(Kennedy 1978, Kennedy and Cooke 1982, Cooke et al. 1986).
The objective is
to control phosphorus release for a period of at least several years. Another
procedure, known as phosphorus removal, has been used to add small amounts of
an aluminum salt to water for the purpose of removing the phosphorus in the
water column rather than giving sediments a maximum dose to control phosphorus
release.
Phosphorus removal has been used very effectively in special situa-
tions such as the interception of nutrients released
vegetation
in the fall (Funk et al.
and it has been used as a
for incom-
ing streams water (Part III).
Fly ash, the airborne particulate matter (5 to 100
that is trapped in
in coal-fired power plants, has been suggested as
another type of phosphorus inactivant for lakes and reservoirs (Tenney and
Echelberger 1970).
Fly ashes have very large sorptive areas and are high
Therefore, they would sorb phosphorus.
Na, and Al.
Fly ash appears
to be an attractive option for improving reservoirs because the material is
produced in very large quantities and only about 20 percent of it has been
used for purposes such as the manufacturing of cement
et al. 1980).
fly ash treatments have produced serious negative environmental
Unfortunately,
impacts, due primarily to the presence of heavy metal contaminants.
Aluminum dosage to a reservoir for the purpose of removing phosphorus
from the water column is determined by jar tests. Aluminum salts, usually
increasing
a
of continuously
aluminum sulfate,
stirred beakers containing reservoir water and reservoir water spiked with
After settling, phosphorus concentration is mea-
known amounts of phosphorus.
sured, and the amount of alum required to obtain the desired phosphorus
removal is used to calculate the tonnage of alum needed to treat the water
column (Peterson et al. 1973, 1974; Cooke and Kennedy 1981). The amount of
alum added is usually so small that large
shifts and the appearance of
However,
alkalinity, and dissolved alu-
dissolved aluminum do not occur.
minum must be measured to be certain that potentially deleterious conditions
do not occur.
Kennedy (1978) was the first to suggest that the most desirable lake
treatment would be to add as much aluminum as possible, consistent with envi-
ronmental safety, to the phosphorus-rich sediments rather than to the water
column, with the purpose of inactivating this sediment store.
He developed a
procedure for obtaining the maximum dose for a lake by considering the
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