Ozone Dose Research Articles

Preparation and application of Ag–Ce–O composite metal oxide catalyst in catalytic ozonation for elimination of Reactive Black 5 dye from aqueous media

It is necessary to treat textile effluents before discharging them into natural water bodies as they harm the environment. Compared to conventional treatment methods, catalytic ozonation has gained attention due to its effectiveness in removing refractory organic pollutants. In this study, the coprecipitation method was used to synthesize a composite metal oxide of silver and cerium oxide, and the synthesized catalyst was used to eliminate the Reactive Black 5 (RB5) dye. X-ray diffraction, scanning electron microscopic, and Brunauer–Emmett–Teller surface area analyses were performed to characterize the synthesized catalyst. Afterwards, relevant experimental parameters, such as pH, ozone and catalyst dosages, and initial dye concentration, were investigated. The experiments revealed that the optimal experimental conditions were a pH value of 10, a catalyst dosage of 0.7 g/L, and an ozone dosage of 60 L/h. In these optimized conditions, the RB5 dye was entirely removed, and a chemical oxygen demand removal efficiency of 88% was achieved within a reaction time of 80 min. Furthermore, the recycling potential of the catalyst was tested for three cycles, and no deterioration in its activity was observed. Additionally, studies were conducted using a hydroxyl radical scavenger in order to understand the reaction pathway of the system. As a result, the indirect pathway was more dominant than the direct pathway in the system.

Modeling and optimization of synergistic ozone-ultraviolet-chlorine process for reclaimed water disinfection: From laboratory tests to software simulation.

The ozone-ultraviolet (UV)-chlorine process is a highly effective method of disinfection in water reuse system, but currently still lacks precise quantification and accurate control. It is difficult to determine the dosage of each disinfectant because of the complex interactions that occur between disinfection units and the complicated mathematical calculation required. In this study, we proposed a dosage optimization model for ozone-UV-chlorine synergistic disinfection process. The model was able to identify the cost-effective doses of the disinfectants under the constraints of microbial inactivation, decolorization, and residual chlorine retention requirements. Specifically, the simulation of microbial inactivation rates during synergistic disinfection process was accomplished through quantification of the synergistic effects between disinfection units and the introduction of enhancement coefficients. In order to solve this optimization model rapidly and automatically, a MATLAB-based software program with graphical user interface was developed. This software consisted of calibration unit, prediction unit, assessment unit, and optimization unit, and was able to simulate synergistic ozone-UV-chlorine process and identify the optimal dose of ozone, UV, and chlorine. Validation experiments revealed good agreements between the experimental data and the results calculated by the developed software. The developed software is believed to help the water reclamation plants improve disinfection efficiency and reduce the operational costs of synergistic disinfection processes.

Case Study of Ozone Bagging Adjuvant Therapy in Wagner II and III Diabetic Foot Ulcers on Wound Healing Process: Three Patients Recovered Completely

Background: Diabetic foot ulcer is a chronic complication of diabetes mellitus in the form of ulceration with or without infection. Diabetic foot ulcers that are not handled properly can cause damage to the foot that requires amputation. Wound care techniques for treating diabetic foot ulcers are starting to develop, one of which is ozone bagging therapy. This ozone bagging therapy in diabetic foot ulcers is reported to be useful as an anti-microbial effect, increasing glycemic control, increasing insulin sensitivity, preventing oxidative stress, increasing fibroblast proliferation, and increasing the release of growth factors. This case study will report 3 patients with Wagner II and III-foot ulcers who healed completely within 28 days using ozone bagging treatment as an adjuvant. Methods: 3 patients with diabetic foot ulcers Wagner II and III received ozone bagging therapy every 4 days for 7 sessions (a total of 28 days) as an additional therapy besides treating moist gauze using NaCl. This study used a Medical Ozone Generator. The dose of ozone used with medical oxygen is 1 lpm, flow 0.6, in the first session "high dose" with an output dose of 80-100 mg/l and in the 2nd-7th session with a low dose (25-35 mg/l). Macroscopic assessment of the wound using the Wagner scale and the progress of each treatment session is documented in photographs. Results: On macroscopic measurements, the process of wound healing leading to wound closure was better in the treatment group and was taken as a case for 3 patients who recovered completely. It resulted in 3 patients who recovered completely with a measurement of the Meggitt-Wagner scale of 0.26. Conclusion: For these recovered patients, there was a decrease in VEGF, TGF-β, and PDGF levels. The VEGF, TGF-β, and PDGF levels tested were VEGF, TGF-β, and PDGF levels in wound exudate by comparing them on the 3rd day. 1st and 12th day. Supported by macroscopic data showing that the wound healing process was better in the group that received ozone bagging therapy as an adjuvant. From this study it was found that the trend of decreasing levels of VEGF, TGF-β, and PDGF in wound exudate occurred because the inflammatory and proliferative processes in the treatment group lasted more faster than the control group. Keywords: ozone bagging therapy, diabetic ulcers, wound exudate, growth factors, VEGF, TGF-β, and PDGF, Meggitt-Wagner scale.

