Operation Analysis And Advanced Treatment Research Of A Phthalic Anhydride Wastewater Treatment Project

This topic takes phthalic anhydride wastewater from an industrial park enterprise as the research object,and combines the existing wastewater treatment process of the enterprise,through monitoring and statistical analysis of operating data,to propose optimal operating parameters to ensure that the effluent meets the standards and is connected to the park sewage treatment plant.At the same time,in order to realize the reuse of sewage resources,the company plans to reuse part of the external drainage as circulating cooling supplementary water after advanced treatment.Using advanced oxidation method coupled with biochemical method,a small test device was built in the laboratory.By comparing the treatment efficiency of each process,the ozone concentration,hydraulic retention time and aeration amount were used as influencing factors to investigate the effects of COD,TN,TP,and NH₃-N.At the same time,three-dimensional fluorescence spectroscopy was used to analyze the removal of organic matter;the aeration volume and hydraulic retention time were used as influencing factors to investigate the operation effect of different carrier aerated biological filters,combined with microbial community analysis,to compare the performance of different microbial carriers..The main findings are as follows:（1）For the enterprise’s comprehensive wastewater that is mainly phthalic anhydride and also contains high-concentration,refractory styrene and domestic sewage,the existing treatment project adopts the combined process of UASB and A/O method.The total treatment scale is2000 m³/d,the raw water COD is 20000 mg/L,and the average influent concentrations of TN,TP,and NH₃-N are 50 mg/L,17 mg/L,and 22mg/L.After statistical analysis of the process operation of each unit,the removal effect of COD,TN,TP,NH₃-N is obvious after the process is stable,and the average effluent concentration is 460 mg/L,15.9 mg/L,2.7mg/L,1.3 mg/L,Comply with the takeover requirements of the sewage treatment plant in the industrial park.（2）Take the external drainage of the enterprise as the research object,and use ozone oxidation,iron-carbon micro-electrolysis,biological aeration filter（BAF）and its coupling process for advanced treatment to meet the goal of reclaimed water reuse.The test results show that the above several processes have certain treatment effects on COD,TN,TP,NH₃-N,etc.of the secondary effluent;among them,the combined process of ozone oxidation and ozone oxidation-BAF can reduce the COD concentration to 50 mg/L,but from an economical point of view,the ozone oxidation process is superior to its combined process.After the ozone oxidation process,the removal rates of COD,TN,TP,and NH₃-N in the effluent were 91.4%,32.4%,73.8%,and 95.2%,respectively,and the concentrations were 30 mg/L,10.8 mg/L,and 0.4 mg/L,respectively0.05 mg/L,the effluent quality meets the requirements for reclaimed water reuse.（3）The abundance and diversity of the microbial community of the iron-carbon micro-electrolysis-BAF process and the ozone oxidation-BAF process,as well as the growth of different functional bacteria were investigated.The results showed that the diversity and abundance of microbial communities were the highest in the Ozone Oxidation-BAF process.The dominant bacterial phyla in the filter mainly include:Proteobacteria（Shapingobacteria）,Parcubacteria（Mycobacterium）,Planctomycetes（Planctomycetes）,Bacteroidetes（Bacteroidetes）,Nitrospirae（Nitrospirae）,Firmicutes（Firmicutes）phylum),followedbyCyanobacteria-Chloroplast（cyanobacteria-chloroplast phylum）,Acidobacteria（Acidobacteria）and Unclassified-Bacteria（unclassified bacteria）,etc.,which include various organic matter degrading bacteria,nitrifying bacteria,denitrifying bacteria,denitrifying bacteria,denitrifying bacteria,etc.Phosphorus bacteria and other functional bacteria.（4）The total investment of the phthalic anhydride wastewater treatment project of the company is 11.379 million yuan,the direct treatment cost per ton of wastewater is 2.04 yuan,the average daily direct treatment cost is 4,080 yuan,and the whole year is about 1.4892 million yuan.If the advanced treatment of external drainage adopts the separate ozone oxidation process,the operating cost is about 0.73 yuan/m³,the operating cost of the ozone oxidation-BAF combined process is about0.77 yuan/m³,and the operating cost of the iron-carbon micro-electrolysis-BAF combined process is about 0.81 yuan/m³,compared with The operating cost of the separate ozone oxidation process is increased by 0.04 yuan/m³and 0.08 yuan/m³respectively.From the perspective of green environmental protection,ozone oxidation as a front-end pretreatment process can better avoid the generation of excess ozone;but from an economical point of view,before the operation of the aerated biological filter process,the ozone oxidation or iron-carbon micro-electrolysis process is selected as the pretreatment process not only needs to increase the construction investment and operation cost,but also needs to control the influencing factors such as aeration volume and hydraulic retention time.Therefore,based on the analysis of the results of the pilot test and considering the operating cost,it is recommended to use the ozone oxidation process for the advanced treatment of the external drainage reuse of the enterprise.