Shen, Emma

Dr. Shen is a process engineer based in Jacobs Toronto Office, with more than 15 years of experience in municipal wastewater treatment design, process...

Titles from this speaker

Description: Balancing Carbon for Energy Recovery and Nutrient Removal for the World's Largest...

Balancing Carbon for Energy Recovery and Nutrient Removal for the World's Largest MBR Facility

Abstract

The 800 ML/d Tuas Water Reclamation Plant (WRP) will be the largest membrane bioreactor facility in the world, featuring many advanced treatment technologies and an integrated NEWater facility that produces high-grade water for reuse. The Tuas WRP will be co-located with an Integrated Waste Management Facility (IWMF) which will generate electricity to meet the demand for the co-located facility, making it energy self-sufficient. A key component to energy efficiency is the management of carbon through the treatment process, as it has major impacts on the energy production (through conversion to biogas in the anaerobic digestion process), energy consumption (especially from oxygen demand in the MBR process), and the dependency of carbon to drive biological nutrient removal. Extensive process modelling was completed to inform the design, specifically, incorporating flexibilities to allow for optimizing the degree of carbon re-direction via A-stage primary treatment while achieving effluent goals for NEWater and outfall discharge

SpeakerShen, Emma

Presentation time

13:00:00

13:30:00

Session time

11:00:00

12:00:00

SessionGoing KETO: Stories of Carbon Re-Direction in the Age of Advanced Nutrient Removal

Session number9B

TopicEnergy Production, Conservation, and Management, Municipal Wastewater Treatment Design, Nutrients, Research and Innovation

Author(s)

E. ShenT. ConstantineC. NewberyY. Wei HinM. WongL. Yee WenA. Ang

Author(s)E. Shen1; T. Constantine1; C. Newbery1; Y. Wei Hin2; M. Wong2; L. Yee Wen2; A. Ang2;

Author affiliation(s)Jacobs1; Singapore's National Water Agency2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157906

Volume / Issue

Content sourceWEFTEC

Word count15

Be Ambitious: Durham Region's Water and Wastewater Net-zero GHG Roadmap

Abstract

Durham Region initiated a project to develop a long-term greenhouse gas (GHG) management strategy for its water and wastewater (W&WW) facilities over the next 20 years, in alignment with the Region's Corporate Climate Action Plan (CCAP) goals of 20% below 2019 levels by 2025, 40% below 2019 levels by 2030, and achieving net-zero emission for corporate operations by 2045. The Region's GHG inventory was expanded to include applicable Scope 1 and 2 emissions conform with the 2019 Intergovernmental Panel on Climate Change (IPCC) Refinement, and selected Scope 3 emissions related to chemicals, biosolids, and incineration ash management (Table 1). Development of the GHG inventory considered the industry best practice, applicable local and federal GHG reporting requirements, the availability and accuracy of quantification methodologies for each source, the level of complexity and difficulty in quantifying these emissions, and whether mitigation measures are available (such that the contribution to GHG reduction goals can be reasonably quantified). The updated 2019 base year emission for Region's W&WW sectors was 45,913 tonnes CO2e, including 85% Scope 1, 6% Scope 2, and 9% Scope 3 emissions. Wastewater contributed to approximately 92% of the total emissions, while water accounted for the remaining 8%. It is recognized that setting GHG reduction targets for all emission sources is currently not practical, given the difficulty and uncertainty associated with the quantification methods. Therefore, only Scope 1 and 2 emissions were included for GHG objective setting; Scope 3 emissions will continue to be tracked to assist decision-making, and target setting can be considered in the future as improved methodologies can data sources become available. Figure 1 shows the base year Scope 1 and 2 emissions by source. Wastewater process N2O emission represents the single largest GHG source. The very low Scope 2 emissions (electricity) are attributed to the low-intensity electricity grid in Ontario (largely consisting of nuclear, hydro, and renewables). An industry scan of current best practices was completed to identify net-zero solutions applicable to the Region. The long list was screened using a set of must-meet criteria that considered compatibility, technology readiness level, and GHG reduction potential based on the 80/20 rule (i.e., 80% of emissions likely resulted from 20% of the processes). Twelve (12) sites/systems were shortlisted for detailed evaluation, including 6 wastewater pollution control plants, 4 water supply plants, the wastewater collection system, and the drinking water distribution system. These sites/systems together accounted for more than 90 percent of the total Scope 1 and 2 emissions. Monitoring and mitigating process N2O emissions was identified as one of the most critical strategies. A two-year continuous N2O monitoring program was initiated, with two liquid-phase N2O sensors installed at the Duffin Creek Water Pollution Control Plant (co-owned by Durham and York Regions) in August 2023; initial results indicated variances over time and at different locations within the same treatment train. Examples of other shortlisted net-zero solutions include mitigating CH4 emissions through leak detection and repair, converting sludge storage lagoon to gravity thickener to reduce fugitive CH4 emission, biogas upgrade to renewable natural gas, thermal hydrolysis pre-treatment coupled with post-aerobic digestion to increase biogas generation while mitigating process emissions, sewer thermal recovery, and solar photovoltaic generation. Future GHG projections were developed for business-as-usual and based on implementing the recommended projects, as shown in Figure 2. Although it is possible to meet the 2025 and 2030 GHG reduction targets set out in the CCAP (if implementing all the identified projects), additional reductions will be required to meet the net-zero target by 2045, through further process optimization and/or adopting innovative net-zero solutions in the long term as they become more developed. A two-tiered approach was recommended, including the baseline objectives considering the current best practices available, and stretch goals aligned with the CCAP targets, as illustrated in Figure 2. The project is expected to be completed in early 2024. The presentation will include the final recommendations of major projects, the implementation plan by 2045, and the refined short-, medium-, and long-term GHG reduction targets for Durham Region's water and wastewater systems. Results from the first 14 months of the continuous N2O monitoring program will also be presented.

