Auerbach, Eric

Mr. Auerbach several degrees including a BS in Biological Engineering from Cornell University, a MS in Environmental Engineering from the University of Wisconsin, and a MS in Energy Engineering from the University of Illinois Chicago. He has worked at Arcadis for 18 years developing biosolids resource recovery systems at some of the largest WRRFs in the country and has now recently moved to London to set his sights on global domination. Seeing as this is the last talk of the conference, Eric is just happy you chose to stay and listen instead of heading out early to hit the airport bar.

Titles from this speaker

Description: Biogas Action Planning in Tallahassee--Plans for the Future with Improvements for...

Biogas Action Planning in Tallahassee--Plans for the Future with Improvements for the Now

Abstract

INTRODUCTION The City of Tallahassee developed a biogas and energy optimization plan for its Thomas P. Smith Water Reclamation Facility (TPS WRF). The goals of this plan included optimizing imports of organic wastes to anaerobic digesters and maximizing biogas energy use in a way that is operationally sensible, economically beneficial, and promotes sustainability. The cornerstone of this plan was the development of a Solids and Energy Flow Model a tool that dynamically and holistically tracks flows of solids and energy in its various forms throughout the TPS WRF. Using this methodology, a multi-phased improvement plan was developed to address immediate issues with biogas blowers and improve short term biogas utilization rates, while also laying out a long-term path for a more sustainable future. The identified improvements included: -Replacing existing digester blowers to allow short term use of biogas in onsite thermal dryers. -Implementation of new FOG receiving with feeds to individual digesters. -Implementation of Renewable Natural Gas (RNG) to fuel City owned vehicles. BIOGAS BLOWERS TO FUEL THERMAL DRYER A previous plant upgrade had installed new digesters and a new rotary drum thermal dryer. Biogas blowers intended to be used to fuel the dryer failed during this project's startup and were never fully put into service. Recurring failures in the blower seals were observed within weeks of operation. Due to these failures the system was never started up on biogas and the dryer has been run on natural gas. Detailed investigations into the blower failures revealed that moisture buildup due to the specific blower location and elevation were the cause of recurring failures. Blowers were located in close proximity to the raw biogas draw off from digesters, leaving little pipe length to cool gas and remove condensate (Figure 6). Blower suction elevations were also located at the low point in the piping system which exacerbated the buildup of condensate in the blowers. Improvements included reconfiguring biogas piping to include moisture knockouts while installing new blowers with higher suction elevations (Figure 10). This upgrade will allow biogas to be used in the dryer as intended saving significant amounts of natural gas use (Figure 9) in a short-term timeline. This project was designed and is currently in the construction phase. During design it was discovered that the rotary drum dryer controls were never officially configured to use biogas. The Design Team worked with the dryer manufacturer to devise comprehensive and unified control strategies for the entire biogas system including coordinating dryer firing rates based on digester dome pressure. NEW FOG RECEIVING AND RNG The longer-term improvements identified included upgrades to the FOG receiving and sludge pumping systems as well as the implementation of RNG. Currently the plant receives FOG and septage in a single receiving station. Staff reported O&M issues with this station being undersized and having long piping runs to connect to the Blended Sludge Tank for distribution to digesters (Figure 3). An item identified during investigations was that FOG is currently blended with sludge in the Blended Sludge Tank (Figure 11) making it impossible to segregate FOG to individual digesters. This is important because the plan called for segregating FOG feed to individual digesters to maintain D3 RIN classification for a portion of the biogas directed to a future RNG system. The plan included a new trucked waste receiving station dedicated only to FOG. This new station would be located in closer proximity to the digesters and would provide individual feed pumps to send FOG to individual digesters (Figure 13). It was determined that Digester #3 that is currently being rehabbed could accept all the existing FOG loads received while leaving the remaining 3 plant digesters 'untainted' by FOG and able to produce D3 RINs. The plan called for specific enhancements to Digester #3 feed piping and pumping allow this unit to become the 'FOG heavy' digester. RNG was targeted as the long-term biogas utilization strategy at the TPS WRF due to several beneficial circumstances. First is the fact that the City of Tallahassee owns the natural gas local distribution utility pipeline. City NG pipeline staff have expressed high interest and willingness to facilitate a pipeline interconnection with the TPS WRF at a reasonable cost and terms while avoiding lengthy negotiations with 3rd party pipeline operators. The second is that the City already owns and operates a CNG sanitation fleet, giving the project a captive vehicle user for the RNG again without the need to negotiate terms with a 3rd party. The plan examined projected RNG production rates and compared them to the City fleet fuel use in Diesel Gallon Equivalents (DGE) per day. The fleet was found to have a steady consumption rate on a weekly and yearly basis that approximately matched the production of the proposed RNG system. With the benefits of these City owned partner utilities the RNG project was found to have significant long-term economic and sustainability benefits over using the biogas in the thermal dryer. CONCLUSION The plan provided Tallahassee with both immediate action items for improving their biogas system while laying the foundation for a more sustainable future. The biogas blowers to fuel the dryer could be implemented on a short timeline (~1 year) at a small cost (~$1 million) and would save an estimated 60,000 mmbtu/year of NG use at a savings of $570,000/year. This project is already in construction to provide short term benefits and operational flexibility while the larger and long-term projects for FOG receiving and RNG production are being developed.

