Inactivation of Giardia muris Using Ozone and Ozone-Hydrogen Peroxide

The disinfection effects of the ozone molecule alone and that of ozone decomposition products when inactivating Giardia muris cysts were investigated at bench-scale using two different ozone demand-free laboratory buffer systems. The first water was a 0.05 M phosphate buffer with hydrogen peroxide added at a 10:1 weight ratio. The second water was a 0.05 M phosphate – 0.01 M bicarbonate buffer which quickly scavenged radical species from ozone decomposition. The C3H/HeN mouse model was used to assess the infectivity of ozone treated cysts.

The phosphate-bicarbonate buffer system had significantly greater (P ≤ 0.05) inactivation of G. muris cysts than that observed in the phosphate buffer – peroxide system where ozone was completely decomposed in less than 120 s. Consequently, the design of ozone disinfection processes should maintain ozone residual for disinfection prior to the addition of hydrogen peroxide for the oxidation of other compounds.     

Production and Removal of Assimilable Organic Carbon Under Pilot-Plant Conditions Through the Use of Ozone and PEROXONE

Pilot-plant studies were conducted in two source waters to determine the effects of predisinfection with ozone alone and with a combination of hydrogen peroxide and ozone (PEROXONE) on the production of assimilable organic carbon (AOC) compounds. Colorado River water (CRW) and State project water (SPW) from Northern California were treated with ozone alone at applied dosages ranging from 1 to 4 mg/L and with PEROXONE at hydrogen peroxide/ozone (H₂O₂/O₃) ratios of 0.05, 0.10, 0.20, and 0.30. Ozonation of CRW with applied dosages of 1.0,2.0, and 4.0 mg/L increased AOC concentrations from 70μg C/L to 275, 350, and 224 μg C/L, respectively. Ozonation of SPW with an applied dosage of 4.0 mg/L elevated AOC concentrations from 70 to 522μg C/L.     

Evaluation of High Level Ozone Inactivation of Giardia muris Using an Animal Infectivity Model

Ozone inactivation of Giardia muris cysts was investigated in laboratory phosphate buffer (pH 6.7; 22°C) at bench-scale using four ozone dose levels and two contact times. The C3H/HeN mouse model was used to assess the infectivity of ozone treated cysts. This model was found to be a sensitive measure of cyst inactivation to 99.99% inactivation and beyond. It was also observed that ozone rapidly inactivated G. muris and that ozone concentration appeared to be the most important parameter for predicting ozone inactivation of G. muris cysts.     

Performance evaluation of ozonation and an ozone/hydrogen peroxide process toward development of a new sewage treatment process—Focusing on organic compounds and emerging contaminants

Performance of ozonation and an ozone/hydrogen peroxide process under a new concept centering on ozonation and/or ozone/hydrogen peroxide processes in sewage treatment processes comprising only physical and chemical processes are discussed, with focus on the removal of matrix organic compounds and emerging contaminants. Matrix organic compounds of filtrated primary sewage effluents were removed to as low as 3.2 mgC/L in the ozone/hydrogen peroxide process at an ozone consumption of around 400 mg/L. Linear relationships between ozone consumption and removal amounts of organic compounds were observed, in which the amounts of ozone required to remove 1 mg of organic carbon were 9.5 and 8.3 mg (2.4 and 2.1 mol-O₃/mol-C) in ozonation and the ozone/hydrogen peroxide process, respectively. Ratios of hydroxyl radical exposure to ozone exposure were in the order of 10^–9 to 10^–8 for ozonation and 10^–7 to 10^–6 for the ozone/hydrogen peroxide process. Experiments and a kinetic evaluation showed that ozonation and/or the ozone/hydrogen peroxide process have high elimination capability for emerging contaminants, even in primary sewage effluent with the thorough removal of matrix organic compounds. Newly found reaction phenomena, the temporal increase and decrease of dissolved ozone and accumulation of hydrogen peroxide in the early stage of oxidation with the continuous feeding of hydrogen peroxide, were presented. Possible reaction mechanisms are also discussed.     

