Wij. Poulton et al., MICROBIOLOGICAL SURVEY OF OPEN RECIRCULATING COOLING WATER-SYSTEMS AND THEIR RAW WATER-SUPPLIES AT 12 FOSSIL-FIRED POWER-STATIONS, Water S.A., 21(4), 1995, pp. 357-364
Raw water supplies utilised at 12 fossil-fired power stations, as well
as the corresponding open recirculating cooling water systems were su
rveyed. Visual inspections were carried out and total aerobic and anae
robic bacteria, anaerobic acid-producing bacteria, Thiobacillus., Nitr
obacter spp., sulphate-reducing bacteria (SRB) and algae were quantifi
ed. All raw water supplies and recirculating cooling waters contained
all of the above groups of micro-organisms, with the exception of the
two potable raw water supplies. In 75% of the systems, the numbers of
SRB in the recirculating cooling waters were higher than in the corres
ponding raw water supplies in 92% of the systems, the numbers of total
aerobic bacteria were higher in the recirculating cooling waters than
in the raw water supplies. However, no relationship between the sulph
ate levels in the recirculating cooling waters and the numbers of SRB
could be distinguished, or between the percentage increase in the numb
ers of total aerobic bacteria and the cycles of concentration at which
the system was operated. The frequency polygons of the occurrences of
total aerobic and anaerobic bacteria in the raw water supplies and re
circulating cooling waters did not follow normal distribution patterns
. Visible biofouling deposits were observe at six of the power station
s surveyed and the predominant algal group was the blue-green algae. H
owever, in the raw water supplies, the predominant algal groups were g
reen algae and diatoms. Microbiologically influenced corrosion was ide
ntified in all five of the condensers inspected. Each system was found
to be unique and no generalisations in terms of presence or activity
of micro-organisms could be made.