Towards a Sustainable Residential Hot Water Infrastructure: Optimizing Public Health, Water Savings, and Energy Goals

1336650（Pruden）。住宅热水基础设施是水，能源和公共卫生的关键联系。在美国，其能源需求总量超过了水和废水公用事业部门的总和，而建筑管道系统（特别是热水）现在是水传播疾病爆发的主要来源。特别是，嗜肺军团菌，非结核分枝杆菌，铜绿假单胞菌和阿米巴特别具有挑战性，因为它们在热水分配系统本身内建立和生长。不幸的是，目前缺乏实际的研究来指导合理选择最佳的热水系统。因此，拟议研究的总体目标是通过对公共卫生，节水，能源目标和整体系统脆弱性方面的性能进行首次综合评估，来促进我们的住宅热水基础设施的可持续性。三个具体的研究目标（O 1-O3）是：O 1。对标准、循环和按需热水器配置在一系列温度和水需求下进行受控的头对头研究，并比较它们在能耗和水的微生物质量方面的性能; O2.检查不同的水化学，管道材料和热水器配置对结垢，腐蚀，能量损失和水的微生物质量的相互作用;和O3。开发一个多标准决策分析工具，以确定特定情况下最具可持续性的配置，同时考虑到消费者在执行方面的障碍。 尽管美国总能源需求的3.3-5.5%用于住宅热水系统，并且这种系统现在是水传播疾病爆发的主要来源，但在选择最佳热水器所需的基础知识方面存在着重大差距。将对三种有代表性的热水器配置所产生的水和能源需求进行广泛的头对头比较。下一代DNA测序工具的应用将为热水器对病原体和更广泛的微生物生态学的影响提供真正的开创性理解。初步结果表明，氢营养细菌可能利用镁阳极产生的氢（常见于水箱加热器，以减少腐蚀），反过来，固定和释放有害水平的有机碳到水中。其他初步结果表明，铜可能具有抑制军团菌的有益特性。虽然这项研究的重点是电力能源作为重要的第一步，但所获得的基本理解，如温度分层的影响，缩放和管道组件的作用，可以很容易地外推到其他能源。最佳的热水器可能会根据各种当地限制而变化。虽然按需预计具有最低的初始水和能量需求，以及最小的病原体扩增潜力，但在高结垢潜力的沃茨中，它不太可能是一个可行的选择。所有操作条件对消毒剂残留水平的影响，是抵抗病原体的关键保护屏障，也将是整体性能评价的重要因素。有什么证据表明？绿色？建议可能会产生误导性的政策，对水能源消费和公共卫生产生长期的负面影响。这项研究寻求基础知识和整体视角，以支持消费者，公共卫生官员和监管机构选择最佳热水系统的理性决策。考虑到性能的多个方面的科学合理的建议是必要的，以实现真正的可持续水系统。拟议的努力包括一个重要的社会科学组成部分和可持续性排名的方法，以支持多标准决策工具的发展。研究结果将在公共网站上公布，在绿色建筑和水工程会议上介绍，并发表在同行评议的文献中。该项目还将支持三名研究生，他们将参加Water Interface跨学科研究生教育计划，并将接受绿色工程、水化学和环境微生物学等领域的培训。本科研究人员也将通过跨学科水科学和工程NSF REU网站参与。

1336650 (Pruden). Residential hot water infrastructure is a critical nexus of water, energy, and public health. In the U.S., its total energy demand exceeds that of the water and wastewater utility sectors combined, while building plumbing systems (especially hot water) are now the primary source of waterborne disease outbreak. In particular, Legionella pneumophila, non-tuberculosis mycobacteria, Pseudomonas aeruginosa, and Acanthamoeba are especially challenging because they establish and grow within the hot water distribution system itself. Unfortunately, there is currently a void of practical research to guide rational selection of optimal hot water systems. Thus, the overall goal of the proposed research is to advance sustainability of our residential hot water infrastructure by conducting the first integrated assessment of performance in terms of public health, water savings, energy goals, and overall system vulnerabilities. Three specific research Objectives (O1-O3) are: O1. Conduct a controlled, head-to-head study of standard, recirculating, and on-demand water heater configurations over a range of temperatures and water demands and compare their performance in terms of energy consumption and microbial quality of the water; O2. Examine the interplay of varying water chemistries, pipe materials, and water heater configuration on scaling, corrosion, energy loss, and microbial quality of the water; and O3. Develop a multi-criteria decision analysis tool to identify the most sustainable configuration(s) for a specific context, with consideration of consumer barriers to implementation. Although 3.3-5.5% of total U.S. energy demand is used in residential water heating systems, and such systems are now the primary source of waterborne disease outbreak, there exists a critical gap in fundamental knowledge needed to select an optimal water heater. Extensive head-to-head comparisons will be made of water and energy demands incurred by three representative water heater configurations. Application of next-generation DNA sequencing tools will provide a truly pioneering understanding of water heater impacts on pathogens and the broader microbial ecology. Preliminary results suggest that hydrogenotrophic bacteria may utilize hydrogen produced by magnesium anodes (common in tank heaters to reduce corrosion) and, in turn, fix and release detrimental levels of organic carbon into the water. Other preliminary results indicate that copper may possess beneficial properties for inhibiting Legionella. While this research focuses on electric energy sources as an important first step, the fundamental understanding gained, such as effects of temperature stratification, scaling, and roles of plumbing components, can be readily extrapolated to other energy sources. The optimal water heater is likely to vary based on a variety of local constraints. Although on-demand is expected to have the lowest initial water and energy demands, and the least potential for pathogen amplification, it is not likely to be a feasible option in waters of high scaling potential. Effects of all operating conditions on disinfectant residual levels, a critical protective barrier against pathogens, will also be a vital factor for overall performance evaluation. Evidence is mounting that existing ?green? advice may be creating misguided policy with long-term negative repercussions on water-energy consumption and public health. This research seeks fundamental knowledge and a holistic perspective to support rational decision-making by consumers, public health officials, and regulators on selection of optimal hot water systems. Scientifically-defensible recommendations considering multiple dimensions of performance are necessary to achieve truly sustainable water systems. The proposed effort incorporates a significant social science component and sustainability ranking approach in support of the development of a multi-criteria decision making tool. Results will be available on public websites, presented at green building and water engineering conferences, and published in the peer-reviewed literature. The project will also support three graduate students, who will participate in the Water INTERface Interdisciplinary Graduate Education Program and will be trained across fields of green engineering, water chemistry, and environmental microbiology. Undergraduate researchers will also participate through the Interdisciplinary Water Science and Engineering NSF REU site.