Influence of Carbonate on the Ozone/Hydrogen Peroxide Based Advanced Oxidation Process for Drinking Water Treatment

The influence of carbonate on the ozone/hydrogen peroxide process has been investigated. Carbonate radicals, which are formed from the reaction of bicarbonate/carbonate with OH radicals, act as a chain carrier for ozone decomposition due to their reaction with hydrogen peroxide. The efficiency of bicarbonate/carbonate as a promoter for the radical-based chain reaction in presence of hydrogen peroxide has been calibrated and compared to a well-known chain promoter (methanol) and an inhibitor (tert-butanol). Relative to tert-butanol, the hydrogen peroxide induced ozone decomposition is accelerated by bicarbonate/carbonate. Relative to methanol, bicarbonate/carbonate in presence of hydrogen peroxide is less effective as a promoter under comparable experimental conditions.     

Application of Combined Ozone–Hydrogen Peroxide for the Removal of Aromatic Compounds from a Groundwater

Nitro and chlorobenzene compounds, which are widely used in dye industries, have been associated recently with groundwater contamination. Because of their potential toxicity and for taste and odor considerations, three main actions were undertaken to solve the problem. First, to follow the advance of pollution toward the wells, samples were collected automatically and analyzed using GC-MS. Results indicate that o-chloronitrobenzene was the main pollutant in concentrations ranging from 10 to 2000μg/L. Second, to monitor the drinking water quality, an on-line spectrophotometer was used to measure the optical density at 254 nm at the inlet and outlet of the plant. Third, the feasibility of using the O₃/H₂O₉ combination was determined at a 450 L/h pilot plant. Reduction of concentrations of chloronitrobenzenes from 1900 μ/L to less than 20 μg/L could be reached by the application of 8 mg O3/L and 3 mg H2O9/L with a 20-minute contact time. To avoid an eventual bacterial egrowfn in the network due to biodegradability of the oxidation by-products, sand and GAC filtration were tested after oxidation. An evaluation of the costs of these different treatments is also presented.     

Bromate Formation in Ozone and Advanced Oxidation Processes

Both the direct ozone reaction and the indirect hydroxyl radical reaction are important in ozonation of drinking water. This article investigates the effectiveness of ozone versus the advanced oxidation process of ozone coupled with hydrogen peroxide in the formation of bromate. The investigation was conducted on a pilot scale at various H₂O₂:O₃ dose ratios of 0.1, 0.2, and 0.35 at different times of the year. The results of this study show a reduction in bromate with the addition of hydrogen peroxide to an ozone system versus ozone alone. It was also observed that bromate increased with increased H₂O₂:O₃ ratios; however, concentrations were still lower than those in the ozone only system.     

Theoretical Aspects Of The Kinetics Of Competitive First Reactions Of Ozone In The O3/H2O2 And O3/UV Oxidation Processes

Kinetics of competition between the ozone direct reaction with compounds in water, ozone-hydroperoxide ion reaction leading to free radicals in the O₃/H₂O₂ process, and the photolysis of ozone in the O₃/UV process are discussed in terms of diffusion and reaction times to establish conditions for these reactions to be competitive. Film theory and chemical kinetic concepts then are applied to estimate initial rates of ozone absorption and consumption, removal rates of compounds present in water, and the importance of the radical oxidation path versus direct ozone and/or photolysis reactions.     

Combination of Ozone with Activated Carbon as an Alternative to Conventional Advanced Oxidation Processes

The objective of this study was to compare the efficiency of O₃/granular activated carbon (GAC) to enhance ozone transformation into ·OH radicals, with the common advanced oxidation processes (O₃/OH^?, O₃/H₂O₂). The results obtained with model systems under the given experimental conditions showed that the system O₃/OH^? (pH 9) and O₃/H₂O₂ (pH 7, [H₂O₂] = 1·10^?5 M) are more efficient than O₃/GAC (pH 7, [GAC] = 0.5 g/L) to enhance ozone transformation into ·OH radicals. However, in Lake Zurich water the O₃/GAC process has a similar efficiency as O₃/H₂O₂ for ozone transformation into ·OH radicals. The results also show that the presence of GAC during Lake Zurich water ozonation leads to (i) removal of hydrophilic and hydrophobic micropollutants, (ii) reduction of the concentration of CO₃ ^2?/HCO₃ ^?, and (iii) decrease of the concentration of dissolved organic carbon (DOC) present in the system.     

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.     

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.     

