ABSTRACT

ABSTRACT: In regions suffering from water scarcity, domestic greywater can serve as an alternative water source especially for toilet flushing and gardening. However, greywater may be highly polluted posing health and aesthetic risks. Eighteen scenarios were explored, in each at least one greywater stream was excluded and the effects on flow and pollutants loads were studied. Excluding the combined stream of the first 2 stages of the washing machine and dishwasher, and the kitchen sink reduced more than 50% of the organic matter, nutrients and boron. Excluding the bath and shower reduced the faecal coliforms significantly. The realistic penetration ratio in Israel was assessed by two different methods reaching 18-33% nationally in 2023 (equivalent water saving of 30-54 MCM/Y). This water saving is of the same order of magnitude of a medium size seawater desalination plant, but obviously a more sustainable option.