Study On The Degradation Of PNP By SBR And Biological Contact Oxidation Process

P-nitrophenol(PNP)is toxic and has a great harm to the ecological environment and organisms.The biological method is widely used in the degradation of phenol wastewater because of its wide range of effects,low secondary pollution,and low cost.It is of great significance to study the performance of biological methods to degrade PNP wastewater.In this experiment,the sequential batch activated sludge method(SBR)and biological contact oxidation process were used to treat PNP wastewater.The main conclusions obtained are as follows:(1)The effects of four factors,hydraulic retention time,initial PNP concentration,initial pH and aeration,on the degradation of PNP wastewater by SBR and biological contact oxidation process were explored,and their respective optimal experimental conditions were obtained..The best experimental conditions for SBR treatment of PNP wastewater are:hydraulic retention time 6 h,initial PNP concentration 40 mg/L,initial pH=7,aeration 800L/m~3·min.Under this experimental condition,PNP in wastewater The degradation rate reached98.7%,COD removal rate was 97.3%,BOD5 removal rate was 89.5%,and ammonia nitrogen removal rate was 94.9%.The best experimental conditions for the treatment of PNP wastewater with biological contact oxidation process are:hydraulic retention time 12 h,initial PNP concentration 20 mg/L,initial pH=7,aeration 1600 L/m~3·min.In this experimental condition The degradation rate of PNP reached 93.7%,COD removal rate was 90.3%,BOD5 removal rate was 82.5%,and ammonia nitrogen removal rate was 91.2%.(2)Under the best experimental conditions,the kinetic equations of PNP wastewater degr adation were fitted and analyzed.The results showed that the degradation of PNP wastewater by SBR and biological contact oxidation process all accorded with the first-order kinetic equat ion.The fitting equation of SBR degradation PNP wastewater is y=0.8416x-1.0839,R~2=0.9612;the fitting equation of biological contact oxidation process degradation PNP wastewater i s y=0.2705x-0.5649,R~2=0.9511.(3)The microbial communities in activated sludge and biofilm were analyzed by high-thr oughput sequencing technology.The study found that when the concentration of PNP wastew ater was 20 mg/L,the microorganisms in activated sludge were classified as Proteobacteria(39.2%)and Bacteroides(32.7%)as the dominant bacteria;Bacteroides(32.6%),?-Proteobacter ia(23.1%)and?-Proteobacteria(12.5%)as the dominant bacteria;Flavobacteria(19.9%)and Rhodobacteria(9.5%)are the dominant bacteria.Microorganisms in biofilms,with Proteobact eria(41.4%),Bacteroides(20.8%)and Patescibacteria(14.8%)as the main dominant bacteria;?-Proteobacteria(27.0%),Bacteroides(20.8%),Saccharimonadia(14.5%)and?-proteobacter ia(10.2%)are the dominant bacteria;Rhodobacteria(15.5%),Saccharimonadales(14.5%)and Flavobacteria(11.1%)are the dominant bacteria.When the concentration of PNP wastewater is 40 mg/L,the main microorganisms in the activated sludge are Proteobacteria(48.2%);?-Pr oteobacteria(34.5%)are the dominant bacteria;Among them,Caulobacterales(7.1%),Saccha rimonadales(7.0%)and Rhizobia(5.6%)are relatively abundant.Among the microorganisms in the biofilm,Patescibacteria(60.9%)and Proteobacteria(18.1%)are the main dominant bact eria;Saccharimonadia(60.6%)is the dominant bacteria;Saccharimonadales(60.6%)are the d ominant bacteria.(4)Compared with SBR and biological contact oxidation process,SBR can treat PNP wa stewater with higher concentration,degrade PNP wastewater at a faster rate,require less energ y consumption,and have a more stable bacterial structure.Therefore,SBR is more effective in treating PNP wastewater.