Ozone-based Oxidation Processes Research Articles

Degradation of chromosomal and plasmid encoded extracellular and intracellular resistance genes across different types and sizes in water matrices during ozone-based oxidation process

Antimicrobial resistance is a major and growing threat to public health and imposes significant environmental and economic burden worldwide. This study evaluates the degradation kinetics of resistance genes from ciprofloxacin (gyrAR), levofloxacin (qnrSR), tetracycline (tetAR), and mobile genetic elements (intl-1, plasmids) in water matrices by O3 treatment. For extracellular antibiotic resistance genes (e-ARGs) in deionized water, 3.6–5.2 logs removal was obtained, whereas intracellular ARGs (i-ARGs) in phosphate buffer saline, exhibited a removal of 3.5–4.5 logs at an O3 dosage of 3.7 × 10−2 M.s. While there was no significant impact of the wastewater matrix on e-gyrAR and e-intl-1 degradation as compared to deionized water (p > 0.05), the e-qnrSR reduction was higher (4.8–5.2 logs) at an ozone dosage of 3.7 × 10−2 M.s. For i-plasmid and e-plasmid encoded ARGs in wastewater, 4.0–5.5 logs removal was observed for the same dosage. Electrical Energy per Order (EEO, kWh/m3) was estimated, and the energy consumption on the degradation of the ARGs in the wastewater ranged between 0.68 and 1.1 kWh/m3. The findings of this study provide quantitative data for evaluating the fate and degradation of different ARG forms/types during ozone treatment of wastewater to mitigate the risk of AMR dissemination in the environment.

Advantages of ozone disinfection method for water purification over chlorine disinfection

The improvement of various advancements for water sanitization is a significant issue. Among numerous elective drinking water treatment advances, the well-known disinfectant techniques are ozonation and chlorination to treat drinking water. All through the ozonation procedure, it produces biodegradable organic by-products while in the chlorination process, some risky by-products (trihalomethanes and haloacetic acids) are generated. Because of the possible danger of these results, several water purification methods have been reported, such as ozonation, chlorination, UV, etc. During ozonation, exceptionally reactive hydroxyl radicals are produced, which has a crucial effect on purifying water. In this paper, we have discussed the wide use of ozone disinfectants for water treatment with an emphasis on radical chemistry of ozonization as well as advanced oxidation processes instead of the chlorination process, low-cost ozone generation processes, the impact of ozone and chlorine disinfectants on cryptosporidium oocysts, and the removal of seven strains microbes from drinking water. The favorable circumstances, hindrances of the utilization of ozone and chlorine in wastewater treatment, and their confinements in water treatment innovation just as the elective advances, for example, ozone-based oxidation process, catalytic ozonation, photocatalytic oxidation, and so on are additionally clarified in this paper.

Kinetics, Mechanisms and Ecotoxicity Assessment of Ozone-Based Oxidation Processes for Removal of Neonicotinoid Insecticide Clothianidin from Water

Kinetics, Mechanisms and Ecotoxicity Assessment of Ozone-Based Oxidation Processes for Removal of Neonicotinoid Insecticide Clothianidin from Water

Ozone-based advanced oxidation of biologically treated landfill leachate: Oxidation efficiency, mechanisms, and surrogate-based monitoring for bulk organics

