Municipal surface water valorization for clean water recovery and heavy metal removal towards a circular economy

Abstract

Unsustainable urban expansion increases runoff, introducing heavy metals into municipal surface water systems. Despite the need to remove heavy metals from municipal surface water, conventional treatment technologies are ineffective in removing these contaminants. Reverse osmosis (RO) effectively removes emerging contaminants such as ionic matter, but generates concentrate that poses environmental challenges. The circular economy approach can address these issues by valorizing municipal surface water. Therefore, this study evaluates the feasibility of valorizing municipal surface water for clean water production and heavy metal removal using RO and mechanical vapor compression (MVC). When RO was employed to produce clean water, 98 % of ionic contaminants were successfully removed with high water recovery (>90 %). However, operating the community-scale RO system in batch mode led to significant reductions in water flux and operational instability at high recovery due to the limited feed volume and increased concentration. To understand the implications of these operational constraints further, the associated energy consumption and economic costs were systematically evaluated. The high-recovery RO operation reduced MVC energy needs, lowering the specific energy consumption (SEC) of the RO-MVC process to below 2 kWh/m³. This reduction in SEC lowered the unit product cost and increased revenue, particularly in high-income societies, with generation reaching $0.71/m³ at 95 % recovery. Further revenue potential could increase if the social costs of health risks induced by heavy metals and the economic value of the recovered metals are considered.