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

SpeakerAuerbach, Eric

Presentation time

9:30:00

10:00:00

Session time

8:30:00

11:45:00

SessionSession 09: Biogas

Session number09

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicSustainability and Resource Recovery

Author(s)

E. Auerbach

Author(s)E. Auerbach1, M. Costa Tomazelli2, S. Lee3, 4,

Author affiliation(s)Arcadis1; City of Tallahassee2

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158797

Volume / Issue

Content sourceResiduals and Biosolids

Word count14

Description: Biosolids Planning for an Uncertain Future - How Regulatory Drivers and Technology...

Biosolids Planning for an Uncertain Future - How Regulatory Drivers and Technology Developments are Influencing Long-Term Infrastructure Decisions

Abstract

Introduction The current era is challenging to plan for long-term biosolids infrastructure upgrades. Over the past decade, many of the traditional solids management outlets have dwindled, with incinerators shutting down due to increasingly strict air regulations, and many landfills starting to limit biosolids loads. Land application is one of the strongest remaining pillars of traditional biosolids management, with its relatively low costs and effective nutrient recycling making it a favorable option. As of 2021, 43% of all biosolids in the USA were land-applied. Given the uncertainty around future regulations restricting land application due to PFAS and other emerging contaminants, this outlet is also facing its existential crisis. While confidence in traditional biosolids outlets waver, at the same time many utilities across the country are grappling with their fast-approaching need for renewal of solids infrastructure. Many of these solid systems built in the 1970s have needed capital upgrades repeatedly deferred to the point that major investment is now needed as these systems reach the end of their service life. Additionally, there has been attrition in O&M staffing across the country due to Covid and other global forces. With limited experienced O&M staff, it becomes difficult to embrace advanced technology, especially purported to destroy PFAS which are very early in their development phase and whose efficacy is as unclear as the future regulations they intend to address. Waiting for these regulatory and technology questions to be answered would be ideal but not feasible for many utilities whose time to act is now. The case study for the City of Toledo, OH forms the basis of this paper. Toledo is planning and procuring funding for one of the largest upgrades in its Bay View WWTPs history. This impending solids system upgrade is viewed as an opportunity to enhance sustainability and reduce GHG emissions by recovering more renewable energy from biosolids. There is also trepidation, however, over pouring major investments into digesters with the looming uncertainty around land application due to future federal PFAS regulations. Existing Conditions This paper presents an overview of the recent solids planning effort for the Bay View WWTP (ADF - 68 MGD). In 2022 the City developed a facility plan that included demolishing plant digesters (built in the 1930s) to clear space for new liquid stream process. The plan included constructing a new solids facility on new plant land created by filling part of the bay on which the WWTP sits. This WWTP currently produces ~ 40,000 wet tons of Class B biosolids annually, which consists of combined thickened primary and WAS that is anaerobically digested and dewatered to Class B cake. These biosolids are land-applied using a 3rd party cake management partner, while occasional loads are sent to landfills during seasonal outlet restrictions. The biogas generated is utilized on-site for digester heating with boilers. Toledo had previously shown advanced thinking and ambition in energy recovery as it constructed a combined cycle turbine CHP plant at the WWTP designed to run of digester gas and landfill gas piped in via a trans-city pipeline. This facility was sitting currently unused due to lack of sufficient fuel, as landfill gas volumes were less than half of the anticipated design values. The City engaged the engineering team to explore various solids processing alternatives and recommend a path forward for their new solids processing facility. The team focused on maximizing energy recovery and enhancing sustainability while recognizing that the City was staff-limited without capacity to take on new advanced technology adding considerable O&M effort. Another driver was to reduce final solids volume and develop alternatives centered around Pyrolysis and Gasification addressing PFAS concerns. Since the City was capital and staff limited, these alternatives were developed with the leading technology manufacturers as 3rd party turnkey projects to be owned and operated by a 3rd party commercial entity. Methods A comprehensive and holistic solids and energy modeling effort was developed to understand complex and interacting impacts of implementing various solids and energy processes in one framework (Figure 1). Each potential combination of processes was quantitatively analyzed for annualized cost, greenhouse gas (GHG) reductions, net power generation, and initial capital cost. Along with determining an operationally sound and cost-effective treatment facility, processes were also examined to meet the goals of generating Class A biosolids, maximizing energy recovery, and utilizing technology that shows promise for reducing PFAS contained in residuals. The technologies investigated under this framework include: Pre-digestion - Gravity Thickening of Primary Sludge - Mechanical Thickening of WAS - Thermal Hydrolysis - Thermal-Alkaline Hydrolysis Digestion - Single Stage Mesophilic Digestion Post Digestion - Dewatering - Thermal Drying Biogas Utilization - Digester heating via boilers - Existing Combined Cycle Turbine CHP - New Combine Heat and Power Engine - Renewable Natural Gas -On-site and 3rd Party - Thermal Drying Biochar Processes - Pyrolysis - Gasification Leading technology manufacturers were consulted to develop 3rd party proposals for Biochar Processes. The proposals included the technology provider and a solids management contractor that would serve as O&M staff and manage all residuals. Two different project delivery methods were considered for biochar technology - turnkey contracting and city finance. Under turnkey contracting, the 3rd party would finance and construct the facility, operate, maintain, and charge Toledo a tipping fee for cake delivered. For the city finance option, the City would pay to build the facility and engage in a long-term O&M and residuals management contract with the 3rd party entity. Results The quantitative results (Table 1) from the energy flow modeling were used as a guide to provide recommendations to the stakeholders, some of which are described below. - Reusing digester biogas for generating renewable natural gas results (RNG) in the increased monetary value of the gas. Current solids loading would generate about $1,700,000 gross RIN revenue annually. Adding the RNG system alone to the existing facility did not meet the project goals since there was no final solids volume reduction. - Addition of a pre-digestion hydrolysis process for WAS changed the overall outlook from a solids volume and energy endeavor. Hydrolysis allowed additional solids to be digested, greater biogas generation and increased the dewaterability of sludge. This alternative reduces GHG emissions more than others while reducing dewatered solids by 33% compared to the baseline. This alternative retain the same solids management program, optimizing the cost and sustainability of the existing solids facility; however, does not create a Class A product or destroy PFAS. - Adding a thermal dryer to the digestion system with enhanced WAS lysis system is recommended to create Class A granules eliminating the export of Class B biosolids. It was still financially advantageous to send biogas to RNG and fuel the dryer with NG. This scenario reduces the amount of solids transported out of the facility by 78% but increases the annualized cost of solids management while increasing GHG emissions. - For mitigation against future PFAS regulations as an end goal, a 3rd Party turnkey solution with either pyrolysis or gasification would need to be considered as the only viable option. Pyrolysis systems appeared to have better financials but did not include as much redundancy as the Gasification system proposed. The syngas produced helped the energy balance of these processes, but both were net energy consumers, driving increased GHG emissions. The turnkey project delivery would reduce the capital spent over the baseline scenario by about $100 million by digesters and eliminating cake storage. The case study findings provided a need to stay flexible while investing capital in upgrading the biosolids facilities. While federal regulatory action is not imminent, using a phased project delivery approach for the solid's upgrade project will be prudent while re-investing in digestion. The initial phase would include the installation of a single WAS-lysis treatment train as a large-scale pilot treating ~50% of the WAS load. Biogas will be utilized to produce RNG, thus increasing the value of the energy resources. Adding a thermal dryer or biochar processes will increase the solids handling systems' cost, complexity, and GHG emissions. These options need to be planned for both budgeting and space allocation, but should be phased for implementation when there is evidence that the market for land-applied cake is reduced or eliminated due to regulatory concerns.

