Mesophilic vs Thermophilic Reactors in Warm Climates: What is the Best Option?

Aerobic thermophilic treatment technology offers significant advantages over mesophilic treatment processes especially in warm equatorial climates. This paper compares a thermophilic versus mesophilic design for a biopharmaceutical wastewater pretreatment plant in Southeast Asia, treating a high-strength, high-salinity wastewater. The analysis included a 65-day mesophilic bench-scale test compared to data obtained from a full-scale biopharmaceutical facility with similar wastewater that is currently operating a biological reactor (Chemostat with no recycle and <2 day solids retention time) on the low end of the thermophilic range (40°C). Stoichiometric and kinetic data are compared along with impacts on capital and operating costs. The thermophilic design yielded a smaller biological reactor and waste solids processing system; but required effluent cooling and extra odor control and safe handling for ammonia emissions because of the lack of nitrification at high temperatures. Mesophilic operation was ultimately selected because the high ammonia could be safely managed via nitrification.