The Lake Morey Alum Treatment: Looking Back After 20 Years

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The Lake Morey Alum TreatmentLooking Back After
20 Years

• Eric Smeltzer
• Vermont Department of Environmental Conservation

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Water Quality Problems in Lake Morey(early 1980s)

• Algae blooms of blue-greens and other types
• Dissolved oxygen depletion
• Fish kill of yellow perch in summer 1985
• Septic contamination

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The Lake Morey Diagnostic-Feasibility Study- -
Findings - -

• Watershed phosphorus inputs were low.
• Septic system phosphorus inputs were low.
• Internal phosphorus loading was the main problem.
• Historic events set the cycle in motion.
• Alum treatment was recommended.

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Use of alum to control internal phosphorus
loading in Lake Morey
P
P
P
P
P
P
P
P
P
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Alum TreatmentMay-June 1986

• Liquid alum (aluminum sulfate) and sodium
  aluminate used for pH balance
• Chemicals injected at 8 meter depth to treat 133
  ha (330 acres) of deep sediments
• 440 dry tons of chemicals applied
• Chemical cost 110,000 (with donation)
• Application cost 67,000

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Beneficial Effects of the Treatment
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Reduction in spring phosphorus concentrations
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Reduction in mean summer chlorophyll-a
concentrations
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Increase in mean summer Secchi disk transparency
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Reduction in hypolimnetic phosphorus accumulation
in late summer
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Increase in hypolimnetic dissolved oxygenin late
summer
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Adverse Effects of the Treatment
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Elevated dissolved aluminum levels
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Yellow perch
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Reduction in relative weight of yellow perch
Source Richard Kirn, Vermont Department of Fish
and Wildlife
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Benthic macroinvertebrates
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Initial reductions, followed by increases in
density and number of species in the benthic
community
Statistically different from pre-treatment value
Source Steve Fiske, Vermont Department of
Environmental Conservation
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Lessons Learned

• A phosphorus budget and diagnostic study are
  essential.
• External phosphorus loads should be controlled
  before alum treatment.
• Alum treatment can provide long-term
  effectiveness.
• There are environmental risks that should be
  minimized by proper treatment design.