bill becomes a Law and then Fully Defined

Abstract

I’m just a bill, sitting here on Capitol Hill… While almost everyone 45 years old or older knows the refrain, we rarely consider the linkage between environmental regulations that shape wastewater-treatment operations/projects and the legislated authority that Congress must create to frame that structure. Instead, questions like: “Doesn’t the United States (US) Environmental Protection Agency (EPA) understand that making all co-digestion biogas renewable identification numbers (RINs) only Advanced (or “D5”) instead of Cellulosic (or “D3”; that are worth 2 to 2.5 times the value of D5s) discourages water resource recovery facilities (WRRFs) from recovering more resources?”; or “Why doesn’t the Renewable Fuel Standard (RFS) fairly provide for electric RINs (e-RINS)?” are heard all too often. This paper is less about how Congress creates laws – and more about what happens afterwards to make federal policy and programs that deliver benefits to the public at-large and the environment.

Dive deep into the details of the Renewable Fuel Standards regulatory details that allow wastewater utilities to generate serious $$$$ from digester-gas upgrading and use of rCNG to fuel vehicles. Congress’ original Legislation is linked to EPA’s RFS1, RFS2, and Pathways-II Regulations and the process/effort/timeline for EPA’s creation of rules is reviewed in detail. Other more routine related actions are also discussed.

SpeakerWillis, John

Presentation time

13:30:00

13:45:00

Session time

13:30:00

14:30:00

SessionBiogas: Market-based Decisions for Resource Recovery

Session number507

TopicBiosolids and Residuals, Energy Production, Conservation, and Management, Policy and Regulation

Author(s)

John Willis

Author(s)J. Willis1;R. Bastian2;

Author affiliation(s)Brown and Caldwell, Atlanta, GA1Former US Environmental Protection Agency (EPA) –Office of Water, DC2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825158168

Volume / Issue

Content sourceWEFTEC

Word count14

Description: School House Rock: How a Bill becomes a Law and then Fully Defined (using the...

School House Rock: How a Bill becomes a Law and then Fully Defined (using the Renewable Fuel Standard as an Example)

