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

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

Potential of Ozonated Water at Different Temperatures to Improve Safety and Shelf-Life of Fresh Cut Lettuce

The present study was carried out to determine the effect of ozonated water (2 mg L^?1) at different temperatures (4 °C and 15 °C) on the microbiological, color and sensory properties of lettuce. Cold ozone treatment (4 °C) significantly reduced the natural background microflora of lettuce. Salmonella Typhimurium and Escherichia coli inoculated on lettuce samples were insignificantly influenced by the temperature of water. During storage period at +4 °C for 14 days, the highest quality was observed from the samples treated with cold ozonated water. Ozone treatments did not affect the color properties and sensory quality of lettuce samples.     

Inactivation of Bacillus cereus and Salmonella enterica serovar typhimurium by Aqueous Ozone: Modeling and UV-Vis Spectroscopic Analysis

Antibacterial efficacy of aqueous ozone (O₃) against B. cereus vegetative cells and S. typhimurium by was studied by using GInaFiT tool and results were validated using UV-Vis spectroscopy. Ozone gas was generated using a domestic ozone generator. Buffer solutions containing known amounts (≈10⁸–10⁹ cfu/mL) of bacterial pathogens were treated with aqueous ozone (200 mg/hr or 0.1 mg/l) for 16 min with sampling at 0-, 0.5-, 1-, 2-, 4-, 8- and 16-min intervals. A reduction of 4.6 log of B. cereus and 7.7 log cycle reduction of S. typhimurium was obtained in 16 min. Biphasic shoulder and double Weibull models were good fit for the experimental inactivation kinetics data. Principal Component Analysis showed discrete grouping based on the time of treatment. The highest correct classification results for SIMCA were achieved for both B. cereus and S. typhimurium after 1 and 8 min of treatment, respectively. In partial least squares regression analysis, maximum R² values for calibration and validation were found to be 0.84, 0.80 for B. cereus and 0.90, 0.89 for S. typhimurium, respectively.     

Pilot-Scale Evaluation Of The Effects Of Mixing On Ozone Disinfection Of Escherichia Coli In A Semi-Batch,Stirred Tank Reactor

A research program was undertaken to examine the effects of mixing intensity and post-ozonation conditions on the survival of Escherichia coli ATCC 11775 in a high quality secondary wastewater effluent with a total organic carbon content of 8 mg/L and a chemical oxygen demand of 26 mg/L. The study was conducted using a pilot-scale, semi-batch stirred tank reactor with a 6-blade Rushton turbine. Two power conditions were investigated: 255 W/m³ and 870 W/m³. Two post-ozonation conditions also were investigated. In the first, a headspaceless sample was withdrawn and stored in the dark, in a quiescent condition. For the second, the gas flow to the reactor was stopped, but mixing was continued.

For equivalent contact times, it was found that two orders of magnitude more E. coli survived under the second post-ozonation condition when compared with the first condition. There was also a significant difference associated with the mixing intensity in the contactor, with the higher power input resulting in less efficient inactivation of E. coli.

The results confirm the importance of designing an ozone contactor to promote the maintenance of aqueous ozone in the contactor. In addition, optimum ozone mass-transfer may require different contacting conditions than those required for optimum disinfection performance. It was concluded that the design of ozone contactors should consider the use of at least two-stages: one optimized for ozone mass-transfer and one optimized for disinfection contacting.     

