Greywater reuse for toilet flushing at a university academic and residential building

Abstract

Interest in water reuse is increasing all over the world and particularly in South Africa, because of its potential to supplement scarce freshwater resources in the face of increased demand and aridity. If water reuse is to be implemented, it must be done sustainably. This study: (i) describes the perceptions of beneficiaries before and after greywater reuse (GWR) implementation; (ii) determines the attributes of greywater that were important to beneficiaries when reusing greywater and their willingness to pay for these attributes; and (iii) undertakes an economic analysis of the implemented GWR systems. To this end, two GWR systems for toilet flushing were installed. The first was installed at a university academic building at the University of the Witwatersrand, Johannesburg, and the second at a university residence at the University of Johannesburg. Perceptions highlighted included respondents’ preference to reuse greywater for toilet flushing rather than irrigation, and the greater preference for GWR for toilet flushing expressed for the university academic relative to the university residential building. In sequence, ‘smell’, ‘colour’ and ‘greywater tariff’ emerged as the attributes of greywater that were important to respondents. In terms of payback period, net present value and benefit-cost ratio, both systems generated a net loss and were economically unfeasible.

Keywords: greywater reuse for toilet flushing, perceptions, economics