Kinetic Study and Optimum Control of the Ozone/UV Process Measuring Hydrogen Peroxide Formed In-situ

This study was conducted to develop a kinetic model of the ozone/UV process by monitoring the trend of in-situ hydrogen peroxide formation. A specifically devised setup, which could continuously measure the concentration of hydrogen peroxide as low as 10 μg/L, was used. The kinetic equations, comprised of several intrinsic constants with semi-empirical parameters (k_chain and k_R3) were developed to predict the time varied residual ozone and hydrogen peroxide formed in situ along with the hydroxyl radical concentration at steady state,[OH°]_ss, in the ozone/UV process. The optimum ozone dose was also investigated at a fixed UV dose using the removal rate of UV absorbance at 254 nm (A₂₅₄) in raw drinking water. The result showed that the continuous monitoring of hydrogen peroxide formed in situ in an ozone/UV process could be used as an important tool to optimize the operation of the process.     

Effects Of Ozone-Hydrogen Peroxide Combination On The Formation Of Biodegradable Dissolved Organic Carbon

The effects of ozone and ozone/hydrogen peroxide on BDOC formation were studied with the “Ozotest” method, a laboratory technique that permits the assessment of oxidation efficiency. Oxidation treatments were performed on river water and sand filter effluent samples. Ozone consumption, reduction of UV absorbance, and BDOC formation were monitored during the experiments. The ratio of 0.35-0.45 mg H₂O₂ per mg O₃ used to degrade pesticides also was optimal for the oxidation of organic matter. BDOC formation versus ozone dose curves with ozone alone or ozone/peroxide system were similar. BDOC formation was optimum at an applied ozone dose of 0.5-1 mg O₃/mg C (contact time = 10 min). The ozone/peroxide system yielded lower BDOC values than ozone alone, a phenomenon related to differences in byproducts generated by the two oxidative systems. Moreover, reduction of the concentration of DOC was higher with ozone/hydrogen peroxide than with ozone alone. For both oxidant systems, BDOC formation occurred during the first minute of treatment.     

Impact of Ozone Treatment on Selected Microbiological Parameters

A pilot plant study was conducted to evaluate the effects of ozonation on the quality of Colorado River water delivered to the Phoenix (Arizona) Union Hills Water Treatment Plant through the Central Arizona Project canal. Raw and finished water were monitored for basic chemical water quality parameters and for microorganisms including total coliforms, heterotrophic plate count, enteric viruses, Giardia and Crvptosporidium cysts. Ozone, applied through diffusion contactors in dosages optimized to provide the required CT (concentration x contact time) value, was used as a primary disinfectant in two of the four 10 gpm (37.8 L/min) treatment trains.     

Compromise Between Bromate Ion Formation and Pesticides Degradation and/or Manganese Removal

Ozonation is a widely used technology within the water industry. Bromate ion formed by oxidation of water containing bromide ion was studied with the Gas Ozone Test and Pilot Scale Ozonation. Bromate ion formation was investigated along with the removal of triazines and/or manganese. Under identical conditions of ozonation, BrO₃ ^? formation is specific for each water and depends on parameters such as Total Organic Carbon, UV absorbance at 254 nm, applied ozone and ozone residual. Pesticides degradation by ozonation alone cannot be achieved without the formation of BrO₃ ^? at a high concentration. Hydrogen peroxide, at a constant ozone dose, reduces the BrO₃ ^? formation. However, even with the use of hydrogen peroxide, the concentration of BrO₃ ^? can remain in excess of the provisional Maximum Contaminant Level (10 μg/L). For certain types of water, pesticide degradation is difficult to achieve if the MCL for BrO₃ ^? has to be met. Manganese oxidation by ozone appears to be achieved without high bromate formation; indeed the presence of manganese hinders BrO₃ ^? formation.     

