| Home | Français | ||
|---|---|---|
MICROBIAL POLLUTION
Freshwater bodies polluted by faecal discharges from man, pets, farm animals and wild animals may transport a variety of pathogens such as bacteria (Shigella, Salmonella, Cholera Vibrio, Escherichia), viruses and protozoans. According to the WHO, waterborne diseases account for 5 million deaths annually, worldwide (Ref. 30).Detection of all potential waterborne pathogens is difficult; therefore most water quality surveys use various indicators of faecal contaminations such as total coliforms and faecal coliforms. Bacterial counts, expressed in number per 100 ml, may vary over several orders of magnitude at a given station. They are the most variable of water quality measurements.
In rivers that are relatively free of faecal discharges, or at stations located far downstream of sewer outfalls, total faecal counts are less than 100/100 ml as in the Gläma for example. Most of the GEMS stations in Europe reflect a marked contamination with counts between 1000 and 10 000/100 ml with occasional peaks exceeding 100 000/100 ml. In rivers that receive untreated sewage, coliform counts can well exceed 100 000 counts/100 ml. The lower values in India relative to European rivers may reflect methodological and reporting differences.
| Home | Français |
|---|
