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Municipal water reuse can contribute to a circular water economy in different contexts and with various treatment trains. This study synthesized information regarding the current technological and regulatory statuses of municipal reuse. It provides process-level information on cost and energy metrics for three potable reuse and one nonpotable reuse case studies using the new Water Techno-economic Assessment Pipe-Parity Platform (WaterTAP3). WaterTAP3 enabled comparisons of cost and energy metrics for different treatment trains and for different alternative water sources consistently with a common platform. A carbon-based treatment train has both a lower calculated levelized cost of water (LCOW) ($0.40/m3) and electricity intensity (0.30 kWh/m3) than a reverse osmosis (RO)-based treatment train ($0.54/m3 and 0.84 kWh/m3). In comparing LCOW and energy intensity for water production from municipal reuse, brackish water, and seawater based on the largest facilities of each type in the United States, municipal reuse had a lower LCOW and electricity than seawater but higher values than for production from brackish water. For a small (2.0 million gallon per day) inland RO-based municipal reuse facility, WaterTAP3 evaluated different deep well injection and zero liquid discharge (ZLD) scenarios for management of RO concentrate. Adding ZLD to a facility that currently allows surface discharge of concentrate would approximately double the LCOW. For all four case studies, LCOW is most sensitive to changes in weighted average cost of capital, on-stream capacity, and plant life. Baseline assessments, pipe parity metrics, and scenario analyses can inform greater observability and understanding of reuse adoption and the potential for cost-effective and energy-efficient reuse.

This study lists material composition data for two concentrating solar power (CSP) plant designs: a molten-salt power tower and a hypothetical parabolic trough plant, both of which employ a molten salt for the heat transfer fluid (HTF) and thermal storage media. The two designs have equivalent generating and thermal energy storage capacities. The material content of the salt-HTF trough plant was approximately 25% lower than a comparably sized conventional oil-HTF parabolic trough plant. The significant reduction in oil, salt, metal, and insulation mass by switching to a salt-HTF design is expected to reduce the capital cost and LCOE for the parabolic trough system. The report relies primarily on data generated through two prior studies undertaken with WorleyParsons Group that estimated the material content of a molten-salt power tower [1] and oil-HTF parabolic trough plants [2]. New analysis is provided with regard to the material composition of the power tower solar field and the sizing of a salt-HTF trough solar field and HTF system. The overall embodied mass of the salt-HTF trough plant was slightly below that of the salt tower design. The similarity in the total mass of the two designs, combined with the inherent similarity in how the two plants would operate, suggests that salt-HTF trough plants could be competitive with molten-salt power towers if the technical hurdles of deploying salt in the solar field can be overcome. The potential cost and complexity of freeze protection and freeze recovery technology are viewed as having the greatest impact on the viability of salt-HTF troughs. The development of acceptable flexible connections that are compatible with molten salt has also been a challenge. CSP plants are composed mainly of steel, glass, concrete and aggregate materials, which are abundantly available from domestic sources. This is true for most locations in the world where CSP plants might be deployed and is an attractive attribute of the technology with regards to its impact on the local economy. In the U.S., we estimate that 90% by mass and 79% by value of the commodity materials utilized in a CSP plant can be supplied by domestic sources.