Laub, Margaret

Margaret Laub is reponsible for business and project development for Anaergia, with a focus on anaerobic digestion of organic waste and biogas utilization. Margaret is a Certified Energy Manager and holds a degree in Environmental Engineering from Harvard.

Titles from this speaker

Description: Alternate: Greenfield Wastewater Resource Recovery Facility in Southern California...

Alternate: Greenfield Wastewater Resource Recovery Facility in Southern California Leverages State of the Art Technology to Deliver Complete Resource Recovery & Community Resilience

Abstract

Overview: Formed in 1954, East Valley Water District (EVWD) provides water and wastewater services for a population of more than 100,000 across 18,000 acres in the City of Highland and portions of the City and County of San Bernardino County, CA. EVWD initiated greenfield development of the Sterling Natural Resource Center (SNRC) to provide water recycling for groundwater recharge and enhance their core mission of water production. SNRC enables EVWD to provide in-house wastewater services to ratepayers, rather than relying on neighboring agencies. SNRC was envisioned with the ultimate goal to provide community resilience through utility reliability, resource recovery, economic development, and educational partnerships. SNRC takes a holistic approach to waste recovery, providing water recycling to replenish the Bunker Hill groundwater basin, leveraging biogas from anaerobic digestion to support plant energy needs, and converting solids to Class A soil amendment. The 2.2-acre eastern portion of SNRC houses state-of-the-art process equipment, and the western lot was developed to feature a new District headquarters, community center, and public green space. EVWD partners with community organizations to host events and activities, including educational and vocational initiatives. Following October 2018 groundbreaking, construction was completed in early 2022, and commissioning is ongoing. Operations are to begin in early 2023. EVWD worked closely with stakeholders to maintain construction progress through the pandemic. Approach to Resource Recovery: The greenfield 8 MGD wastewater resource recovery facility (WRRF) is designed to provide complete resource recovery, beyond the scope of traditional wastewater treatment. Ultimately, all wastewater entering the plant is turned into beneficial products supporting facility operations and the broader community. -Wastewater: SNRC treats up to 8 MGD wastewater, using a Fibracast membrane bioreactor (MBR) with FibrePlate membranes. Recycled water is injected underground to replenish the Bunker Hill Groundwater Basin, which serves as water supply for EVWD and neighboring communities, and improve drought-resistance. -Biosolids: Solids remaining after anaerobic digestion (AD) via Anaergia's OmnivoreTM high-solids digestion technology are transported to the nearby Anaergia Rialto Bioenergy Facility (RBF) (approximately 10 miles away) for thermal processing via pyrolysis to carbon- and nutrient-rich Class A soil amendment for agricultural use in Southern California. Nutrients: Sidestream treatment is provided by Anaergia's AMR system to recover nitrogen for use in commercial fertilizer (as discussed further below) and recycle nutrients back to regional agriculture. - Energy: Biogas produced from anaerobic digestion fuels 3MW of combined heat and power (CHP) systems to create renewable energy to meet plant power and thermal demands. In addition to self-sufficiency, this improves reliability of operations and reduces operating costs and therefore burden on ratepayers. -High-strength waste (HSW): SNRC receives up to 130,000 gallons per day of landfill-diverted HSW for co-digestion with wastewater biosolids. This supports methane emissions reductions from landfill, compliance with state organics recycling mandates, and enhances biogas production to support SNRC energy-neutrality. Tip fees collected offset operating costs at SNRC and support rate stabilization. Key Technologies: SNRC employs leading edge technologies from Anaergia and Fibracast to achieve resilient, self-sufficient operations with minimal residuals. -Fibracast MBR: Water is recycled using a MBR with FibrePlate membranes so that it may be used for groundwater recharge. These proprietary membranes combine the best advantages of hollow-fiber and flat sheet MBR systems, using aeration and mixed liquor cross filtration to continuously clean the membranes during operation. The membrane's high packing density, low trans-membrane pressure, and advanced automation leads to easy and reliable plant operations. -Anaergia Omnivore high-solids digestion: Omnivore was employed to cost-effectively provide the digester capacity required to process wastewater biosolids and HSW and generate biogas for energy neutrality. Omnivore uses Anaergia proprietary OmniMix high-solids mixing system together with robust thickening technology to increase the solids ratio in digesters, allowing for triple the feed capacity of a traditional digester, reduced footprint, and reduced and capital expense. This was particularly important at SNRC given space constraints. Anaergia screw presses are employed to pre-thicken digester feeds, which also reduces heat demand associated with heating excess liquid within the digester. Anaergia OmniMix mixers ensure the thickened digestate, including high-solids HSW, is adequately mixed to support tank turnover, digester health, and VSR. OmniMix mixers provide improved energy efficiency versus traditional mixing systems. Overall, Omnivore provides SNRC with reduced energy demand while supporting increased biogas production, advancing achievement of energy-neutrality. -Anaergia AMR sidestream treatment: After digestion, digestate is dewatered via Anaergia screw presses to 25% TS. The filtrate is processes via Anaergia AMR to recover up to 90% of nitrogen as ammonia, creating ammonium sulfate (AMS) fertilizer. AMR operations use heat generated via biogas CHP. Following sidestream treatment, filtrate is also treated via MBR for groundwater recharge. Strategic Partnerships: SNRC was conceived of primarily as a community resource beyond essential water and wastewater services. SNRC supports community and economic development by providing valuable resources for residents and strategic partnerships. -Workforce Development: SNRC resulted in creation of numerous permanent, full-time Greentech jobs within the District service area. Leveraging the new public spaces built as part of the project, EVWD intends to host community events, including educational events focused on SNRC capabilities to enhance engagement and sense of ownership. As SNRC is located across the street from Indian Springs High School, EVWD has launched a Water and Resource Recovery Career Pathway in partnership with San Bernardino City Unified School District. This program offers courses that highlight opportunities in the resource recovery sector and facilitate industry leaders sharing technical and personal stories to community members at no cost. A similar program has been established with San Bernardino Valley College. SNRC also house the Water Education Learning Lab (WELL) Program to provide readily-accessible hands-on experiences and training. Rialto Bioenergy Facility: Dewatered biosolids generated at SNRC will be transported approximately 10 miles to Anaergia's RBF, where they will be dried and pyrolyzed. The resulting Class A product is carbon- and nutrient-rich, and free of PFAS and other contaminants of emerging concern (CECs) such as microplastics and pharmaceuticals. This process allows both nutrients and energy from biosolids to be recovered and beneficially reused. Further, this partnership provides EVWD with a reliable and environmentally friendly guaranteed biosolids management outlet, compliant with California SB1383 regulations, which limit landfill disposal of organics such as biosolids. By establishing agreements within the region, vehicle miles and emissions associated with biosolids hauling are also significantly reduced. Anaergia Nutrients: EVWD and Anaergia once again teamed to develop the Anaergia Nutrients facility at an underutilized District property, approximately two miles from SNRC. The facility will blend Class A soil amendment produced at RBF with AMS recovered at SNRC to create a marketable carbon-negative commercial fertilizer. The user-friendly material can be readily substituted for more costly conventional fertilizers. As a result, two resources often treated as residuals are instead converted to a valuable product helping to close the loop on nutrient recovery and create ancillary benefits and improve profitability for California farmers. EVWD and its ratepayers directly benefit from enhanced property use, lease payments, and host fees. Waste Generators & Haulers: SNRC provides a reliable alternative HSOW disposal option that meets state organics diversion requirements that is also good for business. Rather than travel to landfill, waste haulers reduce vehicle miles and emissions by disposing of waste at SNRC and reduced trip time translates to more business. The mutual benefits mean robust and consistent feedstock source to SNRC for onsite renewable energy generation. SNRC is the result of a visionary mission for EVWD. It provides the new model for stewardship of scarce public resources while enhancing quality of life and economic growth.

