Study On Reducing Of Activated Sludge By Method Of Low Concentration Ozone And Biochemistry In Experiment

Today, disposal establishment of sewage is popular; its disposal rate is improved and its disposal degree is deepened. Along with these developments, the yield of sludge in sewage plant will increase greatly, and problems of secondary pollution comes with that can not be ignored. Now, international study adopts physics and chemic measure, for examples, heat treatment and ultrasonic, to decrease the yield of sludge. This paper discusses application of low concentration ozone-biological measure in the treatment of waste activated sludge.Results of experiment show that the decrease effect of sludge is mainly relate to the concentration and time of reaction when activated sludge goes along ozone-biological reaction of low concentration (=0.010mgO3/mgMLSS). In oxidation of sludge and entire ozone-biological treatment process, the oxidation removal rate and total removal rate increase along with increase of ozone concentration and reaction time. The oxidation removal rate of sludge and reaction concentration of ozone accord direct ratio, and its reaction general form is E_MLSS(%) = AC_O3 + B(C_O3∈[0-0.001]). The oxidation removal rate of sludge and natural logarithm of reaction time accord direct ratio, and its reaction general form is E_MLSS(%) = ALn(t) + B(t∈[0-60min]). The total removal rate of sludge shows direct ratio relation to reaction concentration of ozone and natural logarithm of reaction time, its reaction general form is E _总(%) = ALn(X) + B (X)(X shows reaction concentration of ozone and reaction time). When reaction time is 60 minutes and reaction concentration of ozone is 0.010mgO₃/mgMLSS, the total removal rate of sludge reaches 77.73%. In the process of oxidation of sludge by low concentration ozone, reaction of ozone and microorganism destroy the wall of cell and release cytoplasm, meanwhile water-fast big molecule are decomposed to soluble small molecule segment, which manifests the value of SCOD increase in mix liquid of sludge and water. At different reaction time, when reaction concentration of ozone is about 0.005 mgO₃/mgMLSS, increase quantity of SCOD in sludge is maximum, which shows cytoplasm which is released and small molecule segment which is decomposed will be oxidation continually by ozone.By disposal with low concentration ozone—biological measure, sludge yield decrease meanwhile COD in effluent of biochemistry reactor is lower than 60mg/L that is ordained with Integrated wastewater discharge standard(GB8976-1996).