Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OI;' THE INVl-~.N'rION
lhe current public interest in pollution control
has created the need for surveilance and monitoring of en-
vironmental conditions particularly related to plant effluent,
waterways, sewers, lakes and rivers. The acquisition of ac-
curate and reliable data regarding water quality as affected
by industrial wastes, treatment plant effluent, meterological
and other factors is necessary for effecting enforcement of
standards for pollution control, as well as for analysis
and planning.
Automated water quality monitoring systems include
monitors at field stations connected by telemetry to a cen-
tral control data receiving station and rely on the use of
automatic unattended measurement procedures operated on a
continuous basis, or intermittently, at a predetermined fre-
quency. Sophisticated instrumentation for automatically ana-
lyzing physical and chemical parameters, such as pH, conduc-
tivity, temperature, dissolved oxygen, chlorides and turbidity
of plant effluent and waterways have been utilized in the
art. It is recognized that instrument reliability is adversely
affected by the fouling of the sampling system or malfunc-
tion of the analyzer components that are continously exposed
to polluted water. Heavy build-up of slime, algae or par-
ticulate matter on the sensing probes, which may comprise
solid state or liquid membrane electrodes, and on the surface
areas confining the water surrounding the probes, with re-
sulting stagnation of flow deleteriously affects the
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sensitivity of the probes resulting in inaccurate measurements
or measurement failure.
In order to obtain reliable data it has been found
necessary to clean the sensing probes manually at frequent pe-
riodic intervals, preferably, at least daily. Monitoring
stations which are remotely located at substantial distances
from a central receiving station must be visited daily by service
personnel to effect manual cleaning of the probes and associated
apparatus. This requires extensive travel, as well as a sub-
stantial expenditure of labor by the service personnel, andrepresents a significant cost in the maintenance of monitoring
stations in the system under consideration. It also has been
found that manual removal or displacement of the sensing probes
from the monitoring apparatus for manual cleaning disturbs the
stability of the calibration resulting in unreliable data.
SUMMARY OF THE IN'ilENTIO~
The present invention relates to a method utilizing
ultrasonic energy in combination with centrifuge means for
automatically cleaning the sensing probes and associated ap-
paratus of water quality monitoring apparatus so as to maintainthe same in clean condition for maximum sensitivity and relia-
bility, in order to obtain accurate data for effective enforce-
ment of environmental pollution control standards.
The use of ultrasonic electrode cleaning apparatus
is known. Typical of such apparatus is the EIL Ultrasonic
Electrode Cleaner, Model U 28, manufactured by Cambridge Instru-
ment Co., Inc. of Great Britain.
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The use of centrifuge apparatus for removing settleable
solids or particulate matter from liquids is known. Typical of
such apparatus is the Bauer Centri-Cleaner* Liquld Cyclone No.
600-3 manufactured by Bauer Brothers Co., of Springfield, Ohio.
Another is the Vulcan Hydro-Clone V 20*, manufactured by Vulcan
Laboratories, Inc. of Pontiac, Michigan.
Insofar as is known to me ultrasonic energy and centri-
fuge action have never been used, in combination, for cleaning
the sensing probes and associated apparatus of water quality
monitoring systems. I have found that the use of a centrifuge
for removing particulate matter or settleable solids, such as
sand, grit, stones etc., from the effluent or water to be tested,
before it contacts the sensing probes, reduces the likelihood ~
injury to the sensing probes and also results in a very marked re-
duction in over-all build-up of objectionable materials on the
surfaces of the probes and associated apparatus, so that sub-
sequent cleaning of the probes and associated apparatus by
ultrasonic energy is highly efficient.
