PChem Plant Information
The PChem plant is located in the Village of Sauget, Illinois.
The plant is a physical-chemical plant which provides preliminary
and primary treatment for industries located in the Village of
Sauget and operates 24 hours per day, 365 days per year. The plant
was originally constructed in 1942 and has had many additions of
treatment equipment and processes to the plant over the years.
When the American Bottoms plant opened in 1986, the PChem
plant began conveying its treated water to American Bottoms for
secondary biological activated sludge treatment. The primary goals
of the treatment process at PChem are to neutralize the pH, to
remove metals, to remove oil, and to prepare the wastewater for
secondary treatment at American Bottoms. The PChem plant also
contains a hauled wastewater discharge facility where approved
hauled wastewater streams can be discharged for treatment.
from the industries and storm drains through a system of pipes to a
pump station located at the PChem facility. The PChem plant can
process flow rates of 26 million gallons per day through the
plant. The process begins with the removal of large trash and
debris from the wastestream. Two industrial grade screens,
called barscreens, catch the trash and debris consisting of things
like cans, bottles, plastic bags, lawn clippings, and all the
things you might see in the gutters along the streets. The PChem
bar screens are manually raked to pull the debris and trash from
the screen into a trough located at the top of the screen.
The trash and debris are then shoveled into a hopper and
dumped into a dumpster for disposal at a landfill.
Once the large trash and debris are removed, all floating oil is
removed by nine oil skimming units made up of two belt skimmers and
seven rope skimmers. The oil is picked up by the skimmers and
captured in a day tank. It is then pumped to a storage tank
where any excess water picked up with the oil is allowed to
separate to be returned back to the process. Once this tank
is full, the oil is transferred to a final storage tank where it is
tested prior to disposal. After screening and oil removal, the
water is conveyed to the neutralization process by pumps.
The final stage of the preliminary treatment process is the
neutralization process. The waste stream entering the PChem
facility typically has a pH less than 3. Due to the extremely
low pH of the influent wastewater, large quantities of lime must be
added to achieve the optimum pH level of 8.3. An average of
248 dry tons of lime per month is used at the PChem treatment
facility. Dry lime is mixed with water in a very reactive process
called slaking to form a lime slurry. PChem contains
two lime slakers and two lime silos for storing dry lime. The lime
slurry is added in a series of three completely mixed tanks to
adjust the pH of the incoming wastewater.
Neutralizing the wastewater ensures that it is no longer
corrosive. This protects the equipment further down the
treatment process. The addition of lime and the increase
of pH will also allow the dissolved metals in the wastewater to
precipitate out in the primary treatment process.
Neutralization is also required to ensure no upsets occur in the
biological process at American Bottoms during secondary
The wastewater has now completed the various stages of
preliminary treatment and is ready for primary treatment at
PChem Primary Treatment:
Primary treatment at PChem starts by adding a liquid chemical
called polymer to the wastewater stream prior to entering the
flocculation process. The purpose of the liquid polymer is to
aid in the flocculation of the solids in the wastewater.
Flocculation is the formation of clumps of solids, or "flocs", in
the wastewater. Once the polymer is added, the water flows
into a flocculation chamber which contains three slowly rotating
paddle mixers. The mixers slowly mix the wastewater and
polymer encouraging the flocs to form.
The heavily flocculated water then enters a set of rectangular
tanks called clarifiers. The primary purpose of the
clarifiers at PChem is to settle out heavy solids, including the
metals contained in the wastewater. The wastewater flows into one
end and flows out over v-notched weirs at the opposite end.
As the water travels across the clarifier, the heavy solids fall to
the bottom. A traveling bridge pushes these solids to sludge pits
at the end of the clarifiers.
The solids pushed into the sludge pits by the traveling bridge
are generally very thick. There is an agitator in each of the
pits which is used to gently stir the water and sludge, causing the
sludge to fall down the sloped walls and into the sludge
pits. The sludge is pumped from the pits to the sludge
handling process at PChem.
During heavy storms our PChem plant can become overloaded.
When this happens, we have a large storage tank called the storm
water basin which holds this excess wastewater until the flows
return to normal levels. All water stored in the tank is returned
back through the plant for treatment.
The water flowing over the weirs of the rectangular clarifier
pass through a flow measuring device called a parshall flume.
The amount of water leaving the plant is measured by this
structure. Samples of the effluent water are also taken at this
location and monitored by the plant's certified laboratory to
ensure compliance. The plant also has the capability of adding
sodium hydrosulfide at this location to combine with any excess
metals to prevent an upset in the secondary biological process at
American Bottoms. The water leaving the flume structure flows
through a 42 inch sewer to the American Bottoms plant for secondary
treatment. The water is pumped into the American Bottoms plant by
three screw pumps.
Sludge is pumped from the clarifier sludge pits to a storage
tank. The sludge is then pumped from this tank to a belt
filter press at PChem. Polymer is mixed into the sludge as it
is being pumped to the press to help the water separate from the
solids. The polymer conditioned sludge passes through a single
belt filter press where it is squeezed to remove as much water as
possible. Pressure is applied as the sludge is squeezed between
belts. This pushes water from the sludge. The dewatered
sludge, also called filter cake, is removed from the belt with
scrapers where it falls to a conveyor and is conveyed directly to a
dumpster that is hauled to a landfill.
The PChem plant has the capability to accept approved hauled
wastewater discharges. Although the plant can't accept hazardous
waste, it can take high or low pH wastewaters, oily wastewaters,
metal-bearing wastewaters, and more due to the treatment processes
and capabilities of the facility. For more information on the
hauled wastewater program, please see the hauled waste section of
this web site.
Every one of our employees knows that treating wastewater is our
primary responsibility for the protection of our nation's water
resources both today and for future generations. The PChem plant is
a critical component for providing beneficial services for our
industrial customers in a cost effective manner and for providing a
high quality wastewater effluent at the American Bottoms Regional
details on the PChem Plant process