Prereservoir phosphorus precipitation has had few reported applications.
However, results have been very encouraging, and it will probably be used with
Lathrop (1982) has reviewed this method.
increasing frequency,
Bannink, van der Meulen, and Peeters (1980) and Hayes et al. (1984)
report on the use of iron salts to treat river water entering reservoirs in
Water
improvements were
The Netherlands and England, respectively.
However, Hayes
noted, as well as reduced treatment costs of drinking water.
et al. (1984) noted that internal phosphorus release during summer months was
responsible for algal blooms, suggesting that iron-bound phosphorus may have
been released under anaerobic conditions.
Harper, Wanielista, and
(1983) have suggested the use of the
sludge,:produced during potable water treatment, as a cost-effective
No results appear to be avail-
compound for treating incoming stream waters.
able on their treatment of inflowing storm water to Lake
Florida.
Caution should be exercised in the use of the material from a potable water
treatment plant since the sludge may have very large amounts of organic matter
Thus, its addition to the upper end of a reser-
and phosphorus sorbed to it.
voir could produce a pronounced oxygen demand and little phosphorus removal.
Cooke and
(1986) have found that only a small dose of aluminum
sulfate (1 to 5 mg Al
was needed to precipitate all of the soluble
reactive phosphorus in the Cuyahoga River just above Rockwell Reservoir, Ohio.
The dose to accomplish phosphorus removal was determined with a jar test. To
be certain that only insoluble aluminum hydroxide was formed, an attempt was
made to keep the dose above the level that would produce a
of 6.0 or less.
Since the experiment was conducted on only a pilot scale in August and
ber 1985, long after substantial macrophyte and blue-green algae problems had
developed in the reservoir, there was no expectation of reservoir improvement,
The large volume of aluminum hydroxide
that deposited
and none occurred.
in a small area due to the late summer low-flow conditions was deleterious to
No changes in macroinvertebrates,
benthic macroinvertebrates in this area.
compared with upstream controls, were observed at stations nearer the reser-
voir.
This apparently new and simple (compared with Wahnbach) approach
protecting a reservoir is undergoing further evaluation by Cooke and
Wetlands
Case histories of the use of wetlands, marshes, or small impoundments
with dense vegetation demonstrate that these systems can remove
percent or
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