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.     

Formation of Bromate and Chlorate during Ozonation and Electrolysis in Seawater for Ballast Water Treatment

Many effective technologies have been developed and approved for ballast water treatment, and the effectiveness of a process should be evaluated considering its environmental friendliness. The aim of this study was to evaluate the formation and formation mechanisms of bromate (BrO₃^?) and chlorate (ClO₃^?) in seawater during ozonation, electrolysis, and a combined (ozonation/electrolysis) process. In seawater ozonation, BrO₃^? was generated exceeding a 5 mg/L ozone dose despite the high Br^? (65 mg/L). The formation of BrO₃^? and ClO₃^? by electrolysis depended on the electrode materials where two types of electrodes (IrO₂/Ti and Pt/Ti) were used. The combined (ozonation/electrolysis) process generated much higher levels of BrO₃^? and ClO₃^? than either individual process. In ozonation or electrolysis, mixed oxidant including HOCl/OCl^? and HOBr/OBr^? is the main parameter for inactivation, which is called total residual oxidant, TRO. In this study, a predictive model for BrO₃^? and ClO₃^? was suggested in terms of TRO formation. This predictive model can recommend allowable TRO (generated by ozonation or electrolysis) for practical applications in seawater treatment.     

Disinfection of Seawater: Application of UV and Ozone

Ozone and ultraviolet technologies are proposed as potential disinfecting agents for seawater. Ozone doses were applied in the range 0.38 to 4.89 mg O₃ L^?1. They permit to observe a complete disinfection as well as UV doses superior to 320 J L^?1. Impacts of both processes on organic matter were also studied. UV absorbances were reduced in both cases but in higher proportion using ozone (up to 50% removal). Total organic carbon was slightly reduced by UV radiation, and ozonation achieves up to 10% mineralization. Ozone reaction proceeds with biochemical oxygen demand increase. Seawater ozonation, in addition, leads to the formation of residual oxidants that show an inhibitory effect on autochthonous microorganisms.     

Resistance of Fusarium sp spores to solar TiO2 photocatalysis: influence of spore type and water (scaling‐up results)

BACKGROUND: Common irrigation water disinfection methods, which may be unable to inactivate all types of pathogens or even become phytotoxic themselves, are not very effective in controlling phytopathogens. Water disinfection by photocatalysis is a promising irrigation‐water treatment for destroying phytopathogens without the drawbacks of conventional disinfection methods. Previous research has shown that solar photocatalytic technology can be used in the disinfection treatment of bacteria, protozoa and fungi, either through solar disinfection only. The purpose of this work was evaluate the TiO₂ photocatalysis process to inactivate Fusarium spores in distilled and well water. RESULTS: This paper reports on the ability of solar photocatalysis to inactivate Fusarium spores in a solar bottle reactor and in a new 60 L compound parabolic collector (CPC) prototype reactor. Inactivation of Fusarium sp spores by titanium dioxide (Degussa P25) was evaluated in distilled and natural well water. The experiments were carried out using 5 or 6 h exposure to natural sunlight at the Plataforma Solar de Almeria (Southeast Spain). The highest Fusarium spore inactivation rate during experiments was achieved with a 30 L min^?1 flow rate and 100 mg L^?1 TiO₂ concentration. Three different Fusarium spores (microconidia, macroconidia and chlamydospores) were individually evaluated to determine whether there were differences in resistance to the photocatalytic treatment. The results showed that chlamydospores were the most resistant, followed by macroconidia, and finally microconidia were the most sensitive. CONCLUSIONS: Microconidia, macroconidia and chlamydospores in distilled and well water were inactivated with TiO₂ slurry in a 60 L CPC photoreactor, demonstrating for the first time that it is possible to scale‐up photocatalytic treatment for use and reuse of water for irrigation. Copyright © 2010 Society of Chemical Industry     

Ozone Application for Postharvest Disinfection of Tomatoes

Ozone is an effective alternative for the postharvest treatment of fruits and vegetables. The purpose of this study was to evaluate the ozone application in gaseous or aqueous phases for postharvest disinfection of tomatoes (Lycopersicon esculentum Mill) cultivar FA-180. Fruits harvested at the breaker stage were exposed to ozone concentrations of 25 and 45 mg m^?3 for 2 h per day during 16 days, at non-controlled temperature and relative humidity. Exposure to ozone during storage extends the shelf-life of tomatoes, besides preserving its sensory attributes. Mature tomatoes, inoculated with Escherichia coli ATCC 25922, were washed with ozonated water containing 0.5 to 1.0 mg L^?1 during 15 to 30 min. To achieve an adequate disinfection, 1 mg L^?1 and 15 min are recommended. The disinfection with ozonated water was effective.     

