U.S. patent number RE28,940 [Application Number 05/449,487] was granted by the patent office on 1976-08-24 for method and apparatus for agglomeration measuring and control.
This patent grant is currently assigned to Komline-Sanderson Engineering Corporation. Invention is credited to Thomas R. Komline, Sr., deceased, Walter R. Wills.
United States Patent |
RE28,940 |
Komline, Sr., deceased , et
al. |
August 24, 1976 |
Method and apparatus for agglomeration measuring and control
Abstract
The apparatus extracts samples of a fluid stream containing
colloidal suspended solids at a detection station wherein the
electrophoretic mobility (EM) of the colloidal suspended solids is
determined. The detection station automatically measures the EM and
provides such data to a computer, which computes the Zeta
Potential. The computer also receives other information relating to
the characteristics of the colloidal suspended solids, such as
temperature, the percent of solids, and the flow rate of the fluid
system. The computer is programmed to interpret the input data and
to provide corrective signals to processing apparatus which
automatically adjust and control the additives fed into the fluid
stream to achieve automatic flocculation correction so that the
agglomeration of the colloidal suspended solids in the fluid stream
is optimized.
Inventors: |
Komline, Sr., deceased; Thomas
R. (late of Gladstone, NJ), Wills; Walter R. (Cedar
Knolls, NJ) |
Assignee: |
Komline-Sanderson Engineering
Corporation (Peapack, NJ)
|
Family
ID: |
26884161 |
Appl.
No.: |
05/449,487 |
Filed: |
March 8, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
188516 |
Oct 12, 1971 |
03723712 |
Mar 27, 1973 |
|
|
Current U.S.
Class: |
204/549; 204/400;
210/85; 324/109; 204/645; 702/25; 73/61.64; 324/92; 702/130;
702/55; 348/142 |
Current CPC
Class: |
G01N
27/447 (20130101) |
Current International
Class: |
G01N
27/447 (20060101); G06F 015/46 (); G01N 021/28 ();
G01N 033/16 () |
Field of
Search: |
;73/61.4
;204/149,195R,195B,299 ;210/85,91 ;235/151.31 ;324/92,109 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dildine, Jr.; R. Stephen
Attorney, Agent or Firm: Watson, Cole, Grindle &
Watson
Claims
What is claimed is:
1. A method for determining the Zeta Potential of suspended
colloidal particles comprising the steps of:
a. establishing a predetermined voltage gradient along an
electrophoresis cell positioned on a microscope stage,
b. introducing a sample of said suspended colloidal particles into
said cell,
c. scanning a microscopic image of said colloidal particles within
said cell,
d. tracking said particles to determine their movement,
e. storing data representative of said particle movement;
f. calculating the particle velocity from said data, and
g. determining the Zeta potential from said particle velocity, the
voltage gradient of said cell, and the temperature of said
suspended colloidal particles sample.
2. A method as in claim 1 wherein said particle velocity is
determined from the total distance travelled by the individual
particles and dividing said total distance by the number of
particles observed during a fixed observation period.
3. The method as in claim 1 wherein said particle velocity is
determined by differentiating a signal representative of said
particle displacement with respect to time to provide a signal
proportional to the rate of change of particle displacement.
4. A method as in claim 1 wherein the Zeta Potential is determined
from the following formula:
Zp= -k.sub.1 (v.sub.e /V) (1.45-0.02t.sub.c) and wherein K.sub.1 =
4.pi.Ln/D,
V.sub.e is the electrophoretic velocity of said particles,
V is the voltage across said cell, t.sub.c is the temperature of
said sample, L is the length of said cell, D is the dielectric
constant of said sample, and n is the viscosity of said sample.
5. A method as in claim 1 wherein the Zeta Potential is determined
from the following formula:
Zp=-k.sub.2 (d/V) (1.45-0.02t.sub.c) wherein K.sub.2 = 4.pi.Ln/D, d
is the distance travelled during a predetermined observation
interval, V is the voltage of said cell, t.sub.c is the temperature
of said sample, L is the length of said cell, n is the viscosity of
said sample and D is the dielectric constant of said sample and
where K.sub.2 includes said predetermined observation interval.
