Nangle, Tom

Tom is Brown and Caldwell’s Solids National Specialty Leader, Chair of WEF’s Pre-digestion Hydrolysis Focus Group, and Co-Chair of WEF’s High Performance Digestion Task Force. Tom has planned, designed, provided construction oversight, commissioning, and optimization services for biosolids projects throughout the Eastern United States. And he is passionate about the resource recovery potential within water reclamation facilities, especially the beneficial reuse of biosolids, biogas utilization, and nutrient harvesting.

Titles from this speaker

Next Generation Digestion for the Fugitive Methane Era

Abstract

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

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

SpeakerNangle, Tom

Presentation time

10:45:00

11:15:00

Session time

08:30:00

11:45:00

SessionGreenhouse Gas Emissions at Wastewater Treatment Plants

Session number11

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicAnaerobic co-digestion, Biogas, fugitive methane emission

Author(s)

Nangle, Tom

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

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

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159475

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count9

Description: One South Carolina Utility's Biosolids Plan: Forging a Path Amidst Rising Tip Fees...

One South Carolina Utility's Biosolids Plan: Forging a Path Amidst Rising Tip Fees and Regulatory Uncertainty

Abstract

Spartanburg Water, through the Spartanburg Sanitary Sewer District (SSSD), owns and operates eight wastewater treatment facilities (WWTFs) throughout Spartanburg County. Sludge generated by the seven smaller facilities are typically hauled to the A. Manning Lynch WWTF (AM Lynch), where it is blended with grease trap waste (GTW) that is also hauled in from around the County, then centrifugally dewatered. The dewatered cake is then hauled to two local landfills. SSSD wanted to take a fresh look at their biosolids management strategy due to: -Rising landfill tip fees and the risk landfills can stop accepting sludge with little notice -Regulatory uncertainty, especially around per- and polyfluoroalkyl substances (PFAS) -Changing biosolids treatment technology landscape A Biosolids Master Plan and Roadmap was developed that compares the current biosolids management approach to a range of potential new technologies and beneficial end uses. The master plan approach first evaluated the local market for biosolids derived products, which informed potential management strategies and technology selections. A detailed evaluation was conducted of SSSD's current and preferred sludge management practices and critical existing processes to customize the alternatives to SSSD's on the ground realities. A large list of alternatives was screened incrementally down to the five most attractive strategies, which then received a cost and non-cost analysis. BC developed an implementation plan that immediately reduces costs and risks to SSSD's sludge management program, while providing flexibility to respond to regulations and market conditions that may further alter the sludge management landscape in the coming years. The result is a Biosolids Master Plan that identifies near-, mid-, and long-term options for biosolids management that are informed by the existing and projected regulations and market demand for biosolids, and customized to SSSD's size, operating budget, and preferences. The plan includes a dynamic roadmap for implementing the selected biosolids management strategies, with timing of selected near-, mid- and long-term strategies informed by various triggers. Biosolids Market Study The biosolids market study shed light on actual demand for different biosolids derived products (compost, dried Class A biosolids, Class B Cake, and biochar) in SSSD's local market. This helped inform the attractiveness of different biosolids management strategies and technologies. Evaluating actual local market conditions first reduced risk and uncertainty around making capital investments to access different biosolids end use markets. In addition to identifying markets for beneficial reuse, the team also evaluated alternative disposal options for SSSD's sludge and separate processing of GTW to improve dewatering operations. Regionalization Considerations Detailed evaluation was conducted to determine sludge production and projections at all plants, and trucking logistics to bring thickened sludge to the centralized solids processing facility at AM Lynch WWTF. The sludge projections and AM Lynch mass balance indicate that the sludge storage tank is running out of capacity to effectively equalize, blend, and decant SSSD's sludge and GTW prior to centrifugal dewatering. By 2025, there will not be enough capacity to equalize average week sludge loads and maintain decant operations. If decant abilities were completely lost, SSSD would have to increase centrifuge weekly run time by 55%, and would experience reduced centrifuge performance (e.g., lower cake solids concentrations), both of which will increase operational costs. Table 1 outlines options to increase sludge storage to allow for reliable decanting in the future and to provide peak week equalization to limit required processing