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Resource recovery from reverse osmosis concentrate as a solution to water crisis: A technological assessment
Journal
Sustainable Water: Resources, Management and Challenges
Date Issued
2020-04-24
Author(s)
Nawaz, Tabish
Selvaratnam, Thinesh
Abstract
The rising world population, increasing urbanization, industrialization, and climate change have led to a global water crisis. Reuse of wastewater is essential to address the ongoing water crisis. However, water reuse requires technological, financial and social support. The emerging paradigm of resource recovery is a potential solution to make water reuse feasible and sustainable. Reverse osmosis (RO) concentrate is a waste stream discharged by RO desalination process plants. RO concentrate streams are rich in minerals and salts, which when economically recovered can bring down the cost of desalination and water. RO desalination is also considered crucial for increasing potable water availability. RO concentrate discharge, therefore, is expected to increase, which implies an increased risk of environmental harms posed by its release into the environment. Moreover, minerals/salts recovery from RO concentrate would lead to potential economic gains. In this article, the case for resource recovery from RO concentrate is made. The key material species found in RO concentrate are identified for their recovery and economic potential. The available methods reported in the literature are reviewed for their suitability for resource recovery from RO concentrate. The reviewed methods include chemical precipitation, crystallization, evaporation, membrane-based methods, adsorption/ion-exchange and few miscellaneous methods such as algal methods, and eutectic freeze point crystallization. For recovering high ionic strength species from RO concentrate chemical precipitation, crystallization and membrane-based methods can be useful; trace minerals' recovery can be achieved via ionexchange, adsorption, electrodialysis, and liquid-liquid extraction-based methods. The species that can be profitably recovered include Na, K, Ca, Mg, Rb, In, Cs, Ge, Li, Sr, Br, and U.