Durham Region (ON) initiated a project to develop a long-term greenhouse gas (GHG) management strategy for its water and wastewater facilities that aligns with the Region's net-zero by 2045 commitment. This paper presents the holistic approach and final recommendations for the net-zero roadmap, including the short-, medium- and long-term GHG reduction objectives, and the implementation plan for major projects, including results from the first year of full-scale nitrous oxide monitoring study.

SpeakerShen, Emma

Presentation time

13:30:00

13:50:00

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)

Shen, Emma, Green, Joe, Beaulne, Denis, Pellegrino, Maika, Murphy, Ella

Author(s)E. Shen1, J. Green2, D. Beaulne2, M. Pellegrino3, E. Murphy4

Author affiliation(s)1Jacobs, ON, 2Regional Municipality of Durham, ON, 2, 3, ON, 4Jacobs, Ontario

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159509

Volume / Issue

Content sourceWEFTEC

Word count11

Description: Development of an Integrated Resource Recovery Strategy for the 630 ML/d Duffin...

Development of an Integrated Resource Recovery Strategy for the 630 ML/d Duffin Creek Water Pollution Control Plant

Abstract

The Duffin Creek Water Pollution Control Plant (WPCP) is a conventional activated sludge secondary treatment facility located in Pickering, Ontario that treats municipal wastewater from the Regional Municipality of Durham and York (the Regions). The plant has an average day design capacity of 630 megaliters per day (ML/d). The liquid treatment process consists of headworks, primary and secondary treatment, phosphorus removal via dual-point chemical addition, and chlorine disinfection. Waste activated sludge (WAS) is co-thickened with raw sludge in the primary clarifiers. Solids handling processes include anaerobic digestion (for a portion of the sludge generated), dewatering, and incineration. The plant also receives hauled septage, liquid raw sludge and digested biosolids from wastewater treatment plants in both Regions. Several internal energy sources generated at the plant are being used to offset energy consumption. Heat from the incineration process is recovered to generate steam, which is used to drive turbines to power the fluidizing air blowers, with excess steam to supplement plant heating. Biogas generated from the digestion process is captured to fuel hot water boilers and supplement digester and building heating. Capital upgrades to the incinerators are underway, which will allow heat recovered from incineration to meet plant-wide process and building heating demand, freeing up biogas for alternative utilization. In addition, ongoing upgrades to the digesters will divert imported sludge (largely digested) away from the primary digesters, therefore improving digestion performance and increasing biogas generation. The current solids treatment and energy recovery operations are illustrated in Figure 1. In alignment with Regional goals to advance sustainability and reduce greenhouse gas (GHG) emissions, the Regions initiated an Integrated Resource Recovery (IRR) Study at the Duffin Creek WPCP in 2019. The purpose of this study is to identify feasible opportunities that can be integrated into the plant, including energy efficiency/recovery, material use reduction/recovery, and water conservation/recycling opportunities. This paper presents the review and development of energy use reduction and recovery opportunities associated with solids treatment at the Duffin Creek WPCP.

