ABSTRACT
In 1980 a research program was initiated using bench-scale laboratory reactors to study an anoxic/anaerobic/aerobic treatment train for biological nutrient removal. In 1985 a pilot plant was constructed to field test the treatment process. These facilities were operated at varying flow and Qr/Q ratios, and at effective mixed liquor suspended solids (MLSS) concentrations. The results of 25-months of pilot-plant operational data indicated that the effluent concentrations of total BOD, TSS and nitrate nitrogen were less than 10 mg/L. Ammonia nitrogen was less than 2 mg/L. The solids settleability was excellent, and foaming due to Nocardia, was effectively controlled. Influent BOD concentrations of less than 89 mg/L significantly reduced the system’s ability to remove phosphorus. A strong relationship between the amount of carbon source in the influent, phosphorus release in the anoxic and anaerobic tanks and phosphorus uptake in the aeration basin was established.