capacity of downstream equipment. Technology Screening Fifteen (15) technologies were identified as being attractive for SSSD. Eight (8) technologies remained after a pre-screening effort, which eliminated any technologies that: -Could not achieve Class A Biosolids -Increased the volume of biosolids to manage -Were embryonic (did not have a successful full-scale municipal sludge installation in the US) Conceptual designs (equipment sizing and site plans), along with pros and cons were presented for the eight (8) prescreened options in the Initial Screening Workshop. At the workshop, the team came to consensus on the five (5) alternatives to advance for detailed evaluation; the alternatives and their reason for selection are summarized in Table 2. Long-Term Alternatives Analysis Lifecycle cost and non-cost analyses were conducted for the five (5) alternatives. Sensitivity analyses were performed on landfill tipping fees, chemical prices, land application cost. Off-site composting by a third party had the best non-cost rating, lowest capital costs, and lowest operating costs of all the options being considered. The biosolids market study determined that compost also had the greatest local market demand. There is also strong interest from two experienced and successful large-scale composters to build a new facility and have SSSD as their main client. For all these reasons, BC recommended moving forward with off-site composting immediately, as it will reduce risk and should reduce biosolids management costs on day one. BC is currently assisted SSSD in releasing an RFP for off-site 3rd party processing services. A summary of considerations for each alternative will be discussed in the manuscript. Biosolids Road Map BC developed an implementation plan that immediately reduces costs and risks to SSSD's sludge management program, while providing flexibility to respond to regulations and market conditions that may further alter the sludge management landscape in the coming years. Near-Term Recommendations (2022-2025): SSSD should focus on diversifying their solids management, improving sludge storage and dewatering at AM Lynch, and monitoring regulations on PFAS. This includes: -Letting an RFP for off-site third-party processing of the majority of SSSD's dewatered cake. -Evaluate third party processing of the GTW accepted and stored at AM Lynch, as well as evaluating centrifuge optimization options. -Build a redundant sludge storage tank to provide required volume for equalizing peak week loads and to continue decanting operations. SSSD is currently moving forward with all of these recommendations. Mid-Term Recommendations (2026-2035): SSSD should re-evaluate this biosolids master plan and make capital improvements necessary for aging equipment. This includes: -A master plan update that evaluates how satisfied SSSD is with the off-site third-party composting contract, provides an updated regulatory landscape regarding PFAS's impact on biosolids beneficial reuse, quantifies the increased costs and risks of trucking sludge (which will inform both sludge hauling to AM Lynch, and trucking of dewatered cake from AM Lynch), as well as an updated evaluation of landfill access/fees and the local biosolids market. -A condition assessment of critical equipment should be included prior to or as part of this master plan update. -Replace the two older centrifuges and their ancillary systems, as well as any other capital improvements identified as part of the condition assessment and master plan update. Long-Term Recommendations (2036-2045): Given the current regulatory uncertainty, and the luxury of pursuing off-site third-party composting to reduce risks and control sludge management costs over the next decade, no significant investments that would alter the sludge handling process at AM Lynch are recommended. The recommendations reduce risks and control costs in the near- to mid-term and buys SSSD time to see how PFAS regulations will unfold, how expensive and restrictive landfill disposal of sludge becomes, and how the many new advanced sludge destruction technologies perform at full scale municipal WWTFs in the US. The long-term recommendations will be decided in the biosolids master plan update schedule for 2029-2030, which will be based on the outcome of the above variables, as well as results of the condition assessment. Capital Improvements Planning: To facilitate CIP planning, three alternative budgets of solids management capital investments were developed associated with these recommendations: 1.Recommended budget assumes off-site composting by a third-party remains the long-term biosolids management strategy for SSSD 2.This alternative budget represents investments needed if market triggers result in SSSD adding a thermal belt dryer at AM Lynch to reduce costs and risks. 3.This alternative budget represents investments needed if regulatory triggers result in SSSD adding a sludge destruction technology at AM Lynch to reduce costs and risks.

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

SpeakerNangle, Tom

Presentation time

9:00:00

9:30:00

Session time

8:30:00

11:15:00

SessionSession 18: Managing Biosolids in the Carolinas

Session number18

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicManaging Biosolids in the Carolinas