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

SpeakerKikale, Pranoti

Presentation time

11:15:00

11:45:00

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

TopicBiosolids Management Planning, Decision Making, Holistic Design

Author(s)

Kikale, Pranoti

Author(s)P. Kikale1, E. Auerbach1, A. McClure2

Author affiliation(s)Arcadis U.S., Inc. 1; Arcadis U.S., Inc.1; City of Toledo 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2024

DOI10.2175/193864718825159438

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count19

Description: Designing Cogeneration Engines to Maximize Energy Efficiency: Focusing on Heat...

Designing Cogeneration Engines to Maximize Energy Efficiency: Focusing on Heat Recovery

Abstract

Biogas fueled combined heat and power (CHP) has been a cornerstone of resource recovery and renewable energy generation at wastewater plants for over 50 years. However, In the past decade, however, making the case for new CHP projects within the US has become increasingly difficult due to historically low energy prices and a scarcity of O&M labor. CHP remains in the interest of many utilities as an excellent way to achieve sustainability goals, but thoughtful and creative designs are needed to make projects work economically. By focusing on heat recovery aspects of CHP, a project to utilize biogas can also serve as an opportunity for a fundamental heating system upgrade at a WRRF while also providing positive economics. This paper provides insight into CHP design strategies that can be used to drive projects forward in a financially viable way, with a focus on the heat recovery portion instead of the more typical focus on electric power generation. Waste heat recovery is often an afterthought in most cogeneration discussions, but in reality it can be the tipping point for positive economics. It also is one of the most site specific and engineering intensive aspects of CHP design. Understanding the types, quality, and amount of waste heat to be generated and matching these sources to existing plant heat demands, hot water loops, boiler feeds, condensate return systems, and controls is a crucial part of the design process. The supporting case study for this paper is a recent CHP design by the Columbus Division of Sewerage and Drainage (DOSD) in Columbus, Ohio. DOSD is currently installing two 1.4 MW reciprocating CHP engines at its Jackson Pike WWTP which treats an average influent flow of 68 MGD. The plant's existing heating systems use steam for heating the water loops that ultimately heat their digesters as well as for space heating for buildings (Figure 1). There are three sets of boilers installed in different locations at the plant, all installed under different contracts and in different eras. This resulted in various steam and condensate systems that are not highly integrated and require the plant staff to operate multiple heating systems at once. The desire to implement CHP was driven largely by city wide sustainability goals, but DOSD staff also recognized the opportunity that a CHP project presented to unify and optimize their core heating systems. Arcadis was engaged to design the CHP system while focusing on developing heat recovery solutions that integrated into the existing plant systems, optimized energy recovery, and offset future capital projects by upgrading heating infrastructure. The design included the following elements: - Jacket water heat exchangers to deliver medium-grade heat to existing digester heating water loops. - Reduction of flow and temperatures of existing digester heating loops to maximize heat transfer from CHP. - Heat Recovery Steam Generators (HRSGs) to recover high-grade exhaust heat and produce steam for space heating. - Repurposing oversized digester heating boilers to service the entire plant steam system as a backup to CHP. - New cross-connection between two existing steam headers to unify systems. -Reconfiguration of condensate returns and centralization of deaeration equipment. - Retirement of aging building heating boilers while eliminating a capital project to replace them. The amount of CHP engine heat rejected into the jacket water loop was sufficient to heat the digesters even in the most demanding winter scenario (Table 1). However, in order to maintain the similar hot water supply temperatures into the sludge heat exchangers, a flow reduction in the primary hot water supply circuit was required. The plant staff experimented during the colder months of 2019/2020, changing pumps speeds and hot water circulation rates in their supply loop while monitoring digester temperatures. It was found that the primary hot water supply flow could be reduced by 25% while maintaining hot water supply temperatures at each sludge heat exchanger. The new reduced flow operation allowed a greater temperature rise across CHP heat exchangers and ultimately more effective heat recovery while also reducing pumping energy. Existing steam to hot water converters in the digester heating loop will also be maintained for backup when the CHP system is offline. HRSGs installed on the engine exhaust will be used to provide additional heat recovery and inject steam into existing building heating systems. These HRSGs needed to fit into an abandoned venturi scrubber building (Figure 2) which was being repurposed to house the new CHP system and eliminate the need for constructing new buildings or containers. An additional layer of complexity for this site is that Jackson Pike WWTP is a site with historically significant and preserved building architecture, so any building modifications needed to minimal and/or in line with historical standards. The HRSGs were designed in a vertical configuration to make better use of the tall but narrow building orientation. Existing building mezzanine grating, preserved to the largest extent possible, provide access to the exhaust system components reaching upwards towards the building roof. Figures 3 and 4 illustrate the final exhaust piping design work that delivered an intricate layout solution in the existing space while adhering to all back-pressure, acoustical, and accessibility constraints. Analysis of existing digester boiler capacity and actual digester heating loads revealed that the digester boiler system was oversized by approximately 5X. In contrast, the existing building space heating boilers were being operated a maximum capacity every winter with no redundancy at all. These boilers were also of 1970s vintage and in need of replacement with a capital project. A new steam cross connection was designed between the digester heating boilers with excess capacity and the aging and overtaxed building heating boilers. This will allow the building heating boilers to be retired without replacement, eliminating the need for a boiler replacement capital project which was counted as a capital credit to the cogeneration project economics. The existing digester heating boilers will now serve as a single backup system to heat the entire plant when the CHP engines are offline. A key finding during design was that unifying heating systems did not require large amount of capital spending, but it did require a large amount of engineering effort and brainpower. This is perhaps best exemplified in the condensate collection and return systems that needed to be reconfigured and reconceived. Currently, three different condensate return systems are dispersed throughout the plant and only return water to their dedicated boilers. Under the CHP project, all condensate returns will be rerouted to a centralized deaerator which will be equipped with sophisticated boiler feedwater pumping controls that deliver the feedwater to the various boiler systems as needed including the HRSGs installed with CHP (Figure 5). Table 2 shows the economic analysis of the CHP project with the above mentioned advanced heat recovery design approaches incorporated. The economic benefits from maximizing the amount of useable heat were significant. The CHP system could heat the entire digester systems while also providing 61% of the building heating in winter (on top of generating ~3MW in green power). This led to a minimized about of natural gas consumption needed to heat the balance of the plant and significantly brought down O&M spending. Also, by avoiding a capital project to replace existing building boilers, a capital credit was applied to the CHP project which played a considerable role in the financial success of the project. These heat recovery benefits served as the tipping point for the CHP project become financially viable while also providing a pathway for the plant to upgrade its core heating infrastructure. The bidding was executed in December 2020 with construction award expected in early 2021. By using heat recovery to help make CHP viable, DOSD and the City of Columbus now have a financially and operationally sensible project to make significant achievements towards city wide GHG reduction goals.

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

SpeakerAuerbach, Eric

Presentation time

8:30:00

9:00:00

Session time

8:30:00

11:15:00

Session number18

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicCogeneration, Energy recovery, Heat recovery

Author(s)

E. Auerbach

Author(s)S. Allen1; E. Auerbach2; M. Costa Tomazelli3; B. Fox4

Author affiliation(s)Residuals and Biosolids Speaker; 1Residuals and Biosolids Speaker; 2Residuals and Biosolids Speaker; 3City of Columbus Department of Public Utilities; 4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May, 2022