Landfill leachate effluent obtained from partial nitrification-Anammox (PNA) biological treatment still contains various recalcitrant organics. In this study, ozone-based oxidation processes (O3 and O3/H2O2) were applied to treat PNA leachate effluent. The oxidation efficiency and mechanisms were investigated by measuring chemical oxygen demand (COD), biochemical oxygen demand (BOD5), molecular size, fluorescence, UV–vis absorbance, and electron-donating capacity (EDC). Given the challenge of efficient ozone dosing, a surrogate-based monitoring approach was proposed and evaluated. Results show that leachate variability caused significant variation in the ozone utilization efficiency (O3E) for COD removal. The O3E of O3 and O3/H2O2 ranged between 0.32 and 0.47 mgCOD/mgO3, and between 0.43 and 0.73 mgCOD/mgO3, respectively. Compared to O3, O3/H2O2 was more effective to remove COD, to degrade the high molecular fraction, and to enhance biodegradability. The two-stage pseudo-first-order model (R2 > 0.90) can well describe the degradation of COD, fluorophores, UVA330, UVA254, and EDC during O3 and O3/H2O2 treatment, and the degradation rate can be ordered as follows: fluorophores > UVA330 > EDC > UVA254 > COD. Particularly, COD reduction was correlated well with surrogate reductions (i.e., fluorophores, UVA330, EDC, and UVA254) in an exponential function (R2 > 0.90), while exhibiting different steepness depending on the degradation kinetics of surrogates. The increased BOD5 showed a trend from rising and decline when presented as a function as surrogate reductions. The above correlations demonstrate the potential of surrogates to replace the conventional parameters for oxidation optimization and control. Overall, this research enriches the knowledge in the oxidation of recalcitrant organics in leachate and provides a reference for efficient ozone dosing.

Synergistic effects of the combined use of ozone and sodium percarbonate for the oxidative degradation of dichlorvos

Dichlorvos or 2,2-dichlorovinyl dimethyl phosphate (DDVP) is a chlorinated organophosphorus pesticide which is frequently detected in the aqueous environment. In this study, an environmentally friendly and highly efficient oxidant, i.e., sodium percarbonate (SPC, Na2CO3·1.5H2O2) was introduced to an ozonation process for the degradation of dichlorvos (DDVP). Experimental results revealed an enhancement of DDVP degradation efficiency via the O3/SPC process compared with O3 alone due to the generation of reactive species (OH and CO3−) under various conditions. Both processes fitted the pseudo-first-order kinetic model and the reaction rate constant of the O3/SPC process under low SPC dosage (30 mg L-1) was more than two times higher than for O3 alone. The DDVP removal performance was evaluated in terms of initial pH, O3 dosage, SPC dosage and water matrix. The pH played a significant role in DDVP degradation during the O3/SPC process, especially on the occurrence of the different types of reactive species. Based on radical scavenger experiments, OH were observed over the full pH range but dominated under neutral and alkaline conditions, while less oxidative CO3- emerged at lower pH. Furthermore, the complex matrix of real wastewater inhibited the oxidation process due to the competition for oxidative species between organic matter and DDVP. A modified kinetic model based on a steady-state hypothesis was established to predict DDVP degradation via the O3/SPC treatment and provided a fair result under different conditions. This observation suggested that eco-friendly SPC could be considered as a promising alternative for H2O2 in developing sustainable ozone-based oxidation processes for recalcitrant compounds elimination in wastewater treatment.

Individual and simultaneous degradation of sulfamethoxazole and trimethoprim by ozone, ozone/hydrogen peroxide and ozone/persulfate processes: A comparative study

This study investigates the individual and simultaneous degradation and mineralization of the antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP) in aqueous solution by ozonation, ozone-activated persulfate (PS) and hydrogen peroxide (H2O2) processes. The trials were carried out in a semi-continuous column bubble reactor with an ozone diffuser located at the bottom of the column for a period of 2 h. Furthermore, the efficiency of studied processes were evaluated at two different initial pH and various doses of oxidants. The target compounds degradation observed pseudo-first-order rate constants (kobs) and removal of total organic carbon (TOC) using ozone-based oxidation processes were compared. Irrespective of the applied processes, the mineralization of target compounds was less effective than their degradation in both individual and simultaneous systems. The highest antibiotics degradation rate constants were observed for individual oxidation of TMP (kobs = 0.379 min−1) and SMX (kobs = 0.367 min−1) at alkaline initial pH (pH0) in the O3/H2O2 system at an [antibiotic]/H2O2 molar ratio of 1/1. Irrespective of the antibiotic studied, the most effective TOC removal (~44%) was observed after a 2-h treatment with the O3/H2O2 system at an [antibiotic]/H2O2 molar ratio of 1/5 (pH0 10.9). The O3/PS system at an [antibiotic]/PS molar ratio of 1/5 (pH0 10.9) proved the most effective system for both mineralization and degradation (kobs values of 0.294 min−1 and 0.266 min−1) of TMP and SMX, respectively, during the simultaneous oxidation of SMX-TMP. The decomposition by-products of SMX and TMP in studied ozone-based processes were identified using LC-MS analysis. The results of this study strongly suggest that using the O3/PS process is a promising solution to reduce SMX-TMP contamination in water matrices.