Emma Shen is a process engineer based in Jacobs’ Toronto office, with 10 years of experience in municipal wastewater and water treatment plant performance assessment and process upgrades evaluation, process modelling, energy optimization, and chemical system and disinfection optimization. She is Jacobs’ Global Technology Lead for Wastewater Energy Optimization and Sector Decarbonization. Emma holds a PhD degree in Civli Engineering from University of Toronto, Ontario, Canada, and a bachelor degree in Environmental Engineering from Tsinghua University, Beijing, China. She was the 1st place recipient for the 2014 American Water Works Association Academic Achievement Award for her doctoral dissertation. In her spare time, Emma loves travel, reading, podcast, Lego, and puzzles.

SpeakerShen, Emma

Presentation time

14:00:00

14:15:00

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)

Emma Shen

Author(s)E. Shen1; P. Burrowes1; A.D. Willoughby1; T.A. Constantine1; D. Ross1;

Author affiliation(s)Jacobs, Toronto, ON, CA1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2021

DOI10.2175/193864718825158137

Volume / Issue

Content sourceWEFTEC

Word count18

Description: Global Lessons for Benchmarking and Reducing Fugitive Methane Emissions from Sludge...

Global Lessons for Benchmarking and Reducing Fugitive Methane Emissions from Sludge Treatment and Biogas Handling

