Method and device for monitoring and controlling the state of a process stream

Patent metadata

Field	Value
Publication number	US-9970919-B2
Application number	US-201214362135-A
Country	US
Kind code	B2
Filing date	Nov 30, 2012
Priority date	Dec 2, 2011
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

The present invention concerns a method of estimating and optionally controlling the microbiological state in a process stream of an industrial process by measuring the concentration of dissolved oxygen or the rH value, or both, in said stream, the method including continuous or periodic sampling and online measurement. The invention also concerns a device suitable for use in implementing said method.

First claim

The invention claimed is:

1. A method of monitoring a microbiological state of a process stream by measuring concentration of dissolved oxygen and determining a rH value in said stream, wherein the rH value is determined by measuring a pH and a redox potential of a sample of the process stream and by calculating the rH value by adding the measured pH and redox potential of the sample together, modified by constants, the method comprising
providing a process stream originating from said process;
conducting a sample of the process stream to a measuring unit;
carrying out initial measurements of the concentration of dissolved oxygen and the rH value in the measuring unit at the beginning of the measurement of the concentration of dissolved oxygen and the determination of the rH value, and determining whether process stream has aerobic or anaerobic conditions;
measuring, in the measuring unit, at two or more time points, the concentration of dissolved oxygen in the sample and calculating relative dissolved oxygen consumption if the process stream has aerobic conditions between the two of said two or more time points;
determining, in the measuring unit, at least at two time points, which may be the same or different than the at least two time points for measuring the concentration of dissolved oxygen, the rH value of the sample and calculating at least one of change of the rH value and relative change of the rH value if the process stream has anaerobic conditions between said at least two time points;
determining the microbiological state of the process stream, based on one or more of the rH value, the change of the rH value and the relative change of the rH value if the process stream has anaerobic conditions, and determining the microbiological state of the process stream, based on relative dissolved oxygen consumption and optionally based on the rH value if the process stream has aerobic conditions;
correlating the relative dissolved oxygen consumption and optionally the rH value to the amount of aerobic bacteria in the process stream, and correlating one or more of the rH value, the change of the rH value and the relative change of the rH value to the amount of anaerobic bacteria in the process stream;
the method further comprising controlling the microbiological state of the process stream by adding an amount of biocide(s) to the process stream based on results of the correlating the relative dissolved oxygen consumption and optionally the rH value to the amount of aerobic bacteria in the process stream, and correlating one or more of the rH value, the change of the rH value and the relative change of the rH value to the amount of anaerobic bacteria in the process stream.

2. The method according to claim 1 , wherein the process stream is an industrial stream.

3. The method according to claim 1 , wherein a temperature of the sample of the process stream and a pressure in the measuring unit are measured.

4. The method according to claim 1 , wherein the measurement of the concentration of dissolved oxygen or the determining of the rH value, or both, is carried out at constant pressure, or at constant temperature, or with both the temperature and the pressure being constant.

5. The method according to claim 1 , wherein the process stream has aerobic conditions if the concentration of dissolved oxygen is higher than about 0 mg/l, the process stream had anaerobic conditions if the concentration of dissolved oxygen is about 0 mg/l.

6. The method according to claim 1 , wherein the step of determining the microbiological state of the process stream includes calculations using the following equation for the relative dissolved oxygen consumption:

Δ
⁢

⁢
DO
⁢

⁢
%

=

100
⁢

%
·

O
2

⁢

(

t
1

)

-

O
2

⁡

(

t
2

)

O
2

⁡

(

t
2

)

(
2
)

where O 2 (t 1 ) is a first value of the concentration of dissolved oxygen, and O 2 (t 2 ) is a second value of the concentration of dissolved oxygen,
and optionally the following equations for the rH values:
rH= 2* pH+ 2* Eh*F /( c·R·T )  (3),

wherein F=Faraday constant 9.64853399(24)×10 4 Cmol −1 , c=ln 10, T=temperature (K), Eh=redox potential measured with standard hydrogen electrode, and R=universal gas constant 8.314472(15) JK −1 mol −1 ,

Δ
⁢

⁢
rH

=

rH
⁡

(

t
1

)

-

rH
⁡

(

t
2

Assignees

• Kemira Oyj

Inventors

• Ilmola Pekka
• Jansson Kaj
• Joensuu Iiris
• Piironen Marjatta

Classifications

• G01N33/1806

  Biological oxygen demand [BOD] or chemical oxygen demand [COD] · CPC title

• G01N33/343 Primary

  Paper pulp · CPC title

• C12M1/3461

  Bio- or chemi-luminescence · CPC title

• G01N33/1826 Primary

  Organic contamination in water · CPC title

• G01N33/48735

  Investigating suspensions of cells, e.g. measuring microbe concentration (by chemical means C12Q1/04; colony counters C12M1/34; concentration of particle suspensions in general G01N15/06) · CPC title