N-亚硝胺在不同处理工艺污水处理厂中的分布及其

以6种典型N-亚硝胺(NAs)为研究对象,基于质量浓度监测数据系统研究了它们在3种不同处理工艺的污水处理厂中的分布及其去除规律,并分析了它们在受纳河水中的污染概况及来源.结果表明,6种NAs在3种不同处理工艺污水处理厂各工艺段废水中普遍存在,其中主要污染物为NPIP、NDMA和NPYR,质量浓度水平为几十到几百ng·L-1. 3种不同处理工艺的污水处理厂都能对NAs起到一定的去除效果,其中改良A~2/O和A~2/O+MBR对NAs的去除效果较好,总体去除率分别为95%和63%,主要依靠生化阶段的微生物降解和转化.在过滤、MBR和消毒阶段,废水处理体系中NAs前驱物经一系列反应后会形成一定的NAs增量. 6种NAs在受纳河流的表层水中也频繁检出,主要污染物和污水处理厂进水中的主要污染物一致,仍然是MDMA、NPIP和NPYR.受纳河流中的NAs来源广泛而复杂,包括污水处理厂尾水排入、未经处理的生活污水和工业废水以及工业区地表径流等的汇入.因此,应该通过增强污水收集和处理能力、优化污水处理工艺等措施减少NAs向受纳河流的输入.

Occurrence and Removal of N-nitrosamines in the Wastewater Treatment Plants Using Different Treatment Processes

This study measured the concentrations of six N-nitrosamines (NAs) in water samples from each process stage of three wastewater treatment plants (WWTPs) and their corresponding receiving rivers. The occurrence and removal of NAs was then systematically studied in three WWTPs using different treatment processes, and their pollution profiles and sources in the receiving rivers were analyzed. The results showed that the six NAs occurred widely in the wastewater from every process stage of three WWTPs. NPIP, NDMA, and NPYR were the dominant pollutants with concentrations in the tens to hundreds ng·L^-1. The three WWTPs using different treatment processes removed a certain amount of NAs, and the modified A²/O and A²/O+MBR showed good NAs removal effects, with total removal rates of 95% and 63%, respectively. The removal of NAs mainly relied on microbial degradation and transformation during the biochemical stage. During the filtration, disinfection, and MBR stages, NAs precursors in the wastewater treatment system could form some added NAs after a series of reactions. The six NAs were also frequently detected in the surface waters of receiving rivers, where the main pollutants were also MDMA, NPIP, and NPYR, which was consistent with the influent of the WTTPs. The sources of NAs in the receiving rivers were wide ranging and complicated, including emission from the effluent of the WTTPs, the release of untreated sanitary sewage, industrial wastewater, and surface runoff from industrial districts. Therefore, effective measures should be taken to reduce the input of NAs into receiving rivers, such as enhancing the capacity of sewage collection and treatment and optimizing sewage treatment processes.