NITROGEN REMOVAL FROM WASTE-WATER WITH HIGH AMMONIA NITROGEN CONCENTRATION VIA SHORTER NITRIFICATION AND DENITRIFICATION

Shorter nitrification is reached through Nitrobacter bacteria activity inhibition. Nitrobacter bacteria responsible for nitrite nitrogen oxi dation are sensitive to free ammonium. The presence of free ammonium d epended on a high ammonia nitrogen concentration in wastewater and its pH, It was the pH of the wastewater that was the decisive parameter i n Nitrobacter bacteria activity inhibition in stable temperatures and at stable ammonia nitrogen concentrations. Reaction control in the aer ation phase of the treatment process guaranteed the concentration of f ree ammonium within the 1 to 6 mg NH3/l range and at the same time con centration of free nitrous acid did not exceed 0.04 mg HNO2/l. It allo wed nitrification to be significantly shortened and to receive build-u p of nitrite nitrogen up to 300 mg NO2-N/l. Nitrification rate was abo ut 0.06 g N/g MLSS . d. Measured oxidation rates of particular groups of nitrifying bacteria as oxygen uptake rates by Nitrosomonas and Nitr obacter bacteria respectively made control of shorter nitrification ea sier and gave insight into the activity of both nitrifier groups. (C) 1997 IAWQ. Published by Elsevier Science Ltd.