Assessment of simultaneous autotrophic–heterotrophic denitrification with high removal of nitrogen, sulfur and carbon: optimization through response surface methodology

BACKGROUND Some liquid industrial wastes are rich in sulfur (S), nitrogen (N) and organic matter, causing eutrophication of lakes and rivers. These wastes also are highly toxic to aquatic organisms and pose serious health problems. Biological N removal is performed by denitrification. Heterotrophic denitrifiers oxidize organic matter to CO 2 gas and reduce nitrate (NO 3 − ) to N 2 gas, whereas autotrophic denitrifiers oxidize reduced S compounds...