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The Lake Morey Alum Treatment: Looking Back After 20 Years

The Lake Morey Alum Treatment: Looking Back After 20 Years. Eric Smeltzer Vermont Department of Environmental Conservation. 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

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The Lake Morey Alum Treatment: Looking Back After 20 Years

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  1. The Lake Morey Alum Treatment:Looking Back After 20 Years Eric Smeltzer Vermont Department of Environmental Conservation

  2. 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

  3. 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.

  4. Epilimnion (surface water) Hypolimnion (deep water) Sediments Use of alum to control internal phosphorus loading in Lake Morey P P P P P P P P P

  5. 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

  6. Beneficial Effects of the Treatment

  7. Reduction in spring phosphorus concentrations

  8. Reduction in mean summer chlorophyll-a concentrations

  9. Increase in mean summer Secchi disk transparency

  10. Reduction in hypolimnetic phosphorus accumulation in late summer

  11. Increase in hypolimnetic dissolved oxygenin late summer

  12. Adverse Effects of the Treatment

  13. Elevated dissolved aluminum levels

  14. Yellow perch

  15. Reduction in relative weight of yellow perch Source: Richard Kirn, Vermont Department of Fish and Wildlife

  16. Benthic macroinvertebrates

  17. 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

  18. 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.

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