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

1336650(普鲁登)。住宅热水基础设施是水、能源和公共卫生的重要纽带。在美国，它的总能源需求超过了供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)现在是水源性疾病爆发的主要来源。特别是，嗜肺军团菌、非结核分枝杆菌、铜绿假单胞菌和棘阿米巴尤其具有挑战性，因为它们在热水分配系统本身内建立和生长。遗憾的是，目前还缺乏指导合理选择最佳热水系统的实用研究。因此，拟议研究的总体目标是通过在公共健康、节水、能源目标和整体系统脆弱性方面进行第一次综合绩效评估，促进我们住宅热水基础设施的可持续性。三个具体的研究目标(O1-O3)是：O1。在一定的温度和用水需求范围内，对标准、循环和按需热水器的配置进行可控的、正面的研究，并从能耗和水的微生物质量方面比较它们的性能。检查不同的水化学成分、管道材料和热水器配置对水的结垢、腐蚀、能量损失和微生物质量的相互影响；以及臭氧。开发多标准决策分析工具，以确定特定环境下最可持续的配置(S)，并考虑消费者实施的障碍。尽管美国总能源需求的3.3%-5.5%用于住宅热水系统，这类系统现在是水媒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严重缺口。将对三种具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正面比较。下一代DNA测序工具的应用将真正开创性地了解热水器对病原体和更广泛的微生物生态的影响。初步结果表明，氢遗传营养细菌可能会利用镁阳极产生的氢(在坦克加热器中很常见，以减少腐蚀)，进而固定并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。虽然这项研究将重点放在电力能源上，作为重要的第一步，但所获得的基本理解，如温度分层、结垢和管道部件的作用，可以很容易地推断到其他能源。最优热水器可能会根据各种局部约束条件而有所不同。尽管On-Demand预计具有最低的初始水和能量需求，以及最小的病原体放大潜力，但在高结垢潜力的水域中，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也将是整体性能评估的重要因素。消毒剂残留水平是抵御病原体的关键保护屏障。有越来越多的证据表明存在吗？绿色？建议可能会产生误导性的政策，对水、能源消耗和公共健康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在选择最佳热水系统方面的理性决策。为了实现真正可持续的水系统，考虑到绩效的多个方面，有科学依据的建议是必要的。拟议的努力纳入了一个重要的社会科学部分和可持续性排名方法，以支持开发多标准决策工具。结果将在公共网站上公布，在绿色建筑和水利工程会议上公布，并在同行评议的文献中发表。该项目还将支持三名研究生，他们将参加水界面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领域的培训。本科生研究人员还将通过NSF REU跨学科水科学与工程网站参与。

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.