Ozone-based Advanced Oxidation Processes Research Articles

Transformation of Contaminant Candidate List (CCL3) compounds during ozonation and advanced oxidation processes in drinking water: Assessment of biological effects

The removal of emerging contaminants during water treatment is a current issue and various technologies are being explored. These include UV- and ozone-based advanced oxidation processes (AOPs). In this study, AOPs were explored for their degradation capabilities of 25 chemical contaminants on the US Environmental Protection Agency's Contaminant Candidate List 3 (CCL3) in drinking water. Twenty-three of these were found to be amenable to hydroxyl radical-based treatment, with second-order rate constants for their reactions with hydroxyl radicals (OH) in the range of 3–8 × 109 M−1 s−1. The development of biological activity of the contaminants, focusing on mutagenicity and estrogenicity, was followed in parallel with their degradation using the Ames and YES bioassays to detect potential changes in biological effects during oxidative treatment. The majority of treatment cases resulted in a loss of biological activity upon oxidation of the parent compounds without generation of any form of estrogenicity or mutagenicity. However, an increase in mutagenic activity was detected by oxidative transformation of the following CCL3 parent compounds: nitrobenzene (OH, UV photolysis), quinoline (OH, ozone), methamidophos (OH), N-nitrosopyrolidine (OH), N-nitrosodi-n-propylamine (OH), aniline (UV photolysis), and N-nitrosodiphenylamine (UV photolysis). Only one case of formation of estrogenic activity was observed, namely, for the oxidation of quinoline by OH. Overall, this study provides fundamental and practical information on AOP-based treatment of specific compounds of concern and represents a framework for evaluating the performance of transformation-based treatment processes.

Ozone-based advanced oxidation processes for the removal of harmful algal bloom (HAB) toxins: a review

Ozone-based advanced oxidation processes for the removal of harmful algal bloom (HAB) toxins: a review

An Effective Heterogeneous Ozone-Based Advanced Oxidation Process in Acidic Solution— Ti-MCM-41/H2O2/O3

ABSTRACTA useful ozone-based advanced oxidation process in acidic solution- Ti-MCM-41/H2O2/O3 was studied, and acetic acid (HAc) was selected to be degraded because it is a hydroxyl radical-probe compound in ozonation. The results showed that only Ti-MCM-41/H2O2/O3 could effectively degrade HAc at initial pH 3.0, and that other oxidative processes such as O3, H2O2/O3 Ti-MCM-41/O3 and MCM-41/H2O2/O3, all could not, indicating the coexistence of Ti-MCM-41 and H2O2 was necessary for the generation of hydroxyl radicals under the experimental conditions. The optimization of parameters indicated that the rate of generation of hydroxyl radicals could be regulated by the amount of Ti-MCM-41, and that the amount of hydroxyl radicals could be controlled by the concentration of H2O2. The preceding results are of significance for effective treatment of acidic refractory wastewater.

A promising ozone-based advanced oxidation process for effective generation of hydroxyl radicals in acidic solution

The oxidative efficiency of H2O2/O3 in the presence or absence of titanium silicalite of TS-1 was investigated at pH value of 3.0, in which acetic acid was selected as the target organic compound owing to its inert to ozone. The removal rate of acetic acid by H2O2/O3 was negligible (5.6% in 30min) because of the impossible deprotonation reaction of H2O2 in acidic solution. However, addition of titanium silicalite of TS-1 could greatly improve the oxidative efficiency of H2O2/O3 (29% in 30min). The results of effects of different parameters such as concentration of H2O2, concentration of TS-1, rate of ozone input, and pH value, on the oxidative efficiency of TS-1/H2O2/O3 showed that the degradation of HAc by TS-1/H2O2/O3 was controlled by the transfers of reactants (including ozone and HAc) to the surface of TS-1. The tests of addition of tert-butyl alcohol and dimethyl sulfoxide (DMSO) both confirmed generation of hydroxyl radicals in this process. The rate of generation of hydroxyl radicals could be controlled by adjusting the concentration of H2O2. The mechanism for generation of hydroxyl radicals might be the reaction of some reactive oxygen species (including Ti(IV)-superoxide and Ti(IV)-hydroperoxide/peroxide), which resulted from the interaction of TS-1 with H2O2, with dissolved ozone. The results are of significance for the effective pretreatment of acidic wastewater containing refractory ozone-inert organic matter.

