Behavior of Nitrite Oxidizers in the Nitrification/Denitrification Process for the Treatment of Simulated Coke-Oven Wastewater

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The behavior of nitrite oxidizers in the nitrification/denitrification process for the treatment of coak-oven wastewater was studied by using molecular methods. An activated sludge process was operated with simulated coak-oven wastewater. In the existence of thiosulfate, partial nitrification was observed, while in its absence, full nitrification was observed. In the activated sludge treating simulated coak-oven wastewater, only Nitrobacter species were found as the nitrite oxidizers by using PCR and FISH targeted at different nitrite oxidizers. The QP-PCR (quenching primer PCR) method was applied for the quantitative monitoring of Nitrobacter species. The QP-PCR method demonstrated that Nitrobacter species increased when thiosulfate was absent. Nitrobacter species was found to have been the major nitrite oxidizing species at least in one of the operational periods with full nitrification. On the other hand, in another period with full nitrification, their absolute amount was too small to explain nitrite oxidation.