Control of Effluent Organic Matter and Disinfection Byproducts with Biofiltration for Potable Reuse

Peterson, Eric S.

Graduate Thesis Or Dissertation

Control of Effluent Organic Matter and Disinfection Byproducts with Biofiltration for Potable Reuse Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/mk61rj272

Abstract

Water scarcity is driving an increasing need for potable reuse of municipal wastewater effluent, but appropriate and affordable treatment is not well-established. Carbon-based advanced treatment (CBAT) with ozone, biofiltration, and granular activated carbon is a cost-effective advanced treatment alternative, but adoption is hindered by knowledge gaps regarding control of disinfection byproducts (DBPs). DBPs form through unintended reactions between chemical disinfectants and dissolved organic matter. Many unregulated DBPs, especially brominated and nitrogenous species, are more toxic at lower concentrations than regulated DBPs and have high formation potential in wastewater effluent. This dissertation’s objective was to systematically evaluate the potential for biofiltration, in combination with other CBAT processes, to remove wastewater effluent organic matter (EfOM) and control regulated and unregulated DBPs in potable reuse water. In the first study, a biofiltration model was developed from a meta-analysis of 42 wastewater effluents. It describes the impact of operational conditions on EfOM removal; up to 40% removal can typically be achieved biologically by using pre-ozonation, longer empty bed contact times, and biological activated carbon media. Next, filter bioactivity was quantified and found to be impacted by EfOM character and filter operation, and to follow a strong pseudo-first order relationship with biodegradable EfOM removal. In the second study, experimental evaluation of EfOM removal using biofiltration and other CBAT processes showed lower DBP-associated toxicity, achieved by preferential removal of DBP precursors within EfOM despite a concurrent shift towards more-toxic brominated species. That tradeoff was then evaluated by developing and applying a quantitative toxicity-based DBP speciation metric. In the third study, experimental evaluation of pre-formed DBP removal using biofiltration showed significant removal (>80%) from pre-chlorinated wastewater effluents, especially when EfOM removal was high. The biodegradation potential of pre-formed haloacetonitriles, haloacetamides, and haloacetaldehydes was identified and found to be related to EfOM but not ammonia removal (heterotrophic primary substrate utilization). Further, haloacetonitriles were found to undergo biological hydrolysis, unlike regulated DBPs, and to yield haloacetamides and haloacetic acids. Overall, these systematic studies can be used to inform data-driven biofilter design and help practitioners understand and maximize the utility of biofiltration for DBP control in potable reuse.

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