Water Science & Technology: Water Supply Vol 1 No 2 pp 237–246 © IWA Publishing 2001
Toxic cyanobacterial blooms in a drinking water reservoir - causes,
consequences and management strategy
M Tarczyńska*, Z Romanowska-Duda**, T Jurczak*** and M Zalewski****
*
Department of Applied Ecology, University of Lodź,
Banacha 12/16, 90-237 Lodź, Poland
**
Department of Plant Growth Regulation, University of Lodź,
Banacha 12/16, 90-237 Lodź, Poland
***
Department of Environmental Chemistry, University of Lodź, Pomorska
163, 90-236 Lodź, Poland
****
Department of Environmental Chemistry, University of Lodź, Pomorska
163, 90-236 Lodź, Poland
ABSTRACT
Eutrophication of reservoirs used for drinking water supplies is a very
common problem, particularly in lowland reservoirs. Long water retention
time (60-120 days) favours cyanobacterial bloom occurrence in
Sulejów Reservoir, Poland. The localisation of the water intake
in a bay exposed to north-east winds favoured the Microcystis bloom
accumulation, which formed a 0.5 m thick dense scum for the first
time in September 1999. Cyanobacterial hepatotoxins can pose a
potential health problem because the presence of about
0.8  g/l microcystins was detected in drinking water during three
series of analysis. An investigation of the efficiency of each stage
of water treatment processes in the elimination of microcystins showed
that pre-chlorination, coagulation, and rapid sand filtration were
ineffective in removing microcystins from water. Significant elimination
was observed after ozonation and chlorination. The concentration of
microcystins in bloom material was between 12 to 860 g/g dry weight
of phytoplankton biomass. Management strategies for reservoirs should
consider the important role of ecohydrological processes, which are
often very easy to regulate, and which can be useful for bio-manipulation
of the water ecosystem.
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