Mechanism And Regulation Of Biological Filter And Ultrafiltration Hybrid Process For Removing Typical PPCPs In Micro-polluted Surface Water

Recently,pharmaceuticals and personal care products（PPCPs）have received increasing attentions from domestic and foreign scholars due to their robust chemical persistence,refractory degradation,and easy bioaccumulation.However,few domestic studies on PPCPs were reported.Based on the pretreatment technology of SPE and UPLC-MS/MS,the detection of trace PPCPs in water was established and optimized,the distribution characteristics of PPCPs in the two major water systems of Beijiang river and Xijiang river were investigated,and removal performance of PPCPs by conventional treatment process and advanced treatment process were analyzed,respectively.Furthermore,the hybrid biological filter and ultrafiltration（UF）process was proposed to remove the PPCPs,with expects to investigate the removal performance of PPCPs and optimize the operation conditions,as well as investigate the removal routine and mechanism of the contaminants during the long-term filtration.Using the combination of s SPE and UPLC-MS/MS,a method for detecting and analyzing 25 target PPCPs in water was established and optimized.The detection limit of this method is between 0.1-4.8 ng/L,and the recovery rate of more than half of the25 target PPCPs was more than 80%.Furthermore,the developed measurement was used to evaluate the distribution characteristics of PPCPs in the Beijiang river and Xijiang river in Guangdong Province.Surprisingly,just a few kinds of PPCPs were detected in the main streams of Beijiang river and Xijiang river,with relatively low average concentration,which indicated that the potential risks of PPCPs pollution in the main stream were low.Compared with the main stream,more kinds of PPCPs were detected with relatively higher concentrations in the downstream tributaries due to the discharge of aquaculture wastewater and ground runoff,indicating a significantly higher risk of PPCPs pollution.In addition,a systematic analysis of PPCPs in the effluent of four typical drinking water treatment plants（DWTP）and pipe network water was carried out in the study area.The results demonstrated that PPCPs were found both in the effluent of DWTP and pipe network water with relatively lower concentrations and frequencies relative to the raw water;furthermore,the types,frequencies,and concentrations of PPCPs in the pipe network water were lower than those in the effluent of DWTP.Such results indicated that some certain removals of PPCPs could be found by the present conventional treatment process,and pre-chlorination and coagulation process performed higher removal efficiency of PPCPs than the treatments by sedimentary and filtration process.Furthermore,the advanced treatment by UF process and granular activated carbon（GAC）also conferred significant removal performance of PPCPs,especially the GAC process.In addition,the adsorption and removal performance of five target PPCPs by either coconut shell activated carbon or biological ceramsite were investigated,both achieving removal efficiency of EM>SDZ>SMP>SMD>CAF.Among the factors affecting adsorption and removal performance,the adsorption behavior of the three sulfonamide PPCPs were significantly affected by p H conditions,and their removal efficiency decreased with the increase of p H value.With respect to the CAF,the temperature conferred the most significant effects on its removal,with the higher temperature,the lower removal efficiency of CAF.In the treatment of either biological activated carbon（BAC）filter and aerated biological filter,it’s found that the height of filter layer,filtration velocity,PPCPs concentration in the feed water,and p H value exerted significant impacts on the removal performance of PPCPs,and instead,the air-water ratio just exhibited limited influence on the PPCPs removal.The removal efficiencies of the five target PPCPs by the two biofilters were both as follows:EM>CAF>SDZ,SMD,SMP.The removal of PPCPs by the biological filter mainly occurred in the top layer of the filter layer,amounting to about 75.0%of the total removal efficiency of PPCPs.In addition,the removals of PPCPs by the BAC filter were mainly related to both the adsorption and biodegradation process,especially the adsorption behavior.By the contrary,the biodegradation process conferred a positive effect on the CAF removals,but not significant on the other four kinds of PPCPs.The removals of PPCPs by the UF process were evidently impacted by either p H value or the PPCPs concentration in the raw water.Regarding treatment of the target five PPCPs by UF process,the highest removal rate was achieved for the CAF,while the lowest removal efficiency was found in the SMD treatment.Based on the analysis of the relationship between the removal efficiency of target PPCPs and other water quality parameters by the hybrid biological filtration and ultrafiltration process,it’s found that the removal rate of typical PPCPs was highly correlated with the removal efficiency of DOC.In the biological filter,particles and colloids in water could not be effectively diminished,which indicated that the biological filter should be coupled with the UF process to enhance the removal efficiency of colloids and particles,with hopes to improve the resistance to shock loads of turbidity and ensure the biological safety of water supply.In the treatments of hybrid biological filter and UF process,efficient removals of COD_Mn,UV₂₅₄,ammonia nitrogen,and nitrite in water were achieved,and also PPCPs substances were effectively removed.Furthermore,through tracking the transfer behavior and removal process of pollutants in the hybrid biological filter and UF process,it can be inferred that the biological filter played the fundamental role in the removals of pollutants(e.g.,PPCPs,COD_Mn,UV₂₅₄,ammonia nitrogen,etc.),and UF process also conferred significant removals of these contaminants due to the formation of biofilm on the UF membrane surface.