Abstract

KEY TAKEAWAY EPA works within the framework of Congressional legislation and prior rules of their own and other federal departments' making. The process is transparent; influenced by science, economics, and public comment; evolutionary; and available for anyone willing to read extensively. INTRODUCTION I'm just a bill, sitting here on Capitol Hill. While almost everyone 45 years old or older knows the refrain, we rarely consider the linkage between environmental regulations that shape wastewater-treatment operations/projects and the legislated authority that Congress must create to frame that structure. Instead, we ask or hear questions like: 'Doesn't the United States (US) Environmental Protection Agency (EPA) understand that making all co-digestion biogas renewable identification numbers (RINs) only Advanced (or 'D5') instead of Cellulosic (or 'D3'; worth 2 to 3 times the value of D5s) discourages water resource recovery facilities (WRRFs) from recovering more resources?'; or 'Why doesn't the Renewable Fuel Standard (RFS) provide for electric RINs (e-RINS)?' This paper is less about how congress creates laws & and more about what happens afterwards to make federal policy and programs that deliver benefits to the public at-large and the environment. The Energy Policy Act of 2005 and its successor law, the Energy Independence and Security Act (2007) established the RFS. EPA promulgated rules that we will rely on as a relevant 'case study'. RFS evolution and context provides insight into the following aspects of Federal policymaking and program implementation: - Inter-relationships between Executive, Legislative, and Judicial branches. - How Presidential Administrations can (and in some ways cannot) influence regulation. - The public provides input to the process. - Bureaucracy is a good thing that while slow-moving; limited by legislated authority; constrained by prior regulations; methodically moves toward 'getting it right' on a foundation of science, economics, and available hard data. Readers are encouraged to read this paper with an open mind and rigorously explore all claims (e.g. consult the citations) that conflict with preconceived notions or otherwise. Please contact us to discuss findings that support or (more importantly) conflict with our positions & so that we might improve our collective understanding of these subjects. Congressional legislation creates the framework for new programs like the RFS and provides many of the details, specific requirements, and guardrails for each program. EPA then conducts rulemaking within the legislated framework to define program implementation and compliance. An example of how the proposed full paper would inform the reader is included in this abstract. That example covers the regulatory basis for EPA's distinction that cellulosic RINs, both D3 and D7, must be derived from feedstocks comprised of at least 75% cellulosic content (in addition to providing the largest/over-60% life-cycle greenhouse gas (GHG) reductions. CELLULOSIC RINS MUST HAVE OVER-75%-CELLULOSIC FEEDSTOCK The cellulosic discussion originates in the 2005 legislation. The 2005 Act envisions an industry where non-food (i.e. 'waste') agricultural materials are converted into cellulosic ethanol and provided incentives to foster said-industry's innovation and development. The 2007 Congressional legislation provides the following definition : ''Cellulosic biofuel' means renewable fuel derived from any cellulose, hemicellulose, or lignin that is derived from renewable biomass and that has lifecycle greenhouse gas emissions, as determined by the Administrator, that are at least 60 percent less than the baseline lifecycle greenhouse gas emissions.' The 2007 Act also made provisions for EPA to adjust cellulosic volume requirements downward to match actual production when production fell below legislated minimums and identified cellulosic waiver credits as a volume-shortfall bridging mechanism . In Spring 2007, EPA published Regulation of Fuels and Fuel Additives: Renewable Fuel Standard Program (or RFS-1). RFS-1 required 116 pages of 3-column CFR text with details on a wide array or air-quality benefits associated with the RFS. The potentially most enlightening cellulosic discussion within RFS-1 relates to equivalence determinations for various fuels. Specifically, that cellulosic-biomass ethanol has 2.5 times the per-gallon value of corn ethanol (with an equivalence of 1.0) which mirrors the higher historical values attributed to cellulosic RINs. The balance of RFS-1 provides many foundational details of the RFS, but little on cellulosic biofuels (with continued cellulosic ethanol focus). In 2010, EPA published Modifications to RFS-1 (or 'RFS-2') which provided the first minimum volume by-type and by-year table with cellulosic RINs as one of 4 nested categories. EPA published the 'Pathways II' rule in mid-2014. This rule determined that 'EPA has decided to finalize a cellulosic content approach, with a minimum cellulosic content threshold of 75%' in order to qualify for cellulosic RINs . That determination is supported by an extensive discussion on options considered and the rationale for its selection. The discussion further states that the 75% threshold has been consistently applied to other Pathways II updates; which includes updating Table 1 to include Pathway Q, which allowed renewable compressed or liquefied natural gas from municipal wastewater treatment digester biogas to be classified as D3 RINs . EPA has recently suggested that no regulatory pathway currently exists to allow for feedstocks with less than 75% cellulosic content like FOG (primarily lipids and not cellulosic) or food waste (with typically less than 75% cellulosic content) to be co-digested with municipal sludge within a single digester, diluting the combined feedstock cellulosic content to below 75% - and still qualify for D3 RINs (without special provisions). While that discussion should proceed, it is important for the domestic wastewater industry to understand that without new data and/or approaches, and possibly new EPA rules for co-digestion & that EPA's 'hands are tied' by the rules currently in place. SUMMARY This paper informs both procedurally (on how the RFS is administered and legislated) and technically with details for anyone involved with RFS projects. Fully referenced discussions will be provided on the following aspects of the RFS and its ongoing legislative process: - EPA amended the methodology to estimate RIN volumes for the 2018 calendar year. The revision was published, explained, and has been in use since. - While EPA administers the RFS, that administration is done in close cooperation with the US Departments of Energy and Agriculture. Examples of such coordination will be provided. - The Renewables Enhancement and Growth Support Rule was issued as a proposed rule in late 2016 to address shortcomings in the RFP program (including provisions for intermediate biofuel products; a framework for eRIN development; and other topics. This proposed rule and its eventual withdrawal will show how changing Presidential Administrations can influence the regulatory process. - Two or three examples will be provided on how filed public comments on proposed rules changed EPA's understanding and affected the final published rules. - Finally, as an example of how the Judicial branch of the government affects the administration of laws, a discussion will be included on the Tenth Circuit Court of Appeals determination that EPA had exceeded its authority in granting small refinery exemptions (Renewable Fuels Association et al. v. EPA case, January 24, 2020) and EPA's response to that determination.

