Characteristics of Activated Sludge Treatment at High DO Level

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  • Matsuzaki Harumi
    Hitachi Research Laboratory, Hitachi Ltd.
  • Takahashi Sankichi
    Hitachi Research Laboratory, Hitachi Ltd.
  • Zhu Hong Li
    Hitachi Research Laboratory, Hitachi Ltd. Shanghai Inst. of Env ironmental Protection the People's Republic of China.
  • Oguri Yoshitaka
    Hitachi Research Laboratory, Hitachi Ltd. Hitachi Plant Engineering & Construction Co., Ltd. Research Laboratory

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Other Title
  • 高溶存酸素レベルにおける活性汚泥処理特性
  • コウ ヨウゾン サンカ レベル ニ オケル カッセイ オデイ ショリ トクセイ

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Effects of environmental factors (DO level, MLSS conc., etc.) on the kinetics of activated sludge have been studied by using a shaft-type aeration tank of 10m depth.<BR>It was clarified that specific oxygen consumption rate, γ, is constant when DO level is greater than the critical DO and decreases when DO level is less than the critical DO. The critical DO, which has different values according to the dominant process in activated sludge, is 1.1-1.35mg/l in oxidation reaction and is 0.65-0.9mg/l in growth reaction. SVI is constant when DO level is greater than the critical DO and increases when it is less than the critical DO. When MLSS and retention time, TR, are constant, γ is proportional to specific COD removal rate, β. Dominant process in activated sludge varies with variation of MLSS or TR. Oxidation proceeds mainly when MLSS×TR is greater than 17000h·mg/l and DO level is greater than 4.5mg/l. Groth reaction dominates when MLSS ×TR is less than 10000 h·mg/l.<BR>It is shown that βc with only a bacterium is greater than βc in mixture phase microorganism.

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