Microbially Derived Off-Flavor from Geosmin and 2-Methylisoborneol: Sources and Remediation - Reviews of Environmental Contamination and Toxicology - page 12

geosmin levels increased from 34 to 150ng/L on copper sulfate application for
control of geosmin-producing cyanobacteria.
The copper dose required to control a particular alga is not always effective
because of its temporary effects (Izaguirre and Devall 1995) and the higher dose
requirement, especially in alkaline waters, wherein it precipitates. Copper used for
algal control has been found to be toxic to various freshwater fish, and speciation has
a potential role in the toxicity of copper. It has been found that its continued use can
result in copper-tolerant algal strains, requiring even higher doses for control
(Izaguirre and Devall 1995), as evidenced in Lake Norrviken in Sweden (Ahlgren
1970), the Fairmont Lakes in Minnesota (Moyle 1949; Hanson and Stefan 1984),
Mill Pond Reservoir in Massachusetts (McKnight et al. 1982), and Canadian prairie
dugouts or farm ponds (Peterson and Swanson 1988). In Canada, continued applica-
tion of copper sulfate favored the growth of Oscillatoria (Klassen et al. 1970).
Copper tolerance has also been reported in various algae in lakes in Ontario, Canada
(Stokes et al. 1973; Butler et al. 1980) and a river in England (Foster 1977).
Lyngbya , Nostoc , and Phormidium have been reported as copper-resistant blue-
green algae (Palmer 1977). Izaguirre (1992) isolated a copper-tolerant benthic
Phormidium sp., which produces MIB in Lake Mathews, California. The release of
MIB in this reservoir has been linked with a cyanobacterium, Oscillatoria curvi-
ceps , first found in 1978 by Izaguirre et al. (1982). Later, by 1989, Phormidium had
appeared all around the reservoir, following the decline of O. curviceps , which
indicates that eradication of one taste-and-odor producer can be followed by the
proliferation of another undesirable organism (Izaguirre 1992). The tolerance of
Phormidium up to 3.5 mg/L copper in culture has been attributed to the repeated use
of copper sulfate in the reservoir. Zimba et al. (2002) found that weekly applica-
tions of diuron to catfish ponds altered the taxonomic composition of the phyto-
plankton communities as the filamentous cyanobacteria were replaced by coccoid
cyanobacteria. A copper-resistant strain of M. aeruginosa has been discovered by
Garcia-Villada et al. (2004).
It has been observed (Izaguirre and Devall 1995; Tucker 2000; Han et al. 2001;
Boylan 2001; Schrader et al. 2003; Tung et al. 2004) that synthetic algicides have
the following adverse impacts: (i) toxicity toward phytoplankton that can lead to the
death of the entire phytoplankton community and subsequent water quality deterio-
ration; (ii) persistence in the environment; (iii) the public's negative perception of
the use of synthetic herbicides in food fish production ponds; (iv) environmental
safety issues from copper accumulation in the pond sediments; (v) adverse affect
on microbial activity in pond sediments from long-term applications;
(vi) deterioration of water quality resulting in the need for more aeration; (vii) pH
fluctuation; (viii) dissolved oxygen depletion; and (ix) additional costs from multi-
ple treatments as algae can reestablish in nutrient-rich water.
Studies conducted by Tung et al. (2004) on the effect of three different oxidants
on MIB concentration in the presence of cyanobacteria in raw water revealed that
ozonation was the most effective technique for the removal of both MIB and geos-
min. Glaze et al. (1990) reported similar results in which 80%-90% of geosmin and
MIB were removed by treatment with ozone. Ozonation appeared to affect the MIB
concentrations by releasing it from damaged cells and oxidizing soluble MIB (Tung