Some Ozone Applications in Seafood

The use of ozonized seawater to reduce and eliminate bacterial pathogens in mariculture facilities and to extend shelf life of marine food products is demonstrated. Consequent benefits of this treatment are also discussed. Laboratory and pilot experiments were conducted using ozone gas to reduce disease-producing Vibrio sp. bacteria at a shrimp (Litopenaeus vannameii) hatchery in Ecuador, South America. Pacific Ocean seawater was treated in a 1,540 L capacity fiberglass contact tower (5–7 min retention) with an ozone oxidant residual of 0.07 mg/L. Prior to ozone treatment, Vibrio determined by TCBS plating was too numerous to count, causing shrimp to die of disease (30 tanks of 13,000 L each). After treatment, Vibrio counts and shrimp disease were eliminated, ozonized seawater decreased the time required for normal molting of shrimp and the total growth cycle was reduced by three days versus control water. From June 1991 until September 1992, survival rates of larval shrimp were robust, routine antibiotic addition was reduced, and one additional growth cycle was realized. Ozonized ice (fresh water) was prepared in the Milford Laboratory CT, USA; Gloucester Food Tech Lab, MA, USA; and a field station (brine water) for sockeye salmon (Oncorhynchus nerka) in Homer, AK. USA. In these studies, squid (Loligo pealei) and commercially captured salmon demonstrated a reduction in spoilage and extension of shelf life of 3 to 5 days' time using ozonized ice. Bacteria associated with commercial ice-producing machines were reduced by 4 logs using ozone treatment. In addition, no flavor aberration was noted using ozonized ice.     

Simultaneous elimination of two species of algae from a contaminated water through ozonation process: mechanism and destruction intermediates

An ozonation process was used for in situ removal of two species of green algae namely Oocystis sp. and Cosmarium sp. from a dam. According to the results, under the optimum conditions of the ozonation process 85.18% and 58% of Oocystis sp. and Cosmarium sp. were removed, respectively. Furthermore, the obtained results confirmed the main role of ozone molecules, and active hydroxyl radicals during the degradation mechanism. Also, chlorophyll-a concentration, SEM images, GC–MS technique proved the effectiveness of ozonation process for the complete and in situ removal of algal species.     

Research Note: Inactivation Efficiency of Ozonated Water for Fusarium oxysporum Conidia Under Hydroponic Greenhouse Conditions

Ozonated water was used for inactivation of Fusarium oxysporum conidia in sterilized water and inorganic soil-less nutrient medium at different treatment temperatures. F. oxysporum conidia were effectively inactivated in both water and nutrient media and the inactivation curves were almost same at 15°C, 25°C and 30°C. Approximate 4-log orders of F. oxysporum conidia were killed when the ozonated water with initial ozone concentration of 1.0 ppm had been used. The surviving curves, however, were characterized by a tailing-off effect, and the effect was related to the residual ozone concentration in the ozone treated suspensions.     

The Effect of Ozonation on Particle Size Distribution for Recirculating Aquacultural Seawater: Analysis of Particle Flocculation and Breakup

ABSTRACT

Solids removal is very important for water quality maintenance in recirculating aquaculture systems (RAS). Ozonation is a practical water treatment which can promote the solids removal. However, the characteristics of ozonation effects on particles are still unclear. In this study, the effect of ozonation on particle size distribution (PSD) was investigated for seawater from a RAS of Pacific white shrimp (Litopenaeus Vannamei). Both flocculation and breakup of particles were demonstrated during ozonation treatment, which resulted in changes of PSD. By using a fractal characteristic value (D_f), the flocculation process could be divided into three stages of preparation, growth and steady. Besides, the flocculation efficiency varied parabolically with contact time. A higher ozone dosage resulted in a shorter preparation stage, along with a longer growth stage (namely lasting a longer flocculation effect) and thus a relatively higher limit of parabolic flocculation efficiency. However, the limit would reach a peak and probably be accompanied with a more breakup of particles. The best flocculation efficiency was 43% at ozone dosage of 3.5 mg/L with 5 min contact time. Furthermore, a higher ozone dosage could produce more ammonia.     

Activated sludge process coupled with intermittent ozonation for sludge yield reduction and effluent water quality control

BACKGROUND: Ozone is applied in wastewater treatment for effluent water quality improvement (post‐ozonation) as well as for excess sludge reduction (in the recirculation line). There is some evidence that ozone dosed directly to aerobic biooxidation (ABO) process enhances degradation of recalcitrant compounds into intermediates, following their biodegradation in the same reactor. However, no information regarding the influence of ozone on sludge yield in this system was found. Therefore, the current work aimed to evaluate the effect of ozone on the sludge yield when ozone is dosed directly to the ABO process. In addition, batch and continuous treatment schemes for phenolic wastewater treatment are compared. RESULTS: The results revealed that an optimal ozone dose of ～30 mgO₃ L^?1 day^?1 reduced the sludge yield by ～50%, while effluent water quality in terms of total chemical oxygen demand (TCOD), compared with a conventional ABO process, was improved by 35.5 ± 3.6%. Slight improvement in soluble COD removal at the same ozone dose was also detected. The toxicity of effluent water was reduced as the ozone dose was increased. CONCLUSIONS: In an integrated ozonation‐ABO process it is possible to simultaneously reduce sludge yield and to improve effluent water quality, as COD and toxicity are reduced. Copyright © 2011 Society of Chemical Industry     

