Statistical Study of Phosphorus Removal in Wisconsin

A statistical study of water quality in the Wisconsin sector of the Lake Michigan watershed revealed that Wisconsin phosphorus removal policy has been only partially effective. A variance components model was applied to water quality data for a sample of 12 municipal treatment plants to test a variety of hypotheses pertaining to phosphorus removal methods and secondary effects on other plant variables. Towns treating with iron compounds achieved significant phosphorus reduction; towns treating with alum did not, possibly because of insufficient alum dosages or incorrect dosing methods. No desirable secondary effects, such as reduction of BOD or suspended solids concentrations, were evident.