Abstract

Introduction Sludge generated from wastewater treatment typically goes through a series of handling processes such as thickening, stabilization and dewatering, before its final use or disposal. Anaerobic digestion is widely applied in medium to large water resource recovery facilities (WRRFs) for sludge stabilization. In anaerobic sludge treatment, fugitive methane emissions can occur from digesters (due to aging infrastructure), downstream storage, from associated pressure relief valves and pipework, and also due to methane slip through combined heat and power (CHP) engines and biogas upgrading. For example, work in Denmark over the past few years has quantified methane emissions at 69 biogas facilities and shows methane emissions account for up to 7.5 percent of the gas production at WRRFs (Fredenslund, A.M et al., 2021; Scheutz & Fredebslund, 2019). Large leakage of methane may negate the positive climate impact from biogas energy recovery and contribute significantly to the facility's operational carbon footprint. A portion of the methane generated is dissolved in the digestate, which can also be released during the downstream dewatering or sidestream treatment processes. In addition, long-term sludge drying (e.g., in lagoons) is commonly applied in many countries, such as Australia, due to its ease of operation and low operational costs. Methane generated from sludge drying lagoons is typically not captured and can be a significant greenhouse gas (GHG) emission source. In the US, a country-wide standard methodology for quantifying GHG emissions from the wastewater sector does not exist. Among the available reporting protocols, methodologies for quantifying fugitive methane emissions from sludge treatment and biogas handling are limited to combustion of biomass and biogas, which essentially assumes zero methane emissions from anaerobic digestion and biosolids dewatering processes. The latest Biosolids Emissions Assessment Model (BEAM 2022) has recommended a minimum of 1 percent of methane in biogas as fugitive emission and allows a user-input value if site-specific data are available. The lack of consistent methodology and lack of facility level measurement result in significant risk to facilities in the estimation of their fugitive methane emissions through the sludge treatment and biogas handling processes. This paper presents an overview of challenges and issues in quantifying fugitive methane emissions from sludge treatment and biogas handling, impacts on GHG inventory and practical tips for reducing methane emissions based on global experience to date across a growing number of case studies. Benchmarking Fugitive Methane Emissions Methodologies and Key Considerations In the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, a three-tier method is described for quantification of methane emissions from WRRFs. Tier 1 provides global activity and emission factors; Tier 2 provides for local in-country activity factors and/or emission factors and Tier 3 methods require facility level monitoring. Accurately quantifying fugitive methane emissions requires Tier 3 facility level measurement using methods such as differential absorption lidar (DIAL), tracer gas dispersion (TDM) and inverse dispersion modelling (IDM), which may be combined with point source leak detection or other process unit methods to determine location of leaks. This practice remains emerging with significant work ongoing in Europe to provide facility level quantification and mitigation at WRRFs. Elsewhere, Tier 2 methods are common. The UK Carbon Accounting Workbook is used by Utilities to report on operational emissions and includes country-specific (Tier 2) theoretical emission factors associated with the most common sludge and biosolids processes in the UK, with emissions based on mass of methane per unit of tonnes dry solids of raw sewage sludge (UKWIR, 2020). In the Australian National Greenhouse and Energy Reporting (NGER) framework, methane process emissions are indirectly estimated using sampled influent and/or effluent streams and application of assumed biogas generation and percentage biogas utilization to calculate the net tonnes of CO2 equivalent released to the atmosphere. This approach considers facility level data but does not require direct measurement of the GHG, hence still considered Tier 2. Emissions from biogas flaring is based on best practice flow rate measurements of the flared biogas and its methane concentration. Different facilities may have a range of approaches to sampling process streams for operational, planning or reporting requirements. Sampling locations, frequencies and methodologies can result in inaccuracies in estimating the fugitive methane emissions. The recently published IWA book 'Quantification and Modelling of Fugitive Greenhouse Gas Emissions from Urban Water Systems' includes additional information on fugitive methane emissions from a range of wastewater treatment, sludge and biogas handling processes, estimated through facility level monitoring (IWA, 2022). Table 1 provides a summary of key methane emissions from global case studies including both those which directly monitor methane emissions and those which use various alternative GHG accounting methodologies, generally aligned with Tier 2 level approaches. A more complete table will be provided in the full paper. In the absence of global full scale monitoring data to estimate fugitive methane emissions, existing methodology estimates may be beneficial for benchmarking emissions from sludge treatment and biogas handling processes however, Tier 3 level facility monitoring is required to accurately estimate methane emissions and to validate any mitigation efforts. Monitoring and Reducing Fugitive Methane Emissions Whilst published literature studies of methane mitigation are limited, practical examples of programs for monitoring and mitigation across European countries show the criticality of direct methane emissions monitoring, and operational approaches to mitigate methane emissions through regular survey, proactive leak detection and repair and independent certification. Table 2 summarizes some of the key sources and (limited) mitigation approaches from work to date; further details to be provided in the full paper. In future planning, it is critical that decisions regarding anaerobic versus aerobic sludge digestion consider fugitive emissions from existing and proposed assets. Conclusions Fugitive methane emissions from sludge treatment and biogas handling processes are a significant source of GHG emissions which must be monitored and mitigated by utilities taking action to reduce their carbon footprint. These emissions are particularly critical for WRRFs with anaerobic digestion and open anaerobic systems such as sludge drying ponds. There is lack of consistent methodology for quantifying and monitoring these emissions in North America, which could lead to over- or (more likely) underestimation of their contributions to the overall GHG footprint for the WRRFs. As shown by ongoing work in Europe, facility level measurement is critical in quantifying the fugitive methane emissions. This paper will provide practical recommendations to WRRF operators to guide best practices for methane monitoring and mitigation throughout the facility life cycle.

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

SpeakerShen, Emma

Session time

11:45:00

SessionSession 11: Circular Water Economy

Session number11

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicSustainability and Resource Recovery

Author(s)

E. Shen

Author(s)E. Shen1, A. Romero2, A. Vellacott3, A. Lake4,

Author affiliation(s)Jacobs1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158791

Volume / Issue

Content sourceResiduals and Biosolids

Word count16

Subject keywordsCWECircular Water Economy

Green Energy, Less Power, Fewer Chemicals, Cleaner Water, Class A Biosolids: A Transformational Program at Chattanooga's MBEC With a Financial Payback

