Preliminary Treatment at Calumet WRP: A European Approach to Grit Removal

The Metropolitan Water Reclamation District of Greater Chicago (District) has utilized aerated grit chambers with chain-and-flight collectors for more than 50 years. While the aerated grit chambers have proven effective, the District's extensive experience has found the chain and flight system very maintenance intensive with high operation costs. The District sought an approach that would continue the use of aerated grit chambers but effectively remove the grit in a different, less costly way. After completing a facility survey and life cycle cost evaluation, the District and the design team developed a unique approach: a traveling bridge with a scraper modified to include an airlift, plus the addition of a fixed submersible pump at the head end of the grit chamber. This combination provides a unique system well suited to handle grit loading under both dry and wet weather conditions, while reducing maintenance requirements and associated costs.