Ozone Disinfection Of Urban Storm Drain Water

Concerns regarding bacteria in runoff entering Santa Monica Bay were validated by the isolation of human enteric virus in storm drain effluents. As an alternative to chlorination, ozonation was investigated for disinfection of dry-weather urban runoff. Ozone at 10-20 mg/L reduced coliform counts an average of 3.4-logs, with 6-log maximal disinfection. Although varying contaminant concentrations complicate the analyses, total organic carbon predicted ozone demand, and effluent coliform counts were correlated with ozone residuals.     

Control of corrosive water in advanced water treatment plant by manipulating calcium carbonate precipitation potential

The corrosion of metal pipes in water distribution networks is a complex electrochemical and physicochemical phenomenon between a metal surface and corrosive water. The level of corrosion in water distribution systems was controlled by manipulating the calcium carbonate precipitation potential (CCPP) concentration, and the corrosive water quality was controlled in two steps within the advanced water treatment plant (AWTP) constructed at the Institute of Water Quality Research (IWQR), Busan Metropolitan City, Korea. The 1 ^st control step was located before a coagulation process included on a rapid mixer, and the 2 ^nd control step was located after a biological activated carbon (BAC) process. The capacity of the AWTP in IWQR was 80 m³/day. The CCPP concentration was controlled from the calcium hardness, alkalinity, and pH by adding calcium hydroxide (Ca(OH)₂), sodium carbonate (Na₂CO₃), and carbon dioxide (CO₂) in the above two steps. A CCPP control system was installed and operated according to the developed algorithm to maintain a CCPP range of 0–4 mg/L. The CCPP range was reasonably controlled to induce the formation of a CaCO₃ film on the surface of the simulated water distribution system (SWDS). From the result of the corrosive water control, the CCPP formed greater than 0.0 mg/L. The crystalloid structure of the scale produced by CCPP control in the inner surface of pipe was zinc carbonate hydroxide hydrate (Zn₄CO₃(OH)₆·H₂O).     

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).     

Evaluation of Process Control Alternatives for the Inactivation of Escherichia coli,MS2 Bacteriophage,and Bacillus subtilis Spores during Wastewater Ozonation

Dissolved ozone concentration integrated over time (CT) is a reliable indicator of disinfection efficacy in drinking water treatment. However, ozone CT may not be measurable in some wastewater ozone applications. In this study, alternative process control parameters, specifically ozone to total organic carbon (O₃:TOC) ratio, differential UV₂₅₄ absorbance (ΔUV₂₅₄), and differential total fluorescence (ΔTF), were correlated with the inactivation of Escherichia coli, the bacteriophage MS2, and Bacillus subtilis spores in five secondary wastewater effluents. CT values greater than 9 mg-min/L were generally required for measurable inactivation of B. subtilis spores, and CT values of 1 and 2 mg-min/L consistently achieved greater than 6- and 5-log inactivation of MS2 and E. coli, respectively. The O₃:TOC, ΔUV_254, and ΔTF correlations for MS2 and B. subtilis were useful for predicting inactivation, while those of E. coli were characterized by greater variability. [Supplementary materials are available for this article. Go to the publisher's online edition of Ozone: Science & Engineering for the following free supplemental resources: additional figures and data tables.]     

Stabilized and Immobilized Bacillus subtilis Arginase for the Biobased Production of Nitrogen‐Containing Chemicals

L ‐Ornithine could serve as an intermediate in the biobased production of 1,4‐diaminobutane from L ‐arginine. Using the concept of biorefinery, L ‐arginine could become widely available from biomass waste streams via the nitrogen storage polypeptide cyanophycin. Selective hydrolysis of L ‐arginine to L ‐ornithine is difficult to perform chemically, therefore the stabilization and immobilization of Bacillus subtilis arginase (EC 3.5.3.1) was studied in a continuously stirred membrane reactor system. Initial pH of the substrate solution, addition of L ‐aspartic acid and reducing agents all appeared to have an effect on the operational stability of B. subtilis arginase. A remarkably good operational stability (total turnover number, TTN=1.13⋅10⁸) at the pH of arginine free base (pH 11.0) was observed, which was further improved with the addition of sodium dithionite to the substrate solution (TTN>1⋅10⁹). B. subtilis arginase was successfully immobilized on three commercially available epoxy‐activated supports. Immobilization on Sepabeads EC‐EP was most promising, resulting in a recovered activity of 75% and enhanced thermostability. In conclusion, the stabilization and immobilization of B. subtilis arginase has opened up possibilities for its application in the biobased production of nitrogen‐containing chemicals as an alternative to the petrochemical production.     