DOI10.2175/193864718825158376

Volume / Issue

Content sourceResiduals and Biosolids

Word count12

Full Scale Pilot of a Novel Struvite Precipitation System at the Provo WRP

Abstract

INTRODUCTION The Provo Water Reclamation Plant (WRP) which treats approximately 15 MGD of influent is currently undertaking a major plant upgrade to address effluent phosphorus levels. This upgrade includes a mainstream liquid process shift to enhanced biological phosphorus (P) removal (EBPR). This upgrade also has implications for the solids stream as historically the plant has struggled with nuisance struvite formation in its dewatering centrate downstream of its anaerobic digesters. The introduction of EBPR is expected to exacerbate the struvite issues by increasing the ortho-P concentrations in digested sludge from the currently levels of 60-70 mg/L to levels approaching 200-250 mg/L. This struvite issue combined with the need to limit recycle P loads to meet effluents limits created a glaring need for a sidestream struvite mitigation system. This plant upgrade also brought financial stress on the utility as the mandated effluent quality improvements carried a hefty capital price tag. As a result, the Provo WRP was keenly interested in finding ways to solve their struvite problems while limiting the impact to their capital budget. As the solids stream lead for the plant upgrade engineering team, Arcadis was tasked with identifying and evaluating advanced and novel sidestream P solutions that could address the full suite of operational and financial drivers. TECHNOLOGY SELECTION The technology selection included a competitive, performance based solicitation that considered a wide range of factors including P removal performance, capital cost, chemical addition, footprint requirements, and system O&M requirements. The resulting selected technology from this solicitation was a novel struvite precipitation process developed in Germany by Eliquo and dubbed the 'EloVac' process. This process is similar to other well-known struvite precipitation processes in that it aims to strategically raise sludge pH in a dedicated reactor, thereby increasing the solubility levels of struvite and creating struvite crystals that can be recovered or incorporated into the biosolids. The novel concept behind the EloVac technology is method by which the pH of the sludge is raised. While better known technologies utilize air stripping with blowers and diffusers and very tall reactors, the EloVac system utilizes a vacuum pump to raise sludge pH. This methods allows struvite precipitation to occur in a reactor that is the fraction of the size of traditional struvite precipitation technologies, requiring a residence time of only 10 minutes. It also eliminates the tall tank height and blower requirements involved with more traditional air stripping systems. The vacuum based EloVac is a compact system that can fit entirely on a 20'x10' prefabricated skid and has significantly reduced installation costs and footprint requirements. The main concern regarding this selection was the nascent nature of the technology, with only one other operating system in the world located in Lingen, Germany where it was developed. After technical due diligence the engineering team and the Provo WRP staff elected to move forward with a pilot system based on the cost and footprint benefits provided. While developed in Germany, the system is distributed in the US by Ovivo with its headquarters is located within the Salt Lake City area adjacent to Provo. Ovivo has had a successful history piloting its (then novel) linear motion mixer at the Provo WRP. To mitigate new technology risk, Ovivo and Provo negotiated an agreement to produce a full scale pilot capable of treating the entire plant sludge flow. The system is furnished under a 3 year lease agreement contingent on successful performance of the equipment during pilot testing, with Provo afforded the option to buy the equipment after the lease period. PILOT SYSTEM The containerized pilot system was installed at the plant site and started up in April 2021. The piloting was a collaborative effort between the engineering team (Arcadis), the equipment supplier (Ovivo), and the Provo WRP staff who performed the sample collection and laboratory analyses. The EloVac unit draws sludge from the plant's East Secondary Digester and returns struvite precipitated sludge to the West Secondary digester where it is then fed to dewatering. The major sampling points parameters measure are summarized in Table 1. RESULTS After an initial 10 day start-up period, the data collected for reactor performance showed immediate effectiveness for reducing sludge and centrate ortho-P concentrations below the target of 25 mg/L (as shown in Figure 1). This was not the entire picture, however, as Provo staff had initially kept dosing ferric to the centrate as a precaution during the pilot system start-up. This ferric dosing was discontinued in May (see Figure 2) which led to a build-up of struvite on the centrate pumps. This struvite formation was confounding as the ortho-P levels in the centrate remained low. After additional field investigations and analysis, it was determined that struvite was forming due to a combination of elevated pH levels occurring between the reactor effluent and centrate as well as overdosing of Mg. This combination of factors was driving the solubility product constant (Ksp) towards precipitation of struvite in the downstream centrate and not as crystals in the reactor as intended. Struvite precipitation on internal reactor piping was also observed during maintenance. Mitigating actions were taken including reducing the target Mg feed rate to the reactor as well as increasing the reactor level and vacuum pressure to drive more precipitation in the reactor and not the centrate. These adjustments appeared to be effective as the Provo staff were able to gradually reduce precautionary ferric dosing to the centrate and no new struvite formation was observed. CONCLUSIONS The based on full scale pilot testing results, the EloVac system was deemed to be effective in precipitation of struvite from the digested sludge. Throughout the pilot testing the effluent and centrate ortho-P concentrations remained at or below the target concentration of 25 mg/L. In September 2021 Provo staff reported that they had curtailed the precautionary ferric dosing to zero and that nuisance struvite had not been observed. This indicated that the system is working as intended to both prevent nuisance struvite and to prevent recycle of ortho-P back to the liquid stream. Provo WRP operators also noted that there have been observable benefits to dewatering performance in the form of higher cake solids and lower polymer dose. Currently the precipitated struvite crystals exit the plant via the biosolids but there are future plans to implement P recovery. Provo has accepted the equipment and is exploring options to permanently install it inside a building once the 3-year lease is completed. From a technology standpoint, this is an instance where a utility and engineering team took a chance to try something new. Backed by significant due diligence and a dedicated technology provider in Ovivo this willingness to test a novel technology resulted in considerable capital and operational savings. With these testing results in hand, sludge struvite management at this scale may be due for a paradigm shift as other plants of similar size can consider the EloVac technology when addressing their struvite issues.

