Surti, Jay

Jay Surti is the East Regional Biosolids Manager at GHD.

Titles from this speaker

Description: Alternate: Advancements in Wastewater Solids Management for the City of Cuenca,...

Alternate: Advancements in Wastewater Solids Management for the City of Cuenca, Ecuador

Abstract

The City of Cuenca is a large metropolitan City located in the high lands of Ecuador at about 2,560 meters above seal level. The wastewater collection and treatment system for the City consists of approximately 1,300 kms of sewage networks and 80 kms of interceptor networks that convey wastewater to various treatment plants, the Ucubamba WWTP being the largest of all treating approximately 95% of wastewater produced by the City. The rated design capacity of the Ucumamba WWTP is 1.8 cubic meter per second (m3/sec). The treatment process at the Ucumamba WWTP consists of preliminary treatment consisting of screens, followed by a 3-step biological process consisting of primary aerated lagoons, secondary facultative lagoons and tertiary maturation lagoons. Exhibit 1 is a process flow diagram of the Ucumamba WWTP liquid treatment process. The Ucumamba WWTP is challenged with accumulation of solids in the lagoons. In 2013 the City installed sludge removal and dewatering system to remove and process approximately 3,000 cubic meter of sludge per year (m3/year). However, the sludge removal and dewatering is capacity limited to remove and process sludge accumulated in the facultative lagoons. As a result, approximately 50% of the lagoon volume is occupied by sludge, thereby reducing the active hydraulic retention time, and leading to compromised treatment efficiency. To address challenges with reduced treatment capacity of the Ucumamba WWTP, reduce dependence on the Ucumamba WWTP to meet the City's treatment needs, and diversify treatment options to meet future growth, the City completed the design of the new Guangarcucho WWTP having a rated design capacity of 1.8 m3/sec. With the new Guangarcucho WWTP being operational, the City will be able to effeciently treat wastewater produced by the City and remove portions of the Ucumamba WWTP out of service for maintenance and sludge removal to restore capacity. Exhibit 2 summarizes the future wastewater treatment strategy for the City of Cuenca after the Guangargucho WWTP becomes operational. Wastewater biosolids are considered a valuable resource in Ecuador due to the high nutrient content and its benefit to the agricultural industry. Evaluation completed by the City indicate that the sludge removed from the Ucumamba WWTP is low in nutrients (nitrogen) due to the prolonged stabilization and meets EPA Part 503 Class B biosolids standards. As a comparison, the wastewater biosolids to be produced by the advanced Guangarcucho WWTP is assumed to have a high nutrient content and potential to meet EPA Part 503 Class A biosolids standards. The liquid treatment process for the Guangargucho WWTP consists of preliminary treatment (screening and grit removal), primary clarification, biological treatment, secondary clarification and disinfection. Primary sludge produced by the primary clarifiers will be thickened in gravity thickeners and waste activated sludge produced by the secondary treatment process will be thickened with gravity belt thickeners (GBTs). Thickened primary and waste activated sludge will be anaerobic digested and dewatered with centrifuges. Exhibit 3 provides the process flow diagram of the solids treatment process at the Guangarcucho WWTP. Limited quantity of biosolids currently produced by the Ucumamba WWTP is currently conveyed to the Pichacay Landfill for disposal. However, the Pichacay Landfill is nearing the end of its service life by 2031, and thus does not have the capacity to accept additional biosolids to be produced by the City's Ucumamba and Guangarcucho WWTP in the future. The City is currently challenged to find disposal or beneficial use options for biosolids produced by the two WWTPs. In addition, there are no regulations to regulate the general conditions and obligations to be fulfilled for beneficial use of biosolids e.g. land application. To address its biosolids management challenges, the City has initiated a Feasibility Study to investigate treatment and beneficial use options to manage biosolids that will be produced by the two WWTPs in the future. The treatment approach will focus on maximizing reduction in mass and volume of biosolids that will require outside the fence management, and produce high quality biosolids that can be beneficially used for agriculture and/or mine reclamation. Treatment solutions that will be investigated include thermal drying, solar drying, incineration and innovative treatment solutions such as pyrolysis and gasification to produce value derived products such as biochar. Beneficial use opportunities for biogas to be produced by anaerobic digestion at the Guangarcucho WWTP will also be investigated e.g. cogeneration, biosolids drying, etc. The paper will provide an overview of the current and future wastewater treatment for the City of Cuenca, and the challenges the City faces to sustainably manage biosolids that will be produced by the Ucumamba and Guangarcucho WWTPs in the near future. An overview of treatment options investigated to achieve a reduction in mass and volume of biosolids requiring end use management, advantages and disadvantages of the various alternatives and a triple bottom line evaluation to identify the most cost-beneficial alternative will be presented. Consideration of other factors such as operational and maintenance know how, energy requirements and costs, availability of manufacturer services and spare parts in Ecuador will also be considered in selecting the preferred treatment approach. The presentation will be useful to Utility Managers, Consultants and Engineers who also face biosolids processing and management challenges similar to the City of Cuenca. The paper will provide the attendees an understanding of a Citywide approach and initiatives to implement a sustainable biosolids management strategy in a resource constrained environment. The paper will also provide an overview of the City's existing and planned wastewater collection and treatment infrastructure.