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

SpeakerLaub, Margaret

Presentation time

8:30:00

11:45:00

Session time

8:30:00

11:45:00

SessionSession 11: Circular Water Economy

Session number11

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicSustainability and Resource Recovery

Author(s)

M. Laub

Author(s)M. Laub1, 2, 3, 4,

Author affiliation(s)Anaergia1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158778

Volume / Issue

Content sourceResiduals and Biosolids

Word count24

Description: Case Study Highlighting the South San Francisco-San Bruno Water Quality Control...

Case Study Highlighting the South San Francisco-San Bruno Water Quality Control Plant's Initiatives to Increase Digestion Capacity within Existing Plant Infrastructure via High-Performance Mixing, Recuperative Thickening, and High Solids Digestion.

Abstract

l to both the solids retention time (SRT) and hydraulic retention time (HRT). Anaergia's two-part Omnivore AD platform triples capacity of existing digesters to maximize existing WRRF infrastructure and provide redundancy. Anaergia's sludge screw thickener (SST) (Fig. 1) recuperatively thickens digestate to decouple SRT from HRT, allowing digesters to operate at significantly higher solids content. By separating water from digestate, excess water is removed and returned to plant headworks for additional treatment and/or nutrient recovery, while thickened solids (typically 12% TS) are returned to the digester (Fig. 2). Digestate is therefore thickened up to three-fold (6-8% TS) thus tripling F:M ratio and enabling organic loading rates up to 0.33 lb-VS/ft3/day. By decoupling SRT from HRT, Omnivore ensures SRT well over 15 days required for regulatory compliance and stable digester operation. Mixing is an essential and often overlooked component of the AD process and has historically been limited to technologies that operate effectively at lower solids content. To ensure proper mixing in higher solids conditions, Omnivore employs Anaergia's robust low-speed and high-torque permanent synchronous magnet (PSM) mixers (Fig. 3). These high-efficiency propeller mixers are designed to effectively mix high viscosities that result from thickening digestate and resist ragging. Omnivore mixing achieves a high standard of mixing performance, over 90% of the digester volume continuously mixed above critical velocity (0.3 ft/s) ensuring maximum volatile solids destruction, biogas production, avoiding settling of grit, and homogeneity de-risking upset events such as rapid rise. The cost-effective retrofit has the ability to unlock additional digester capacity and increase redundancy while simultaneously improving digester performance. With the additional AD capacity created, WRRFs can rapidly accommodate increased internal sludge loads, high strength waste (HSW) for codigestion, and improve plant resiliency. Application: South San Francisco-San Bruno Water Quality Control Plant (WQCP) capital improvement planning identified a need for additional AD capacity and initially prescribed construction of a new AD facility. Design by Carollo Engineers incorporated Omnivore retrofits to the existing AD system to cost-effectively provide necessary capacity and avoid the need to build an additional digester. The retrofit also provides flexibility for future codigestion of HSW and increased biogas production. In late 2020, construction was completed to retrofit Digester 1 (0.83 MG) with the Anaergia Omnivore high-solids digestion (HSD) system. The technology package included one skid-mounted sludge screw thickener (SST) for recuperative thickening, three high-solids submersible PSM digester mixers, three mixer service boxes, and all ancillary equipment for a complete Omnivore system. Existing mixers were removed from Dig. 1 and replaced with new PSM mixers. Mixers were selected for low energy demand, low operation and maintenance cost, and efficient performance. Platforms installed provide access to Anaergia service boxes (Fig. 3), which enable in-situ mixer access without interrupting AD operations. Each mixer is mounted to a vertical post inside the digester allowing for height and attack angle adjustments to achieve optimal mixing, resuspend settled grit, and break scum accumulation in upper layers. The SST and accessory equipment were installed adjacent to Dig. 1, reducing pump energy, footprint, and impact on WQCP operations. Validating Omnivore HSD: Dig. 1 was brought online on January 5, 2021. Recuperative thickening was initiated in February and achieved steady performance in April (Fig. 4). Third-party performance testing was conducted in conjunction with Anaergia from April to July 2021. The below performance criteria were evaluated and achieved (Table 1): - Min. volatile solids reduction (VSR) above 57% for 80% of the time over 90-day test period, over a 30-day moving average (Fig. 5) - Demonstrate stable digester operation with volatile fatty acid (VFA)/alkalinity ratio <0.2 (Fig. 6) Testing further confirmed successful HSD in Dig. 1 as demonstrated by increased digester feed volumes, TS loading, and VSR, as well as steady OLR and VFA/alkalinity ratio. Note that design was developed to meet performance requirements and operational objectives requested by WQCP representatives and does not maximize use of Dig. 1 volume. Operation at higher solids would further increase digester capacity for future growth needs or codigestion. Mixer Performance Test: A third-party Lithium-ion Tracer test was conducted to confirm achievement of mixer performance requirements. The independent study (1) validated achievement of Anaergia's high-performance mixing standard (>90% of digester volume >0.3 ft/s) and (2) aligned with computational fluid dynamics (CFD) modeling of mixer performance, which indicated superior performance compared to alternate mixing technologies. Adequate mixing efficiencies were observed from the Tracer test washout curve (Fig. 7), which demonstrates low data scatter (high R2 value). Temperature profile indicated uniform temperature distribution within Dig. 1, with a 1-degree C maximum variance between maximum and minimum temperatures (Fig. 8). Total solids concentration was +/-10% of the mean value, indicating homogenous digester operation (Fig. 9). Tracer test findings are compatible with CFD analysis by Anaergia for the WQCP. The analysis modeled Dig. 1 and various mixer technologies present at the WQCP (Anaergia PSM, linear motion, and pump mix). The model was calibrated with published submittal sheet parameters for each mixer type and actual dimensions of Dig. 1. The model compared energy usage and mixing performance (as measured by percent of tank volume above critical velocity) for each technology at 2%TS and 6%TS. The model demonstrated that PSM mixers are more effective and efficient in delivering mixing performance (Tables 2-5), with equivalent or reduced energy usage compared to linear motion mixing (up to 54% reduction in energy consumption). Moreover, analysis demonstrated a greater portion of tank volume at or above critical velocity when using PSM mixers vs. the alternatives. Results of the CFD analysis demonstrate further advantages (i.e., greater delta in volume above critical velocity) in high solids conditions, such as those resulting from Omnivore thickening or codigestion with high-solids food waste and evaluated as part of the lithium tracer testing. Recuperative Thickening Performance Test: An SST-focused 5-day performance test demonstrated acceptable operation of the recuperative thickening system (Table 6). In addition, an extended 30-day test completed at the request of the WQCP demonstrated continuous and overnight operation. Summary: The Omnivore system effectively addressed the biosolids and residuals management needs of the WQCP leveraging existing infrastructure and provided third-party validated performance improvements. As a result of the project's success, the below benefits were delivered to the WQCP: - Avoided major capital expenditure of an additional digester - Addressed capital improvement needs - Redundant digester capacity - Reliable production of stabilized biosolids - Improved digester performance - Improved mixing performance - High-efficiency mixers with lowest overall lifecycle cost - Future-proofing for load growth and changes in feedstock composition - Enable codigestion of organic waste - Support for increased biogas production and energy neutrality A similar solution may be replicated at other WRRFs to cost-effectively improve biosolids management while significantly enhancing the ability of municipalities to leverage existing infrastructure for meaningful resource recovery. This session will discuss the considerations, advantages, and applications of implementing HSD at WRRF such as the WQCP. It will further detail third-party acceptance testing data demonstrating the successful operation of the Omnivore system and HSD processes, and achievement of a new standard in high-performance mixing. Discussion will include agreement between the in-field performance testing and modeled mixer perform

