Water Science & Technology: Water Supply Vol 1 No 1 pp 33–41 © IWA Publishing 2001
Enhanced coagulation: a viable option to advance treatment technologies in
the South African context
SD Freese*, DJ Nozaic**, MJ Pryor***, R Rajagopaul****, DL Trollip***** and RA Smith******
*
Umgeni Water, P.O. Box 9, Pietermaritzburg, 3200, South Africa
**
Umgeni Water, P.O. Box 9, Pietermaritzburg, 3200, South Africa
***
Umgeni Water, P.O. Box 9, Pietermaritzburg, 3200, South Africa
****
Umgeni Water, P.O. Box 9, Pietermaritzburg, 3200, South Africa
*****
Umgeni Water, P.O. Box 9, Pietermaritzburg, 3200, South Africa
******
Umgeni Water, P.O. Box 9, Pietermaritzburg, 3200, South Africa
ABSTRACT
Laboratory and pilot scale tests were conducted to compare the
effectiveness of enhanced coagulation with the more advanced technologies
of ozone and granular activated carbon in treating a range of clean,
eutrophic and industrially polluted waters. Particular attention was
paid to the removal of disinfectant by-product precursors, organics
and micropollutants that could be achieved using the various types of
treatment. Reductions of up to 50% trihalomethane formation potential
and between 40 and 70% organic carbon and colour were obtained using
enhanced coagulation, which compared favourably with the advanced
treatment processes. The more sophisticated processes were especially
effective in the removal of micropollutants, this generally being in
excess of 70%, which was not achievable using enhanced coagulation. pH
depression using acid addition allowed for increases in organics removal
at lower coagulant doses and inorganic coagulants were found to be more
effective than the polymeric coagulants for organic matter removal. It was shown that the advanced treatment processes became more cost effective
for larger plants and as water quality deteriorates, but for smaller water
works, enhanced coagulation is cheaper.
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