铝形态对铝系混凝剂去除抗性基因的影响

Effect of aluminum species on removal of antibiotic resistance genes by aluminum-based coagulants

抗生素抗性基因(ARGs)会对自然环境和人体健康造成潜在的巨大威胁,而污水处理厂的出水是环境ARGs主要来源之一.铝基混凝工艺可以有效削减出水中氮、磷等指标,然而对于ARGs的去除以及其中起主要作用的铝形态仍然不清楚.因此,本文首先对污水厂现有工艺段出水中的ARGs进行了调研,结果发现,在经过活性污泥工艺处理后ARGs的丰度出现明显提高,并且在最终的出水中sulⅠ和sulⅡ基因有较高残留.接着以sulⅠ和sulⅡ为模型物,研究了氯化铝(AlCl_(3))和聚合氯化铝(PAC)混凝剂对污水处理厂出水中ARGs和int I1基因的去除效果,探讨了不同的Al形态对ARGs去除效果的影响.结果发现,AlCl_(3)和PAC的混凝过程均能够有效去除ARGs,去除率为0.1~2.26-log.统计学相关分析发现,ARGs的去除主要是通过去除抗性细菌来实现,并且碱性条件下(pH为8或10)混凝过程对ARGs去除率较高,这表明ARGs的有效去除是通过铝水解产物尤其是无定形Al(OH)_(3)沉淀的吸附和网捕来实现,其中,AlCl_(3)中起主要作用的是单体铝和低聚态铝(Al_(5))物种,而PAC中则是单体铝和高聚合态Al_(13)发挥主要作用.

Antibiotic resistance genes(ARGs) pose a potential huge threat to the natural environment and human health,and effluent from wastewater treatment plants(WWTPs) is one of the main sources of environmental ARGs.The aluminum-based coagulation process can effectively reduce nitrogen and phosphorus in water,while the removal of ARGs by aluminum coagulant and the main aluminum species during this process are still unclear.Herein,we investigated the type and abundance of ARGs in various units of WWTP effluent,and found that the abundance of ARGs significantly increased after the activated sludge treatment and there were still high residues of sulⅠ and sulⅡ genes in the final effluent.Then,we studied the removal of aluminum chloride(AlCl_(3)) and polyaluminum chloride(PAC) on ARGs(i.e.,sulⅠ and sulⅡ) and intI1 genes in WWTP effluent,and explored the effects of Al species on the removal of ARGs.The results showed that both AlCl_(3) and PAC could effectively remove ARGs with removal rates of 0.1~2.26-log.Correlation analysis further revealed that the removal of ARGs was mainly achieved by the removal of antibiotic resistant bacteria.Moreover,the coagulation process under alkaline conditions(pH 8 or 10) has a high removal rate of ARGs,indicating that the effective removal of ARGs is achieved by the adsorption and net capture of aluminum hydrolysates,especially amorphous precipitation Al(OH)_(3).The main role in AlCl_(3) coagulation are monomer aluminum and oligomeric aluminum(Al_(5)) species,while monomer aluminum and high polymerization Al_(13) play the main role for PAC coagulation.