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The City of Los Angeles has developed an award-winning program of biosolids reuse, primarily by farmland application of mesophilically digested, dewatered cake. Unfortunately, California has witnessed a proliferation of county bans and restrictions on biosolids application. Kern County, one of the City's major application areas, recently adopted an ordinance that will require Class A biosolids beginning in 2003. The City is moving aggressively to achieve Class A biosolids by use of advanced, thermophilic digestion. Pilot and full-scale tests have been conducted to evaluate alternative flowsheets and to support design decisions for the selected flowsheet. It is believed that Hyperion is the largest U.S. wastewater facility currently committed to producing Class A material by on-site advanced digestion.

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Hyperion Treatment Plant, with an average design flow capacity of 1,700 mld (450 mgd), is the largest of four treatment plants owned and operated by the City of Los Angeles. Recently, the plant implemented a 76,000 l/d (20,000 gal/d) pilot facility to investigate the benefits of adding FOG to its anaerobic digesters. The results were promising showing significant improvements in digester gas production. Therefore, a study was conducted to research FOG and food waste market and evaluate digesters capacity to receive such high strength wastes. The study concluded that FOG volumes as high as 380,000 l/d (100,000 gal/d) would be available to the plant. The City of Los Angeles, however, decided to initially expand the facility by 190,000 l/d (50,000 gal/d). This paper describes the alternatives considered for expanding the facility. Pros and cons of each alternative along with corresponding costs are presented. Finally, recommendations for expansion of the facility are provided.