Inactivation of Chironomid Larvae with Chlorine Dioxide and Chlorine

Chironomid larvae propagate prolifically in eutrophic water body and they cannot be exterminated by conventional disinfection process. The inactivation effects of chlorine and chlorine dioxide on Chironomid larvae were investigated and some bourdary values in practice were determined under .conditions of various oxidaat dosage, organic precursor concentmtion and pH value. In addition, removal effect of different pre-oxidation cambined with coagulation process on Chironomid larvae in raw water was evaluated. It was found that chlorine dioxide possessed better inactivation effect than chlorine. Complete inactivation of Chironomid larvae in raw water was resulted by 1.5 mg/L of chlorine dioxide with 30 min of contact ＇time. Additionally, the organic precursor concentration, pH value had little influence on the inactivation effect. The coagulation jar test showed that Chironomid larvae in the raw water could be completely removed by chlorine dioxide pre-oxidation in combination with the coagulation process at chlorine dioxide dosage of 0.8 mg/L.

Full-scale study of removal effect on Cyclops of zooplankton with chlorine dioxide

Cyclops of zooplankton propagated excessively in eutrophic water body and could not be effectively inactivated by the conventional disinfections process like chlorination due to its stronger resistance to oxidation. In this paper, a full-scale study of chlorine dioxide preoxidation cooperating with routine clarification process for Cyclops removal was conducted in a waterworks. The experimental results were compared with that of the existing prechlorination process in several aspects: including the Cyclops removal efficiencies of water samples taken from the outlets of sedimentation tank and sand filter and the security of drinking water and so on. The results showed that chlorine dioxide might be more effective to inactivate Cyclops than chlorine and Cyclops could be thoroughly removed from water by pre-dosing chlorine dioxide process. The GC-MS examination and Ames test further showed that the sort and amount of organic substance in the treated water by chlorine dioxide preoxidation were evidently less than that of prechlorination and the mutagenicity of drinking water treated by pre-dosing chlorine dioxide was substantially reduced compared with prechlorination.

Effects of Chlorine Dioxide Gas on Postharvest Physiology and Storage Quality of Green Bell Pepper (Capsicum frutescens L.var.Longrum)

The effects of treatment of chlorine dioxide （C1Oz） gas on postharvest physiology and preservation quality of green bell peppers were studied. Green bell peppers were collected in bags and treated with 0, 5, 10, 20, and 50 mg L^-1 ClO2 gas at 10±0.5℃ for over 40 d, and the changes in postharvest physiology and preservation quality of the peppers were evaluated during the storage. The inhibition of rot of the peppers was observed for all the tested ClO2 gas treatments. The rot rates of the treated samples were 50% lesser than those of the control after day 40 of storage. The highest inhibitory effect was obtained after 50 mg L^-1 ClO2 gas treatment, where the peppers did not decay until day 30 and showed only one-fourth of the rot rate of the control at day 40 of storage. The respiratory activity of the peppers was significantly （P〈0.05） inhibited by 20 and 50 mg L^-1 ClO2 treatments, whereas no significant effects on respiratory activity were observed with 5 and 10 mg L^-1 ClO2 treatments （P〉0.05）. Except for 50 mg L^-1 ClO2, malondialdenyde （MDA） contents in the peppers treated with 5, 10, or 20 mg L^-1 ClO2 were not significantly （P〉0.05） different from those in the control. Degradation of chlorophyll in the peppers was delayed by 5 mg L-1ClO2, but promoted by 10, 20, or 50 mg L^-1 ClO2. The vitamin C content, titratable acidity, and total soluble solids of the peppers treated by all the tested ClO2 gas did not significantly change during the storage. The results suggested that ClO2 gas treatment effectively delayed the postharvest physiological transformation of green peppers, inhibited decay and respiration, maintained some nutritional and sensory quality, and retarded MDA accumulation.

