In soft waters, only small amounts of aluminum sulfate can be added
before the
A. R. Gahler and C. F. Powers of the Corvallis
falls below 6.0.
Environmental Research Laboratory
undated report,
OR) sug-
of an aqueous solution,
gested that sodium aluminate, which increases the
could be used with aluminum sulfate to maintain a
between 6.0 and 8.0.
(1978) was apparently the first to successfully use this dose
approach on a large scale when Annabessacook Lake, Maine (alkalinity, 20 mg
was treated with this mixture in an empirically determined ratio of
Another alternative is to add materials
(alum to sodium aluminate).
such as lime or
to buffer the alum. Before attempting an alum treat-
3
ment, the reader is urged to consult the primary literature, especially
Kennedy and Cooke (1982) and Cooke et al.
for a detailed, step-by-step
outline of the dosage determination procedure.
Figure 8 illustrates the design of the application equipment used at
Dollar and West Twin Lakes, Ohio (Kennedy 1978; Cooke et al. 1978, 1982;
Kennedy and Cooke 1982).
The delivery system was mounted on barges, and alum-
inum sulfate, mixed 50-50 with lake water, was pumped to an application mani-
fold that was below the barge at the top of the hypolimnion.
This allowed
direct injection of the inactivant to the nutrient-rich anoxic hypolimnion and
As designed, the
sediments without significant leakage to the littoral zone.
system added 140
of liquid aluminum sulfate
3 days to a
area of 16 ha.
Delivery systems similar to this have been used to treat much
larger areas, but they are all labor-intensive.
The development of a more
rapid application system is needed.
One option, where a large harvester is
available,
to
the front cutter bar to attach the delivery manifold and
the weed storage area to hold alum tanks.
The harvester's hydraulic system
can be used to operate the pumps.*
Ideally, based upon experiences with lakes, the entire area of reservoir
sediments should be treated, particularly the area that becomes anoxic.
Prac-
tically, this may not be possible in reservoirs due to their large size. An
alternative is to determine those areas of reservoir sediments with the
highest release rates of phosphorus and to treat them. This approach may
*
Personal Communication, 1986, G. N. Smith, Aquatic Control Technology,
Inc., Northborough, MA.
51
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