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Since 1998, the Eastern Municipal Water District (District) has developed and successfully operated a heat pasteurization facility to treat extended aeration waste activated sludge (WAS) from the Perris Valley Regional Water Reclamation Facility (PVRWRF). The treatment train uses hot water to sludge spiral heat exchangers and a patented continuous-feed, complete mix pasteurization vessel (heated sludge holding tank). Treated biosolids are dewatered on belt filter presses and applied to farmland either within 8 hours of pasteurization or after air drying to 75 percent total solids on sludge drying beds.The pasteurization process has proven to be reliable and cost effective. Tests for fecal coliforms have consistently demonstrated that the pasteurization system produces Class A biosolids when operated at 158 degrees F in accordance with the Part 503 requirements. Based on fecal coliform monitoring, Class A biosolids could possibly be produced at temperatures below 158 degrees F. However, additional monitoring of parasites and viruses should be conducted to establish the minimum required temperature for complete pathogen inactivation Pasteurization does not adversely impact the downstream dewatering process or appreciably change the nutrient quality of the biosolids.From a national perspective, the pasteurization offers several potential advantages for POTWs with aerobic digesters which can not meet Class B biosolids standards: (1) cost effective production of Class A biosolids, (2) potential use of waste heat generated from engine driven blowers and pumps, (3) elimination of dust, odor and vector problems of composting and other open air processes, and (4) compact facility design with minimal land requirements and minimal manpower requirements.

Biofiltration is an increasingly popular technology for treating of foul air at biosolids composting facilities employing static pile or invessel processes. The Rancho Las Virgenes Composting Facility (Rancho), located in western Los Angeles County, provides biosolids treatment, including anaerobic digestion, dewatering, and in-vessel composting, for customers served by the Rancho Las Virgenes Municipal Water District (District), the facility operator, and Triunfo Sanitation District. Rancho employs an in-vessel system to treat dewatered, anaerobically digested solids and produces a soil amendment for local distribution and marketing. Over several years, the District has worked closely with Black & Veatch Corporation to investigate the operation of the Biofilter and to develop enhancements that optimize performance.In 2000, Black & Veatch conducted a study to evaluate the performance of the Biofilter and recommend improvements to enhance its short-term and long-term operability. A $1 million construction project was recommended to provide a major renovation and expansion of the Biofilter. The recommended design included complete rehabilitation of four existing zones of Biofilter, two new-slab-on grade concrete zones equipped with air distribution channels and drainage system, and other improvements. The schedule requires that the two new concrete zones be in service by the end of October 2001 and other improvements to be completed by the end of December 2001.After award and negotiation of the contract, an equipment vendor approached Black & Veatch, the District, and the Contractor about modifying the design of the concrete zones to use BacTee aeration floor system. Benefits to the District include savings in capital costs and construction time, enhanced air and moisture distribution, longer media life, and potential energy saving. The District negotiated a construction change order to incorporate the aeration floor system. This paper presents the results of the study, including the Biofilter's operating history, long-term design recommendations, and a cost analysis of biofiltration options. Discussion of how the design recommendations were refined and incorporated in the final detailed design of the Biofilter and how the change order for the aeration floor system was incorporated to provide a state-of-the art biofilter is also included.

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The Encina Wastewater Authority (EWA) is implementing a Biosolids Management Program to serve the agency's long-term biosolids management needs through 2025. First, EWA developed a Biosolids Strategic Plan, which was completed early in 2002. The Biosolids Strategic Plan provides valuable information for other agencies embarking upon biosolids management programs. EWA's Biosolids Strategic Plan included an investigation of regulatory issues, facility siting Class A biosolids treatment technologies; a more detailed evaluation of heat drying and pre-pasteurization alternatives using economic and economic criteria; and an assessment of heat dried biosolids product markets in Southern California. Based on the evaluation of both cost and non-cost factors, heat drying using either single or dual trains for redundancy was identified as the preferred option. A potential Southern California market was determined through a telephone survey of local fertilizer companies to determine their interest in a heat dried biosolids fertilizer product. Subsequently, EWA developed the conceptual design of a new solids processing facility that will consist of high solids centrifuges, one or more heat dryer trains, and associated support facilities.