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American Water Enterprises
3100 South Lewis Blvd, RR6
Sioux City, IA 51106
Phone - 712-279-6916
Fax - 712-279-6191
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Septage and Trucked-in Material
The City receives septage form Siouxland only. The septage suitable for
disposal at the wastewater plant is compatible with the wastewater treatement
plant and is received at the headworks through a Special Waste Authorization
Permit issued by the City of Sioux City Environmental Services Department.
Primary Treatment
Raw wastewater enters the WWTP and passes through a bar screen where large
solids are removed. The wastewater then flows through two grit removal basins,
and thereafter receives primary treatment in the primary clarifiers. The
clarifiers are equipped with continuous chain and flight sludge collectors and
primary sludge pumps. Primary sludge is pumped to the primary sludge digesters.
Floating scum is skimmed from the primary clarifiers and flows to the scum
pumping station, where it is pumped to the primary sludge digesters.
Secondary Treatment
Primary clarifier effluent is pumped to the activated sludge tanks by four
primary effluent pumps. Oxygen transfer in the secondary aeration tanks is
accomplished by the use of synthetic membrane diffusers. Centrifugal blowers
supply air to the membrane diffusers. Following aeration, the activated sludge
passes through the secondary clarifiers, where the sludge is settled out. Three
return activated sludge pumps recycle the activated sludge from the secondary
clarifiers back to the aeration tanks. Waste activated sludge is directed to the
gravity belt thickeners. The secondary clarifiers also contain scum removal
equipment. Overflow from the secondary clarifiers is discharged to the chlorine
contact basins for disinfection before discharge to the Missouri River.
Disinfection System
Wastewater is disinfected in two chlorine contact chambers prior to
discharge. Chlorine gas is used as the disinfection agent. The disinfected
effluent is discharged in the Missouri River. Disinfection occurs seasonally
from April through September.
Solids Handling and Treatment
Waste activated sludge (WAS) from the secondary clarifiers is pumped by two
WAS pumps to the gravity belt thickeners. The thickened sludge is then pumped to
the anaerobic digesters. There are two anaerobic digester complexes; each
complex contains two primary and two secondary digesters.
Following digestion, the stabilized sludge is pumped to the sludge storage
lagoons. The sludge is stored in the lagoons on a seasonal basis; it is hauled
and applied to farmland after fall crop harvest.
Methane gas is produced by the anaerobic digesters. A portion of the methane gas
is used within the WWTP as fuel for building heat and for the boilers that serve
the sludge heat exchangers. The excess gas is scrubbed of particulates and
compressed, and sold to the local gas utility. The methane gas line is a 3” high
pressure line that was replaced in 1995 (Buy/Sell Line).
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