Plant and control method for aerobic treatment

Patent metadata

Field	Value
Publication number	US-10287196-B2
Application number	US-201515122801-A
Country	US
Kind code	B2
Filing date	Feb 24, 2015
Priority date	Mar 4, 2014
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A treatment plant and a method for controlling such a treatment plant suitable for treatment of waste water. The treatment plant includes a circulation channel adapted to house a liquid, an aeration arrangement adapted to supply a gas flow Q including oxygen to the liquid, at least one flow generating machine arranged in the circulation channel and adapted to generate a liquid flow along the circulation channel, and a control unit.

First claim

The invention claimed is:

1. A method for controlling a treatment plant for treating liquid, the treatment plant comprising (i) a circulation channel adapted to house a liquid, (ii) an aeration arrangement adapted to supply a gas flow Q comprising oxygen to the liquid, and (iii) at least one flow generating machine arranged in the circulation channel and adapted to generate a liquid flow along the circulation channel, the at least one flow generating machine comprising a submersible mixer machine, the method comprising the steps of:
providing a gas flow Q to the liquid via the aeration arrangement,
operating the flow generating machine at an operational speed f to generate a liquid flow having a flow rate v along the circulation channel,
measuring at least one process parameter at at least one location in the circulation channel, which process parameter, directly or indirectly, provides an indication of a dissolved oxygen concentration of the liquid in the treatment plant,
comparing the measured value of said at least one process parameter with a set value, and
adjusting the dissolved oxygen concentration of the liquid in the treatment plant responsive to a difference between the measured value of the process parameter and the set value by adjusting the gas flow Q provided by the aeration arrangement, adjusting the operational speed f of the flow generating machine and thereby the flow rate v of the liquid, or a combination thereof, to guide the measured value of said at least one process parameter towards said set value,
wherein a relationship between the operational speed f of the flow generating machine and the gas flow Q provided by the aeration arrangement, at a time the value of said at least one process parameter is equal to the set value, is determined by the formula:

f

f
0

=

(

a
*

(

Q

Q
0

)

b

+
1
-
a

)

where Q 0 is equal to maximum gas flow,
f 0 is equal to the operational speed of the flow generating machine at maximum gas flow Q 0 , and
a and b are constants dependent on prerequisites of the treatment plant, including one or more of an intended liquid level in the circulation channel, a location of the aeration arrangement in the circulation channel, a capacity of the flow generating machine, a location of the flow generating machine in the circulation channel, an efficiency of the aeration arrangement, an efficiency of the flow generating machine, and a required range of the dissolved oxygen concentration in the liquid.

2. The method according to claim 1 , wherein the method comprises the steps of:
measuring a power consumption PC A for the aeration arrangement for providing said gas flow Q to the liquid,
measuring a power consumption PC M for the flow generating machine at said operational speed f, and
adjusting the gas flow Q provided by the aeration arrangement and the operational speed f of the flow generating machine to minimize a sum of the power consumption PC A of the aeration arrangement and the power consumption PC M of the flow generating machine, simultaneously with guiding the measured value of said at least one process parameter towards the set value.

3. A method for controlling a treatment plant for treating liquid, the treatment plant comprising (i) a circulation channel adapted to house a liquid, (ii) an aeration arrangement adapted to supply a gas flow Q comprising oxygen to the liquid, and (iii) at least one flow generating machine arranged in the circulation channel and adapted to generate a liquid flow along the circulation channel, the at least one flow generating machine comprising a submersible mixer machine, the method comprising the steps of:
providing a gas flow Q to the liquid via the aeration arrangement,
operating the flow generating machine at an operational speed f to generate a liquid flow having a flow rate v along the circulation channel,
measuring at least one process parameter at at least one location in the circulation channel, which process parameter, directly or indirectly, provides an indication of a dissolved oxygen concentration of the liquid in the treatment plant,
comparing the measured value of said at least one process parameter with a set value, and
adjusting the dissolved oxygen concentration of the liquid in the treatment plant responsive to a difference between the measured value of the process parameter and the set value by adjusting the gas flow Q provided by the aeration arrangement, adjusting the operational speed f of the flow generating machine and thereby the flow rate v of the liquid, or a combination thereof, to guide the measured value of said at least one process parameter towards said set value,
wherein the operational speed f of the flow generating machine is determined by a table having predetermined pairs of quotients C i and d i and based on the gas flow Q provided by the aeration arrangement using the relationship:
f/f 0 =d i when c i-1 <Q/Q 0 <c i
given than c i <1 and c i >c i-1

where Q 0 is equal to maximum gas flow,
f 0 is equal to the operational speed f of the flow generating machine at maximum gas flow Q 0 ,
i is a positive integer, and
C i and d i are quotients dependent on prerequisites of the treatment plant, including one or more of an intended liquid level in the circulation channel, a location of the aeration arrangement in the circulation channel, a capacity of the flow generating machine, a location of the flow generating machine in the circulation channel, an efficiency of the aeration arrangement, an efficiency of the flow generating machine, and a required range of the dissolved oxygen concentration in the liquid.

4. The method according to claim 1 , wherein the treatment plant comprises a sensor for measuring the dissolved oxygen concentration in the liquid.

5. The method according to claim 4 , wherein the sensor is an oxygen sensor and the aeration arrangement comprises at least one aeration sector arranged in the circulation channel, the oxygen sensor being located in connection with a terminal end of the aeration sector relative to a flow direction of the liquid flow along the circulation channel.

6. The method according to claim 1 , wherein the operational speed f of the flow generating machine is higher than a predetermined lowest allowed operational speed f min .

7. The method according to claim 1 , wherein the operational speed f of the flow generating machine is lower than a predetermined highest allowed operational speed f max .

8. The method according to claim 1 , wherein the aeration arrangement comprises at least one aeration sector arranged in the circulation channel.

9. The method according to claim 8 , wherein the aeration arrangement comprises at least one blowing machine connected to and supplying pressurized gas to the aeration sector.

10. The method according to c

Assignees

• Xylem Ip Man Sarl

Inventors

• Uby Lars

Classifications

• C02F3/1257 Primary

  Oxidation ditches · CPC title

• C02F3/303

  characterised by the nitrification · CPC title

• C02F3/006 Primary

  Regulation methods for biological treatment · CPC title

• C02F2209/006

  comprising a software program or a logic diagram · CPC title

• C02F2209/001

  Upstream control, i.e. monitoring for predictive control · CPC title