Effect of Application of Ozone and Ozone Combined with Hydrogen Peroxide and Titanium Dioxide in the Removal of Pesticides From Water

The aim of this research work is to study the influence of hydrogen peroxide and titanium dioxide in the ozone-based treatment to degrade 44 organic pesticides present in natural water, which are systematically detected in the Ebro River Basin (Spain). The studied pesticides are: alachlor, aldrin, ametryn, atrazine, chlorfenvinfos, chlorpyrifos, pp'-DDD, op'-DDE, op'-DDT. pp'-DDT, desethylatrazine, 3,4-dichloroaniline, 4,4'-dichlorobenzophenone, dicofol, dieldrin, dimethoate, diuron, α-endosulphan, endosulphan-sulphate, endrin, α-HCH, β-HCH, γ-HCH, δ-HCH, heptachlor, heptachlor epoxide A, heptachlor epoxide B, hexachlorobenzene, isodrin, 4-isopropylaniline, isoproturon, metholachlor, methoxychlor, molinate, parathion methyl, parathion ethyl, prometon, prometryn, propazine, simazine, terbuthylazine, terbutryn, tetradifon and trifluralin. The ozonation using 3 mg O₃ L^?1 produces a pesticides removal close to 23%, whereas the application of O₃/H₂O₂ and O₃/TiO₂ treatments achieves average degradation yields lower than the ozonation. However, the application of O₃/H₂O₂ /TiO₂ process improves considerably the pesticides degradation and an average degradation yield of 36% is obtained.     

Treatment of Wastewater Coming from Painting Processes: Application of Conventional and Advanced Oxidation Technologies

The process of car body painting is one of the manufacturing processes that may involve the use of organic solvents for surface treatments. As a result of this process, wastewaters containing raw materials and auxiliary products used during the cleaning step are produced. The main objective of this study is to find an appropriate purification technique to eliminate or reduce the contamination present in this kind of wastewater. Different treatments were investigated: ozonation, ozonation combined with hydrogen peroxide, photo-Fenton treatment, and coagulation- flocculation.     

Oxidation of Propylene Glycol Methyl Ether Acetate Using Ozone-Based Advanced Oxidation Processes

The present study investigates the degradation of PGMEA and its TOC removal using O₃, UV/O₃, O₃/H₂O₂, and UV/H₂O₂ processes under various experimental conditions. Ozonation of PGMEA was substantially enhanced in the presence of UV light and H₂O₂. Approximately 33% of TOC enhancement was noted in UV/O₃ process over ozonation process. A linear relationship between PGMEA and H₂O₂ decomposition was observed in O₃/H₂O₂ and UV/H₂O₂ processes. The influence of solution pH on the decomposition of PGMEA was investigated and found that basic medium was the most efficient in all AOPs. After 60 minutes 62.4%, 100%, 90% and 54% of PGMEA decomposition at pH 10.0 was observed in O₃, UV/O₃, O₃/H₂O₂, and UV/H₂O₂ processes, respectively. It is concluded that UV/O₃ process is a promising approach for the oxidation and removal of PGMEA.     

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.     

Advanced Oxidation of Textile Wastewaters

Model dyeing and laundering wastewaters produced during two basic technological operations of the textile industry were subjected to treatment by advanced oxidation processes (AOPs). The following agents were used: ozone (O₃), hydrogen peroxide (H₂O₂) and UV radiation. They were applied separately and in all possible combinations: O₃ + UV, O₃ + H₂O₂, UV + H₂O₂, as well as all three at the same time: O₃ + UV + H₂O₂. Effluents before and after the treatment were analyzed according to requirements of the Polish Standards that included pH, color threshold, COD and concentration of anionic and non-ionic surfactants. Ozonation was carried out in a lab-scale bubble column reactor with a centrally located UV burner. The most effective version of AOPs proved to be the simultaneous use of all three agents. In the case of such treatment of dyeing wastewaters nearly complete discoloration and full decomposition of surface-active substances were obtained at 80% reduction of COD. A similar tendency was observed in the case of laundering wastewater, though in that case the results were slightly worse, which may be explained by much higher initial concentrations of the pollutants. Good treatment effects have also been obtained in combined treatment by simultaneous use of hydrogen peroxide and ozone.     

