Process Aeration Balance Controller in Wastewater Treatment

Patent metadata

Field	Value
Publication number	US-2020299162-A1
Application number	US-202016824469-A
Country	US
Kind code	A1
Filing date	Mar 19, 2020
Priority date	Mar 19, 2019
Publication date	Sep 24, 2020
Grant date	—

Abstract

An aeration balance controller in a wastewater treatment process allows for precise control of aeration medium in situations where the oxygen concentration must be controlled in more than one aeration zone or compartment, with reduced instrumentation. The system also has application controlling aeration media where the aeration of one or more zones may interfere with the stable control of aeration in another zone. This is accomplished by the use of two control schemes: one which determines the overall aeration effort required, and one or more controllers which adjust the balance between zones to equalize the process error from setpoint from zone to zone.

First claim

I claim:

1 . An aeration control system for a wastewater treatment tank or basin having a plurality of zones each requiring aeration at a preselected dissolved oxygen (DO) level, and wherein a change in DO level in one zone can affect DO level in a downstream zone, comprising:
an air supply, and an air duct through which aeration air is supplied for all of the plurality of zones, a downstream header receiving aeration air from the air duct for supply to each of the plurality of zones, a DO sensor at each zone, producing a wastewater DO level signal, a comparitor connected to the DO sensor of each zone, for comparing DO level of each zone to a set point DO level for the zone, to produce an error signal for each zone, each error signal being a positive value, a negative value or zero, a controller receiving error signals of the zones and for adjusting aeration via a flow valve in one or more of the zones to move DO of the zones toward balance of the plurality of the zones to essentially equal errors from set point DO in the respective zones, and averaging means for computing an average of the DO error signals for the plurality of zones at a given time, to produce an average zone DO error signal for the plurality of zones, and an overall air flow controller receiving the average DO error signal and for increasing or decreasing total air flow to all zones, i.e. to the downstream header serving the plurality of zones, whereby the system allows for precise control of aeration in multiple zones, by balancing aeration deviations from set point in a plurality of zones, and separately by adjusting total flow delivered from the air supply based on total aeration requirements of all zones as determined from average deviation of all zones from their respective DO set points.

2 . The aeration control system of claim 1 , the plurality of zones comprising two zones and the controller having means for calculating a difference between the error signals of the two zones, then adjusting aeration in at least one of the two zones to essentially equalize error from set point in the two zones.

3 . The aeration control system of claim 1 , wherein the wastewater treatment tank or basin is an oxidation ditch.

4 . A method for controlling aeration air flow in a wastewater treatment system having a plurality of zones with sludge requiring aeration at preselected dissolved oxygen (DO) levels and wherein a change in DO level in one zone can affect DO level in a downstream zone, comprising:
monitoring dissolved oxygen within the sludge of each of the plurality of zones, and comparing DO at each zone to a set point desired DO level for the zone, to calculate a positive or negative deviation from set point at each zone, calculating an increase or decrease in aeration needed for one or more of the zones to equalize deviations from set point of all zones, increasing or decreasing aeration at the one or more zones to substantially equalize deviations such that all zones are in balance by essentially equal deviations even if not on set point, averaging the deviations from set point of the plurality of zones, and increasing or decreasing total air flow to the plurality of zones as needed to reduce the average deviation essentially to zero, bringing the DO of each zone essentially to set point.

5 . An aeration control system for a wastewater treatment tank or basin having a plurality of zones each requiring aeration at a preselected dissolved oxygen (DO) level, comprising:
a low speed surface aerator in each zone, a DO sensor at each zone, producing a wastewater DO level signal, a comparitor connected to the DO sensor of each zone, for comparing DO level of each zone to a set point DO level for the zone, to produce an error signal for each zone, each error signal being a positive value, a negative value or zero, a controller receiving error signals of the zones and for adjusting aeration via a speed control on each low speed surface aerator to move DO of the zones toward balance of the plurality of the zones to essentially equal errors from set point DO in the respective zones, and averaging means for computing an average of the DO error signals for the plurality of zones at a given time, to produce an average zone DO error signal for the plurality of zones, and an overall aeration controller receiving the average DO error signal and for increasing or decreasing total aeration flow to all zones, by proportionally increasing or decreasing speed of the surface aerators in all zones, whereby the system allows for precise control of aeration in multiple zones that can have effect on one another, by substantially equalizing aeration zones from set point in a plurality of zones, and in addition by adjusting the overall level of aeration in all zones as determined from average error of all zones from their respective DO set points.

6 . The aeration control system of claim 5 , the plurality of zones comprising two zones and the controller having means for calculating a difference between the error signals of the two zones, then adjusting aeration in at least one of the two zones to essentially equalize error from set point in the two zones.

7 . The aeration control system of claim 5 , wherein the wastewater treatment tank or basin is an oxidation ditch.

Assignees

• Ovivo Inc

Inventors

• Robertson Calvin

Classifications

• Y02W10/10

  Biological treatment of water, waste water, or sewage · CPC title

• C02F2209/005

  Processes using a programmable logic controller [PLC] · CPC title

• C02F3/1257

  Oxidation ditches · CPC title

• C02F2209/22

  O2 · CPC title

• C02F3/006 Primary

  Regulation methods for biological treatment · CPC title