Shared Urban Greywater Recycling Systems: Water Resource Savings and Economic Investment

摘要

The water industry is becoming increasingly aware of the risks associated with urban supplies not meeting demands by 2050. Greywater (GW) recycling for non-potable uses (e.g., urinal and toilet flushing) provides an urban water management strategy to help alleviate this risk by reducing main water demands. This paper proposes an innovative cross connected system that collects GW from residential buildings and recycles it for toilet/urinal flushing in both residential and office buildings. The capital cost (CAPEX), operational cost (OPEX) and water saving potential are calculated for individual and shared residential and office buildings in an urban mixed-use regeneration area in the UK, assuming two different treatment processes; a membrane bioreactor (MBR) and a vertical flow constructed wetland (VFCW). The Net Present Value (NPV) method was used to compare the financial performance of each considered scenario, from where it was found that a shared GW recycling system (MBR) was the most economically viable option. The sensitivity of this financial model was assessed, considering four parameters (i.e., water supply and sewerage charges, discount rate(s), service life and improved technological efficiency, e.g., low flush toilets, low shower heads, etc.), from where it was found that shared GW systems performed best in the long-term.