制革废水处理过程中微生物代谢产物特征及铬分布的解析

制革废水生化处理后的出水仍残留低浓度的铬，为揭示微量铬在活性污泥胞外聚合物(EPS)中的分布及胞外聚合物在生物处理过程中的转化，通过改良热提取法提取生物处理过程中EPS和SMP，测定各组分中多糖、蛋白质、总铬等含量，分析制革废水生物处理中EPS组分的特征、金属铬的分布和EPS各组分含量。结果表明：一级生物处理中EPS的蛋白质和多糖含量均逐渐降低，二级生物处理中EPS含量增加，活性污泥SMP与邻近沉淀池出水组分及溶解性有机物含量具有较强的相似性；铬在不同来源污泥EPS中的分布存在差异，污泥表面吸附及EPS对铬的络合富集、EPS的水解及代谢组分外排的行为均影响铬的迁移；通常，水体中铬首先被S-EPS吸收，经LB-EPS运输渗透至TB-EPS中储存。根据Pearson分析结果，总铬的分布与胞外聚合物中PS/PN及PS含量呈显著正相关(P<0.01)。以上研究结果可为制革废水铬排放总量控制和深度处理提供参考。

Analysis of microbial metabolites characteristics and chromium distribution during tannery wastewater treatment

As an ecological risk, trace amount of chromium commonly remains in the effluent of biochemical treated tannery wastewater. This study aims to clarify chromium distribution in the extracellular polymeric substance (EPS) in activated sludge and EPS transformation during the biological treatment process. The modified heat extraction method was used to extract EPS and SMP, and the contents of polysaccharides, protein, and total chromium in these extracted components were determined. The EPS component characteristics, chromium distribution and contents of EPS components during biological treatment of tannery wastewater were also analyzed. The results showed that the contents of protein and polysaccharide in the EPS decreased gradually during the primary biochemical treatment, while the EPS content increased during the secondary biological treatment. A strong similarity occurred between SMP in activated sludge and the components in the effluent from the adjacent sedimentation tank, as well as the contents of dissolved organic matter. The chromium distribution was different in the EPS extracted from different sludge, which was affected by sludge surface adsorption, chromium complexation with EPS, the EPS hydrolysis and the release of microbial metabolites. In general, chromium in water body was absorbed by S-EPS, then transported into LB-EPS and TB-EPS in turn. According to the Pearson analysis (P<0.01), the distribution of total chromium was significantly positively correlated with PS/PN and PS content in EPS. The above results provide a reference for total chromium emission control and advanced treatment of tannery wastewater.