Experimental Investigation on the Microbial Inactivation of Domestic Well Drinking Water using Ozone under Different Treatment Conditions

The effect of ozonation on the microbial activities of domestic well drinking water was investigated, and the influence of the treatment conditions such as pH, temperature, ozone dose, and contact time was elucidated by comparing removal efficiencies. The results revealed that the disinfection of the microorganisms was related to an increase in contact time and thereby increases in Ct values with ozone. Higher ozone doses led to a large amount of microbial inactivation. The addition of hydroxyl and hydronium ions contributed greatly to the destruction of any microorganism in both acidic and basic mediums, achieving 25–88% efficiencies.     

Pilot-Plant-Scale Ozone and PEROXONE Disinfection of Giardia muris Seeded into Surface Water Supplies

PEROXONE is an advanced oxidation process for water treatment which is generated by combining ozone and hydrogen peroxide. In this study, surface water supplies were seeded with viable Giardia muris cysts and disinfected by ozone and PEROXONE in the pretreatment columns of a 22.7 L/min pilot plant. Inactivation was examined in two source waters under conditions of varying applied ozone doses (0.5–4.0 mg/L), with and without the addition of hydrogen peroxide; at increasing contact times (3, 6, 9, and 12 min); and with and without added high turbidity (10 and 50 NTU). Approximately 10⁸ viable G. muris cysts were injected into the ozone contactor-column influent. The cysts were collected at the ozone contactor-column effluent and concentrated, and viability was then determined using in vitro excystation.     

Effect of pH on inactivation of Microcystis aeruginosa by ozonation air in sequencing batch reactor

In this study, a mixture of ozone and air (ozonation air for short) was adopted for the inactivation of Microcystis aeruginosa in a sequencing batch reactor (SBR). Scanning electron microscopy of Microcystis aeruginosa revealed damage to the cell wall and leakage of intracellular contents after ozone oxidation. Owing to the destruction of cells, the chlorophyll a released from the cells was degraded by ozone oxidation, which showed that chlorophyll a concentrations increased vastly during the first 5 min, then, decreased continuously. pH in the SBR declined with increasing time, reaching around 3.0 at the end of the cycle. It was observed that the removal efficiencies of chlorophyll a were, respectively, 68.4%, 74.5%, 86.7% and 77.9% after 90 min at pH 3.0, 7.0, 9.0 and 11.0 conditions, and the degradation of chlorophyll a accorded with the apparent first‐order kinetics. The results suggested that inactivation of Microcystis aeruginosa was successfully performed by ozone treatment, verifying the potential of this alternative process for the decontamination of eutrophic water. Copyright © 2010 Society of Chemical Industry     

Comparative Analysis of Ozone and Ultrasound Effect on the Elimination of Giardia spp. Cysts from Wastewater

Giardia spp. is a flagellate protozoan that presents two evolution forms, cysts and trophozoites. Cysts are resistant to chlorine, the most employed disinfectant agent in the treatment of water. For this reason, new techniques for the disinfection of waters that contain this parasite are necessary. This work evaluated the efficiency of the disinfection by ozone and ultrasound individually and simultaneously upon wastewater. The data obtained showed that after application, ozone, ultrasound, and combined techniques induced a significant elimination of Giardia spp. cysts. Furthermore, this effect was more accentuated when the two techniques were applied simultaneously.     

The Impacts of New CT Requirements for Designing Ozone Systems for Cryptosporidium Inactivation

The impacts of new CT requirements for ozone disinfection of Cryptosporidium are evaluated using a desktop CT disinfection analysis. The analysis is applied to the design of new and upgraded ozone systems for two water treatment plants in Virginia. The results indicate that the feasibility of ozone disinfection of Cryptosporidium is dependent on ozone demand and decay characteristics of the water supply and may not be feasible for water supplies with moderate to high ozone decay rates. The CT analysis is a useful design procedure to evaluate the benefit-cost tradeoffs of using ozone to achieve alternative disinfection goals.     

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.     

Effect of Micro-Mixing Conditions on Predictions of Cryptosporidium Inactivation in an Ozone Contactor

The U.S. EPA is considering segregated flow analysis as an alternative calculation method to determine Cryptosporidium parvum inactivation credit in continuous-flow ozone contactors in drinking water treatment facilities. A computer method is presented in which C. parvum inactivation in the reactive flow segment of a hypothetical ozone contactor with a pre-determined residence time distribution is calculated based on the assumption of either completely segregated or completely micro-mixed flow. In a series of computer simulations using typical ozonation conditions in a water treatment facility, inactivation predicted assuming complete segregation was 0.3 to more than 2.0 log greater than that predicted assuming complete micro-mixing, depending on the level of back-mixing, ozone decomposition rate and inactivation level. CFSTR-in-series model predictions of inactivation were between those of segregated flow analysis and micro-mixed analysis. It was concluded that segregated flow analysis calculations may result in significant over-prediction of C. parvum inactivation credit in ozone contactors and should be used with caution.     

