Environmental Engineering Reference
In-Depth Information
States such as southern Florida and Puerto Rico and the Virgin Islands in the
Caribbean. Because of the seriousness if this problem in Florida, the U.S. Corps of
Engineers has carried out a comprehensive studies on control of such growths,
including use of physical, chemical, and biological methods of control, which
show that mechanical cutting/removal is expensive and yet the most feasible
control method
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.
Situation in DCs
A study of this problem in southern Nigeria in 1988
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,
where the problem is very serious, led to a review of other potentials for con-
trol, including a comprehensive review by the Asian Institute of Technology
in 1984
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. This again did not come up with any noncostly control methods,
although some potential for harvesting hyacinths for making wood furniture
which was followed by limited use of this method in Thailand
22
and in Japan
for limited commercial making of fiber baskets
18
. Still another potential being
tested in Argentina uses Amazonian flies as a means of biological control
123
.For
reservoirs suffering from heavy hyacinth growth, it may be necessary to utilize
log booms to prevent the hyacinths from entering water intakes.
The survival hardiness of this plant is well shown by observations of its growth
in a major
klong
(waterway) in Bangkok, Klong Samrong, which in 1970 was
relatively free of hyacinth, with the klong used for major boat traffic. However,
progressive pollution by degradable organics resulted in such heavy growth that
the boat traffic had to cease; then came pollution from toxics discharged by indus-
tries, which caused the growth to fade away. Another example is the experience
in Laguna Lake in the Philippines, Manila
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where little growth occurred when
the lake, normally freshwater, was affected by serious periodic seawater intru-
sions; then building of a gate to minimize the intrusion resulted in great increase
in the hyacinth prevalence.
Water Quality Analyses
Problem in DCs
A very common problem with WQ testing by DC
practitioners, both in the laboratory and in the field, is the lack of review
of the test data by WQ testing experts to ensure its reliability. This is due,
usually, to the common belief that the practitioner with a graduate degree is
bound to be correct —hence, no need for such review
66
. As a result, much of
the data are misleading and counterproductive. This problem is illustrated by
Box 4.1, which reviews a practitioner's nonreviewed report to indicate errors
with explanations
61
. The IAAs commonly give grants of testing equipment to
the DCs but do not finance the training that is needed to enable good use of the
equipment.
An additional example is the testing of well waters by the laboratory of the
national water supply agency of the Philippines (very well furnished with donor
grants, with ample equipment and ample staff with ample graduate training), with
