Effect of molybdenum and selenium addition on the denitrification of waste water

The involvement of molybdenum and selenium in enzyme systems responsible for dentrification has been cited by several investigators. In this investigation, a bench scale denitrification column was operated continuously at room temperature to study the effect of molybdenum, added singly or in combination with selenium, on nitrate reduction and COD utilization rates. Methanol was used as the sole source of carbon and electron donor. As expected both nitrate reduction and COD utilization rates increased significantly (P < 0.001) when molybdenum concentration in the feed reached 1.5 mg 1−1 and the observed increase was maximum when molybdenum concentration was raised to 2.5 mg 1−1. The rates could be increased further by incorporating 0.5 mg 1−1 selenium in combination with 2.5 mg 1−1 molybdenum. A possible biochemical interpretation of the observed stimulation is suggested.