Pilot Studies of Ozonation for Inactivation of Artemia salina Nauplii in Ballast Water

A pilot-plant study was conducted in the Republic of Croatia to determine the applicability of ozonation for inactivation of non-indigenous species and to provide necessary information regarding use of ozone as a ballast water treatment option. Nauplii of the brine shrimp Artemia salina were used as model organisms to investigate the efficacy of ozonation at three different ozone dosages (2.4, 3.7 and 10.9 mg L^?1). Mortality of Artemia nauplii at 98.6%, was achieved after 3 h of exposure in ozone-treated water with the highest ozone dosage. Our results indicated that ozonation is a promising treatment for controlling non-indigenous and potentially invasive species; however, to draw more general conclusions, several species with higher level of resistance to ozone are required and will be studied in the future.     

Electrochemical disinfection of simulated ballast water using Artemia salina as indicator

This work examined the potential of electrochemical disinfection to treat simulated ballast water with Artemia salina (A. salina) as an indicator organism. The effect of contact time (residence time in the electrolytic cell) and current density were investigated. Furthermore, the formation of disinfection by-products (trihalomethanes) was also examined. Under conditions of single pass through the electrolytic cell, a current density of 135 mA/cm² and a residence time of around 1 min were required for 100% mortality of A. salina. Dissolved organic carbon due to cell lysis increased by 1–2 mg/L, while the formation of chlorination by-products, expressed as trihalomethanes was very small (less than 10 μg/L at 135 mA/cm²).     

Conditions Affecting Bromate Formation During Ozonation of Bottled Water

Bromate concentration, ozone lifetime and ozone exposure (CT value) measured in bottled water in full-scale runs, were in good agreement to those measured in laboratory experiments. Ozone lifetime in bottled water was high enough to result in a CT value greater than 5 even for ozone dose as low as 0.1?mgO₃/L, at a water pH of 7.6. Bromate was gradually formed during the ozone lifetime. Bormate formation and ozone exposure were significantly influenced by pH. In full-scale runs, an ozone dose of 0.15?mgO₃/L at pH=7.6 resulted in a CT of 10.3 and a bromate concentration of 13.5?µg/L, while at pH=7.25 the values of CT and BrO₃ ^? were 12.6 and 9.6?µg/L, respectively. By decreasing further the pH to 6.8, an increase of CT value to 15.8 and a reduction of bromate to 5.5?µg BrO₃ ^?/L were observed. In addition, results in full-scale runs showed that ozone exposure and bromate concentrations were linearly related to ozone dose in the working range of 0.1 to 0.25?mgO₃/L.     

Effects of Ozone Treatment on Microbiological Quality and Physicochemical Properties of Turkey Breast Meat

ABSTRACT

The effects of ozone treatment (1 × 10^?2 kg m^?3, for up to 8 h) on quality parameters of turkey meat were investigated. Ozone was effective in inactivating microorganisms. Approximately 2.9, 2.3 and 1.9 log reductions were achieved in the counts of total aerobic mesophilic bacteria, Enterobacteriaceae and yeast-mold, respectively. Ozone caused significant changes in carbonyl contents, thiobarbituric acid reactive substances, color and pH values of the samples. Water holding capacity and cooking yield of treated samples increased significantly (p < .05). This is the first report demonstrating that quality parameters of turkey breast meat are markedly affected by ozone treatment.     

Oxidation of Nitrites in Mine Waters

A major component in the disinfection cost of mine water is the oxidation of microbiologically formed nitrite ion, which can be effectively oxidized by ozone (at close to the stoichiometric ratio of 3.4 mg O₃ per mg nitrite–snitrogen. The injudicious use of oxidizing disinfectants in the mine water may be implicated n i nitrite ion buildup. Laboratory batch reactor experiments show that 3 to 12 mg Cl₂/L and 3 to 11 mg CIO₂/L can inhibit nitrite ion oxidation by Nitrobacter. This inhibitive effect has not been observed for ozone.     