The Impact of Traces of Hydrogen Peroxide and Phosphate on the Ozone Decomposition Rate in “Pure Water”

To obtain an idea of the magnitudes of the ozone loss rates r_O3 in practical applications of ozone, an overall determination of the ozone decay profiles and rate constants was carried out in four different systems. These systems resemble different conditions for industrial application of ozone and the peroxone process, such as in the field of micro electronics, drinking water purification, disinfection, etc. Therefore, the behavior of ozone was monitored in the pH range from 4.5 to 9.0, in pure water and phosphate buffered systems in absence and presence of small amounts of hydrogen peroxide (10^?7 M to 10^?5 M H₂O₂). First the reproducibility of the ozone decay profiles was checked and from the various kinetic formalism tests, the reaction order 1.5 for the ozone decay rate has been selected. As expected, hydrogen peroxide increases the decay rates. In pure systems, added concentrations of 10^?7M H₂O₂ already cause a remarkable acceleration of the ozone decay in the acidic and neutral pH range compared to the pure systems. However for alkaline pH conditions almost no effect of the low hydrogen peroxide concentrations was noticed. Contradictory to literature data, in the absence of hydrogen peroxide, ozone displays faster decays in the buffered systems of low ionic strength of 0.02 compared to pure water. This acceleration is more pronounced for acidic pH conditions. Low concentrations of phosphate may indeed accelerate the ozone decay in the presence of organic matter. Adding H₂O₂ concentrations below 10^?5M to phosphate buffered solutions has a negligible effect on the ozone decay rate compared with pure water systems, except for pH 7. It appears that phosphate masks the effect of hydrogen peroxide below 10^?5 M as tested here. Thus the application of AOP's by adding low concentrations of hydrogen peroxide is not well feasible in the presence of phosphate buffers in pure water systems.     

Parameters Affecting the Formation of Bromate Ion During Ozonation

Batch type ozone experiments conducted on aquatic humic substances solutions spiked with bromide ion were developed to evaluate the importance of various parameters that may affect the formation of bromate ion during ozonation. The nature of the NOM, the alkalinity, the bromide ion content and the presence of ammonia were found to significantly affect the bromate ion production. Temperature and pH can be considered as minor factors. The ozonation of a clarified surface water using a continuous flow ozone contactor have shown that the addition of a low quantity of ammonia (0.05 to 0.1 mg/L NNH₄ ⁺) appeared to be an interesting option for controlling the bromate formation. On the contrary, the addition of hydrogen peroxide may enhance or reduce the bromate ion production, depending on the applied hydrogen peroxide/ozone ratio.     

Effect of Ozone Treatment on the Reduction of Chlorpyrifos Residues in Fresh Lychee Fruits

The effect of ozone on the reduction of chlorpyrifos residue in lychee cv. Chakapat (Litchi chinensis Sonn.) was studied. Lychee fruits were dipped in the solution of chlorpyrifos at a concentration of 10 mg L^?1 for 10 min. Then, they were exposed to ozone gas (O₃) at concentrations of 80, 160, 200, 240 mg L^?1 and dipped in ozone-containing water, at concentrations of 2.2, 2.4, 3.4 and 3.2 mg. L^?1 for 10, 20, 30 and 60 min, respectively. Both ozone gas and ozone-containing water reduced pesticide residue in lychee, but exposure to ozone gas for 60 min was most effective. When lychee fruits were stored at 25 °C for 6 days, both processes did not show significant differences in weight loss, total soluble solids (TSS) and titratable acidity (TA). However, ozone-containing water decreased the eating quality of lychees after storage, compared with the ozone-fumigated groups.     

Kinetic Study of Ozone Decay in Homogeneous Phosphate-Buffered Medium

The ozone decomposition reaction is analyzed in a homogeneous reactor through in-situ measurement of the ozone depletion. The experiments were carried out at pHs between 1 to 11 in H₂PO₄^?/HPO₄^2– buffers at constant ionic strength (0.1 M) and between 5 and 35 °C. A kinetic model for ozone decomposition is proposed considering the existence of two chemical subsystems, one accounting for direct ozone decomposition leading to hydrogen peroxide and the second one accounting for the reaction between the hydrogen peroxide with the ozone to give different radical species. The model explains the apparent reaction order respect of the ozone for the entire pH interval. The decomposition kinetics at pH 4.5, 6.1, and 9.0 is analyzed at different ionic strength and the results suggest that the phosphate ions do not act as a hydroxyl radical scavenger in the ozone decomposition mechanism.     

