The DeKalb Sanitary District’s Facility Plan Update recommended a phased approach for rehabilitation and upgrade of the existing facility. Phase 1A focused on rehabilitation and upgrade of the District’s biosolids facilities.

The existing plant is rated for a DAF of 8.63 MGD and a PHF of 18 MGD with a PWWF of 55 MGD. The existing biosolids facilities included four 55-foot diameter anaerobic digesters and a 40-foot diameter sludge storage tank. At that time, the District had abandoned the sludge drying beds and relied solely on decanting back to the plant and liquid hauling biosolids seasonally. The decanting operations negatively impacted the District’s treatment capabilities within the biological process.

The sludge storage tank was originally constructed in 1928 and had served as the original anaerobic digester. The District had constructed one of the 55-foot digesters in 1955, another in 1963, and the third and fourth in 1982. TAI performed a thorough evaluation of the system and determined that while the mechanical components were beyond their service life, all of thestructures could be rehabilitated and reused for the proposed improvements.

Phase 1A included rehab and upgrade of the existing digesters, construction of an operations building, sludge handling building (thickening and dewatering), an off-site dewatered sludge storage barn, and miscellaneous piping improvements. Trotter and Associates, Inc. designed, permitted, and worked through the ARRA funding process to finance this $18.5 Million dollar project. Construction was completed in 2010.

2012 APWA Environmental Project of the Year

Technical Challenges & Solutions

  • Reuse of Infrastructure – Structural rehab/modification to meet current code
  • Elimination of Recycle Flows – Upgraded Dewatering Operations
  • Continuation of Operations – Sequenced Construction/ Rehabilitation
  • Digester Efficiency – Upgrade to complete mix/ heat
  • Operational Efficiency – Methane Gas Utilization


Chris Marschinke, P.E.