Economic feasibility of on-site greywater reuse in multi-storey buildings

This paper analyses the economic feasibility of on-site greywater reuse in the urban sector. RBC- and MBR-based systems were selected as model systems for the economic analysis. The analysis showed that the investment costs of an RBC-based system consist of less than 0.5% of the price of a flat for buildings of more than 20 flats (five storeys). At a water price of 1.16 US$/m3 and sewage charges of 0.3 US$/m3, the RBC-based system became economically feasible when the building size reached seven storeys (28 flats). The on-site MBR-based system proved to be economically unrealistic, becoming economically feasible only when the building size exceeded 40 storeys. Cluster MBR-based systems, incorporating several buildings together, became feasible when the cluster size was four buildings or more (each 10 storeys high). A subsidy of 0.7 US$/m3reused resulted in much smaller systems becoming economically feasible: four-storey buildings (16 flats) for the RBC system and two buildings for the cluster MBR system. The on-site MBR system (single building) remained unfeasible.