Organic, Inorganic, and Biological Contaminant Occurrence and Removal in a Carbon-Based Potable Water Reuse Mobile Demonstration System

Direct potable reuse (DPR) might become a critical water source for communities facing water scarcity. Due to the impaired source water used for DPR, it is critical to demonstrate that contaminant concentrations in the finished water meet the standards in relevant regulations. In this research we monitored the concentrations of disinfection byproducts (DBPs) and other organic contaminants, poly- and per-fluoroalkyl substances (PFAS), metals, and pathogens over a five-month period through a demonstration-scale DPR treatment train (ozone/biologically active carbon/microfiltration/granular activated carbon (GAC)/ultraviolet light with advanced oxidation/disinfection). The treatment train reduced all regulated contaminants to concentrations below regulatory standards and removed most unregulated contaminants below detection. The concentrations of some organic contaminants in the finished water, such as PFAS, increased over time as the adsorptive capacity of the GAC decreased. Disinfection byproduct formation was minimal, and those formed during ozonation were removed during subsequent treatment. The concentrations of inorganic contaminants were within regulated limits throughout the treatment train. Pathogens were consistently detected in the influent but not in the finished water. The results demonstrated that a GAC-based DPR treatment train, as an alternative to reverse osmosis-based DPR, can reliably mitigate the risk of chemical and microbial contaminants.