Abstract
BOD5 is an index used for evaluation of water environment and purification function of wastewater treatment facilities. This value indicates bio-chemical oxygen demand consuming by organic matter. However, the BOD5 measurement is affected by oxygen demand of nitrification and BOD5 sometimes indicates an abnormal higher value compared with COD(Mn).
By examining the trend of DO, NOx-N in incubation bottles and analyzing the change of effluent water quality in wastewater treatment facilities, we obtained some results shown bellow.
1. The nitrification in incubation bottle occurred in initial 2 days for cultivation period of 5 days and observed exponential increase of nitrate.
2. The BOD5 values of effuents from wastewater treatment facilities often observed larger than the COD(Mn) value and sometimes take 3 times higher than COD(Mn) value.
3. The reaction rate of nitrification in incubation bottle was affected by NH3-N concentration. At the higher concentration of NH3-N in BOD5 measurement sample, the rate was in inverse proportion to NH3-N concentration. At the lower NH3-N concentration, however, it was in direct proportion to NH3-N concentration.
In case of being affected by nitrification in BOD5 measurement, it is difficult to evaluate effluent water quality and purification function of wastewater treatment facilities by effluent BOD5. So it is necessary to measure the values of ATU-BOD, NH3-N, NO2-N, NO3-N with BOD5 measurement for biological treatment effluents.
