REDUCTION OF NUTRIENT EMISSION BY SLUDGE HYDROLYSIS

Biological sludge hydrolysis was demonstrated in full scale at three D anish wastewater treatment plants. For primary sludge the hydrolysis y ield expressed in terms of filtrable COD varied from 9-16% of the tota l COD in the sludge (WTPs 1 & 2) and for the hydrolysis of activated s ludge a yield of 2.5% of the total COD was found. The addition of hydr olysate was demonstrated to improve the biological P removal considera bly. No effect on the nitrogen removal could be identified due to a fa vourable wastewater composition during the demonstration phase. A cost -benefit analysis showed that biological sludge hydrolysis may be a co st efficient process that should be considered in connection with the upgrading of wastewater treatment plants to nutrient removal. (C) 1997 IAWQ. Published by Elsevier Science Ltd.