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Bacteriological evidence of water pollution
2022-12-05
Assistant Professor Dr. Muthanna Badie Farhan
Upper Euphrates Basin Developing Centre / University of Anbar
The direct investigation of the presence of pathogenic bacteria in the water does not It is a useful routine examination from a practical point of view for the presence of water contamination with these pathogenic bacteria for several reasons, including the presence of pathological bacteria in the water in low numbers concerning the bacteria that live normally in the intestine In addition Until the period of survival in the water is less than that of bacteria, Likewise, the length of the period required for the emergence of infection, for example, if there is one case of water pollution with typhoid disease, then the symptoms of the disease appear after two weeks with the appearance of fever and another week or more for its diagnosis. It is known that the intestines of humans and warm-blooded animals contain large numbers of bacteria, most of which are non-pathogenic strains. Among these bacteria, is Escherichia coli Which is found in abundance in the stool, for these reasons, the investigation of the faecal bacteria that are found naturally in the human intestine is easier, faster, and less dangerous in isolation and diagnosis, and its presence in the water indicates the possibility of the presence of pathological species, and its absence indicates the absence of pathological bacteria. Four bacterial groups are used as a vital indicator of water pollution with sewage water, through which pathological bacteria can be inferred. These groups are:
1- Coli bacteria (coliform bacteria):
It includes a group of bacteria, the most important of which are bacteria Escherichia coli Which is mainly used as an indicator of water contamination with pathogenic bacteria, The reason for using it is an indicator of water pollution due to many reasons, including the presence of bacteria, especially E.coli permanently in the human intestine and large numbers more than pathogenic bacteria, as they are excreted at a rate of thousands of millions per day within the faeces of the average person, and they live in the water for a longer period compared to pathological microorganisms, and the other reason is that the average person does not It sheds pathological microorganisms such as typhoid bacteria, but it excretes these bacteria in the event of infection with this disease. Thus, the presence of coliform bacteria in the water sample taken is a warning that the water may be contaminated with dangerous pathological microorganisms. Because of the bacterium, coli Fecal source while there are other members of the coliform bacteria, whose source is not faecal, It is also able to decompose lactose, acid and gas such as bacteria Enterobacter aerogenes, that are found on plants, grains, and in the soil, such as a bacterium Klebsiella originating from the respiratory tract, so after detecting a group of coliform bacteria in the water, a distinction must be made between the faecal and non-faecal lactose-breaking microbes, as for the rest of the intestinal bacteria. Such as Shigell, and Salmonella Proteus It is not hydrolyzed for lactose. And to distinguish between the faecal group, represented by E. coli bacteria and the non-faecal group, represented by Enterobacter aerogenes bacteria. A set of tests known as the IMViC Test, In addition, an Ekman test may be performed Eijkman using McConkey liquid medium (MacConkey both), as well as examining the growing colonies on the medium Eosin Methylene Blue Agar (EMBA), If it is proven after these tests, the presence of bacteria E. coli, This means that the water from which the test sample was taken is not It is suitable for drinking and not for other uses while the presence of E. aerogenes bacteria. This water is allowed to be used.
2- Staphylococcus faecal streptococci
These bacteria are found in faeces, but to a lesser extent than Streptococcus E. coli the presence of streptococcus bacteria in the water indicates that the water is contaminated with water sewer recent pollution, i.e. that occurred less than a year ago24 hours.
The group of spherical streptococci includes several genera through which we can infer the source of pollution in the water, for example, the presence of bacteria Enterococcus faecalis which comes from human waste and Streptococcus facial bacteria which comes from animal waste. It was noticed in some cases that there were negative water samples for the coliform group, and at the same time, it was positive for the pathogenic Salmonella bacteria test. Therefore, it is recommended in this case to conduct a Double test for the detection of both faecal coliform and faecal streptococcus bacteria streptococci faecal It also benefits from the results of this Double test check whether the source of sewage pollution is human or animal. In human waste, we find that the number of E. coli bacteria is much larger than the number of Streptococcus bacteria unlike in the case of animal waste.
3- Clostridium perfringens
They live in the water longer than coliform bacteria. It is found in the faeces of both humans and animals, but in smaller numbers than E. coli, bacteria and their numbers range from 1,000 to 100,000 per gram, and they are also found in the soil.
The presence of these bacteria in the water indicates that the water has old sewer contamination that has been around for more than three days and may reach several weeks. And since these bacteria are resistant to inappropriate conditions, their presence in the water also indicates contamination from industrial waste, because other types of bacteria do not withstand the toxic effect of that waste and die.
4- Pseudomonas aeruginosa
There are Ps. Aeruginosa bacteria in sewage and many polluted rivers are often found in waters containing more than 1000 coli faecal bacteria per 100 ml of water. For this reason, they are not found in drinking water. As for their number in river water, it is related to the degree of contamination of this sewage water. If the number is less than 1 for each 100, this indicates that the water is polluted by sewage water. Pollution is considered small if the number ranges from (1-10) for every (100 ml) of water, but if the number exceeds 100 for every 100 it is evident that this water is much polluted. There are also Ps. Aeruginosa bacteria in the water are associated with other types of bacteria indicative of faecal pollution such as E. coli and then its presence is considered additional evidence of pollution, especially when the water is doubtful as if it is a cause for diarrhoea which needs to be investigated about these bacteria. The percentage of E. coli bacteria to Ps. Aeruginosa is usually between1:10 approximately.
