For over forty (40) years I have been designing digesters with floating covers. I had always felt that the flexibility these covers provided the operator was essential to the successful practice of the anaerobic stabilization of wastewater solids. During my last ten (10) years of wastewater design it has become increasingly obvious that Brown and Caldwell floating covers even with their better corrosion and scum control no longer meet the environmental requirements of odor elimination and the operational requirements of safety and foam control.