Removal of Disperse Yellow-42 Dye by Catalytic Ozonation Using Iron and Manganese-Loaded Zeolites

In this research, the efficiency of the catalytic activity of iron and manganese-loaded (bimetallic) sodium zeolite was investigated for the ozonation-based removal of disperse yellow 42 dye. The impregnation method was used to deposit Fe and Mn on the surface of sodium zeolite. The morphological analysis of sodium zeolite before and after Fe and Mn deposition was conducted by SEM, EDX, and FTIR. It was found that several variables, including the ozone dose, contact time, pH, catalyst dose, and hydroxyl radical scavenger action, greatly influenced the efficiency of dye removal. The chemical oxygen demand (COD) removal by catalytic ozonation using Fe and Mn-loaded sodium zeolite from real dye textile wastewater was also investigated. After 30 min of treatment with catalytic ozonation at pH 6, the maximum 73% removal of disperse yellow 42 dye was achieved with a catalyst dose of 0.5 g and an ozone dose supply of 1.8 mg/min. In catalytic ozonation with the hydroxyl radical scavenger effect (HRSE), the decline in removal efficiency from 73% to 61% demonstrated that removal efficiency was highly dependent on hydroxyl radical production. The COD removal efficiency in the real textile wastewater was 59% with the ozonation process, which increased to 79% after catalytic ozonation.

Assessing the efficiency of ozone-based advanced drinking water treatment processes in removing antibiotics and antibiotic-resistant genes: Pilot-scale research

With the widespread use of antibiotics, the emergence of antibiotics and antibiotic resistance genes (ARGs) poses a potential threat to public health. Drinking water plants are both the source and sink of these pollutants. In this study, we investigated and analyzed the distribution of four major types of antibiotics and ARGs in a drinking water plant with advanced treatment processes (ozone and activated carbon units) located in the central region of China. Among these treatment processes, the ozone process had significant removal effects on antibiotics and resistance genes, ranging from 15.10–91.17 % and 0.07–1.27 log, (except for ermA and qnrD) respectively. A correlation analysis of the concentrations of antibiotics and ARGs revealed a significant correlation (0.95 < r < 1) between antibiotics and ARGs, as well as between different types of ARGs. Additionally, the mechanism of ozone in the lab- and pilot-scale tests was analyzed to improve the removal capacity of ozone units for target pollutants. The experimental results showed that the removal efficiency of antibiotics and ARGs by ozone could be effectively improved by increasing the ozone dosage (5 mg/L), pH (9), and reaction time (10 min). The removal efficiency of the pollutants ranged between 36.65 % and 96.01 %. Under optimal reaction conditions, the results of the pilot-scale ozone experiment were significantly better than the actual treatment effects in drinking water plants. Our findings provide a theoretical basis for the optimization of the ozone process in actual drinking water plants.