6. A method as in claim 1 wherein the Zeta Potential is determined
from the following formula:
Zp=(k.sub.3 /tv) (1.45-0.02t.sub.c) wherein -K.sub.3 = 4.pi.Ln/D, T
is the average time required for the particles to travel a
predetermined distance, V is the voltage across said cell, and
t.sub.c is the temperature of said sample, L is the length of said
cell, n is the viscosity of said sample and D is the dielectric
constant of said sample and wherein K.sub.3 includes said
predetermined distance. .Iadd. 7. A method for determining the Zeta
potential of suspended colloidal particles comprising the steps
of:
a. establishing a pedetermined voltage gradient along an
electrophoresis cell,
b. introducing a sample of said suspended colloidal particles into
said cell,
c. tracking said particles to determine their movement during a
fixed tracking period,
d. storing the data representative of said particle movement;
e. calculating the particle velocity from the movement of said
particles by the total distance travelled by the individual
particles and dividing said total distance by the number of
particles observed during said fixed tracking period, and
f. determining the Zeta potential from said particle velocity, the
voltage gradient of said cell, and the temperature of said
suspended colloidal particles sample. .Iaddend..Iadd. 8. A method
as in claim 7 further comprising the step of scanning said
particles before said step of tracking. .Iaddend. .Iadd. 9. A
method as in claim 7 wherein the Zeta Potential is determined from
the following formula:
ZP=-K.sub.1 (V.sub.e /V) (1.45 - 0.02t.sub.c) and wherein K.sub.1
=4.pi. Ln/D, V.sub.e is the electrophoretic velocity of said
particles, V is the voltage across said cell, t.sub.c is the
temperature of said sample, L is the length of said cell, D is the
dielectric constant of said sample, and n is the viscosity of said
sample. .Iaddend..Iadd. 10. A method as in claim 7 wherein the Zeta
Potential is determined from the following formula:
ZP=-K.sub.2 (d/V) (1.45-0.02t.sub.c) wherein K.sub.2 =4.pi.Ln/D, d
is the distance travelled during a predetermined observation
interval, V is the voltage of said cell, t.sub.c is the temperature
of said sample, L is the length of said cell, n is the viscosity of
said sample and D is the dielectric constant of said sample and
where K.sub.2 includes said predetermined observation interval.
.Iaddend..Iadd. 11. A method as in claim 7 wherein the Zeta
Potential is determined from the following formula:
ZP=(-K.sub.3 /TV) (1.45-0.02t.sub.c) wherein K.sub.3 =4.pi.Ln/D, T
is the average time required for the particles to travel a
predetermined distance, V is the voltage across said cell, and
t.sub.c is the temperature of said sample, L is the length of said
cell, n is the viscosity of said sample and D is the dielectric
constant of said sample and wherein K.sub.3 includes said
predetermined distance. .Iaddend..Iadd. 12. Apparatus for
determining the Zeta Potential of suspended colloidal particles
from a sample of said suspended colloidal particles wherein the
temperature thereof is known, comprising:
means for establishing a predetermined voltage gradient along an
electrophoresis cell;
means for introducing said sample into said cell;
means for tracking said particles for determining their movement
within said cell during a fixed tracking period;
means for storing data representative of the particle movement;
means for calculating the particle velocity from the movement of
the particles determined by said means for tracking; and
means for determining the Zeta Potential from said particle
velocity by determining the total distance travelled by the
individual particles within said sample and by dividing said total
distance by the number of particles tracked during said tracking
period, the voltage gradient of said cell and the temperature of
said suspended colloidal particles sample. .Iaddend. .Iadd. 13.
Apparatus as in claim 12 wherein said means for determining the
Zeta Potential includes means for differentiating a signal
representative of the displacement of said particles with respect
to time for providing a signal proportional to the rate of change
of particle displacement to said means for determining.