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

SpeakerLaub, Margaret

Presentation time

10:15:00

10:45:00

Session time

8:30:00

11:15:00

Session number19

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicAerobic Digestion, Mixing Efficiency, Recuperative thickening

Author(s)

S. Purswani

Author(s)S. Purswani1; M. Laub2; A. Dale3

Author affiliation(s)Anaergia; 1Residuals and Biosolids Speaker; 2Anaergia Services LLC; 3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May, 2022

DOI10.2175/193864718825158407

Volume / Issue

Content sourceResiduals and Biosolids

Word count31

Full-Scale Biosolids Drying and Pyrolysis

Abstract

Polyfluoroalkylated substances (PFAS) and other contaminants of emerging concern (CECs) pose a major threat to the future land application of biosolids. Anaergia has developed a high temperature pyrolysis technology that converts biosolids into a pyrolyzed biosolids fertilizer product with no detectable level of PFAS or CECs. This technology will soon be commissioned at the Rialto Bioenergy Facility (RBF) in Southern California. In developing this technology, Anaergia conducted bench and pilot scale trials to study the conditions required to eliminate PFAS and develop a mass and energy balance for a full-scale pyrolysis system. Trials showed that pyrolyzed biosolids produced at 650oC showed no measurable level of common PFAS or CECs. The pyrolysis system at RBF will be designed to produce about 0.4 metric tons of pyrolyzed biosolids per metric ton of dried solids fed to the system. Perennial ryegrass pot studies showed that grass treated with pyrolyzed biosolids grew faster and developed longer roots than grass treated with dried biosolids and commercial fertilizers. Field studies with commercial food crops in Southern California showed that avocado and lemon crops treated with pyrolyzed biosolids showed no significant difference in leaf tissue and soil analysis than crops treated with conventional synthetic fertilizer products. Further investment in biosolids pyrolysis projects is expected to be driven by government policy limiting the land application of biosolids, demand for sustainable fertilizer products and private sector demand for carbon-removal projects

Case studies in pyrolysis, or the thermal decomposition of organic matter at elevated temperatures in the absence of oxygen. During pyrolysis, volatiles including CECs such as PFAS volatilize to a high heating value gas phase that can be harnessed for biosolids drying or other energy use. Remaining solids are carbon-rich with high nutrient content suitable for direct land application or blending into fertilizer. Pyrolysis represents a critical tool to sustainably manage biosolids and support

SpeakerLaub, Margaret

Presentation time

16:30:00

16:50:00

Session time

15:30:00

17:00:00

SessionFull-scale Thermal Drying System Implementation

Session locationRoom S501d - Level 5

TopicAdvanced Level, Energy Production, Conservation, and Management, PFAS, Sustainability and Climate Change

Author(s)

Laub, Margaret

Author(s)M. Laub 1; M. Laub 1; G. Van Every 1; C. McClelland 3; D. Barry 4;

Author affiliation(s)Anaergia 1; Anaergia 1; Anaergia 1; Anaergia 3; Anaergia 4;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2023

DOI10.2175/193864718825159030

Volume / Issue

Content sourceWEFTEC

Word count6

Description: Full-Scale Biosolids Drying and Pyrolysis for PFAS Destruction and Organic Nutrient...

