光催化/活性炭/纳滤组合工艺处理二级出水及对膜污染的控制

污水的资源化与回用可作为城市和各类建筑的非传统水源,必须满足相关水质标准,其中有机物一直是广泛关注的重要指标.本文采用华北某市大型污水厂的二级出水,研究了二氧化钛光催化氧化(UV-TiO_2)和颗粒活性炭(GAC)技术对溶解性有机物的去除特性以及对纳滤(NF)的膜污染控制特性,构建了UV-TiO_2/GAC/NF组合工艺,评价了组合工艺的有机物去除效能和膜污染控制作用,解析了影响NF膜污染程度的有机物种类和相对分子质量分布特征.结果表明,UV-TiO_2和GAC技术均可不同程度地缓解NF膜的不可逆污染、降低膜通量衰减速率; UV-TiO_2/GAC联用的不可逆膜污染程度比单独UV-TiO_2或GAC技术分别降低了48. 7%或61. 4%.类蛋白质和类腐殖质等有机污染物是不可逆膜污染的主要组分;相对分子质量为小于3×10~3和30×10~3～100×10~3的有机物是造成纳滤膜通量下降的主要因素. UV-TiO_2/GAC/NF组合工艺的COD、DOC和UV_(254)去除率为45. 7%、74. 5%和89. 2%,出水中COD、DOC和UV_(254)等有机物指标均得到有效去除.研究成果为城市和各类建筑非传统水源的深度净化与多途径回用提供了技术支持.

Organic Matter Removal and Membrane Fouling Control of Secondary Effluents Using a Combined Nanofiltration Process

For cities and various types of constructions, the recycling and reuse of wastewater can be an important and unconventional water source. However, water quality must meet relevant standards, especially with respect to organic matter. In this study, secondary effluents from a large sewage plant in a northern city in China were analyzed. The removal efficiencies for soluble organic matter and the characteristics of nanofiltration (NF) membrane fouling of UV-TiO₂ photocatalysis and GAC adsorption were studied, and a combined UV-TiO₂/GAC/NF process was developed. The removal of organic matter and the controlling effect of membrane fouling in the combined UV-TiO₂/GAC/NF process was evaluated. The types and molecular weights of organic matter, which influenced the degree of membrane fouling, were analyzed. The results indicated that both the UV-TiO₂ and GAC techniques can alleviate irreversible NF membrane fouling and reduce the attenuation rate of membrane flux to some extent. Compared to individual UV-TiO₂ or GAC processes, the degree of irreversible membrane fouling in the combined UV-TiO₂/GAC process was reduced by 48.7% and 61.4%, respectively. Protein-like and humus-like components were dominant in the irreversible membrane fouling, and organic components with relative molecular mass of less than 3×10³ and between 30×10³ and 100×10³ were dominant in causing a decrease in NF membrane flux. Organic content was efficiently removed using UV-TiO₂/GAC/NF combined process, achieving a removal rate for COD, DOC, and UV₂₅₄ of 45.7%, 74.5%, and 89.2%, respectively. This study provides technical support for the advanced treatment and multi-path reuse of unconventional water sources for cities and various types of constructions.