Effect of varying salinity, temperature, ammonia and nitrous acid concentrations on nitrification of saline wastewater in fixed-bed reactors.

Nitrification under changing salinities (0-9%), temperatures (6-50°C), ammonia (0-5 g NL(-1)) and nitrite concentrations (0-0.4 g NL(-1)) was investigated in fixed-bed reactors. For all conditions ammonia oxidation rates (AOR) were lower than nitrite oxidation rates (NOR). AORs and NORs increased from 12.5 to 40°C and were very low at 6°C and almost zero at 50°C. No recovery of nitrification was obtained after incubation at 50°C, whereas nitrification was restorable after incubation at 6°C. Ammonia concentrations of 5 g NL(-1) or nitrite concentrations up to 0.125 g NL(-1) decreased AOR to almost zero. AORs and NORs recovered if ammonia or nitrite was removed. At concentrations of 1 and 5 g NL(-1) ammonia AOR and NOR were inhibited by 50%, whereas 27 mg N/L nitrite inhibited AOR by 50%.