United States to be treated with aluminum to control internal phosphorus
release.
average summer
A dose of alum equivalent
the
to
phosphorus load was added to the hypolimnion
1986. Deep-water phos-
phorus concentration, internal loading, and.blue-green algae were reduced
Algal biomass remained high because a bloom of
relative to previous summers.
the dinoflagellate Ceratiwn occurred.
External phosphorus loading remained
high and may have contributed to the Ceratiwn bloom (Kennedy et al. 1987).
Annabessacook Lake-is one of the largest
Annabessacook Lake, Maine.
(575 ha) water bodies to be treated by this method. The lake supported
intense blue-green algal blooms, even following nutrient diversion, due to
Since the water is soft (20 mg
only
internal phosphorus loading.
small amounts of aluminum
could be used before
6.0 was reached and
dangerous levels of dissolved aluminum
appeared.
A mixture of aluminum
sulfate and sodium aluminate in a
ratio was determined through jar tests
Over an
to be a dose that would maintain
in the 6 to 7 range.
period, this dose was applied to the top of the
ha) with a
barge upon which tank truck trailers had been driven. A concentration of 25 g
-3
-3
was applied to the
Al m
was applied to the
to 10-m contour; 35 g Al m
10-m contour and deeper (Dominie 1980).
A 65-percent reduction in internal phosphorus loading occurred in summer
Blue-green blooms were absent in 1979
1979, following the 1978 application.
(Dominie 1980).
Pickerel Lake, Wisconsin, and Long Lake, Washington.
Application to
shallow, nonstratified lakes was believed to be inappropriate because it was
thought that the aluminum hydroxide would be dispersed and relocated during
This problem is important because many shallow, eutrophic
turbulent weather.
reservoirs might also experience this problem.
This concern is supported by the results of the phosphorus removal
treatment of shallow, holomictic Pickerel Lake, Wisconsin. A dose of 7.3 g
-3
Al m
was applied in April 1973, and total phosphorus was sharply reduced.
After a series of mixing events, total phosphorus returned to pretreatment
levels and an analysis of the sediments showed that the aluminum hydroxide
This left areas of the sed-
had been redistributed to the lake's center.
iment free to continue phosphorus release (Knauer and Garrison 1980).
At Long Lake, Washington, however, a maximum dose of aluminum sulfate
Total phosphorus declined, along with phytoplankton biomass and
was applied.
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