Hydroxyl Radical/Ozone Ratios During Ozonation Processes. II. The Effect of Temperature, pH, Alkalinity, and DOM Properties

Elovitz, Michael S.; Gunten, Urs von; Kaiser, Hans‐Peter

doi:10.1080/01919510008547216

Cited by 308 publications

(196 citation statements)

References 21 publications

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“…According to Elovitz et al (2000), the concentration of hydroxyl radicals was independent of the water temperature. Using the equilibrium concentrations of dissolved ozone, C O 3s ; at 5, 15, and 25°C (Fig.…”

Section: Determination Of the Indirect (Radical) Reaction Rate Constantmentioning

confidence: 99%

Ozonation of Naphthenic Acids in Water: Kinetic Study

jibouri

Upreti

2015

Water Air Soil Pollut

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The large amount of oil sands processaffected water (OSPW), produced from the extraction of oil from oil sands in Alberta, Canada, has demonstrated both acute and chronic toxicity to many species due to the presence of naphthenic acids (NAs). The Bzero discharge^policy posted by the Alberta government presents a major challenge for the oil sands industries. In this study, ozonation was used to remove model NAs from water. It was found that the removal of NAs increased with the temperature. The kinetics of direct ozonation between molecular ozone and NAs was investigated in the presence of a radical scavenger, sodium bicarbonate. The rate constants of the direct ozonation at 5, 15 and 25°C were determined to be 0.67, 2.71 and 8.85 M −1 s −1 , respectively, and the activation energy of the direct ozonation was found to be 88.85 kJ mol −1 . The kinetics of indirect ozonation was also studied. By using pCBA as a hydroxyl radical probe compound to determine the hydroxyl radical concentration and applying the ratio of hydroxyl radical concentration to dissolved ozone concentration, R ct , the rate constants of the indirect ozonation of NAs were found to be 1.12×10 8 , 1.78×10 8 and 2.33×10 8 M −1 s −1 at 5, 15 and 25°C, respectively. In addition, from the Arrhenius plot of the rate constants, the activation energy of the indirect ozonation was found to be 25.41 kJ mole −1 .

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Section: Determination Of the Indirect (Radical) Reaction Rate Constantmentioning

confidence: 99%

Ozonation of Naphthenic Acids in Water: Kinetic Study

jibouri

Upreti

2015

Water Air Soil Pollut

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“…4, using the R ct concept originally proposed by Elovitz et al (4). R ct is defined in equation 6 as the ratio of ozone exposure to hydroxyl radical exposure:…”