Efficient removal of organic matters and typical odor substances in rural drinking water using Ozone-BAC-UF combined system to meet new water quality standards in China

China has just implemented new drinking water quality standards, canceling the provisions detailed in the previous standards that allowed relatively lenient water quality standards in rural areas, and unifying the water quality requirements for urban and rural areas. In rural areas of China, lakes are important sources of drinking water, but their water typically contain high concentrations of organic pollutants. In addition, removal odorous substances from such sources is challenging. In response to these issues, an ozone-biological activated carbon-ultrafiltration process is proposed and its efficiency in drinking water treatment is explored. The results indicate that O3-BAC pretreatment significantly improved the efficiency of the membrane process in removing organic and odor substances. At an ozone dosage of 2 mg/L, with granular activated carbon as filler and an EBCT of 25 min, the O3-BAC pretreatment allowed removal rates in the membrane system equal to 71.5% of CODMn, 84.2% of UV254, as well as 92.2% and 92.5% of GSM and 2-MIB, respectively, the latter being typical odor compounds. In addition, the function and diversity of the microbial communities in the reactor were evaluated under different pretreatment conditions at different stages: functionally specific microorganisms were enriched in different systems, and some microorganisms contributing to the removal of organic and odorous substances were identified. The effluent from the combined Ozone-BAC-UF process consistently met the new requirements for drinking water in China, implying that the combined system has significant potential for practical applications for drinking water treatment in rural areas.

Effects of Different Ozone Doses Added to the Antibiotic Treatment on Cytokine Levels in Experimental Sepsis Model

We aimed to examine the changes caused by ozone therapy added to the antibiotic treatment on proinflammatory and anti-inflammatory cytokine levels in an experimental sepsis model formed with E. coli endotoxin. Rats were divided into 6 groups of 10 rats. Sepsis was formed by dosing 5 groups of rats with intraperitoneal E. coli endotoxin injection. For the first 3 groups, 0.6 mg/kg, 0.9 mg/kg, and 1.1 mg/kg doses of ozone therapy were added to the antibiotic treatment and group-4 only received antibiotic treatment. Group-5 was not treated. Group-6 received intraperitoneal serum physiologic injection simultaneously with the other groups. All treatments were sustained for 5 days. IL-1, IL-10, and TNF-alpha levels were detected in blood serum taken from rats sacrificed on day 6. It was seen that IL-1, TNF-alpha levels are significantly lower than the levels in other groups that received ozone therapy. In the comparisons amongst the groups receiving ozone therapy, it was observed that IL-1 levels do not have a significant difference and TNF-alpha levels are significantly lower in the two groups receiving lower doses than the group receiving a higher dose. There were no significant differences detected between groups at serum levels of IL-10 which is an anti-inflammatory cytokine. It was concluded that ozone added to the antibiotic treatment in sepsis could have a positive effect on survival rates by suppressing inflammatory process.

Effects of ozone treatment to the levels of neurodegeneration biomarkers after rotenone induced rat model of Parkinson’s disease

The study investigated the effects of ozone treatment on the neurodegeneration of stereotaxic rotenone-induced parkinson's disease (PD) model. The model was confirmed using the apomorphine rotation test. α-synuclein, amyloid-β, Tau, phosphorylated Tau, as well as tyrosine hydroxylase(+), nNOS(+), and glial cell counts were used to evaluate neurodegeneration in the substantia nigra pars compacta and ventral tegmental area. The experiment involved 48 Sprague-Dawley rats divided into four groups: dimethyl sulfoxide (DMSO), DMSO with ozone (O), DMSO/rotenone (R), and D/R/O. Ozone treatment significantly improved tissue α-synuclein level and TH+, nNOS+, and glial cell counts compared to the rotenone-only group. The study suggests that ozone treatment may have beneficial effects on PD biomarkers in the rotenone model. Further studies on ozone dosage, duration, and administration methods in humans could provide more evidence for its potential use in Parkinson's disease treatment.

