Detroit Water and Sewerage Department – Belt Filter Press Replacement Project

The Detroit Water and Sewerage Department (DWSD) wastewater treatment plant (WWTP) has had increasing difficulty handling and processing an average daily sludge production of 450 dry tons per day (DTPD) (4 08 dry metric tons per day [ DMTPD ]) generated by the primary settling and secondary treatment processes. Dry weather flows to the facility have been decreasing in recent years. The implementation of a broad Combined Sewer Overflow (CSO) control program has increased wet weather flows to the WWTP and caused increasing solids captured by these CSO facilities to be directed to the WWTP for treatment after each event. Increasingly, the continuous operation of the existing belt filter press (BFP) dewatering units’ results in frequent maintenance problems and production of sludge with lower cake solids and increasing solids recycle. Problems with properly feeding polymer to the BFPs are causing issues with blinding of filter belts resulting in lower cake solids and solids recycle. These problems have caused operational issues resulting in solids build-up in the primary clarifiers and, ultimately, a discharge to the Detroit River with resulting permit violations. The project discussed in this manuscript is focused on addressing dewatering capacity and maintenance problems associated with the BFPs so that the WWTP could come back into compliance with the NPDES permit discharge limits.