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

SpeakerAuerbach, Eric

Presentation time

14:30:00

15:00:00

Session time

13:30:00

16:45:00

Session number14

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicPhosphorus Removal and Recovery, Pilot Scale, Struvite

Author(s)

E. Auerbach

Author(s)E. Auerbach1; M. Kessler2; S. Turnbow3; M. Gangal4; J. Goldhardt5

Author affiliation(s)Residuals and Biosolids Speaker; 1City of Provo Utilities; 2Provo City; 3SUEZ - Water Technologies & Solutions; 4Coombs Hopkins; 5

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158433

Volume / Issue

Content sourceResiduals and Biosolids

Word count14

Description: Sludge Conditioning, High Strength Waste, and Renewable Natural Gas at the Capital...

Sludge Conditioning, High Strength Waste, and Renewable Natural Gas at the Capital Region Water AWTF

Abstract

WEFTEC, the largest water event of its kind in North America, offers water quality professionals the best in water quality education and training. With almost 200 technical sessions, workshops, mobile sessions, local facility tours and 1,000+ exhibitors, it is the premier water conference! The WEFTEC technical program is selected through a rigorous, peer-review process, ensuring that attendees experience the highest-quality education. WEFTEC speakers are experts and innovators, leading the way in water quality. The following paper was presented at WEFTEC 2020.

SpeakerAuerbach, Eric

Presentation time

12:00:00

12:30:00

Session time

11:00:00

12:00:00

SessionPredicting, Increasing and Conditioning Biogas

Session number8B

TopicBiosolids and Residuals, Facility Operations and Maintenance

Author(s)

E. AuerbachE. AuerbachJ. RosentelT. Johnston

Author(s)E. Auerbach1; E. Auerbach1; J. Rosentel2; T. Johnston3;

Author affiliation(s)Arcadis, NY1; City of Harrisburg, PA2; Material Matters Inc, PA3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2020

DOI10.2175/193864718825157588

Volume / Issue

Content sourceWEFTEC

Word count16

Sludge Conditioning and Renewable Natural Gas at the Capital Region Water AWTF

Abstract

On the heels of a major BNR upgrade completed in 2016, Capital Region Water (CRW) in Harrisburg, PA set out on making significant improvements to its solids and energy streams. CRW operates a 22 MGD Advanced Wastewater Treatment Facility (AWTF) with a pair of mesophilic digesters dating back to last major plant expansion in the 1970s. These digesters are currently undergoing refurbishment including grit removal, new covers, and mixing. With BNR and fresh digesters in place, CRW is now setting its sights on sustainability goals by targeting a project to enhance energy recovery from its solids resources. To help identify the most beneficial energy recovery project, CRW engaged with an engineering team led by Arcadis in 2018 to undertake a comprehensive solids and energy planning effort targeting upgrades. The CRW plant already had an operational history of recovering its biogas for energy using CHP engines. The plant has been operating a set of 600 kW Waukesha 'Enginators' since 1984 to make electricity and recover hot water for heating (see Figure 1). Interestingly, CRW does not utilize the CHP electricity internally, but instead transmits its generated power to the local utility and receives full delivered unit pricing via an interconnection agreement. These engines are reaching the end of their useful lives, however, and the CRW staff initially envisioned an in-kind replacement of the CHP engines with upgrades to heat recovery. The solids and energy planning effort was aimed at looking at a wide range of options both in conjunction with and in lieu of CHP. For example, the plant currently co-thickens primary sludge and WAS in gravity thickeners, leading to significant seasonal deterioration in thickening performance (see Figure 2) especially after the implementation of BNR. One of the improvements examined was the separation of WAS for mechanical thickening to improve sludge feed concentrations to the digesters. This, along with the following list enhancement items were examined: Separated mechanical WAS thickening WAS lysis for enhanced digestion New CHP engines with upgraded heat recovery Biogas to Renewable Natural Gas (RNG) Acceptance of High Strength Waste (HSW) Backup power generation with CHP Upgrades to biogas compression and transmission The key tool used to evaluate all these options and their interacting effects was holistic solids and energy flow model (see Figure 3). With this tool, any potential combination of processes or loading rates was quantitatively analyzed for annualized cost, greenhouse gas (GHG) reductions, net power generation, and capital cost. Along with determining an operationally sound and cost-effective