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High-rate partial nitrification performance of high ammonium containing wastewater under low temperatures

Qiao, Sen, Matsumoto, Noriko, Shinohara, Takehiko, Nishiyama, Takashi, Fujii, Takao, Bhatti, Zafar, Furukawa, Kenji
Bioresource technology 2010 v.101 no.1 pp. 111-117
bacteria, effluents, electrons, fermentation, fluorescence in situ hybridization, magnesium ammonium phosphate, methane, nitrification, nitrites, oxidation, pH, particle size, sludge, temperature, wastewater
In this study, a swim-bed reactor was used for partial nitrification treatment of magnesium ammonium phosphate precipitation process treated effluent of methane fermentation digester liquor. Even without temperature, DO, and pH control, the maximum nitrite production rate of 2.66kg NO₂-N/m³/d was achieved under a nitrogen loading rate of 5.45kgN/m³/d at 18°C and a nitrite production rate of 0.22kg NO₂-N/m³/d was still attained at a nitrogen loading rate of 0.48kgN/m³/d even the operational temperature decreased to 8°C. The average effluent NO₂-N/(NO₂ +NO₃-N) ratio reached 95.4% during the entire experimental period. The mean particle size of suspended sludge increased from 260 to 450μm and the microscopic observation confirmed the formation of dense-flocs. The results indicated that there were two regimes for ammonium oxidation, one at 20-30°C and the other at 10-20°C. Scanning electron microscopic observation and FISH analysis demonstrated that ammonium-oxidizing bacteria were the dominant microorganisms and were considered to be responsible for the satisfactory partial nitrification performance.