净水厂沉淀池污泥中PFCs分布及吸附/解吸规律研究

Study on Distribution and Adsorption/Desorption Behavior of PFCs in Sludge From Sedimentation Tank of Water Supply Plant

探究了长江南京段某净水厂平流式沉淀池过程水、排泥水和不同分段污泥中全氟辛酸(PFOA)和全氟辛烷磺酸(PFOS)两种全氟化合物(PFCs)的浓度分布,研究了沉淀池污泥对低浓度PFCs(200 ng·L^(-1))的吸附/解吸规律。结果表明:沉淀池排泥水和过程水中PFOA和PFOS的质量浓度分别为48.35～63.38和56.26～71.62ng·L^(-1),中段污泥中PFOA和PFOS的干重浓度分别为1.03和1.54ng·g^(-1)·dw(干重),均高于前段和中段污泥。PFOA和PFOS在污泥中的吸附和解吸分别在24和36 h能达到平衡,两种PFCs均存在不同程度的解吸滞后现象,PFOA在污泥中基本为可逆吸附,约30%的PFOS不可逆吸附于污泥中。PFOA的吸附容量低于PFOS,PFOA的解吸率高于PFOS。

The levels of perfluorooctanoate(PFOA)and perfluorooctane sulfonate(PFOS)in process water,sludge wastewater and sludge from horizontal sedimentation tank of a water supply plant were quantified.The adsorption and desorption of PFCs of low concentration(200 ng·L-1)on sludge from sedimentation tank were studied.The results showed that the mass concentrations of PFOA and PFOS in sludge wastewater and process water were 48.35~63.38 and 56.26~71.62 ng·L-1,respectively.Simultaneously,PFOA and PFOS concentrations in sludge from the middle sedimentation tank were 1.03,1.54 ng·g-1·dw(dry weight),respectively.And both of them were higher than that of sludge from the front and rear sections of sedimentation tank.The adsorption and desorption of PFCs on sludge reached equilibrium at 24 h and 36 h,respectively,while desorption hysteresis was observed during the desorption process.PFOA was basically reversible adsorbed on sludge,and about 30%of PFOS was irreversibly adsorbed on sludge.The adsorption capacity of PFOA was lower than that of PFOS,while the desorption rate of PFOA was higher than that of PFOS.