Research On Deep Degradation Of Biochemical Tail Water Of Citric Acid By Ozone Catalytic Oxidation And MBBR Combined Process

After the secondary biochemical treatment of citric acid wastewater,the effluent has the characteristics of high COD,deep color,and poor biochemical properties.It is difficult to deeply degrade the secondary biochemical tail water of citric acid by using conventional sewage treatment technology.In recent years,the country has stepped up its efforts to remediate polluting industries,and industrial wastewater discharge standards have gradually improved.Research on new and efficient advanced sewage treatment technologies has become imminent.In this study,the ozone catalytic oxidation technology and the ozone catalytic oxidation-moving bed biofilm reactor(MBBR)combined process were used to deeply degrade the biochemical tail water of citric acid.The main research contents include:ozone catalytic oxidation technology process parameter optimization,ozone catalysis-MBBR combined process parameter optimization,and MnOx-CeOx composite bimetallic catalyst regeneration process parameter optimization.The specific conclusions are as follows:(1)Aeration methods(bottom aeration process,middle aeration process,jet aeration process)have a significant impact on the removal of COD and chromaticity in the biochemical tail water of citric acid.By comparing the removal effects of COD and chromaticity under different aeration processes,the best aeration method is determined to be jet aeration.This conclusion provides a theoretical basis for the practical application of jet aeration technology in industry.(2)Using MnOx-CeOx composite bimetal oxide as a catalyst,single factor experiment and response surface method were used to optimize the operating parameters of ozone catalytic oxidation technology to degrade citric acid biochemical tail water,and the best process parameters were obtained as follows:air intake 1 m3·h-1,ozone concentration 55 mg·L-1,residence time 60 min.Under these conditions,the effluent COD was 38.7 mg·L-1,and the removal rate reached 63.8%.The effluent index has reached the level I standard(COD=50 mg·L-1)of Jiangsu Province’s Restrictions on Discharge of Major Water Pollutants from Urban Sewage Treatment Plants and Key Industrial Industries in Taihu Lake Region(DB32/1072-2007).(3)The combined process of ozone catalysis and MBBR is used to deeply degrade citric acid biochemical tail water.Taking the COD removal rate as an indicator,the best operating parameters are obtained:in the ozone catalytic pretreatment system,when the ozone dosage is 30 mg·L-1,the hydraulic retention time is 60 min,and the ozone intake amount is 1 m3·h-1,the COD and chromaticity removal rates of the effluent from the ozone catalytic pretreatment were 36.4%and 83.3%,respectively,and the biochemical properties of the effluent increased from 0.08 to 0.22;in the MBBR system,the HRTm was 6 h and the gas-water ratio was 4:1,the effluent COD is less than 40 mg·L-1,and the chromaticity is stable at about 10 times.(4)The regeneration process(direct calcination method,dilute nitric acid impregnation method,ethanol impregnation method)has a significant impact on the recovery of the activity of the used catalyst.By comparing the degradation effect of the catalyst on Rhodamine B after different regeneration processes,it is concluded that the best process is the dilute nitric acid impregnation method.The best process parameters are:impregnation concentration of 8%and impregnation time of 10 min.And through SEM,XRD,XRF,BET analysis of the regenerated catalyst,it is found that the surface of the regenerated catalyst is smoother,the active components increase,and the specific surface area increases.