Distributions And Removal Of PAHs And PAEs In A~2O Sewage Treatment Processes

As a class of persistent organic pollutants (POPs), Polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) are high toxic, bioaccumulated, persistent and refratory, which have serious influence on human health and environment. Because they are persistent, complicated, difficult to control and widely distributed in environment, PAHs and PAEs cause much attention from government and reseachers. There is serious attention on water safety and the removal of PAHs and PAEs in sewage treatment processes. As for low concentration in environment, PAHs and PAEs are difficult to enrich and identify. In this paper, we established a method to enrich and monitor them rapidly and accurately. Distributions and removal of PAHs and PAEs in A2O sewage treatment processes were also investigated. The main research contents were as follows:(DA rapid and accurate method was established to enrich and monitor, PAHs and PAEs. The solid-phase extraction (SPE) and the accelerated solvent extraction (ASE) were combined as the pretreatment method to enrich these substances firstly. Afterwards, they were quickly identified by high performance liquid chromatography (HPLC). The optimum extraction conditions of SPE were as follows:the elution rate was5.0mL/min, the amount of eluent was6mL, the ratio of cleaning agent methanol and water was90/10(V), the ratio of eluent methanol and dichloromethane was20/80(V). The optimum extraction conditions of ASE were as follows:the components of extraction solvent is the mixture of hexane and acetone with a ratio of1:1, the temperature of extraction was100℃, the pressure was1500psi, the time of pre-heating was3min, the time of static extraction was5min, extract twice. PAHs were identified by HPLC with ultra-violet detector(UVD) and fluorescence detector(FLD) simultaneously. The conditions of the chromatographic were as follows:the wavelength of UVD detector was254nm, and the excitation wavelength of FLD was460nm.The column temperature was35℃, the column was250mm×4.6mm,5μm, the gradient of mobile phase were water and acetonitrile with certain elution procedures, the flow rate was0.65mL/min and the injection volume was20μL.The conditions of the HPLC chromatographic to monitor PAEs were as follows:the wavelength of UVD was254nm,the ratio of the mobile phase methanol and water was80/20(V/V), the temperature of column was35℃, the injection volume was25μL and the flow rate was1.0mL/min, analysis time was20min. For PAHs, the internal standard recovery(ISR) of this method were87.65～93.28%, and the relative standard deviation(RSD) were0.68%-9.02%. Analogous for PAEs, the ISR of this method were57.7%～98.4%, and the RSD were1.47-9.29%. This method had low detection limit, high sensitivity, and less time of detection.(2) Concentrations of the PAHs and PAEs in A2O treatment processes from Jinan Everbright wastewater treatment plant(WWTP) were investigated. Pollutants in aqueous, suspended and sedimentary phase were determined respectively.16kinds of PAHs and6kinds of PAEs were selected as the key points in our reseach.16kinds of PAHs in aqueous phase, Acen, Fluo, Phe and Anth with three rings were usually detected. PAHs with five rings were less detected, and Dib was not present in aqueous phase. Besides, the concentrations of PAHs with three and four rings in suspended phase were found to be higher. Chry, BkF, Dib and Bghi were not present in some sludge treatment processes. In addition, the concentrations of PAHs with three and four rings in edimentary phase were also high.In aqueous phase,6kinds of PAEs were all detected. The concentrations of DMP, DEP, BBP, DBP. and DEHP in pretreatment process were all found to be higher than6μg/L, and DNOP was only2μg/L. In aqueous phase, DMP had the highest concentration, which was9.71μg/g in aerobic process. The concentrations of DNOP in influent and effluent were2.60and0.96μg/g respectively. In sedimentary phase, DMP also had the highest concentration. The concentrations of DMP and DEHP in sludge were10.71and1.05μg/g respectively.(3) Distributions and removal of16kinds of PAHs and6kinds of PAEs in A2O sewage treatment processes were investigated. In aqueous phase,14kinds of PAHs were detected except for BaA and Bghi and concentrations were almost between0.98and6.07μg/L. The removal rate of PAHs in pretreatment, biotreatment and sludge treatment process were2.25%～30.56%,30.74%～60.88%and25.83%～76.10%respectively. Besides, in suspended phase, the concentrations of other PAHs were between1.14and10.86μg/g. In addition, the removal rate of PAHs in the three processes were8.38%～19.46%,11.26%-45.65%and18.06%～77.63%respectively. While in sedimentary phase, concentrations of PAHs were between4.14and14.04μg/g. For the whole A2O sewage treatment processes, the total removal rate was25.96%. The selected6kinds of PAEs were all detected in the whole treatment process. In aqueous phase, concentrations of6kinds of PAEs were between0.08and7.63μg/L, The removal rate of PAEs in pretreatment, biotreatment and sludge treatment process were1.57%～6.88%,36.54%～60.97%and14.53%～38.43%respectively. In suspended phase, concentrations of PAEs were between0.97and9.05μg/g, The removal rate of PAEs in pretreatment, biotreatment and sludge treatment process were3.06%～70.37%,23.03%～51.13%and19.56%～73.25%respectively. While in sedimentary phase concentrations were between0.10and10.71μg/g. For the whole A2O sewage treatment processes, the total removal rate was48.84%.