Evaluation of Chemical and Microbiological Factors Affecting Nitrification in Chloraminated Drinking Water Distribution Systems

[01:1218 Harrington]本研究项目的目的是建立一个综合氯胺化饮用水系统中发生的化学和微生物现象的模型。随着氯胺的腐烂，消毒电位降低，由腐烂形成的氨被氨氧化细菌（AOB）转化为亚硝酸盐。这导致了两个问题：首先，亚硝酸盐是一个公共卫生问题；其次，亚硝酸盐加速氯胺残留的分解，进一步降低消毒潜力，并产生更多的氨供AOB硝化。一般来说，当AOB的生长速率（由于氨的存在）大于AOB的失活速率（由于氯胺的存在）时，就会发生硝化作用。本研究的具体目标是：1)制定指示硝化潜力的食物与杀菌剂的比率，并评估该比率预测分布系统内各种化学环境中硝化开始时间的能力；2)评价氯胺化配电系统中AOB和亚硝酸盐氧化菌的微生物生态学，并确定从配电系统中分离的代表性菌株对氯胺的耐药性；3)利用模拟模型配电系统中硝化作用的数学模型，将氯胺化配电系统中硝化作用的化学和微生物基础联系起来。硝化潜力指标的发展可以帮助公用事业公司建立标准，以尽量减少硝化事件。此外，评价不同环境条件下的硝化发生情况将为制定硝化控制策略提供相关信息。微生物生态学研究和相关氯胺耐药菌株的分离将为探索消毒剂耐药机制提供手段。＊＊＊

011218 Harrington The objective of this research project is to develop a model integrating the chemical and microbiological phenomena that occur in chloraminated drinking water systems. As chloramines decay, disinfection potential decreases and the ammonia formed by the decay is converted to nitrites by ammonia-oxidizing bacteria (AOB). This causes two problems: first, nitrite is a public health concern and second, nitrite accelerates the decomposition of the chloramine residual, further reducing disinfection potential and creating more ammonia for the AOB to nitrify. In general, nitrification will occur when the growth rate of AOB (due to the presence of ammonia) is larger than the inactivation rate of AOB (due to the presence of chloramines). The specific objectives of this research are to: 1) Develop a food-to-biocide ratio indicative of nitrification potential and evaluate the ability of this ratio to predict the time to onset of nitrification in various chemical environments within the distribution system, 2) Evaluate the microbial ecology of AOB and nitrite-oxidizing bacteria in chloraminated distribution systems and determine the chloramine resistance of representative strains isolated from the distribution systems and 3) Interconnect the chemical and microbiological fundamentals of nitrification in chloraminated distribution systems using a mathematical model that simulates nitrification in model distribution systems. The development of a nitrification potential indicator may help utilities establish criteria to minimize nitrification episodes. Furthermore, the evaluation of the onset of nitrification under different environmental conditions will provide relevant information to formulate strategies for nitrification control. The microbial ecology studies and the isolation of relevant chloramine resistant strains will provide the means to explore the mechanisms of disinfectant resistance. ***