Feasibility of Activated Sludge Treatment of Potato Processing Wastewaters

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Agricultural Wastes


Laboratory studies were undertaken to determine the feasibility of using the activated sludge process in treating liquid effluents generated from a potato processing plant in the Red River Valley in North Dakota, USA. The wastewaters contained average COD (Chemical Oxygen Demand) and alkalinity concentrations of 1870 and 390 mg litre-1. Factors affecting the activated sludge treatment unit performance were evaluated in this study. These included the hydraulic detention time in the aeration tank, the sludge age, and the dosage of powdered activated carbon added to the aeration tank. The hydraulic detection time was varied from 0·35 to 1·42 days, and the sludge age ranged from 1·96 to 4·86 days. Activated carbon dosages of 4000 mg litre-1 were maintained in three reactors, while three other reactors were without carbon addition. Nutrient additions of nitrogen and phosphate were employed to achieve effective biological waste treatment. Biological treatment removed from 87 to 98% of ammonia-nitrogen to give final effluent concentrations between 1·1 and 5·6 mg litre-1. Reactors without carbon addition removed 92 to 94% of COD with an effluent COD of 114 to 147 mg litre-1. With the addition of carbon the COD removal efficiencies increased to 94 to 96% with an effluent COD concentration of 67 to 108 mg litre-1. Based on this study, the activated sludge process can be used effectively in treating potato processing wastewaters to achieve an effluent COD of less than 100 mg litre-1. The design parameters include a hydraulic detention time of 1·43 days, a sludge age of 5 days, and a powdered activated carbon dosage of 4000 mg litre-1. © 1981.