A stochastic model of domestic water consumption and greywater generation in the Al Ain city

A stochastic model of domestic water consumption and
greywater generation in the Al Ain city

The sources of urban water in the United Arab Emirates are groundwater, desalinated water and treated wastewater. About three-quarters of desalinated water are used for irrigation to amenity plantations. Water consumption in major cities varies between 170 and 200 liter per capita per day (Lpcd) in flats and between 270 and 1760 Lpcd in villas. Irrigation to roadside plants, home gardens and to recreation areas has been increasing in the region with the rapid growth of its urban development. Diversification of water sources and water demand reduction are therefore considered two vital tools for the security of urban water supplies. Currently about 98% of municipal wastewater are centrally collected through an efficient sewerage networks and then treated for reuse to provide irrigation to roadside plantations. The treated wastewater is not conveyed to houses because of the necessity of dual reticulation systems. Reuse of greywater (household wastewater except from kitchen and toilet) for non-potable consumptions (gardening and toilet flush) can be an alternative. The objective of this study is to investigate the potential for decentralized (individual houses) harvesting and reuse of greywater in Al Ain city for non-potable consumptions. An attempt has been undertaken to estimate domestic water consumptions and greywater generation in the city. The frequency and water volume of personal water uses (shower, ablution, toothbrush, hand wash, face wash, toilet flush) and family water uses (laundry, dish wash, home clean, car wash, pet wash, gardening) were estimated from 100 homes randomly distributed across the city. Their probability distributions were fitted using the normal, log-normal, gamma and logistic distributions. The estimated average greywater generation rate was found to be 195 Lpcd. For personal water uses, highest consumption was observed in shower, toilet flush and ablution accordingly. About 70% respondents considered greywater can be reused for gardening. Considering the high variability of water uses frequency and time requirements, the probabilistic model is recommended for greywater quantitative analysis.