| When L. A. County Department of Public
Works inherited Belvedere Lake from L. A. County Parks & Recreation,
they were left to contend with a 2 acre lake with an average depth of 3.5
feet, that had been ineffectively converted from a retention basin to an
artificial lake, complete with Bass, Trout, Catfish and migratory birds.
The summer water temperatures reach 98.6 degrees F, and there was little
or no circulation, despite the aerators. |
The designers of this transformation
misapplied certain technologies that left an unbalanced ecosystem. The conversion
steps were as follows:
- Drain the retention basin and
line with a polyethylene liner
- Line with 2 feet of clay and compacted
soil
- 8 inch layer of Zeolite was added
- 8 tons of aluminum sulfate was
added
- 6 aerators, that did not assist
circulation were installed
|
| One major mistake, in this initial
plan was using Zeolite as part of the bottom. Zeolite is effective for binding
ammonia, when it is contained in a filter, which can be cleaned. Once Zeolite
has bound all the ammonia it can, it starts to leach it back into the water,
further reducing water quality, instead of improving it. The Zeolite also
lowered the water pH to 4.2, which was too acid for fish, so the aluminum
sulfate was added to balance the pH to 7.9 to 8.1. Flocculant characteristics
of aluminum sulfate were also deemed beneficial, initially producing clear
looking water. Toxicity of this volume of aluminum was overlooked. |
| After a few months, algae and weeds
developed, and ammonia toxicity led to fish kills. Copper sulfate was tried
to kill weeds and algae, but it was not really effective, since the dead
algae just added to the nutrient load, feeding the next batch of algae,
as soon as the copper dropped into the sludge at the bottom. Copper sulfate
also did nothing to curtail the rising ammonia levels. |
| Constant manual labor was required
in a vain attempt to control the algae, weeds and debris in the lake. As
they got more desperate, various technologies were tried, and all failed. |
| At this point, AquaBio
Environmental Technologies was called in to remediate the lake.
A thorough survey and analysis of water and sludge led to an initial prescription
of Alken Clear-Flo 1200 and 1001. |
| Ms. Vitela also suggested that a concrete
barrier in the runway be removed to improve circulation, and this was accomplished. |
| As the water quality improved, Alken Clear-Flo 1000 was prescribed to attack
the sludge. As the organic sludge was degraded, new pockets of aluminum
sulfate were uncovered, causing the pH to suddenly spike as high as 9.6.
This led to a constant battle to control the pH below 8.5, to maintain both
healthy fish and effective bacterial performance. Today, we would use Clear-Flo 1005, our best sludge degrading formula. |
| Titration tests led Ms. Brankovic-Vitela
to the correct dosage of diluted hydrochloric acid to restore pH. Weekly
monitoring determined when additional acid was needed. In addition to uncovering
aluminum sulfate while degrading the sludge, the Alken Clear-Flo 1000 would
periodically encounter pockets of copper sulfate, in sufficient strength
to kill the product, leading to the requirement for higher doses at times. |
| An ultra-violet light inhibitor (similar
to Aqua Shade) was included in the program, during the height of
the summer, to compensate for the lack of nearby shade trees and the shallowness
of the lake. |
| To control weeds immediately, Sonar
was applied once in the Spring, followed in 10 days by Alken Clear-Flo
1200 with 1001 to clean up the debris. Today, we would use CF 1008, specially created for this purpose. |
| As the aerators ceased to function
and were not repaired because of prohibitive costs, two new aerators, of
different design, were installed to supply both oxygen and circulation. |
| When overflow from storm sewers brought
a fair amount of hydrocarbons, Alken Clear-Flo 7026 was included
in the treatment program. Today Alken Clear-Flo
1006 is used instead of this discontinued product. |
| The maintenance for the lake includes
weekly monitoring of pH, BOD, ammonia and the contents of storm water runoff,
with treatments applied as needed to maintain a balanced, viable ecosystem.
With its variety of parameters, this was one of the most challenging projects
for AquaBio
Environmental Technologies and Alken Clear-Flo. |