Quantification of the Bactericidal,Fungicidal, and Sporicidal Efficacy of the JLA Ltd. Ozone Laundering System

The objective of this study was to demonstrate the bactericidal, fungicidal, and sporicidal efficacy of the in-use concentration of ozone in solution generated continuously by the JLA Limited OTEX validated ozone laundering system against a range of typical microorganisms associated with laundering applications. The study used the JLA HC 100 laundering machine as the containment vessel. Test microbial suspensions were introduced directly into the drum of the laundering machine containing a known level of water in the presence of soluble ozone. Using standard microbiological techniques, the numbers of surviving bacteria, mold spores or bacterial spores were determined, and reductions in viable counts were calculated. The following test organisms were employed: Pseudomonas aeruginosa, Methicillin-Resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, E. coli, Acinetobacter baumannii, Aspergillus niger (spores), and Clostridium difficile (spores). All tests used multiple contact times of 0, 1, 3, 5, 7, 11 and 15 minutes at 20 °C±2 °C. Levels of ≤0.25 mg/L of dissolved ozone had minimal effect on the bacteria. Levels of >0.45 mg/L ozone showed good biocidal activity, except against Acinetobacter baumannii, which showed strong resistance to ozone. Against fungal spores, dissolved ozone levels of >1.2 mg/L were required to obtain a 2.8 log reduction. For Clostridium difficile spores, a dissolved ozone level between 0.90 and 1.20 mg/L gave >1.6 log reduction with no discernable spore recovery. In every instance, the control tests (no ozone) recovered levels of microorganisms that proved that the action of the laundering machine has no antimicrobial activity, and that the log reductions obtained are solely due to the effects of dissolved ozone.     

Removal of Escherichia coli after Treatment Using Ozonation-Ultrafiltration with Iron Oxide-Coated Membranes

The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the removal of Escherichia coli was studied. Commercially available ceramic membranes with a molecular weight cutoff (MWCO) of 5kDa were used as is, and also coated with iron oxide nanoparticles and sintered at 900°C. With membrane filtration and ozonation-membrane filtration using the uncoated membrane, 7 log removal of E. coli was achieved, as compared to 7.5 log removal with ozonation-membrane filtration with the coated membrane. A Live-Dead assay indicated that the mortality of E. coli in the product water was 15%, ～50%, ～86%, and >99% with membrane filtration, ozonation, combined ozonation-membrane filtration with the uncoated membrane and the coated membrane, respectively. With the coated membrane, the concentration of assimilated organic carbon (AOC) was reduced by up to 50% more than with the uncoated membrane filtration (with both systems operated using ozone). This indicates that there is a reduced potential for regrowth after treatment using the coated membranes and ozone. Scanning electron micrographs (SEM) of the membrane surface suggest that after filtration there is less detritus on the surface of the coated membrane than on the uncoated membrane. As a result of the inactivation of the E. coli and the lower AOC concentrations observed using combined catalytic ozonation-membrane filtration this process is likely to be very effective to both disinfect the water and control bacterial regrowth in the distribution system.     

Disinfection of recycled red‐meat‐processing wastewater by ozone

Ozonation of a real red‐meat‐processing wastewater was conducted in a semi‐batch reactor to explore the possibility of the water reuse. The experimental results revealed that ozone was very effective in disinfection of the red‐meat‐processing wastewater. After 8 min of ozonation with an applied ozone dose of 23.09 mg min^?1 liter^?1 of wastewater, 99% of aerobic bacteria, total coliforms and Escherichia coli were inactivated. Empirical models were developed to predict the microbial inactivation efficacy of ozone from the CT values for the real red‐meat‐processing wastewater. A correlation was also derived to estimate the CT values from the applied ozone dose and the ozone contact time. The results also revealed that under the ozonation condition for 99% inactivation of aerobic bacteria, total coliforms and E coli, the decrease in the chemical oxygen demand and the 5‐day biological oxygen demand of the wastewater were 10.7% and 23.6%, respectively. However, ozonation under this condition neither improved the light transmission nor reduced the total suspended solids (TSS) despite of the decolorization of the wastewater after ozonation. Copyright © 2005 Society of Chemical Industry     

Effect of pH and Importance of Ozone initiated Radical Reactions In Inactivating Bacillus subtilis Spore

The effect of pH on the inactivation of Bacillus subtilis spores with ozone in a batch reactor was examined in association with the role of OH radicals. The exact effect OH radicals have on ozone inactivation of microorganism is not well understood, although a direct reaction of molecular ozone has sometimes been emphasized. This study reports a novel observation that the presence of OH radicals plays a significant role in microbial inactivation. Considering the dependence of the ozone decay rate on pH, the observed C¯ T values for achieving a 2 log inactivation using the modified Chick-Watson model was 40 % lower at pH 8.2 compared to that at pH 5.6. In the presence of OH radical scavengers (tert-butanol), the observed change of C¯ T with pH was within 10%. This difference could be explained by the significant role of OH radicals.     