An electrolyte-free system for ozone generation using heavily boron-doped diamond electrodes

An electrolyte-free system for electrochemical ozone generation was developed using boron-doped diamond (BDD) electrodes as the anode and cathodes in combination with Nafion® N117/H⁺ as the separating membrane. Trials using BDD with various B/C ratios suggested that heavily boron-doped BDD with sp² impurities yielded high concentration of ozone. Further experiments by replacement of the feedstock solutions with 0.85 M Na₂SO₄ or 0.85 M NaCl resulted in no significant difference, suggesting that the use of pure water as the feedstock is the most appropriate method for ozone production. A high efficiency could be achieved by applying water as a feedstock for the anode and the cathode chambers. In addition, comparison with Pt electrodes confirmed that the excellent structural stability of BDD was the main factor contributing to this success.     

Efficacy of Ozonated Water Against Erwinia carotovora subsp. carotovora in Brassica campestris ssp. chinensis

Erwinia carotovora subsp. carotovora (Ecc) is a bacterial pathogen that causes decay of vegetables and is found in a wide range of Brassica crops in the Shanghai area, particularly in non-heading Chinese cabbage (NHCC). In this study, aqueous ozone was used as an antimicrobial agent to prevent the growth of Ecc bacterial colonies. Ecc that were treated with aqueous ozone were completely inactivated after the bacteria had been exposed to 0.5 mg/L ozone at 28 °C. Furthermore, a susceptible NHCC cultivar was directly sprayed with different concentrations of dissolved ozonated water as a pesticide substitute. The effects of the treatments on morphology were analyzed, and some treatments were characterized by induction of visible symptoms of senescence. No negative effects were observed after treatment by spraying ozonated water compared with the control at concentrations below 8 mg/L. However, visible damage to leaves was observed after the plants were exposed to 10 mg/L ozonated water via spraying for 15 days during the plant reproductive stage. Additionally, enzyme activities and antioxidant responses gradually increased to a certain degree and then decreased in the untreated and ozonated water-treated plants. These results showed that ozonated water was effective in restraining pathogens and potentially defending against disease in growing NHCC plants within a certain concentration range. These results provide a theoretical basis for preventing disease by applying ozonated water to vegetables as an alternative to pesticides.     

Transformation of the Β-Triketone Pesticides Tembotrione and Sulcotrione by Reactions with Ozone: Kinetic Study,Transformation Products,Toxicity and Biodegradability

Rate constants between ozone and triketone herbicides, tembotrione and sulcotrione, were determined between pH 2 and 12. Both compounds are completely transformed within seconds by ozone under real water treatment conditions. A reaction pathway was proposed based on the identification of transformation products. Toxicity evaluation using Vibrio fischeri test showed that a residual toxicity remained even after degradation of the major by-products, but biodegradation significantly increased from 50% to 70% for molar ozone to pesticide ratios from 0 to 2. Thus, ozonation coupled with biological treatment would drastically reduce the risk associated to the presence of triketone herbicides.     

Survival of Bacteria After Ozonation

The change of the bacterial population after each water treatment process was examined in a full-scale water treatment plant that uses ozone as a primary disinfectant. The fluctuation of heterotrophic bacterial number along the water treatment processes was determined. After ozonation, the bacterial number decreased to 13 CFU/mL. The surviving bacteria after each water treatment process were identified to genus or species level. The significant finding was the predominance of double-layered gram-positives (75%) among the surviving bacteria after ozonation. It included Mycobacterium spp., Bacillus spp., Corynebacterium spp., and Micrococcus spp. On the other hand, the dominance of gram-negatives was observed in most other water samples but each treatment process exerted different selection on dominant bacterial groups. The proportion of opportunistic pathogens was the lowest in the ozonated water.     

Pilot-Scale Ozone Inactivation of Cryptosporidium and Other Microorganisms in Natural Water

A pilot-scale study was conducted to evaluate the inactivation by ozone against Cryptosporidium oocysts, Giardia cysts, poliovirus, and B. subtilis endospores spiked into Ohio River water. The indigenous Ohio River populations of total coliform bacteria, heterotrophic plate count bacteria and endospores of aerobic spore forming bacteria were also evaluated. Endospores were the only organisms found to be more resistant to ozone than Cryptosporidium oocysts. Endospores may serve as an indicator of microbial treatment efficiency. Cryptosporidium oocysts were more resistant than Giardia cysts or poliovirus. Although HPC bacteria were less resistant than Cryptosporidium oocysts, variability limits their usefulness as an indicator of treatment efficiency. Ozone inactivation data generated in a pilot-scale study employing natural surface waters were comparable to inactivation data derived from previously published bench-scale studies using laboratory waters. The ozone requirements for inactivation of Cryptosporidium oocysts may produce elevated levels of bromate and ozone byproducts.     

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