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

SpeakerSurti, Jay

Presentation time

13:30:00

17:00:00

Session time

13:30:00

17:00:00

Session number02

Session locationGreater Columbus Convention Center, Columbus, Ohio

TopicBiosolids Management, Technology Comparison, Thermal Processes

Author(s)

J. Surti

Author(s)J. Surti1; J. Vicuna-Reyes2; F. Sarmiento3

Author affiliation(s)Greeley & Hansen; 1Greeley and Hansen; 2Greeley and Hansen; 3

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2022

DOI10.2175/193864718825158425

Volume / Issue

Content sourceResiduals and Biosolids

Word count13

Description: The Opportunity for Water Resource and Recovery Facilities to Advance Regional GHG...

The Opportunity for Water Resource and Recovery Facilities to Advance Regional GHG Reduction Goals

Abstract

The need for a circular economy and organic waste diversion regulations aimed at reducing carbon footprint is driving cities and utilities to adopt a holistic resource recovery approach for organic waste streams typically disposed in landfills. These waste streams can range from organic fraction of the municipal solid waste (MSW), pre-consumer waste streams such as those produced by food processing facilities, packaged food and beverages, biosolids produced by water resource and recovery facilities (WRRFs), and organic wastes produced by other City public service departments. States and cities across North America are developing plans and strategies to reduce greenhouse gas (GHG) emissions for climate change adaption and develop a circular (green) economy. The plans typically identify WRRFs as a strategic solution provider for sustainable organic waste management and resource recovery, and to produce value added products such as biogas, renewable natural gas (RNG) and/or compost. WRRFs are typically located in urban environments, in proximity to pre-consumer and post-consumer food waste generation, fats, oil and grease (FOG) waste streams, and have the treatment infrastructure to efficiently process and manage these waste streams. A 2012 Water Research Foundation (WRF) Study concluded that hauling of food waste to municipal WRRFs and utilizing it beneficially for resource recovery through anaerobic digestion (AD) results in reduction of carbon footprint of food waste management, when compared with other commonly adopted industry practices such as landfills and composting. Although the benefits of co-processing of organics waste streams with wastewater solids are uncontested, the adoption of this approach by utilities has been slow. This is primarily due to limited understanding of managing this feedstock, especially pretreatment/conditioning required to make these feedstocks more amenable to process in anaerobic digestion, system design considerations, permitting requirements and plantwide operational impacts. Using case studies summarized below, the authors will share their experience and lessons learned assisting early North American adopters with planning, design, construction, commissioning, and operation of organic resource recovery and co-digestion facilities. 1)Case Study 1 - Oneida County WPCP Energy Independence, Utica, New York: Beginning January 1, 2022, the New York State Food Donation and Food Scraps Recycling Law went into effect. This law prohibits large generators of food waste that produce more than 2 tons per week from disposing of that food waste as solid waste. To help meet the requirements of the recycling law and reduce greenhouse gas emissions, the Onieda-Herkimer Solid Waste Authority partnered with the Oneida County WPCP to process source separated organic food waste slurry in the new anaerobic digesters at the Oneida County WPCP. The Oneida County Solid Waste Facility is located adjacent to the Oneida County WPCP. Under the County's Food2Energy Initiative, the Solid Waste Authority has been able to divert food waste, which makes up approximately 22 percent of the waste stream, away from the Regional Landfill. The co-digestion of food waste slurry with wastewater solids has allowed the WPCP to enhance biogas production and electricity generation onsite. To fully utilize the