NUTRIENT REMOVAL FROM PIGGERY WASTE WITH SBR COUPLED WITH MEMBRANE: A FULL-SCALE EXPERIENCE

A full-scale sequencing batch reactor (SBR) plant coupled with reverse osmosis (RO) membrane was evaluated in this study. The plant was operated at 1.0 to 2.6 kgCOD/m3/d and 0.6 to 1.0kgN/oxic m3/d for SBR, and 28 to 40 L/m2/hr for membrane with pressure range from 179 to 330 psi. About 74.5% of nitrogen was removed by bio treatment and the remainder was removed by RO membrane system. In bio treatment process, about 60% of nitrogen was removed by denitrification, 15% by ammonia stripping and about 3% by sludge wasting. The phosphorus seemed to be removed by chemical precipitation in SBR, and later by membrane.Application of aerobic biological treatment to piggery waste with high COD and nutrients cause high temperature up to 44°C, which eventually inhibits activities of nitrifying bacteria. Based on this experiment, it was considered that the reactor temperature should not exceed 35°C to minimize nitrification inhibition. Most of nitrogen was converted to nitrite (NO2N) forms. Nitrite denitrification required less carbon source and additional chemicals did not need for nitrification because of suitable alkalinity recovery. Due to increase in ammonia uptake rate (AUR) and nitrite uptake rate (NUR), treatment efficiency increased.SBR effluent was directed to RO membrane system without any intermediate treatment. Shear force added on the membrane surface prevented fouling and biological slime build-up. Consequently continuous and stable flux and salt rejection rate were achieved; and decreased flux backed up again to the optimum level through periodical flushing and chemical cleaning. As a tertiary treatment method, applied RO membrane system suggested a new way of economic polishing method of biologically treated waste without any intermediate treatment.