Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. ...Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. To understand the risks of chlorination resulting from the potential selection of pathogenic bacteria, the inactivation, reactivation and regrowth rates of indigenous bacteria were investigated in reclaimed water after chlorine disinfection. Inactivation of total coliforms, Enterococcus and Salmonella showed linear correlations, with constants of 0.1384, 0.1624 and 0.057 L/（mg·min） and R 2 of 0.7617, 0.8316 and 0.845, respectively. However, inactivation of total viable cells by measurement of metabolic activity typically showed a linear correlation at lower chlorine dose （0-22 （mg·min）/L）, and a trailing region with chlorine dose increasing from 22 to 69 （mg·min）/L. Reactivation and regrowth of bacteria were most likely to occur after exposure to lower chlorine doses, and extents of reactivation decreased gradually with increasing chlorine dose. In contrast to total coliforms and Enterococcus, Salmonella had a high level of regrowth and reactivation, and still had 2% regrowth even after chlorination of 69 （mg·min）/L and 24 hr storage. The bacterial compositions were also significantly altered by chlorination and storage of reclaimed water, and the ratio of Salmonella was significantly increased from 0.001% to 0.045% after chlorination of 69 （mg·min）/L and 24 hr storage. These trends indicated that chlorination contributes to the selection of chlorine-resistant pathogenic bacteria, and regrowth of pathogenic bacteria after chlorination in reclaimed water with a long retention time could threaten public health security during wastewater reuse.展开更多
Sachet water was introduced in Ghana to provide safe, hygienic and affordable instant drinking water to the general public. The aim of the study was to examine the effect of storage on the quality of sachet-vended wat...Sachet water was introduced in Ghana to provide safe, hygienic and affordable instant drinking water to the general public. The aim of the study was to examine the effect of storage on the quality of sachet-vended water produced in the Tamale Metropolis. Two brands of sachet water were sampled freshly after production (Six packs or bags), transported to the laboratory and analysed. Samples of freshly prepared sachet water were then stored at ambient room temperature (at 27°C), in a refrigerator (at 4°C) and in the sun (at 40°C). Samples from these three storage methods were collected and analysed on a weekly and monthly basis for a period of three months. The physico-chemical parameters were within World Health Organization limits regardless of the mode of storage. The pH of sachet water ranged from 6.69 to 7.89 with a mean of 7.38 ± 0.31. There was no significant difference (p > 0.05) in the physico-chemical parameters for the sachet water under the different storage conditions over the period. The concern however was the low concentration of these major ions, sodium, potassium, total hardness, calcium and magnesium which seem to pose direct health concerns. The counts of total heterotrophic bacteria ranged from 0.0 to 73 cfu/1ml with a mean of 19.16 (SD = 21.61) of the sachet water samples. Total heterotrophic bacteria regrowth was observed on the third week in all brands stored and gradually deceased numerically throughout the study period. Total coliform regrowth ranged from 0.0 to 5 cfu/100 ml. There was significant difference (p Based on the findings of this study, it is recommended that Food and Drugs Authority and Ghana standard Board should ensure minerals concentrations of sachet water are improved to meet the general dietary requirement.展开更多
基金supported by the National Natural Science Foundation of China(No.51178242)the National Post-doctoral Research Foundation of China(No.023203010)
文摘Disinfection of reclaimed water prior to reuse is important to prevent the transmission of pathogens. Chlorine is a widely utilized disinfectant and as such is a leading contender for disinfection of reclaimed water. To understand the risks of chlorination resulting from the potential selection of pathogenic bacteria, the inactivation, reactivation and regrowth rates of indigenous bacteria were investigated in reclaimed water after chlorine disinfection. Inactivation of total coliforms, Enterococcus and Salmonella showed linear correlations, with constants of 0.1384, 0.1624 and 0.057 L/（mg·min） and R 2 of 0.7617, 0.8316 and 0.845, respectively. However, inactivation of total viable cells by measurement of metabolic activity typically showed a linear correlation at lower chlorine dose （0-22 （mg·min）/L）, and a trailing region with chlorine dose increasing from 22 to 69 （mg·min）/L. Reactivation and regrowth of bacteria were most likely to occur after exposure to lower chlorine doses, and extents of reactivation decreased gradually with increasing chlorine dose. In contrast to total coliforms and Enterococcus, Salmonella had a high level of regrowth and reactivation, and still had 2% regrowth even after chlorination of 69 （mg·min）/L and 24 hr storage. The bacterial compositions were also significantly altered by chlorination and storage of reclaimed water, and the ratio of Salmonella was significantly increased from 0.001% to 0.045% after chlorination of 69 （mg·min）/L and 24 hr storage. These trends indicated that chlorination contributes to the selection of chlorine-resistant pathogenic bacteria, and regrowth of pathogenic bacteria after chlorination in reclaimed water with a long retention time could threaten public health security during wastewater reuse.
文摘Sachet water was introduced in Ghana to provide safe, hygienic and affordable instant drinking water to the general public. The aim of the study was to examine the effect of storage on the quality of sachet-vended water produced in the Tamale Metropolis. Two brands of sachet water were sampled freshly after production (Six packs or bags), transported to the laboratory and analysed. Samples of freshly prepared sachet water were then stored at ambient room temperature (at 27°C), in a refrigerator (at 4°C) and in the sun (at 40°C). Samples from these three storage methods were collected and analysed on a weekly and monthly basis for a period of three months. The physico-chemical parameters were within World Health Organization limits regardless of the mode of storage. The pH of sachet water ranged from 6.69 to 7.89 with a mean of 7.38 ± 0.31. There was no significant difference (p > 0.05) in the physico-chemical parameters for the sachet water under the different storage conditions over the period. The concern however was the low concentration of these major ions, sodium, potassium, total hardness, calcium and magnesium which seem to pose direct health concerns. The counts of total heterotrophic bacteria ranged from 0.0 to 73 cfu/1ml with a mean of 19.16 (SD = 21.61) of the sachet water samples. Total heterotrophic bacteria regrowth was observed on the third week in all brands stored and gradually deceased numerically throughout the study period. Total coliform regrowth ranged from 0.0 to 5 cfu/100 ml. There was significant difference (p Based on the findings of this study, it is recommended that Food and Drugs Authority and Ghana standard Board should ensure minerals concentrations of sachet water are improved to meet the general dietary requirement.
