水厂尾水处理系统浓缩池上清液回用对PFASs的富集

Supernatant Recycling for PFASs Enrichment in Thickening Tank of Tailwater Treatment System in WTP

全氟和多氟烷基物质(perfluoroalkyl and polyfluoroalkyl substances,PFASs)具有累积特性,其长期的富集效应不容忽视。浓缩池上清液是水厂尾水处理系统的重要组成部分,对其进行合理回用对水资源可持续发展至关重要。研究通过构建中试试验装置,对水厂尾水处理系统中的浓缩池上清液进行连续直接回流,探究水处理工艺中PFASs潜在的富集风险,判断上清液安全回用的可行性。结果表明,浓缩池上清液中总PFASs质量浓度在14.6~36.0 ng/L,平均质量浓度为27.3 ng/L,与以长江为水源的原水PFASs组分特征基本一致,多数情况下总PFASs含量优于原水。在15 d的中试试验周期内,上清液直接回用对排泥水和炭砂滤柱反冲洗水总PFASs浓度水平未有明显改变;回用后出水总PFASs质量浓度为2.2~3.6 ng/L,未回用时为3.1 ng/L,上清液连续直接回用对出水中的PFASs组分影响甚微,未出现明显富集现象,甚至表现出了改善出水水质的效果;出水中PFASs的健康风险可忽略不计。总之,以PFASs为风险控制指标,浓缩池上清液进行连续直接回用具备一定可行性。

Perfluoroalkyl and polyfluoroalkyl substances(PFASs)exhibit cumulative properties,and their long-term enrichment effects cannot be ignored.The supernatant from thickening tank plays a crucial role in the tailwater treatment system,and its responsible recycling is vital for sustainable water resource management.This paper constructed pilot test equipment to facilitate the continuous direct recycling of the supernatant from thickening tank of tailwater system in WTP.The primary aim was to explore the potential enrichment risk of PFASs in the water treatment process and to assess the feasibility of safe supernatant recycling.The results revealed that the total concentration of total PFASs in the supernatant of the thickening tank ranges was from 14.6 ng/L to 36.0 ng/L,with an average concentration of 27.3 ng/L.This was consistent with the composition characteristics of PFASs found in raw water sourced from the Yangtze River,and the content of total PFASs was superior to that of raw water in most cases.During the 15 days pilot test period,the direct recycling of supernatant did not significantly alter the total PFASs concentration in sludge discharge water and carbon sand filter column backwashing water.The total PFASs concentration in the effluent after recycling ranged from 2.2 ng/L to 3.6 ng/L,while it was 3.1 ng/L before reuse.Continuous direct recycling of the supernatant had minimal impact on PFASs components in the outflow,and no significant enrichment occurred;it even demonstrated the potential for improving effluent quality.The health risk of PFASs in the effluent was negligible.In conclusion,using PFASs as the risk control index,the continuous direct recycling of the supernatant from the thickening tank is deemed feasible.