The removal of particulate matter or settleable solids
from the water before the water contacts the sensing probes is
highly desirable in all monitoring situations involving the use
of sensing probes, and particularly, in situations involving the`
use of glass electrodes of pH measurements and liquid membrane
electrodes for measuring dissolved oxygen. Particulate matter
has abrasive characteristics and would tend to erode the elec-
trodes. In the case of liquid membrane electrodes, the use of
very thin Teflon* membranes is desirable for obtaining maximum
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* Trade Mark
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sensitivity to dissolved oxygen changes. Such membranes are
fragile and would be subject to excessive degradation if re-
quired to withstand the quality of ultrasonic energy necessary
by itself for cleaning the probes of normal build-up of algae,
slime etc., and also settleablematerial incorporated in the
build-up. Obviously, in such cases thicker and less sensitive
membranes would need to be used to withstand the rigors of
such ultrasonic energy for long periods. By reason of the use
of a centrifuge, the settleable material is removed before it
has an opportunity to contact the membranes and, as a result,
the sensing probes require shorter intervals of th~ applicatlon
of ultrasonic energy to effect cleansing of the probes. This
allows the use of thinner membranes with greater sensitivity
of measurement. In a series of comparative tests conducted
over a period of several months it was found with the uti-
lization of conventional cleaning practices, with resultant
clogging in the sensing zones, that the deviation of measure-
ments from the true value ranged from 1 to 2 parts per million.
With the use of my invention the deviation was reduced to 0.22
parts per million, a figure which is within the tolerance of
0.25 parts per million established for an accurate system. In
the case of stagnant flow, without cleaning, the deviation
could be as high as l0 parts per million.
Broadly stated, my invention is defined a~ a mathod
for cleaning a sensing probe in a liquid quality monitoring
system which comprises the steps of: continuously removing
particulate matter from a sample stream of liquid containing
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the same by centrifugation in a closed vessel under pressure;
moving a portion of the liquid from the vessel into a recep-
tacle having an associated ultrasonic transducer, the receptacle
surrounding the probe; and applying ultrasonic energy to the re-
ceptacle to substantially remove deposits of foreign matter from
the surface of the probe and the receptacle.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is the schematic representation of a spe-
cific embodiment of my invention.
BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to the drawing, there is diagrammatically
shown a field station 10 which includes functional components
such as an automatic monitor 11 and utilities, all conventional
and well known in the art.
Each monitor 11 comprises a flow chamber module 12 which
includes an influent pipe 13, a plurality of stainless steel sen-
sor cones or funnels 14, preferably six in number, an overflow
drain 16 and individual sensor probes 17 inserted in respective
funnels 14 and having
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associated leads and plugs, not shown. Each monitor 11 also
includes an analyzer module 18 in which the electronic signals
from the sensor probes 17 are converted to a linear output, am-
plified to the necessary output voltage and displayed on indica-
ting meters 19. The monitor 11 also includes a telemetry module
21 connected to the central receiving station or control center,
not shown. The utilities include electric and telephone services
and the necessary pumps and piping. The central station re-
ceives data from each monitoring station at periodic intervals
in accordance with a predetermined program.
The foregoing components are conventional and from no
part of the present invention.
In accordance with my invention I provide each monitor
11 with a fourth module constituting an ultrasonic generator 22
connected by cables 25 to transducers 23 associated with each of
the funnels 14 in the flow chamber module 12~ This module in-
cludes timing apparatus for controlling the operation of the
ultrasonic generator 22. The generator may comprise any well
known type, for example, Model U28, EIL Ultrasonic Electrode
Cleaner manufactured by Cambridge Instrument Company, Inc., and
the transducer funnels 14, 23 may comprise either the flow type
or dip types, examples of which are Models EIL No. 47 2843 300
and EIL No. 47 2843 400, respectively, both also manufactured by
Cambridge Instrument Company, Inc. of Great Britain.
Desirably, the ultrasonic generator 22 should have the
camability of operating a multiple number of transducers 23 se-
quentially with a power output of approximately 100 watts and a
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frequcncy output of approximately ~0.0 kilohertz. The timing
apparatus, not shown, associated with the generator 22 includes
two timers, the first, for sequentially applying a manually pre-
set interval of ultrasonic power to each transducer 23 for the
total cleaning cycle of the multiple sensing probes and the se-
cond, for starting and stopping the cleaning cycle and energizing :
and de-energizing an associate relay, not shown, which functions
to transmit a signal to the central receiving station, indicat-
ing that the ultrasonic cleaning is in process. This signal
is employed in the data acquisition apparatus to notify the cen-
tral station that the data being transmitted by the monitor 11
to the receiving station during the ultrasonic cleaning interval
is unreliable and should be rejected by the data processing
equipment.
