On-site demonstration tests evaluated 1,4-dioxane removal in reverse osmosis permeate (RO permeate) at the Orange County Water District (OCWD) Advanced Water Purification Facility (AWPF). The study used a pilot-scale ultraviolet (UV) reactor to compare efficacy of UV/chloramine, UV/chloramine/H2O2 and UV/chloramine/HOCl advanced oxidation processes (AOPs). The UV/chloramine process did not achieve the targeted 0.5 log removal of 1,4-dioxane even at a high UV fluence of 4400 mJ cm−2 and the 1,4-dioxane decay did not follow pseudo-first order kinetics. Oxidant concentrations as low as 2.6 mg L−1 H2O2 or ∼1.0 mg L−1 free Cl2 (HOCl) in the RO permeate at ambient quality parameters, e.g. 2.2–2.4 mg L−1 monochloramine (as Cl2), 1.2–1.4 mg L−1 dichloramine (as Cl2), ≤0.08 mg L−1 NO2− (UV/H2O2 AOP), ∼97.0% T, resulted in 0.56 and ≥0.51 log reduction of 1,4-dioxane with the UV/chloramine/H2O2 and UV/chloramine/HOCl process, respectively, while simultaneously achieving ∼2.0 log reduction of NDMA. Overall, the UV/chloramine/HOCl process showed higher removal efficiency of 1,4-dioxane than UV/chloramine/H2O2 for the same mass-based oxidant concentrations and process conditions. Nitrite ions present in the RO permeate and/or generated from monochloramine photolysis during the UV/AOP impacted significantly the process performance. It was confirmed through these pilot-scale tests that the removal of 1,4-dioxane in the UV/chloramine/H2O2 and UV/chloramine/HOCl processes can be predicted accurately with a comprehensive mechanistic kinetic model that accounts for the molecular and radical reactions that occur in the RO permeate in the UV reactor.
No takes yet. Share an insight, caveat, or question.
Kwon et al. (2020) studied this question.
Synapse has enriched 5 related papers. Consider them for comparative context: