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United States Patent [i9] [ii] 4,06i,S70
Fletcher et al. [45] Dec. 6, 1977
[54] IODINE GENERATOR FOR RECLAIMED
WATER PURinCATION
[76] Inventors: James C. Fletcher, Administrator of
the National Aeronautics and Space
Aministraton, with respect to an
invention of; Richard A. Wynveen,
Pepper Pike; James D. Powell,
Euclid; Franz H, Schuhert, Mentor,
all of Ohio
[21]
Appl. No.;
571,459
[22]
Filed;
Apr. 25, 1975
[51]
Ini, C1.2 ....
BOIJ 1/06; BOIJ 4/02;
GOIN 21/02; GOIN 33/18
[52]
U.S. a
210/96 M; 210/192;
204/180 P; 204/301; 23/253 A
[58]
Field of Search 23/253 A; 210/62, 64,
210/96, 192; 204/180 P, 301
[56]
References Cited
U.S. PATENT DOCUMENTS
3,288,708
3,351,542
3,464,555
3,528,545
11/1966 Cordle et al
11/1967 Oldershaw et al.
9/1969 Schneider
9/1970 Frazel et al
210/62
210/62
210/96
210/96
3,554,905 1/1971 Place et al 210/62
3,574,084 4/1971 Bruce 210/62
3,669,857 6/1972 Kirkham et al 204/180 P
3,755,134 8/1973 Francis et al 204/180 P
Primary Examiner — Morris O. Wolk
Assistant Examiner — Bradley Garris
Attorney, Agent, or Firm — Carl O. McClenny; John R.
Manning; Marvin F. Matthews
[57] ABSTRACT
The system disclosed is for controlling the iodine level
in a water supply in a spacecraft. The system iodinates
drinking water as necessary. It includes an iodine accu-
mulator which stores crystalline iodine, an electro-
chemical valve to control the input of iodine to the
drinking water and an iodine dispenser. A pump dis-
penses fluid through the iodine dispenser and an iodine
sensor to a potable water tank storage. The iodine sen-
sor electronically detects the iodine level in the water,
and through electronic means, produces a correction
current control. The correction current control oper-
ates the electro-chemical iodine valve to release iodine
from the iodine accumulator into the iodine dispenser.
7 Claims, 3 Drawing Figures
lOd
4,061,570
IODINE GENERATOR FOR RECLAIMED WATER
PURIFICATION
, ORIGIN OF THE INVENTION
The invention described herein was made in the per-
formance of work under a NASA Contract and is sub-
ject to the provisions of Section 305 of the National
Aeronautics and Space Act of 1958, Public Law 85-568
(72 Statute 435; 42 U.S.C. 2456).
FIELD OF THE INVENTION
This invention relates to systems for controlling the
iodine level in the water supply for a spacecraft. More
particularly, this system relates to an electro-chemical IS
iodine valve which can be operated by an electrical
current in response to detection of iodine levels in the
water supply to inject additional iodine into the water
system in precise and controlled amounts to maintain a
preset residual concentration of iodine in the water 20
supply.
BACKGROUND OF THE INVENTION
In a spacecraft as well as other situations where mi-
cro-organism control of drinking water is desired, io- 25
dine is a suitable agent. Iodine has several notable char-
acteristic advantages as a micro-organism control and is
effective against a broad spectrum of organisms. Ordi-
narily, in a spacecraft operation, it is desirable to main-
tain low weight requirement and low electrical power 30
consumption. In this invention the valve operates at 10
mWatts and 5 ma. The spacecraft uses recycled water.
The iodine system is superior to pasteurization on the
basis of wei^t, volume, cost and power consumption.
SUMMARY OF THE INVENTION
The system for iodination of water includes a potable
water storage tank. Water is circulated by a pump to the
storage tank through a dispenser chamber which has an
iodine valve. From the dispenser chamber, the water 40
passes through an iodine sensor to the potable water
storage tank. The iodine sensor detects the level of
iodine concentration in the water and produces in re-
sponse thereto electrical signals. The electrical signals
are sampled and passed to an error amplifter which 45
determines if the iodine level is below a predetermined
or preset value. If an error signal is produced, a corre-
sponding current is passed through the electro-chemical
iodine valve to pass iodine into the water by ion ex-
change. 50
The electro-chemical iodine valve includes an anion
exchange membrane. An anode and cathode are respec-
tively disposed on opposite sides of the membrane. On
one side of the membrane a slurry of water and I 2 crys-
tals are stored. On the other side of the membrane, the 55
water supply circulates past the membrane in the dis-
penser chamber. An electrical current between the
anode and cathode causes iodine to transfer from one
side of the membrane to the other side of the membrane.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a thematic illustration of the system em-
bodying the present invention;
FIG. 2 is a schematic illustration of an I 2 sensor for.
the system; and 65
FIG. 3 is a view in cross-section through an iodinat-
ing device embodying the principles of the present in-
vention.
