Study On Aerobic Digestion Of Excess Sludge

As the growing of the quantity of wastewater treatment plant and the ability ofwasterwater treatment, excess sludge output was also increasing suddernly. So the problemsof sludge treatment and disposal were serious day by day. If sludge was not to be treatedproperly, it could cause serious consequence. Therefore, people had adopted many methods totreat sludge and aerobic digestion of excess sludge was a common method among them. Butlong period and large amount of energy consumption of aerobic digestion restrained itsapplication range. Physical treatment and chemical treatment used for sludge was an effectivemethod.Aerobic digestion with Fenton’s reagent, aerobic/anoxic digestion with Fenton’s reagentand aerobic digestion with UV/Fenton’s reagent was adopted for sludge treatment by thisarticle, and characteristics of sludge are investigated meanwhile.Results showed that reduction rate of SS and VSS with Fenton’s reagent (m (Fe²⁺):m（H2O2）=1:4)2.0g/L（sludge） and3.0g/L（sludge） per day could respectively improve from32.2%,38.1%of control experiment to37.4%,43.2%and40.2%,47.7%after15days’digestion by adopting method of aerobic digestion with Fenton’s reagent. The more dosingquantity of Fenton’s reagent was added, the better sludge treatment effect had. The massconcentration of COD in the supernatant improved20%and40%respectively. The massconcentration of total phosphorus in the supernatant improved39.4%and74%respectively.The mass concentration of ammonia nitrogen in the supernatant improved15.9%and34%.After Fenton’s reagent added, pH of sludge decreased obviously. Fenton’s reagent oxidizationcould make dehydration capacity of sludge increasing obviously that improved72.9%and86%compared with contrast experiment.The reduction rate of VSS and SS improved by Fenton’s reagent (m (Fe²⁺): m （H2O2）=1:4)3.0g/L （sludge） per day afer15days’digestion （12hours’ aerobic digestion,12hours’anoxic digestion per day） adopting method of aerobic/anoxic digestion with Fenton’s reagent.The reduction rate of SS and VSS respectively improved from30%to35%and36.1%to42%. The mass concentration of COD and total phosphorus in the supernatant respcectivelyimproved50%and33.6%. Because of existing denitrification, the mass concentration ofammonia nitrogen in the supernatant was below13mg/L in the period of aerobic/anoxicdigestion without any oxidizing agent, and it rised slowly after Fenton’s reagent added. In theperiod of aerobic/anoxic digestion without any oxidizing agent, pH of sludge was between7,but it decreased to4.9after Fenton’s reagent added. The dehydration capacity of sludgeimproved88.6%compared with contrast experiment adopting Fenton’s reagent oxidization.The reduction rate of VSS and SS improved by Fenton’s reagent (m (Fe²⁺): m （H2O2）=1:4)3.0g/L （sludge） and24hours’ UV illumination per day afer15days’digestion. Thereduction of SS and VSS respectively improved from35.5%to45.4%and41.4%to51.2%.The mass concentration of COD, total phosphorus and ammonia nitrogen in the supernatantrespcectively improved33.3%,110.3%and37.9%. The pH of sludge decreased to1.5. Thedehydration capacity of sludge improved90%.