Biosolids Flow-Through Thermophilic Treatment Design and Implementation

Brown and Caldwell’s design to retrofit a 40 mgd wastewater treatment plant’s anaerobic digesters for the Columbus Water Works (CWW) used the first-of-its-kind Columbus Biosolids Flow-Though Thermophilic Treatment (CBFT3) process and cogeneration. CBFT3 converts the existing mesophilic digestion process to low-cost thermophilic digestion, produces Class-A biosolids, and reduces required batch processing times from an EPA-required 24 hours to 30 minutes, saving at least $3 million in capital costs. The new lean-burn engine generators produce 15 percent more power than previous generation engines or 60 percent more power than microturbines, with low exhaust emissions. This project is the first thermophilic anaerobic digestion project in the United States to be run entirely from heat generated from digester-gas-fueled power generation. Power generation has saved CWW as much as $19,000/week. The overall design produces a net carbon offset of 9,500 metric tons of CO2e emissions per year.