Comparative Analysis of Ozone and Ultrasound Effect on the Elimination of Giardia spp. Cysts from Wastewater

Giardia spp. is a flagellate protozoan that presents two evolution forms, cysts and trophozoites. Cysts are resistant to chlorine, the most employed disinfectant agent in the treatment of water. For this reason, new techniques for the disinfection of waters that contain this parasite are necessary. This work evaluated the efficiency of the disinfection by ozone and ultrasound individually and simultaneously upon wastewater. The data obtained showed that after application, ozone, ultrasound, and combined techniques induced a significant elimination of Giardia spp. cysts. Furthermore, this effect was more accentuated when the two techniques were applied simultaneously.     

Ultraviolet-Enhanced Ozonation of Organic Compounds: 1,2-Dichloroethane and Trichloroethylene as Model Substrates

1,2–Dichloroethane (DCE) and trichloroethylene (TCE) were used as model compounds to study the oxidation of organic chemicals by ozone/ultraviolet radiation, ozone, and hydrogen peroxide/ultraviolet radiation. It was found that ozone/ultraviolet radiation oxidized both 1,2–dichloroethane and trichloroethylene in batch systems, at pH = 2 (phosphate buffer). At ozone concentrations in the 1 to 5 mg/L range, the reaction was first order in both ozone and substrate. At pH = 2 and initial ozone concentration 2.2–2.6 mg/L, rate constants (k)Q = 25 and 130 M^-1sec^-1 were observed for the ozone/ultraviolet radiation oxidation of DCE and TCE, respectively. The rat e constants for ozone oxidation of DCE and TCE without ultraviolet radiation were 4.3 and 47 M^-1sec^-1, respectively.

The higher rate of TCE oxidation implies that direct reaction occurs with the double bond. Finite reaction rate of DCE with ozone, and substantial increases in rate at higher pH imply the participatation of hydroxyl radicals in the oxidation of both compounds. For example, at pH = 7, initial ozone concentration of 2.3 mg/L, the k_o for TCE oxidation by ozone/ultraviolet radiation is approximately 500 M^?1 sec^?1 almost too fast to measure in a batch system.The rate also is increased by increased ultraviolet radiation intensity, and by the presence of hydrogen peroxide, which acts as a catalyst.     

The Combination of Ozone/Hydrogen Peroxide and Ozone/UV Radiation for Reduction of Trihalomethane Formation Potential in Surface Water

Applied ozone dosages of 20, 25, and 30 mg/L to lake water utilized by the city of Shreveport, LA produced no significant reductions in trihalomethane formation potentials (THMFP). However, the addition of 20 mg/L of hydrogen peroxide and/or 0.67 W/L of UV radiation (254 nm) in combination with ozone produced decreases in THMFP of over 60% in 60 minutes. Smaller THMFP decreases were seen with shorter contact times. The use of H₂O₂ and/or UV in combination with O₃ increased the percentage of applied ozone consumed by the lake water (i.e., enhanced the ozone mass transfer) five times over simple ozonation.     

Removal Characteristics of Organic Pollutants in Sewage Treatment by a Pre-Coagulation,Ozonation and Ozone/Hydrogen Peroxide Process

The applicability of a sequential process of ozonation and ozone/hydrogen peroxide process for the removal of soluble organic compounds from a pre-coagulated municipal sewage was examined. 6–25% of initial T-COD_Cr was removed at the early stage of ozonation before the ratio of consumed ozone to removed T-COD_Cr dramatically increased. Until dissolved ozone was detected, 0.3 mgO₃/mgTOC₀ (Initial TOC) of ozone was consumed. When an ozone/hydrogen peroxide process was applied, additional COD_Cr was removed. And we elucidated that two following findings are important for the better performance of ozone/hydrogen peroxide process; those are to remove readily reactive organic compounds with ozone before the application of ozone/hydrogen peroxide process and to avoid the excess addition of hydrogen peroxide. Based on these two findings, we proposed a sequential process of ozonation and multi-stage ozone/hydrogen peroxide process and the appropriate addition of hydrogen peroxide. T-COD_Cr, TOC and ATU-BOD₅ were reduced to less than 7 mg/L, 6 mgC/L and 5 mg/L, respectively after total treatment time of 79 min. Furthermore, we discussed the transformation of organic compounds and the removal of organic compounds. The removal amount of COD_Cr and UV₂₅₄ had good linear relationship until the removal amounts of COD_Cr and UV₂₅₄ were 30 mg/L and 0.11 cm^?1, respectively. Therefore UV₂₅₄ would be useful for an indicator for COD_Cr removal at the beginning of the treatment. The accumulation of carboxylic acids (formic acid, acetic acid and oxalic acid) was observed. The ratio of carbon concentration of carboxylic acids to TOC remaining was getting higher and reached around 0.5 finally. Removal of TOC was observed with the accumulation of carboxylic acids. When unknown organic compounds (organic compounds except for carboxylic acids) were oxidized, 70% was apparently removed as carbon dioxide and 30% was accumulated as carboxylic acids. A portion of biodegradable organic compounds to whole organic compounds was enhanced as shown by the increase ratio of BOD/COD_Cr.     

