Research On High COD Chemical Wastewater

This paper took chemical wastewater which came from emissions of a large chemical industrial park in zhejiang province as research object. It investigated the wastewater source, characteristics, water quality, water yield and so on.The results were as follows:high COD, toxicity, containing a variety of dyes, refractory, high content of organic pollutants, the components of complex, great changes in water quality. According to the actual condition of the wastewater, in this paper, we put forward the feasible combination process of Fenton oxidation micro electrolysis-coagulant-biochemical process. Through this combination process, the wastewater reached the receive standard of the secondary of sewage plant of cities and towns in this area.In Fenton oxidation process, it examined the influence of the pH, reaction time, the proportion of hydrogen peroxide and ferrous, the dosing quantity of hydrogen peroxide and other factors by single factor method. Ultimately, the best process conditions of Fenton oxidation were as follows:pH was3.0,1hour response time, dosage of hydrogen peroxide was60g/L, the ratio of hydrogen peroxide and ferrous was10:1. Under this condition, the average COD removal rate was45.0%and the colourity removal rate was54.6%. Then we got the effluent water quality, COD was about14000mg/L, colourity was about6250times.In micro-electrolysis method, It studied the water pH, reaction time, the micro electrolysis filler, the water volume, the size of the air condition and other factors for the influence of the treatment effect. By experiment we could get the optimal experiment conditions:choosing micro electrolysis new packing, water pH value about3.0, air size for3to4mg/L,1.5hour reaction time, when the filler volume was10L, the water volume was just12L. Under the best experimental conditions, COD removal rate was26.2%, the colourity removal rate was67.4%and B/C ratio increased from0.22to0.55.For Coagulant method, It inspected kinds of coagulant dosing quantity, coagulation pH, stirring speed, the static time and other factors. The optimum process conditions were as follows:Coagulation agents choosing iron series polymerization iron sulfate, its dosing quantity for2000ppm, coagulation pH7.5, stirring speed of150r/s, rest time for30min. Under the this condition, COD removal rate could reach24.8%, and chromaticity removal rate could reach29.7%, and the SS removal rate could reach66.0%.Because the wastewater was hard to biochemical treatment, the research used biochemical method of anaerobic-aerobic activated sludge combination process. It examined the active sludge domestication and cultivation, water pH, temperature, HRT, dosing quantity of disodium hydrogen phosphate and other factor such as dissolved oxygen, and get the best process conditions, these were, dissolved oxygen concentration for3-4mg/L, water pH8.0, HRT for48hour, the temperature for25to30℃, disodium hydrogen phosphate dosing quantity for0.35g/L. Biochemical system ran in a stable condition, and the average COD removal rate was87.4%, the average ammonia nitrogen removal rate was38.2%, the colourity removal rate was about71.3%on average.Test results showed that after the combination process of Fenton oxidation-micro electrolysis-coagulant-biochemical method, effluent water quality were as follows:COD for about380mg/L, the color for100times, ammonia nitrogen30mg/L, the concentration of suspended matter was210mg/L. The experiments showed that the combination process had good operation effect for the wastewater of this chemical plant. There were21pictures,27tables and69references in this paper.