Changes in DBP Speciation with GAC Treatment

Authors:

  • Meric Selbes, Erik Rosenfeldt, Ben Stanford - Hazen and Sawyer
  • Susan Richardson - University of South Carolina
  • R. Scott Summers - CU Boulder
  • Detlef Knappe - NCSU

With more stringent disinfectant/disinfection byproduct rule (D/DBPR), and a potential Stage 3 D/DBPR on the horizon, utilities are evaluating to optimize their current treatment processes for the removal of disinfection byproduct (DBP) precursors. Granular activated carbon (GAC) adsorption has been proven effective for removal of regulated DBP precursors. However, how the speciation of regulated and unregulated DBPs changes during GAC treatment was not well-known until recently. Our recently-completed Water Research Foundation project 4560 “GAC Control of Regulated and Emerging DBPs of Health Concern” has provided significant insight into potential preferential formation of brominated DBPs and other DBPs post-GAC treatment. The goal of this presentation is to discuss some of the key project results from several different pilot- and full-scale applications using GAC adsorption and how GAC treatment impacts regulated and unregulated DBPs.

GAC treatment processes with various source water conditions, oxidation conditions and upstream processes were evaluated. A pilot-scale system was used to evaluate several different optimization strategies for DBP compliance, including preformed DBPs formed during raw water chlorination, among other strategies. Fluorescence measurements coupled with DBP analysis were able to provide insight into how pre-chlorination changes the reactive organic matter as well as the DBPs. Additionally, full-scale GAC treatments have been evaluated at various facilities and at various breakthroughs for both regulated DBPs (trihalomethanes (THMs) and five haloacetic acids (HAA5s)) and emerging DBPs (additional HAAs, halonitromethanes, haloketones, haloacetonitriles, and haloacetamides among others).

This presentation evaluates the results from these GAC installations to provide preliminary insights into how various source water quality conditions and chlorination strategies coupled with GAC optimization strategies may impact DBPs. By quantifying the change in DBP speciation and concentration, this work will provide key information on how GAC use may impact regulated DBPs and what unintended consequences may occur in terms of unregulated DBP formation.

For more information, please contact the author at mselbes@hazenandsawyer.com.

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