Toxic cyanobacteria, cyanotoxins and drinking water production in Ghana: implications to human health
Addico, Gloria Naa Dzama
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- © 2008 Gloria Naa Dzama Addico. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
The management and control of cyanobacteria and their toxins in drinking water reservoirs and water supplies have engaged the attention of many scientists worldwide due to their negative effects on population health. The cyanotoxin, microcystin, the main focus of this research has been responsible for much documented illness in humans and is the most wildly studied cyanotoxin. The World Health Organization has set a guideline limit of 1 µg/l in drinking water.
A number of methodologies have been used in this research. These include the use of an inverted microscope for the identification and quantification of cyanobacteria species after sedimentation in counting chambers. The biomass of picocyanobacteria was determined by epifluorescence microscopy after staining with DAPI. Extraction, purification and concentration of dissolved microcystins were done using the Solid Phase Extraction method. Identification of microcystins was done through comparison with commercial standards and their characteristic UV- spectra, and quantified by extrapolations of HPLC peak areas at 238 nin to a linear calibration curve for microcystin-LR standard. Nutrients (N0₂-N, N0₃-N and P0₃-P) in reservoirs in Ghana were analysed using the American Public Health Association standard methods.
The results which are the first of their kind from Ghana, and for most part in West Africa, highlight that the water treatment processing currently in place is not effective in removing cyanobacteria cells from the final drinking water. Positive correlations were obtained between cyanobacteria biomass and nutrients concentrations in the reservoirs. Fifteen new cyanobacteria species were
identified for the first time in Ghana of which Cyanogranisferrugineais reported for the first time in tropical waters. Four known microcystin variants -1R, -RR, - LF and -YR in both dissolved and intracellular samples were identified in four drinking water reservoirs.
The study concludes that, the presence and dominance of potentially toxic small sized cyanobacteria such as Aphanocapsa nubilum, Cyanogranis ferruginea, Geitlerinema unigranulatum and other toxic cyanobacteria species like Cylindrospermopsis raciborskii, Planktothrix agardhii and Microcystis spp in the Weija, Kpong, Barekese and the Owabi reservoirs all with basic conventional drinking water treatment facilities, shown to be ineffective in removing
cyanobacteria and their toxins, present a potential risk to human health through exposure to cyanotoxins such as microcystins and cylindrospermopsin. Even though the concentrations of dissolved microcystins obtained in the reservoirs and drinking water supplies were lower than the WHO limit, there is potentially a risk to public health and ongoing monitoring would be a good idea.
- Department of Biological Sciences, The University of Hull
- Hardege, Jörg D.
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