Inactivation of cryptosporidium at 1°c using ozone or chlorine dioxide

Inactivation of cesium chloride purified, bovine‐derived C. parvum oocysts was studied at bench‐scale using ozone or chlorine dioxide at 1°C. Experiments were conducted in 200 mL of 0.05 M phosphate buffer using a temperature controlled water bath. Animal infectivity using neonatal CD‐1 mice was used for evaluation of oocyst viability after treatment. The results showed that while the parasite could be killed at 1°C, the level of effort was substantially higher than that found at 22°C. An ozone Ct product (final residual and contact time product) of 7.2 to 15 mg‐min./L at pH 6.9 and 1°C resulted in an inactivation of 0.7 to 1.3 log‐units. This was about one‐third to one‐fifth of that observed at room temperature using a similar Ct product. A chlorine dioxide Ct product of 120 to 135 mg?min./L at pH 6.0 and 1°C resulted in an inactivation of 0.5 to 0.6 log‐units. This was about one‐fourth the kill observed at 22°C using a similar Ct product.     

Enhancing Biodegradability of Textile Wastewater by Ozonation Processes: Optimization with Response Surface Methodology

ABSTRACT

In this study, an ozonation process was used to increase biodegradability of textile wastewater by considering chemical oxygen demand (COD) and color removal. Response surface methodology was applied in order to determine the significance of independent variables which are initial pH, reaction time and ozone dose. While a biological oxygen demand (BOD)/COD rate of 0.315 was obtained at optimum conditions, which are pH 9, 75 min of reaction time and 26 mg/L ozone dose, color and COD removal was obtained at 74% and 39%, respectively. BOD/COD ratio value increased from 0.18 to 0.32 by ozonation process. In addition, k coefficient for BOD also increased from 0.21 to 0.30 d^?1.     

Ozone Inactivation of Pseudomonas aeruginosa,Escherichia coli,Shigella sonnei and Salmonella typhimurium in Water.

Based on the properties of ozone as a strong germicidal agent, inactivation kinetics of Pseudomonas aeruginosa, Escherichia coli, Shigella sonnei and Salmonella typhimurium towards ozone in water were studied. The values of 90% inactivation (t₉₀) obtained varied from 0.20 minutes (2.4 mg/L, Escherichia coli ATCC 25922) to 8.33 minutes (0.39 mg/L, Pseudomonas aeruginosa wild strain). First order inactivation kinetics with respect to both the concentrations of ozone and microorganisms were found, resulting an overall second order inactivation kinetics. The ATCC strains showed to be the most sensitive toward ozone among all. Meanwhile, the environmental isolation of Pseudomonas aeruginosa was the most resistant and Escherichia coli the most sensitive wild strain. The longest time required to achieve total inactivation was 35 minutes.     

Impact of Water Temperature on Resolving the Challenge of Assuring Disinfection While Limiting Bromate Formation

Intensive pilot studies were performed to study the impact of ozone dose (0.6 to 3.5 mg/L), pH (6.0 to 7.5), and contact time (12 to 38 min) on bromate (BrO₃) formation, for different sand-filtered water qualities from the Neuilly-sur-Marne Treatment Plant (COT = 1.3 to 2.2 mg/L, TAC = 190 to 230 mg CaCO₃, [Br^?] = 25 to 50 μg/L, and T = 5°C to 26°C). Whatever the water quality studied, the main factors influencing bromate formation were ozone dose, pH, and a cross factor between them. Bromate formation was shown to be proportional to bromide concentration, and to increase only slightly with temperature, depending on the ozone dose and the pH. As on the contrary temperature has an important impact on disinfection, especially when considering Cryptosporidium inactivation, resolving the challenge of ensuring disinfection while limiting bromate formation was shown to be quite easily achievable, at intermediate temperature, and with more stringent conditions at high temperature (because of bromate formation) or at low temperature (because of disinfection).     

