Download Occurrence of algae and indicator bacteria in an open drinking

Occurrence of algae and indicator bacteria in an open drinking water reservoir and their
subsequent infiltration into the distribution network systems.
The fitness of suitability of drinking water for human consumption in South Africa is measured against the
national standard SANS 241 for both biological and physico-chemical parameters. Water suppliers aim to
produce water that meets this standard in order to comply with the Department of Water Affairs incentivebased monitoring system known as the Blue Drop System. Following a rigorous treatment process,
drinking water is supplied to customers through a network of closed bulk water reservoirs and a couple of
open reservoirs. The City Cape Town’s Oranjezicht and Southern suburbs experienced episodes of
clogged filters in their water meters which resulted in low pressure in their shower taps. Water sampling
was carried out at the reservoir and associated distribution network. Sludge samples were also collected
at the floor of the reservoir. Two filamentous algal species Melosira (Bacilliophyceae and Mougeotia
(Chlorophyceae) were isolated and found to be dominant species occurring in the reservoir as well as in
the drinking water samples. Elevated levels of indicator bacteria, metals, inorganic compounds as well as
a cocktail of other algae were also observed in the sludge samples. It was concluded that the filamentous
algae were responsible for the clogging of the filters and had passed through the open drinking water
reservoir into the distribution. The presence of polluted sludge at the bottom of the reservoir presents the
possibility of compromising drinking water quality and infiltration of unwanted pollutants into the system.
This presentation will elaborate on this and other challenges facing the City of Cape Town and how the
City aims to manage these issues in the future.