Mixotrophic denitrification and desulfurization for treatment of nitrate, nitrite, sulfide and organic carbon-contaminated wastewater

An expanded granular sludge bed packed with porous sponge was started to treat wastewater contaminated by sulfide, nitrate, nitrite and organic carbon compounds. In inflow wastewater, potassium nitrate and sodium nitrite acted as electron acceptors, sodium sulfide acted as electron donor and glucose acted as organic carbon source. In the anoxic reactor, autotrophic denitrification happened together with heterotrophic denitrification whose percent was 21.76%. The destruction for anoxic environment had larger impact on nitrate removal than nitrite removal. The enhancement of influent loading rates had also effect on contaminants removal, but its effect was less than that from anoxic environment destruction. The ratio of sulfate to removal sulfide was about 40%, considering abiotic oxidation. The influent concentrations of sulfide, nitrate, nitrite and organic carbon were 200mgS/L, 52.5mgN/L, 20mgN/L, 20mgC/L and corresponding conversion were 99%, 99%, 95.5% and 80% respectively, which actualized the simultaneous mixotrophic denitrification and desulfurization.