Biosolids Heat Drying Using Waste Heat from a Combined Cycle Power Plant – City of Corona's Approach

The City of Corona serves a rapidly growing area of Southern California. The City operates three wastewater treatment plants (WWTPs), two produce reclaimed water for unrestricted reuse. The sludge from the three WWTPs is transported to a central sludge treatment facility located at WWTP No. 1. The sludge treatment facility consists of sludge receiving, thickening, anaerobic digestion, and dewatering.In the year 2000, the City was faced with two crises. First, the California power shortage and escalating cost of power severely impacted the industry and businesses. Second, bans on Class B biosolids land application and the partial shutdown of a local privatized composting facility where the bulk of the City's biosolids were processed or reused forced the City to transport bulk waste a much greater distance. To cost-effectively respond to these crises, the City decided form a municipal electrical utility to generate and supply power to its constituents by constructing a nominal 30-megawatt (MW) power plant. The feasibility study proved that locating the power plant at the City's largest WWTP produced significant synergies. The reclaimed water from the WWTP could be used for power plant cooling, the waste heat from the power plant could be recovered and used to heat the digesters and in Class A biosolids processes, and the digester gas could be used for supplementing the fuel needs of the sludge dryer. Additionally, the power plant could supply the entire plant's electricity requirements and the combined facilities operation was more efficient than physically separate facilities. This paper presents the results of this analysis as well as the construction and operational aspects of the project.