DECOMPOSITION OF 4-NITROPHENOL BY OZONATION IN A HOLLOW FIBER MEMBRANE REACTOR

The effect of initial pH, liquid flow rate, gas flow rate, and gaseous ozone concentration on the ozonation of 4-nitrophenol in a membrane reactor was investigated. The results showed that the disappearance of 4-nitrophenol increased with the increase of liquid flow rate, gas flow rate, and gaseous ozone concentration. The rise of the initial pH value led to an increase in 4-nitrophenol removal rate, but the increase became negligible after initial pH exceeded 9.5. The highest removal efficiency of 4-nitrophenol achieved was 94% after 100 min reaction when gaseous ozone concentration was 0.51 mmol L^?1, gas flow rate was 57 mL min^?1, liquid recirculation rate was 72 mL min^?1, and initial pH was 10.3. The membrane reaction system could be modeled based on the lumped kinetics of 4-nitrophenol removal, and the corresponding rate constant of 4-nitrophenol removal was determined from the model.     

Process Control For Ozonation Systems: A Novel Real-Time Approach

For real-time control of ozonation processes in water works, a sequencing batch reactor was constructed to measure the ozone decay rate constant (k_O3) in short time intervals of about 15 min. The batch reactor is filled during the production process, immediately after dissolving ozone in water by a static mixer. On the basis of k_O3 and the initial ozone concentration ([O₃]₀), and the experimentally determined ratio of the concentrations of ^?OH radicals to ozone (R_ct), the degradation of micropollutants in ozone reactors (modeled as Continuously Stirred Tank Reactors - CSTRs) were calculated for compounds with known reaction rate constants with ozone and ^?OH radicals. Calculated degradation of atrazine, iopromide, benzotriazole and acesulfame are in good agreement with measured data. For acesulfame the following rate constants were determined in this study at 20 ^oC: reaction rate constant with ozone = 88 M^?1s^?1, reaction rate constant with ^?OH radical = 4.55?×?10⁹ M^?1s^?1. For the ozone reaction an activation energy of 35 kJ/mol was determined. Similarly to micropollutants, the relative inactivation of microorganisms (N/N₀) can be calculated based on the inactivation rate constant for ozone and if applicable the lag phase. The pI-value (=??logN/N₀) was introduced and implemented in the process management system to calculate online the log inactivation of reference microorganisms such as B. subtilis spores. The system was tested for variation of pH (6.5–8.5), DOC (1.2–4.2 mg/L) flowrate 3.2–12 m³/h and temperature (5.7–9 ^oC). Furthermore, a given pI-value, e.g. 1 for a 1-log inactivation of B. subtilis spores, can be set as control parameter in the process management system. The ozone gas flow is then adjusted until the set pI-value is reached. The process control concept was validated with B. subtilis spores. Generally, a good agreement was found between calculated and measured inactivation data. It was also demonstrated, that a constant ozone residual may lead to insufficient disinfection or overdosing of ozone. The new process control concept for ozonations based on onsite measurement of the ozone decay rate constant and the pI-value allows to assess disinfection and degradation processes quantitatively in real-time.     

