Analysis of Damage on the Streptococcus mutans Immersed in Ozonated Water: Preliminary Study for Application as Mouth Rinse

Ozonated water has been demonstrated to induce significant results in terms of the elimination of microorganisms. The present study assessed the damage to Streptococcus mutans after exposure to ozonated water; the ozone generator was adjusted to provide an outlet concentration of 60 mg/L, the samples were submitted to different ozonation times 1, 2, 4, 6, and 10 mi. Scanning electron microscopy and atomic force images were obtained to identify damage to the bacteria, followed by reactive oxygen species (ROS) evaluation and microbial viability. The results showed a significant reduction in viability and the images evidenced the generation of gaps on the microbial wall and surface layer alterations. Ozone can induce significant damage to S. mutans, thus suggesting that the use of ozonated water to prevent carious lesion formation is extremely promising.     

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.     

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.     

Antimicrobial Activity of Ozone against Pathogenic Oral Microorganisms on Different Denture Base Resins

ABSTRACT

The present study aimed to evaluate the antimicrobial effect of gaseous ozone against specific oral pathogens on denture base resins. 1080 round samples were prepared (10mm-diameter, 2mm-thickness). Candida albicans, Streptococcus mutans, Streptococcus gordonii, and Aggregatibacter actinomycetemcomitans, polyamide-Deflex, heat-cured polymethyl-methacrylate (PMMA)-QC-20, and cold-cured-PMMA-Meliodent. The doses and durations: 25, 50 and 100µg/ml, 5, 10, 20, 30 minutes. For Cell viability (CV) MTT was used. 100µg/ml was most effective dose for C. albicans, S .gordonii, and A. actinomycetemcomitans were in heat-cured-PMMA and polyamide for S.mutans. For polyamide, lowest CV was 43% in S.mutans and A.actinomycetemcomitans. CV of heat-cure and cold-cure PMMA were 31% and 32% in S.gordonii, respectively. CV was similar for all resins and durations in S.mutans and A.actinomycetemcomitans and for polyamide for C.albicans and for heat-cure PMMA for S.gordonii. 30-min ozone application killed 80% of all microorganisms in all resins except for C.albicans in polyamide (65% cell death) and cold-cure PMMA (57% cell death). Optimal dose/duration combination was 100 µg/ml-10 min. Gaseous ozone can be considered as an effective cleansing agent for denture base resins.     

Research on the Feasibility of Spraying Micro/Nano Bubble Ozonated Water for Airborne Disease Prevention

This research combined micro/nano bubble techniques with ozone disinfection to determine feasibility of applying micro/nano bubble ozonated water in preventing tomato airborne disease. Results indicated that dissolving ozone in micro/nano bubbles is more efficient than using a mixing pump. In our in vitro studies, when dissolved ozone concentration was 1.6 mg/L, a 5.2 to 3.3 log reduction in Alternaria solani Sorauer conidia was observed; with concentration of 1.8 mg/L, there was a 5.0 to 3.7 log reduction in Cladosporium fulvum conidia. Furthermore, spraying ozonated water in a certain concentration range (0.6–1.8 mg/L) had no significant negative effects on tomato growth.     

Industrial-scale Malting Barley (Hordeum vulgare L.) Seed Disinfection by Fog of Ozonated Water Application

The aim of this study was to underscore that seed treatment by the fog of ozonated water constitutes a promising alternative tool, in terms of health and environmental gains, regarding traditional ozone treatment. In order to obtain a clear vision of this performance, the technology was implemented on an industrial scale (malting industry). Under an exposition of barley seeds to 9.8 ppm of dissolved ozone into water, our results showed a significant disinfection effect of 80% for Fusarium sp. and 70% for Aspergillus sp., but no effect was established on Alternaria sp.     

Evaluation of the effects of different remineralizing agents on Streptococcus mutans biofilm adhesion

The aim of the study was to compare the effects of different remineralization methods that are well established in clinical and daily use on S. mutans biofilm adhesion. In this study 72 human third molars were used. From each tooth two pieces of 4?mm x 7?mm enamel blocks were acquired. The samples were divided into 6 groups in which include 10 samples per time period (24h and 48?h) and for each remineralization method; control, flouride, ozone, CPP-ACP, arginine, novamin. After remineralization procedures, enamel surfaces were covered with saliva. 10⁵ CFU/mL of active S. mutans culture were inoculated onto the samples. S. mutans colonies were counted with Plate Count Agar (PCA) decimal dilution method. Micromorphologic effects of different remineralization methods were observed by Scanning Electron Microscopy (SEM). The most S. mutans biofilm formation for both time periods was observed in the control group whereas the less biofilm adhesion was showed in the arginine group. There were no statistically significant differences among remineralization agents (p?>?0.05). In the control group there was statistical difference between 24?h and 48?h (p?<?0.005) but in the other study groups there were no significant difference between the time periods (p?>?0.05). Remineralization agents did not significant differ on S. mutans biofilm adhesion.     