Preparation and Evaluation of Novel Solid Chlorine Dioxide-based Disinfectant Powder in Single-pack

Objective To prepare and evaluate novel chlorine dioxide-based disinfectant powder in single-pack that is more convenient for use and transportation. Methods Orthogonal experiment was performed to determine the recipe of the disinfectant powder. Stability test, suspension quantitative bactericidal test, simulation field triM, and animal toxicity test were carded out to observe its bactericidal and toxicological effects. Results The orthogonal experiment showed that the type of water solution had no effect on the disinfectant powder and the best ratio of sodium chlorite to solid acid was 1：3. Ten grams of the disinfectant powder was fully dissolved in 20 mL water for 2 min, and diluted to 500 mL in water. After 5-10 min, the concentration of chlorine dioxide （CIO2） solution was 266 mg/L to 276 mg/L. After stored at 54℃ for 14 d, the average concentration of CIO2 was decreased by 5.03%. Suspension quantitative bactericidal test showed that the average killing logarithm （KL） value for both Staphylococcus aureus and Escherichia coli in 100 mg/L CIO2 solution for 2 min was over 5.00. In simulation field triM, the average descending KL value for Escherichia coli in the solution containing 100 mg/L CIO2 for 5 min was over 3.00. The mouse acute LD50 in the solution 5 times exceeded 5000 mg/kg. The disinfectant powder was not toxic and irritative to rabbit skin and had no mutagenic effect on mouse marrow polychromatic erythrocytes （PCE）. Conclusion The stability and bactericidal efficacy of solid chlorine dioxide-based disinfectant powder in single-pack are good. The solution containing 100 mg/L CIO2 can kill vegetative forms of bacteria. The concentration of CIO2 on the disinfecting surface of objects is 100 mg/L. The disinfectant powder is not toxic and irritative.

Kinetics of aniline oxidation with chlorine dioxide

For the first time, kinetics of aniline oxidation with chlorine dioxide(ClO 2) were investigated systematically by detecting concentration of aniline with HPLC at regular intervals. Results showed that the reaction was first-order both in ClO 2 and in aniline, and the oxidation reaction could be described as second-order reaction. Stoichiometric factor η was experimentally determined to be 2 44. The second-order-reaction rate constant k was 0 11 L/(mol·s) under condition of pH 6 86 and water temperature(T w) 287K. Reaction activation energy was 72 31 kJ/mol, indicating that the reaction could take place under usual water treatment conditions. The reaction rate constants in acidic and alkali media were greater than that in neutral medium. Chlorite ion could slightly increase reaction rate in acidic medium. p-aminophenol and azobenzene were detected by GC-MS as intermediates.

Removal effect on Mesocyclops leukarti and mutagenicity with chlorine dioxide

Mesocyclops leukarti of zooplankton propagates excessively in eutrophic water body and it cannot be effectively inactivated by the conventional drinking water treatment process. In order to tackle this problem, a study of removal effect on Mesocylops leukarti with chlorine dioxide in a waterworks was performed. The results showed that Mesocyclops leukarti could be effectively removed from water by 1.0 mg/L chlorine dioxide prcoxidation combined with the conventional drinking water treatment process. Higher oxidizability and molecular state of chlorine dioxide in water is the key to the inactivation of Mesocyclops leukarti. The chlorite, disinfection by-products （DBPs） of chlorine dioxide, was stable at 0.45 mg/L, which is lower than that critical value of the USEPA. GC-MS examination showed that the quantity of organic substance in the water treated by chlorine dioxide obviously decreased. Ames test further revealed that the mutagenicity was reduced by chlorine dioxide with respect to prechlorine. The propagation ofMesocyclops leukorti can be inactivated effectively and safely by chlorine dioxide pre-oxidation.

