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Effluent Pumping System Overview
Purpose
The effluent pumping system pumps the effluent from the new wastewater treatment facility back to the existing wastewater treatment facility for discharge to the Mississippi River.
Theory of Operation
The effluent pumps will pump flows from 2 MGD to 17 MGD from the the new wastewater treatment plant to the existing flood pump station at the CSO facility.  Four identical pumps are used to pump the effluent through a 24" force main.  The Effluent Pump Station also contains the nonpotable water pumps that supply nonpotable water to all facilities at the new wastewater treatment plant site.
Equipment
The Effluent Pumping system includes the following equipment: 
  • Effluent pumps
  • Effluent pump variable frequency drives (VFD's) 
  • Effluent flow monitoring
  • Effluent surge relief valve
  • Effluent sampling 
  • Nonpotable water pumps
  • Nonpotable water strainers
  • Nonpotable water booster pumps 
  • Nonpotable water flow meter
Description
Secondary effluent flow is monitored with a long throated flume as it enters the Effluent Pump Station wet well.  The four effluent pumps are vertical turbine solids handling units that extend into the wet well.  The pumps are variable speed pumps and are controlled based on the wet well level.  Effluent flow is discharged through a 24" forcemain running from the Effluent Pump Station to the effluent trough of the Flood Pump Station located at the existing wastewater treatment facility.
 
Nonpotable water is pumped from the Effluent Pump Station wet well by two vertical turbine pumps.  The flow from the nonpotable water pumps is directed through strainers before leaving the pump station through a 6" line.  A magnetic flow meter monitors the flow of nonpotable water.  The difference between the secondary effluent flow and the nonpotable water flow produces the total effluent flow.
 
A portion of the flow from the strainers provides the suction for the nonpotable water booster pumps.  These pumps boost the pressure to provide seal and flush water for the effluent pumps.
 
An automatic composite sampler collects effluent samples for effluent compliance monitoring.
Effluent Pumps6
   The four effluent pumps are located in the Effluent Pump Station of the new wastewater treatment facility.  These units pump the treated effluent from the secondary clarifiers through a 24" forcemain back to the existing wastewater treatment facility for discharge to the Mississippi River.  The pumps are controlled based on the level in the effluent wet well.
Effluent Pump VFD's 6
  Each effluent pump is equipped with a variable frequency drive which allows for adjustment of the pump speed.  The pump discharge rate is proportional to the pump speed so that as the pump speed is increased, the pump discharge rate also increases. 
Effluent Flow Monitoring6
Effluent flow is monitored using two flow meters, one for the secondary clarifier effluent entering the effluent wet well and the other on the discharge line from the nonpotable water pumps.  The net effluent flow is calculated by subtracting the nonpotable water flow from the secondary clarifier effluent flow. 
Effluent Surge Relief Valve6
A 12" surge relief valve on the 24" effluent forcemain protects the pipeline and pumping equipment from pressure surges that may occur during pumping operations.  The valve opens rapidly at the setpoint pressure and discharges flow from the forcemain back to the effluent wet well.  After pressure returns to normal, the valve slowly closes. 
Effluent Sampling Equipment 6
A refrigerated automatic sampler is located in the Effluent Pump Station to collect samples of the effluent from the new wastewater treatment facility.  Flow out of the Effluent Pump Station is sent to the automatic sampler for flow-paced sampling.  The effluent samples collected by the sampler are analyzed to determine compliance with the NPDES permit for the facility.
Nonpotable Water Pumps   6
The two nonpotable water pumps are vertical turbine units that extend into the Effluent Pump Station wet well.  The pumps are controlled based on the level in the hydropneumatic tank, located in the Dewatering Building.
Nonpotable Water Strainers   6
The two automatic strainers remove particles greater than 50 microns from the nonpotable water. The discharge from the nonpotable water pumps flows into the filter body and through the stainless steel coarse filter element (10,000 micron) outside in, keeping large debris from entering the fine screen.  Once water flows through the coarse screen, it enters the stainless steel fine filter element inside out, allowing particles to accumulate on the inside surface of the element.  A differential pressure switch senses the pressure differential across the filter as material builds up on the fine screen.  The control system for the screen initiates a cleaning cylce when the differential pressure reaches 7 psi.
Nonpotable Water Booster Pumps   6
The nonpotable water booster pumps increase the pressure of the nonpotable water for use as seal and flush water in the effluent pumps.
Nonpotable Water Flow Meter   6
A magnetic flow meter monitors the nonpotable water flow leaving the Effluent Pump Station.  This flow is substracted from the secondary effluent flow to establish the final effluent flow.
 

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Last Updated: 5/9/2013 11:22:08 AM
Version 3.0.1