Chemical Technology April 2015

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Chemical Technology • April 2015
After consultation with the power station staff it was
determined that the cooling water clarifier had been over-
dosed with flocculant and that the water returning to the
tower basin had then flocculated in the basin of the cooling
tower. This sludge had settled to approximately 1 m thick
in the basin and was contaminating the entire south side
cooling water system. The sludge increased the organics in
the entire system and the treatment chemicals could not
control the microbiological growth.
The treatment chemicals’ supplier was contacted and the
dosage concentration increased. The basin was dredged on-
line due to limitations in taking the tower off-line. The sludge
that was removed had turned septic and a full inspection
of the cooling tower basin will be undertaken on the next
outage to ensure that there is no damage to the concrete.
Conclusions
The BOMM device offers a simple means of obtaining
representative sessile samples from Eskom cooling water
systems. The results generated in terms of counts and
corrosion rates offers direction to the chemical suppliers
on the effectiveness of their regimes. The Microbiology
department is in the process of compiling a report which
offers the photograph, the bacterial counts and the corro-
sion rates for the two metals.
References
A list of references for this article is available from the editor
at z
Figure 1: Block one of the BOMM indicating the positions of
the corrosion coupons (red).
Figure 2: Block 2 of the BOMM indicating the positions of the
corrosion coupons and the rope attachment joints.
Figure 3: BOMM complete indicating the nylon insets (yellow)
on the outsides of the blocks
Figure 4: BOMM showing severe fouling and scaling.
Figure 5: BOMM showing biofilm formation and MIC nodule
formation on the corrosion coupons.
Figure 6: Algal fouling of the south cooling water system.
Figure 7: BOMM device from the north cooling tower basin.
Figure 8: BOMM device from the south cooling tower basin.
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WASTE MANAGEMENT