Which Uv Wavelength is the Most Effective for Chlorine-Resistant Bacteria in Terms of the Impact of Activity, Cell Membrane and DNA?
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Download This Paper Open PDF in Browser Add Paper to My Library Share: Permalink Using these links will ensure access to this page indefinitely Copy URL Copy DOIAims: Chlorine demand by Listeria monocytogenes cells and inactivation of L. monocytogenes by chlorine (0·6–1·0 mg l−1) at different temperatures (4, 20 and 30°C) have been investigated in a batch reactor. Methods and Results: Chlorine demand depended on the microbial concentration and was independent on the initial chlorine concentration and temperature. Chlorine decay was modelled by the addition of two first-order decay equations. Inactivation of L. monocytogenes by chlorine depended on the initial microbial concentration, initial chlorine concentration and temperature. A mathematical model based on a biphasic inactivation properly described survival curves of L. monocytogenes and a tertiary model was developed that satisfactorily predicted the inactivation of L. monocytogenes by different concentrations of initial chlorine at different temperatures. Conclusions: Both available chlorine decay and inactivation of L. monocytogenes by chlorine were biphasic and can be modelled by a two-term exponential model. Significance and Impact of the Study: The biphasic nature of survival curves of L. monocytogenes did not reflect the effect of a change of available chlorine concentration during the treatment. The microbial inactivation was caused by successive reactions that occur after the consumption of the chlorine by the bacterial cell components.
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Chlorination of wastewater is recently practiced in Korea. While many researchers have studied the kinetics of aqueous chlorine(HOCl) with nitrogeneous compounds and other organic/inorganic contaminants in drinking water, the researches of wastewater chlorination are relatively few. The purpose of this study was to investigate the chlorine decay kinetics and parameters on wastewater chlorination. Chlorine decay rate increased with increasing initial chlorine concentration. The parameters affecting chlorine decay rate were different in each wastewater treatment plant. One of the most important parameters affecting chlorine decay was initial chlorine concentration, and other parameters such as NH₃-N, total coliform, UV_(254) and Fe were also affected. The decay ratio of chlorine was decreased with increasing initial chlorine concentration, and the disinfection efficiency showed good correlation with the decay ratio.
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The chlorine loss of electrolyzed oxidizing (EO) water was examined during storage under different light, agitation, and packaging conditions. The chlorine loss of pH-adjusted EO water was also examined. Under open conditions, the chlorine loss through evaporation followed first-order kinetics. The rate of chlorine loss was increased about 5-fold with agitation, but it was not significantly affected by diffused light. Under closed conditions, the chlorine loss did not follow first-order kinetics, because the primary mechanism of chlorine loss may be self-decomposition of chlorine species rather than chlorine evaporation. The effect of diffused light was more significant compared to agitation after two months of storage under closed conditions. The chlorine loss of EO water and commercial chlorinated water decreased dramatically with the increase of pH from the acidic (pH 2.5) to the alkaline (pH 9.0) region.
Oxidizing agent
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Chlorine disinfection is a globally used method to ensure the safety of drinking water. However, it has not always been successful against viruses and, therefore, it is important to find new methods to disinfect water. Seventeen different coliphages were isolated from the treated municipal wastewater. These coliphages and MS2 were treated with different dosages of chlorine in drinking water, and a combined chlorine/ultraviolet irradiation treatment for the chlorine-resistant coliphages. Chlorine disinfection with 0.3-0.5 mg/L total chlorine (free Cl-dosage 0.12-0.21 mg/L) for 10 min achieved 2.5-5.7 Log10-reductions for 11 sensitive coliphages. The six most resistant coliphages showed no reduction with these chlorine concentrations. MS2 was intermediate in chlorine resistance, and thus it is not a good indicator for viruses in chlorine disinfection. In the combined treatment total chlorine of 0.05-0.25 mg/L (free Cl-dosage 0.02-0.08 mg/L) and ultraviolet irradiation (14-22 mWs/cm(2)) were more effective than chlorine alone, and 3-5 Log10-reductions were achieved for the chlorine-resistant strains. The chlorination efficiency could be increased by higher dosages and longer contact times, but this could increase the formation of disinfection by-products. Therefore, the combination treatment is a recommended disinfection method.
Dose
Ultraviolet
Portable water purification
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The inactivation effect of E.coli with different combination modes of UV and chlorine was compared.The result shows that the combination of UV and chlorine can improve the inactivation effect.However,different combination modes and different doses of UV and chlorine affect the inactivation effect.Simultaneous disinfection with UV and chlorine has lower effect than sequential disinfection.During disinfection with chlorine followed by UV,addition of high-concentration chlorine with short contact time has better disinfection efficiency.During disinfection with UV followed by chlorine,high chlorine dose has high inactivation rate.When the chlorine concentration is the same and the contact time is different,the difference of inactivation effect is not significant.
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The current study measured the available chlorine concentration in commercial and household chlorine bleaches (referred to here as "disinfectants") in the liquid and spray forms. The available chlorine concentration in commercial liquid disinfectants is regarded as 5%. However, the results indicated that the available chlorine concentration in commercial liquid disinfectants was 4.39-6.53%, thus the available chlorine concentration was lower than 5%. Household liquid disinfectants were purchased at different times. Liquid bleach that was purchased 1 month prior had an available chlorine concentration of 5% or higher, while liquid bleach that was purchased 6 months prior had an available chlorine concentration of less than 5%. Liquid bleach that was purchased more than 6 months prior had an available chlorine concentration of less than 5%. As time passed after the liquid bleach was purchased, the lower its available chlorine concentration. Commercial spray bleach had an available chlorine concentration of 2.02-3.08%.
Bleach
Disinfectant
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The mechanism and efficiency of chlorine removal by calcium in different atmospheres were investigated by means of thermogravimetry.The PVC was used as the chlorine emission source.The results indicated that PVC can be used as the chlorine emission surce.The efficiency of chlorine removal by Ca(OH)\-2 is the best in the three calcium compounds.The mechanism of chlorine removal by Ca(OH)\-2 is the same as by CaO.The chlorine removal mechanism in different atmospheres is individual.CaCl\-2 will be decomposed under high temperature.
Thermogravimetry
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Chlorine content,distribution and accumulation,yield and quality of flue-cured tobacco were influenced remarkably by different amount of chlorine applied.Chlorine content and accumulation increased remarkably as increasing chlorine rate.There was a linear relationship between chlorine rate and chlorine content or accumulation.Chlorine distribution in upper leaves increased evidently as increasing the amount of applied chlorine from 0 kg/hm~2 to 48 kg/hm~2;and distribution in middle and lower leaves increased remarkably as increasing the amount of applied chlorine to 96 kg/hm~2;chlorine distribution in stem and roots had degressive trend as decreasing the amount of applied chlorine.Yield,quality and chemical composition were the best with 24 kg/hm~2 of chlorine applied;no chlorine applied or applied chlorine more than 24 kg/hm~2 had worse effects on yield and quality.
Curing of tobacco
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In this study, the factors that leading to loss of chlorine residual in water distribution systems were investigated. A series of experiments performed on real water samples collected from effluent of water treatment plant before chlorination. The results showed that bulk chlorine decay rate varied significantly with the initial chlorine concentration and the organic content of water.Further, this paper explores the performance and the potential applicability of the parallel first order model and second order model to represent the bulk chlorine reactions. The modelling and simulation study lead to define the bulk chlorine coefficients as a function of initial chlorine concentration (Co) and COD by developing mathematical equations related to these parameters.
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