Full-Scale Biosolids Drying and Pyrolysis for PFAS Destruction and Organic Nutrient Recovery

Abstract

Overview: Pyrolysis is the thermal decomposition of organic matter at elevated temperatures (250-750 °C) in an inert atmosphere (i.e., in the absence of oxygen). During pyrolysis, volatiles including contaminants of emerging concern (CECs) such as PFAS are driven off into a high heating value gas phase that can be harnessed for biosolids drying or other onsite energy use. The remaining solids are a carbon-rich biochar with high nutrient content suitable for direct land application or blending into high value fertilizer product. Pyrolysis represents a critical tool to sustainably manage biosolids and support effective resource recovery for nutrients and energy. Pyrolysis will become increasingly valuable as biosolids management options are expected to be further constrained by state and national policies including landfilling bans, land application restrictions, competition for compost capacity, and federal PFAS regulations. Located in Rialto, CA, Rialto Bioenergy Facility (RBF) provides an important case study as the largest biosolids pyrolysis facility constructed in North America. It is designed and permitted to process 300 tons per day (TPD) (equivalent to 75 dry tons per day, DTPD) of dewatered biosolids from municipal WWTPs. The facility is owned by Anaergia, who is responsible for design, construction, financing, operations, and maintenance of the facility, as well as feedstock management and marketing and distribution of the biochar end-products. Low temperature belt dryers and a subsequent Anaergia-developed and -patented high-temperature pyrolysis process converts Class B Biosolids into a biochar product (Class A) for use as a fertilizer. The facility's drying operations currently operate continuously, twenty-four (24) hours per day and seven (7) days per week. The proprietary pyrolysis system will begin commissioning in Q1 2023 with commissioning data and lessons learned to date available for conference date of May 2023. The goals of this plant include: -Maximizing biochar value by eliminating PFAS and other contaminants of emerging concern (CECs) while maximizing carbon and nutrient yield -Maximizing heat recovery for autothermal drying -Meeting South Coast Air Quality Management District (SCAQMD) permitting limits -Demonstrating successful full-scale operation of biosolids pyrolysis Process Description: Feed Handling: RBF receives up to 300 tons per day of dewatered biosolids from municipal WWTP's in Southern California, which are transported to the facility via end-dump truck. The offloading area at RBF includes one (1) below-grade reception bin dedicated for biosolids receiving. The bins are vented to an odor control system and piston pumps are used to transfer the biosolids to a storage silo, prior to pumping to the belt dryers for processing. Drying: The dewatered biosolids are dried to 90% total solids (TS) in two (2) 5-tph evaporation capacity belt dryers. While the pyrolysis system is in construction, dryers currently recover heat from CHP engines on site; the dryers will ultimately recover heat from the pyrolyzer via thermal oil. Dryer foul air passes through an ammonia scrubber, regenerative thermal oxidizer (RTO), and SOx scrubber to meet SCAQMD requirements before being released to atmosphere. Dried product recycle is used in the dryers to produce a granular Class A dried biosolids product. From the dryers, the dried biosolids are pneumatically conveyed to a nitrogen blanketed biosolids storage silo with truck loading, or conveyed to the pyrolysis system for carbonization. Pyrolysis: Biosolids from the dryer are forwarded to a 3.5 tph indirectly heated pyrolysis unit where the biosolids are converted in the absence of oxygen to pyrogas and biochar. Biosolids are processed at temperatures up to 1600 degrees F with adjustable residence time to maximize fixed carbon yield while eliminating PFAS and other CECs (see Table 1). Out of the pyrolyzer, the biochar is cooled to below 40 degrees C before being forwarded to bagging or storage. Pyrogas generated via this process is sent through heat traced pipe directly to the thermal oxidizer. Thermal Oxidizer, Heat Recovery, & Flue Gas Cleaning: The pyrogas from the pyrolyzer is processed directly in a multi-stage low-NOx thermal oxidizer (TO) with >2 seconds residence time. The TO is used to eliminate volatile organic compounds (VOCs) and contaminants of concern in the pyrogas, release their available heat while keeping NOx limts below 200 ppmvd@3%O2. Downstream of the TO, flue gas passes through a thermal oil heat exchanger from which recovered heat is directed to the dryers to achieve energy neutral operation. Flue gas is subsequently treated via Selective Catalytic Reduction (SCR), SOx scrubbing, and mist/particle elimination. This system provides best available control technology (BACT) and is permitted in SCAQMD among the nation's most stringent with NOx <30 ppmvd@3%O2 and SOx <1ppmvd@3%O2. Downstream of the flue gas cleaning equipment, induced draft fans are used to motivate the pyrogas and flue gas through the system while maintaining a slight vacuum through the entire system to eliminate any fugitive emissions. Biochar End Use: Carbon- and nutrient-rich biochar produced at RBF will be transported approximately 15 miles to a local Anaergia-owned fertilizer blending facility. The product is a nutrient-balanced fertilizer with high levels of nitrogen, phosphorus, and potassium, with significantly lower carbon intensity than traditional fertilizers. As a carbon-negative product, carbon removal credits from biochar production will be sold on the voluntary market. This approach maximizes the value that can be realized from the biochar product, allows direct to consumer sales to commercial agricultural operations, and facilitates direct replacement of conventional commercial fertilizers, reducing barrier to entry for end-users. As the remaining mass is approximately one-eighth to one-tenth that the inbound biosolids, the biochar may be much more readily managed. Research conducted by Anaergia indicates that crops perform equally as well when fertilized with blended biochar product as with conventional commercial fertilizers. Numerous studies indicate additional environmental benefits from use of biochar for agriculture, which may be referenced in the presentation. Benefits for Biosolids Generators: In addition to environmental benefits associated with pyrolysis and biochar use, RBF pyrolysis provides operational benefits to biosolids generators. RBF is contracted to receive biosolids from municipal generators throughout Southern California. RBF provides municipalities with a Class A biosolids management outlet and can offer guaranteed and/or fail-safe capacity. As a regional biosolids disposal option, RBF allows municipalities to achieve reduced vehicle mileage associated with hauling of biosolids to farther-flung alternative outlets, as well as improved service reliability and hauler availability resulting from reduced trip time. Pyrolysis at RBF offers destruction of PFAS and other CECs, providing 'future-proof' compliance to WRRFs for anticipated regulations pertaining to biosolids management and land application. Lessons Learned: Lessons learned from the design, permitting, construction, and commissioning phases of North America's largest biosolids pyrolysis facility will be shared. Data presented will focus on air emissions, mass and energy balances, and analysis confirming PFAS and CEC destruction through the operating pyrolysis system. Discussion may include favorable applications and various delivery approaches.

