The St. Louis Wastewater Plant was originally constructed in
1954 as a primary treatment plant.
Expansions to the plant occurred in 1978-80 and again in 1998-2001. These expansions and upgrades resulted in the
plant to be a state of the art, tertiary-biological-chemical-sand filter
system. In 2014, the City needed to
further upgrade the plant and received a loan from the State Revolving Loan
fund to switch the treatment process from RBCs (rotating biological contactors)
to oxidation ditches. When completed in
2015-16, the upgraded wastewater plant provides primary, secondary, and
tertiary treatment consisting of a fine screen with vortex grit removal,
pre-aeration ahead of the primary clarifiers followed by anaerobic selector
basin, oxidation ditches, final clarifiers chlorination, a holding pond and
sand filters. All biosolids pass through
anerobic digestion and are stored on site prior to land application.
The plant is designed to treat a maximum of 4.0 MGD (million
gallons per day) with an average day flow of 1.6 MGD. In 2018 the wastewater plant treated
453,434,000 gallons of sewage resulting in an average day flow of 1.2433
MGD. A portion of this sewage flow
consists of infiltration and inflow (I & I) into the sewer lines through
illegal connections, such as storm inlets, sump pumps, footing and downspout
connections as well as cracks and failed joints due to the age of the sewer
lines. A reduction in these sources of
storm drainage and groundwater into the sanitary sewer pipes has been an
ongoing process with City maintenance personnel and construction projects. The City must continue to locate and remove
these sources of I & I to reduce the impacts of the periodic high flows on
the wastewater plant and its treatment ability.
The City wastewater treatment plant and collection system
includes five pump stations which transmit flows from Pine River and Bethany
Townships (two stations), two of the correctional facilities located east of
the City (one station), and two stations within the City which collects and
transports sewage to the plant. As part
of the recent Asset Management Plan, three of the pump stations are being
considered for replacement over the next few years.