Aerobic Treatment of Fruit Cannery Waste Water with Added Nitrogen

Abstract Increased land disposal costs and more stringent legislation implies more sophisticated treatment methods for food processing plant wastes. Fruit cannery wastes, characterized by high BOD values and very low N & P levels, present problems for biological oxidation systems. A pilot plant aeration system with sludge recirculation was used to determine the most suitable form of N for use as a nutrient supplement. It was possible, using a three compartment system, to achieve up to 99+ percent BOD removal with an average retention time of about 2.5 days. The final effluent was clear and was free of nitrate, nitrite and ammonia N. Use of a single aeration chamber with sludge recirculation (average retention time 30 hours) gave up to 98+ percent BOD removal. Sodium nitrate at 56 ppm added N was the only effective nitrogenous additive. Others tested (urea, ammonium phosphate, ammonium nitrate, sodium nitrite and ammonia) gave poor floe characteristics and much lower BOD removal.