粉末活性炭-超滤组合工艺对二级出水中污染物的去除及膜污染机制研究

采用粉末活性炭(PAC)-超滤(UF)组合工艺处理污水处理厂二级出水,探讨不同PAC投加量下PAC-UF组合工艺对溶解性有机物(DOC)及抗生素抗性基因(ARGs)的去除效果,分析PAC对UF膜污染的缓解机制。结果表明,与直接UF相比,PAC-UF组合工艺可有效降低出水DOC和ARGs含量;水中4种ARGs与微生物含量、整合子intI1、DOC浓度间呈显著相关关系,说明去除上述指标有助于削减不同类型ARGs;PAC可吸附水中小分子量有机物,提高膜比通量,改善UF膜的反冲洗效果,PAC投加量为20mg/L时效果最好;PAC投加量增加可使滤饼层变得致密,使UF膜的不可逆污染阻力下降,但总污染阻力增加;直接UF与PAC-UF组合工艺的膜污染主导机制均为滤饼层污染,其中PAC-UF组合工艺受滤饼层污染机制影响更大。综合考虑污染物去除及膜污染缓解效果,采用低投加量(20mg/L)的PAC-UF组合工艺处理二级出水最为适宜。

Removal of pollutants in secondary effluent by PAC-UF combined process and membrane fouling mechanism

The combined process of powdered activated carbon(PAC)and ultrafiltration(UF)was used to treat the secondary effluent of sewage treatment plant,and the effect of PAC-UF combined process on the removal of dissolved organic carbon(DOC)and antibiotic resistance genes(ARGs)under different dosage of PAC was explored,and the membrane fouling control mechanism was also analyzed.The results showed that PAC-UF effectively reduced the effluent concentrations of DOC and ARGs,compared with direct UF.The concentrations of four ARGs showed a significant positive correlation with the concentrations of microorganism,intI1 and DOC in the secondary effluent,indicating that the removal of the above substances could help to reduce different types of ARGs.PAC could improve membrane specific flux and the effect of backwashing by removing the organic matters with low molecular weight,and the performance was the best when PAC dosage was 20 mg/L.The increase of PAC dosage could make the cake layer dense,reduce the irreversible fouling resistance of the UF membrane,but increase the total fouling resistance.The dominant mechanism of membrane fouling in the direct UF and PAC-UF were both the cake layer,but the PAC-UF was affected by the cake layer mechanism more seriously.Comprehensively considering the effects of pollutants removal and membrane fouling controlling,the PAC-UF with low PAC dosage(20 mg/L)was most suitable for the treatment of secondary effluent.