Abstract

Introduction The Moccasin Bend Environmental Campus (MBEC) in Chattanooga treats wastewater from a combined sewer system and currently has capacity of up to 140 million gallons per day (MGD). The liquids train treatment processes include primary clarification, high purity oxygen activated sludge (HPOAS) basins, secondary clarification, and chlorine disinfection. The solids treatment train includes gravity thickening, anaerobic digestion of a small fraction (~10 percent) of the total solids generated through temperature-phased digesters, centrifuge dewatering and post-lime stabilization of all biosolids to produce Class B biosolids. MBEC generates 55 dry tons of biosolids per day that is hauled offsite and land applied. Energy Audit MBEC recently completed a comprehensive Energy Audit to determine ways that both energy consumption and chemical use at the facility could be reduced. The audit evaluated energy and chemical savings from three potential major improvements in addition to several minor ones. The major improvements are based on:

*Installing thermal hydrolysis (THP) to enhance the digestion process and produce more biogas;

*Achieving complete nitrification to avoid very large hypochlorite expenditures due to nitrite lock; and,

*Converting the plant to diffused aeration with blowers and fine bubble diffusers. First, THP was evaluated as an anaerobic digestion enhancement alternative due to limited digester capacity and tight footprint at MBEC. Adding THP to the existing digestion system allows all sludge to be processed through the anaerobic digestion system, cuts biosolids generated in half (~$1.5M annual savings in hauling costs), eliminates lime use (~$570K annual savings in lime costs), produces Class A biosolids and boosts biogas production. The analysis recommended renewable natural gas (RNG) as the most favorable use of the biogas, given the potential for revenue generation. The net biogas available for RNG production is approximately 570 scfm and could account for $4M in annual revenue for the City at current RIN rates. Operational cost savings in the solids train are shown in Figure 1. Nitrification is difficult to achieve under the current MBEC configuration in dry weather conditions due to the short retention time and low pH conditions that are endemic to HPOAS systems. Meeting the 15 mg/l monthly average permit limit is difficult. In addition, the low pH conditions of HPOAS-based treatment can inhibit the growth of nitrite oxidizing bacteria, leading to high concentrations of nitrite in the secondary effluent. Nitrite has a high chlorine demand is responsible for over 50% of the chlorine consumed at MBEC. The alternatives analysis found that the most effective means of meeting MBEC's nitrification permit is by using membrane aerated bioreactor (MABR) technology. Utilizing MABRs avoided nitrite production, as the nitrifiers were fixed on submerged membrane cassettes inside the anoxic zone of the existing system, which has a higher pH, and results in ammonia removal without nitrite formation. Projected effluent quality from the plant SUMO model is shown in Figure 2. In addition, the analysis found that the lowest lifecycle cost option for replacing the oxygen plant at MBEC was to install blowers and fine-bubble diffusers as part of a conversion to aeration. The change to aeration supports the nitrification MABR recommendation, as the MABR reduces the soluble COD entering the aeration zones (reducing demand) and the switch to aeration removes the low pH conditions, reducing the residual nitrite formation. The annual average energy consumption from secondary treatment after the changes will be ~7 million kWh annually, a roughly 65% drop from the nearly 20 million kWh used at present. Conclusion The improvements listed here for MBEC result in very large operational cost savings throughout the treatment plant. The estimated capital cost for the program are $136M. See Figures 3-5 for capital cost estimates for the solids train, liquid train, and the combined program, respectively. The major operational cost savings are estimated as:

*$4M in annual RIN revenue from RNG

*$2.2M annually in reduced sodium hypochlorite use

*$1.5M annually in reduced cake hauling costs

*$900k annually in secondary treatment power costs Note that a $570k reduction in lime addition costs are roughly balanced out by increased polymer use, increased maintenance and a small increase in power in the solids train. These savings total $8.6M annually. The end result of the savings is a rare outcome in the industry — a major capital improvement program with a financial payback. A simple payback analysis has the entire improvement program paying for itself within 15 years. Further, the payback for the improvements is not solely dependent on generating revenue from RIN sales. The estimated simple payback without RIN revenue is 30 years. When the true costs of a 'do nothing' option are also included ($25M to replace the end-of-life oxygen plant, and an alternate solution to meet increasing difficult ammonia limits and sludge disposal challenges) the true payback becomes even shorter. However, this is not a project pursued solely due to a favorable payback. The City will also be more reliably able to meet their NPDES permit, will replace aging assets, and will be generating both cleaner water and Class A biosolids

This paper was presented at the WEFTEC 2024 conference in New Orleans, LA October 5-9.