treatment facility, processes were also examined to meet goals of maximizing value of the plant's energy resources and supporting the cost effective Class B biosolids land application program already in place. There were some very significant site specific factors identified early in the planning process. One item was the existence of a natural gas 'peaker' facility directly adjacent to the AWTF fence line in the area of the digesters. This facility is operated by the local natural gas utility. Engagement with this utility revealed a positive and cooperative position regarding connection of RNG to their system. This meant that CRW had not only identified a partner for RNG, but also would have an interconnection pipeline requirement of essentially zero. Another site specific item for this project was the abundance of high quality HSW in the area due to the presence of local food producers such as Hershey Creamery and Utz Potato Chips. These producers have previously shown high interest bringing their material to the AWTF, making the acceptance of HSW a high priority for CRW. With these site specific conditions in mind, Figure/Table 5 give the results of some of the most prominent scenarios from solid and energy flow model tool. One of the major conflicts facing this facility and many others is the illogical incentive structure under the current Renewable Fuel Standard (RFS) where digesters receiving HSW get penalized as RINs are downgraded from D3 to D5. This was confounded by the acute drop in D3 RIN pricing occurring in late 2019 during the time of the study. Significant sensitivity analysis on both D3 and D5 RIN pricing was done using the flow model tool, allowing many potential future RIN pricing scenarios to be considered. Ultimately, the decision to target both RNG and HSW acceptance was made. While accepting HSW reduced RIN value potential, it also brings in tipping fees and avoids the higher sensitivity swings related to D3 RIN prices. Some other conclusions were as follows: The replacement of CHP engines with new equipment and upgraded heat recovery did not provide an annualized savings to the plant. This included maintaining the existing interconnection agreement at $0.075/kWh and taking a capital credit for offsetting backup power generation. The main driver was the high cost of biogas conditioning and the O&M support package which is difficult to overcome for newer engines at this scale. The addition of enhanced sludge thickening by separately mechanically thickening WAS did not provide annualized savings to the plant. However, this was viewed as a fundamental investment in solids infrastructure, providing operators more control over thickening and eliminating the difficulties with seasonal bulking and performance deterioration in the gravity thickeners. Savings from other parts of the project would offset this long term investment in improved operations. The addition of WAS lysis beneficial on an annualized costs basis, paying for its capital by increasing biogas recovered as RNG and reducing biosolids to be managed. Implementation of lysis was selected, with major driver being current dewatering difficulties. Currently the AWTF must produce 20% TS cake as part of their land application which has been a struggle. With lysis, a cake TS increase of 2-3% is expected which would significantly improve dewatering operations for land application. Based on the results of this work, CRW has moved forward with implementation of the recommended project with the design completed and construction slated to begin in early 2021. The project includes a new Thickening and Lysis Building to house new WAS thickeners as well as thermal-alkaline WAS lysis. Heated and lyzed WAS will be blended in-line with received HSW in a new feed line to the digesters. A new biogas to RNG skid will be implemented with the neighboring natural gas peaker facility taking custodial transfer of the product gas for injection into the pipeline. The engineering team has also recently identified a local PA 'green gas' program in the Philadelphia area willing to pay premium prices for RNG. Partnering with this type of offtake can remove headaches related to the RFS by avoiding swings in RIN market prices and value conflicts around accepting HSW. By partnering with local food producers and natural gas utility, this project serves as model for how cooperation and regionalization can significantly uptick the value that can be obtained for energy resources at a WRRF. This also demonstrates the value of effective solids and energy planning as CRW staff were able to quickly and confidently move forward with implementation, and take on long term operational improvements such as thickening in combination with money savings aspects like HSW and RNG.

