Lower St. Regis Lake, the lowest of a chain of three lakes in Franklin County, Adirondack Region, New York, was subject to severe eutrophication, as indicated by summer-long intense blue-green algal blooms caused by phosphate discharges from a point-source contributing approximately 0.8 g P/(sq m x yr). Sewage from the point-source had been subject to an extended aeration-activated sludge treatment. Ferric chloride was added and ferric phosphate sludge was removed from the basin from July to December 1972, from March to November 1973, and in April 1974. In May 1974 year-round diversion of the effluent to a sand bed 250 meters from the lake was begun. During the summers of 1973 and 1974 there was washout of phosphate from the lake system, and the summer bloom was delayed. In 1975 the usual spring bloom of flagellates and diatoms did not occur, and the summer bloom was further reduced in duration and intensity. The recovery of the lake is thus very much in evidence. The high iron content of the lake, among several other factors, appears to be speeding the recovery; a delaying influence is being exerted by the continued hypolimnic oxygen depletion, however, presumably from methane formed in the sediments.

"EPA Grant No. S-801529." "February 1977." Cover title. Prepared by New York State Dept. of Health, Environmental Health Center and New York State Dept. of Environmental Conservation, Environmental Quality Research Unit, for the U.S. Environmental Protection Agency, Office of Research and Development, Environmental Research Laboratory, Corvallis, Oregon, under EPA Grant no. S-801529. Includes bibliographical references (pages 102-105).