Experimental Study On Advanced Treatment Of Refractory Organic Wastewater By Persulfate Advanced Oxidation-BAF

China's urban industrialization is still in the period of rapid development.Water pollution has shown an increasing trend."Water Pollution Control Action Plan" promulgated by the State Council has comprehensively controlled the discharge of pollutants,especially the industrial pollution prevention and control,as well as the special remediation of the ten key industries.In particular,the refractory organic wastewater treatmentof these industries is a key and important point.The traditional wastewater treatment technology has been impossible to meet the increasingly high emission requirements.It is an important research topicto explore efficient treatment of refractory organic wastewater process.In this paper,the advanced treatment process of persulfate advanced oxidation-Biological aerated filter(BAF)is carried out to achieve the stable discharge of refractory organic wastewater.Firstly,Fe and Ni metal ions were supported on the powdered activated carbon(PAC)by chemical coprecipitation method and high temperature calcination method.The catalyst was prepared to activate sodium persulfateefficiently,and then the catalyst was characterized.Secondly,based on the formation of catalyst and sodium persulfate oxidation system simulated dye wastewater treatment.The chemical oxygen demand(COD)removal rate as an evaluation index,and the process parameters of catalyst dosage of sodium persulfate,sodium persulfate dosage,reaction p H value and reaction time were used to study the factors that affect COD removal rate.The results were optimized by response surface methodology,and the degradation mechanism was discussed.Using the basalt fiber cotton and PP hollow spheres as raw materials make the aerated biological filter filler.This paper taking the actual chemical wastewater as the treatment object to study the characteristics of biofilm formation and microbial community structure.In this paper,the effects of HRT,DO and p H on the efficiency of BAF process were studied emphatically.The process parameters of BAF were optimized by response surface method.Finally,taking the actual dyeing wastewater as the object,this paper investigated advanced treatment efficiency of persulfate advanced oxidation-BAF process.The main conclusions are as follows:1)The optimum conditions for the preparation of sodium persulfate catalyst are Fe3+ +Fe2+:Ni(molar ratio)4:1,Fe3O4:PAC(mass ratio)is 1:4,calcination temperature is 700 ?,calcination time is 4 h.The catalysts were characterized by SEM,TEM,XRD and EDS,which indicated that the voids on the surface of the catalyst were increased and showed hollow structure.The surface contains C,O,Fe and Ni.The surface active substances were magnetic in the form of nickel ferrite,and were conducive to recycling.2)Catalyst and sodium persulfate were used to treat dye wastewater treatment which was simulated by the methyl orange.The reaction time is 2 h,the p H value of the wastewater changes within the range of 3 to 11,the catalyst exhibits excellent catalytic performance,and the degradation efficiency increased with the increase of p H value.The degradation rate of COD was the lowest 75.93%.Under the neutral condition,the catalyst was reused 6 times and the catalytic efficiency was still over 70%.GC-MS analysis showed that the methyl orange dye molecules were oxidized totally in the oxidation system,most of the products were the p-benzoquinone,and a small part of the products were the chain-like organic molecules,such as 2-cyclopentenone,2-dichlorocyclopentene and so on.The process of oxidation of organic pollutants was the first adsorption of pollutants on the surface,and then organic mattesr were broke down into small molecules by oxidation.The binary polynomial regression equation for the treatment of methyl orange simulated dye wastewater with the catalyst and sodium persulfate oxidation system was obtained by the response surface method:?=82.96+4.07X1+3.99X2+1.97X3+1.44X1X2-1.95X1X3+0.98X2X3-0.92X12-5.14X22-4.69X32(In this formula,? is the predicted COD removal rate,X1,X2,X3 are p H,catalyst dosage,sodium persulfate dosage,respectively).When X1,X2 and X3 were 11,4.1 and 10.3,respectively,the COD removal rate was 87.55% that was highest,and the best results were 0.88% compared with the actual results.3)BAF process to the actual chemical waste water as the object of treatment,by inoculation linked to the membrane method to start film.BAF process has the best hydraulic retention time of 8 h,the best influent p H is 7,the best DO range is 3~4 mg/L.Under the optimum conditions,COD,NH3-N and TP removal rates were stable at 80%,85% and 87.5%,respectively.In the early stage of the membrane,the microbial community in the biofilm was single,mostly nematode and paramecium.Domestication in the late,began to appear insects,tired insects,rosewood,a variety of rotifers,oligomers and other biodiversity is very rich.Microbial diversity analysis of mature biofilms showed that the microbial species in the biofilm were abundant,The types of microbial species in nitrogen and phosphorus removal are mainly Pseudomonas,Desulfomicrobium,Thauera,Derie,Rhodobacte.The binary polynomial regression equation for COD,NH3-N and TP removal rates of aeration biofilter system was obtained by response surface method:?1=85.0+1.93X1+4.26X2+11.81X3-0.48X1X2-0.68X1X3-2.95X2X3-8.26X12-9.99X22-8.53X32?2=85.6+2.1X1+1.33X2+17.18X3-0.1X1X2-0.6X1X3-0.05X2X3-14.52X12-20.11X22-12.52X32?3=85.5+3.73X1+2.43X2+13.55X3-0.60X1X2-0.30X2X3-17.31X12-13.56X22-6.71X32;(In this formula,?1,?2,?3 are predicted COD,NH3-N,TP removal rate,X1,X2,X3 were p H,DO,HRT values).The removal rates of COD,NH3-N and TP were 89.20%,91.57% and 92.23%,respectively,when X1 = 7.17,X2 = 3.13 and X3 = 11.06.4)The COD concentration of the actual printing and dyeing wastewater was 835~1125mg/L,the concentration of NH3-N was 16.35~22.24 mg/L,and the effluent COD was below 40 mg/L,the effluent NH3-Nwas below 2 mg/L,effluent quality in line with "Discharge standard of water pollutant for dyeing and finishing oftextile industry" limit.The peroxylate advanced oxidation-BAF combination process is simple to construct,and has a wide applicability in the treatment of refractory organic wastewater.The effluent quality meets the corresponding pollution control standard.This study provides technical support for the application of the combined process in the field of refractory organic wastewater treatment.