Pilot-scale study of removal effect on Chironomid larvae with chlorine dioxide

Chironomid larvae propagated excessively in eutrophic water body and could not be effectively inactivated by the conventional disinfection process like chlorination due to its stronger resistance to oxidation. In this paper, a pilot-scale study of chlorine dioxide preoxidation cooperating with routine clarification process for Chironomid larvae removal was conducted in Shenzhen Waterworks in Guangdong Province, China. The experimental results were compared with that of the existing prechlorination process in several aspects, including the Chironomid larvae removal efficiencies of water samples taken from the outlets of sedimentation tank, sand filter, the security of drinking water and so on. The results showed that chlorine dioxide might be more effective to inactivate Chironomid larvae than chlorine and Chironomid larvae could be thoroughly removed from water by pre-dosing chlorine dioxide process. The GC-MS examination and Ames test further showed that the sort and amount of organic substance in the treated water by chlorine dioxide preoxidation were evidently less than that ofprechlorination and the mutagenicity of drinking water treated by pre-dosing chlorine dioxide was substantially reduced compared with prechlorination.

Inactivation of Resistant Mycobacteria mucogenicum in Water:Chlorine Resistance and Mechanism Analysis

Objective To better understand the mechanism of chlorine resistance of mycobacteria and evaluate the efficiency of various disinfection processes.Methods Inactivation experiments of one strain Mycobacteria mucogenicum,isolated from a drinking water distribution system in South China were conducted with various chlorine disinfectants.Inactivation efficiency and disinfectant residual,as well as the formation of organic chloramines,were measured during the experiments.Results This strain of M.mucogenicum showed high resistance to chlorine.The CT values of 99.9% inactivation by free chlorine,monochloramine and chlorine dioxide were detected as 29.6±1.46,170±6.16,and 10.9±1.55 min（mg/L） respectively,indicating that chlorine dioxide exhibited significantly higher efficiency than free chlorine and monochloramine.It was also found that M.mucogenicum reacted with chlorine disinfectants more slowly than S.aureus,but consumed more chlorine disinfectants during longer time of contact.Lipid analysis of the cell construction revealed that 95.7% of cell membrane lipid of M.mucogenicum was composed of saturated long chain fatty acids.Saturated fatty acids were regarded as more stable and more hydrophilic which enabled the cell membrane to prevent the diffusion of chlorine.Conclusion It was concluded that different compositions of cell membrane might endow M.mucogenicum with a higher chlorine resistance.

Research on the explosion characteristics of chlorine dioxide gas

The explosion characteristics of chlorine dioxide gas have been studied for the first time in a cylindrical exploder with a shell capacity of 201. The experimental results have indicated that the lower concentration limit for the explosive decomposition of chlorine dioxide gas is 9.5% （[ClO2]/[air]）, whereas there is no corresponding upper concentration limit. The maximum pressure of explosion relative to the initial pressure was measured as 0.024 MPa at 10% ClO2 and 0.641 MPa at 90% ClO2. The induction time （the time from the moment of sparking to explosion） at 10% ClO2 was 2195 ms, but at 90% ClO2 the induction time was just 8 ms. The explosion reaction mechanism of ClO2 is of a degenerate chain-branching type involving the formation of a stable intermediate （Cl2O3）, from which the chain branching occurs.

Process Development and Design of Chlorine Dioxide Production Based on Hydrogen Peroxide

This paper presents a process development and design of chlorine dioxide production based on hydrogen peroxide. The process is characterized by cleaner production, high efficiency, and waste minimization. Optimization of process conditions, selection of equipment, and experiment of recycle of waste acid are carried out. The process design is realized in consideration of several aspects such as operation, material, equipment design and safety. An industrialized process flowsheet is developed according to experiment. A pilot testing is carried out to confirm the lab results. Process design of chlorine dioxide production based on hydrogen peroxide is realized.

Ordinary Toxicity of Chlorine Dioxide and By-products Chlorite and Chlorate in Water

Acute toxicity and accumulated toxicity of chlorine dioxide (ClO2) and by-products chlorite (ClO2-) and chlorate (ClO3-) in water acted on mice are studied by the method of Horn and accumulation coefficient. Subchronic toxicity of the mixture of ClO2 and ClO2-and ClO3- in water acted on rat is studied though feeding test for 90 days, including statistical analysis of variance on weight gaining, food utilization efficiency,index of blood and serum,liver (or kidney) to body weight ratio, and histopathological examination on liver and kidney. The results show that aqueous solution of ClO2, NaClO2 and NaClO3 ( with the concentration of 276.5 mg/L, 200 mg/L and 200 mg/L respectively) and the mixed aqueous solution of ClO2 with the concentration of 553 mg/L are actually non-poisonous , and non-cumulative aqueous solution as well.