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

SpeakerLaub, Margaret

Presentation time

15:45:00

16:15:00

Session time

13:30:00

16:45:00

SessionSession 16: Advances and Innovations in Thermal Processes I

Session number16

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicThermal Processes and Biochar

Author(s)

M. Laub

Author(s)M. Laub1, G. Van Every2, 3, 4,

Author affiliation(s)Anaergia1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158856

Volume / Issue

Content sourceResiduals and Biosolids

Word count13

Description: South San Francisco-San Bruno Water Quality Control Plant Digestion Capacity...

South San Francisco-San Bruno Water Quality Control Plant Digestion Capacity Expansion Within Existing Plant Infrastructure Via High Solids Digestion

Abstract

Technology Overview:
Anaerobic digestion (AD) biologically degrades municipal wastewater solids and other organic waste streams. Typical AD at municipal water resource recovery facilities (WRRFs) receive primary sludge (PS) and thickened waste activated sludge (TWAS) at 4-5% total solids (TS) and operate at 2-3% TS. Volatile solids (VS) in TS are converted over ~15-day solids retention time (SRT) to produce biogas and stabilize sludge. In conventional digestion, SRT and hydraulic retention time (HRT) are equal. Anaergia's two-part Omnivore AD platform triples capacity of existing digesters to maximize existing WRRF infrastructure and provide redundancy. Anaergia's sludge screw thickener (SST) (Fig. 1) recuperatively thickens digestate to decouple SRT from HRT, allowing digesters to operate at significantly higher solids content at similar SRT and greatly reduced HRT. (Pre-thickening is available if preferable given existing site configuration.) Excess water is separated from digestate and returned to headworks for treatment and/or nutrient recovery, while thickened solids (~12%TS) are returned to the digester (Fig. 2). Digestate is thickened and returned to the digester, enabling the digester to operate at up to three-times the solids concentration (6-8% TS), with organic loading rates up to 0.33 lb-VS/ft3/day. By decoupling SRT from HRT, Omnivore provides SRT well over 15-day requirements for regulatory compliance and stable digester operation. Mixing is an essential component of digestion and has historically been limited to technologies that operate at lower solids content. To ensure proper mixing at higher solids, Omnivore employs robust low-speed, high-torque permanent synchronous magnet (PSM) mixers (Fig. 3). These high-efficiency submersible propeller mixers effectively mix high viscosities resulting from digestate thickening. Omnivore achieves a high standard of mixing performance, over 90% of digester volume continuously above critical velocity (0.3 ft/s) ensuring maximum volatile solids destruction, biogas production, and limited grit settling or upset events such as rapid rise. The cost-effective retrofit unlocks digester capacity and increases redundancy while improving digester performance. With additional AD capacity, WRRFs can rapidly accommodate increased internal sludge loads, external high strength waste (HSW) for co-digestion, and improve resiliency.
Application: South San Francisco-San Bruno Water Quality Control Plant (WQCP) capital improvement planning identified a need for additional AD capacity and initially prescribed construction of a new AD facility. Design by Carollo Engineers incorporated Omnivore retrofits to the existing AD system to cost-effectively provide necessary capacity and avoid the need to build an additional digester. The retrofit also provides flexibility for future co-digestion of HSW and increased biogas production. In late 2020, construction was completed to retrofit Digester 1 (0.83 MG) with Anaergia's Omnivore high-solids digestion (HSD) system. The Omnivore package included one skid-mounted SST for recuperative thickening, three high-solids submersible PSM digester mixers, three mixer service boxes, and all ancillary equipment. Existing mixers were removed from Digester 1 and replaced with Anaergia mixers, selected for low energy demand, low operation and maintenance cost, and efficient performance. Platforms installed provide access to Anaergia service boxes (Fig. 3), enabling in-situ mixer access without interrupting operations. Each mixer is mounted to a vertical post inside the digester allowing for height and attack angle adjustments to achieve optimal mixing, resuspend settled grit, and break scum accumulation. SST and accessory equipment were installed adjacent to Digester 1, reducing pump energy, footprint, and impact on WQCP operations.
Validating Omnivore HSD: Digester 1 was brought online January 5, 2021. Recuperative thickening was initiated in February and achieved steady performance in April (Fig. 4). Third-party performance testing was conducted in conjunction with Anaergia from April to July 2021. Performance criteria were evaluated and achieved (Table 1): - Minimum volatile solids reduction (VSR) above 57%, for 80% of the 90-day test period, over a 30-day moving average (Fig. 5) - Demonstrate stable digester operation with volatile fatty acid (VFA)/alkalinity ratio <0.2 (Fig. 6) Testing further confirmed successful HSD in Digester 1 as demonstrated by increased digester feed volumes, TS loading, and VSR, and steady OLR and VFA/alkalinity ratio. Note that design was developed to meet performance requirements and operational objectives requested by WQCP representatives and does not maximize use of Digester 1 volume. Operation at higher solids would further increase digester capacity for future growth needs or co-digestion.
Mixer Performance Testing: A third-party Lithium-ion Tracer test was conducted to confirm achievement of mixer performance requirements. Independent study (1) validated achievement of Anaergia's high-performance mixing standard (>90% of digester volume >0.3 ft/s) and (2) aligned with computational fluid dynamics (CFD) modeling of mixer performance, which indicated superior performance versus alternate mixing technologies. From Tracer testing, mixing efficiencies were confirmed from the washout curve (Fig. 7). Temperature profile indicated uniform temperature distribution within Digester 1, with a 1-degree C maximum variance between maximum and minimum temperatures (Fig. 8). Total solids concentration fell within +/-10% of the mean, indicating homogenous digester operation (Fig. 9). Tracer test findings are compatible with Anaergia's CFD analysis for the WQCP. Digester 1 was modeled with various mixer technologies present at the WQCP (Anaergia PSM, linear motion, and pump mix). The model was calibrated with published submittal sheet parameters for each mixer type and actual Digester 1 dimensions. The model compared energy usage and mixing performance (measured by percent of tank volume above critical velocity) for each technology at 2%TS and 6%TS. Anaergia's model demonstrated PSM mixers are more effective and efficient in delivering mixing performance (Tables 2-5), with equivalent or reduced energy usage compared to linear motion mixing (up to 54% reduction). Moreover, analysis demonstrated a greater portion of tank volume at or above critical velocity when using PSM mixers versus the alternatives. Results of CFD analysis demonstrate further advantages (i.e., greater delta in volume above critical velocity) in high-solids conditions, such as those resulting from Omnivore thickening or HSW co-digestion.
Summary: Omnivore leveraged existing infrastructure to effectively address biosolids and residuals management needs of the WQCP and provided third-party validated performance improvements.
The WQCP realized these benefits: - Avoided major capital expenditure of additional digester - Addressed capital improvement needs - Redundant digester capacity - Reliable stabilized biosolids production - Improved digester and mixing performance - High-efficiency mixers with lowest lifecycle cost - Future-proofing for load growth and feedstock composition changes - Enabled co-digestion of HSW - Support for increased biogas production and energy neutrality
Similar solutions may be replicated at other WRRFs to cost-effectively improve biosolids management while enabling municipalities to leverage existing infrastructure for meaningful resource recovery.
Session will discuss considerations, advantages, and applications of HSD at WRRFs. It will further detail third-party acceptance testing data demonstrating successful operation of Omnivore and HSD processes, and achievement of a new standard in high-performance mixing. Discussion will include agreement between in-field performance testing and modeled mixer performance for the WQCP, and implications.

