Forecasting clearwater supply for non-potable uses in buildings

a literature review

Abstract

According to the Brazilian Association of Technical Standards, the term ‘clearwater’ refers to effluents generated from thermal systems (cooling and heating) or from laboratory water purification systems (such as distillation and reverse osmosis). Given its low turbidity and minimal concentrations of organic matter, clearwater might serve as a viable alternative water source for non-potable end-uses in buildings. The aim of this study was to identify potential sources of clearwater and systematize the existing methods for forecasting clearwater supply for non-potable uses in buildings through a narrative and cumulative literature review. Overall, clearwater can be classified into two main categories: i) clearwater discharge, from laboratory water treatment processes such as water stills or haemodialysis reverse osmosis systems; and ii) clearwater condensate, produced by air-conditioning or boiler systems. Findings indicate a lack of standardized and validated methods for forecasting clearwater supply from reverse osmosis, distillation, air-conditioning and boiler systems, which constrains their practical integration into non-potable water systems. Even though results suggest that clearwater presents promising opportunities for non-potable uses, their application is limited by insufficient empirical data and the lack of validated forecasting approaches. By systematizing existing knowledge and identifying critical research gaps, this review provides technical insights to support the improvement of building-scale water management systems and to promote more sustainable use of water resources.