Hubbell, Roth & Clark, Inc. (HRC) recently completed an upgrade and expansion of the City of South Lyon wastewater treatment plant from a capacity of 1.5 MGD to 2.5 MGD.

The project planning process for the City of South Lyon was complicated by discussion and negotiation with the Michigan Department of Environmental Quality regarding a proposed reduction in phosphorus limitations.   The new limitations will reduce the phosphorus discharge from the current 0.3 mg/l to between 0.03 mg/l to 0.10 mg/l.  The project includes replacement of the rotating biological contactors (RBC) with a new extended aeration activated sludge treatment system.

The plant uses a new ballasted flocculation system in which ferric chloride, polymer, and microsand are added to coagulate the phosphorus and settle the floc using much smaller clarifiers.   This unique system is the first application for this technology in Michigan.   The system is installed in an existing filter building thus saving the capital that would have been required for a new building.

The existing fixed film biological system (RBCs) was replaced with a new innovative activated sludge system which will be much easier to maintain and control.  The existing RBC building was renovated for use as a storage and vehicle maintenance facility.  Other major plant modifications included the addition of a fine screenings system, new solids dewatering, aerobic digestion, solids storage, and ultraviolet disinfection.