Urban water systems are an example of complex, dynamic human–environment coupled systems which exhibit emergent behaviors that transcend individual scientific disciplines. While previous siloed approaches to water services (i.e., water resources, drinking water, wastewater, and stormwater) have led to great improvements in public health protection, sustainable solutions for a growing global population facing increased resource constraints demand a paradigm shift based on holistic management to maximize the use and recovery of water, energy, nutrients, and materials. The objective of this review paper is to highlight the issues in traditional water systems including water demand and use, centralized configuration, sewer collection systems, characteristics of mixed wastewater, and to explore alternative solutions such as decentralized water systems, fit for purpose and water reuse, natural/green infrastructure, vacuum sewer collection systems, and nutrient/energy recovery. This review also emphasizes a system thinking approach for evaluating alternatives that should include sustainability indicators and metrics such as emergy to assess global system efficiency. An example paradigm shift design for urban water system is presented, not as the recommended solution for all environments, but to emphasize the framework of system-level analysis and the need to visualize water services as an organic whole. When water systems are designed to maximize the resources and optimum efficiency, they are more prevailing and sustainable than siloed management because a system is more than the sum of its parts.
A survey of enteric viruses and indicator bacteria was carried out in eight community water supply sources (four wells and four springs) in East Tennessee. Seven sites derived their water from carbonate aquifers and one from fractured sandstone. Four of the sites were deemed "low-risk" based on prior monitoring of fecal indicators and factors such as presence of thick layers of overlying sediments. The remaining sites were deemed "high-risk." Enteric viruses (enterovirus and reovirus) were detected by cell culture at least once in seven of the eight wells or springs including all but one of the four low-risk sites. Viral RNA, however, was not detected in any of the samples by reverse transcription-polymerase chain reaction. Conventional indicators of microbial contamination (Escherichia coli and total coliform bacteria) were detected together with culturable viruses in seven of nine virus positive samples. Bacteroides, an alternative fecal indicator which has not previously been used in groundwater investigations, was also detected in all but one of the samples containing E. coli or total coliform bacteria, as well as in one sample where viruses were present in the absence of other bacterial indicators. The study highlights some of the challenges involved in surveys of virus occurrence and indicates that culturable enteric viruses in East Tennessee karst aquifers may be more widespread than previously observed in studies of karst aquifers in Pennsylvania (8%), the Ozark region of Missouri (< 1%), or several other states covered in a national microbial water quality survey conducted by the U.S. Environmental Protection Agency (43%).
Urban water and wastewater utilities are striving to improve their environmental and economic performances due to multiple challenges such as increasingly stringent quality criterion, aging infrastructure, constraining financial burden, growing urban population, climate challenges and dwindling resources. Growing needs of holistic assessments of urban water systems are required to identify systems-level cross-domain solutions. This study evaluated the life cycle environmental and economic impacts of urban water and wastewater systems with two utilities in Greater Cincinnati region as a case study. The scope of this study includes the entire urban water and wastewater systems starting from raw water acquisition for drinking water to wastewater treatment and discharge. The detailed process-based life cycle models were developed based on the datasets provided by local water and wastewater utilities. The life cycle assessment indicated that the operation and maintenance of drinking water distribution was a dominating contributor for energy consumption (43%) and global warming potential (41%). Wastewater discharge from the wastewater treatment plant contributed to more than 80% of the total eutrophication potential. The cost analysis determined that labor and maintenance cost (19%) for wastewater collection, and electricity cost (13%) for drinking water distribution were major contributors. Electricity purchased by the utility was the driver for the majority of impact categories assessed with the exception of eutrophication, blue water use, and metal depletion. Infrastructure requirements had a negligible influence on impact results, contributing less than 3% to most categories, with the exception of metal depletion where it led to 68% of total burdens. Sensitivity analysis showed that the life cycle environmental results were more sensitive to the choice of the electricity mixes and electricity consumption than the rest of input parameters such as chemical dosages, and infrastructure life time. This is one of the first comprehensive studies of the whole urban water system using real case data. It elucidates a bigger picture of energy, resource and cost distributions in a typical urban centralized water system. Inherent to a modern city as large population centers, a significant expenditure has to be invested to provide water services function (moving water, treating water/wastewater) in order to avoid human and environmental health problems. This study provides insights for optimization potentials of overall treatment efficiency and can serve as a benchmark for communities considering adoption of alternative water systems.
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