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The efficiency of three different oxidation processes, UV/H2O2 oxidation, ferrate(VI) oxidation, and ozonation with and without hydroxyl radical (OH) scavenger tert-butyl alcohol (TBA) on the removal of organic compounds from oil sands process-affected water (OSPW) was investigated and compared. The removal of aromatics and naphthenic acids (NAs) was explored by synchronous fluorescence spectra (SFS), ion mobility spectra (IMS), proton and carbon nuclear magnetic resonance ((1)H and (13)C NMR), and ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC TOF-MS). UV/H2O2 oxidation occurred through radical reaction and photolysis, transforming one-ring, two-ring, and three-ring fluorescing aromatics simultaneously and achieving 42.4% of classical NAs removal at 2.0 mM H2O2 and 950 mJ/cm(2) UV dose provided with medium pressure mercury lamp. Ferrate(VI) oxidation exhibited high selectivity, preferentially removing two-ring and three-ring fluorescing aromatics, sulfur-containing NAs (NAs + S), and NAs with high carbon and high hydrogen deficiency. At 2.0 mM Fe(VI), 46.7% of classical NAs was removed. Ozonation achieved almost complete removal of fluorescing aromatics, NAs + S, and classical NAs (NAs with two oxygen atoms) at the dose of 2.0 mM O3. Both molecular ozone reaction and OH reaction were important pathways in transforming the organics in OSPW as supported by ozonation performance with and without TBA. (1)H NMR analyses further confirmed the removal of aromatics and NAs both qualitatively and quantitatively. All the three oxidation processes reduced the acute toxicity towards Vibrio fischeri and on goldfish primary kidney macrophages (PKMs), with ozonation being the most efficient., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

When treating drinking water using UV/H2O2 advanced oxidation, the H2O2 residual is usually quenched to allow for downstream chlorine stability. In some utilities, monochloramine (NH2Cl) is used for secondary disinfection, and H2O2 may not need to be quenched because NH2Cl and H2O2 can coexist for some time. However, when ammonia and chlorine are applied to form NH2Cl in the H2O2 -containing water, H2O2 will compete with ammonia to react with the applied chlorine, compromising the NH2Cl formation efficiency. This research combined theory and experiments to evaluate NH2Cl formation efficiency in the presence of H2O2 in Lake Ontario water and, after NH2Cl formation, its subsequent decay at different temperatures and pH. The results demonstrated that at many typical temperatures and pH, the presence of H2O2 does not significantly impair the formation of NH2Cl. Furthermore, while H2O2 accelerates NH2Cl decay, the results suggest that under specific conditions, such as short to medium residence times (e.g., less than 48 h), it may be possible for NH2Cl to coexist with as much as 5 mg/L H2O2 without compromising secondary disinfection. [ABSTRACT FROM AUTHOR]

• Peracetic acid (PAA) may exert chlorine demand in drinking water. • PAA's chlorine demand is mostly by H 2 O 2 from PAA hydrolysis, especially at pH ≥ 8. • Direct PAA reaction with chlorine is slow and the reaction rate is pH dependent. • In most cases, chlorine demand by PAA is < 20% of initial chlorine over 7 days. Peracetic acid (PAA) may be used in drinking water treatment for pre-oxidation and mussel control at the intake. PAA may exert a downstream chlorine demand, but full details of this reaction have not been reported. There are three possible mechanisms of this demand: (1) PAA may react directly with chlorine; (2) PAA exists in equilibrium with hydrogen peroxide, which is known to react with chlorine; and (3) as H 2 O 2 reacts with chlorine, PAA will hydrolyze to form more H 2 O 2 to re-establish PAA/H 2 O 2 equilibrium, thereby serving as an indirect reservoir of chlorine demand. While the H 2 O 2 reaction with chlorine is well known, the other mechanisms of possible PAA-induced chlorine demand have not previously been investigated. The observed molar stoichiometric ratio of PAA to free chlorine (n) for the presumed direct PAA + free chlorine reaction was determined to be approximately 2, and the corresponding observed reaction rate coefficients at pH 6, 7, 8, and 9 were 2.76, 3.14, 1.61, 10.1 M−n·s−1, respectively (at 25 °C). With these estimated values, a kinetic model was built to predict the chlorine demand by PAA. The results suggest that chlorine demand from PAA is likely to be negligible over the course of several days (e.g., < 20% chlorine loss) for most conditions except for high pH (e.g., >8) and high PAA:Cl 2 molar ratios (e.g., >2:1). [ABSTRACT FROM AUTHOR]