Effects Of Phthalates On Vegetation-Activated Sludge Process And Its Removal

Phthalate esters（PAEs）are plasticizers that can easily enter the environment and are one of the common pollutants in wastewater treatment.The treatment effect of the new plant-activated sludge complex system（V-ASP）on PAEs and its influence on PAEs are still unclear.Three typical phthalate esters were selected in this study:Dimethyl phthalate（DMP）,dibutyl phthalate（DBP）and dioctyl phthalate（DOP）were treated with five concentrations of PAEs:50mg/L,5mg/L,500μg/L,50μg/L and 0μg/L.The pollutant concentration,plant and microorganism changes of effluent treated with V-ASP were investigated.The removal of conventional pollutants such as COD,NH₃-N,TN and TP is affected differently by the three PAEs.For COD and NH₃-N,DBP and DOP will increase the effluent concentration of COD and NH₃-N according to different influent concentration,and DBP has a more obvious effect on COD,while DOP has a greater effect on NH₃-N effluent.DMP has no effect on the effluent of COD and NH₃-N.After the effluent is stabilized,DMP can promote the TN removal by V-ASP,DBP has no effect on TN removal by V-ASP,DOP can inhibit TN removal by V-ASP,and the inhibition is reversible.DMP,DBP and DOP had no effect on total phosphorus（TP）removal by V-ASP.The removal rates of DMP,DBP and DOP were 99.968%,99.938%and 99.281%,respectively,when the influent concentration was 1-50mg/L.When the influent concentration was 2-5mg/L,the removal rates were 99.513%,98.949%and 98.267%,respectively.When influent concentration was 3-500μg/L,the removal rates were 94.188%,88.759%and 81.991%,respectively.When influent concentration was 4-50μg/L,the removal rates were 83.682%,64.315%and 68.806%,respectively.The main removal method of PAEs is microbial metabolic decomposition,and the ratio of microbial metabolic PAEs decreases with the decrease of influent PAEs concentration,among which 4-50μg/L is the lowest.At least 81.432%,49.029%and 36.890%of DMP,DBP and DOP were metabolized by microorganisms.At least 87.861%,69.348%and 60.879%of DMP,DBP and DOP without catabolism were excreted with effluent.Toxicity of PAEs to V-ASP plants DMP>DBP>DOP,it shows a trend of weakening with the increase of side chain length and increasing with the increase of influent concentration.The microbial diversity of activated sludge and rhizosphere sludge in V-ASP increased first and then decreased with the increase of influent DMP concentration,and decreased first and then increased with the increase of influent DBP concentration.DOP only increased the microbial diversity of rhizosphere sludge,but did not affect the activated sludge..The difference of microbial diversity between DMP influent rhizosphere sludge and activated sludge was the largest,and rhizosphere sludge was more susceptible to PAEs.Proteobacteria,Bacteroides and Actinbacteria were the main Proteobacteria,Bacteroides and Actinbacteria in V-ASP.Proteobacteria had the highest abundance of activated sludge（42.177%-64.766%）and rhizosphere sludge（44.659%-74.027%）in all PAEs installations.DOP could increase the abundance of Proteobacteria,while DMP and DBP had no effect.The abundance of Bacteroides decreased in activated sludge due to DOP.In foundation sludge,DMP decreased,while DBP and DOP increased.The abundance of Actinbacteria was not affected by DMP,but DBP increased the abundance of Actinbacteria,and DOP of50mg/L increased the abundance of Actinbacteria in activated sludge.