Study on metal corrosion caused by chlorine dioxide of various purities

Weight lost method was used to comparatively study the corrosion behavior of four different metals under the dosage of chlorine dioxide, chlorine and their mixture respectively. The experimental results indicated that chlorine causes the most serious corrosion of carbon steel, and the higher the concentration of chlorine, the more serious the corrosion. On the contrary, metals corrosion is the least serious in the case of chlorine dioxide. The results further revealed that chlorine dioxide is the most effective water treatment reagent, making it the best choice to use extensively in circulated cooling water disinfection and corrosion control.

Reversed flow injection spectrophotometric determination of low residuals of chlorine dioxide in water using chlorophenol red

A novel, simple, rapid, sensitive and highly selective flow injection procedure for the spectrophotometric determination of chlorine dioxide in the presence of other chlorine species, viz,free chlorine, chlorite, chlorate and hypochlorite, is developed. The method is based on the discoloration reaction between chlorine dioxide and chlorophenol red and can overcome the shortcomings existed in direct spectrophotometric determination for chlorine dioxide owing to the serious interference of free and combined chlorine. The procedure gave a linear calibration graph over the range 0—0.71 mg/L of chlorine dioxide. With a detection limit of 0.024 mg/L and a sample throughput of 60 samples/h.

Effects of Stable Chlorine Dioxide on Sterilization and Preservation of Fresh-cut Narrow-leaf Cattail

At present, chlorine dioxide has been widely used as a bactericide that may become an alternative to chlorine. In this study, fresh-cut narrow-leaf cattail was soaked with 45, 70 and 95 mg/L chlorine dioxide solution, respectively. Fresh-cut narrow-leaf cattail samples were collected regularly to determine changes in surface microbe amount, cellulose content, Vc content, reduction sugar content and sensory quality of narrow-leaf cattail, thus analyzing the effects of chlorine diox- ide on sterilization and preservation of fresh-cut narrow-leaf cattail. The results showed that all three concentrations of chlorine dioxide solution could significantly reduce the amount of microbes on the surface of fresh-cut narrow-leaf cattail and improve the edible safety of products. The initial sterilization efficiency was im- proved gradually as the concentration of chlorine dioxide increased. In addition, chlorine dioxide treatment postponed the increase of cellulose content of fresh-cut narrow-leaf cattail. However, chlorine dioxide oxidized Vc and reducing sugar, and its bleaching effect also exerted a certain impact on the sensory quality of fresh- cut narrow-leaf cattail. Based on comprehensive comparisons, 45 - 70 mg/L chlorine dioxide solution exerted the best effects on sterilization and preservation of fresh-cut narrow-leaf cattail. This study laid the foundation for the production and application of chlorine dioxide solution and promotion of rapid development of nar- row-leaf cattail industry.

Effect of Inhabitation Mouthwash Solution Containing Chlorine Dioxide (Pro Fresh^®) on Oral Malodor