The following conference paper was presented at Residuals and Biosolids 2021: A Virtual Event, May 11-13, 2021.

SpeakerAuerbach, Eric

Presentation time

13:50:00

14:10:00

Session time

13:30:00

14:30:00

SessionSustainability: Planning, Action, and Communication

Session number7

Session locationLive on Zoom

TopicBiogas Energy, Renewable Natural Gas, thermo-chemical hydrolysis

Author(s)

E. AuerbachJ. Rosentel

Author(s)E. Auerbach1; J. Rosentel2

Author affiliation(s)Arcadis 1; City of Harrisburg 2;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2021

DOI10.2175/193864718825157959

Volume / Issue

Content sourceResiduals and Biosolids Conference

Word count13

Description: The Road to Resource Recovery - Equipment Procurement, Natural Gas Utility...

The Road to Resource Recovery - Equipment Procurement, Natural Gas Utility Negotiations, D3 RINs, and IRA Credits for an Enhanced Energy Recovery Project

Abstract

Introduction Capital Region Water (CRW) in Harrisburg, PA is embarking on a project to convert its 22 MGD Advanced Wastewater Treatment Facility (AWTF) to a true resource recovery facility through an Enhanced Energy Recovery Project. This project takes a multifaceted approach to maximize the biosolids energy extracted and beneficially utilized including the following: - Thickening upgrades to enhance percent Total Solids (%TS) in digester feed - Hydrolysis of Waste Activated Sludge (WAS) using a Thermal-Alkaline process - Importing local High Strength Waste (HSW) and blending into digester feed - Implementing Renewable Natural Gas (RNG) and interconnecting with an existing Natural Gas (NG) utility gas injection station adjacent to the plant This project is a culmination of a long-term planning, design, and implementation program that took a holistic view of the facility to devise a comprehensive resource recovery strategy. This strategy allowed CRW to invest in fundamental solids infrastructure (thickening) as well as embrace new technology (Thermal-Alkaline Hydrolysis) all while providing significant financial returns and sustainability benefits. Biogas production is expected to double and be 100% utilized as renewable fuel. Revenue from monetizing RINs and tipping fees from HSW will more than offset the cost of the project (including annual debt service on capital) with net revenue from the project expected to exceed $1 million/year. As this program developed from planning in 2018 to currently ongoing construction, there were a variety of changes in the resource recovery landscape that needed to be accounted for. These included: - Rising value of D3 and especially D5 RINs and emergence of voluntary markets - Material and labor shortages and resulting inflation due covid and global conflict - Passing of the Inflation Reduction Act (IRA) - RFS update to amend rules governing D3/D5 splits for co-digestion These developments led to a variety of new challenges and benefits that shaped how CRW and its engineering partners went about executing their vision for enhanced energy recovery. This paper details the various endeavors undertaken to keep up with the fast paced change as the project moved from planning to implementation. Procurement of Lysis A specialized Thermal-Alkaline Hydrolysis (Lysis) process was selected to enhance digestibility of sludge while increasing digester solids feed concentrations and lowering viscosity. The Lysis process was procured under a separate equipment procurement contract with the supplier, which will then be assigned to an installing contractor. This had a number of benefits including: allowing the design of WAS thickening and Lysis as one unified process, accelerating the delivery of long lead time equipment, and locking in pricing to mitigate against rising inflation. As provisions and timelines for the IRA came to light, early procurement of this equipment also became a tool when seeking to officially start construction before 2024. Negotiations with Natural Gas Utility There is a natural gas peaker facility located directly adjacent to the CRW plant. This facility stores pressurized natural gas and injects it into the grid on very cold days to augment local gas pipeline supply. The entity operating this facility is an unregulated energy services division of the local distribution company which means that they not only can provide access into the pipeline but could also serve as the buyer and monetizer of RINs. This was advantageous as it allowed negotiations and contracting with one single entity for both pipeline connection/injection terms, as well as gas and attribute sales. It also created natural incentives for cooperation and streamlining interconnection terms, as the energy services entity would also be losing profit if the interconnection was shut in. In this spirit of cooperation, there was a single gas monitoring station owned and maintained by the energy service entity but located on the CRW plant site with foundations and utilities provided by CRW. For the jurisdictional gas piping connection from the RNG skid to the interconnection