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Life cycle assessment (LCA) is a framework that was originally developed to study the impacts of a product on its surroundings throughout its manufacturing, use, and disposal. Increasingly, LCA is being used to study the environmental impacts of processes. For instance, LCA is a useful tool when a manufacturer or operator wants to reduce the overall environmental impacts of the product or process, as well as to highlight the different tradeoffs associated with choices made in manufacturing and operations. In this presentation, the LCA framework will be applied to examples from water supply planning and wastewater management.
Regarding drinking water treatment, a case study was conducted on a saltwater intrusion event that affected a coastal water utility in Florida. The conductivity of the groundwater increased from approximately 500 to 4,000 µS/cm. The possible causes of the saltwater intrusion event were explored, and the steps taken by the water utility to manage the saltwater intrusion were documented. To understand the environmental impact of the saltwater intrusion event on drinking water treatment, the LCA methodology was used, comparing the original water treatment plant with virtual treatment trains that could treat source waters ranging from freshwater to seawater. Specifically, the LCA results showed the change in environmental impacts between chemical-intensive and electricity-intensive processes. As such, an LCA toolbox is proposed; with national and international participation, an LCA toolbox could be used by water utilities as part of the decision-making process when confronting major changes in water quality and treatment.
Regarding wastewater management, a comparative LCA was conducted that focused on the environmental and economic impacts of managing nutrients from urine produced in a residential setting with three different urine management scenarios. Scenario A was combined wastewater collection and conventional centralized treatment. Scenario B was urine source separation and subsequent struvite precipitation with high phosphorus recovery, which requires magnesium inputs to urine. Scenario C was urine source separation and subsequent struvite precipitation with high phosphorus and nitrogen recovery, which requires magnesium and phosphorus inputs to urine. The life cycle impacts evaluated in this study pertained to the hypothetical construction of urine source separating systems in residence halls at the University of Florida, production of potable water used as toilet flush water, operation of decentralized urine treatment, and operation of centralized wastewater treatment. The system boundaries also included fertilizer offsets resulting from the production of urine based struvite fertilizer. Preliminary economic evaluations showed that the three urine management scenarios were relatively equal on a monetary basis, whereas the order of increasing environmental impact was Scenario B < Scenario A < Scenario C. The environmental impact of Scenario A mostly suffered from high electricity use at the drinking water treatment plant to produce toilet flush water and high electricity usage at the centralized wastewater treatment plant, and Scenario C suffered from very high chemical requirements.
This presentation will conclude with thoughts on future research opportunities on the use of LCA as a framework and tool to provide solutions for integrated water management. |