Recently, the interest in oral malodor has been grown and the number of people having trouble with oral malodor is increasing year by year. Generally, as the branch of medicine which deals with patients complaining about oral malodor, dentistry is mostly chosen. On the current situation, however, the dental office side typically finds it difficult to deal with several kinds of oral malodor which show no improvement even though cavities or periodontal disease is completely cured. Main components to cause oral malodor are volatile sulfur compounds (methyl mercaptan, dimethyl sulfide, hydrogen sulfide);in the present study, therefore, the effect of mouthwash solution containing chlorine dioxide to relieve oral malodor and increase saliva production was tested. The subjects were 92 patients (Control group: 2 males, 3 females, age;30.8 ± 4 years old, Mouthwash group: 28 males, 59 females, age: 36.9 ± 1.3 years old) who visited the hospital complaining about oral malodor. Intraoral gas, exhaled gas, the saliva production at rest, the ability for salivation and the buffering ability of saliva were examined twice, before the subjects used the mouthwash solution every day for one month. The simple chromatography oral chroma, which was insulated from the influence of temperature and humidity and also was able to measure with a high degree of accuracy, was used to measure odor as the device analysis method. The control group did not change in VSCs, saliva production and the buffering ability of saliva. After using mouthwash solution, the concentration of the 3 major components gas of intraoral gas and exhaled gas, i.e. methyl mercaptan, dimethyl sulfide, hydrogen sulfide, were all decreased. As for hydrogen sulfide, intraoral gas (from 225.8 ± 28.1 ppb to 41.1 ± 8.8 ppb) and exhaled gas (from 212.0 ± 50.4 ppb to 34.6 ± 16.6 ppb) was significantly decreased. Also, saliva production at rest (from 1.3 ± 0.1 ml to 1.7 ± 0.1 ml) and the ability to salivate (from 4.5 ± 0.3 ml to 5.1 ± 0.3 ml) were both significantly increased. As for the buffering ability of saliva, significant changes were not detected on the change of salivary pH after using mouthwash solution, and it did not have any effects on the buffering ability of saliva. In conclusion, these results suggest that the mouthwash solution containing chlorine dioxide has significant effects on inhibiting malodor.

Virucidal Activity of Chlorine Dioxide Gas for Reduction of Coronavirus on Surfaces and PPE

A coronavirus (SARS-CoV-2) has caused a global pandemic and associated morbidity and mortality resultant from COVID-19. As a result of efforts to control direct (person to person) and indirect (contaminated objects, surfaces, indoor air) transmission of the virus, various interventions have been evaluated. Studies were conducted to evaluate the efficacy of commercially available chlorine dioxide (CD) products to reduce viral loads on PPE (face masks) and surfaces using a novel dry gas release intervention. The efficacy of CD slow release 30-day sachets was tested on N95 face masks inoculated with human coronavirus OC43 in suspension. One sachet was placed with an inoculated mask in plastic resealable bags. Three trials were completed using the original sachet where a mask and sachet were placed into a plastic bag for 13 hours per sachet age of 1 day, 14 days, and 30 days. The amount of CD generated during a 13-hour treatment period was 0.30 mg. The nominal concentration of CD was estimated to be 317 mg/m3. All three tests demonstrated at least a 99.91% reduction of viral loading in the mask versus a non-treated control. Efficacy of CD dry gas fast releasing pods (Ultrashok) for fumigation was also tested in a 1344 ft3 closed room. Two pods were placed in the space and CD surface virucidal efficacy was tested in three locations of the room after 1 hour and 2 hours of dwell time. The estimated nominal peak concentration was 15 ppmv in the room. The one-hour exposure saw a >99.91% OC43 reduction on surfaces and the two-hour exposure resulted in a >99.997% OC43 reduction on surfaces versus a non-treated control. These results indicate dry CD is highly effective against human coronavirus. CD was 99.91% effective for eliminating human coronavirus OC43 in both sachet and capsule fumigant form using both fast and slow release mechanisms. Rapid fumigant application is suitable for contaminated rooms, ambulances, emergency vehicles, and many types of PPE, most particularly porous PPE materials. The gaseous state of CD allows for rapid diffusion and transfer of the virucidal stable free radical to all surfaces of PPE and indoor areas that would favor virus survival. Additionally, this work suggests CD can be effective at levels with significant margins of safety (little to no exposure and rapid degradation of residuals) providing minimal public health risks associated with the use of CD.