Diclofenac Degradation by Ozone-Based Oxidation Processes: PROMETHEE Method, Kinetic and Cost-Effectiveness Study

ABSTRACT In this study, the treatment of diclofenac (DCF), which is a pain reliever belonging to non-steroid anti-inflammatory drug group, was investigated by ozone-based oxidation processes. In experiments; pH (6–7) and 10 min reaction times were kept constant and the effects of different initial concentrations (5 mg/L, 10 mg/L and 20 mg/L), ozone doses (5 and 8 ppm), power of UV lamps (16 W and 32 W) and catalysts (0.1 g ZnO, In2O3, CuO and Fe2O3) were studied. Initially, studies were performed for the photocatalytic ozone oxidation process to determine which catalyst was more effective in DCF treatment, and study results were evaluated according to the PROMETHEE decision-making method. As a result of the evaluation based on DCF removal, energy consumption and cost parameters, ZnO was chosen as the best catalyst. In the following catalytic and photocatalytic ozone oxidation processes, studies continued with ZnO catalyst. In the second step of the study, the effect of DCF initial concentration, ozone dose and UV light intensity was determined. According to the results of the study, max degradation was obtained 100% in O3/UV/ZnO and O3/UV oxidation processes, at 5 mg/L DCF concentration, 5 ppm ozone dose, 16 W UV lamp and at 4- and 5-min reaction time, respectively. The highest total organic carbon (TOC) removal was obtained 76% in O3/UV/ZnO process. O3, O3/UV and O3/ZnO oxidation processes for 5 mg/L DCF were found to be better suited to pseudo-first-order kinetics rate model.

Removal of food soil by ozone-based oxidation processes: Cleaning and wastewater degradation in a single step

The cleaning of heat-treated cornstarch adhered to stainless steel is analyzed in a simulated Cleaning-In-Place system. The effects of temperature (20–60 °C), cleaning time (30–120 min), and ozone (0.00–42.30 g/Nm³) on both detergency and chemical oxygen demand (COD) are analyzed. Two mathematical models are proposed to evaluate the detergency and COD fitting satisfactorily the experimental results. The highest detergency is obtained at 60 °C and 120min, reaching 68 and 88% when the ozone concentration is 0.00 and 42.30 g/Nm3, respectively. Ozone diminishes the COD in the wastewater. Higher ozone concentration, cleaning time and temperature produces the greater reduction of COD/Detergency ratio. So, ozone promotes starch degradation, reducing the contamination charge of the wastewater during the cleaning process providing new possibilities for the optimization of cleaning processes in starch end-user industries by combining cleaning and depuration processes in a single step.

Removal Characteristics of Steroid Estrogen in the Mixed System through an Ozone-Based Advanced Oxidation Process

In this work, the removal of estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) in their coexisting micro-polluted solution through an ozone-based oxidation process was studied in depth. The results showed that all of the estrogens in the mixed solution could be completely degraded and their degradation processes fitted the pseudo-first-order kinetic model well. As the initial concentration of the mixed solution increased from 50 to 300 μg L−1, the removal rate constants of E1, E2, and EE2 decreased by 65.9%, 66.5%, and 67.0%, respectively. However, when the initial solution pH increased from 2.0 to 7.0, the removal rate constant of E1, E2, and EE2 increased by 271.4%, 149.7%, and 152.4%, respectively. When the H2O2 or UV was introduced into the ozonation system, the removal efficiency of steroid estrogens in the mixed solution was substantially enhanced. Moreover, main intermediates of E1, E2, and EE2 were proposed. The synthetic estrogen EE2 was chosen as the representative compound to evaluate the estrogenic activities during O3, O3/H2O2, and O3/UV processes. In the O3/H2O2 and O3/UV processes, the degradation products still possessed certain estrogenic activities, which led to a hysteresis of the decrease of estrogenic activity compared with that of the estrogen concentration. These findings provided some reliable research data, alternative oxidants, and oxidation manners for the removal of steroid estrogens from the aquatic environment.