Advanced Oxidation Treatment of Recalcitrant Wastewater from a Wood-Based Industry: a Comparative Study of O3 and O3/UV

Ozone and ozone-based advanced oxidation processes were applied for the treatment of a recalcitrant wastewater generated by wood-based industries that contains different inorganic and organic constituents and high chemical oxygen demand (COD) varying between 3,400 and 4,000 mg/L. The investigation used a tubular ozone reactor combined with an UV reactor designed for different hydraulic retention times. The dependent variables addressed to evaluate the treatment efficiency were the reduction of COD and total organic carbon (TOC) and the biodegradability of the treated effluent based on respirometric studies using activated sludge from a wastewater treatment. The results showed that even though ozonation alone at acid pH promoted COD and TOC reductions of 65 and 31 % respectively, a decrease in the biodegradability was observed. The most effective treatment (COD and TOC reductions of 93 and 43 %, respectively) was obtained when applying ozone combined with UV light at basic pH. The ozone-UV combination was capable of increasing the amount of readily available COD by 75 % with an additional reduction of TOC by 60 %. In conclusion, ozonation at low pH effectively reduces the COD content in wastewater generated by the wood-based industry; however, in order to combine advanced oxidation with biological process, ozone combined with UV is recommended.

Hydroxyl radical formation during ozonation of multiwalled carbon nanotubes: performance optimization and demonstration of a reactive CNT filter.

We explored factors influencing hydroxyl radical (•OH) formation during ozonation of multiwalled carbon nanotubes (MWCNTs) and assessed this system's viability as a next-generation advanced oxidation process (AOP). Using standard reactivity metrics for ozone-based AOPs (RCT values), MWCNTs promoted •OH formation during ozonation to levels exceeding ozone (both alone and with activated carbon) and equivalent to ozone with hydrogen peroxide. MWCNTs oxidized with nitric acid exhibited vastly greater rates of ozone consumption and •OH formation relative to as-received MWCNTs. While some of this enhancement reflects their greater suspension stability, a strong correlation between RCT values and surface oxygen concentrations from X-ray photoelectron spectroscopy suggests that surface sites generated during MWCNT oxidation promote •OH exposure. Removal of several ozone-recalcitrant species [para-chlorobenzoic acid (p-CBA), atrazine, DEET, and ibuprofen] was not significantly inhibited in the presence of radical scavengers (humic acid, carbonate), in complex aquatic matrices (Iowa River water) and after 12 h of continuous exposure of MWCNTs to concentrated ozone solutions. As a proof-of-concept, oxidized MWCNTs deposited on a ceramic membrane chemically oxidized p-CBA in a flow through system, with removal increasing with influent ozone concentration and mass of deposited MWCNTs (in mg/cm2). This hybrid membrane platform, which integrates adsorption, oxidation, and filtration via an immobilized MWCNT layer, may serve as the basis for future novel nanomaterial-enabled technologies, although long-term performance trials under representative treatment scenarios remain necessary.

A pilot-scale investigation of ozonation and advanced oxidation processes at Choa Chu Kang Waterworks

A two-year comprehensive advanced oxidation processes (AOPs) pilot test was completed for a Singapore waterworks in 2011–2013. This study focused on oxidative removal of spiked organic contaminants with ozone and ozone-based AOPs (ozone application together with hydrogen peroxide, which is necessary for AOPs). The ‘optimized H2O2 dosage’ test philosophy was verified during the test period – keeping the residual ozone at 0.3 mg/L in the water for disinfection purpose by minimizing the H2O2 dosage. This study also monitored the bromate concentration in both ozone- and AOP-treated water, and all the samples reported below the laboratory detection limit (<5 µg/L), which is also lower than the WHO Guidelines for Drinking Water Quality (<10 µg/L). For comparison, a low pressure UV-based AOP test was conducted in the final stage of the study. The electrical energy per order (EEO) value is compared with ozone- and UV-based AOPs as well. The results indicated that ozone-based AOP with an optimized hydrogen peroxide dosage could be the most energy efficient option for this specific water matrix in terms of most selected compounds.