South San Francisco-San Bruno Water Quality Control Plant (WQCP) implemented Anaergia's Omnivore anaerobic digestion platform to enable high solids digestion process and cost-effectively increase solids handling capacity. The system, comprised of high-solids mixers and recuperative thickening, eliminated the need for construction of additional new digesters at the WQCP and created additional capacity to support co-digestion. Overview of performance tests demonstrating successful operation.

SpeakerLaub, Margaret

Presentation time

13:35:00

13:50:00

Session time

13:30:00

15:00:00

TopicIntermediate Level, Biosolids and Residuals, Facility Operations and Maintenance, Municipal Wastewater Treatment Design, Nutrients

Author(s)

Laub, Margaret

Author(s)Sanjay Purswani1; Margaret Laub2; Brian Schumacker3

Author affiliation(s)Anaergia, Carlsbad, CA1; Anaergia, Carlsbad, CA2; City of South San Francisco, CA3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2022

DOI10.2175/193864718825158602

Volume / Issue

Content sourceWEFTEC

Word count20

Description: South San Francisco-San Bruno Water Quality Control Plant Employs High-Solids...

South San Francisco-San Bruno Water Quality Control Plant Employs High-Solids Digestion to Enable Food Waste Co-Digestion & Advance Energy Neutrality with Lowest Lifecycle Cost

