Drinking water Coliform bacteria

Kampfer P, Nienhuser A, Packroff G et al (2008) Molecular identification of coliform bacteria isolated from drinking water reservoirs with traditional methods and the Colilert-18 system. Int J Hyg Environ Health 211(3-4) 374—384... 

Biofilm samples and microbial contamination of drinking water flowing through the model in result of biofilm formation were analyses with standard methods (APHA, 1992). Number of heterotrophic bacteria (R2A/22°C/7d) coliforms and bacteria from different physiological groups, including corrosion related bacteria were determined. 

From the viewpoint of bacteriological and biological requirements the permissible indicators involve the quantity of coliform and mesophile bacteria. Of course, drinking water must not contain any pathogens, microscopic and macroscopic organisms which come from waste- or surface waters. The Standard limits the number of infusoria and colourless flagellata. The rated indicators also include the amounts of psychrophile bacteria and enterococci. 

While the MCLG for the microbial agents Giardia lamblia, Legionella, total coliform bacteria, viruses, and standard plate count has been set at zero, the MCL is based on the treatment technique. It is critical that no bacteria, viruses, or other microbial agents be found in the drinking water supply. 

The primary sources of bacteria in water are human and animal wastes, seepage or discharge from septic tanks, sewage treatment facilities, and natural soil and plant bacteria. Pathogenic organisms can cause intestinal infections, dysentery, hepatitis, typhoid fever, cholera, and other illnesses. The EPA requires that aU public water suppliers regularly test for coliform bacteria and deliver water that meets the EPA standards. The EPA Maximum Contaminant Level (MCL) for coliform bacteria in drinking water is zero total cohforms per 100 mL of water (56). 

Coliform bacteria should not be detectable in 100 ml of drinking water. In the case of mineral water, they must not be present in 250 ml. 

Multiple-tube fermentation method Three-step method of testing for coliform bacteria in drinking water. 

The multiple tube fermentation method requires the use of replicate tubes and dilutions of samples. The fermentation products of lactose include mixed acids and gas, which is usually detectable. Coliforms are reported in terms of MPN of organisms present. MPN tables are based on a random dispersion of coliforms (Poisson distribution). Failure to shake the samples very well will result in a nonrandom distribution that will underestimate the actual density of the bacteria. If testing drinking water, a single bottle containing 100 mL may be used or 5 replicate tubes with 20 mL each or 10 replicate tubes with 10 mL each. If testing nonpotable water such as salt water, brackish water, or sediments, multiples and subsamples of 10 mL (e.g., 0.1 1.0 10 mL) should be used. 

Presence/absence test for total coliforms This test uses P-B broth and is intended for obtaining qualitative information on the presence or absence of coliform bacteria in samples, particularly drinking water samples. The test is usually used to examine on a... 

The final criterion of satisfactory sterilization of domestic water is the reduction in bacterial concentration to very low values. Bacteriological examination of drinking water uses the coliform bacteria Escherichia coli—often referred to as E, coli) as an indication of the purity of the water since these bacteria are the normal inhabitant of the intestinal tract and constitute about 30% of the dry weight of adult human feces. Water suitable for human consumption should contain less than one viable coliform per 100 mL. 

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