Life cycle assessment of a commercial rainwater harvesting system compared with a municipal water supply system

Abstract

Building upon previously published life cycle assessment (LCA) methodologies, we conducted an LCA of a commercial rainwater harvesting (RWH) system and compared it to a municipal water supply (MWS) system adapted to Washington, D.C. Eleven life cycle impact assessment (LCIA) indicators were assessed, with a functional unit of 1 m3 of rainwater and municipal water delivery system for toilets and urinals in a four-story commercial building with 1000 employees. Our assessment shows that the benchmark commercial RWH system outperforms the MWS system in all categories except Ozone Depletion. Sensitivity and performance analyses revealed pump and pumping energy to be key components for most categories, which further guides LCIA tradeoff analysis with respect to energy intensities. Tradeoff analysis revealed that commercial RWH performed better than MWS in Ozone Depletion if RWH’s energy intensity was less than that of MWS by at least 0.86 kWh/m3 (249% of the benchmark MWS energy usage at 0.35 kWh/m3). RWH also outperformed MWS in Metal Depletion and Freshwater Withdrawal, regardless of energy intensities, up to 5.51 kWh/m3. An auxiliary commercial RWH system with 50% MWS reduced Ozone Depletion by 19% but showed an increase in all other impacts, which were still lower than benchmark MWS system impacts. Current models are transferrable to commercial RWH installations at other locations.

A City Wide Assessment of the Financial Benefits of Rainwater Harvesting in Mexico City

“…For potable uses (all indoor uses except drinking) the treatment equipment considered were a first flush filter, a leaf filter, a 20 micron sediment filter, an activated carbon filter, a 5 micron sediment filter, and chlorination. Other disinfection features such as silver ions (Adler et al ) and UV (Ghimire et al ; Leong et al ) were explored but from the treatment costs elicited from Mexican suppliers, chlorination was still the most economical. However, it is known that chlorination has other downsides, such as the formation of toxic disinfection by‐products and the risks from incorrect dosing (Nieuwenhuijsen et al ).…”

Combining Hydrologic Analysis and Life Cycle Assessment Approaches to Evaluate Sustainability of Water Infrastructure: Uncertainty Analysis

“…The LCA has four steps: outlining the goal and scope of the analysis (described in Section 2.1), gathering the data needed for all life cycle stages to create a life cycle inventory (LCI), quantifying the impacts via life cycle impact assessment (LCIA) methods, and interpreting the results. In LCA studies of water and wastewater treatment plants, 1 m 3 of treated water [63][64][65][66] or wastewater [28,67] is often used as the Functional Unit (FU). The drainage area has been used as the functional unit in prior watershed scale LCAs [12,13].…”

Rainwater Harvesting in Buildings in Brazil: A Literature Review

“…According to Ghimire et al [65], implementation of rainwater systems continues to be a challenge, mainly due to a lack of understanding of their environmental and human health impacts (material selection criteria and energy use) and partly due to a lack of regulations to which systems are governed. To prove the effectiveness of the systems in minimizing environmental impacts, it is necessary to use evaluation tools, allowing the benefits to be analysed holistically.…”