Department of Chemical Engineering and Material Sciences, University of California, Henry Samueli School of Engineering, University of California, Irvine, CA 92697, USA.
Water Res. 2011 Nov 1;45(17):5641-53. doi: 10.1016/j.watres.2011.08.020. Epub 2011 Aug 22.
Sewage-contaminated shallow groundwater is a potential cause of beach closures and water quality impairment in marine coastal communities. In this study we set out to evaluate the feasibility of several strategies for disinfecting sewage-contaminated shallow groundwater before it reaches the coastline. The disinfection rates of Escherichia coli (EC) and enterococci bacteria (ENT) were measured in mixtures of raw sewage and brackish shallow groundwater collected from a coastal community in southern California. Different disinfection strategies were explored, ranging from benign (aeration alone, and aeration with addition of brine) to aggressive (chemical disinfectants peracetic acid (PAA) or peroxymonosulfate (Oxone)). Aeration alone and aeration with brine did not significantly reduce the concentration of EC and ENT after 6 h of exposure, while 4-5 mg L(-1) of PAA or Oxone achieved >3 log reduction after 15 min of exposure. Oxone disinfection was more rapid at higher salinities, most likely due to the formation of secondary oxidants (e.g., bromine and chlorine) that make this disinfectant inappropriate for marine applications. Using a Lagrangian modeling framework, we identify several factors that could influence the performance of in-situ disinfection with PAA, including the potential for bacterial regrowth, and the non-linear dependence of disinfection rate upon the residence time of water in the shallow groundwater. The data and analysis presented in this paper provide a framework for evaluating the feasibility of in-situ disinfection of shallow groundwater, and elucidate several topics that warrant further investigation.
受污水污染的浅层地下水是导致滨海社区海滩关闭和水质受损的一个潜在原因。在本研究中，我们旨在评估在污水到达海岸线之前对其进行消毒的几种策略的可行性。我们测量了从加利福尼亚州南部沿海社区采集的污水和微咸水的混合物中大肠杆菌（EC）和肠球菌（ENT）的消毒率。我们探讨了不同的消毒策略，范围从良性（单独曝气和曝气加盐水）到激进（过乙酸（PAA）或过一硫酸盐（Oxone）等化学消毒剂）。单独曝气和曝气加盐水在暴露 6 小时后，并没有显著降低 EC 和 ENT 的浓度，而 4-5 mg/L 的 PAA 或 Oxone 在暴露 15 分钟后即可实现 >3 对数减少。Oxone 在较高盐度下的消毒速度更快，这很可能是由于形成了次级氧化剂（例如溴和氯），这使得这种消毒剂不适合海洋应用。我们使用拉格朗日模型框架，确定了几个可能影响 PAA 原位消毒性能的因素，包括细菌再生的可能性，以及消毒速率与水在浅层地下水中的停留时间之间的非线性关系。本文提供的数据分析框架为评估浅层地下水原位消毒的可行性提供了依据，并阐明了几个值得进一步研究的主题。
