Dynamics of Accumulation of Nitrite Nitrogen during Denitrification in SBR at Low Temperature

Under the strictly-controlled experimental conditions,the accumulation of nitrogen during the denitrification of actual landfill leachate which was pre-treated by anoxic/anaerobic up-flow anaerobic sludge bed(UASB) was investigated in a lab-scale sequencing batch reactor(SBR) at low water temperatures.The experimental results show that at four different initial NO-3-N concentrations of 64.9,54.8,49.3 and 29.5 mg/L,an obvious accumulation of nitrogen is achieved in SBR under the conditions of lower water temperature of 13.5 to 15.5 ℃.The maximum accumulation concentrations are 37.8,21.5,25.2 and 18.9 mg/L respectively.During the accumulation of nitrogen,two break points of knee and nitrite knee on the oxidation reduction potential(ORP) profile indicate that the nitrate reduction reaction and reduction reaction are completed,respectively.For the denitrification with obvious accumulation of nitrogen,it is not accurate that nitrate nitrogen is only used as the sole parameter of the denitrificaion rate.The nitrate nitrogen plus nitrogen should be used.It should be named as nominal denitrificaion rate when nitrate nitrogen is used as the only utilizable substrate.