A novel insight of degradation ibuprofen in aqueous by catalytic ozonation with supported catalyst: Supports effect on ozone mass transfer

Catalytic ozonation is an effective wastewater purification process. However, the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency (OUE), poor organic degradation performance, and high energy consumption. Therefore, there is an urgent need to develop efficient supported catalysts that can enhance mass transfer and performance. However, the reaction mechanism of the support on ozone mass transfer remains unclear, which hinders the development of catalytic ozonation applications. In this study, lava rocks (LR)-supported catalysts, specifically CuMn2O4@LR and MnO2Co3O4@LR, were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity, stability, and high OUE. Addition of CuMn2O4@LR or MnO2Co3O4@LR increased IBP removal efficiency from 85% to 91% or 88%, and reduced energy consumption from 2.86 to 2.14 kWh/m3 or 2.60 kWh/m3, respectively. This improvement was attributed to LR-supported catalysts enhancing mass transfer and promoting O3 decomposition to generate •OH and •O2−, leading to IBP degradation. Furthermore, this study investigated the effects of ozone dose, supporter sizes, and catalyst components on ozone-liquid mass transfer. The results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass transfer. Larger-sized LR (kLa= 0.172 min−1) exhibited better mass transfer compared to smaller-sized supports. Based on these findings, it was concluded that both CuMn2O4@LR and MnO2Co3O4@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater, and LR showed good credibility as a catalyst supporter. Understanding the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.

Facing the treatment of polymedicated effluents using gaseous ozone electrochemically generated

The degradation of antibiotics in hospital urine, as alternative to reduce the chemical risk of hospital effluents, is evaluated by gaseous ozone electrochemically generated in Polymer Electrolyte Membrane (PEM) cells. Firstly, the influence of the current density in the electrochemical step is evaluated. The results indicate that ozone gas with rates ranging from 0.034 to 1.111 mg O3 min−1 can be produced by applying current densities of 21–125 mA cm−2. Then, the degradation of Penicillin G (Pen G) by electrochemically generated ozone is evaluated. Results show that the degradation rate is dependent on the ozone dose flow rate and the aeration system plays a crucial role in enhancing the efficiency of the ozonation process by reducing the limitations associated with gas-liquid mass transfer. Under the optimal conditions, using an ozone dosage of 1.111 mg O3 min−1, 100 % efficiency of Pen G (50 mg dm−3) removal in hospital urine is achieved after 13 min, resulting in a ratio of 1.04 mg Pen G removed per mg O3 supplied. Finally, the efficiency of electrogenerated gaseous ozone for treating a simulated polymedicated hospital urine (using data from the University Hospital Complex of Albacete (Spain) as case of study) is tested. The findings suggest that the chemical risk associated with hospital urine is mitigated (reducing antibiotic activity by 100 %) by breaking down pharmaceutical compounds into simpler molecules that no longer possess antibiotic properties. Degradation efficiencies over 2 g (kWh)−1 make of this treatment a cost-effective alternative to treat hospital effluents.

Surface atomic oxygen species mediated the in-situ formation of hydroxyl radicals on Fe3C decorated biochar for enhancing catalytic ozonation

Developing highly efficient and anti-interference catalysts was still a challenge for the practical application of heterogeneous catalytic ozonation (HCO) in water decontamination. Herein, a magnetic Fe3C decorated biochar (Fe3C/BC) was prepared for HCO to achieve efficient degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The Fe3C/BC catalytic ozonation system promoted the degradation ratio of 2,4-D from 58.7% (ozonation alone) to 90.0% within 10 mins when the ozone dosage was 1.0 mg/L. And the observed degradation rate constant (kobs) of 2,4-D under catalytic ozonation system was 2.58 times that of ozonation alone. Fe3C/BC exhibited negligible adsorption on 2,4-D but with a significant enrichment to ozone, which realized the cooperating process of “adsorption-catalysis” at the solid–liquid interface, thus avoiding the ineffective decomposition of ozone. The dissociative adsorption of ozone molecules on the surface Fe3C generated surface atomic oxygen species (O* and O2*), which mediated the in-situ formation of hydroxyl radicals (·OH). ATR-FTIR, in-situ Raman, isotope tracing tests, and theoretical calculations were used to disclose the interface reaction processes and reveal the ·OH formation mechanism. Free radical reactions at the interface efficiently avoid the interference of coexisting ions dissolved in water. The presence of 3 mM (183 mg/L) bicarbonate had essentially little effect on the degradation of 2,4-D. The consecutive use of Fe3C/BC did not influence its catalytic performance and stable structure. This study provided new insight into the ·OH-dominated interfacial reaction in the HCO process.

