MECHANICAL DEWATERING OF THE BIOSOLIDS FROM THE METROPOLITAN WATER RECLAMATION DISTRICT OF GREATER CHICAGO'S STICKNEY WATER RECLAMATION PLANT

The Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) is one of the largest producers of biosolids in the United States today. Biosolids generated from the treatment of over 1.5 billion gallons per day (bgd) of wastewater exceed 400 dry tons per day (DT/day). The MWRDGC's solids processing train includes anaerobic digestion, centrifuge or lagoon dewatering, lagoon aging and agitation drying. In order to increase solids processing capabilities in a cost effective manner and continue to produce a high quality biosolids for beneficial reuse, the MWRDGC has decided to expand the existing centrifuge complex at the Stickney Water Reclamation Plant (WRP).The 26 million MWRDGC expanded centrifuge complex contains the following major features:Eighteen (Future expansion to Twenty-one) Sharples DS706 centrifuges each capable of handling 34 dry tons per day of biosolids with a solids capture of 93%.A new central biosolids wet-well and pumping station using a looped distribution piping system with a recirculating return line. This looped system ensures an equal distribution of biosolids to each centrifuge, provides operational flexibility with the variable frequency drives (VFD) biosolids pumps and prevents blockages and stagnation in the distribution system.A three-stage packed bed scrubber to control the odorous gases from the polymer storage tanks, biosolids wet well, dewatered cake conveyance system and the centrate discharge. The scrubbing system was chosen after a detailed study of other odor control technologies including ozone, activated carbon and biofilters.Use of a unique centrifuge cake conveyance system consisting of belt conveyors, incline conveyors, shaftless screw conveyors, and shuttle conveyors to save floor space and provide reliable operation and maximum flexibility in loading railroad cars and trucks in 6 loading bays.Combined railroad and truck loading facility with flexibility to convert 2 loading bays from rail to truck loading using an in-ground rail car pull system.A supervisory control and data acquisition (SCADA) system for biosolids pumping, polymer feeding, centrifuge operation, cake conveyance and struvite and odor control using a network of programmable logic controllers and personal computer workstations.