Ozone Versus Ozone/Peroxide Induced Particle Destabilization And Aggregation: A Pilot Study

This research compares the role of ozone and the conjunctive use of ozone plus hydrogen peroxide in particle destabilization and particle aggregation, and improvement in filtered water quality. Particle destabilization was observed at all doses of ozone and ozone/peroxide studied, whereas aggregation was observed with ozone only at lower doses (> 2 mg/L) and in conjunction with ozone/peroxide (all doses studied). As compared to alum alone, the ozone-plus-alum and ozone/peroxide-plus-alum treatments provided improved flocculation and better filtered water quality. In addition, each of these preoxidations significantly reduced alum requirements. Overall, in terms of particle destabilization and aggregation; i.e., effectiveness as a coagulation aid, Ozone/peroxide performed better than ozone.     

Chemical degradation of aldicarb in water using ozone

The use of ozone to degrade aldicarb in water was investigated under different conditions. The oxidation develops through the direct attack of ozone since the presence of hydroxyl radical inhibitors, such as tert-butanol, does not affect the degradation rate of aldicarb. The combination of ozone with hydrogen peroxide does not improve the oxidation rate which also confirms the absence of radical reactions to eliminate aldicarb. However, TOC removal increases 51% in the presence of hydrogen peroxide after 65 min of oxidation. The oxidation rate is strongly affected by the type of device for feeding ozone, which indicates that a fast gas-liquid reaction is taking place. Therefore, mass transfer and chemical reaction steps are important factors in the establishment of the global rate of oxidation. Application of kinetic equations derived from gas absorption theories allows the determination of the rate constant of the direct ozone–aldicarb reaction, which was found to be: k = 3·18 × 10¹¹ exp(–6000/T) m³ mol^?1s^?1.     

Ozone Disinfection Efficiency for Indicator Microorganisms at Different pH Values and Temperatures

Disinfection efficiency of ozone was determined in various types of water at different pH (6, 7 and 8) values and temperatures (15, 25 and 35 ^°C) for E. coli and Salmonella. Three different applied ozone concentrations (1.5, 1.7, and 2 mg/L) in the gas phase were applied, and samples were taken at different time intervals to determine microbial survival using spread plate count (SPC) and ozone residual. Highest microbial inactivation was observed in distilled water with applied ozone concentration of 2 mg/L in the gas phase. Survival of E. coli was higher at pH 8 and 15 ^°C as compared to lower pH values and temperatures as depicted by the inactivation kinetics of the test microbes used in the study. Salmonella showed 5 and 6 log removal after contact time of 45 and 60 sec, respectively, at 2 mg/L. Disinfection of mixed culture showed relatively more survival of E. coli; as 3 and 4 log removal of E. coli and 4 and 5 log removal of Salmonella was observed after 45 and 60 sec.     

Organic matter removal in boiler feed water treatment of a power plant with ozone

The purpose of this work was to test the effectiveness of ozone as a treatment to remove organic matter of the boiler feed water of a power plant. In the experiments carried out in the power plant Endesa in As Pontes (Spain), chlorine was substituted for ozone in the pre‐treatment stage. The use of ozone reduced the organic content of the boiler feed water by an average 20% compared with chlorination and by 50% when ozone was combined with hydrogen peroxide. The latter treatment achieved an organic content in the boiler feed water of less than 40 μg C/L. The ozone treatment also reduced the content of trihalomethanes in the drinking water, produced by the same plant, to values in the range of 10 μg/L and even to undetectable values when ozone was combined with hydrogen peroxide, in spite of the postchlorination applied to this stream to ensure a disinfectant capacity though the distribution system.