| Currently,membrane bioreactor combined with reverse osmosis（RO）is an effective treatment method for landfill leachate.However,the most critical issue in implementing this technology is the generation of reverse osmosis concentrate.ROC has the characteristics of low biodegradability and high pollutant concentration and contains a large amount of humic acid,aldehydes,ketones,and heavy metals.The most economical option for concentrate disposal is recycling to landfill.ROC recycling can cause the accumulation of pollutants such as humic acid and heavy metals,reducing the treatment efficiency.Ozone is a strong oxidant with high reactivity and selectivity to macromolecular organic pollutants.However,the utilization rate of ozone in the application process is low,and the processing capacity of concentrated liquid is limited.Therefore,ozone combination technology is widely used to treat practical wastewater.The main constituents of ceramic membranes are metal oxides,which can stimulate ozone to generate free radicals.Furthermore,the ceramic membrane has the advantages of long life,strong thermal stability,solid chemical stability,and strong mechanical stability.Therefore,ceramic membranes have great potential for application in water treatment.Based on the ceramic membrane ozone generator,this study investigated the removal ability of CM/O3 in the treatment of landfill leachate reverse osmosis concentrate.In order to further improve the degradation ability of the concentrate,the O3/Ca（OH）2-CM system was proposed to simultaneously separate and oxidize the concentrate.In addition,a flow field simulation study was carried out on the special structure of the 19-hole multi-channel ceramic membrane used.The main research results of the full text are as follows:（1）Under the conditions of ceramic membrane pore size 50 nm,reaction pressure0.2 MPa,ozone concentration 60 mg/L,and ozone flow rate 3 L/min,the COD removal rate of ROC during CM/O3 treatment was 81.93%,and the TOC removal rate reached62.6%.After CM/O3 system treatment,the COD removal rate was 2.5 times and 1.17times that of single CM and single O3.The effects of different operating conditions on the removal efficiency and membrane flux changes were discussed.In addition,by UV245,3D-EEM,and GC-MS analysis,the changes in the composition of macromolecular organic compounds in the ROC during the reaction treatment of the CM/O3 system were compared and analyzed.The results show that ozone can quickly and effectively degrade some humic macromolecular organic pollutants in ROC,and the degree of aromatization in wastewater is rapidly reduced.After 5 min of treatment,the UV254 rapid removal rate of the concentrate can reach 39.9%.During the treatment process,with the increase of ozone dosage,the humic substances in the concentrated solution are effectively degraded,but at the same time,a small number of intermediates of soluble microbial by-products are also produced.（2）The COD removal rate of ROC by O3/Ca（OH）2-CM system can reach as high as95.69%,TOC removal rate is 91.89%,and UV254 removal rate is 95.13%.The COD removal efficiencies were 3.29,2.82,and 1.27 times higher than those of CM,Ca（OH）2,and O3 systems,respectively.Ca（OH）2 acts as both a flocculant and an ozone catalyst in the system.It can catalyze ozone to improve the utilization rate of ozone and improve the mineralization rate of ROC while flocculating ROC.The effects of different operating conditions on the removal efficiency and membrane flux changes were discussed.Moreover,the changes in macromolecular organic matter composition before and after treatment with the four systems were compared and analyzed.There are 24 kinds of organic substances in the concentrated solution,and 20,18 and 9 kinds of organic substances remain in the wastewater after being degraded by CM,Ca（OH）2,and O3,respectively.However,after O3/Ca（OH）2-CM treatment,only 5 kinds of organic matter remained in the wastewater,and the total concentration of organic matter was only18.3708 mg/L.The concentrated solution’s carbon-carbon double bond and carbon-oxygen double bond unsaturated organic matter are completely degraded.（3）The effect of the microchannel of the 19-hole multi-channel ceramic membrane on the fluid flow of gas-liquid mixture was studied by CFD simulation technology.The flow field simulation results show that,compared with the single-channel reactor,the19-hole multi-channel can effectively disperse the gas,slow down the gas aggregation phenomenon,and enhance the solubility of the gas in the liquid phase.The flow velocity distribution of the mixture in the 19-hole multi-channel reactor is uniform,and the pressure is high,its velocity and pressure are much higher than those in the single-channel reactor.In addition,the effects of inlet gas phase velocity and outlet pressure on the 19-well multichannel reactor were investigated.The results show that the gas holdup increases with increasing gas phase velocity.However,when the inlet velocity of the gas phase is too high,a large amount of gas accumulates in the reactor,and the outlet pressure has little effect on the fluid flow of the gas-liquid mixture in the reactor. |
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