Control effects of pε and pH on the generation and stability of chlorine dioxide

A new method, without assistance of activity ratio diagram, was applied to construct the p ε \|pH diagrams for chlorine system. The optimal pH range for generation of ClO_(2) by contacting Cl 2(g) directly with ClO^(-) _(2) solution is within pH 1.35-1.94, particularly within pH 1 35-4 00 only if minimizing the formation of Cl_(2) It is unachievable to synthesize pure ClO_(2) from the reaction of Cl_(2) and ClO^(-)_(2). Conversely, ClO_(2) may be present a variation of stability in different waters owing to the changed p ε and pH. ClO_(2) could be relatively stable if not disproportionate into ClO^(-)_(3), coexisting with ClO^(-) _(2) (p ε 17 63 and pH>9 68), Cl_(2) (pH≤0.92) or Cl^(-)(pH 0.92-9.68). When chlorine system has already reached the ultimate equilibria, ClO_(2) is a stable species in strongly acid media. As the acidity decreases, ClO 2 disproportionates into ClO^(-)_(3) and Cl_(2) Aqueous ClO_(2) is unstable within the normal pH range. This work initially, theoretically elucidates the generation and stability of ClO_(2) by way of the p ε pH diagrams.

Removal of benzene homologous compounds with chlorine dioxide

Chlorine dioxide composite disinfectant generator that produces a mixture of the oxidant gases comprising chlorine dioxide, chlorine, ozone and hydrogen peroxide through electrolyzing salt,is widely utilized in China presently.The experiments in the paper focused on the removal of benzene homologous compounds such as styrene, methyl and dimethyl benzene. The results indicated that pH value was the most crucial factor to influence the treatment effects while reaction time and input way were considered as the importance. The removal rate for benzene could reach 60% when above 80% for methyl, and 100% for styrene and dimethyl. The variation mechanisms between chlorine dioxide,chlorite and chloride which determine the drinking water quality also discussed.

Comparison of Anolyte and Chlorine Dioxide for a Continuous Hot Water Disinfection in Nursing Home: A Two Years Legionnaires’ Disease Prevention

Worldwide epidemiological reports assert that drinking water is a source for infections and Legionella control represents a critical issue in healthcare settings. Chemical disinfections of water networks are control measures that need to be fine-tuned to obtain satisfactory results in large buildings over prolonged time periods. Aim of study is the evaluation of the effect of anolyte and chlorine dioxide, applied in two different hot water networks of a nursing home to manage Legionella risk. Nursing home has two buildings (A and B), with the same point of aqueduct water entrance. From June 2016, following a shock chlorination, the continuous disinfections with chlorine dioxide and anolyte were applied in hot networks of building A and B, respectively. Hot water was sampled at the central heating system and at two points of use for Legionella research, while chemical tests of manganese (Mn), iron (Fe), zinc (Zn) and trihalomethanes compounds (THM) were implemented to evaluate the disinfection by-products presence. Before chlorination Legionella pneumophila sg1 was recovered with a mean count of 2.4 × 104 CFU/L, while chemical compounds concentrations were within the law limits (Directive 98/83/EC). Then the disinfections Legionella was not recovered in both hot water plants. After the disinfection with chlorine dioxide (from June 2016 to May 2018), a statistically significant increase of iron, zinc and THM concentrations was detected in building A (p = 0.012;p = 0.004;p = 0.008). Both disinfectants appear effective against Legionella spp. growth in water network, but anolyte ensures a lower disinfection by-products release.

Bench and Full Scale Study of Removal Effect and Mutagenicity on Mesocyclops Leukarti with Chlorine Dioxide

Mesocyclops Leukarti of zooplankton propagates excessively in eutrophic water body and it can not be effectively inactivated by the conventional process in drinking waterworks for its special surface structure. In this paper, a study of removal efficiency on Mesocyclops Leukarti with chlorine dioxide in a drinking waterworks was performed. Bench scale results showed that chlorine dioxide is more effective against Mesocyclops Leukarti. And Mesocyclops Leukarti could be effectively removed from water by 1.0 mg/L chlorine dioxide preoxidation cooperated with the conventional process during the full scale study. The chlorite, by.product of prechiorine dioxide, was constant at 0.45 mg/L after filtration, which was lower than the critical value of the USEPA. GC-MS examination and Ames test showed that the quantity of organics and the mutngenicity in the water treated by chlorine dioxide is obviously less than that of prechlorination.