Measuring environmental sustainability of water in watersheds

Effect of Nutrient Removal and Resource Recovery on Life Cycle Cost and Environmental Impacts of a Small Scale Water Resource Recovery Facility

To limit effluent impacts on eutrophication in receiving waterbodies, a small community water resource recovery facility (WRRF) upgraded their conventional activated sludge treatment process for biological nutrient removal, and considered enhanced primary settling and anaerobic digestion (AD) with co-digestion of high strength organic waste (HSOW). The community initiated the resource recovery hub concept with the intention of converting an energy-consuming wastewater treatment plant into a facility that generates energy and nutrients and reuses water. We applied life cycle assessment and life cycle cost assessment to evaluate the net impact of the potential conversion. The upgraded WRRF reduced eutrophication impacts by 40 percent compared to the legacy system. Other environmental impacts such as global climate change potential (GCCP) and cumulative energy demand (CED) were strongly affected by AD and composting assumptions. The scenario analysis showed that HSOW co-digestion with energy recovery can lead to reductions in GCCP and CED of 7 and 108 percent, respectively, for the upgraded WRRF (high feedstock-base AD performance scenarios) relative to the legacy system. The cost analysis showed that using the full digester capacity and achieving high digester performance can reduce the life cycle cost of WRRF upgrades by 15 percent over a 30-year period.

Freshwater Vulnerability beyond Local Water Stress: Heterogeneous Effects of Water-Electricity Nexus Across the Continental United States

Human health and economic prosperity are vulnerable to freshwater shortage in many parts of the world. Despite a growing literature that examines the freshwater vulnerability in various spatiotemporal contexts, existing knowledge has been conventionally constrained by a territorial perspective. On the basis of spatial analyses of monthly water and electricity flows across 2110 watersheds and three interconnected power systems, this study investigates the water-electricity nexus (WEN)'s transboundary effects on freshwater vulnerability in the continental United States in 2014. The effects are shown to be considerable and heterogeneous across time and space. For at least one month a year, 58 million people living in water-abundant watersheds were exposed to additional freshwater vulnerability by relying on electricity generated by freshwater-cooled thermal energy conversion cycles in highly stressed watersheds; for 72 million people living in highly stressed watersheds, their freshwater vulnerability was mitigated by using imported electricity generated in water-abundant watersheds or power plants running dry cooling or using nonfreshwater for cooling purposes. On the country scale, the mitigation effects were the most significant during September and October, while the additional freshwater vulnerability was more significant in February, March, and December. Due to the WEN's transboundary effects, overall, the freshwater vulnerability was slightly worsened within the Eastern Interconnection, substantially improved within the Western Interconnection, and least affected within the ERCOT Interconnection.

The Emergy Perspective of Sustainable Trends in Puerto Rico from 1960 to 2013

Emergy analysis quantifies the direct and indirect contributions of nature to human systems providing a sustainability assessment framework, which couples economic growth within biophysical constraints. In this study, Puerto Rico's sustainability was assessed with emergy flow dynamics from 1960 to 2013. During this period, the island shifted from an agriculture-based economy to an industrial base of manufacture and services (1960-1970). The emergy analysis indicated an exponential decline in sustainability during this period. From 1975 to 1992, the island became more industrialized and imported more goods and services. Since 1998, although more renewable production such as forest regeneration occurred, the rapid industrialization heavily relied on imported fossil fuels, goods, and services, resulting in a system that has not been self-sufficient, nor sustainable. The latest economic crisis and the most recently passed financial rescue bill represent an opportunity to redirect Puerto Rico towards a sustainable path with policies that decrease the ratio of imported y to exported emergy, and strategies that encourage efficient use of resources and local production based on the utilization of renewable sources within this U.S. territory.

Assessing the sustainability of freshwater systems: A critical review of composite indicators

Quantitative indicators are a common means of assessing the complex dimensions of a sustainable freshwater system, and framing scientific knowledge for policy and decision makers. There is an abundance of indicators in use, but considerable variation in terms of what is being measured and how indicators are applied, making it difficult for end-users to identify suitable assessment methods. We review 95 water-related indices and analyze them along their normative, procedural, and systemic dimensions to better understand how problems are being defined, highlight overlaps and differences, and identify the context(s) in which a particular index is useful. We also analyze the intended use, end-users, and geographic scale of application for each index. We find that risk assessment is the most common application (n = 25), with indices in this group typically focusing either on hazard identification (biophysical assessments) or vulnerability of human populations. Indices that measure freshwater ecological health are not explicitly linking these indicators to ecosystem services, and in fact the concept of ecosystem services is rarely (n = 3) used for indicator selection. Resource managers are the most common group of intended end-users (n = 25), but while 28 indices involved consultation with potential end-users, 11 did not specify an intended use. We conclude that indices can be applied as solution-oriented tools, evaluating scenarios and identifying tradeoffs among services and beneficiaries, rather than only assessing and monitoring existing conditions. Finally, earlier engagement of end-users is recommended to help researchers find the right balance among indices' salience, legitimacy, and credibility and thus improve their decision relevance.

Assessing and Enhancing Environmental Sustainability: A Conceptual Review

While sustainability is an essential concept to ensure the future of humanity and the integrity of the resources and ecosystems on which we depend, identifying a comprehensive yet realistic way to assess and enhance sustainability may be one of the most difficult challenges of our time. We review the primary environmental sustainability assessment approaches, categorizing them as either being design-based or those that employ computational frameworks and/or indicators. We also briefly review approaches used for assessing economic and social sustainability because sustainability necessitates integrating environmental, economic, and social elements. We identify the collective limitations of the existing assessment approaches, showing that there is not a consistent definition of sustainability, that the approaches are generally not comprehensive and are subject to unintended consequences, that there is little to no connection between bottom-up and top-down approaches, and that the field of sustainability is largely fragmented, with a range of academic disciplines and professional organizations pursuing similar goals, but without much formal coordination. We conclude by emphasizing the need for a comprehensive definition of sustainability (that integrates environmental, economic, and social aspects) with a unified system-of-systems approach that is causal, modular, tiered, and scalable, as well as new educational and organizational structures to improve systems-level interdisciplinary integration.