Destruction of Helminth (Ascaris suum) Eggs by Ozone

Based on the properties of ozone as a strong germicidal agent, the inactivation kinetics or disintegration of Ascaris suum eggs in water were studied. Ozone was applied in synthetic samples, the concentration of dissolved ozone in the liquid phase was typically between 3.5 to 4.7mg/L, pH 5, 9. The value of 90% inactivation (t₉₀) obtained was at 1 h, the remaining 10% being inactivated in 2 h. A linear correlation between the logarithm of bacterial or yeast concentration (N) and contact time was found, being the linear significant correlation coefficient (r of 0.95). That 2-log inactivation occurred at a CT value near 4.7mg/min/L. The best reduction percentage was of 99.00 in 120min. It therefore could be demonstrated that ozone indeed induces effects on the helminth eggs.     

Ozonolysis Post-Treatment of Anaerobically Digested Distillery Wastewater Effluent

ABSTRACT

In this study, the ozonolysis of real anaerobically digested distillery wastewater (DWW) was carried out. The effect of operating parameters, such as pH, initial concentration, and ozone dosage, on the efficiency of ozone utilization, color removal, and sludge solubilization was studied. The highest ozone utilization of 99% was observed at the highest initial concentration (COD of 3000 mg/L) and lowest ozone flowrate (22.5 mg O₃/L/min), but with a very low color reduction of 20%, after 60 minutes of ozonolysis. To achieve a higher color reduction >80% and at ozone utilization >95%, the DWW had to be diluted twice (COD 1500 mg/L), and the flowrate doubled to 45 mg O₃/L/min. The reduction in color signified the oxidation of the color causing biorecalcitrant aromatic melanoidin compounds. This was confirmed by the 47% reduction in ultraviolet absorbance at 254 nm indicating the breakdown of the complex aromatic compounds into low molecular weight organics. Moreover, increases in average oxidation state from ?0.6 to ?0.2 suggested a decline in aromaticity and formation of easily biodegradable aliphatic compounds. The ozonolysis process was found to follow the first-order reaction kinetic model with the highest rate constant of 0.0326 min^?1 obtained. A reduction in suspended COD by 88% indicated solubilization of the sludge contained in the effluent.     

Ozonation of Reactive Orange 122 Using La3+-Doped WO3/TiO2/Sep Photocatalyst

La³⁺/WO₃/TiO₂/sep composites have been prepared by the sol–gel method. The degradation of dye was studied under the influence of various operational parameters such as initial pH, amounts of catalyst, concentrations of the dye, and ozone flow rate. The mineralization of Reactive Orange 122 has been confirmed by chemical oxygen demand measurements. The color removal of dye was found to follow a pseudo–first-order kinetics. Maximum color and chemical oxygen demand removal were 99.9% and 90% respectively, at a dye concentration of 200 mg/L, ozone flow rate of 2.0 L/min., 0.05 g/L weight of catalyst, and pH of 6.9 in 4 h. In addition, the catalyst was characterized by X-ray diffraction spectra, Fourier-Transform Infrared Spectroscopy, scanning electron microscopy, and a transmission electron microscope. This work could be a good candidate as a practical application for photocatalytic dye degradation.     

Enterococcus sp. Inactivation by Ozonation in Natural Water: Influence of H2O2 and TiO2 and Inactivation Kinetics Modeling

This article presents the results about the disinfectant power of treatments based on the application of ozone (578 mg O₃ h^?1) and ozone combined with TiO₂ (1 g L^?1) and H₂O₂ (0.04 mM) on Enterococcus sp., a bacteria indicator used in the control of water quality. The results show that all the ozone-based treatments under study achieve the inactivation of Enterococcus sp. solution in natural water. Moreover, the combination of ozone with H₂O₂ or TiO₂ lightly improves the inactivation of Enterococcus sp. compared to the ozonation. However, the treatment with O₃, H₂O₂ and TiO₂ is less effective than the use of O₃, O₃/H₂O₂ or O₃/TiO₂. Finally, the primary mathematical models are applied (Hom, biphasic and Mafart) and they adequately describe the disinfection kinetics of the ozonation treatments studied for Enterococcus sp.