| At present,the domestic sewage and industrial waste water of our country is commonly treated by activated sludge process.But it can produce a large number of surplus sludge,which is restricting the development of the city.So it is very importment for us to study on the sludge reduction and how to produce less sludge,even not produce sludge in the wastewater treatment process.The main components of sludge which is produced in the wastedwater treatment process are bacteria and other organisms.The bacteria is like an egg, the cell wall of the bacteria is as hard as the egg shell and the organic matter is as nutritious as the yolk of the egg.Because of the protection of the bacterial cell wall, the rich organic matter in the bacteria cannot be utilized by microorganisms in the activated sludge.The technology of biological cell lysis is a method which use the physical,chemical and other technology to destroy the bacteria and other organisms in the sludge,so that the organic matter within the cells(protein,polysaccharide,nucleic and so on) released into the liquid phase of the sludge.Then,let organic matter return to the aeration tank and they can be used by the organisms in the activated sludge again,so that the sludge is produced less and less in the wastewater treatment process.In this paper, the returned sludge from the secondary sedimentation tank in the petrochemical wastewater treatment plant was studied,a part of the sludge from the secondary sedimentation tank returned to the aeration tank to supply microorganism and another part was carried to for landfill. The main componts of the residual sludge were bacterica and other organisms, but the cell wall of bacterica and other cells of the organism was a stable semi rigid structure and it was a very difficult biodegradable material.In addition, there were many extracellular polymers around the cell wall, which had strong protective effect on the bacterial cells. In this paper,advanced oxidation process was used to destroy the microbial cells in order to make the organic substance release into the sludge liquid phase.So that we could change the particulate, difficult biodegradable COD into a low molecule, easily biodegradable COD.In this paper,Fenton,sodium hypochlorite and ozone oxidation were used to destroy the microbial cells of the sludge from the secondary sedimentation tank in the petrochemical wastewater treatment plant in order to observe and study the reaction influence factors and the effect of the oxidative cracking,and make the effect the best.The purpose of experiment was to provide basic data for the following research and industrial application.And the main conclusions are as follows:(1) The rerurned sludge from the secondary sedimentation tank in the petrochemical wastewater treatment plant was disintegrated by Fenton oxidation and the change of soluble chemical oxygen demand(SCOD) 、polysaccharide、 suspended solids(MLSS) and volatile suspended solids(MLVSS) were showed the effect of sludge disintegration by Fenton oxidation. The effect of the pH value of sludge、 reaction temperature 、reaction time 、the dosage of Fe2+ and the dosage of H2O2 on the sludge disintegrated by Fenton oxidation were investigated.And we optimized the process and analyzed the change of the properties of the sludge after oxidation by Fenton. The main conclusions were as follows:the sludge was disintegrated by Fenton oxidation,and the effect of oxidation contions on sludge disintegration was investigated. The results showed that the optimum conditions were the pH value of sludge 2.5,reaction temperature 40 ℃,reaction time 90 min,the dosage of Fe2+(mass concentration in sludge) o.4g/L,the dosage of H2O2(mass concentration in sludge) 10.0g/L.Under these conditions, the mass concentration of soluble chemical oxygen demand(SCOD) and polysaccharide in the sludge increased from 56.88,9.33mg/L to 1183.06,403.85mg/L,respectively,and the mass concentrations of suspended solids(MLSS) and volatile suspended solids(MLVSS) decreased from 7657.00,5905.00 mg/L to 4906.00,2675.00mg/L,respectively,the sludge reduction rate was35.9%,Sludge settlement ratio of 30min(V30min) decreased from 95% to 43%,the specific resistance to fitration(SRF) decreased from 1.12×1010 s2/g to 1.28×109 s2/g,the average particle size of sludge particles decreased from 131.98 um to 58.78 um.The microbial cells of the sludge could be cracked effectively by sodium hypochlorite oxidation.And the dehydration and the sedimentation could be improved after Fenton oxidation.(2) The rerurned sludge from the secondary sedimentation tank in the petrochemical wastewater treatment plant was disintegrated by sodium hypochlorite oxidation and the change of soluble chemical oxygen demand(SCOD) 、polysaccharide、 suspended solids(MLSS) and volatile suspended solids(MLVSS) were showed the effect of sludge disintegration by sodium hypochlorite oxidation. The effect of the pH value of sludge、 reaction temperature 、reaction time and the dosage of sodium hypochlorite on the sludge disintegrated by sodium hypochlorite oxidation were investigated.And we optimized the process and analyzed the change of the properties of the sludge after oxidation by sodium hypochlorite. The main conclusions were as follows: the sludge was disintegrated by sodium hypochlorite oxidation,and the effect of oxidation contions on sludge disintegration was investigated. The results showed that the optimum conditions were the initial pH value of sludge 7.68,reaction temperature 30 ℃,reaction time 40 min,the dosage of sodium hypochlorite(mass concentration in sludge) 11.5g/L.Under these conditions, the mass concentration of soluble chemical oxygen demand(SCOD) and polysaccharide in the sludge increased from 56.88,9.23mg/L to 4143.79,750.77mg/L,respectively,and the mass concentrations of suspended solids(MLSS) and volatile suspended solids(MLVSS) decreased from 7657.00,5905.00 mg/L to 4716.00,2413.00mg/L,respectively,the sludge reduction rate was38.4%,the average particle size of sludge particles decreased from 131.98 um to 38.99.The microbial cells of the sludge could be cracked effectively by sodium hypochlorite oxidation.(3) The rerurned sludge from the secondary sedimentation tank in the petrochemical wastewater treatment plant was disintegrated by ozone oxidation and the change of soluble chemical oxygen demand(SCOD) 、polysaccharide、 suspended solids(MLSS) and volatile suspended solids(MLVSS) were showed the effect of sludge disintegration by ozone oxidation. The effect of the pH value of sludge、 reaction time and the dosage of H2O2 on the sludge disintegrated by ozone oxidation were investigated.And we optimized the process and analyzed the change of the properties of the sludge after oxidation by ozone. The main conclusions were as follows:the sludge was disintegrated by ozone oxidation,and the effect of oxidation contions on sludge disintegration was investigated. The results showed that the optimum conditions were the initial pH value of sludge 7.68,ozone concentration 30mg/L,the intake air flow 2.5L/min,reaction time 25 min.Under these conditions, the mass concentration of soluble chemical oxygen demand(SCOD) and polysaccharide in the sludge increased from 56.88,9.33mg/L to 1309.21,300.77mg/L,respectively,and the mass concentrations of suspended solids(MLSS) and volatile suspended solids(MLVSS) decreased from 7657.00,5905.00 mg/L to 4508.00,2312.00mg/L,respectively,the sludge reduction rate was 41.13%,the average particle size of sludge particles decreased from 131.98 um to 39.82.The microbial cells of the sludge could be cracked effectively ozone oxidation. |
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