Water, Sewage & Effluent January February 2019 | Page 22

operational costs. Ideal conditions
are artificially created in gravity sand
filters for natural bacteria that feed
on iron and manganese. Control of
pH and dissolved oxygen are the only
requirements. The 10Ml/day plant has
been in operation for five years. Typical
results from treated drinking water
indicates iron and manganese levels
below 25μg/l.
Another good story in Overstrand
Local Municipality is the successful
outsourcing
of
operation
and
maintenance of all 14 treatment works.
According to Hanre Blignaut, deputy
director responsible for engineering
planning at Overstrand, this was
necessary due to a number of factors.
Acquiring and retaining the required
classes of process controllers at
treatment plants proved to be a challenge.
Effective maintenance of especially
mechanical and electrical equipment
remained a constant headache. The
Figure 1: The bio-filtration process at Preekstoel Water Treatment Works.
New pump and compressor room.
22
Water Sewage & Effluent January/February 2019
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