On January 1, 2008, GBMSD took over operations of
the De Pere wastewater treatment facility. GBMSD's De Pere
Facility services our southern service area, primarily the
City of De Pere, parts of the Village of Ashwaubenon, and parts of
the Towns of Lawrence, Belleuve, and Hobart.
The De Pere wastewater treatment facility was built in 1976 and
over the years has received a number of upgrades to keep up with
demand and to replace outdated equipment. The average flow received
at the facility is 8 million gallons per day (mdg). The
maximum design flow for the facility is 14.2 mgd, with a maximum
wet design flow of 30 mgd.
As the wastewater enters the facility, it passes through fine
screening devices that are able to remove trash, rags, and other
debris at least a 1/4" in size. The material collected is washed,
compacted, and sent to a landfill for disposal.
After the wastewater passes through the fine screening devices,
the water is conveyed to the next treatment point by large
centrifugal pumps. The wastewater is forced under pressure to the
Preliminary Treatment Units for further processing.
As wastewater flows through the preliminary treatment Units, the
flow speed is slowed to one foot per second, allowing sand and
other coarse material to settle to the bottom.
The settled material is removed, washed, and disposed of in a
landfill. The oil and grease that rises to the surface is skimmed
off the top of the tank for further processing.
After the wastewater passes through the PTUs, it flows through
an anoxic zone for biological phosphorus removal. In this phase,
the bacteria will consume the phosphorus before the wastewater
enters the aeration tanks.
From the anoxic zone, the wastewater moves to the aeration tanks
where an abundant supply of oxygen is added through fine bubble
diffusers. Now, the bacteria have an ideal environment to multiply
and consume the organic material in the wastewater. The wastewater
will remain in the aeration tanks for 6 to 8 hours.
Following aeration, the wastewater is again slowed to allow the
bacteria to settle to the bottom and be captured and pumped back to
the aeration basins to be reused (return activated sludge) or sent
on to be either incinerated or landfilled (waste activated sludge).
The De Pere Facility operates two intermediate clarifiers.
The wastewater from the intermediate
clarifiers flows to the final clarifiers where further settling
occurs. At this point, about 85% to 90% of the pollutants are
removed. The De Pere Facility has three final clarifiers, however
only one is needed for operation at a time.
The wastewater from the final clarifiers goes through a gravity
filter process where it passes through a filtering media, capturing
the remaining suspended solids.
Before entering the environment, the wastewater goes through a
disinfection process to kill remaining bacteria. The De Pere
facility uses an ultraviolet light disinfection system that is
capable of treating 15 mgd. The liquid chlorine treatment process
that was used prior to 1997, is still retained and used during
periods of high flow.
Solids from the De Pere Facility are pumped through an
interplant pipeline to the Green Bay Facility for
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