biogas and eliminate flaring, the County plans to expand its cogeneration facility by installing two new 200 kW microturbines, in addition to three (3) existing 200 kW microturbines. The case study will provide the attendees an understanding of the successful partnership between the Solid Waste Authority and the WPCP, and the benefits to the WPCP to advance its energy independence and reduce its GHG footprint. Exhibit 1 Process Flow Diagram for Oneida County's SSO Pre-treatment and Conveyance 2)Case Study 2 - Central Marin Sanitation Agency Organic Waste Acceptance and Power Generation Program, San Rafael, California The State of California has promulgated several regulations to reduce GHG emissions; most notably SB 1383 promulgated to achieve 75 percent reduction in landfilled organic waste by 2025 and reduce short-lived climate pollutants in California. Beginning 2014, the Central Marin Sanitation Agency (CMSA) entered into a public-private-partnership with Marin Sanitary Service (MSS), a private solid waste service provider, to accept pre-consumer food waste. The pre-consumer food waste is co-digested together with wastewater solids produced by CMSA's WWTP and fats, oil and grease (FOG) collected from the service area. Biogas produced by co-digestion is conditioned and used as fuel in an existing internal combustion engine based cogeneration system for electricity generation. The Organic Waste Receiving Facility (OWRF) has been successfully operational for many years now. Lessons learned through years of experience include high strength waste (HSW, a mixture of pre-processed food waste and FOG) storage limitation at the WWTP, pumping and handling challenges due to high solids content and corrosive nature of the HSW stream, and shredded inorganics in the HSW slurry resulting in operating and maintenance nuisances and high operating costs. The authors are in the process of making improvements to the OWSF to provide dedicated fine screening and storage for FOG to address storage and HSW slurry quality challenges. The case study will provide the attendees an understanding of lessons learned, operational and maintenance challenges, and improvements CMSA plans to make. The other purpose of the improvements is to enhance utilization of available anaerobic digestion capacity to increase biogas production and operate the cogeneration system 24 x 7. The most unpredictable failure has been with hose breakdown for the peristaltic hose pumps. CMSA has averaged approximately six (6) hose replacements per year for the pumps. The following graphic is a process flow diagram of the upgraded OWSF. Exhibit 2 Process Flow Diagram of CMSA's Organic Waste Receiving Facility after Improvements. 3)Case Study 3 - Rialto Bioenergy Facility, California, United States: The Rialto Bioenergy Facility (RBF) processes approximately 700 tons per day (tpd) of organics/food waste recovered from solid waste through anaerobic digestion and 300 tpd of biosolids from external WRRFs into renewable electricity, renewable natural gas (RNG), and fertilizer products. Dewatered cake from external WRRFs and anaerobically digested biosolids is dried in two belt dryer units. The dried biosolids will be processed in a pyrolysis system and converted into syngas, bio-oil and a nutrient-rich biochar. The pyrolysis process is expected to become operational by Q1 2023. The produced syngas would be used to run the dryers, along with the waste heat from the cogeneration system. The pyrolysis oil will be recirculated in the anaerobic digesters to enhance biogas production. This case study will provide the attendees an understanding of how various innovative technologies can be combined to enhance energy recovery and reduce GHG footprint, and preliminary operating data will be presented. The Facility initially became operational in 2020. Exhibit 3 Aerial Image of the Rialto Bioenergy Facility

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

SpeakerSurti, Jay

Presentation time

9:30:00

10:00:00

Session time

8:30:00

11:15:00

SessionSession 19: Resource Recovery

Session number19

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicCase Studies/Lessons Learned