Decoloration and Nitrogen Removal of Swine Wastewater After Anaerobic Treatment Using the Sulfur Filling Up Reactor.

An innovative upflow sulfur filling up reactor was developed to remove nitrogen of swine wastewater after anaerobic treatment. This reactor consisted of a high DO upper layer filled with polyester unwoven cloth media and a low DO lower layer filled with sulfur pellet containing calcium (S0+CaCO3 pellet) . Anaerobically treated swine wastewater was supplied to the reactor from the middle layer. Overflow from the top of the reactor was partially recirculated to the bottom of the reactor, and the remainder was finally fed to a gravity settling tank. Removal efficiencies of NH4+-N and T-N were affected by the circulation ratio, and maximum removal (63% for NH4+-N, 42% for T-N) was observed at a circulation of 2. Accumulation of NO2--N was observed at a circulation ratio of more than2, but no accumulation of NO3--N was observed at any circulation ratio. Free ammonia concentration in influent and effluent was estimated to range from 4.9 to 100 mg/1 (average: 34.9 mg/l) . Free ammonia would inhibit oxidation of NO2--N. On the other hand, free nitrous acid was less than 0.2mg/l, and it was not inhibited oxidation of NO2--N.The effluent SO42--S concentration correlated with the decoloration rate (r=0.757), suggesting a relationship between sulfur oxidation and color removal.