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The widespread and successful use of coagulation, ozonation, biofiltration, and granular activated carbon (GAC) adsorption for the treatment of impaired drinking water sources makes them attractive as an economical approach for direct potable reuse. This study systematically evaluated these processes for the treatment of four secondary wastewater effluents with the objective of meeting U.S. drinking water disinfection byproduct (DBP) regulations and developing treatment objectives. Total trihalomethane (TTHM) and the sum of five haloacetic acids (HAA5) targets of 60 and 50 μg/L, respectively, were developed under uniform formation conditions and were related to a target total organic carbon (TOC) concentration of 2 mg/L. Ozonation, followed by biofiltration, was effective in decreasing HAA5 formation to below the target levels, but GAC treatment was needed to meet the target TTHM and TOC levels. Optimizing the TOC removal before GAC treatment extended the GAC run times similarily to those found in drinking water treatment. Drinking water–based DBP formation algorithms were very effective in predicting TTHM and HAA5 formation.

Disinfection byproduct (DBP) pre-formation is a major issue when prechlorination is used before or during advanced treatment of impacted drinking water sources. Control strategies for pre-formed DBPs before final disinfection, especially for currently nonregulated although highly toxic DBP species, are not yet established. This study evaluated the biodegradation potential of pre-formed DBPs, including haloacetonitriles (HANs), haloacetamides (HAMs), and haloacetaldehydes (HALs), during biofiltration with sand, anthracite, and biological activated carbon of three wastewater effluents under potable reuse conditions. Up to 90%+ removal of di- and trihalogenated HANs, HAMs, and HALs was observed, and removal was associated with active heterotrophic biomass and removal of biodegradable organic carbon. Unlike the microbial dehalogenation pathway of haloacetic acids (HAAs), removal of HANs and HAMs appeared to result from a biologically mediated hydrolysis pathway (i.e., HANs to HAMs and HAAs) that may be prone to inhibition. After prechlorination, biofiltration effectively controlled pre-formed DBP concentrations (e.g., from 271 μg/L to as low as 22 μg/L in total) and DBP-associated calculated toxicity (e.g., 96%+ reduction). Abiotic residual adsorption capacity in biological activated carbon media was important for controlling trihalomethanes. Overall, the toxicity-driving DBP species exhibited high biodegradation potential and biofiltration showed significant promise as a pre-formed DBP control technology.