Rebuilding high-quality near-surface ozone data based on the combination of WRF-Chem model with a machine learning method to better estimate its impact on crop yields in the Beijing-Tianjin-Hebei region from 2014 to 2019

In recent years, the problem of surface ozone pollution in China has been of great concern. According to observation data from monitoring stations, the concentration of near-surface ozone (O3) in China has gradually increased in recent years, and ozone concentration often exceeds the contaminant limit standard, especially in the Beijing-Tianjin-Hebei (BTH) region. High O3 concentration pollution will adversely affect crop growth, which can cause crop yield losses. Therefore, it is urgent to recognize the situation of ozone pollution in the BTH region and quantitatively evaluate the crop yield losses caused by ozone pollution to develop more effective pollution prevention and control policies. However, the monitoring of ozone concentration in China started relatively late compared with some developed countries, and currently, long-time series data covering the BTH region cannot be obtained, which makes it difficult to evaluate the impact of ozone on crop yield. Therefore, a new method (WRFC-XGB) was proposed in this study to establish a high-precision near-surface O3 concentration dataset covering the whole BTH region from 2014 to 2019 by integrating the Weather Research and Forecasting with Chemistry (WRF-Chem) model with the extreme gradient boosting (XGBoost) machine learning algorithm. Through verification with ground observation station data, the results of WRFC-XGB are satisfactory, and R2 can reach 0.78–0.91. Compared with other algorithms, the accuracy of the near-surface ozone concentration dataset is greatly improved, which can be used to estimate the impact of surface ozone on crop yield. Based on this dataset, the yield loss of winter wheat, rice, and maize caused by O3 pollution was estimated by using the response equation of the relative yield and ozone dose index. The results showed that the total yield losses of winter wheat, rice and maize from 2014 to 2019 were 2659.21 million tons, 49.23 million tons and 1721.56 million tons due to ozone pollution in the BTH region, respectively, and the highest relative yield loss of crops caused by O3 pollution could be 29.37% during 2014–2019, which indicated that the impact of ozone pollution on crop yield cannot be ignored, and effective measures need to be developed to control ozone pollution, prevent crop production loss, and ensure people's food security.

The role of noble metals in TiO2 nanotubes for the abatement of parabens by photocatalysis, catalytic and photocatalytic ozonation

The role of modified TiO2 nanotubes (TNTs) with noble metals was studied for photocatalysis, catalytic and photocatalytic ozonation of a paraben’s mixture. The TNTs were obtained by anodization and were modified by photodeposition with 0.25 mol% of Au, Pt or Pd.Results showed that solar photocatalysis led to higher degradation than UVA radiation, and under UVA radiation, the use of 3 Pt-TNTs (3 TNTs plates modified with Pt) and 3 Pd-TNTs present the same effect as the use of 5 and 7 pristine-TNTs plates, respectively. The best parabens removal was achieved for Pd-TNTs under UVA radiation and pristine TNTs under solar radiation, with 43% and 81% removal in 120 min, respectively.All the catalytic and photocatalytic ozonation experiments led to less ozone consumption than single ozonation (transferred ozone dose (TOD) = 5.27 mgO3/L) with total parabens abatement. Catalytic ozonation experiments suggest that the presence of metals can promote the formation of oxidative radicals, with the Au-TNTs presenting best performance (TOD ≈ 3.59 mgO3/L) while pristine TNTs led to TOD = 4.98 mgO3/L. For photocatalytic ozonation, the pristine TNTs led to the lowest ozone consumption (TOD = 3.74 mgO3/L).Moreover, the use of hydroxyl radical scavenger showed that hydroxyl radical is formed during single and photocatalytic ozonation mechanism, which should be related to the natural and surface catalytic ozone decomposition.

