Quantcast Applications of Pneumatic Destratification (Cont.)

 
  
 
1969. While the system didn't successfully destratify the entire lake, the system reduced the
stratification in the area around the diffusers and in the vicinity of the dam. The extent of the zone of
influence was difficult to determine; however, some data indicated that the system affected the DO
levels as far as 4 miles upstream from the dam.
Other prototype experiments were conducted in 1976, 1977, and 1978 (Kranenburg 1979)
using a point diffuser system. All of these tests were begun under stratified conditions and were
operated and monitored for approximately 1 week. During the 1976 tests, the air flow rate was not
sufficient to cause total lake destratification, but did succeed in affecting the portion of the reservoir in
the area of the diffuser. There was minimal change in the temperature of the epilimnion, but the
metalimnion and hypolimnion increased approximately 3oC over time (assumed to be a result of vertical
mixing).
In the 1977 and 1978 tests, the influence of the bubble plume was found to extend over the
entire reservoir. The water temperature profile became fairly uniform top to bottom over the course of
the tests, indicating substantial vertical mixing due to either the bubble plume and/or wind mixing. These
tests were used to verify laboratory predictions of the destratification process and did not consider DO
in the process.
Burns (1981) details some of the design and installation procedures used at Tarago Reservoir in
Victoria, Australia. The design uses two 20-m lengths of pipe containing diffusers. Two operational
configurations were tested (one in 1976 and the other in 1977), and both were successful in
destratifying the majority of the reservoir. The 1976 test began with operation of the air system under
strongly stratified conditions. A high air flow rate (150 L/sec) was used to destratify the reservoir (in
14 hr) initially. This was reduced to 50 L/sec to maintain the destratification. During the 1977 test, the
system was started at the beginning of the stratification season. Initially, 50 L/sec was used, but as the
season progressed the air rate had to be increased to 100 L/sec to maintain destratification.
The destratification system designed for the Cotter Reservoir as part of the water supply system
for Canberra, Australia (Smith 1981) used a cross-shaped diffuser system, similar in design to the
diffusers used at Allatoona Lake, Georgia, but smaller. This system was to be used to alleviate high
iron and manganese problems experienced as the hypolimnion became anoxic through the summer. At
the time of publication of the report, the system had been installed, and preliminary testing was taking
place to determine optimum air flow rate and operating schedule. However, further information about
the success of this system has not been published.
Croome (1981) describes two destratification systems used on Kangaroo Creek Reservoir and
Little Para Reservoir, both in South Australia. Kangaroo Creek Reservoir was destratified twice, once
in 1977 and again in 1978 under different stratification intensities. The system utilized two 12.2-m-long
(100-mm-diam) galvanized steel pipes located approximately at the heel of the dam. Sixteen fine
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