Streamlined Multi Facility Residuals and Biosolids Master Planning with Triple Bottom Line Optimization

As regional utilities are faced with tighter regulations and simultaneous goals for economic and environmental sustainability, it is advantageous to identify synergies among multiple facilities to improve efficiency and performance. This approach was utilized to develop a County-wide short-term (5-Year) and long-term (25-Year) Residuals Management Master Plan for Westchester County (NY) Department of Environmental Facilities (DEF). Westchester DEF owns and operates seven Water Resource Recovery Facilities (WRRFs) with a combined capacity exceeding 190 MGD. These facilities currently produce 120,000 cubic feet of screenings and grit, and approximately 19,000 dry tons of biosolids annually for beneficial use and disposal.The 5-Year plan proposed strategies for optimizing existing facilities with a focus on reducing operational costs through reduction in residuals volume and more efficient energy usage. Commercial liquid sludge and dewatered cake hauling and disposal contracts are a large component of operating costs for DEF, amounting to $7.4 million annually, which makes volume reduction a priority for the County. In addition to providing facility-specific recommendations to improve operations, it was recommended that the County consolidate several facilities (Blind Brook, Port Chester, Ossining, and Peekskill WRRFs) by utilizing the additional capacity at the Peekskill WRRF to thicken, digest, and dewater. The recommendations presented in the 5-Year plan are expected to save the County $1.1 million annually on operations costs.The 25-Year plan employed the strategy of identifying specific triggers that would necessitate improvement. Four triggers were identified by Westchester County: (1) Class A biosolids requirements; (2) limited disposal options; (3) sustainability mandates; and (4) nutrient reduction requirements. A 7-step process was used to evaluate the recommended strategies for each trigger, with a focus on strategies that could support multiple triggers. A multi-facility Residuals Handling Evaluation and Optimization Tool was utilized to perform a triple bottom line analysis and identify the most suitable approach for meeting a trigger requirement in a streamlined manner. Seven of 20 different scenarios evaluated made it through the screening process. Based on this analysis, it was determined that retrofitting the existing digesters at the Yonkers Joint WRRF to operate Temperature Phased Anaerobic Digestion (TPAD) for processing cake from the New Rochelle, Peekskill, and Yonkers Joint WRRFs would be the most suitable option. In this scenario, three triggers are met: Class A biosolids requirements, limited disposal options, and sustainability mandates. Additional annual operations costs savings are anticipated to be $34 million per year after debt service for fully financed capital improvements.This paper describes the approach to multiple-facility planning in order to develop a Countywide short-term (5-Year) and long-term (25-Year) Residuals Management Master Plan for Westchester County DEF.The key elements of this manuscript include:Approach to evaluating current operations and establishing baseline conditions for short-term and long-term planning.Optimization of existing infrastructure to provide low-to-no cost short-term improvements and achieve substantial savings in annual operations and maintenance (O&M) costs.Multi-facility decision making process for long-term planning.