Effectiveness of Ozonation for Improving the Microbiological Safety of Fresh-Cut Parsley (Petroselinum crispum) Leaves

In the last decade, fresh-cut plants have become a more popular flavoring additive in food. It is important to find an effective method for ensuring the safety and quality of plant materials used as food additives. Ozonated water is being considered by the EFSA for approval as a cidal agent for plant protection. The objective of this study was to evaluate the effectiveness of ozonated water in improving the microbial safety of fresh-cut parsley leaves, with a particular focus on mesophilic and psychrotrophic bacteria and fungi. The yeasts and bacteria were identified with the MALDI-TOF MS system. Color changes on the surface of the parsley samples were measured in the CIE L*a*b trichromatic color model. The chemical composition of the essential oil was evaluated via gas chromatography with mass spectrometry (GCMS). The microbial level of the fresh leaves varied and depended on the season. The highest microbial levels were found in the leaves picked in the summer and autumn, at 104 to 106 CFU/g for fungi and 106 to 108 CFU/g for bacteria. Among the isolates with the highest isolation frequency, bacteria belonging to Pseudomonas fluorescens, Staphylococcus warneri, and Bacillus megaterium dominated. The dominant yeasts and molds were Candida sp., Rhodotorula sp., Cladosporium sp., and Fusarium sp. The conditions for water ozonation (ozone dose and time) were established for both mono- and mixed cultures. Time of 3 min, ozone content of 0.5, O3 mg/L or 1 min, and 1.5 mg of O3 mg/L were sufficient for a 90% reduction in the number of living microorganisms. Yeasts and bacteria were sensitive to ozone treatment, excluding P. fluorescens rods. The tested mold strains were the most resistant. However, it was noted that organic matter might reduce the decontamination effect. The effectiveness of ozonation was negatively influenced by organic compound content above 1%. Spectrophotometric measurements of parsley leaves after ozonation, especially after 3 min treatment at 1.5 O3 mg/L, revealed morphological changes. The CIELAB color space (L*a*b*) changed in the direction of lightness and yellowness; however, ΔE showed no statistically significant differences in comparison with the untreated leaves. In preliminary studies, no differences were noted in GLC-MS chromatograms for essential oils of parsley leaves before and after ozonation. The aroma of parsley treated with ozonated water was more intensely herbal than the control sample, probably due to the higher content of α and β phellandrene. The results of this study show that decontamination of parsley leaves by ozonated water containing 1.5 O3 mg/L in a closed 5 min process can effectively ensure the microbiological quality of fresh-cut parsley leaves. It can be concluded that ozone treatments in aqueous form appear to provide promising qualitative and quantitative results for the decontamination of this fresh-cut plant material. However, more work is necessary to study chemical and volatilome changes. Especially the sensory analyses should be conducted before and after ozone treatment.

Influence of Gaseous Ozonation on Bio-Techno-Functionality, In Vitro Nutrient Digestibility, and Molecular Properties of Red Sorghum Flour

ABSTRACT The current investigation aimed at evaluating the effect of different applied ozone dosages of 32.0, 38.0, 44.0 and 50.0 g.kg−1 on techno-functional properties, structural properties, molecular interactions and thermal properties of red sorghum flour. Ozonation led to an increase in the water absorption capacity (1.79 to 2.15 g/g), water solubility index (1.59 to 5.13%), oil absorption capacity (1.27 to 1.71 g/g), swelling power (7.68 to 8.31 g/g), foaming capacity (10.14 to 13.91) and stability and paste clarity (19.35 to 34.30%T); however, there was a decrease in the gel consistency (95.50 to 40.20 mm), flour dispersibility (92.36 to 89.21%), emulsion activity (8.50 to 7.00%) and stability (32 to 22.20%). This alteration in the functional properties could be attributed to the cleavage of various groups due to oxidation and resulting in increased electronegativity. Ozonation enhanced the total phenolic content (226.34 to 276.23 mg GAE/100 g), FRAP activity (8.14 and 12.65 µmol TE/g), in vitro starch digestibility while reduced the total flavonoid content (605.26 to 582.15 mg QE/100 g), DPPH (10.90 to 9.61%RSA) and in vitro protein digestibility. Scanning electron microscopy and Fourier transform infrared microscopy showed modification in the structure and molecular interaction attributing to the widening of the protein and compactness of the starch. Pearson’s correlation coefficient and Principal component analysis (PCA) were employed for studying the relationship between different variables and for validation of changes due to ozonation.

