Results of Phosphorus Minimization Studies for Pulp and Papermill Activated Sludge Systems Located Around the Great Lakes, 1997 Environmental Conference Proceedings

Recent environmental requirements for low effluent phosphorus concentrations for pulp and papermill activated sludge systems have resulted in wastewater treatment problems for some of these systems. Some systems have phosphorus needs for successful wastewater treatment that require an effluent phosphorus concentration above 1.0 mg/L, the most common standard in use. This paper presents recent findings from phosphorus minimization studies conducted for several pulp and papermill activated sludge systems located around the Great Lakes in Wisconsin and Michigan. Two approaches have been taken to assess the actual phosphorus needs of an activated sludge system. In the first approach, statistical analyses of at least a year’s data for operational and effluent quality parameters is done to determine at what effluent phosphorus level good treatment plant performance is obtained or lost. In the second approach, a six month to one year study is undertaken during which phosphorus addition to the activated sludge system is systematically lowered in steps, and the resulting impacts on treatment system performance documented. Key biological indices of low phosphorus stress have been filamentous bulking, especially by Nostocoida limicola III; an increase in the activated sludge polysaccharide content, causing polysaccharide bulking and foaming; and loss of BOD removal. The second approach has proven to be the better approach to pinpoint the exact required phosphorus level to maintain good treatment plant performance without upset due to low phosphorus. Three case examples of phosphorus minimization studies are presented to illustrate these methods.