Life cycle water, energy and cost analysis of multiple water harvesting and management measures for apartment buildings in a Mediterranean climate

Reducing water demand in the building through efficient water fixtures and appliances can decrease annual water and primary energy use by 1 534 kL and 130 GJ, respectively, while saving 530 USD every year. Wastewater treatment requires 230 MJ and costs 0.97 USD per kL of water saved, necessitating subsidies to be competitive. Rainwater and condensate water harvesting cover 4.8% and 1% of the total demand, respectively, but can reduce infrastructure spending, avoid water leakage and reduce urban run-off. Combining all measures reduces mains water supply by up to 75% for 1 MJ/kL saved and zero life cycle cost. Finally, a metered, seasonal and demand-driven water pricing scheme is recommended to better relate building occupants with the intermittent and scarce nature of water around the Mediterranean.