SpeakerSteele, Paul

Presentation time

08:30:00

08:50:00

Session time

08:30:00

10:00:00

SessionEnergy Conservation: From a Want to a Must

Session number305

Session locationRoom 346

TopicEnergy Production, Conservation, and Management, Facility Operations and Maintenance, Intermediate Level, Resilience, Safety, and Disaster Planning

Author(s)

Steele, Paul, Ohemeng-Ntiamoah, Juliet, Shen, Emma, Constantine, Tim, Johnson, Thomas

Author(s)P.M. Steele1, J. Ohemeng-Ntiamoah1, E. Shen2, T. Constantine3, T. Johnson4

Author affiliation(s)1Jacobs, TN, 2Jacobs, ON, 3Jacobs, MT, 4Jacobs, NC

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159720

Volume / Issue

Content sourceWEFTEC

Word count22

Hybrid Modeling and Diagnosis to Reduce N2O Emissions at WRRFs

Abstract

Introduction
A key challenge in monitoring N2O at WRRFs is managing and analyzing large amounts of data to develop mitigation insights and inform operations. This paper presents a unique hybrid modeling approach that combines data-driven models with process knowledge to predict liquid-phase N2O concentrations. The tool has been successfully applied to two full-scale, long-term monitoring datasets; information about the two facilities is summarized in Table 1, and Figures 1 and 2.

The focus of the project was identifying drivers for N2O generation using diagnostic tools and not simply fitting a model to data. The project aimed at answering the following questions:
- Why did a specific N2O peak happen, and which variables are associated with it?
- Which operational settings should be changed to reduce or prevent an N2O peak?
- Is there a model that describes the correlation between measured variables that can explain N2O behavior and can be used to mitigate N2O emissions?

Methodology
Proprietary code was developed and applied to automate the building and training of a PLS (Projection of Latent Structures) model via the NIPALS (Non-linear Iterative Partial Least Squares) algorithm. The model is integrated with diagnostic tools that objectively evaluate model performance, guide model iterations, and identify effective control handles to mitigate N2O emissions. A key statistic used was the percent sum of squares explained in the input (%SSX — the goodness of fit for input data) and output (%SSY — indication of model output consistency) (Figure 3). Variable Importance Plots (VIP) were used to rank the most information-rich variables and identify which variables could be removed (Figure 4). Contribution plots were used to further analyze specific events by ranking the variables with the highest contributions to the result data point (Figure 5) - this ability to examine specific events is a key advantage of the PLS modeling approach.
A stepwise and iterative procedure was applied to develop a robust and reliable hybrid model (Figure 6).
A typical iteration identifies that the model is not providing a good fit for a specific section of the data, which would trigger a discussion among domain experts and typically lead to the identification of data issues or information to add to the model inputs. This iterative procedure guided the project team in adding domain expertise in process and control. Examples are the translation of operational information (e.g., logbooks, operator interviews) into a digital format to feed into the model (i.e., removing data for events such as sensor cleaning/calibration, or unreliable data based on operator insights).

Duffin Creek WPCP Results
The performance of the first model (%SSX: 28.9) was improved with every iteration with the last model iteration explaining 72% of the data (Figure 7). Key improvements were data cleaning (based on plant information, statistical analysis, and identification of a faulty temperature sensor for the N2O probe (Figure 8)), and the addition of domain expertise such as influent load calculations and feeding DO control errors (Figure 9). The final model achieves a very good fit and follows diurnal and seasonal variations, with an average tank N2O Emission Factor (EF) of 0.7%.

The diagnostic tools identified aeration control as the main driver for N2O accumulation. An aeration improvement project is currently ongoing and the impact on N2O will be closely monitored. The second highest ranking could be linked to oxygen ingress in the pre-anoxic zone during mixer maintenance; the plant has been advised to minimize airflows into the pre-anoxic zones.