Removal of trace antibiotics from wastewater: A systematic study of nanofiltration combined with ozone-based advanced oxidation processes

This work did a systematic investigation on removal of trace antibiotics from wastewater treatment plant (WWTP) effluent through nanofiltration (NF), and disposal of the NF concentrate by advanced oxidation processes (AOPs). Four antibiotics, namely, norfloxacin (NOR), ofloxacin (OFL), roxithromycin (ROX) and azithromycin (AZI), which had high detection frequencies in effluents from WWTPs in Dalian (China), were selected as the target micropollutants. High rejections of antibiotics (>98%) were obtained in all sets of NF experiments. UV254 photolysis, ozonation and UV/O3 process were employed to treat NF concentrate. Results demonstrated that UV254 photolysis was not effective in degrading the four antibiotics, while ozone-based processes exhibited high removal efficiencies in 30min. A synergetic effect between O3 and UV was observed in degradation of the selected antibiotics during UV/O3 treatment. Generation of hydroxyl radicals in the process was testified using electron paramagnetic resonance (EPR) spin trapping technology. In treatment of NF concentrate from real secondary effluent, UV/O3 process achieved excellent removal efficiencies of antibiotics (>87%), a partial removal of dissolved organic carbon (DOC) (40%), an increase of BOD5/COD ratio (4.6 times), and a reduction of acute toxicity (58%). The study revealed that nanofiltration could efficiently remove antibiotics from WWTP effluent, and meanwhile, UV/O3 process was able to further eliminate the antibiotics in the NF concentrate effectively.

Transformation products of pharmaceutically active compounds during drinking water ozonation

Ozonation and ozone-based advanced oxidation processes have been shown to be effective in the oxidation of several pharmaceutically active compounds (PhACs) routinely detected in surface waters. Under typical operating conditions of these processes, most of the parent compound oxidized is expected to lead to the formation of transformation products (TPs). For a target ozone exposure, the resulting hydroxyl radical exposure depends on the water matrix or process chosen (e.g. peroxone) which in turn may influence the degradation pathway and the TPs formed. This study was undertaken to examine the expected impact that varying ozone and hydroxyl radical exposures may have on TP formation from the oxidation of PhACs during typical drinking water ozonation. Two representative PhACs were selected for the study. Carbamazepine was chosen to represent PhACs with a fast reaction rate with ozone (kO3 > 104 M−1 s−1) and bezafibrate was chosen to represent PhACs with a slow to moderate reaction rate with ozone (kO3 < 104 M−1 s−1). The results show that under varying ozone and hydroxyl exposure scenarios examined, the major oxidation pathway for the parent compound was dominated by reaction with ozone for carbamazepine while for bezafibrate it varied.

A bench-scale assessment of ozone pre-treatments for landfill leachates

Leachate from stabilized landfill can pose unique challenges to conventional biological wastewater treatment. Ozone-based advanced oxidation processes have garnered recent consideration as an option to reduce the organic strength and recalcitrance of aged landfill leachate. With a bench-scale investigation, the reported work examines the potential for leachate conditioning for further biological treatment by treatment with low-mg/L doses of ozone (0–7.5 mg/L O3). While not sufficient for significant organics mineralization, the tested ozone doses could potentially produce both selective and non-selective oxidation of recalcitrant leachate organic compounds leaving bio-available products in the pre-treated leachate. Leachate conditioning by O3 or O3/H2O2 was assessed via monitoring of three anthropogenic organic leachate contaminants(tris-(2-chloroethyl) phosphate, tris-(butoxyethyl)-phosphate and 17β-estradiol (E2)) with ozonation, and ozonation followed by anaerobic incubation. In addition, chemical oxygen demand (COD) and BOD5 analysis of the ozonated leachate, and methane and total gas formation during the anaerobic incubation were used to assess the degree of leachate conditioning. When treated with O3 alone, 58% removal of E2 was observed with an ozone dose of 4.5–5.4 mg/L. Direct oxidation of the three leachate contaminants was limited with O3/H2O2 pre-treatment. However, this pre-treatment was observed to have significantly improved degradation of E2 during anaerobic incubation of ozonated leachates (removal rate of E2 was 53.7% with 15 days of incubation), indicating the potential for ozone synthesized co-metabolism. However, overall anaerobic microbial activity was not significantly impacted by the applied ozone pre-treatments, as measured by methane formation, total gas formation, and COD removal during incubation.

