二级处理水中溶解性有机物特征及其对纳滤膜性能的影响

EFFECT OF SOLUBLE ORGANIC COMPOUNDS IN SECONDARY WASTEWATER ON PERFORMANCE OF NANOFILTRATION MEMBRANE

本试验采用分子量分级膜和XAD-8树脂,分析了城市二级处理水的溶解性有机物分子量和亲疏性分布特征及其对纳滤膜性能的影响。结果表明,城市污水厂二级出水水中的溶解性有机物主要集中在<2kDa的分子量区间上,且疏水性有机物的含量比亲水性有机物的含量大;分子量区间分布不同的有机物对纳滤膜透水通量和截留率有着不同的影响,分子量2kDa以下的有机物引起纳滤膜透水通量衰减较大,有机物截留率较小,达57.2%;分子量10～100kDa的有机物引起纳滤膜透水通量衰减较平缓,有机物截留率却较大最高达73.8%;亲疏性不同的有机物对纳滤膜透水通量和截留率有着不同的影响,经对膜表面阻力的测定,证实引起膜透水通量和截留率变化的主要物质为疏水性物质,而亲水性物质引起的变化较小。

XAD-8 resin and Ultra-filtration membranes with different molecular cut-offweight were used to analyze the distributing character of molecu- lar weight and hydrophilic/hydrophobic of soluble organisms which exist in secondary wastewater. In addition, the influence of those distributing characters on performance ofnanofiltration membrane was investigated. The results showed that： the second urban sewage plant effluent water soluble organic matter mainly concentrated in the molecular weight of less than two thousand Dalton, and the content of hydrophobic organic compounds was more than the content ofhydrophilic organic compounds; different molecular weight distribution of organic matter has different effect on the NF mem-brane permeable flux and retention rates, organics with molecular weight less than 2 kDa caused significant NF membrane flux decline but smaller organic retention rate, to 57.2%; organics with molecular weight ranged from 10 kDa to 100 kDa caused NF membrane flux decline flatter, but larger organic retention rate, to 73.8%. Organic compounds with different character of affinities have different effects on permeable membrane flux and retention rates, by determining membrane surface resistance, it can be confirmed that hydrophobic material was the main reason to cause membrane flux decline and retention rates were mainly whereas hvdronhilic material has a neglectable effect.