Abstract
To evaluate the microbiological quality of treated and untreated water samples came from urban and rural communities and to examine the relationship between coliforms occurrence and average water temperature, and a comparison of the rainfall levels. A sample of 3,073 untreated and treated (chlorinated) water from taps (1,594), reservoir used to store treated water (1,033), spring water (96) and private well (350) collected for routine testing between 1996 and 1999 was analyzed by the multiple dilution tube methods used to detect the most probable number of total and fecal coliforms. These samples were obtained in the region of Maring , state of Paran , Brazil. The highest numbers water samples contaminated by TC (83%) and FC (48%) were found in the untreated water. TC and FC in samples taken from reservoirs used to store treated water was higher than that from taps midway along distribution lines. Among the treated water samples examined, coliform bacteria were found in 171 of the 1,033 sampling reservoirs. Insufficient treatment or regrowth is suggested by the observation that more than 17% of these treated potable water contained coliform. TC and FC positive samples appear to be similar and seasonally influenced in treated water. Two different periods must be considered for the occurrence of both TC and FC positive samples: (i) a warm-weather period (September-March) with high percentage of contaminated samples; and (ii) cold-weather period (April-August) were they are lower. Both TC and TF positive samples declined with the decreased of water temperature.
Highlights
The contamination of natural water with fecal material, domestic and industrial sewage and agricultural and pasture runoff may result in an increased risk of disease transmission to humans who use those waters.[7,12] Diarrheal disease from contaminated water continues to be a serious problem in developing countries and a lesser, but chronic, problem in developed countries.[8]Human pathogenic microorganisms that are transmitted by water include bacteria, viruses, and protozoa
The tests for coliforms come in two formats, a most-probable-number multiple-tube fermentation based on lactose fermentation with production of acid and gas within 48 hours and a membrane filtration method based on lactose fermentation
Samples were analyzed for total coliforms (TC) using a multiple-tube fermentation technique based on lactose fermentation with production of acid and gas within 48 hours in a lauryl
Summary
Human pathogenic microorganisms that are transmitted by water include bacteria, viruses, and protozoa. The presence of coliform bacteria in drinking water has been seen as an indicator of fecal contamination through cross connection, inadequate treatment, or an inability to maintain a disinfectant residual in the water distribution system.[9] Coliform bacteria are regarded as belonging to the genera Escherichia, Citrobacter, Enterobacter, and Klebsiella. Coliform organisms may not always be directly related to the presence of fecal contamination or pathogens in drinking water, the coliform test is still useful for monitoring microbial quality of treated piped water supplies.[11] Typically, the tests for coliforms come in two formats, a most-probable-number multiple-tube fermentation based on lactose fermentation with production of acid and gas within 48 hours and a membrane filtration method based on lactose fermentation. Fecal coliform is detected with these same methods, but often by using elevated temperatures and different medium formulations.[1]
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