Disinfection Efficacy Of Chlorine Research Articles

The Identification of Selective Pathogenic Microbial Community Biofilms in Different Distribution Pipeline Materials and Their Disinfection Kinetics

Biofilms in water distribution lines strongly affect water safety as they are the main carriers of pathogens. The current study investigated the biofilm formation and identification of selected pathogens in different distribution pipeline materials and their disinfection method in an annular reactor (AR). Initially, the quality of the flowing water from each pipeline material was analyzed, i.e., pH, TDS, EC, turbidity, and salinity; then, the biofilm formation was monitored for each material, i.e., ABS, PC, PVC, PP, and HDPE. Further, the disinfection kinetics of biofilm at different chlorine doses, i.e., 0.5, 1.0, 1.5, and 2.0 mg/L, was investigated. The selected pathogens, i.e., E. coli, Pseudomonas, Shigella, Salmonella sp., and Vibrio sp. were identified in biofilms formed in different pipeline materials. The disinfection kinetics results showed that a chlorine dose of 2.0 mg/L was the most effective in disinfecting selected pathogens. Following the disinfection kinetics, it was observed that Salmonella sp. was disinfected within 7 days, whereas other pathogenic biofilms were disinfected within 14 days. The efficacy of chlorine disinfection was affected by the types of pipeline materials. The study outcomes could provide insights into biofilms’ disinfection method and the selection of suitable pipeline materials to ensure drinking water safety.

Effect of peeling, cutting, or shredding of lettuce, carrot, or potato on the efficacy of chlorine disinfection.

Minimally processed vegetables are washed and subsequently disinfected by immersion in water solutions with antimicrobials which reduce the initial pathogenic or spoilage microbial load. Chlorine remains one of the most widely used disinfectants for vegetables and hence the importance of studying its properties. The aim of this study was to evaluate the effect of peeling, cutting, and shredding on the effectiveness of chlorine (200 ppm) as a disinfectant in lettuce, carrot, and potato. Three independent repetitions of each experiment were completed, and data was statistically analyzed. Results showed that the maintenance of the chlorine concentration in the disinfectant solution, over time, depended on the vegetables' preliminary processing technique (whole, peeled, cut, or shredded) (p < 0.05). In general, the disinfection treatments studied reduced Escherichia coli by 1-8 logs. The addition of chlorine in the disinfectant solution allowed greater reduction in E. coli than using water immersions (p < 0.05) and disinfection times longer than 5 min did not improve these microbiological reductions (p>0.05). The vegetables' subdivision (whole, peeled, cut, or shredded) can affect both E coli's reduction and the vegetables' residual chlorine concentration. No trend was observed in terms of sensory differences and their relationship to the vegetables' processing and disinfection. These results suggest that each facility must validate its disinfection processes, according to the conditions established on site and reduction goals related to initial microbial counts, vegetables' quality, processing operations, and other important aspects.

Chlorine disinfection of drinking water assessed by flow cytometry: New insights

Abstract The efficacy of chlorine disinfection was assessed for the first time over a range of disinfection conditions using flow cytometry (FCM) to provide new insights into disinfection processes. Inactivation was assessed for pure culture bacteria (Escherichia coli) and micro-organisms in real treated water from operational water treatment works (WTWs). A dose dependent increase in inactivation rate (k) was observed for both test matrices, with values of 0.03 to 0.26 and 0.32 to 3.14 L/mg min for the WTW bacteria and E. coli, respectively. After 2 min, E. coli was reduced by 2 log for all chlorine doses (0.12 to 1.00 mg/L). In the case of the WTW filtrate bacteria, after 2 min log reductions were between 0.54 and 1.14 with increasing chlorine concentration, reaching between 1.32 and 2.33 after 30 min. A decrease in disinfection efficacy was observed as temperature decreased from 19 to 5 °C for both microbial populations. With respect to chlorination at different pH (pH 6, 7, 8), membrane damage was more pronounced at higher pH. This was not consistent with the higher disinfection efficacy seen at lower pH. when culture based methods are used to assess bacterial reductions. This provides evidence that more understanding into the fundamental mechanisms of chlorine disinfection are required and that methodological alterations may be required (e.g. pH standardisation) to fully utilise FCM over the entire range of chlorination conditions observed in operational environments.

Impact of the organic load on the efficacy of chlorine disinfection against acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus

Impact of the organic load on the efficacy of chlorine disinfection against acute hepatopancreatic necrosis disease‐causing <i>Vibrio parahaemolyticus</i>

The disinfection efficacy of chlorine and chlorine dioxide as disinfectants of Bacillus globigii, a surrogate for Bacillus anthracis, in water networks: A comparative study

Intentional contamination of drinking water with anthrax spores is a concern to water utilities. The spores may become embedded in the distribution pipe corrosion and biofilm, where they will be protected from residual disinfectants. This paper compares the disinfection effectiveness of chlorine and chlorine dioxide on Bacillus globigii , a surrogate for B. anthracis . Batch experiments were performed using both disinfectants. Data was analyzed using the delayed Chick-Watson model to determine the corresponding CTlag (CT = concentration  ×  time) values and Watson plots, which indicate the dominant factors affecting disinfection kinetics. Chlorine dioxide had CTlag values almost one tenth of those observed for chlorine. However, Watson plots showed that exposure time and disinfectant concentrations have equal weights on the inactivation rate of both disinfectants.

