| Phthalates(PAEs)are a class of semi-volatile and fat-soluble environmental hormones,and phthalates are widely used as softeners and plasticizers in living organisms.Currently,phthalates have been detected in various environmental media and have been identified as“the second global PCB pollutant” with strong toxicological effects.At present,many countries have carried out a lot of theoretical research and practical application on the removal technology of PAEs in water.According to the different removal mechanism,the current methods for removing PAEs mainly include activated carbon adsorption,membrane filtration and advanced oxidation.The water purification safety of the traditional water purification process is low.Considering the needs of the existing process upgrade and the limitation of the infrastructure of the water plant,the coagulation precipitation filtration disinfection water purification process is strengthened and the deep processing unit is introduced.The complementary enhancement of the treatment effect is of great significance for the efficiency improvement and sustainable development of the water plant process.This project selects dimethyl phthalate,diethyl phthalate,dibutyl phthalate and di(2-ethylhexyl)phthalate,which are commonly detected in China's water bodies.The pollution status of phthalates in Ljiangjiang,Bjiang and Mjiang in South China was investigated.The background value of laboratory concentration was used to optimize the activated carbon.The enhanced coagulation process was used to remove phthalic acid.The optimal operating conditions of the ester;demonstrate the optimal operating efficiency of the separate deep processing unit and the combined process to remove phthalates.The testconclusions are as follows:The survey of phthalate pollution seasons in water sources shows that the water sources surveyed are generally polluted by PAEs and have seasonal differences,with the highest pollution value in autumn and winter,and the DBP over-standard rate in autumn water source reaches 100%;DMP,DEP,DBP were detected,and DEHP was detected only in summer B water.The detection concentrations ranged from 1.74-3.10?g/L,0,20-10.81?g/L,0.15-8.12?g/L.,0-187.71 ?g / L.The peak concentration of PAEs in the water source ranged from 14.18?g/L to 33.59?g/L,which was higher than the phthalate contamination value of other domestic water sources.The activated carbon selection test showed that the adsorption capacity of the shell charcoal for PAEs was higher than that of coal charcoal and charcoal.The Freundich empirical model can well fit the adsorption behavior of PAEs by shell carbon.In the dynamic adsorption test,the removal rate of four PAEs by shell charcoal is 85%-100%,and the adsorption time exceeds 120 min.The PAEs concentrations were all below 0.5 ?g/L.When the influent concentration of PAEs is 5?g/L,10?g/L,20?g/L,the carbon effluent concentration of each PAEs substance is lower than 2.70?g/L,which meets the water quality hygienic standard,which shows that the shell carbon is good for PAEs.The adaptability is better than the domestic conventional water treatment process.Therefore,the advanced treatment process of activated carbon can be considered in combination with the conventional water treatment process.The enhanced coagulation test showed that under the condition of 50?g/L PAEs influent,the best operating conditions were determined by the enhanced coagulation experiment: stirring at 150r/mins+3min,at which time the removal rate of ?PAEs reached41.02%.The activated carbon was co-processed at a carbon content of 15 mg/L,and the removal rate of ?PAEs was about 45%.Under the influent concentration of 10-20?g/L,40-60/L and 80-100?g/L,the average residual concentration of PAEs treated by enhanced coagulation and activated carbon was 4.93?g/L,8.55?g/L and 18.40?g./L,?PAEs removal rate ranged from 66.0% to 73.90%.The series combination process operation test shows that: considering the safety of water quality,the comprehensive removal rate of PAEs,the operation period,the maintenance life of the membrane,etc.,the project determines the optimal processparameters: ozone dosage 8mg/L,activated carbon empty bed residence time At 15 min,the ultrafiltration operating pressure was 0.1 MPa.For the ozone-activated carbon process,the order of removal of each phthalate molecule is: DMP>DEP>DEHP>DBP;for activated carbon-ultrafiltration process,when pH=7,the hydrophobicity of PAEs is enhanced,and the molecular form is mostly The filter is removed by adsorption.Higher concentrations of Na+and PAEs are likely to cause membrane fouling.With 0.001 mol/L Na+ concentration and pH=7 as the optimal conditions,the removal order of each phthalate molecule is:DEHP>DBP>DEP >DMP.The ozone-activated carbon combined process is suitable for treating small molecules such as DEP and DMP;the comprehensive removal rate of PAEs in activated carbon-ultrafiltration process is 82.46%-96.60%,which is 23.49% higher than that of activated carbon adsorption process alone,and the effluent of four PAEs.The concentration is 0-3.11 ?g / L,wherein the macromolecule DEHP.DBP treatment effect is better.The continuous flow experiment of ozone-activated carbon-ultrafiltration process is relatively stable and has a certain trend.Compared with the ozone-activated carbon process and the activated carbon-ultrafiltration process,the removal rates of the three concentrations of PAEs increased by 34.7 and 5.9 percentage points,respectively.It is recommended to use activated carbon-ultrafiltration process at low and medium concentrations,and ozone-activated carbon-ultrafiltration process under high concentration risk. |
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