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Aeration Basin & Blower Procedures


Treatment Aeration - Aeration Basins 1-4, Aeration Blowers 1-3, Aeration Flow Control Valves
Process Flow Diagrams Process Plan and Section Diagrams
Plant Schematic Aeration Basin Process Plan
Aeration Basins Liquid Flow Aeration Basin Process Section
Aeration Basin Air Flow



Aeration Basin Operating Procedures

The Aeration Basin Anoxic Mixers are operated in either a remote manual mode or local manual mode. Process air flow to the aeration basin system is either automatically or manually adjusted using any of the following four operating modes: dissolved-oxygen control, dosage control, remote manual control, and local manual control.

An important limitation for the aeration basin is to limit the differential head across each baffle wall (difference in water surface elevation across each baffle wall) to less than 6-inches. Each FRP baffle wall is designed for only 30 psf (pound per square foot) which is approximately 6 inches of differential across the wall.
Aeration Basins Anoxic Control Modes
MODE DESCRIPTION
Remote - Manual Each Aeration Basin Anoxic Mixer’s START-STOP control is available through the PCS.
Local - Manual The Aeration Basin Anoxic Mixer is manually operated through the MCC in the Blower Building.
   
Aeration Basins Process Air Control Modes
MODE DESCRIPTION
Dissolved Oxygen Control Mode The Aeration Basin air flow is automatically adjusted to maintain an operator-entered aeration basin dissolved oxygen set point.
The dosage set point is adjusted to maintain the dissolved oxygen set point.
Dosage Control Mode The Aeration Basin air flow is automatically adjusted to maintain an operator-entered dosage set point (scfm/mgd).
The Aeration Basin flow control set point(s) is automatically adjusted in response to changes in the plant influent flow rate. 
Remote Manual Mode The Aeration Basin air flow control valve position is manually adjusted through the PCS.
Local Manual Mode  The Aeration Basin air flow control valve position is manually adjusted locally.


Aeration Basin Startup Procedures
Dissolved Oxygen Control Mode

Dosage Control Mode

Remote Manual Mode

Local Manual Mode
 
Aeration Basin Shutdown Procedures
Remote Manual Mode

Local Manual Mode

Aeration Basin Additional Control Features
Under average flow conditions, air flow to the three aerobic zones per aeration basin should be split approximately as shown below. A minimum of 320 scfm needs to be maintained for each zone to keep the mixed liquor in suspension.

Automated dropleg control valves have been supplied to adjust and maintain this process air flow split to each aeration basin zone. Permanent thermal mass flowmeters are installed on each drop leg to measure air flow rate.
 
 
 
Aeration Blower Operating Procedures

The Aeration Blowers inlet air flow is either automatically or manually adjusted using any of the following four operating modes: remote pressure control, remote flow control, remote manual control, and local manual control as shown in the table below.

Aeration Blowers Control Modes
MODE DESCRIPTION
Remote Manual Mode Each Aeration Basin Blower's START-STOP control is available through the PCS.
Local Manual Mode The Aeration Blower is manually operated through the local control panels in the Blower Building.
   
Aeration Blowers Air Flow Control Modes
MODE DESCRIPTION
Remote Pressure Control Mode The Aeration Blower inlet air flow is automatically adjusted through the PCS to maintain an operator-set header pressure set point.
The air flow set point is adjusted to maintain the header pressure set point.
Remote Motor Current Control Mode The Aeration Blower inlet air flow is automatically adjusted through the PCS to maintain an operator-set motor current set point.
Remote Manual Control Mode The Aeration Blower inlet air flow control valve position is manually adjusted through the PCS.
Local Manual Mode The Aeration Blower inlet air flow control valve position is manually adjusted from the Blower Local Control Panel.
Blowoff valve control  
During low flow periods, the amount of air produced by the blower system is in excess of the demand in the aeration basins. In order to prevent excessive DO concentrations during these periods, a blowoff system is operated to maintain a header pressure setpoint and DO setpoint. When the process air demand decreases, the blower inlet valve closes to maintain the setpoint header pressure. The blower inlet valves have a maximum closure position to prevent surge. When the valve has reached this position and the header pressure is still above the setpoint, the blowoff valve will open to 10%. If this still does not achieve the setpoint header pressure, the blowoff valve will incrementally open until the setpoint header pressure is achieved. The blowoff valve is located at the end of the air supply distribution system, downstream of all process air branches on the system.


Blower Startup Procedures
Remote Pressure Control Mode

Remote Flow Control Mode

Remote Manual Control Mode

Local Manual Control Mode
 
Blower Shutdown Procedures
Remote Control Mode:
Through the PCS, initiate an Aeration Blower STOP command.
Local Manual Control Mode:
Initiate an Aeration Blower STOP command from the local control panel.

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Last Updated: 9/16/2013 9:19:51 AM
Version 4.0.1