Development on High Rate Treatment Process of Upflow Anaerobic Sludge Blanket (UASB) Reactor.

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The technical feasibility of treatment of low strength wastewater by upflow anaerobic sludge blanket(UASB)reactor was experimentally investigated using an actual domestic wastewater and industrial wastewater of starch manufacturing factory. The results obtained from continuous flow experiment at treatment of an industrial wastewater are as followings :l. It is possible to operate the reactor at high COD_<cr> loading rate, 25kg/m^3. d at the temperature around 35 ﾟC.2. The removal efficiencies of soluble COD_<cr> and BOD (based on influent total COD_<cr>, BOD and effluent soluble COD_<cr>, BOD) both achieved to be 90%.3. Total COD_<cr> removal efficiency (based on influent total COD_<cr> and effluet total COD_<cr>) decreased with increasing of COD_<cr> loading rate.Also, SS removal rate decreased from 50% (COD_<cr> loading rate : 2.5kg/m^3. d) to 17% (COD_<cr> loading rate : 22kg/m^3d).The results obtained using a domestic wastewater at a HRT of 4.7 hrs in the temperature range of 25 to 13ﾟC are as follows. The removal efficiency of total COD_<cr>, solid COD_<cr> and BOD achieved to be 70%, 80% and 85%, respectively.The removal rates of total COD and soluble COD depend on the influent strength, but not on the temperature. On the other hand, the particulate organic matters in the influent were effectively removed by entrapment into the sludge bed. The hydrolysis rate of the entrapped organics within bed was significantly affected by temperature, that is, 58% of the entrapped particulate organics was liquefied at 25ﾟC, whereas only 33% at 13ﾟC.Furthermore, observation of morphological structure of the sludge fed on the domestic wastewater by scanning electron microscopy revealed that the granules had a tendency to be partly cracked and to be in a state of autolysis, even though remaining granular forms as a whole. It is necessary to maintain UASB reactor at the temperature above 20ﾟC for treatment of low strength wastewater.