Ozone is the most effective disinfectant for dental treatment units: Results after 8 years of comparison

The method of disinfecting water in dental treatment units using ozone‐containing water was first described 10 years ago. In an investigational period over the last 8 years, waters from the outlets of 14 treatment units were examined microbiologically in a total of 240 tests. Twelve of the treatment units, employing hydrogen peroxide/silver ion disinfection ‐ after repeated sanitization ‐ regularly exceeded the limits laid down in the regulations governing water purity, and Pseudomonas aeruginosa could be detected at 181 water outlets. However, germs could hardly be detected in any of the tests of waters sampled from the two treatment units using ozonated water disinfection.     

Inactivation of Giardia muris Using Ozone and Ozone-Hydrogen Peroxide

The disinfection effects of the ozone molecule alone and that of ozone decomposition products when inactivating Giardia muris cysts were investigated at bench-scale using two different ozone demand-free laboratory buffer systems. The first water was a 0.05 M phosphate buffer with hydrogen peroxide added at a 10:1 weight ratio. The second water was a 0.05 M phosphate – 0.01 M bicarbonate buffer which quickly scavenged radical species from ozone decomposition. The C3H/HeN mouse model was used to assess the infectivity of ozone treated cysts.

The phosphate-bicarbonate buffer system had significantly greater (P ≤ 0.05) inactivation of G. muris cysts than that observed in the phosphate buffer – peroxide system where ozone was completely decomposed in less than 120 s. Consequently, the design of ozone disinfection processes should maintain ozone residual for disinfection prior to the addition of hydrogen peroxide for the oxidation of other compounds.     

Optimization of Ozonation Process for Disinfection of Dental Unit Waterlines Using Response Surface Methodology

ABSTRACT

The reduction of microbial contamination in dental unit waterlines (DUWLs) appears to be necessary because of a potential risk of infections in immunocompromised patients and medical staff, which are regularly exposed to water and aerosols generated from DUWLs. In the present study, the qualitative and quantitative microbial contamination of water in DUWLs were determined and the conventional biomedical diagnostic tests were applied to identify microorganisms. A 3-level, 2-factor central composite design was utilized to investigate the effects of chief operating parameters and optimize ozone disinfection conditions. Also, the activity of three disinfectant (ozone, NaOCl, and peracetic acid) in microbial decontamination of DUWLs were compared. The results indicated that Microbacterium laevaniformans were the most prevalent genera (21%) among both Gram-negative and positive species in all samples. Regression analysis illustrated the good fit of the experimental data to the predicted model with R² and R²_adj correlation coefficients of 0.988 and 0.980, respectively. Moreover, under the optimal circumstances (Ozone concentration = 1.2 ppm and reaction time = 13.5 min) the disinfection efficiency was 97.52%. The results also revealed that ozone was effective disinfectant to reduce prevalent genera (with the removal of 93.75%, 92.57% and 96.15% of Pseudomonas aeruginosa, Microbacterium ?laevaniformans, and Alcaligenes faecalis, respectively) and already formed biofilms under optimum conditions. Based on achieved results, ozone was highly effective on microbial decontamination compared to peracetic acid and NaOCl disinfectant and can be used for disinfection of DUWLs.     

Studies on the Disinfection and Removal of Biofilms by Ozone Water Using an Artificial Microbial Biofilm System

Inactivation rates of the biofilms of P. fluorescence and P. aeruginosa established on a small slide glass in ozone water (0.9–3.2 mg/L, 1–20 min) were determined in a batch or flow-through system. The effects of ozone water on the biofilm matrices were defined clearly in situ by confocal laser scanning microscopy. These results indicate that ozone is an effective biocide against biofilms and it can remove exopolysaccharides in the biofilm matrices. However, the effective concentration of ozone for disinfection of biofilms varied with the biofilms formed, mainly due to reactions of ozone with constituents of the biofilms.     

Cryptosporidium Log-inactivation with Ozone Using Effluent CT10, Geometric Mean CT10, Extended Integrated CT10 and Extended CSTR Calculations

The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit.     

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.     

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.     

Water Disinfection of Dental Units using Ozone – Microbiological Results after 11 Years and Technical Problems

Water disinfection in dental treatment units using ozone and hydrogen peroxide/silver ion were compared for a period of 11 years. Water from nine treatment units was microbiologically examined in a total of 240 tests. Eight treatment units using peroxide disinfection regularly exceeded the limits stipulated by water purity regulations, and Pseudomonas aeruginosa was detected at 154 water outlets. However, hardly any of the water specimens taken from the treatment unit using ozonated water disinfection showed bacteria. Four technical problems to using ozonated water were found during this eleven year period. The use of hydrogen peroxide necessitated 48 basic disinfections.     