Elmira WWTP Results
Model iterations improved the goodness of fit from 43.8% to 64.9% SSX explained (Figure 11). Key improvements were achieved by cleaning data and removing variables without relevant information. The largest improvement was from removing the datasets where the performance was disrupted during MABR commissioning and MABR aeration system failure due to cold weather. Results indicate relatively low N2O emissions from the bioreactors downstream of the MABR with occasional spikes, with the average N2O EF at 0.42%.

Diagnosis of the results showed aeration as the main contributor to N2O accumulation and improvements have been recommended. A well-operated MABR seems to keep the downstream N2O emissions low, however, the MABR off-gas could contribute an additional 30% to the N2O emissions based on limited off-gas data. Other N2O peaks could be linked to wet weather events and it has been recommended to investigate controls and process optimization during and after such events.

Summary and Next Steps
The hybrid models were able to explain 65 to 70% of the measured N2O and accurately predicted the trends and diurnal variations. The model allows for multivariate analysis to identify key operational parameters with the highest importance on the measured N2O, which combined with process knowledge, enables extraction of actionable information to develop potential operational strategies to mitigate N2O emissions. At the Duffin Creek WPCP, recommended improvements to the aeration control system will be implemented in spring 2025 together with ammonia-based aeration control, providing the opportunity to optimize aeration energy efficiency while minimizing process N2O emissions; some of the mitigation insights identified by the model will be tested.

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

Presentation time

16:00:00

16:15:00

Session time

15:30:00

17:00:00

SessionDecarbonizing Water: Mathematical Modeling and Digital Twins to Reduce N2O Emissions from WWTP

Session locationMcCormick Place, Chicago, Illinois, USA

TopicProcess Control and Modeling

Author(s)

Shen, Emma, Miletic, Ivan, Rieger, Leiv, Brandimarte Molleta, Lucas, Flores, Jesus, Green, Joe, Medd, Jeff

Author(s)E. Shen1, I. Miletic1, L. Rieger1, L. Brandimarte Molleta1, J. Flores1, J. Green2, J. Medd3

Author affiliation(s)Jacobs1, Regional Municipality of Durham2, Regional Municipality of Waterloo3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Sep 2025

DOI10.2175/193864718825159915

Volume / Issue

Content sourceWEFTEC

Word count11

Tacking Fugitive Methane Emissions at WRRFs - Global Lessons

Abstract

Fugitive methane emissions from sludge treatment and biogas handling processes are a significant source of GHG emissions, particularly critical for WRRFs with anaerobic digestion. Sewer methane production can also contribute to significant GHG emissions for the entire wastewater systems. There is lack of consistent methodologies for quantifying and monitoring these emissions in North America, which could lead to over- or (more likely) underestimation of their contributions to the overall GHG footprint. Ongoing work in Europe show the criticality of direct methane emissions monitoring, and operational approaches to mitigate methane emissions through regular survey, proactive leak detection and repair and independent certification. This session will present an overview of the sources of fugitive methane emissions in collection systems and at WRRFs, available methodologies in monitoring and quantifying fugitive methane emissions (including challenges and issues), and practical tips for reducing methane emissions based on global case studies.

This paper was presented at WEFTEC 2023 in Chicago, IL.

SpeakerLake, Amanda

Presentation time

13:30:00

15:00:00

Session time

13:30:00

15:00:00

SessionGlobal Approaches to Tackling Fugitive Methane Emissions

Session locationRoom S402a - Level 4

TopicIntermediate Level, Sustainability and Climate Change, Water Reuse and Reclamation

Author(s)

Lake, Amanda

Author(s)A. Lake 1; C. Scheutz 2 ; B. Beelen 3; E. Shen 4; P. Nielsen 5; A. Vellacot 6; A. Fredenslund 7; K. Kraemer 8;

Author affiliation(s)Jacobs 1; Technical University of Denmark 2 ; GHD 3; Jacobs 4; VCS Denmark 5; Jacobs 6; Technical University of Denmark 7; GHD 8;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825158977

Volume / Issue

Content sourceWEFTEC

Word count10