Pre-ozonation for gravity-driven membrane filtration: Effects of ozone dosage and application timing on membrane flux and water quality

Gravity-driven membrane (GDM) filtration has been proposed as an alternative to sand filtration for drinking water treatment, but its low membrane flux and poor permeate quality hinder its widespread application. This study investigated the effect of pre-ozonation (with various dosages and application timings) on membrane flux, fouling layer characteristics, and permeate quality during GDM filtration of river water. Pre-ozonation with 3 mg/L ozone increased the mean membrane flux by 9–54%, resulting in approximately 30% increased water production and reduced dissolved organic carbon (DOC) and extracellular polymeric substance (EPS) production by 12–35% and 9–18%, respectively. The timing of pre-ozonation significantly affected the time-dependent flux behavior and morphological characteristics of the fouling layers. Pre-ozonation from the beginning of GDM filtration enhanced the initial flux because of organic fouling control but showed a gradual flux decline with time due to EPS accumulation and biologically inactive fouling layers. Pre-ozonation from the middle of GDM filtration period created heterogeneous and porous membrane fouling layers with high biological activity, showing increased membrane fluxes and improved permeate quality by removing DOC and assimilable organic carbon (AOC) via the combined action of ozone oxidation and biodegradation/sorption in the fouling layer. Overall, our results demonstrate pre-ozonation as a potential option to overcome the limitations of GDM filtration.

Optimizing Ozone Disinfection in Water Reuse: Controlling Bromate Formation and Enhancing Trace Organic Contaminant Oxidation.

The use of ozone/biofiltration advanced treatment has become more prevalent in recent years, with many utilities seeking an alternative to membrane/RO based treatment for water reuse. Ensuring efficient pathogen reduction while controlling disinfection byproducts and maximizing oxidation of trace organic contaminants remains a major barrier to implementing ozone in reuse applications. Navigating these challenges is imperative in order to allow for the more widespread application of ozonation. Here, we demonstrate the effectiveness of ozone for virus, coliform bacteria, and spore forming bacteria inactivation in unfiltered secondary effluent, all the while controlling the disinfection byproduct bromate. A greater than 6-log reduction of both male specific and somatic coliphages was seen at specific ozone doses as low as 0.75 O3:TOC. This study compared monochloramine and hydrogen peroxide as chemical bromate control measures in high bromide water (Br- = 0.35 ± 0.07 mg/L). On average, monochloramine and hydrogen peroxide resulted in an 80% and 36% decrease of bromate formation, respectively. Neither bromate control method had any appreciable impact on virus or coliform bacteria disinfection by ozone; however, the use of hydrogen peroxide would require a non-Ct disinfection framework. Maintaining ozone residual was shown to be critical for achieving disinfection of more resilient microorganisms, such as spore forming bacteria. While extremely effective at controlling bromate, monochloramine was shown to inhibit TrOC oxidation, whereas hydrogen peroxide enhanced TrOC oxidation.

Evaluation of the prediction of micropollutant elimination during bromide ion-containing industrial wastewater ozonation using the ROH, O3 value