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

SpeakerWillis, John

Presentation time

15:45:00

16:15:00

Session time

13:30:00

16:45:00

Session number13

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicBiogas To Biomethane, Circular Economy, Regulatory Requirements

Author(s)

J. Willis

Author(s)J. Willis1; R. Bastian2

Author affiliation(s)Brown and Caldwell; 1US Environmental Protection Agency HQ; 2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158443

Volume / Issue

Content sourceResiduals and Biosolids

Word count22

Description: Sector-wide GHG Emissions with Normalized Process and Effluent N2O, Sewer CH4, and...

Sector-wide GHG Emissions with Normalized Process and Effluent N2O, Sewer CH4, and Methanol CO2

Abstract

Sewer methane (CH4) and methanol carbon dioxide (CO2) have been poorly covered in greenhouse-gas (GHG) emissions protocols. Domestic-sewage treatment nitrous oxide (N2O) has been treated either holistically on a population-based basis or more recently split out to differentiate N2O emitted from biological processing of nitrogen and by effluent-nitrogen discharge and subsequent production of N2O from biological processes in the receiving environment. Willis et. al (2017) and Willis et. al (2020) used DC Water GHG inventories before and after digestion upgrades at the Blue Plains Advanced Wastewater Treatment Plant (Blue Plains) to estimate that methanol (CH3OH) CO2 and sewer- CH4 respectively represented 55.5% and 12.8% of the US centralized-sewage treatment industry’s Scope GHG emissions. These publications noted that, due to the use of Blue Plains’ extremely low process N2O emission rates, that process N2O was necessarily under-accounted for in those national estimates. This paper coordinates those prior estimates with process-specific N2O emissions to provide an initial, better-reconciled assessment of the US wastewater industry’s Scope-1 GHG emissions.

SpeakerWillis, John

Presentation time

14:10:00

14:30:00

Session time

13:30:00

14:30:00

SessionOdors in the Greenhouse: Emission Investigation and Modeling for Odors and Greenhouse Gasses

Session number410

Author(s)

J. WillisK. ChandranT. Le

Author(s)J. Willis1; K. Chandran2; T. Le3;

Author affiliation(s)Brown and Caldwell, GA1; Columbia University, VA2; Brown and Caldwell, WA3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157405

Volume / Issue

Content sourceWEFTEC

Word count15

Description: Turning Emissions into Assets: WSSC Water's DOE-Funded Biogas-to-Methanol...

Turning Emissions into Assets: WSSC Water's DOE-Funded Biogas-to-Methanol Innovation

Abstract

The U.S. wastewater sector faces increasing pressure to achieve sustainable resource recovery while contending with operational constraints such as high methanol consumption and greenhouse gas (GHG) emissions. WSSC Water's Piscataway Bioenergy facility processes solids from six WRRFs, treating as much as 95 MGD of wastewater per day, through thermal hydrolysis (THP), anaerobic digestion (AD), and biogas upgrading to renewable natural gas (RNG). Through a Department of Energy (DOE)-funded partnership among WSSC Water, Johns Hopkins University, the University of Maryland, Argonne National Laboratory (ANL), Brown and Caldwell, and the DOE, this project develops an approach to enhance biogas production and convert carbon dioxide (CO[sub]2[/sub]) into value-added methanol (MeOH) while recovering additional RNG. This work demonstrates a transformative pathway for WRRFs to improve energy efficiency, reduce costs, and lower GHG emissions (Table 1). Objectives of the DOE project include: 1. [b]Boost AD performance[/b] – Increase methane yield by applying free nitrous acid (FNA) pretreatment and THP. 2.[b] Recover entrained gases[/b] – Capture methane, CO[sub]2[/sub], and nutrients during sludge dewatering, enabling struvite co production. 3. [b]Electrolyze CO[sub]2[/sub] to MeOH[/b] – Convert recovered CO[sub]2[/sub] into MeOH using an electrolyzer powered by solar, reducing overall carbon intensity compared with conventional routes. [b]Methods[/b] The first phase of work focused on developing the technologies at bench-scale at the university labs and designing the Biogas Harvester (BH). The second phase would scale-up and pilot at the Piscataway Bioenergy facility. The project includes characterization of the solids feeding WSSC Water's Bioenergy facility through Biochemical Methane Potential (BMP) assays, treating identical volumes of solids with and without free nitrous acid (FNA) as well as with thermal hydrolysis. We designed a modular biogas harvester next to the full-scale anaerobic digester upstream of belt filter press dewatering. This BH system intercepts methane and CO[sub]2[/sub] before they are released in the dewatering process and precipitates struvite before coating downstream equipment. The gas captured by the harvester is then directed through carbon molecular sieve (CMS) membranes, which allow CO[sub]2[/sub] to permeate through highly selective pores while rejecting methane and other gases. Purified CO[sub]2[/sub] is introduced into a humidified electrolyzer, which houses a cobalt based catalyst. The cell reduces CO[sub]2[/sub] to methanol, which can be used on-site or sold. Finally, we integrated all the data into ANL's GREET life cycle assessment model to quantify GHG savings, energy balances, and cost per gallon of MeOH.