Advanced Treatment For Municipal Wastewater Reuse In Agriculture. III - Ozone Disinfection

Results of a pilot (100 m³/h) investigation on ozone disinfection of municipal tertiary effluents for reuse in agriculture carried out at West Bari (S. Italy) treatment plant are presented. Among dosages, contact times and advanced treatment schemes investigated it was demonstrated that ozone disinfection results in the achievement of the WHO microbial guideline (1,000 CFU/100ml for Fecal Coliforms) for unrestricted wastewater reuse in agriculture of both clarified and clarified-filtered municipal secondary effluents; it is very effective towards Pseudomonas aeruginosa, rather effective towards Giardia lamblia and substantially ineffective towards Cryptosporidium parvum and it forms limited amount of DBP (approx. 350 ppb of total aldehydes). O&M costs amount to 37 Euro/1000m³.     

Seawater Ozonation of Bacillus subtilis Spores: Implications for the Use of Ozone in Ballast Water Treatment

The potential of ozone for disinfection of ships’ ballast water was investigated using Bacillus subtilis spores as an indicator. The effects of pH, presence of iron, and bacterial strain on disinfection efficacy in seawater, under simulated ballast conditions, were investigated. Ozone dosages of 9 mg/L (pH 7) and 14 mg/L (pH 8.2) and 24 h contact achieved a 4-log inactivation with the various oxidant residuals formed. Iron surface at a ratio to water of 9 m²/m³ impaired the oxidant residuals and the disinfection of spores. Different strains of B. subtilis resulted in different CT values. Ozone does not seem to be a good choice for the control of spore-forming organisms in ballast water, but may be suitable for the control of other species.     

Superhydrophobic PDMS/SiNPs/T-ZnOw coating with reduced adhesion of Streptococcus mutans for dental caries prevention

The prevention of dental caries is based mainly on killing the cariogenic bacteria Streptococcus mutans. Prevention of S. mutans adhesion through the development of physical structures is rarely utilized. In this study, a superhydrophobic PDMS/SiNPs/T-ZnOw (PST) coating was prepared for use on a bovine tooth by mixing polydimethylsiloxane (PDMS), silicon dioxide nanoparticles (SiNPs), and tetrapod-like zinc oxide whiskers (T-ZnOw) using one-pot solution and spray methods. The results showed that the superhydrophobicity and roughness of the coating, affected by the PDMS content, were positively correlated with the anti-adhesive effect on S. mutans. The PST coating with PDMS, SiNPs, and T-ZnOw at a ratio of 2.5:1:1 exhibited the highest water contact angle (161°) and the best anti-adhesion effect (97.2% at 4 h and 98.1% at 12 h). The anti-adhesion property towards S. mutans was attributed to its needle-like structure, and the biofilm live-dead staining test showed that the coating had no bactericidal effect. In addition, the coating exhibited favorable durability and biocompatibility, providing a solid foundation for application in the human oral cavity. Thus, this study provides an effective method for caries prevention.     

Enhanced Bactericidal Effect of O3/H2O2 Followed by Cl2

With the appearance of chlorine resistant microorganisms such as Cryptosporidium parvum and Giardia lamblia in drinking water, significant attention has been drawn to the sequential application of multiple disinfectants including ozone, chlorine dioxide, and UV as a primary disinfectant. However, few studies have reported about the inactivation behavior of ozone-based AOP (advanced oxidation process) or its sequential application combined with other disinfectants. This is especially important since ozone itself experiences difficulty in the inactivation of these pathogens, especially at low temperatures: This study investigates the enhanced inactivation of Bacillus subtilis spores by the presence of an OH radical in the O₃/H₂O₂ system and the synergistically enhanced inactivation in the application of the O₃/H₂O₂ system followed by Cl₂. The results suggest that the O₃/H₂O₂ process can be considered as one of the viable alternatives when O₃ alone does not satisfy the disinfection requirement.     

Sequential disinfection of cryptosporidium parvum by ozone and chlorine dioxide

A two step disinfection approach was evaluated for control of Cryptosporidium parvum using bench‐scale experiments in 0.05 M phosphate buffer at pH 8 and 22 °C. Sequential application of ozone and chlorine dioxide was evaluated where ozone was applied first followed by chlorine dioxide. Infectivity in neonatal CD‐1 mice was used to assess oocyst viability after disinfection. The sequential treatment of oocysts by ozone followed by chlorine dioxide resulted in additional inactivation of C. parvum due to the synergism of the two disinfectants. The inactivation kinetics for chlorine dioxide were modeled following preconditioning with ozone at a given level using the Integral‐Hom model which takes the disinfectant decay into account. These preliminary findings indicate that sequential disinfection with ozone followed by chlorine dioxide may have potential in controlling waterborne parasites.