Collaborative Research: Influence of drinking water chemical composition on biofilm properties and decay of disinfectant residual: an experimental and modeling study

经过供水系统处理和监测的自来水通常被认为是安全的。然而，最近我们赖以保障这一安全的水基础设施发生了几起故障，这突显了更好地了解和监测国家水质的必要性。最近的研究表明，从饮用水处理厂的源头到家庭中的水龙头，水质可能会恶化。这项研究的一个重点是建筑物内的“建筑内管道”，这是供水系统中最不被了解和最不受监控的部分。住宅管道在配水系统中具有最高的表面积与体积比，因此很容易发生管道表面的化学和生物反应。此外，水经常会在细小的管道中滞留数天，导致残留消毒剂活性丧失，并导致管道表面生物膜中病原体的生长。该项目将确定如何减少消毒剂的腐烂、有毒消毒剂副产品的形成以及在室内管道表面生长的生物膜中病原体的生长。这将通过消毒剂的对照实验和对生物膜中存在的微生物进行分子水平的表征来实现。结果将与饮用水行业、自来水监管机构和其他利益相关者共享，以制定确保家庭饮用水安全的最佳管理实践。建议进行系统研究，以了解住宅管道系统如何、何时以及在哪里发生风险。这项研究基于以下假设：(H1)饮用水化学成分控制室内管道生物膜的多孔结构；(H2)这些生物膜特性控制消毒剂在生物膜和水相之间的质量交换，从而控制消毒剂的残留浓度；以及(H3)在饮用水存在的情况下生长的实验室生物膜将具有由这些来源供应的室内管道网络中的生物膜的扩散和反应特性。一个合作研究计划将通过一个多阶段的研究计划来检验这些假设。首先，在PEX和PVC上消毒剂浓度耗尽的停滞条件下的生物质生长，PEX和PVC是常见的自来水管道材料，使用添加了阻垢和/或防腐化学物质的自来水来模拟处理后的饮用水。H1将通过分析生物膜基质的3D多孔结构来测试，该结构基于从这些不同水域生长的生物膜的光学相干断层扫描。将通过药片和管段规模的反应传输实验和建模来量化消毒剂与生物膜的相互作用来测试氢气。在伊利诺伊大学和华盛顿州立大学的建筑规模实验中，将通过量化不同停滞时间下的游离氯衰减和消毒剂副产品的形成来测试H3。这项研究的成功完成将转变我们对住宅管道中生物膜生长和消毒化学的知识，并帮助监管机构和其他利益相关者更好地管理供水系统，以保护人类健康。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Tap water treated and monitored by the water distribution system has generally thought to be safe. However, several recent failures of water infrastructure that we rely on for this safety have highlighted the need to better understand and monitor the Nation's water quality. Recent research has shown that water quality can deteriorate from the source at the drinking water treatment plant to the taps in homes. A focus of this research is on in-building "premise plumbing", the least understood and monitored part of the water distribution system. Premise plumbing has the highest surface-to-volume ratios in the distribution system, making it susceptible to pipe surface chemical and biological reactions. In addition, water can often sit stagnant in small pipes for days, resulting in loss of residual disinfectant activity and resulting pathogen growth in pipe surface biofilms. This project will determine how to reduce the decay of disinfectant, the formation of toxic disinfectant byproducts, and the growth of pathogens in biofilms that grow on premise plumbing surfaces. This will be achieved by controlled experiments with disinfectants and molecular level characterization of the microbes present in the biofilm. Results will be shared with the drinking water industry, water regulators, and other stakeholders to develop best management practices for ensuring the safety of home drinking water.A systematic study is proposed to understand how, when, and where risk occurs in premise plumbing. The research is based on the following hypotheses: (H1) drinking water chemical constituents control the porous structure of premise plumbing biofilms; (H2) these biofilm properties control the mass exchange of disinfectant between the biofilm and bulk aqueous phases and consequently the residual concentrations of disinfectants; and (H3) laboratory biofilms grown in the presence of drinking water will have diffusion and reaction properties of biofilms occurring in premise plumbing networks supplied from those sources. A collaborative research program will test these hypotheses through a multi-stage research program. First, biomass growth under stagnant conditions with depleted disinfectant concentrations on PEX and PVC, common premise plumbing materials using tap water amended with anti-scaling and/or anti-corrosion chemicals to simulate treated drinking water. H1 will be tested by analyzing 3D porous structure of biofilm matrix based on optical coherence tomography of biofilms grown from these different waters. H2 will be tested by quantifying the interaction of disinfectant with biofilm via coupon- and pipe-section scale reactive transport experiments and modeling. H3 will be tested by quantifying free chlorine decay and formation of disinfectant byproducts in building scale experiments at the University of Illinois and Washington State University under different stagnation times. Successful completion of this research will transform our knowledge of biofilm growth and disinfectant chemistry in premise plumbing and help regulators and other stakeholders better manage water supply systems to protect human health.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.