| Title |
Abnormal Behavior of Ordinary Heterotrophic Organism Active Biomass at Different Substrate/Microorganisms Ratios in Batch Test |
| Authors |
이병준 ( Byung Joon Lee ) ; 민경석 ( Kyung Sok Min ) ; ( M. C. Wentzel ) ; ( G. A. Ekama ) |
| Keywords |
Batch test; So/Xo ratio; Maximum specific growth rate; Competition; Inhibition |
| Abstract |
Batch test methods have developed for a long time to measure kinetic and stoichiometric parameters which are required to perform steady state design and mathematical modelling of activated sludge processes. However, at various So/Xo ratios, abnormal behaviors of ordinary heterotrophic organism in batch tests have been reported in many researches. Thus, in this research, abnormal behaviors of heterotrophs in batch tests were investigated at various So/Xo conditions by measuring and interpreting oxygen utilization rate. As So/Xo ratio increased, the calculated values of maximum specific growth rates, μ_(H.max) and K_(MP.max), increased. However, at a certain point of So/Xo (around 10㎎COD/㎎MLAVSS), μ_(H.max) and K_(MP.max). values started to decrease. According to this observation, three prominent behaviours of heterotrophs were identified at various So/Xo conditions. (1) At low So/Xo region (below 5 ㎎COD/㎎MLAVSS), the oxygen utilization rate of heterotrophs in batch tests were almost stable and consequently yielded lower maximum specific growth rate. (2) At high So/Xo region (up to 5~10 ㎎COD/㎎MLAVSS), oxygen utilization rate incresed sharply with time and indicated more upward curvature than the predicted OUR with conventional activated sludge model, which consists of single hetetrotrophs group. Thus, in this region, competition model of two organisms, fast-grower and slow-grower, seemed to be appropriate. (3) At extremely high So/Xo region (over 10㎎COD/㎎MLAVSS), significant oxygen utilization rate was still observed even after depletion of readily biodegradable COD. This might be caused by retarded utilization of intermediates which were generated by self inhibition mechanism in the process of RBCOD uptake. |