.Iaddend..Iadd. 14. Apparatus as in claim 12 wherein the Zeta
Potential is determined from the following formula:
ZP=-K.sub.1 (V.sub.e /V) (1.45-0.02t.sub.c) and wherein K.sub.1
=4.pi.Ln/D, V.sub.e is the electrophoretic velocity of said
particles, V is the voltage across said cell, t.sub.c is the
temperature of said sample, L is the length of said cell, D is the
dielectric constant of said sample, and n is the viscosity of said
sample. .Iaddend..Iadd. 15. Apparatus as in claim 12 wherein the
Zeta Potential is determined from the following formula:
ZP=-K.sub.2 (d/V) (1.45-0.02t.sub.c) wherein K.sub.2 =4.pi. Ln/D, d
is the distance travelled during a predetermined observation
interval, V is the voltage of said cell, t.sub.c is the temperature
of said sample, L is the length of said cell, n is the viscosity of
said sample and D is the dielectric constant of said sample and
where K.sub.2 includes said predetermined observation interval.
.Iaddend. .Iadd. 16. Apparatus as in claim 12 wherein the Zeta
Potential is determined from the following formula:
ZP=(-K.sub.3 /TV) (1.45-0.02t.sub.c) wherein K.sub.3 =4.pi.Ln/D, T
is the average time required for the particles to travel a
predetermined distance, V is the voltage across said cell, and
t.sub.c is the temperature of said sample, L is the length of said
cell, n is the viscosity of said sample and D is the dielectric
constant of said sample and wherein K.sub.3 includes said
predetermined distance. .Iaddend. .Iadd. 17. A method for
determining the Zeta potential of suspended colloidal particles
comprising the steps of:
a. establishing a predetermined voltage gradient along an
electrophoresis cell;
b. introducing a sample of said suspended colloidal particles into
said cell;
c. tracking said particles to determine their movement;
d. calculating the particle velocity from the movement of said
particles by differentiating a signal representative of said
particle displacement with respect to time to provide a signal
proportional to the rate of change of particle displacement;
and
e. determining the Zeta potential from said particle velocity, the
voltage gradient of said cell, and the temperature of said
suspended colloidal particles sample. .Iaddend.
Description
This invention relates to methods for optimizing conglomeration of
any fluid stream containing colloidal suspended solids and, more
particularly, to a method determining the Zeta Potential of
colloidal suspended solids from their electrophoretic mobility and
a method for the continuous analysis and selection of correction
measures in accordance with the Zeta Potential to automatically
control and select the additives fed into the process or stream to
achieve an optimized agglomeration.
The method of the invention determines the Zeta Potential of
colloidal suspended particles or aggregates of colloidal suspended
particles in a fluid stream. The diameter of the particles and
aggregates of interest is, in most cases, in the range of one to 50
microns. It is well known that particles of activated sludge or
untreated, raw sewage possess an electric charge that can be
accurately determined in an electrophoresis cell. It is also
recognized that the mechanics of measurement for concentrated
suspensions differ somewhat from the standard methods employed for
the measurement of Zeta Potential of dilute colloidal suspensions.
That is, if a sludge is too dense to be viewed optically in an
electrophoresis cell, it may be necessary to treat the sludge in
some way to make it less dense so that optical detection of the
articles is possible.
A dense sludge can be viewed optically by first separating the
liquid phase from the solid and then returning a small portion of
the solid to a large portion of the liquid to give a suspended
solids concentration of about 100 parts per million. The
liquid-solids separation may be achieved by filtration,
centrifugation, or any other method which does not alter the
electrolytic composition of the liquid phase. Simple dilution with
water from another source in most cases changes the electrolytic
balance and as a result the Zeta Potential is also changed.
The invention provides methods for sampling any fluid stream
containing colloidal suspended solids and detecting the
electrophoretic mobility of the suspended solids. Information
relating to the motion of the suspended particles is converted into
electrical signals and fed to a suitably programmed computer which
determines the velocity of the particles, and in conjunction with
other information relating to the characteristics of the suspended
solids, such as the percentage of sludge and the rate of flow of
the fluid stream, generates appropriate control signals which are
then fed to corrective apparatus for altering the addition of
additives into the process of stream to optimize the agglomeration
of the colloidal suspended solids. The methods disclosed herein are
particularly suitable for water and sewage treatment plants,
industrial waste treatment, industrial solids recovery and/or other
industrial process applications.
OBJECTS
It is a primary object of this invention to provide methods for the
automatic optimization of agglomeration or stabilization in any
fluid stream containing colloidal suspended solids.