Section: Determination Of C T Values For Hydroxyl Radicalsmentioning

confidence: 99%

Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions

Cho

Chung

Yoon

2003

Appl Environ Microbiol

170

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Ozone is widely used to disinfect drinking water and wastewater due to its strong biocidal oxidizing properties. Recently, it was reported that hydroxyl radicals ( ⅐ OH), resulting from ozone decomposition, play a significant role in microbial inactivation when Bacillus subtilis endospores were used as the test microorganisms in pH controlled distilled water. However, it is not yet known how natural organic matter (NOM), which is ubiquitous in sources of drinking water, affects this process of disinfection by ozone-initiated radical reactions. Two types of water matrix were considered for this study. One is water containing humic acid, which is commercially available. The other is water from the Han River. This study reported that hydroxyl radicals, initiated by the ozone chain reaction, were significantly effective at B. subtilis endospore inactivation in water containing NOM, as well as in pH-controlled distilled water. The type of NOM and the pH have a considerable effect on the percentage of disinfection by hydroxyl radicals, which ranged from 20 to 50%. In addition, the theoretical C T value of hydroxyl radicals for 2-log B. subtilis removal was estimated to be about 2.4 ؋ 10 4 times smaller than that of ozone, assuming that there is no synergistic activity between ozone and hydroxyl radicals.Ozone is widely used to disinfect drinking water and wastewater due to its strong biocidal oxidizing properties. Many studies on ozone disinfection have focused on the effects of ozone on various microorganisms and the factors affecting the inactivation of these microorganisms such as pH, temperature, contact time, ozone dose, and ozone demand (1,6,9,19). Among the factors, the role of pH in inactivating microorganisms is not well understood and is somewhat controversial (2,5,12,19,25). No pH requirement for inactivation of microroganisms or fast inactivation by low pH has been reported without much discussion of the exact duration of exposure to ozone or the coexistence of hydroxyl radicals. This is partly due to the limited approaches used which considered mainly the biocidal activity of molecular ozone (5, 11, 12) rather than the indirect effect of hydroxyl radicals resulting from ozone decomposition. On the other hand, several studies did emphasize the importance of hydroxyl radicals in microorganism inactivation (1, 3). Recently, Cho et al. (2) reported that under certain experimental conditions, the presence of hydroxyl radicals produced by ozone disinfection plays a significant role in the inactivation of Bacillus subtilis endospores in pH-controlled ozone-demand-free distilled water. In their study, the observed C T values for achieving a 2-log inactivation were 40% lower at pH 8.2 than at pH 5.6 when time-dependent ozone decay as a function of the reaction time was considered in relation to the pH difference. However, in the presence of excess hydroxyl radical scavengers (t-butanol), where it is difficult for hydroxyl radical to exist, all the observed C T values achieved parity, within a 10% margin of error, ...

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“…Rate constants derived from these plots show that O 3 decay rates increase more than one order of magnitude for a temperature range of 5-35 • C. For 5 • C and 15 • C, an initial, fast reaction phase precedes the principal first-order phase. For reactions at 25 • C and 35 • C, there is little or no distinct initial phase and the entire ozone depletion appears to be first-order in (O 3 ) [23]. From the agronomical point of view, the water temperature was higher than optimal values [15,16] for the forcing process in both systems; the higher sensitivity to thermal variations of the environment was measured for the closed loop system.…”

Section: Introductionmentioning

confidence: 81%

“…In fact, the reaction ability of ozone is significantly affected by the temperature. Usually, ozone depletion rates increase with increasing temperature [23]. First-order kinetic plots indicate that, in general, ozone depletion is first-order in O 3 concentration for at least three to four reaction half-lives.…”

Section: Introductionmentioning

confidence: 99%

Effects on Water Management and Quality Characteristics of Ozone Application in Chicory Forcing Process: A Pilot System

2017

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Abstract:Agriculture is the largest user of world water resources, accounting for 70% of all consumption. Reducing water consumption and increasing water use efficiency in agriculture are two of the main challenges that need to be faced in the coming decades. Radicchio Rosso di Treviso Tardivo (RTT) is a vegetable that requires a water forcing process prior to final commercialization which presents a significant environmental impact due to the high water volumes used and then dispersed into the environment. The experiment was aimed at reducing the water use in the forcing process of RTT, by developing a pilot system with recycled water in a closed loop through ozone treatment. Concerning water quality, the redox potential value was higher in the ozonized system, whereas turbidity, pH and electrical conductivity of the ozonized system did not change significantly from the control. Yield and quality of plants obtained in the ozonized system did not significantly differ from the control plants except for the antioxidant activity that was higher in plants forced using the water treated with ozone. Our initial results suggest that the ozone treatment could be applied in the forcing process and is suitable for growers, saving up to 95% of water volumes normally used for this cultivation practice.

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Hydroxyl Radical/Ozone Ratios During Ozonation Processes. II. The Effect of Temperature, pH, Alkalinity, and DOM Properties

Cited by 308 publications

References 21 publications

Ozonation of Naphthenic Acids in Water: Kinetic Study

Ozonation of Naphthenic Acids in Water: Kinetic Study

Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions

Effects on Water Management and Quality Characteristics of Ozone Application in Chicory Forcing Process: A Pilot System

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