Sequential application of Fenton and ozone-based oxidation process for the abatement of Ni-EDTA containing nickel plating effluents

Treatment of Ni-EDTA in industrial nickel plating effluents was investigated by integrated application of Fenton and ozone-based oxidation processes. Determination of integrated sequence found that Fenton oxidation presented higher apparent kinetic rate constant of Ni-EDTA oxidation and capacity for contamination load than ozone-based oxidation process, the latter, however, was favorable to guarantee the further mineralization of organic substances, especially at a low concentration. Serial-connection mode of two oxidation processes was appraised, Fenton effluent after treated by hydroxide precipitation and filtration negatively affected the overall performance of the sequential system, as evidenced by the removal efficiencies of Ni2+ and TOC dropping from 99.8% to 98.7%, and from 74.8% to 66.6%, respectively. As a comparison, O3/Fe2+ oxidation process was proved to be more effective than other processes (e.g. O3-Fe2+, O3/H2O2/Fe2+, O3/H2O2-Fe2+), and the final effluent Ni2+ concentration could satisfied the discharge standard (<0.1 mg L−1, China) under the optimal conditions (H2O2 dosage of 1.0 mL L−1, Fe2+: H2O2 mole ratio of 1.46, and reaction time of 10 min for Fenton reaction, initial influent pH of 3.0, O3 dosage of 252 mg L−1, Fe2+ of 150 mg L−1, and reaction time of 30 min for O3/Fe2+ oxidation). Furthermore, pilot-scale test was carried out to study the practical treatability towards the real nickel plating effluent, revealing the effective removal of some other co-existence contaminations. And Fenton reaction has contributed most, with the percentage ranging from 72.41% to 93.76%. The economic cost advantage made it a promising alternative to the continuous Fenton oxidation.

Energy saving potential of an air treatment system for improved building indoor air quality in Singapore

The design of air conditioning mechanical ventilation (ACMV) system affects the building energy performance and the indoor pollutant removal process. The present study aims to reduce energy consumption on ACMV systems by employing a renewable air treatment system (ATS). The ATS is able to purify the recirculated air through the ozone-based oxidation process and air scrubbing devices. The air purification performance of primary equipment in the ATS has been studied in order to demonstrate the capability to remove indoor air pollutants. Due to the air purification process, the ATS allows a reduced supply of outdoor-air translating to a lower cooling load. In addition, the reduced outdoor-air fraction results in an improved chiller efficiency. Therefore, the ATS is capable of achieving marked energy savings because of the reduced cooling load for conditioning outdoor airflow. The proposed ATS is particular adept during a period when Singapore faces periodic bad haze situations. Activating the ATS while decreasing the outdoor-air fraction can be an attractive solution. Based on Singapore climatic condition, an energy consumption analysis has been carried out to estimate the energy saving potential of the proposed ATS with varying outdoor-air intake. The “plug-and-play” ATS can be easily integrated into any new or existing ACMV systems to realize immediate improvement in indoor air quality and building energy efficiency.

Energy performance evaluation and application of an air treatment system for conditioning building spaces in tropics

The present study attempts to reduce the supply of outdoor air in conditioning building spaces for energy saving while improving the indoor air quality. A hybrid air treatment system incorporating a cooling system is introduced for tropical climates. The air treatment system (ATS) comprises an ozone-based oxidation process and an air scrubbing device. The air purification process has been experimentally investigated. Experimental results demonstrated the feasibility of the proposed ATS to provide improved indoor air quality. A validated mathematical model has been employed to study the air cooling and dehumidification process through the cooling coil. The reduced outdoor air intake facilitates a higher chilled water supply temperature resulting in an improved chiller performance and reduction of cooling load. The energy consumption performance of the proposed hybrid ATS air-conditioning system has been evaluated for an office building experiencing tropical climatic conditions. The cooling load on a design day has demonstrated that the reduction of outdoor air intake enabled marked energy savings potential in terms of the cooling demand. By analysing the building performance based on tropical climatic data, an annual energy consumption saving of up to 64.6kWh/m2 can be achieved via the hybrid ATS air-conditioning system.

