Greywater Phytoremediation in Building-Integrated Greenery Systems: A Review

Global water scarcity is mainly due to climate change, population growth, excessive use of water resources and inadequate water management. Alternative sources such as reusing greywater are promising in urban environments. In this context, phytoremediation, the direct use of plants to remove soil and water pollution, could be an encouraging alternative nature-based solution to traditional reuse methods. While constructed wetlands are the most common method for greywater phytoremediation, their limited feasibility in cities makes green roofs and walls a practical urban alternative. This review examines studies conducted over the last 20 years. The combination of greywater treatment through phytoremediation with urban greenery would help close the water cycle as well as make cities more sustainable. However, for this solution to be viable, several challenges must be addressed, including limited roof or wall surface area compared to traditional systems, the precise volume of water to be managed, and the selection of suitable substrates and plants essential for effective phytoremediation. This work reviews the main mechanisms and factors that drive the phytoremediation process in constructed wetlands, and based on this knowledge, delves into the challenges of applying this process to the urban context through green roofs and facades on buildings.