It is a second object of this invention to provide methods for
automatically determining the Zeta Potential of suspended solids in
a fluid stream from a determination of the electrophoretic mobility
of the suspended solids.
A third object of the invention is to provide greatly improved
methods for automatically determining the electrophoretic mobility
of colloidal suspended solids in any fluid stream.
A fourth object of the invention is to provide improved automatic
and more versatile control of the agglomeration or stabilization of
any fluid stream containing colloidal suspended solids.
.Iadd.A fifth object of the invention is to provide apparatus for
automatically determining the Zeta Potential of suspended solids in
a fluid stream from a determination of the electrophoretic mobility
of the suspended solids.
A sixth object of the invention is to provide improved apparatus
for automatically determining the electrophoretic mobility of
colloidal suspended solids in any fluid stream.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1a is a combined block and diagrammatic illustration of an
embodiment of a measuring and agglomeration control system in
accordance with the invention; and
FIG. 1b illustrates a preferred embodiment of the control system
disclosed in FIG. 1a.
DETAILED DESCRIPTION OF THE INVENTION
Influent (sludge) is pumped into flocculation tank 10 where it is
treated by suitable flocculents from flocculent storage tanks 12 by
means of flocculent feed pumps 14 which are controlled by computer
signals on line 16 to alter the flocculent pumped into the
flocculation tank. The conditioned sludge is pumped from
flocculation tank 10 via sampling port 20 to be pumped into
electrophoresis cell 22. The unsampled sludge is pumped to settling
or flotation equipment (not shown). Provision is made for diluting
sludge from flocculation tank 10 with water to improve the optical
density of the sludge so that the colloidal suspended solids
therein may be optically viewed or tracked in electrophoresis cell
22. For this purpose as well as to purge the electrophoresis cell,
clean water flush 24 is provided.
Lens system 28 magnifies the colloidal motion sufficiently so as to
produce an image which is scanned by an electro-optical scanner or
tracker 32. Scanner 32 is essentially a photomultiplier tube with
servo circuitry for locking onto and tracking a dark or a light
spot and providing displacement data thereof in both X and
Y-directions. The displacement data is converted by velocity module
34 into rate of displacement and produces signals proportional to
dx/dt and dy/dt. The rate of displacement data in turn is fed to
programmed computer 36 and combined with the voltage of
electrophoresis cell 22 and sample temperature data respectively
from cell voltage module 34a and temperature module 34b to compute
the Zeta Potential. A waste stream flow rate signal is fed from
flow rate sensor 35 to proportional plus reset ratio controller 38
which delivers a signal to proportional plus reset cascade
controller 40. The ZP signal from computer 36 is also fed to
cascade controller 40 and the resultant control signal regulates
the speed of pumps 14 by means of pump controls 39.
Scanner 32 may comprise a series 800 Electro-Optical Motion tracker
as manufactured by the Optron Corporation. Electrophoresis cell 22
is positioned on the stage of a microscope and the optical head of
the tracker is positioned to receive the magnified image. The
output of tracker 32 is an analog voltage of .+-.5 volts and is
proportional to the displacement of a tracked object or objects
along the X or Y-axis, or both axes simultaneously. Velocity module
34 may simply comprise a differentiating circuit to generate a
signal representing the differentiation of the tracker output
voltage. The differentiated signals are stored in computer 36. The
computer calculates an average velocity from the stored data and
then calculates the corresponding Zeta Potential from an equation
described below.
FIG. 1b illustrates a preferred embodiment of scanning and tracker
apparatus 32 for measuring the velocity of particle migration
within the electrophoresis cell. In this embodiment the scanner
comprises the .pi.MC particle measurement computer manufactured my
Millipore, a subsidiary of Bausch and Lomb. As in the
aforedescribed embodiment, electrophoresis cell 22 is placed on the
stage of a microscope 28 and the magnified image is scanned by
video scanner 44, which is part of the .pi.MC system. A computer
associated with video scanner 44 identifies each particle and
locates its position from the coordinates of the tangent of the
lower portion of the particle. The particle location coordinates
are stored in computer 36. An average velocity determination is
made by determining the total distance travelled by the particles
divided by the total number of particles divided by the time
interval between observations. The computer associated with video
scanner 44 already has the capability of performing division and
multiplication. Therefore, it can be programmed to determine
particle velocity and supply such data to computer 36 wherein the
Zeta Potential for the suspended particles is calculated. The flow
rate and Zeta Potential signals are processed by controllers 38 and
40 as in FIG. 1a to produce control signals for pumps 14.