[b]Results[/b]
• [b]FNA pretreatment[/b] increased biogas yield by >15%. Based on the observed increase in soluble COD after FNA pretreatment and the absence of volatile solids (VS) destruction during pretreatment, it is estimated that the biogas production potential of solids under FNA pretreatment (pH 5.5, FNA =2.1 mg N/L, Temperature=35°C) is in the range of 180-251 mL CH[sub]4[/sub]/g VS vs. 142 mL/g.
• Completed the 100% [b]BH design[/b] for nearly full-scale application (3-foot diameter, 25-foot-tall primary BH column; Figure 1). The BH eliminates fugitive methane that would otherwise escape during dewatering.
• Developed CMS [b]membranes[/b] with CO[sub]2[/sub]/CH[sub]4[/sub] selectivity of 1164, sufficient for efficient electrochemical conversion. This approach has the potential to significantly reduce costs while improving gas purity for RNG upgrading and MeOH synthesis.
• Developed and scaled-up a recirculating liquid flow-cell reactor using a CoPc-based catalyst for [b]CO[sub]2[/sub]-to-MeOH conversion[/b] through a sequential CO[sub]2[/sub]→CO→CH[sub]3[/sub]OH pathway (Figure 2). The reaction exhibited two distinct stages, suggesting that CO acted as an intermediate and was subsequently hydrogenated to methanol (Figure 3).
• [b]Life cycle assessment (LCA)[/b] of the integrated system indicates that MeOH production has a carbon intensity of 0.28 kg CO[sub]2[/sub] eq kg⁻¹ MeOH-an 85% reduction relative to conventional MeOH pathways (Figure 4). Avoided emissions from methane capture, fertilizer displacement, and methanol displacement credits further offset the GHG emissions, resulting in an overall net benefit.
• The preliminary [b]techno economic analysis[/b] shows MeOH costs comparable to market prices (≈$0.80/gal) when powered by the on site solar array.

[b]Conclusions and Impact[/b] The innovative system demonstrates a dual benefit: it improves RNG yield and simultaneously produces MeOH with an 85% lower carbon footprint and lower operating cost. By capturing dissolved CH[sub]4[/sub] and CO[sub]2[/sub] that would otherwise be released, the plant avoids fugitive methane emissions and reduces fossil-derived MeOH consumption for nitrogen removal. The resulting methanol stream, once scaled up, could supply about 1.5X the demand of all WSSC WRRFs, transforming a growing chemical expense of over $2M per year into a renewable revenue source while simultaneously lowering emissions.

This paper was presented at WEFTEC 2026 in New Orleans, Louisiana.

Presentation time

15:30:00

15:45:00

Session time

15:30:00

17:00:00

SessionResource Recovery: Methane Was Just the Beginning

Session locationErnest N. Morial Convention Center

TopicBiosolids and Residuals, Circular Water Economy, Research and Innovation

Author(s)

Nguyen, Caroline, Li, Guangbin, Willis, John