IMPACT OF FeCl3 ADDITION FOR PHOSPHORUS REMOVAL ON SOLIDS PROCESSSING AT THE JOHN E. EGAN WATER RECLAMATION PLANT

A full-scale study was undertaken in January 2007 at John E. Egan Water Reclamation Plant (Egan WRP) in Schaumburg, Illinois, to evaluate the impact of ferric chloride (FeCl3) addition on solids processing. Ferric chloride was added to the mixed liquor (ML) to treat to a target effluent level of 0.5 mg/L total phosphorus (TP). This investigation followed a similar study, which was part of the Water Environment Research Foundation Nutrient Removal Demonstration Project study in 2005 in which FeCl3 was added in the ML for phosphorus precipitation. During this study, operational problems in gravity belt thickeners (GBTs) were reported during thickening of waste activated sludge (WAS).Thickening of WAS by GBTs and anaerobic digestion and centrifugal dewatering operations were monitored during the recent study and compared against background data. The GBT operations were closely monitored. No operational problems are reported in the entire solids processing including GBTs. Polymer and FeCl3 demand significantly reduced in dewatering operations.