Abstract

Executive Summary: South San Francisco-San Bruno Water Quality Control Plant (WQCP) incorporated high-solids digestion to cost-effectively provide necessary capacity and avoid the need to build additional digester tanks. Following third-party validation of healthy digester operations in high-solids conditions, the WQCP advanced a food waste co-digestion pilot in partnership with a nearby waste management authority. The pilot demonstrated significant increase in biogas production, without negative impact to digester health. The initiative not only sets the stage for the WQCP to advance energy-neutrality but also supports achievement of state-level organic waste diversion mandates in California to support greenhouse gas reductions. Background: The WQCP identified a need to rebuild the plant's three existing digesters due to seismic concerns and built additional AD to meet future load growth. While capital planning initially called for new construction of five (5) digesters total, Carollo Engineers conducted an alternatives analysis considering high-solids digestion to more cost-effectively achieve the required digester capacity. Carollo evaluated a scenario pairing two (2) conventional AD with one (1) high solids digester employing Anaergia's Omnivore high-solids digestion platform. Anaergia's two-part Omnivore AD platform triples capacity of existing digesters to maximize existing WRRF infrastructure and provide redundancy. Anaergia's sludge screw thickener (SST) (Fig. 1) recuperatively thickens digestate to decouple SRT from HRT, allowing digesters to operate at significantly higher solids content. By separating water from digestate, excess water is removed and returned to plant headworks for additional treatment and/or nutrient recovery, while thickened solids (typically 12% TS) are returned to the digester (Fig. 2). Digestate is therefore thickened up to three-fold (6-8% TS) thus tripling F:M ratio and enabling organic loading rates up to 0.33 lb-VS/ft3/day. By decoupling SRT from HRT, Omnivore ensures SRT well over 15 days required for regulatory compliance and stable digester operation. To ensure proper mixing in higher solids conditions, Omnivore employs Anaergia's high-torque submersible propeller mixers (Fig. 3). These high-efficiency mixers are designed to effectively mix high viscosities that result from thickening digestate and resist ragging. By applying mixing energy directly to digestate, Omnivore mixing achieves a high standard of mixing performance, over 90% of the digester volume continuously mixed above critical velocity (0.3 ft/s) ensuring maximum volatile solids destruction, biogas production, avoiding settling of grit, and homogeneity de-risking upset events such as rapid rise. The Carollo evaluation indicated that the proposed configuration leveraging high-solids digestion would deliver equivalent digester capacity to the originally planned five (5) tanks. Further, lifecycle cost analysis confirmed that the high-solids alternative would not only achieve CAPEX savings but OPEX savings, resulting in approximately 10% overall savings over the project life. OPEX savings to the WQCP primarily result from improved mixer energy efficiency and reduced polymer consumption associated with dewatering. Application: In late 2020, construction was completed to retrofit Digester 1 (0.83 MG) with the Anaergia Omnivore high-solids digestion (HSD) system. The technology package included one skid-mounted sludge screw thickener (SST) for recuperative thickening, three high-solids submersible PSM digester mixers, three mixer service boxes, and all ancillary equipment for a complete Omnivore system. Existing mixers were removed from Dig. 1 and replaced with new Anaergia propeller mixers. Mixer selection was validated and informed by computational fluid dynamic (CFD) modelling, the results of which are summarized in Tables 1-4. The model demonstrated low energy demand, improved tank mixing, and energy-efficient mixing performance, particularly in high-solids conditions (6% TS), as compared to linear motion and pump mix alternatives. Platforms installed provide access to Anaergia service boxes (Fig. 3), which enable in-situ mixer access without interrupting AD operations. Each mixer is mounted to a vertical post inside the digester allowing for height and attack angle adjustments to achieve optimal mixing, resuspend settled grit, and break scum accumulation in upper layers. The SST and accessory equipment were installed adjacent to Dig. 1, reducing pump energy, footprint, and impact on WQCP operations. Dig. 1 was brought online on January 5, 2021. Recuperative thickening was initiated in February and achieved steady performance in April (Fig. 4). Third-party performance testing was conducted in conjunction with Anaergia from April to July 2021. The below performance criteria were evaluated and achieved (Table 5): -Min. volatile solids reduction (VSR) above 57% for 80% of the time over 90-day test period, over a 30-day moving average (Fig. 5) -Demonstrate stable digester operation with volatile fatty acid (VFA)/alkalinity ratio <0.2 (Fig. 6) Testing further confirmed successful HSD in Dig. 1 as demonstrated by increased digester feed volumes, TS loading, and VSR. A third-party Lithium-ion Tracer test was conducted to confirm achievement of mixer performance requirements. The independent study (1) validated achievement of Anaergia's high-performance mixing standard (>90% of digester volume >0.3 ft/s) and (2) aligned with CFD modeling of mixer performance, which indicated superior performance compared to alternate mixing technologies. Co-Digestion Pilot: In July 2022, following successful completion of performance testing, the WQCP began a pilot program to receive 1-2 deliveries per day of slurried food waste. The organic slurry is produced at the South Bayside Waste Management Authority's Shoreway Environmental Center. The materials recovery facility (MRF) employs an Anaergia Organics Extrusion (OREX) press and Organics Polishing System (OPS) to remove contamination from commercial source separated organics and create a clean, homogenized, pumpable organic slurry. The slurry is pumped into 5,000-gallon liquid tanker trucks and hauled approximately 15 miles from the MRF to the WQCP. The slurry is fed to Dig. 1 for co-digestion with indigenous biosolids. The high-solids digestion upgrades have facilitated the pilot by provided excess capacity for external feedstock, as well as high-solids mixing capability within the digester to maintain digester health and mixing performance. WQCP monitoring indicates significant increases in biogas production since the initiation of high-solids digestion and co-digestion, respectively. Ongoing data collection during the pilot will inform planning and design of food waste receiving and biogas utilization upgrades to facilitate long-term co-digestion and advance energy-neutrality at the WQCP. Note that the high-solids digestion design was developed to meet performance requirements and operational objectives requested by WQCP representatives and does not maximize use of Dig. 1 volume. Operation at higher solids would further increase digester capacity for future growth needs or expanded co-digestion. Conclusion: The Omnivore system effectively addressed the biosolids and residuals management needs of the WQCP leveraging existing infrastructure; provided third-party validated performance improvements; and facilitated a successful food waste co-digestion pilot. As a result of the project's success, the below benefits were delivered to the WQCP: -Avoided major capital expenditure of an additional digester -Addressed capital improvement needs -Redundant digester capacity -Reliable production of stabilized biosolids -Improved digester performance -Improved mixing performance -High-efficiency mixers with lowest overall lifecycle cost -Future-proofing for load growth and changes in feedstock composition -Enable co-digestion of organic waste -Increased biogas production and energy neutrality The cost-effective retrofit has the ability to unlock additional digester capacity and increase redundancy while simultaneously improving digester performance. With the additional AD capacity created, WRRFs can rapidly accommodate increased internal sludge loads, high strength waste (HSW) for co-digestion, and improve plant resiliency. A similar solution may be replicated at WRRF throughout North America to cost-effectively improve biosolids management while significantly enhancing the ability of municipalities to leverage existing infrastructure for meaningful resource recovery and energy neutrality.

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

SpeakerLaub, Margaret

Presentation time

14:30:00

15:00:00

Session time

13:30:00

16:45:00

SessionSession 07: Intensifying Digestion

Session number07

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicDigestion & Stabilization

Author(s)

M. Laub

Author(s)M. Laub1, 2, 3, 4,

Author affiliation(s)Anaergia1

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158847

Volume / Issue

Content sourceResiduals and Biosolids

Word count25

Description: Victor Valley Wastewater Reclamation Authority's Transition From Net-Zero to...

Victor Valley Wastewater Reclamation Authority's Transition From Net-Zero to Carbon-Negative Through Innovative Public Private Partnerships

