[Nitrogen Removal Performance of a Sulfur/Pyrite Autotrophic Denitrification System]

In order to search for an economical, rapid, and highly efficient nitrogen removal process for sewage, a sulfur/pyrite packed column reactor was fed with low C/N municipal sewage. The effects of temperature, the sulfur-to-pyrite volume ratio, and hydraulic retention time (HRT) on nitrogen removal were studied. The results showed that with an influent total nitrogen (TN) of 40 mg·L^-1, the optimal HRT of the No.1 reactor was 2.5 h, and the removal rate and effluent concentration of TN were stable at 72.2% and 10.55 mg·L^-1, respectively. The optimal HRT of the No.2 reactor was 3.5 h, and the removal rate and effluent concentration of TN were stable at 67.8% and 12.90 mg·L^-1, respectively. The optimal HRT of the No.3 reactor was 3.5 h, and the removal rate and effluent concentration of TN were stable at 60.6% and 15.00 mg·L^-1, respectively. The sulfur/pyrite autotrophic denitrification system starts faster than the pyrite autotrophic denitrification system. Its nitrogen removal rate decreased with decreasing sulfur-to-pyrite volume ratio. The nitrogen removal performance of the system is not sensitive to temperature, and the denitrification performance is better than that of the system with pyrite alone as the sulfur source. The main functional bacteria in the system are Sulfurimonas and Thiobacillus, and the proportion of the sum of these two bacteria in the three reactors decreased from No.1 to No.3.