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NEWR: A Planning Tool for Estimating the Environmental and Economic Suitability of Onsite Non-potable Water Reuse Systems for Large Buildings
Citation:
Arden, S., B. Morelli, S. Cashman, Cissy Ma, M. Jahne, AND J. Garland. NEWR: A Planning Tool for Estimating the Environmental and Economic Suitability of Onsite Non-potable Water Reuse Systems for Large Buildings. American Center for Life Cycle Assessment (ACLCA), Madison,WI, September 22 - 24, 2020.
Impact/Purpose:
This web application provides a tool that allows users to generate planning-level estimates of system cost and environmental performance using ZIP Code and their own building characteristics as inputs to evaluate NPR system options – rainwater harvesting (RWH), air-conditioning condensate harvesting (ACH), and source-separated graywater and mixed wastewater membrane bioreactors (GWMBR, WWMBR).
Description:
Onsite non-potable reuse (NPR) is a way for buildings to conserve water and rely on locally available source waters for services such as toilet flushing, laundry and irrigation. Although previous studies have investigated the life cycle performance of case study NPR systems, aspects like system suitability, cost and environmental performance remain difficult to quantify across broad geographic contexts given the variability in climate conditions and configurations. In this study, we evaluate four NPR system options – rainwater harvesting (RWH), air-conditioning condensate harvesting (ACH), and source-separated graywater and mixed wastewater membrane bioreactors (GWMBR, WWMBR) – in terms of their ability to satisfy onsite non-potable demand, their environmental impacts and their economic cost, all as a function of building characteristics and location in the U.S. To complete the analysis, we developed the Non-potable Environmental and Economic Water Reuse Calculator (NEWR), a publicly available U.S. EPA web application that allows users to generate planning-level estimates of system cost and environmental performance using ZIP Code and their own building characteristics as inputs. We ran simulations of NEWR across U.S. ZIP Codes for a set large building type and a random selection of building characteristics. We find that, across the U.S., rainfall and air-conditioner condensation are only able to satisfy a fraction of the non-potable demand typical of large buildings even under favorable climate conditions. Environmental impacts of RWH and ACH systems also depend on local climate and were found to be competitive to MBRs only where annual rainfall exceeds approximately 10 in/yr or annual condensation potential exceeds approximately 3 gal/cfm. MBRs can meet all non-potable demands but their environmental impacts depend on the composition of the local energy grid, owing to their greater reliance on electricity inputs. Incorporation of thermal recovery to offset building hot water heating requirements amplifies this dependence, with mixed results depending on grid composition and whether thermal recovery offsets natural gas or electricity consumption. Additional environmental benefits are realized when NPR systems are implemented in regions with diverse topography and regions relying on groundwater sources, which amplify the benefits of decreasing reliance on centralized drinking water services. WWMBRs were found to be the most cost-competitive, though achieved cost parity with local drinking water rates in only 10% of surveyed cities.