The delivery of water to the flow chamber 12 from a
stream, waterway or plant effluent being monitored is effected
by any suitable pump means, if the required pressure is not avail-
able. The pump may be of the displacement or submer.sible type,
or both, if the conditions require. For illustrative purposes .
the drawing shows a submersible pump 24 connected in ser.es with
a secondary or booster pump 26, the latter being connected to
the inlet of a centrifuge 27 of any suitable type for example,
a Hydro-Clone* separator, Model No. V50, manufactured by Vulcan
Laboratories, Inc. of Pontiac, Michigan or a Bauer Centri-Clea-
ner* Liquid Cyclone, manufactured by the Bauer Brothers of
Springfield, Ohio.
*Trade Mark
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In the centrifuge 27 the solids and particulate mat-
ter accumulate in a bottom reservoir for easy separation and
disposal and the clean liquid discharged from the centrifuge
is conducted by conduit 28 to the transducer funnels 14,23 in
the flow chamber 12. The liquid in each funnel 14 completely
surrounds a probe 17 associated therewith. The centrifuge 27
operates continuously to remove particulate matter from the
water so that all of the water coming in contact with the sen-
sing probes 17 and the surfaces of the funnels is free of such
matter. This not only reduces the likelihood of erosion of the
sensing probes 17 but also reduces clogging and stagnation of
flow in the funnels 14 and results in a very marked reduction
in overall build-up of any objectionable materials on the sen-
sing probes 17 and on the surfaces of the funnels 14. Thus,
whatever build-up may occur is more effectively removed by the
ultrasonic energy to which the probes 17 and funnel surfaces
are subjected during the cleaning cycles. It will be under-
stood that a modified form of apparatus may comprise a plura-
lity of sensing probes associated with a single transducer fun-
nel of sufficient size to encompass the plurality of probes.In such case the probes would be cleaned simultaneously and
not sequentially.
The cleaning intervals in which the sensing probes
17 are subjected to ultrasonic energy may be varied depending
upon the types and characters of the probes being cleanedO
have found, for example, in most cases, that subjecting an in-
dividual probe to ultrasonic energy for an interval of 5-1
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minutes, in a 2~ hour peri~ is-adequate to cleanse tile probe
and the funnel to maintain the same in clean condition for
maximum sensitivity and accuracy. The application of ultra-
sonic energy for longer intervals would tend to degrade the
probe. The timing apparatus in each generator module 22 auto-
matically programs the sequential application of ultrasonic
energy to the probes 17 in each flow module 12. After the clean-
ing intervals, the data transmitted to the central receiving
station has sustained accuracy and reliabilty.
The automatic cleaning of the sensing probes 17 with
minimum disturbance, in accordance with my invention, very
materially reduces the frequency of service required to maintain
the probes and funnels at optimum operating conditions. Thus,
the intervals between visits by service personnel for manual
examination, cleaning and calibration of the probes may be ex-
tended to once in every three to four week period, instead of
daily visits, as in current practices. Also, the use of prior
art devices and procedures for cleansing the probes which
included the use of filters, dilution methods, periodic chemical
cleaning, jet water spray and mechanical wipes are eliminated
through the use of my invention.
It will be understood that apparatus for obtaining a
composite sample of water for laboratory analysis or turbidity
measurement by a turbidimeter may be installed upstream of the
centrifuge 27.
Various changes coming within the spirit of my in-
vention may suggest themselves to those skilled in the art;
hence, I do not wish to be limited to the specific embodiments
shown and described or uses mentioned, but intend the same to
be merely exemplary, the scope of my invention being limited
only by the appended claims.
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