Ozonation and Advanced Oxidation Treatment of Emerging Organic Pollutants in Water and Wastewater

A vast number of persistent organic pollutants have been found in wastewater effluent, surface water, and drinking water around the world. This indicates their ineffective removal from water and wastewater using conventional treatment technologies. In addition to classical persistent organics such as organochlorine insecticides, solvents, and polychlorinated biphenyls, a growing number of emerging pollutants of both synthetic and natural origins have been identified as major environmental pollutants in recent years. A variety of advanced and conventional treatment options have been suggested for the removal and/or destruction of these persistent organics in water and wastewater, such as chemical oxidation, activated carbon adsorption, and membrane filtration. Of these options, chemical oxidation using ozone, alone or in combination with additional physical/chemical agents (i.e., advanced oxidation), has been proved a highly effective treatment process for a wide spectrum of emerging aqueous organic pollutants, including pesticides, pharmaceuticals, personal care products, surfactants, microbial toxins, and natural fatty acids. In this paper, we discuss the emerging organic pollutants of concern in the aquatic environment and focus on the issues associated with their removal using ozonation and advanced oxidation processes.     

Impact of Ozone and Hydrogen Peroxide vs. UV and Hydrogen Peroxide on Chlorine Residual

The current study undertaken by the Walkerton Clean Water Centre (WCWC) is to evaluate the application of Advanced Oxidation Processes (AOPs) involving Ozone and UV with the addition of hydrogen peroxide, as one of the methods used in the process of the removal of PPCPs and EDCs, or taste and odor. The amount of hydrogen peroxide used with UV is much higher than that used with the ozone application. The concern is the impact of the hydrogen peroxide on the chlorine residual in the water that is pumped to the distribution system. One of the methods used to deal with this problem is to increase the chlorine addition to maintain the required residual. That could increase the disinfectant by-products (DBPs), namely Trihalomethanes (THMs), in addition to increase to the cost of operation. The findings of these experiments would provide useful information regarding the AOPs application using ozone vs. UV with hydrogen peroxide.     

The Chemistry of Water Treatment Processes Involving Ozone,Hydrogen Peroxide and Ultraviolet Radiation

Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O₃ at high pH, 0₃/H₂0₂, O₃/UV and H₂O₂/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O₃/UV process, the effect of the H₂0₂:0₃ ratio in the O₃/H₂O₂ process, and the impact of the low extinction coefficient of H₂O₂ in the H₂0₂/UV process.     

Advanced Oxidation Treatment of Drinking Water: Part II. Turbidity,Particles and Organics Removal from Lake Huron Water

Pre-coagulation ozonation has been reported to be effective in drinking water treatment processes. Limited data are available on the impact of advanced oxidation processes (AOPs) on Lake Huron water which serves as a primary source of drinking water for many communities around the Great Lakes region. Impact of ozone/hydrogen peroxide based AOP on Lake Huron water was studied. The results show that AOPs can achieve higher particles removal in finished water and deliver improved filtered water turbidity compared to the conventional treatment process. Sharp decline in ultraviolet absorbance at 254 nm (UV₂₅₄) was observed immediately following AOP treatment while only minimal overall decrease in dissolved organic carbon (DOC) was achieved.     

Removal Of Pesticides By Use Of Ozone Or Hydrogen Peroxide/Ozone

This article deals with the efficiency of an ozonation step in drinking water treatment plants remove pesticides. These tests are carried out with a laboratory technique, the “OZOTEST” method, which simulates operating conditions on site and allows a complete oxidation assessment.

Efficiency of the two oxidant systems – ozone and ozone coupled with hydrogen peroxide – is evaluated for 11 pesticides commonly analyzed in control laboratories. Comparison of the two systems is made in terms of pesticide removal, but also in terms of ozone consumption. Matrix effects and contact time are also taken into account, and an order of reactivity for each system considered is suggested.     

Comparison of Different Advanced Oxidation Processes Involving Ozone to Eliminate Atrazine

The oxidation of the herbicide atrazine by advanced oxidation processes (AOP) has been studied. The experiments were carried out in a tubular photoreactor, 2.5 L capacity, capable of providing good contact between the liquid and gas reactants. The decomposition rate of atrazine was determined at different pH using UV radiation, Hydrogen Peroxide, Ozone, Ozone/UV, Ozone/H₂O₂, H₂O₂/UV and Ozone/H₂O₂/UV processes. The effect of three different pH values was studied (4.7, 6.8, 11.7).     

The Advanced Oxidation Process of Phenol Solution by O3/H2O2 in a Rotating Packed Bed

This article presents experimental investigation on the oxidative treatment of phenol in water by O₃/H₂O₂ in a rotating packed bed (RPB). It was found that the phenol degradation ratio increased with increasing rotation speed, initial pH value of phenol solution, and temperature. The degradation ratio of phenol had a peak value with increasing H₂O₂ concentration. The optimum operating conditions in this study were determined as an H₂O₂ concentration of 6.5 mM and a rotation speed of 1200 rpm. Phenol degradation ratio reached 100% at an initial phenol concentration of 40 mg/L in the O₃/H₂O₂ process.     

Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.