Treatment characteristic of 1,4-dioxane by ozone-based advanced oxidation processes

The effectiveness of different ozone-based advanced oxidation processes on the treatment of 1,4-dioxane in aqueous solution was investigated in a lab-scale reactor. The removal efficiency of 1,4-dioxane was studied under different initial pH and H2O2 concentrations. Degradation (18%) of COD was observed with the application of UV-C alone, but the degradation of COD was greatly enhanced by a combined method, O3/H2O2/UV (94%). It appears, however, that an excess amount of hydrogen peroxide in the solution retards the decomposition of 1,4-dioxane. At pH 10 and an H2O2/O3 ratio of 0.5, 1,4-dioxane in aqueous solution showed the highest degradation rate.

Continuous determination of hydrogen peroxide formed in advanced oxidation and electrochemical processes

A hydrogen peroxide (H2O2) auto-analyzer was developed to continuously detect H2O2 present in water, using a flow injection analysis (FIA) technique, during several advanced oxidation processes (AOPs) involving H2O2, such as ozone/H2O2, UV/H2O2, and ozone/UV, and an electrochemical process. The analytical method was based on a fluorometric method, using the reaction of p-hydroxyphenyl acetic acid and H2O2 in the presence of peroxidase enzyme. H2O2 was analyzed within the high (100–2,000 μg/L) and low (0–500 μg/L) concentration ranges, using both long and short reaction coils, respectively. The standard deviation and detection limit were 0.5 and 1.6 μg/L, respectively, and the coefficient of variation at 1 μg/L was 7.8%. This study also investigated the effects of Na2S2O3 and NH4Cl, which were used to quench the ozone and hypochlorous acid (HOCl) present in the samples, on the measurement of H2O2 during the ozone-based AOPs and electrochemical process.

UV and UV/H2O2 Treatment: The Silver Bullet for By-product and Genotoxicity Formation in Water Production

Since Rook showed the production of trihalomethanes by drinking water chlorination, reaction product formation by chemical disinfection/oxidation has been thoroughly investigated. Originally, the focus was on the formation of individual organic products. After chlorination, trihalomethanes (THMs), haloacetic acids (HAAs) and many other halogenated compounds were found. After ozonation, ultraviolet (UV) disinfection and advanced oxidation, biodegradable organic by-products such as carboxylic acids were identified. All reaction products were formed by reaction with the organic water matrix (natural organic matter). Formation of reaction products from the inorganic water matrix proved to be an important issue as well. By ozonation and ozone-based advanced oxidation processes bromate was formed in bromide-rich water. By UV and UV/H2O2 treatment, nitrite was formed in nitrate rich water, especially when medium pressure (MP) UV lamps were applied. In addition to chemical characterization of individual reaction products the side effects of disinfection/ oxidation were investigated by genotoxicity testing. After chlorination a high response was found in the classic Ames test. After ozone and ozone based advanced oxidation a decrease of the response in the classic Ames test was observed, while after UV disinfection and UV-based advanced oxidation no significant effect was found. Modified genotoxicity testing such as in vitro Ames-II has been developed and applied on UV/H2O2-treated water. Once again no or just a small significant genotoxic response was observed after MP UV/H2O2 treatment in a system equipped with natural quartz sleeves. However, a substantially higher response was found after MP UV/H2O2 treatment in a system equipped with synthetic sleeves with a higher transmittance at lower wavelengths. The genotoxic response and the nitrite formation increased in the same order of magnitude, suggesting a relationship with the UV photolysis of nitrate. This was confirmed by UV photolysis of natural organic matter (NOM) and nitrate containing reconstituted water. The genotoxic effect was removed completely by post-treatment with granular activated carbon (GAC) filtration and/or dune infiltration.

