Munson, Anna

Anna Munson is a Senior Principal Engineer in Hazen and Sawyers Saint Paul, Minnesota office. She is a member of Hazen's Biosolids Practice Group and has the privilege of working on biosolids and residuals projects across the US while managing a handful of local water and wastewater projects. She has been an active member in WEF and her Member Association, Central States Water Environment Association, throughout her career.

Titles from this speaker

Description: Cost Implications of PFAS Destruction in Biosolids: A Case Study from the Minnesota...

Cost Implications of PFAS Destruction in Biosolids: A Case Study from the Minnesota Pollution Control Agency

Abstract

Introduction and Objectives Our scientific understanding of per- and poly-fluoroalkyl substances (PFAS) in our environment has evolved rapidly in the last several years and PFAS have increasingly gained attention from the public, scientiï¬c, and regulatory sectors due to their carcinogenic and reproductive and endocrine disruptive nature. Previous research has illustrated that water resources recovery facilities (WRRF) are notable PFAS emission routes to the environment, both liquid and solid discharge routes. Despite industrial phasing-out of some PFAS and increasing source management of industrial discharges, PFAS are expected to be present in wastewater solids for the foreseeable future. According to Northeast Biosolid and Residual Association (NEBRA), more than seven million dry tons of wastewater solids were produced at WRRFs in 2004 and solids management practices have resulted in the release of approximately 3000 kg PFAS per year to agricultural lands and landï¬lls (Venkatesan and Halden, 2013). Much work has been done to develop and demonstrate wastewater treatment technologies to destroy PFAS compounds (mineralize to non-fluorinated end-products) in wastewater solids, but few studies have documented the practical application of PFAS destruction technologies for wastewater solids or estimated the cost of implementing those technologies. Our team conducted an evaluation for the Minnesota Pollution Control Agency (MPCA) to document the technology options that could be implemented today to remove and destroy PFAS within municipal wastewater effluent, compost contact water, landfill leachate, and municipal wastewater solids. The objectives of this project were to: -establish a framework for determining which technologies meet the definition of commercially available and effective for PFAS destruction -conceptualize upgrades to destroy PFAS at existing WRRFs -estimate the cost of completing these upgrades for a range of WRRF capacities. Systems were conceptualized for facilities ranging from 0.1-10 MGD. For capacity greater than 10 MGD, a regionalized option was considered. This paper will highlight the findings from wastewater solids portion of the study. This information will be valuable for utilities looking to implement PFAS destruction technologies as regulations around PFAS evolve rapidly. Target PFAS Initial work for the study involved selecting a set of PFAS to represent the range of PFAS known or predicted to be in wastewater solids. Selected PFAS are well-described in PFAS treatment literature, frequently detected in wastewater solids, and diverse in chain length and functional groups. Table 1 lists the selected compounds, assumed typical and high concentrations in wastewater biosolids, and associated target post-treatment. The selected PFAS are generally long-chain perfluoroalkyl acids (PFAAs) or are precursors to PFAA formation, which research has shown to partition into solids. Representative concentrations of PFAS were selected from available literature. Technology Screening PFAS destruction technologies were screened for their ability to consistently remove at least one identified PFAS to below the currently accepted laboratory detection limit, as outlined in Table 1. Technologies were further screened by their readiness for full-scale implementation. Wastewater solids PFAS destruction technologies passing the screening included pyrolysis with thermal oxidation of the process gas, gasification with thermal oxidation, and supercritical water oxidation (SCWO). Pyrolysis and gasification systems were considered to use similar enough equipment to be evaluated as a single alternative for conceptual design. Pyrolysis/gasification systems included a thermal dryer as part of the equipment assembly since both technologies require high solids content. Conceptual Design and Cost Estimating A conceptual design was created for both short-listed PFAS destruction alternatives and for solids production rates of 1, 5, and 10 dry tons per day at a given WRRF, corresponding roughly with the plant influent flow rates used for the liquids portion of the study. The feed solids to the pyrolysis/gasification process were assumed to be dewatered to 25 percent total solids. For SCWO, the feed solids were assumed to be screened and dewatered to 15 percent total solids. Construction cost estimates (AACE Class 5) were prepared from recent project estimates and input from vendors. The construction costs were plotted against the system feed rate to create cost curves for each alternative. One example of a cost curve for pyrolysis/gasification is provided as Figure 1. The construction cost curves for pyrolysis/gasification and SCWO, and parameters used to develop each, will be included in the paper. Additionally, a conceptual design for a regional pyrolysis/gasification facility for wastewater solids was developed to represent another approach for utilities. Our findings showed that due to high costs associated with PFAS treatment, regional approach might become viable for smaller facilities (facilities less than 10 MGD). A regional facility would receive dewatered solids from two or more individual WRRFs within a reasonable hauling distance. Fifty dry tons per day was assigned as a representative capacity for a regional PFAS destruction facility. Operation and maintenance costs estimated for recent pyrolysis/gasification projects were assembled to select representative 2022 O&M costs for a 50 dry ton per day facility. A 20-year lifecycle cost analysis was prepared and tested for sensitivity to variations of the tipping fees and interest rates. This paper will include the results and conclusions from the lifecycle cost analysis of the regional facility concept. Conclusion This study documents the cost of implementing currently available technologies to destroy PFAS in wastewater solids. For pyrolysis/gasification, the O&M costs per dry ton trended lower as the system capacity increased, indicating that smaller utilities could reduce costs if they formed a partnership and developed a regional PFAS destruction facility. Demonstration testing of SCWO systems is expected to provide evidence to clarify if similar results can be expected for SCWO systems.

