Greywater Recycling Systems in Urban Mixed-Use Regeneration Areas: Economic Analysis and Water Saving Potential

Greywater (GW) recycling for non-potable uses such as toilet flushing is a management strategy to meet urban water demand with substantial water saving. This paper proposes a system that collects GW from residential buildings and recycles it for toilet flushing in both residential and office buildings. The total cost and water saving of standard sanitation technology were compared with 5 other options requiring less or no potable water use in toilets. Scenarios compare: no GW, individual GW, and shared GW systems with and without low-flush appliances. Typical residential and office buildings in urban mixed-use regeneration areas in the UK were used for these analyses. The results implied that constructed wetland treatment technology with standard appliances is more economically and environmentally viable than other scenarios. By increasing the water and wastewater price, shared GW systems with and without low-flush appliances were viable options within highly water efficient domestic and office buildings.