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Abstract: Underground brine waste containing high concentrations of ammonium and with a salinity of 3% is usually generated during the production of methane gas and iodine in the gas field of Chiba Prefecture, Japan. In this study, one swim-bed reactor, packed with a novel acrylic fiber biomass carrier (Biofringe), was applied to the partial nitritation treatment of this kind of underground brine waste. A stable nitrite production rate of 1.6 kg NO2-N m−3 d−1 was obtained under a nitrogen loading rate of 3.0 kg-N m−3 d−1, at a pH of 7.5 and a temperature of 25 °C. Nitrate production was negligible and the effluent NO2-N/NO x -N ratio was above 98% due to the successful inhibition of nitrite-oxidizing bacterial activity. Free ammonia was considered to be the main factor for inhibiting the activity of nitrite-oxidizing bacteria. A microbial community shift was demonstrated by 16S rRNA analysis, and it was shown that the ammonium-oxidizing bacteria became the predominant species after successful nitrite accumulation was observed. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]