Evaluating the potential of improving residential water balance at building scale

Earlier results indicated that, for an average household, self-sufficiency inwater supply can be achieved by following the Urban harvest Approach (UHA), in a combination of demand minimization, cascading and multi-sourcing. To achieve these results, it was assumed that all available local resources can be harvested. In reality, however, temporal, spatial and locationbound factors pose limitations to this harvest and, thus, to self-sufficiency. This article investigates potential spatial and temporal limitations to harvest local water resources at building level for the Netherlands, with a focus on indoor demand. Two building types were studied, a free standing house (one four-people household) and a mid-rise apartment flat (28 two-person households). To be able tomodel yearlywater balances, daily patterns considering household occupancy and presence ofwater using applianceswere defined per building type. Three strategies were defined. The strategies include demand minimization, light grey water (LGW) recycling,andrainwaterharvesting(multi-sourcing).Recyclingandmulti-sourcingcater for toilet flushing and laundrymachine. Results showed thatwater saving devicesmay reduce 30% of the conventional demand. Recycling of LGWcan supply 100% of second quality water (DQ2)whichrepresents36%of theconventionaldemandorupto20%of theminimizeddemand. Rainwater harvestingmay supply approximately 80%of theminimized demand in case of the apartmentflat and 60%in case of the free standinghouse.Toharvest these potentials, different system specifications, related to the household type, are required. Two constraints to recycle and multi-source were identified, namely i) limitations in the grey water production and availablerainfall;andii) thepotential toharvestwaterasdeterminedbythe temporalpatternin water availability, water use, and storage and treatment capacities.