Abstract

Building upon the momentum of a public private partnership (P3) that delivered energy neutrality to Victor Valley Wastewater Reclamation Authority (VVWRA)'s Water Resource Recovery Facility (WRRF), VVWRA and Anaergia teamed to implement California's first WRRF-based pipeline renewable natural gas (RNG) project. This initiative demonstrates the critical role WRRFs of all sizes can play to combat climate change, increase resilience, and create alternative revenue streams.
Background: VVWRA operates a 14MGD advanced treatment facility in Victorville, CA. VVWRA sought to better utilize biogas, offset electricity costs, minimize energy price fluctuations, and achieve net-zero operations. Typically, facilities of this size have limited ability to accept outside waste, and produce insufficient biogas to offset energy demand. To achieve these goals and mitigate risk to the Authority, VVWRA partnered with Anaergia to design, build, and finance upgrades to increase digestion capacity and deploy biogas utilization infrastructure. Anaergia provided its Omnivore high-solids digestion package to retrofit a 300,000-gallon anaerobic digester, forgoing the need for additional tank volume. These upgrades significantly increased digestion capacity and solids destruction, allowing for the introduction of energy-dense organic wastes for co-digestion. In addition to digester retrofits, high-strength waste (HSW) receiving was installed, enabling receipt of up to 20,000 gallons per day. As biogas production increased, Anaergia procured two 800-kW dual-fuel combined heat and power (CHP) modules, which began operation in 2016. The system was sized to utilize all WRRF biogas and meet 100% of VVWRA heat and electricity needs. VVWRA realized significant cost savings from offset utility consumption and benefits from enhanced resilience.
Objective: The first phase of this partnership demonstrated operational and economic benefits of an organics-to-energy program for VVWRA. Further, it highlighted demand for alternative outlets for organic waste disposal, driven in part by landfill diversion mandates such as California Senate Bill SB1383. These mandates aim to reduce methane emissions from organic waste in landfills, which can instead be leveraged to generate renewable energy and offset fossil fuels. As a result, VVWRA sought to maximize use of remaining excess digester capacity to increase co-digestion of external HSW and expand on benefits realized thus far â€“ namely, delivery of valuable WRRF infrastructure upgrades, increased biogas production, and ultimately increased financial benefit under a P3 arrangement. A key consideration in further expanding biogas production was determining the most valuable use of biogas, and the most economical way to fuel the cogeneration engines.
Application: Anaergia worked with VVWRA on cost-benefit analysis to determine the most economically favorable beneficial use of increased biogas. At the scale achieved from an expanded co-digestion program, it was concluded that all biogas should be conditioned and upgraded to RNG for injection into the Southwest Gas pipeline. To maximize value to VVWRA, biogas would no longer be used to fuel the cogeneration system, which would instead run-on utility natural gas. Based on RIN and LCFS credit values vs. commodity prices, analysis confirmed that value of RNG sales more than offset the cost of natural gas purchases for CHP. The conclusions are consistent with findings of similar biogas projects throughout California and North America: when sufficient biogas production scale is achieved, maximizing biogas to pipeline RNG creates greatest value, even where CHP systems are in place. This is compounded by higher operating expenses for biogas CHP compared to biogas upgrading. This approach has added benefit of generating carbon-negative fuel, an invaluable tool in achieving carbon-neutrality goals and mitigating climate change. Project Overview: The public private partnership (P3) includes WRRF upgrades for expanded co-digestion (new liquids receiving station, high-solids mixers in each digester) and biogas utilization facilities (biogas conditioning, RNG membrane upgrader, and utility interconnection). Ancillary upgrades (e.g., dedicated digester feed lines) were provided to support overall WRRF operations and address capital improvement needs. The project tripled VVWRA co-digestion and associated biogas production. Under the P3, Anaergia provided design, construction, and financing. Anaergia owns and operates the biogas utilization facility, located on a parcel leased by Anaergia from VVWRA. Anaergia receives all biogas produced at VVWRA and provides conditioning (to remove contaminants such as H2S, VOCs, and siloxanes) and upgrading to produce pipeline-quality RNG. Carbon-negative RNG is 99% methane and delivered to the Southwest Gas point of receipt for pipeline injection and sale, offsetting fossil fuels. Anaergia manages interconnection and offtake agreements, as well as registration with state and federal renewable fuel standard programs to maximize renewable energy credits and RNG value. VVWRA will continue to own and operate co-digestion and ancillary upgrades. Given the well-established co-digestion program, VVWRA maintains responsibility for coordinating organic feedstock (charging $0.05/gal for HSW). VVWRA continues to benefit from energy resilience and electric grid independence via cogeneration using natural gas. In addition, VVWRA receives new revenue streams via lease payments from Anaergia, additional tipping fees, and RNG sales revenue sharing. Construction of RNG infrastructure began in 2020 and was completed in 15 months, sending RNG to Southwest Gas as of late 2021. Lessons Learned: Pairing existing public infrastructure with private investment provides an effective and responsible means to expand resource recovery capabilities, opening the door for ambitious and innovative initiatives. This partnership demonstrates a replicable model to transform wastewater treatment facilities into energy-neutral or -positive resource recovery centers. Private investment can revitalize existing infrastructure to support climate goals and advance a circular economy while limiting risk to agencies and ratepayers. The P3 model enables rapid project delivery at scale to provide meaningful environmental solutions. P3s are appropriate to provide much-needed infrastructure and create new revenue for WRRF capital needs and rate stabilization. Risk to agencies and ratepayers is limited: an experienced industry partner is responsible for project delivery and performance. WRRFs can focus on their core mission while sharing in the benefit of investment and revenue from resource recovery. Bioenergy projects need not impede â€“ and can significantly improve â€“ WRRF operations. Anaergia's compact biogas utilization facilities encompass less than one-quarter acre. Potential impacts to nutrient removal, solids handling, and dewatering are evaluated during development to identify necessary mitigation measures (e.g., Omnivore retrofits or sidestream treatment). Third-party financing may also be leveraged to address deferred maintenance and capital improvement needs beyond core project scope. Overall, P3 is an effective and appropriate tool to deliver infrastructure upgrades. RNG can maximize project value and climate impact. Anaergia analysis confirms it is generally most economically favorable for all biogas to be upgraded for pipeline RNG pipeline. RNG value is sufficient to justify investment in new facilities and increased utility natural gas consumption for existing systems. RNG value is driven primarily by federal and state renewable energy credits, which monetize the potential of carbon-negative RNG to reduce methane emissions, offset fossil fuels, and advance carbon-neutrality.

Building on a previous project that delivered energy neutrality to Victor Valley Wastewater Reclamation Authority (VVWRA)'s, VVWRA and Anaergia teamed to implement California's first wastewater co-digestion pipeline RNG project. This initiative demonstrates the ability of water resource recovery facilities of all sizes to prevent greenhouse gas emissions from organic waste and fossil fuel consumption, while improving infrastructure, increasing resilience, and creating alternative revenue streams.

SpeakerLaub, Margaret

Presentation time

09:00:00

09:15:00

Session time

08:30:00

10:00:00

TopicIntermediate Level, Utility Management and Leadership

Author(s)

Laub, Margaret

Author(s)Darron Poulsen1; Margaret Laub2

Author affiliation(s)Victor Valley Wastewater Reclamation Authority, Victorville, CA1; Anaergia, Carlsbad, CA2