Aerobic treatment of industrial waste water - experiences with the dosage of nitrogen and phosphorus

In industrial wastewater, especially from food industry, the concentrations of the organic compounds are usually high, whereas the contents of nitroge n and phosphorus are often low. For the aerobic treatment, the addition of nutrients to the industrial wastewater can be required. For ecological and economic reasons, this nutrient addition must be kept to a minimum. Uninten tional nitrification and denitrification lead to an additional demand of ni trogen and should therefore be avoided at such plants. Observations from tw o treatment plants (50 000 m(3)/d, 40 t COD/d) proved that the nitrogen dos age can be controlled by monitoring the ammonia concentration. if the contr ol procedure also considers the N/COD ratio in the raw wastewater (includin g the N dosage) and the organic sludge load of the last couple of days, ver y low effluent concentrations (NH4-N in the range of 0.3-0.5 mg/l) can be a chieved and the nitrogen dosage is low. If there are periods with nitrogen in excess, too, a minimum nitrification capacity has to be maintained by me ans of nitrogen addition in periods of deficiency. A control procedure for phosphorus addition is to keep a fixed P/COD-ratio in the raw wastewater (i ncluding P dosage). The PO4-P concentration is monitored in order to limit the maximum phosphorus dosage. Following this procedure, considerable savin gs of phosphorus have been achieved, keeping very low effluent concentratio ns (average Total-P<0.3 mg/l).