Abstract:
The value of selected indicator micro-organisms for assessment of faecal pollution of
water, as well as the distinction of faecal pollution of animal or human origin of
pollution, has been investigated. The following indicators were included: faecal
coliform bacteria, faecal streptococci, sorbitol-fermenting bifidobacteria, Rhodococcus
coprophilus, somatic and male-specific coliphages and phages of Bacteroides tragilis.
Comparative tests were carried out on water samples collected from a stream and
river, and their respective catchments, exposed to predominantly faecal pollution of
domestic animal origin. The same stream and river with catchments, were sampled
after downstream exposure to run-off from a low socioeconomic developing settlement
with restricted sanitation.
Samples were collected from perennial flow in the stream and river during the dry
season and from storm water run-off during general rain and immediately after thunder
storms. Storm water run-off reached faecal coliform counts of up to 4 400 000 per
. 100 ml, which is equivalent to that of many sewage effluents. Faecal pollution of the
aquatic environment was less during the dry season.
Sorbitol-fermenting bifidobacteria were identifiable with faecal pollution of human
origin, and R coprophi/us with that of animal origin. Male specific coliphages were
identifiable with sewage pollution as well as general faecal pollution of water.
Certain selected ratios for the indicator organisms indicated possible distinction
between faecal pollution of human origin and faecal pollution predominantly of animal
origin under certain circumstances.
Phages of B tragi/is were not detected in any of the samples, which implies that their
application in this situation would require more sensitive techniques.
The results show that the run-off from the developing settlement constituted a major
source of pollution for a river catchment which downstream is used as a source of
water for human consumption and that faecal pollution of human and animal origin can
reliably be distinguished by means of combinations of appropriate indicators.
