Cranfield Water Science Institute, Cranfield University, College Road, Cranfield, MK43 0AL, United Kingdom.
Severn Trent Water, 2 St John's Street, Coventry, CV1 2LZ, United Kingdom.
Water Res. 2018 Jan 1;128:120-128. doi: 10.1016/j.watres.2017.10.050. Epub 2017 Oct 25.
This study investigated the impact of coagulation-flocculation treatment on metal form and bioavailability in municipal wastewater. Real humus effluent samples were separated into particulate, colloidal and truly dissolved fractions before and after treatment with either ferric chloride (FeCl) or the biopolymer Floculan. Results revealed that both reagents effectively (≥48%) eliminated Cu, Pb and Zn from the particulate fraction and removed Cu and Zn from the colloidal fraction in conjunction with colloidal organic carbon (COC). Although organics in the truly dissolved fraction were resistant to removal, Floculan reduced Cu in this fraction by 72% owing to the complexation of free Cu ions to phenol and amino groups along the polymeric chains, revealing an additional removal pathway. In fact, COC removed in the CF process by Floculan was replaced with truly dissolved compounds, input as a result of this reagents organic composition. Floculan, therefore, reduced the soluble concentration of Cu and Zn without changing the DOC concentration, thus reducing the bioavailability of these metals in treated effluent. FeCl did not reduce the bioavailability of target metals, thus did not deliver any environmental benefit. This work provides important information for the selection and development of high performance coagulants to improve metal removal.
本研究考察了混凝处理对城市废水中金属形态和生物有效性的影响。在使用三氯化铁 (FeCl) 或生物聚合物 Floculan 进行处理之前和之后，将真实腐殖质废水样品分离成颗粒、胶体和真正溶解的部分。结果表明，两种试剂都能有效地（≥48%）从颗粒部分去除 Cu、Pb 和 Zn，并与胶体有机碳 (COC) 一起从胶体部分去除 Cu 和 Zn。尽管真正溶解部分的有机物难以去除，但 Floculan 通过将游离 Cu 离子与聚合物链上的苯酚和氨基络合，将该部分的 Cu 减少了 72%，揭示了另一种去除途径。事实上，Floculan 在 CF 过程中去除的 COC 被真正溶解的化合物所取代，这是由于该试剂的有机组成造成的。因此，Floculan 降低了 Cu 和 Zn 的可溶性浓度，而不改变 DOC 浓度，从而降低了处理废水中这些金属的生物有效性。FeCl 没有降低目标金属的生物有效性，因此没有带来任何环境效益。这项工作为选择和开发高性能混凝剂以提高金属去除率提供了重要信息。
