Study On Sedimentation Performance Of Activated Sludge, The Rule Of Microbe Multiplication And Low Concentration Municipal Wastewater Treatment In A-step Of AB Process

The present research situation about AB process in and out of our country was analyzed in this paper. In addition to a concentrated study of the factors affecting sedimentation performance of A-step activated sludge, the rule of microbe multiplication, yield of activated sludge in A-step and treatment of low-concentration sewage were also involved in this paper. The main conclusions are as follows:(1) The study on factors affecting sedimentation performance of A-step activated sludge shown that the inflow SS distinctly improve sedimentation performance of activated sludge, the less influent SS makes the sludge bulking easy, and the pythogenous sewage evidently worsen sedimentation performance of activated sludge. The experimental results indicated as well that canceling primary sedimentation tank and cesspool when building houses would avail to stable running of sewage treatment plant. When loading rate Ns is 0.3～4.0 kgBOD5/kgMLSS·d in A-step , the sedimentation performance of A-step activated sludge do not change much, especially when Ns is 0.5～1.5 kgBOD5/kgMLSS·d (bulking Ns), the sludge bulking does not take place; the less or much oxygen does not result in sludge bulking. Besides, the bulking sludge will resume soon to the order when the process running in A-step mode.(2) The alive bacterium number and rule of its multiplication were studied by determining the change of its dehydrogenase. The results shown that the growth velocity ratio of A-step bacteria is between 0.05921 and 0.08742h-1, and its generation period is between 11.7h and 7.9 h.(3) The study on increase of A-step retential sludge indicated: the alive bacterium number of A-step activated sludge is obvious large, but the quality proportion of alive bacterium is quite small and it occupies 4.03％～12.46％. The share resulted from bacteria multiplication of A-step retential sludge is 3.44％～11.0％; the share resulted from influent SS is 96.56％～89.0％. This is the real cause that A-step sludge yield is large. The mode of A-step retential sludge yield is deduced in the paper:S=[0.037(CODinflow－CODoutflow)+0.88(SSinflow －SSoutflow)]×Q(4) The study indicated that a good treatment effect would be acquired by using A-step only to treat low concentration municipal wastewater. When influent COD 170～288 mg/l, BOD5 67～137mg/l,SS 60～189mg/l,HRT 75～25min,and NS 0.38～3.11 kgBOD5/kgMLSS·d,the effluent COD,BOD5 and SS would achieved therequirement of level 1 of national wastewater discharge standard entirelyThe study will benefit stable running of wasterwater treatment plant and development of AB process.