Study On The Removal Of Di (2-Ethylhexyl) Phthalate From Sewage By A Slow Sand Filter

At present, with the water shortage and pollution becoming increasinglyserious and people’s requirement to water quality improving continuously, thedevelopment of efficient wastewater treatment technology to improve recycledwater quality has been an important way to solve the water crisis. However，thereare some environmental hormone substances in wastewater, such as DEHP, whichare difficulty to remove, constitute a serious threat to health of human life.Therefore,the research on slow sand filtration technology used for sewage advanced treatmentwas conducted in order to test its removal performance for DEHP mainly.By using a lab scale slow sand filter with quartz sand filter bed to polish thesecondary effluent of SBR, the removal efficiency and mechanism for conventionalindicators and DEHP was studied. Meanwhile, the impact of the filter bed depth onthe removal of DEHP was analyzed and technical and economic evaluation of theSSF was also done.The slow sand filter has a good removal effect for turbidity and COD, whichare above80%,30%respectively, while the removal rate for NH3-N is not obvious.The increase of filter bed depth can improve its removal effect for conventionalindicators slightly.To test the treatment efficiency of slow sand filter for DEHP, the conventionalslow sand filter with0.8m depth filter bed and0.1m/h filtration rate was operated.Results shows that it has an excellent performance for DEHP removal fromwastewater. When DEHP in influent of slow sand filter is6.1-62.8μg/L, DEHP ineffluent is declined to1.7-7.3μg/L. When a shock concentration of DEHP282.8μg/Lin influent is applied to the slow sand filter, DEHP in the effluent is still below10μg/L.In order to study the impact of the filter bed depth on the removal of DEHP, thefilter depth was changed to0.15m. The result shows that: Though the influentconcentration of DEHP vary between6.68-77.65μg/L,the effulent concentration of itis maintained to2.29-7.1μg/L. When a shock concentration of DEHP230μg/L ininfluent is applied to the slow sand filter, DEHP in the effluent increases to33.2μg/L.All data indicate that when DEHP concentration exceeds a certain range in inlet,the deeper is the depth of the filter bed, the stronger is the removal capability of it forDEHP.In order to study the mechanism for removing DEHP of the slow sand filter, thematerial banlance test for DEHP was carried out. The result shows that: DEHPeliminated by biodegradation within a filtration cycle accounts for62.2%of theinfluent DEHP total content，so the slow sand filter shows a good biologicalremoving efficiency.The amount of DEHP accumulated on the surface membrane ofthe slow sand filter changes obviously at the beginning and the end of a operationperiod. Thus, the surface membrane of the slow sand filter plays a significant role inbiosorption and biodegradation of DEHP.The conclusion is that, slow sand filter can effectively remove DEHP insecondary effluent, so it is a feasible and economical technique for the removal ofDEHP.