Nitrogen and phosphate requirements for the anaerobic digestion of a petrochemical effluent

Abstract

This study was undertaken to determine the minimum nitrogen and phosphate concentrations at which the downflow fixed-bed anaerobic reactor could still operate efficiently. Results obtained from the first phase of the study showed that urea could be successfully substituted by ammonia, when the reactor population became acclimatized to the newly added nitrogen source. In the second phase it was found that the substrate phosphate concentration necessary for efficient reactor performance, could be lowered from 115 to 8 mg l −1 as PO 4-P. At this level no phosphate could be detected in the reactor effluent. In the final phase the substrate ammonia concentration was lowered from 1060 to 45 mg l −1 TKN. At these low phosphate and nitrogen concentrations, the reactor was still able to operate at COD (Chemical Oxygen Demand) removal efficiency > 95%.