ABSTRACT
Three two-stage anaerobic sequencing batch reactor (ASBR) systems were used to treat dairy wastewater in the laboratory to evaluate a two-stage thermophilic-mesophilic system against a two-stage mesophilic-mesophilic system. The total working volume of 15 liters for each system was divided between the first- and second-stage reactors in the volume ratios of 1:4, 1:4, and 1:2 for the three systems, respectively. All three systems were automated to obtain precision feeding, decanting, and data collection using a computer-based control and data acquisition system. Organic loading rates of 2, 3, and 4 g VS/L/day were tested at the system hydraulic retention times of 3 and 6 days. The volatile (VS) removal varied from 26 to 44% with the thermophilic-mesophilic systems destroying 26–50% more VS than the mesophilic-mesophilic system. No fecal coliforms were detected in the effluents from the thermophilic-mesophilic systems compared to only two log reduction in fecal coliforms with the mesophilic-mesophilic system.
