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Layer aeration is a depth-discrete artificial circulation technique. The method"redistributes" water temperature (heat) and oxygen at middle depths of the watercolumn. A "layer" is created which is bounded above and below by thermoclines. Layeraeration has been used to reduce epilimnetic nutrient loading from the hypolimnion, torestore cool water habitats suitable for cold water fisheries and as zooplankton refuge, andfor managing water supply sources. Relative thermal resistance to mixing (RTRM)profiles have demonstrated that stable stratification with multiple thermocline peaks.Layer aeration of a 523 acre, 70 ft deep, eutrophic water supply lake has beenperformed annually since 1987. An 18-year data record identifies very significantimprovements in resource quality and raw water supply quality. The response to layeraeration occurred in several stages. Overall, summer Secchi disk transparency increasedfrom 1.8 m (6 ft) to 4.6 m (15 ft), due to elimination of bluegreen algae blooms(Anabaena sp. and Aphanizomenon sp.). Deepening of the "compensation depth" into thehypolimnion contributed to restoration of 3300 acre-ft of aerobic cool water habitat. Thehabitat improvement resulted in the re-establishment of large-bodied Cladocera (Daphniasp.) which increases the rate of algal biomass removal by grazing and further improvedraw water supply quality. Several long-term water supply reservoir hypolimnetic andlayer aeration cases are reviewed in this paper that are relative to limnological characteristics and watertreatment relationships. Includes reference, figures.

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Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 9File Size: 1 file , 320 KB