Osmotic Dehydration Kinetics of Pumpkin Fruits Using Ternary Solutions of Sodium Chloride and Sucrose

The objective of this work was to obtain experimental data and modeling of osmotic dehydration kinetics of pumpkin fruits (Cucurbita pepo L.) with aqueous NaCl/sucrose solutions. For this purpose, effective diffusion coefficients for water, sucrose, and NaCl were calculated by means of a simple model based on Fick's second law. Water loss achieved 80%, sucrose 13%, and NaCl 6% of the initial sample weight. Effective diffusion coefficients ranged from 0.58–1.40 × 10^?9 m²/s, 0.75–1.23 × 10^?9 m²/s, and 2.60–4.11 × 10^?9 m²/s for water, sucrose, and NaCl, respectively. The proposed model gave a good correlation of the experimental data. The quality of the operation was evaluated by analysis of the values of WL/SG ratio.     

Study Of The Advanced Oxidation Processes Of Chlorobenzenes In Water

The focus of this study was to investigate the use of advanced oxidation processes to oxidize a residual water in which chlorobenzenes were found in the range of 1 mg/L to 10 mg/L and whose TOC was about 1,000 mg/L, and a solution of chlorobenzenes whose concentration was 0.03 mg/L, which was prepared from stock solutions. Ozone in basic medium (pH = 9) and ozone in the presence of hydrogen peroxide (H₂O₂) were compared.     

Hydroxyl Radical/Ozone Ratios During Ozonation Processes. II. The Effect of Temperature,pH, Alkalinity,and DOM Properties

The influence of temperature, pH, alkalinity, and type and concentration of the dissolved organic matter (DOM) on the rate of ozone (O₃) decomposition, O₃-exposure, ?OH-exposure and the ratio R_ct of the concentrations of ?OH and O₃ has been studied. For a standardized single ozone dose of 1 mg/L in all experiments, considerable variations in O₃-exposure and ?OH-exposure were found. This has important implications for water treatment plants regarding the efficiency of oxidation and disinfection by O₃. In oligotrophic surface waters and groundwaters, minimal calibration experiments are needed to model and control the ozonation process, whereas in eutrophic surface waters more frequent measurements of O₃ kinetics and R_ct values are required to evaluate seasonal variations.     

Ozone Disinfection Efficiency for Indicator Microorganisms at Different pH Values and Temperatures

Disinfection efficiency of ozone was determined in various types of water at different pH (6, 7 and 8) values and temperatures (15, 25 and 35 ^°C) for E. coli and Salmonella. Three different applied ozone concentrations (1.5, 1.7, and 2 mg/L) in the gas phase were applied, and samples were taken at different time intervals to determine microbial survival using spread plate count (SPC) and ozone residual. Highest microbial inactivation was observed in distilled water with applied ozone concentration of 2 mg/L in the gas phase. Survival of E. coli was higher at pH 8 and 15 ^°C as compared to lower pH values and temperatures as depicted by the inactivation kinetics of the test microbes used in the study. Salmonella showed 5 and 6 log removal after contact time of 45 and 60 sec, respectively, at 2 mg/L. Disinfection of mixed culture showed relatively more survival of E. coli; as 3 and 4 log removal of E. coli and 4 and 5 log removal of Salmonella was observed after 45 and 60 sec.     

Ozone Applications in the Post-Harvest of Papaya (Carica papaya L.): An Alternative to Amistar Fungicide

The objective of this article was to evaluate ozone applications in the post-harvest of papaya (Carica papaya L) as an alternative to Amistar fungicide, taking into account the effect on the control of fungal pathogens growth, shelf-life, seed germination percentage and soluble solids content. Ozone doses were applied in vitro to strains of seven fungi species, which cause rot of papaya. Papayas cv. Maradol-red were harvested and treated with gaseous ozone (500 mg m^?3), ozone-containing water (1 mg L^?1) and a solution of Amistar fungicide (0.1 ml L^?1). They were stored for 10 days. Washing with ozone-containing water was found to be the most favorable alternative. The ozone use showed a delay in fruit ripening. The effect on seed germination percentage and soluble solids content was not significant. A methodology for ozone use in the post-harvest phase was proposed.