Operating experiences of a treatment plant designed for biological nutrient removal by pilot trials and mathematical modelling

Abstract An existing rendering plant wastewater treatment facility had to be up-graded to comply with new more stringent discharge consent standards. The rendering plant processes slaughterhouse waste materials to produce animal feed additives. The wastewater contains biodegradable organic substances, mainly organic acids and ammonia. The treated effluent is discharged to an adjacent river which feeds into nearby Lough Neagh. The revised consent standards required the removal of ammonia and new reduced standards for total-N and total-P are pending. The site trials indicated influent levels of BOD 1500–5000 mg/l and ammonia 250–750 mg/l. The discharge requirements were 20 mg/l BOD and 10 mg/l ammonia. The pilot trial results were tested against a mathematical model to verify the suitability of the treatment process and predict performance under full-scale conditions. An activated sludge plant with anoxic stage was constructed to provide nitrification-denitrification with phosphate removal by post-precipitation. This paper focuses on a comparison of predicted performance with the actual performance over an extended period.