天然水背景下残余铝组分分析及其对纳滤膜污染的贡献

Residual aluminum components and their contribution to nanofiltration membrane fouling in natural water

残余铝虽然已被广泛证实是造成饮用水处理纳滤膜污染加剧的关键污染物之一,但是到目前为止,尚不清楚残余铝中各组分对纳滤膜污染的影响规律和贡献率.根据残余铝的产生机理,在不扰动实际水体初始状态的前提下,有效调控了纳滤进水中残余铝的种类分布,从残余铝的聚合度及其与有机物的络合程度两个方面对膜污染进行分析.结果显示,中高聚态铝(Al_(b)/Al_(c))的质量浓度即使在200μg/L的条件下也不会对膜污染速率产生明显影响,而低聚态铝(Al_(a))在50μg/L的质量浓度范围内就能显著加剧膜污染.相比于Al_(a)的质量浓度,Al_(a)与天然有机物(NOM)的络合稳定性对膜污染的影响更为显著.所以,络合稳定性较高的Al_(a)-NOM是造成纳滤膜污染加剧最关键的残余铝形态.

Although residual aluminum has been recognized one of the key foulants contributing to nanofiltration membrane fouling in drinking water treatment,the degree to which various residual aluminum components influence membrane fouling is unknown.In this study,the species distribution of residual aluminum in the nanofiltration influent was manipulated in order to analyze the effect of residual aluminum’s degree of polymerization and complexation with organic matter on membrane fouling.Results showed that even when the concentrations of medium and high polymeric aluminum(Al_(b)/Al_(c))were increased to 200μg/L,they had virtually little impact on membrane fouling,whereas the concentration of oligomeric aluminum(Al_(a))in the range of 50μg/L could significantly aggravate the membrane fouling rate.In comparison to the concentration of Al_(a),the complex stability of Al_(a) and natural organic matter(NOM)was shown to have a higher effect on membrane fouling.As a result,the most significant residual aluminum form that aggravated the fouling of nanofiltration membranes was thus the more stable Al_(a)-NOM.