Algal Bioremediation of the Berkeley Pit Lake System: An In Situ
Test Using Limnocorrals
Principal Investigator: Dr. Grant Mitman
gmitman@mtech.edu
Nine 1-meter diameter by 3-meter long limnocorrals were deployed
into the Berkeley Pit lake in June, 2004 to determine if eutrophication
of the surface water would aid in establishing an algae population.
The theory was that the establishment of an algae population would
lead to a reduction of dissolved metals concentrations in the photic
zone. A limnocorral is an enclosed experimental apparatus, open
at the top and closed at the bottom, used to simulate the actual
physical, chemical, and biological conditions of a lake environment
within a controlled volume of water. The limnocorrals were broken
into three replicate groups, with three limnocorrals in each group.
In each group of three, one limnocorral was unnutrified, one was
nutrified with 5 mg/L nitrate and 2 mg/L phosphate, and one was
nutrified with 10 mg/L nitrate and 4 mg/L phosphate. Additionally,
each limnocorral was monitored at three depths, the surface (0 ft.),
1.5 meters below the surface, and 3.0 meters below the surface.
Water samples were collected three times in a six month period and
analyzed for field parameters, dissolved metals, algae counts, bacterial
counts, and nitrate and phosphate concentrations. In the 120 day
monitoring period, algae counts did increase from levels below the
detection limit to 2.8 x 106 cells per milliliter. Control and nutrified
limnocorrals showed statistically significant (95% confidence interval)
differences for arsenic, copper, and iron concentrations. Level
of nitrification and depth did not appear to play a role in the
metals concentrations.
MWTP Activity IV, Project 30
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