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Publication Abstract

Aeration - Destratification of Lake Eureka: Second Year Operation Raman, Raman K., and Ralph L. Evans, 1984  Illinois State Water Survey, Champaign, IL,  ISWS C-159    Full Text Available

City-owned Lake Eureka, formed in 1942 by the damming of a branch of Walnut Creek, was created to serve primarily as a water supply source for the city of Eureka, Illinois. The city owns and operates the water treatment and distribution systems.

During the early 1970s, the city began to receive consumer complaints about taste and odor problems in the finished waters. These complaints became numerous and incessant as the years progressed. The severe taste and odor problems encountered during the winter of 1976-1977 marked the end of local tolerance. The city sought an alternate source of raw water supply and switched to groundwater as the water supply source in November 1979.

However, the use of groundwater as a source resulted in increased pumping, chemical, and treatment costs. Since the water treatment plant had not been designed to treat groundwater, the change created a number of operating problems. The volume of softening sludge increased significantly, floc carryover occurred from the settling basins to the filter beds, and the softening sludge discharge pipes frequently clogged, adding to the plant operational and maintenance loads.

A detailed investigation by Lin and Evans (1981), conducted during 1976-1978 to delineate the relationship between odor and commonly measured water quality characteristics in central Illinois impoundments, revealed that for Lake Eureka, the threshold odor numbers (TONs) had high positive correlations with iron, manganese, and ammonia concentrations and chlorine demand values of the lake waters. They found that TONs for the lake water samples obtained from near the bottom at the deep station were generally much higher than those for the samples obtained at mid-depth and at surface sampling points of the deep station. They further reported that the odors of the finished waters in the Eureka water supply systems immediately followed the odor episodes in the lake waters.

In 1981 the Water Quality Section of the Illinois State Water Survey (division of the Illinois Department of Energy and Natural Resources) instituted an in-lake water quality management program for Lake Eureka on the premise that if the factors contributing to taste and odor episodes could be controlled at the source itself, the lake could once again be used as a water supply source. Aeration-destratification in combination with...

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