The composition of the wastewater matrix influences the oxidation potential of ozonation, a technique widely recognized efficient removal of micropollutants. Here, we developed a chemical kinetic model to determine the ozone dose required to minimize bromate production in wastewater containing bromine ions while achieving target removal rates. In wastewater ozonation, ozone decomposition comprises instantaneous ozone consumption and subsequent decomposition at first-order reaction rates. Under the injection condition of 1.5 g O3/g dissolved organic carbon (DOC), the instantaneous ozone demand was 62.7% of the injection concentration, and it increased proportionally with increasing injected ozone concentration. Ozone and hydroxyl radical exposures were proportional to the initial ozone dose, while hydroxyl radical exposure was proportional to ozone exposure, and the deviation was relatively high at 1.0–1.5 g O3/g DOC. The calculated hydroxyl radical exposure was 3.0 × 10−10 to 5.3 × 10−10 M s. Ozone and hydroxyl radicals are highly correlated with the ratio of ozone dose to organic matter concentration. Therefore, a trace substance removal rate evaluation model combined with the ROH, O3 model and a bromate generation model were also considered. For ibuprofen, the ozone dose for achieving the target removal rate of 80% while maintaining the bromate concentration below 50 μg L−1 was suitable in the operating range of 0.86 g O3/g DOC or more. The proposed method provides a practical operation strategy to calculate the appropriate ozone dose condition from the target compound removal rate prediction and bromate generation models considering the ratio of ozone dose to organic matter concentration in the incoming wastewater.

Removal of contaminants of emerging concern from the supernatant of anaerobically digested sludge by O3 and O3/H2O2: Ozone requirements, effects of the matrix, and toxicity

Digestate is a rich source of nutrients that can be applied in agricultural fields as fertilizer or irrigation water. However, most of the research about application of digestate have focused on its agronomic properties and neglected the potential harm of the presence of contaminants of emerging concern (CECs). Aadvanced oxidation processes (AOPs) have proved to be effective for removing these compounds from drinking water, yet there are some constrains to treat wastewater and digestate mainly due to their complex matrix. In this study, the feasibility to remove different CECs from digestate using O3 and O3/H2O2 was assessed, and the general effect of the matrix in the oxidation was explained. While the lab-scale ozonation provided an ozone dose of 1.49 mg O3/mg DOC in 5 h treatment, almost all the compounds were removed at a lower ozone dose of maximum 0.48 mg O3/mg DOC; only ibuprofen required a higher dose of 1.1 mg O3/mg DOC to be oxidized. The digestate matrix slowed down the kinetic ozonation rate to approximately 1% compared to the removal rate in demineralized water. The combined treatment (O3/H2O2) showed the additional contribution of H2O2 by decreasing the ozone demand by 59–75% for all the compounds. The acute toxicity of the digestate, measured by the inhibition of Vibrio fisheries luminescence, decreased by 18.1% during 5 h ozonation, and by 34% during 5 h O3/H2O2 treatment. Despite the high ozone consumption, the ozone dose (mg O3/mg DOC) required to remove all CECs from digestate supernatant was in the range or lower than what has been reported for other (waste-)water matrix, implying that ozonation can be considered as a post-AD treatment to produce cleaner stream for agricultural purposes.

Surface ozone risk to human health and vegetation in tropical region: The case of Thailand

Tropospheric ozone (O3) is a threat to vegetation and human health over the world, in particular in Asia. Knowledge on O3 impacts on tropical ecosystems is still very limited. An O3 risk assessment to crops, forests, and people from 25 monitoring stations across the tropical and subtropical Thailand during 2005–2018 showed that 44% of sites exceeded the critical levels (CLs) of SOMO35 (i.e., the annual Sum Of daily maximum 8-h Means Over 35 ppb) for human health protection. The concentration-based AOT40 CL (i.e., sum of the hourly exceedances above 40 ppb for daylight hours during the assumed growing season) was exceeded at 52% and 48% of the sites where the main crops rice and maize are present, respectively, and at 88% and 12% of the sites where evergreen or deciduous forests are present, respectively. The flux-based metric PODY (i.e., Phytotoxic Ozone Dose above a threshold Y of uptake) was calculated and was found to exceed the CLs at 1.0%, 1.5%, 20.0%, 1.5%, 0% and 68.0% of the sites where early rice, late rice, early maize, late maize, evergreen forests, and deciduous forests can grow, respectively. Trend analysis indicated that AOT40 increased over the study period (+5.9% year−1), while POD1 decreased (- 5.3% year−1), suggesting that the role of climate change in affecting the environmental factors that control stomatal uptake cannot be neglected. These results contribute novel knowledge on O3 threat to human health, forest productivity, and food security in tropical and subtropical areas.