Control of disinfection by-product formation using ozone-based advanced oxidation processes

The effects of ozone dosage, water temperature and catalyst addition in an ozonation-fluidized bed reactor (O3/FBR) on treated water quality and on the control of chlorinated and ozonated disinfection by-products (DBPs) were investigated. A biofiltration column was used to evaluate its removal efficiency on biodegradable organic matter and to reduce DBP formation. The Dong-Gang River, polluted by agricultural and domestic wastewater in Pingtung, Taiwan, was used as the water source. The treated water quality in terms of dissolved organic carbon (DOC), biodegradable DOC, ultraviolet absorbance at 254 nm (UV254) and specific UV absorbance (SUVA) improved with increasing ozone and catalyst dosages. Catalytic ozonation was more effective than ozonation alone at reducing the formation of DBPs at a given dosage. Experimental results show that water temperature had little effect on the treated water quality with the O3/FBR system used in this study (p>0.05). The combination of O3/FBR and the biofiltration process effectively decreased the amount of DBP precursors. The concentration of total trihalomethanes (TTHMs) was less than the maximum contaminant level (MCL) requirement, which is 80 μg/L, for all treated waters and the concentration of five haloacetic acids (HAA5) fell below 60 μg/L with an ozone dosage higher than 2.5 mg/L.

Removal of rhodamine B by ozone-based advanced oxidation process

The oxidation of rhodamine B in aqueous solution by conventional ozone process and the advanced ozone-based oxidation processes was investigated. The reaction conditions such as ozone dosage, initial concentration of the dye and pH in ozone process were optimized. The decolorization rate of rhodamine B increased with the ozone dosage but decreased with the initial concentration of rhodamine B. Three oxidative processes including UV/ozone, US/ozone and ozone systems were assessed to select the most appropriate oxidative process in terms of rhodamine B aqueous solution treatment and special emphasis was laid on the effect of reaction pH in the three methods. It was found that in all the three methods, the acid condition can promote the oxidation process. The UV/ozone process was the best ozone-based oxidization process, with the decolorization efficiency of 99.78% and COD removal rate of 47.43% after 15 min treatment. The pseudo-first order kinetics was found to fit all the ozone-based processes, with regard to the decoloration and degradation reactions.

Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments

Fenton treatment (Fe2+/H2O2) and different ozone-based Advanced Oxidation Processes (AOPs) (O3, O3/OH− and O3/H2O2) were evaluated as pre-treatment of a mature landfill leachate, in order to improve the biodegradability of its recalcitrant organic matter for subsequent biological treatment. With a two-fold diluted leachate, at optimised experimental conditions (initial pH 3, H2O2 to Fe2+ molar ratio of 3, Fe2+ dosage of 4mmolL−1, and reaction time of 40min) Fenton treatment removed about 46% of chemical oxygen demand (COD) and increased the five-day biochemical oxygen demand (BOD5) to COD ratio (BOD5/COD) from 0.01 to 0.15. The highest removal efficiency and biodegradability was achieved by ozone at higher pH values, solely or combined with H2O2. These results confirm the enhanced production of hydroxyl radical under such conditions. After the application for 60min of ozone at 5.6gO3h−1, initial pH 7, and 400mgL−1 of hydrogen peroxide, COD removal efficiency was 72% and BOD5/COD increased from 0.01 to 0.24. An estimation of the operating costs of the AOPs processes investigated revealed that Fe2+/H2O2 was the most economical system (8.2€m−3g−1 of COD removed) to treat the landfill leachate. This economic study, however, should be treated with caution since it does not consider the initial investment, prices at plant scale, maintenance and labour costs.

Bromate control in phenol-contaminated water treated by UV and ozone processes

Formation of bromate is of a great concern whenever ozone-based technologies are used for treating highly bromide-containing water ever since bromate was classified as a potential carcinogen. Saudi Arabian groundwater is coincidentally high in bromide content, and the potential of forming bromate during the treatment of such water is high. This study investigated the extent of bromate formation under different treatment conditions of ozone-based Advanced Oxidation Processes (AOPs) when used for the treatment of phenol-contaminated water. The results of the study showed that continuous ozonation at a rate of 1 L/min has completely removed 50 ppm of phenol from contaminated water in less than 5 min. However, as high as 8.85 ppm of bromate (BrO 3 −) was detected when treating the water which has high concentration of bromide ion (5 ppm). Results also showed that by adjusting the pH to 6 and adding ammonia (NH 3) at a dosage of 1.5 ppm, bromate formation was diminished drastically to non-detected levels.