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

SpeakerMunson, Anna

Presentation time

10:45:00

11:15:00

Session time

8:30:00

11:45:00

SessionSession 10: PFAS Challenges and Treatment

Session number10

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicEmerging Issues (PFAS, Microplastics, Covid, etc.)

Author(s)

A. Munson

Author(s)A. Munson1, D. Dursun2, M. Blate3, M. Abu-Orf4, A. Ling5, R. Vermace6, K. Wolohan7, S. Kyser8,

Author affiliation(s)Hazen and Sawyer1; Hazen and Sawyer2; Hazen and Sawyer3; Hazen and Sawyer4; Barr Engineering5; Barr Engineering6

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158810

Volume / Issue

Content sourceResiduals and Biosolids

Word count17

Description: Flexibility During Design — How Goleta Sanitary District (GSD) adapted their...

Flexibility During Design — How Goleta Sanitary District (GSD) adapted their long-term bioenergy recovery strategy to rapidly changing external factors

Abstract

This presentation will demonstrate how Goleta Sanitary District (GSD) benefited from having a flexible bioenergy recovery plan and analytical tools to adapt to changing external factors such as funding availability, capital costs, biosolids hauling costs and evolving emission regulations. Attendees will learn the value of revisiting previous decisions when new data becomes available or conditions change and the advantage of having an analysis tool to visualize new outcomes. GSD developed a Biosolids and Energy Strategic Plan (BESP) in 2019 to better capitalize on the energy available from gas produced by their anaerobic digesters at the Goleta Water Resource Recovery Facility (WRRF). The project team used an interactive energy, mass, and financial balance tool (Energy Balance and Analysis Tool - EBAT) to evaluate the benefit from multiple bioenergy recovery alternatives including a combined heat and power (CHP) system, renewable natural gas and sludge drying. Digestion expansion, gas storage and CHP were recommended for the near team. Construction of a biosolids dryer was recommended for solids management about 10 years after digestion expansion to reduce hauling costs and produce a Class A product. GSD began preliminary design work in 2020 to implement the recommendations from the strategic plan. The design included a CHP system with a 450kW digester gas fueled engine generator, digester gas treatment, emissions controls to meet the regional emission limit rules, and a gas storage sphere to provide a consistent gas supply and operational flexibility for the CHP engine. The CHP system would initially operate at 75 percent of its rated output, increasing to full output upon implementation of the planned fats, oils, and greases (FOG) co-digestion program. During the preliminary design phases several external factors changed that extended the payback period of the recommended bioenergy recovery strategy (CHP), including: 1.Capital costs of the CHP engine increased 5-10 percent due to the increasing costs of raw materials. 2. Dialog with the Santa Barbara County Air Pollution Control Department (SBCAPCD) indicated that the 450kW engine would fall under the 'Best Achievable Control Technology' (BACT), requiring continuous emissions monitoring system (CEMS) and a higher level of emission reduction equipment which would increase operating costs. 3. Biosolids disposal and hauling costs increased at a higher rate than expected and could justify expediting the sludge dryer installation. As these conditions evolved, the EBAT model was used to re-examine the long-term bioenergy recovery strategy to determine if an alternative strategy would provide a higher level of value. The team tested many different energy scenarios simultaneously. Scenarios were various combinations of one 450 kW engine generator, one or two 160 kW engine generators, SCR and CMS, and funding received from the Self Generation Incentive Program (SGIP). GSD and the design team discussed the risks and benefits of moving forward with a larger system compared to a smaller system such as availability of grants to fund the project, capital at risk, disruption to operations during construction and adaptability to capitalize on future plant modifications such as co-digestion. As demonstrated in Figure 1, the analysis found that the 160kW CHP system provided a shorter payback period than the 450kW system (13 years vs 22 years) primarily due to the lower capital costs per kW, which was achieved by removing the need for digester gas storage and the continuous emissions monitoring system. While the smaller CHP system would not use all the digester gas produced, the addition of a thermal dryer in the near term (at about 5 years) could provide a means to beneficially utilize the digester gas volume that exceeds the CHP capacity. To test this idea, the team again returned to the EBAT model, incorporating the dryer into the financial and energy balance calculations. The adjustable inputs within the model such as dryer uptime, dryer installation year, FOG co-digestion volume and revenue from FOG tipping fees were varied to understand the individual and cumulative impact on the financial outcome of installing a dryer in the near term. GSD used the interactive, Power-BI based dashboard to experiment independently with CHP sizes, dryer installation years and capital cost reductions from funding opportunities. Figure 2 is a screen shot of the EBAT dashboard. Ultimately, the EBAT model guided GSD to select the smaller CHP system as the bioenergy recovery strategy that provides them higher value with less capital risk. The installation year for a thermal dryer is still under evaluation. This case study illustrates the importance of continuously evaluating and comparing different bioenergy alternatives as conditions such as capital costs, emission regulations, hauling costs, market conditions and other variables evolve during the development of a bioenergy recovery project. The development of a flexible long term bioenergy recovery plan as well as an interactive bioenergy recovery analytical tool provided GSD a means to easily navigate changing conditions and ensure the optimal solution in implemented.

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

SpeakerMunson, Anna

Presentation time

9:30:00

10:00:00

Session time

8:30:00

11:45:00

Session number08

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicDecision Making, Design, Energy Neutrality, Co-digestion, Thermal Drying, Solar PV, Energy Storage, Interactive Dashboard

Author(s)