Sludge Reduction Byozonation And Carbon Source Reuse

With the load of sewage increasing year by year in China and the activated sludgeprocess widely used, municipal wastewater treatment plants have seen excess sludgebecame a common challenge for sewage treatment. At the same time, carbon sourceshortage resulting from low strength wastewater has become another commen problemfaced by the municipal wastewater treatment plants in China. This essay attempted tosolve the two problems. Sudge reduction and carbon reuse achieved in the way thatozone oxidized escess sludge firstly and then ozonolysate of excess sludge retuned tobiological tank.This research analyzed influencing factor for ozonation process, the impact ofozone on the nature of the excess sludge, the optimum ozone dosage, the feasibilitystudy of ozonolysate as carbon source, and design and operation of OZONE-SBRcombined process focusing on evaluating sludge reduction effect and impact on effluentquality.According to the influencing factor experiment，the dominant factor for solubleCOD per SS is ozone dosageï¼›Ozone concentration is the second; Sludge concentrationis the least. Firstly ozone mainly oxidized the cellwall, and then the reaction of ozoneand ozonolysate became the domimate reaction. C, N, and other components increasedrapidly at early stage, but showed a slowdown growth or a decline in late stage. SCOD,TCOD, TN and NH₄-N all incresced rapidly when ozone dosage ranged from0.02to0.098gO3/gSS. TP presented a linear increase. The ozonolysate indicated goodbiodegradability as carbon source. Sludge settling performance improved significantly.Choosing only SCOD or both of protein and polysaccharides as evaluation indicatorsresulted in two optimum ozone dosage,0.080gO3/gSS and0.054gO3/gSS, respectively.The denitrificatin experiment showed that the denitrification rate of ozonolysate is4.52mgN/g SS·h^-1which could almost match that of glucose. The high denitrificationrate for ozonolysate indicated its good quality as a carbon source.The effluent quality, except TP, was not significantly affected by ozonation in theoperation of OZONE-SBR combined process. Though the pollutant removal rates underthe conditions of the two ozone dosage were slightly lower than that of the control,those still maintained high leval overall. The pollutant removal rates under the ozonedosage of0.080gO3/gSS were lower than that of0.054gO3/gSS. High consentration ofTP was the main problem for effluence quality. The consentration of TP were1.15and2.04mg/L, respectively, for the tow ozone dosages, both of which were exceededstandard B of the first class in discharge standard of pollutions for municipal wastewater treatment plant （GB18918-2002），which resulted in requirement forChemical phosphorus removal facilities. Under the ozone dosge of0.054gO3/gSScondition, SS and VSS reduction rates were36.5%and41.4%, respectively. Under theozone dosge of0.080gO3/gSS condition, SS and VSS reduction rates were64.5%and70.8%, respectively. Both results indicated that the sludge reduction effects wereobvious.