| The pharmaceutical wastewater has many characteristics,such as toxic substances,biodegradability and degradation,which can cause serious environmental harm.In this study 3-methylindole,indole and benzothiazole were selected as the characteristic pollutants,and the concentrations were set at 90mg/L and 60mg/L respectively.The two characteristic pollutants in wastewater has high concentration in waster water,they are not only seriously toxic,but also degrade the efficiency of wastewater degradation.The degradation of characteristic pollutants is the technical difficulty of biodegradation of pharmaceutical wastewater.The removal efficiency of pollutants by conventional biological methods is not high,but the cost of advanced oxidation and electro assisted biological methods too high for practice operation.Considering the biological method of acclimated activated sludge,the characteristic pollutant was degraded by the method of glucose co-substrate domestication,PACT process was applied to strengthen microbial flora to improve treatment efficiency and load resistance.The 3-methylindole degrading bacteria acclimated by glucose co metabolism method can completely degrade 3-indole and its degradation products.At the end of domestication,3-methylindole was completely degraded after aeration of 3 hours,and after aeration of 4h,the removal rate of COD was 76.1%,and the removal rate of TOC was 87%.After domestication,the 3-methyl indole degrading bacteria flora is distributed in diversity,and the predominant flora is prominent,such as acidovorax(35.64%),acinetobacter(5.26%).The literature shows that they can degrade recalcitrant organic compounds,so it is supposed that they also have the ability to degrade 3-methylindole.The biodegradation of benzothiazole can be efficiently degraded by the degrading microorganisms,but the degradation efficiency of the metabolites is not high.Therefore,the PACT process is used to strengthen.The PACT process parameters are determined as follows: the optimum dosage of PAC is 60mg/L,and the hydraulic retention time is 7h.After the optimum dosage of PAC was added,the removal efficiency of TOC and COD was greatly enhanced by the degrading microorganisms of benzothiazole,and the metabolites of benzothiazole could be degraded efficiently.The biological activity of bacteria was increased,the oxygen consumption rate,respiration rate and polysaccharide and protein in EPS increased.The PACT enhanced sludge system operates well under load impact.The TOC removal rate of the PACT enhanced sludge system was significantly higher than that of the sludge system without PAC.Experiments show that adding PAC is the necessary measure to ensure the normal operation of sludge system under load impact.After domestication and PACT intensification,the structure of benzothiazole degrading bacteria was changed remarkably,After domestication and PACT intensification,the structure of benzothiazole degrading bacteria are Paludibacter(10.19%),Zoogloea(8.44%).The analysis showed that PAC and activated sludge interact as the synergistic effect.PAC adsorption of microorganisms and dissolved oxygen provides a good place for microbial habitat and metabolism and improves biomass;The PAC adsorption and desorption effect reduced the toxicity of benzothiazole to microorganisms,and promoted the respiration of sludge microorganisms.Adding PAC changed the micro environment of microbial growth,and activated sludge enclosed PAC,which formed a relatively anaerobic environment,thus a large number of non aerobic bacteria,such as Paludibacter degrading heterocyclic compounds,are formed,and a group of microorganisms with high biodegradability can be degraded.The mechanism of PACT promoting degradation of benzothiazole was investigated,It was found that the degradation of benzothiazole was first converted to 2-hydroxy benzothiazole(OBT),then continue to degrade through 2 paths: the first path is the ring opening reaction of benzene ring,the second path is a ring opening reaction of heterocyclic rings. |
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