UV/chlorine vs. UV/H 2 O 2 for water reuse at Orange County Water District, CA: a pilot study
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/H 2 O...
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Veröffentlicht in: | Environmental science water research & technology 2020-08, Vol.6 (9), p.2416-2431 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | 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/H
2
O
2
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
H
2
O
2
or ∼1.0 mg L
−1
free Cl
2
(HOCl) in the RO permeate at ambient quality parameters,
e.g.
2.2–2.4 mg L
−1
monochloramine (as Cl
2
), 1.2–1.4 mg L
−1
dichloramine (as Cl
2
), ≤0.08 mg L
−1
NO
2
−
(UV/H
2
O
2
AOP), ∼97.0%
T
, resulted in 0.56 and ≥0.51 log reduction of 1,4-dioxane with the UV/chloramine/H
2
O
2
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/H
2
O
2
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/H
2
O
2
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. |
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ISSN: | 2053-1400 2053-1419 |
DOI: | 10.1039/D0EW00316F |