Transformation of dissolved organic matter in concentrated leachate from nanofiltration during ozone-based oxidation processes (O3, O3/H2O2 and O3/UV)

In this study, the transformation of dissolved organic matter (DOM) in nanofiltration concentrated leachate during three ozone-based oxidation processes (i.e., O3, O3/H2O2 and O3/UV) was investigated. The transformation characteristics of DOM were evaluated by gel filtration chromatography (GFC), XAD-8 resin fractionation, excitation-emission matrix fluorescence spectroscopy (EEM) and Fourier transform infrared spectroscopy (FTIR). Compared with O3-alone process, the removal efficiencies of COD, TOC, and color were improved in O3-combined processes (i.e., O3/H2O2 and O3/UV) approximately by 10–15%, 7–15%, and 15–20%, respectively. Humic acid (HA) was completely degraded and preferentially reacted with the oxidants during ozonation processes. HA was first converted into fulvic acid (FA), and then the majority of these intermediates were further converted to hydrophilic fraction (HyI). The GFC results indicated that the broader molecular weight distribution of DOM was observed, and high molecular weight DOM (i.e., 0.45 μm–100 kDa) was successfully converted to low molecular weight organics in the range of 1–10 kDa after ozonation reactions. The EEM spectra also showed that HA and FA were effectively converted into HyI after ozonation for 90 min. It is suggested that ozone-based oxidation processes could effectively change the DOM distribution and fluorescence features of concentrated leachate.

Removal and reduction of selected organic micro-pollutants in effluent sewage by the ozone-based oxidation processes

Four typical organic micro-pollutants in effluent sewage were subjected to the various treatments using three ozone-based oxidation processes, i.e. individual ozonation (O3), ultrasonic ozonation (US/O3) and photocatalytic ozonation (PC/O3) under different experimental conditions involving supplied ozone dose, pH value and humic acid (HA) concentration of the effluent, ultrasonic radiation power, and photocatalyst dose. The target compounds, i.e. clofibric acid (CFA), nonylphenol (NP), 17α-ethinylestradiol (EE2) and carbamazepine (CBZ), were selected from 11 organic pollutants frequently detected in the aquatic environment through a developed screening system. The increase on the supplied ozone doses would improve the performances of ozonation of the target compounds. Besides, the removal rates of the compounds during the three ozone-based oxidation processes increased with the rise on pH value in the set range (3.7–9.5) of this study. However, the removal rates on the whole reduced with the increasing HA addition, especially during the US/O3 combined process. Compared with the individual O3, the two combined processes enhanced considerably the removal rates, by 13.9% or above for CFA, 12.6% or above for NP, over 13.3% for EE2, and no less than 14.8% for CBZ. The optimal removal of the target compounds was obtained at the ultrasonic power 240W for the ultrasonic ozonation treatment. For the PC/O3 combined process, the enhanced removal of the targets was mainly due to the larger amount of oxidizing species generated through the enhancement effects of photocatalysis as the adsorption of the targets to the photocatalyst was far less. The US/O3 combined process could achieve the best removal of the target micro-pollutants.

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.

Effects of reaction conditions on nuclear laundry water treatment in Fenton process

This study presents the efficiency of Fenton process in the degradation of organic compounds of nuclear laundry water. The influence of Fe 2+ and hydrogen peroxide ratio, hydrogen peroxide dose, pH and treatment time were investigated. The degradation of non-ionic surfactant and other organic compounds was analysed as COD, TOC and molecular weight distribution (MWD). The most cost-effective degradation conditions were at H 2O 2/Fe 2+ stoichiometric molar ratio of 2 with 5 min mixing and H 2O 2 dose of 1000 mg l −1. With the initial pH of 6, the reductions of COD and TOC were 85% and 69%, respectively. However, the removal of the organic compounds was mainly carried out by Fenton-based Fe 3+ coagulation rather than Fenton oxidation. Fenton process proved to be much more efficient than previously performed ozone-based oxidation processes.