many years after treatment.
The applicability of this procedure to reser-
voirs, where adequate treatment of incoming nutrients may not occur, remains
open to investigation.
This Part describes how the procedure works, how to
apply it, and its cost and effectiveness in lakes.
More reservoir treatments
are needed to better define its effectiveness in this habitat.
Theory and Design
Phosphorus inactivation is carried out through the addition of aluminum
sulfate or sodium aluminate (or both) to the lake or reservoir.
Aluminum has
been the element of choice rather
iron because the complexes and polymers
that form after the addition of either of these aluminum compounds are appar-
ently inert to changes in oxidation-reduction potential, such as would occur
during the development of hypolimnetic anoxia.
Phosphorus will remain bound
to these complexes, whereas iron will release phosphorus as the
poten-
tial falls.
Hayden and
Burrows
and Kennedy and Cooke (1982)
A knowl-
have provided reviews of the chemistry of aluminum salts in water.
edge of this is essential in determining the correct dose and preventing the
an aluminum
development of a high concentration of dissolved aluminum (Al
When
species that has been associated with
to aquatic organisms.
aluminum sulfate
or sodium aluminate
is
added to water, the
dictates the form of hydrolyzed aluminum that will pre-
Settleable, polymerized aluminum hydroxide
predominates
dominate.
below
6 to 8, aluminate above this range, and dissolved aluminum (Al
at
a visible precipitate, is very sorptive of phosphorus, partic-
it.
When aluminum sul-
ularly inorganic phosphorus, and is thus the desired form.
fate (alum) is added to water with carbonate alkalinity, the
and alkalinity
of the water will fall at a rate dictated by the water's initial alkalinity.
to fall below
Low initial alkalinity or an excessive dose would allow
6.0 and thus decrease the amount of phosphorus-sorbing
and increase
the amount of potentially toxic dissolved aluminum (Al
Phosphorus inactivation is a technique in which as much aluminum sulfate
or sodium aluminate as possible, within the bounds dictated by initial alka-
is
and the associated formation of dissolved aluminum (Al
linity,
added to the sediments with the purpose of controlling phosphorus release
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