[Performance of nitrogen and phosphorus removal of sulfur/limestone autotrophic denitrification system]

In order to investigate the performance of nitrogen and phosphorus removal of the sulfur/limestone system from low C/N municipal sewage, a sulfur/limestone packed column reactor fed with synthetic wastewater, and operated in the way of anaerobic biological filter was constructed. The effects of HRT, initial concentration of phosphate, pH and temperature on nitrogen and phosphorus removal were studied. The results showed that with influent of NO3(-) -N 30 mg/L, PO4(3-) -P 15 mg/L, the optimal HRT value was 6 h, and removal rates of TN and phosphorus were 100% and 44.64% respectively. Initial concentration of phosphate and initial pH had a significant influence on nitrogen and phosphorus removal. In order to keep nitrogen removal rate higher than 90%, initial concentration of phosphate should not be below 0.4 mg/L; the optimal pH value was 6.5, and removal rates of TN and phosphorus were 91.51% and 47.68% respectively. Temperature had a positive impact on that system, the nitrogen and phosphorus removal rate decreased with decreasing temperature. The nitrate removal efficiency was high in the temperature range of 18-30 degrees C, and the efficiency of phosphorus removal rate reached about 50%, when the temperature was between 25-30 degrees C. The dephosphorization behavior of sulfur/ limestone system correlated closely with autotrophic denitrification process, and the mechanism of phosphate removal of the SLAD system was mainly due to chemical precipitation. The system had the performance of nitrogen and phosphorus removal from low C/N municipal sewage, the highest phosphorus removal rate could reach 50%.