Emerging application of advanced oxidation processes for the potable reuse of municipal wastewater

Municipal wastewater is being increasingly emphasized as a local, reliable source water supply for potable water. Potable reuse facilities frequently employ Full Advanced Treatment (FAT) trains, most often including microfiltration (MF), reverse osmosis (RO) and the UV/hydrogen peroxide (UV/H2O2) advanced oxidation process (AOP). However, the widespread implementation of FAT treatment is hindered by two major challenges: high cost and the disposal of RO concentrate (ROC). In this dissertation, we evaluated the potential of emerging AOPs, including ozonation followed by biological activated carbon (O3/BAC), the UV/chloramines AOP, and the UV/free chlorine AOP to deal with these two major challenges for FAT trains. We evaluated the application of O3/BAC to remove nitrate and organic contaminants from ROC to facilitate disposal to marine waters. We characterized the ability of the UV/chloramines and the UV/free chlorine AOPs to serve as more efficient alternatives to the UV/H2O2 AOP for the treatment of RO permeate. Chapter 1 introduces the FAT treatment process train, two of the major challenges facing these FAT trains, emerging AOPs to address these challenges, existing knowledge gaps and the objectives of this dissertation. Chapter 2 evaluates the feasibility of O3/BAC to treat RO concentrate at pilot-scale. The results suggest the potential for substantial synergy between potable reuse, and the removal of nitrogen and organic contaminants, enabling utilities to meet regulatory limits while partially offsetting the costs of producing a potable water supply. Chapter 3 develops a kinetic model for the UV/chloramines AOP when applied to RO permeate. The model is able to simultaneously predict the loss of chloramines and contaminants, such as 1,4-dioxane by determining quantum yields for chloramines and incorporating the subsequent reactions of NH2 radical. Initial cost estimates based on bench-scale results indicate UV/chloramines AOP using the residual chloramines in RO permeate could be a cost-effective alternative to the current UV/H2O2-chloramines AOP in some cases depending on the background chloramines concentrations and other constituents in RO permeate. Chapter 4 evaluates UV/free chlorine and UV/chloramines AOPs as alternatives to the UV/H2O2 AOP for treatment of RO permeate at pilot-scale. First, we characterized the speciation of the oxidants during AOP treatment and validated the ability of our kinetic models to accurately predict oxidant speciation. Second, we evaluated the ability of the different AOPs to degrade important target contaminants, such as 1,4-dioxane. Initial cost estimates indicate the UV/free chlorine AOP treatment to achieve 0.5-log 1,4-dioxane removal would be nearly half the cost for UV/H2O2 AOP. The cost for UV/chloramines AOP treatment could be comparable to UV/H2O2 AOP. Third, we demonstrated that after AOP treatment and chloramination for distribution systems, total halogenated DBP formation was comparable between these three AOPs. Chapter 5 summarizes the findings and contributions of this dissertation and proposes the issues that need to be addressed in future research to better understand the feasibility of these emerging AOPs in practice and to enable scale-up.

Advisor: Mitch William A. 
Criddle Craig 
Luthy Richard G.