Mill Creek WWTP Anaerobic Digester Conversion to Mixing/Holding Tanks

Project Overview

Ribway was selected by the Metropolitan Sewer District of Greater Cincinnati (MSD) as the prime consultant to provide engineering design services for a $12 million solids handling and improvement project at the 430 MGD Mill Creek Wastewater Treatment Plant (WWTP). This project, part of the Solids Handling Phase I Improvements, involved converting existing anaerobic digesters into sludge holding tanks (SHTs) and enhancing the plant’s solids handling capabilities.

Scope of Work

Design and Planning Services:

• Field investigations and surveys.
• Preparation of a comprehensive Design Report, including evaluations, recommendations, and cost estimates.
• Detailed design engineering and development of plans and specifications for construction.
• Execution of an asbestos and hazardous material survey, geotechnical studies, and environmental soils investigations.

Proposed Improvements:

• Demolition:
  • Removal of eight (8) anaerobic digesters, four (4) digester control buildings, waste gas burners, and associated digestion equipment.
  • Partial demolition to approximately 12 feet below grade.
• Conversion:
  • Repurposing four (4) existing digesters into sludge holding tanks equipped with:
    • Fixed aluminum geodesic dome covers.
    • Submersible mixing systems.
• Sludge Transfer Systems:
  • Installation of two (2) sludge transfer pumps for each holding tank to convey sludge to dewatering wells.
• Building Renovations:
  • Comprehensive updates to two (2) four-story digester control buildings, including new roofing, doors, windows, railings, and concrete and masonry repairs.
  • New heating and ventilation systems.
• Electrical Upgrades:
  • Construction of a new Electrical Room housing multiple motor control centers (MCCs) and power distribution equipment.
  • Installation of interior and exterior lighting and process equipment power systems.
• Automation:
  • Full process automation using a programmable logic controller (PLC) system.

Project Challenges

• Coordination of complex demolition and conversion processes for deeply buried structures.
• Integration of modern mechanical, electrical, and automation systems with existing infrastructure.

Timeline

• Design Completion: Project design services were completed.
• Construction Status: The project was not constructed due to funding limitations.

Project Impact

Although the project was not constructed, the design addressed key operational needs, including enhanced sludge handling, improved facility automation, and the modernization of infrastructure to support future plant operations.