significant increase in the area of the reservoir that is infested with sub-
merged macrophytes, since the outer depth
of their growth can be
limited.
There is evidence that this has occurred in West Twin Lake, Ohio
(Cooke et al.
and in Long Lake, Washington
Welch, and Michaud
1983).
ash presents a serious environmental hazard and should not be used
in reservoirs (Cooke 1980).
Fly ashes from bituminous coals (eastern United
States) are high in sulfur, and aquatic solutions
This envi-
low
ronment will promote
of the heavy metals which they contain.
coals (western United States) produce a high
(above
12) in solu-
tion and also contain heavy metals
et al. 1980).
and
of
(a) high
(1976) report the following negative attributes of fly ash:
treated waters, (b) dissolved oxygen depletion, (c) appearance of sulfide,
(d) heavy metal release, and (e) physical crushing of
or clogging of
Various laboratory and field studies have demonstrated the toxicity of
gills.
various fly ashes to fish and invertebrates (e.g., Cairns, Dickson, and
1972; Guthrie and Cherry 1979).
Summary
Phosphorus inactivation is a technique to control the release of phos-
phorus from reservoir sediments, a source of "internal loading" that can main-
Aluminum
tain severe algal blooms even after diversion of nutrient income.
sulfate or sodium aluminate will produce the formation of aluminum hydroxide
This hydroxide is a visible
or pre-
in water with carbonate alkalinity.
cipitate that is very sorptive of phosphorus and will not release it under
A procedure for determining the maximum
conditions of low dissolved oxygen.
This dose will produce the largest
dose for a reservoir has been outlined.
amount of
possible, consistent with environmental safety.
Case histories of the procedure have been reviewed (Cooke and Kennedy
1981, Cooke et al. 1986).
This treatment has been effective for up to
12 years in controlling phosphorus release and in improving the
state
mg
of lakes.
Large (575 ha), deep (18 m), soft-water
lakes have been successfully
water (750 mg
and shallow (2
Application procedures for very large areas, such as many
treated.
ervoirs, have not been developed.
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