Development of the intermittent cyclic process for simultaneous nitrogen and phosphorus removal

Technology to simultaneously remove nitrogen and phosphorus from wastewater by carrying out aerobic and anaerobic operations in a single reactor has been developed by the authors. The Intermittent Cyclic Process can be used with two reactors, operating at opposite stages, to receive and treat influent on an uninterrupted basis. Research has been carried out in the: laboratory; pilot plant; and in a 540 m3 full scale wastewater plant. Experiments with aeration time ratios (aeration time to total cycle time) from 0.125 to 1 have been made, and 0.125 yielded the best nitrogen and phosphorus removal results in the laboratory study. In the pilot plant average nitrogen and phosphorus removal rates of 86% and 82% were achieved. In over three years of operation, the full-scale plant realized rates of 87% and 74% respectively. Performance has further improved with our recently developed controller which uses “fuzzy logic” to automatically determine optimal mixing and aeration periods. Measurements of DO, pH, ORP, and reactor water level are constantly relayed to the fuzzy controller. Average nitrogen and phosphorus removal rates in the full-scale plant were 96% and 93%. The study demonstrates that the fuzzy controller is practical and enhances nitrogen and phosphorus removal.