station, the CRW installing contractor is responsible for the earthwork while the energy services entity will deploy its own expert staff to install and certify the pipe. Retaining D3 RINs with Co-digestion Acceptance of HSW was identified during planning due to local food producers such as Hershey Creamery and Utz Potato Chips creating an abundance of high-quality digester feedstock. Original plans included blending this HSW with feed sludge and accepting a lower value D5 RIN as the financial basis of the project. CRW wanted to maximize sustainability benefits of the project while also providing a local outlet for organic recycling and were willing to sacrifice D3 RIN revenue for these goals. During design, steps were taken to segregate HSW and inject it separately into a single digester to retain D3 RINs in one of two plant digesters. This added cost and complexity to the project and limited digester capacity to accept HSW. In June 2023, the EPA released updates to the RFS which amended rules around co-digestion and created pathways to retain D3 RINs in a digester that was receiving a mix of sludge and HSW. Due to this change the design was altered to return to a single, blended digester feed. This not only reduced project cost and complexity, but also assisted in digester feed hydraulics. The heated and lyzed sludge from WAS Lysis is blended in-line with HSW directly at the receiving tank for use as a pumpability enhancing transport medium. Provisions for the new co-digestion rules under the RFS included the requirement to establish a baseline of biogas production with just sludge to set D3 RIN benchmarks, with biogas production above these benchmarks being counted as D5. This lead to a significant baseline data analysis effort as well as staging of the project to get the WAS Lysis system up and running prior to injecting HSW so that the D3 baseline benchmark for the plant can include Lysis benefits. IRA Credits and Timelines The passing of IRA legislation in 2022 created a groundswell of activity in the field of resource recovery from biogas, with a number of credits (including Investment Credit 48 - Energy Property) providing the potential for tremendous capital cost offset in the form of direct pay tax credits. The IRA also brings with it a slew of requirements and timelines to be satisfied, with the timelines of needing construction to start before 2025 being particular challenging to municipal entities. The engineering team engaged with tax professionals with expertise in IRA provisions to develop an effective strategy for the CRW Energy Recovery Project. One insight gleaned from working with these experts was that a credit application does not need to be confined to a single project or single contract. The strategy included establishing a fact pattern to demonstrate ongoing improvements to the overall energy system which encompasses the feedstock collection and processing, the primary digesters, and the biogas collection and utilization. Based on this view, Primary Digester rehab work conducted between 2018 and 2022 were included as part of continuous improvement effort on this system and was considered in the credit application along with the Energy Recovery Project. This yielded a variety of benefits including establishing the start of construction well before the 2025 timeline while also granting safe harbor from onerous IRA requirements that escalate with time such as domestic content provisions. Conclusion This project demonstrates the dynamic nature of the resource recovery landscape and the various activities required to keep a vision up to speed with real world implementation. The engineering role in these endeavors is no longer to simply produce plans and specifications. A true partner involves skills ranging from crafting agreements with gas companies to interpreting federal legislation, all while continuously evolving approaches to keep up with changing external factors. Currently CRW has executed the procurement contract for Thermal-Alkaline Hydrolysis, executed the interconnection and gas sales agreements, and have awarded the construction contract for the Enhanced Energy Recovery Project. From planning to implementation the original vision has persisted despite unprecedented inflation (approximately doubling capital cost over projections). By taking advantage recent changes in credit markets and legislation, the project financial outlook actually improved with a projected annual net savings to CRW in excess of $1 million (including debt service on capital). The project will also double the plant biogas production while providing a beneficial outlet for 100% of gas produced, reducing the GHG footprint by ~7,200 Metric Tons of CO2/year.

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

SpeakerAuerbach, Eric

Presentation time

10:45:00

11:15:00

Session time

08:30:00

11:15:00

SessionCase Studies & Lessons Learned

Session number27

Session locationOklahoma City Convention Center, Oklahoma City, Oklahoma

TopicHigh Stength Waste, Renewable Natural Gas, thermo-chemical hydrolysis