Application of Cyclodextrin
Polymers in the Removal of Organic Pollutants from Water
Report No: KV 194/07
August 2007
EXECUTIVE SUMMARY
The removal of organic pollutants from water in both industrial and
municipal water is a great challenge to water providers worldwide. Some
of these pollutants are very toxic and pose serious health risks to
humans and animals. Additionally, the presence of organic pollutants in
the water often leads to the corrosion of the turbines that are used
for power generation at power stations. This obviously makes the power
generation process less efficient and thus has cost implications,
especially for the end user. Besides the corrosion of turbines, the
removal of contaminants from water contaminated with organic pollutants
also has a bearing on the total cost of generating clean water. To this
end, municipalities and industries sourcing water from Rand
Water’s treatment plants and Eskom’s power stations
are plagued by high water costs.
Geosmin and 2-MIB are detectable by the human nose at concentration
levels as low as 10 ng/L. These compounds are common water pollutants
and are renowned to cause bad taste and odour in drinking water.
Although geosmin and 2-MIB do not pose any serious health risks to
humans, they impact on the aesthetic and consumer acceptability of
drinking water. Currently available technologies such as activated
carbon are unable to remove these pollutants to low levels (i.e. ppb
levels). In our laboratories, we have found cyclodextrin polymers to be
effective in the removal of a range of organic pollutants from water to
ppb levels. However, these investigations were confined to water
samples deliberately spiked with specific pollutants and have not been
proven with "real" water samples. We sought to integrate data
accumulated in the laboratory by testing and applying these polymers on
a larger scale and on real systems.
Cyclodextrin-based polyurethanes were employed in the removal of 2-MIB,
geosmin and other organic pollutants in environmental water sampled
from Lethabo Power Station (Eskom) and Zuikerbosch Water Treatment
Plant (Rand Water). The water samples were extracted using Solid Phase
Microextraction (SPME) and thereafter identified and quantified using
gas chromatography/mass spectroscopy (GC/MS). The new cyclodextrin
polymer technology was compared with treatment methods currently
applied at the power station and treatment plant. To determine the
environmental friendliness of this technology, biodegradation studies
were also carried out. These entail performing soil burial tests prior
to the characterization of the polymers using thermogravimetric
analysis (TGA), Fourier transform infra-red (FTIR), scanning electron
microscopy (SEM) and Braunner Emmet Tellet (BET).
The extraction and analysis of geosmin, 2-MIB and other pollutants
using SPME and analysed using GC/MS, respectively, were successful.
Also, the removal of geosmin and 2-MIB from the two types of samples
(i.e. the Rand Water and Eskom samples) to ppb levels was achieved
using the cyclodextrin polymers. These polymers showed negligible
degradation upon exposure to the different types of soil over a period
of 119 days.