Evaluating the performance of a decentralized graywater treatment system in a living building at Hampshire College, Amherst, MA, USA.

Abstract

Decentralized graywater treatment systems are growing in popularity as the threat of water scarcity rises and wastewater's potential as a resource is recognized. In 2016, Hampshire College in Amherst, Massachusetts, completed construction of the R.W. Kern Center, a Living Building that incorporates physical filters and two constructed wetlands to treat graywater produced on-site. Grab samples of graywater were collected from four sites between August 2016 and March 2019. This study characterizes mixed graywater from all the building's fixtures and graywater from a coffee bar. Untreated mixed graywater was observed with median concentrations of 180mg/L for total suspended solids (TSS), 190mg/L for biochemical oxygen demand (BOD5 ), and 15mg/L for total nitrogen (TN), primarily in the form of total Kjeldahl nitrogen (TKN). Concentrations of TSS, BOD5 , and TN were reduced by 92%, 96%, and 73%, respectively, by the Kern Center's treatment system. Preliminary data from coffee bar effluent establish a wide range of high-strength graywater quality. Because Living Buildings by design explore the connections between people and their builtenvironments, this study also found that the behaviors of building occupants, particularly the café staff, had a direct impact on the functioning of the Kern Center's decentralizedgraywater treatment system. PRACTITIONER POINTS: On-site decentralized graywater treatment systems paired with waterless composting toilets are effective in reducing a building's water use and inmeeting net-zero water goals. Constructed wetlands can effectively treat graywater produced in acentral campus building with public spaces, office spaces, and a coffee bar. On-site decentralizedgraywater treatment systems require cooperation from bothbuilding occupants and water operators in order to function properly.