The Disinfection Efficacy of Chlorine on Sulfate-Reducing Bacteria and Iron Bacteria in Water Supply Systems

Sulfate reducing bacteria (SRB) and iron reducing bacteria (IRB) that widely exist in water supply networks are the main microorganisms leading to metal corrosion in pipelines. Chlorine is widely used in drinking water supply systems. The concentration of chlorine with SRB declined rapidly after 10 mins and reached 0 mg/L finally whereas it decreased more slowly with IRB. If the concentration of chlorine is lower than 0.2mg/L, IRB cannot be sterilized. It indicates that at the end of water pipes where the concentration of chlorine is required to be 0.05mg/L, chlorine is not effective since the concentration is below the minimum requirement of removing IRB

Disinfection efficacy of chlorine and peracetic acid alone or in combination against Aspergillus spp. and Candida albicans in drinking water

The aim of the present study was to evaluate the fungicidal activity of chlorine and peracetic acid in drinking water against various pathogenic Aspergillus spp. and Candida albicans strains. A. nidulans exhibited the greatest resistance, requiring 10 ppm of chlorine for 30 min contact time for a complete inactivation. Under the same experimental conditions, peracetic acid was even less fungicidal. In this case, A. niger proved to be the most resistant species (50 ppm for 60 min for complete inactivation). All Aspergillus spp. were insensitive to 10 ppm even with extended exposure (>5 h). The combination of chlorine and peracetic acid against Aspergillus spp. did not show synergistic effects except in the case of A. flavus. Complete growth inhibition of C. albicans was observed after about 3 h contact time with 0.2 ppm. C. albicans was less sensitive to peracetic acid. Hence the concentrations of chlorine that are usually present in drinking water distribution systems are ineffective against several Aspergillus spp. and peracetic acid cannot be considered an alternative to chlorine for disinfecting drinking water. The combination of the two biocides is not very effective in eliminating filamentous fungi at the concentrations permitted for drinking water disinfection.

The disinfection efficacy of chlorine and chlorine dioxide as disinfectants of Bacillus globigii, a surrogate for Bacillus anthracis, in water networks: A comparative studyA paper submitted to the Journal of Environmental Engineering and Science.

Intentional contamination of drinking water with anthrax spores is a concern to water utilities. The spores may become embedded in the distribution pipe corrosion and biofilm, where they will be protected from residual disinfectants. This paper compares the disinfection effectiveness of chlorine and chlorine dioxide on Bacillus globigii , a surrogate for B. anthracis . Batch experiments were performed using both disinfectants. Data was analyzed using the delayed Chick-Watson model to determine the corresponding CTlag (CT = concentration × time) values and Watson plots, which indicate the dominant factors affecting disinfection kinetics. Chlorine dioxide had CTlag values almost one tenth of those observed for chlorine. However, Watson plots showed that exposure time and disinfectant concentrations have equal weights on the inactivation rate of both disinfectants.

Influence of disinfection processes on the microbial quality of potable groundwater in a laboratory-scale system model

Groundwater was used to evaluate the influence of the disinfection processes on the microbial quality of potable water distribution systems using laboratory-scale units. Coliform bacteria, heterotrophic plate count and total bacteria were used for the evaluation of the bactericidal effectiveness of each disinfectant. The microbial disinfection efficacy of chlorine, chloramine, ozone and UV irradiation was found to be equally effective in the elimination of coliform bacteria during the first hours (20 min-2 h) after disinfection. Complete elimination of coliforms in hydrogen peroxide treated water occurred after 48 h. More than 4 log cfu . ml −1 (average killing rate) heterotrophic bacteria were killed by all the disinfectants with the exception of hydrogen peroxide (average killing rates: 3-2 log cfu . ml −1 ). However, ozone was highly effective within the first 2 h as shown by the average killing rate of 4 log cfu . ml −1 heterotrophic bacteria in both source waters. The phenomenon of bacterial regrowth was linked to the absence of concentrations of disinfectant residuals. Bacterial regrowth, however, could be detected earlier with chlorine (after 20 min-average regrowth rate 0.064 h −1 , average generation time 10.95 h), ozone (after 2 h-average regrowth rate 0.202 h −1 , average-generation time 5.04 h) and UV treated water (after 2 h-average regrowth rate 0.263 h −1 , average generation time 2.70 h) than chloramine (between 24 h and 48 h-average regrowth rate 0.057 h −1 , average generation time 13.87 h) and hydrogen peroxide treated water (after 48 h-average regrowth rate 0.063 h −1 , average generation time 12.74 h). The greater persistence of monochloramine (7 days) and hydrogen peroxide (14 days) residuals were found to inhibit bacterial regrowth in potable water.

Efficacy of Chlorine Disinfection of Soft Contact Lenses

We evaluated the chlorine system SOFTAB (Alcon) for the disinfection of soft contact lenses. The results indicate that a 1000-fold reduction in microorganisms was achieved within 6 h. Even with the slight interference of residual cleaner and the more significant interference of organic matter disinfection was still achieved.

Effect of Calcium Bicarbonate on Disinfection by Halogens

The inorganic entities in water comprise a significant portion of chemicals in water and their effects upon the disinfection process should be fully evaluated. This investigation was undertaken to determine possible effects of various inorganic chemical additives in water on the efficacy of disinfection by halogens. The chemical used in this experimentation was calcium bicarbonate. Halogen concentrations used were on an equal equivalent weight basis. The test microorganism was \IEscherichia coli\N. The exposure substrate was cold sterile distilled water to which appropriate quantities of calcium bicarbonate were added. All bacterial exposures to disinfectant were performed at pH values 5.0 and 7.0 and a temperature of 2-3°C. Bacterial death kinetics are presented in comparisons of varying additive conditions for each halogen and also for constant additive conditions for all halogens used. A hampering effect of calcium on the disinfection efficacy of chlorine, bromine and iodine was found at the conditions of the experimentation.