The Business Case for Optimizing the Operations, Maintenance, and Distribution of Pierce County's Biosolids Fertilizer Manufacturing Facility
Abstract:This paper documents the business case evaluation (BCE) used to determine the best alternative for optimizing the operations, maintenance, and distribution functions for the fertilizer manufacturing facility (FMF) at Pierce County Sewer Utility located in Pierce County, Washington. A BCE is an asset management tool that provides a structured, repeatable, defensible decision-making process based on risk, level of service, and life-cycle costing. Brown and Caldwell followed the steps outlined in Figure 1 to facilitate the FMF BCE with Pierce County staff.
The Pierce County Sewer Utility operates a 28.7 million-gallon-per-day wastewater treatment plant at Chambers Creek. The plant utilizes an anaerobic digestion process and in 2005 an FMF was designed and built, replacing the existing belt filter press dewatering with an Andritz centrifuge and pelletizing biosolids dryer system that uses a direct heat rotary drum dryer with a capacity of drying approximately 9,468 wet tons per year.
The FMF system has been operational since June 2006, producing a Class A biosolids product suitable for use as a commercial fertilizer. The product from this FMF is sold as SoundGRO fertilizer. Over the past 30 months, the County has been working to optimize all aspects of the FMF's operations, maintenance, and distribution functions. This BCE brought members of the Operations, Maintenance, and Distribution groups together to discuss current work methods and processes and to brainstorm ways to optimize the operations schedule, maintenance management, and distribution storage for the FMF.
In order to determine optimal practices, the level of service goals for the FMF's operations, maintenance, and distribution were first defined. The defined levels of service included meeting Class A requirements and nutrient guarantees set by regulatory agencies, providing a consistent and reliable product to their customers, selling the SoundGRO product rather than giving it away, and selling no more than 25 percent of the product to any single customer.
This paper presents a full analysis of nine alternatives that were developed along with the lifecycle costs, benefits, and risks associated with each alternative. Recommendations are also presented and include individual recommendations for optimizing operations, maintenance, and distribution practices as well as overall recommendations for the sewer utility for the future use of the FMF.
Document Type: Research Article
Publication date: 2010-01-01
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