Treatment of winery wastewater by ozone-based advanced oxidation processes (O 3, O 3/UV and O 3/UV/H 2O 2) in a pilot-scale bubble column reactor and process economics

The effectiveness of different ozone-based advanced oxidation processes (O 3, O 3/UV and O 3/UV/H 2O 2) on the treatment of winery wastewater was investigated in a pilot-scale, bubble column reactor. At the natural pH of the wastewater (pH 4) the effectiveness of each AOP followed the sequence: O 3/UV/H 2O 2 > O 3/UV > O 3 > UV-C. The rate of chemical oxygen demand (COD) and total organic carbon (TOC) removal were enhanced by operation at neutral (pH 7) and at alkaline pH (pH 10). The underlying chemistry involved in each of the AOPs is discussed and correlated with the observed reactivity. The rate of ozone consumption in the reactor with the O 3/UV and O 3/UV/H 2O 2 processes was in the range of 70–95% during the experiments, suggesting an effective use of the ozone supplied to the system. In all the experiments the disappearance of the winery wastewater organic load was described by pseudo-first-order apparent reaction kinetics. The fastest rate constant (6.5 × 10 −3 min −1), at the natural pH of the wastewater, was observed with the O 3/UV/H 2O 2 process under optimised oxidant dose (COD/H 2O 2 = 2). An economic analysis of the operating costs of the AOPs processes investigated revealed the O 3/UV/H 2O 2 to be the most economical process (1.31 Euro m −3 g −1 of TOC mineralised under optimised conditions) to treat the winery wastewater.

Pilot Scale Evaluation of MBR-AOP-BAC Treatments for Wastewater Reuse and Aquifer Recharge

Pilot Scale Evaluation of MBR-AOP-BAC Treatments for Wastewater Reuse and Aquifer RechargeThe City of Rio Rancho, New Mexico is expanding its water reuse system to supplement and sustain the water supply for this growing community of approximately 75,000 people within the Middle Rio Grande valley. This paper provides an overview of recently completed pilot testing of an ozone-based advanced oxidation process followed by a biologically activated carbon step to reduce wastewater-derived...Author(s)Robert MarleyGwinn HallVipul DholakiaShaun PorterTodd McEvoySourceProceedings of the Water Environment FederationSubjectSession 51: Looking to the Future: Advanced Treatment for ReuseDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2010ISSN1938-6478SICI1938-6478(20100101)2010:13L.3303;1-DOI10.2175/193864710798182042Volume / Issue2010 / 13Content sourceWEFTECFirst / last page(s)3303 - 3318Copyright2010Word count150Subject keywordsWater reuseaquifer rechargemembrane bioreactoradvanced oxidation processbiologically activated carbon

Kinetics and Modeling of IPA Oxidation Using Ozone-Based Advanced Oxidation Processes

In this study, an oxidation model incorporating the mass transfer and kinetics approach based upon the rate constants for the reactions with ozone and ·OH radicals was developed to predict the degradation of isopropyl alcohol (IPA) and formation of its main byproduct, acetone. The self-decomposition of ozone in buffered water at pH 3 and 7 occurred via a first-order reaction. The ozone mass transfer coefficients are considerably higher at pH 7 than pH 3 due to the participation in the chemical reaction toward the hydroxyl ion. The oxidation model considering side reactions between ozone or ·OH radicals and byproducts has been established using nonlinear simultaneous differential equations. The reaction coefficients for IPA degradation are 0.008, 0.0236, 1.4931, and 1.4909 s-1 at pH 3 and 7 in O3 and O3/UV processes, respectively. The larger reaction coefficient found in the ozone/UV system indicates several competing mechanisms for hydroxyl radicals.