Study On Pretreatment Of Fine Chemical Wastewater With High COD And High Salinity

With the rapid development of China’s industrial modernization,as one of the important industries in the industrial system,the demand for fine chemicals has increased significantly,and all kinds of products are widely used in people daily life.At the same time,the discharge of industrial wastewater is also growing gradually.As the result,the water environment is seriously polluted,as well as threatening the human health and living environment,it is mainly due to the complexity of the water quality,high COD content and salt content,water quantity difference,poor biodegradability,deep chromaticity and high toxicity.At present,more efficient and green treatment of high concentration of industrial wastewater which is difficult to degrade has become an important goal of the current social sustainable development,so it is particularly important for effective water pretreatment.Aiming at the problems of complex effluent composition,high COD concentration and substandard water quality in the chemical plant,this research studied the treatment effect of different pretreatment processes on chemical wastewater by small scale test.The treatment were carried out for the treatment effect and the optimal combination process of economic comparison.Different pretreatment processes are used to treat wastewater.The treatment effects of single coagulant pretreatment,coagulant combination pretreatment,negative pressure evaporation pretreatment,iron-carbon micro-electrolysis,Fenton oxidation,ozone oxidation and ozone/hydrogen peroxide oxidation pretreatment were investigated,and the main influencing factors of each treatment process were determined.The results showed that the optimal conditions of coagulation pretreatment were 25 mg/L Polyacrylamide(PAM),p H=7,COD removal rate of 36.7%,TDS removal rate of 52.2%.After negative pressure evaporation pretreatment,the six water samples were mixed according to the flow ratio,and the COD removal rate was 74.3%after evaporation,TDS removal rate of 99.8%.The advanced oxidation treatment adopts four methods: iron-carbon micro-electrolysis,Fenton oxidation,ozone oxidation and ozone/hydrogen peroxide oxidation.Under the optimal conditions,the COD removal rate of iron-carbon micro-electrolysis reaction reached 44.1%.The COD removal rate of Fenton oxidation reaction can reach 52.4%.The COD removal rate of ozonation reaction was 53.7%.The COD removal rate of ozone/hydrogen peroxide oxidation reaction reached 55.6%.Compare and select the best combination process.Through comparison and selection,the combined process of "Coagulation-negative pressure evaporation-ozone oxidation" was determined as the most suitable pretreatment process,and the main influencing factors,treatment effect and operation cost of each treatment unit were preliminarily determined.After the pretreatment of wastewater via the combined process,the COD removal rate can reach 85.3%,TDS value reduced to 0.031 g/L,and the effluent B/C value increased to 0.21.In terms of economy,the cost of treating wastewater via the combined process is 23.63 yuan per ton.The changes of organic components in wastewater after treatment via combined process.Using Fourier transform infrared(FT-IR),ultrafiltration membrane separation,three-dimensional fluorescence,gas chromatography-mass spectrometry(GC-MS)for pretreatment units at all levels of the composition of organic matter in water were analyzed,and the combination found in wastewater treatment process of the communist party of China to detect the organic matter in 100,which contains nitrogen heterocyclic aromatic hydrocarbons,catalytic agents,dyes and the dye intermediate,medicine intermediate,pesticide intermediate,organic compounds are mainly distributed in the molecular weight of > 100 kda,100 kda ～ 50 kda and < 3 kda range.After treatment,the system is mainly composed of small molecular organic substances,and the molecular weight of the organic substances is mainly distributed in the range of5 k Da～3k Da and < 3k Da.The ester and ether groups in the wastewater are greatly reduced,and most of the fulfulic acids are degraded.