NITRIFICATION OF AMMONIA-NITROGEN IN REFINERY WASTE-WATER

Wastewater from integrated petroleum refineries normally contains 20-80 mg/l ammonia-nitrogen which is harmful to the fishes in the receiving water bodies. To remove ammonia-nitrogen completely in the biotreatment system of refinery wastewater, various enrichment and cultivation methods of nitrifying bacteria were tried. Results indicated that by supplementing glucose nutrient, over 90% ammonia-nitrogen in the refinery wastewater could be converted into nitrite within 7-14 days in either an activated sludge or rotating biological contactor system. Trace nitrate was detected. Further addition of yeast powder to the treatment systems stimulated the growth of Nitrobacter which accelerated the oxidation of nitrite to nitrate. Complete oxidation of the influent ammonia-nitrogen was observed 7 days later after adding 5 mg/l yeast powder to the influent wastewater. It also showed that neither glucose nor yeast powder were required for sustaining ammonia nitrification after the augmentation of Nitrobacter was achieved.