Greywater treatment technologies: a comprehensive review

Concerns about decreasing urban water supplies and environmental degradation caused by existing water infrastructure have prompted research on more resilient and long-term water delivery systems. Greywater reuse has been proposed to expand local water supply portfolios while minimizing stress on existing ecosystems and infrastructure. Researchers have developed several technologies for greywater reusability and recycling. There are three primary treatment technologies for greywater treatment: physical, chemical, and biological. Besides traditional treatment methods, numerous advanced technologies have attracted interest in recent years, like membrane-based technology, improved electrocoagulation, nature-based solutions (constructed wetlands), and solar-based approaches. The cost comparison of existing technologies has also been examined. The current review focuses on the relevance of various technologies and their readiness level, global scenario, risks possibilities and modeling systems for greywater reuse. The issues and hurdles of greywater reuse sustainably have also been evaluated. This in-depth review study will set the basis for future research in greywater reusability. Graphical abstract