THE DERIVATION OF THE WORKING EQUATIONS FOR DETERMINING ZETA
POTENTIAL
The classical expression for electroosmotic velocity of a fluid
caused by a voltage gradient is:
where: v.sub.e =electroosmotic velocity, D=dielectric constant of
the medium, E=electric field strength, ZP=zeta potential,
n=viscosity of the medium. The above equation can be used to
determine Zeta Potential by rewriting it as follows:
In this equation E, the field strength, is replaced by V/L, the
voltage divided by the distance between the electrodes. In all our
work we have taken 22.5.degree.C as our reference temperature and
all Zeta Potential measurements are corrected to 22.5.degree.. In
this way the ZP equation becomes:
where n is the viscosity at 22.5.degree. and c is a correction
factor for the change of viscosity with temperature. Now the
equation is in a form that can be used by a computer to
automatically determine ZP on the basis of three input signals,
particle velocity (electroosmotic velocity), cell voltage, and
temperature. In the case of the first embodiment, the particle
velocity signal will be analog and proportional to velocity so the
basic ZP equation will be:
where: K.sub.1 = 4.pi.Ln/D, so K.sub.1 is a function of the cell
dimensions and the time and distance units used in the
equation.
With the second and preferred embodiment, there are two choices of
signal proportional to velocity (1) the average distance travelled
by the particles in a predetermined time or (2) the average time
required for the particles to travel a predetermined distance. The
equations for calculating ZP in these two cases are as follows:
where d is the average distance travelled and the predetermined
time is included in the constant K.sub.2.
where T is the average time required for the particles to travel.
The predetermined distance is included in the constant K.sub.3.
DETERMINING THE PROPER SET POINT ZETA POTENTIAL FOR OPTIMUM
AGGLOMERATION
Most suspensions of particles that are to be agglomerated for
settling or flotation have an average Zeta Potential of -25 to -50
millivolts. This means that there is a fairly strong negative
charge on each individual particle that repels any other
approaching particles. It has been found that when the Zeta
Potential is less than -20mv, there is a much stronger tendency for
particles to agglomerate. When the Zeta Potential of a suspension
is between -10 and -15mv, the suspension is said to be at the
threshold of agglomeration, but its tendency to agglomerate depends
on the individual suspension properties and the type of agitation
given to it. The actual Zeta Potential at which agglomeration
begins, if this indeed occurs at a sharp point, must be determined
empirically for each suspension. Strong agglomeration and
precipitation occur in the Zeta Potential range of -5 to +5 mv. As
the Zeta Potential increases in the positive direction, the
repelling forces again increase and the tendency to agglomerate
drops off.
The average charge on the particles is a function of the surface
properties of the particle material and the amount and type of
dissolved substances in the suspension, and it is the result of
preferential adsorption of anions around the solid particles and
solvation of cations by the water molecules.
Most commonly used flocculents owe their effectiveness to the their
ability to alter the charge on suspended particles by adding a
surplus of positively charged cations to the suspension. The
positive charges neutralize the existing negative charges and cause
the Zeta Potential to approach zero. However, in most cases, it is
a waste of flocculent to bring the Zeta Potential to zero. Some of
the best known flocculants are compounds containing ferric ions
such as FeCl.sub.3, compounds containing aluminum ions such as
Al.sub.2 (SO.sub.4).sub.3 and AlCl.sub.3, and various cationic
polyelectrolytes such as Dow Purifloc C31 and Rohm and Haas C7.
With automatic and continuous monitoring of Zeta Potential and
control of the rate of flocculent addition based on a set point
Zeta Potential, the minimum amount of flocculent is consumed to
achieve the maximum benefit. In general, the set point for
agglomeration control is -11 mv, but this is flexible to allow for
unusual conditions.
* * * * *