DESCRIPTION OF THE PREFERRED
. EMBODIMENT
One type of system is illustrated in FIG. 1. Conduits
10(a-c) are part of a system in which potable water is
circulated. Additional water as necessary for the system
is supplied to an output conduit 10c from a water stor-
age tank 11 via a conduit lOd. An input conduit 10a is
coupled by a pump 12 to an iodinating device 13. In the
iodinating device 13 is a dispensing compartment 13a,
an electro-chemical valve 136, and an I 2 accumulator
13c. The I 2 accumulator 13c contains a slurry of iodine
crystals and water. The valve 136 is electrically con-
trolled to pass iodine into the dispensing compartment
13a. Water from the system is passed through the dis-
pensing compartment 13a and is in contact with the
electro-chemical valve 136.
The output from the dispensing compartment 13a is
coupled to an iodine level sensing means 14 which de-
tects the iodine level in the water for the system. The
iodine sensing means 14 is coupled to the water storage
tank 11. Insofar as water flow is concerned, it passes
from the pump 12 through the dispensing compartment
13a and iodine sensing means 14 to the storage tank 11.
The storage tank 11 is coupled to the output conduit
10c.
The iodine sensing means 14 continuously detects the
level of iodine concentration in the water and produces
analog electrical signals representative or proportional
to the iodine concentration in the water. The electrical
signals representative of iodine concentration are sup-
plied to sensor electronic means 15 which convert the
analog electrical signals into digital signals. A signal
storage means 16 is coupled to the sensor electronic
means 15 to receive stored digital signals from the elec-
tronic means 15 and to output analog signals. A clock,
17, which can be a free running multivibrator and in-
clude a divider circuit, functions to initiate the sensor
electronic means 15 to obtain an iodine level reading
from the sensor means 14. After a signal is stored, the
clock causes the signal to be output from the storage
means 16. Thus the concentration is measured at dis-
crete times which can be one minute or longer.
The output signals from the storage means 16 are
suppUed to an error amplifier means 20. The error am-
pMer means 20 is also input with a calibrated electrical
si^al from a potentiometer 18a. The potentiometer
signal is representative of a desired iodine level or con-
centration in the water. If the iodine level decreases in
the water, an output signal is produced by the error
amplifier 20 to an integrator means 18 which operates a
bipolar current source 19. The bipolar current source is
responsive to the output of the integrator 18 to provide
a control current for the valve 136.
In the foregoing system, the sampling is periodic. If
continuous sampling is desired, the signals from the I 2
sensor 14 are supplied via an amplifier (not shown)
directly to the error amplifier 20.
Referring now to FIG. 2, the iodine sensor means 14
includes a tubular chamber 22 with flow inlets 14a and
146 ‘at opposite ends. The flow inlet 14a is angled with
respect to the axis of chamber 22 so that fluid flow into
the chamber 22 via the inlet 14a has an impinging and
washing action on a glass lens 23 which also serves as an
end cap. The outlet 146 similarly is angled with respect
to the axis of chtober 22 so that a washing action oc-
ciiii (as fluid exits from the chamber) on an end cap
glass lens 24. A detector 25 is aligned with the axis of
5
10
4,061,570
3
chamber 22 and includes a glass lens 26, a 45° beam
splitter mirror 27 and light sensors 28 and 29 aligned at
90 ° relative to one another and reMive to the axis of the
detector 25 and to the mirror 27. The light sensors 28
and 29 are respectively coupled to a ratio circuit 30
which provides an output if the ratio between the input
signals varies. A light source 32 and lens 34 provide
light for transmission through the cell 22 to the light
sensors 28 and 29. The sensors 28 and 29 are respec-
tively provided with a 465 mm interference filter and a
630 nm interference filter. Thus, a given ratio of signals
will be indicative of a given iodine level or concentra-
tion in the water supply. As the iodine is used and its
level decreases, the ratio changes to produce an output
signal on line 31.
The iodinating device 13 of the present invention is
illustrated in detail in FIG. 3. The iodinating device has
a generally rectangular box-like configuration with end
members 40 and 41 and a center member 42. The mem-
bers define an interior cavity which is divided into three
chamber sections 43, 44 and 45. Chamber section 43 is
defined by the end interior walls of the member 40 and
a valve means 13a. The middle chamber section 44 is
defined between the valve means 13Z» and a retainer
screen 46. The chamber section 45 is defined between
the retainer screen 46 and the interior walls of the mem-
ber 41.
The valve 136 is comprised of a center, flat member
47 and outer, flat metal screens 46 and 48 which form
electrodes. T^e membrane provides for ion exchange.
The anode electrode 46 is made of a noble metal and
coupled to an outlet terminal 49 and the cathode elec-
trode is made of a noble metal and is coupled to an
outlet terminal 50. When an electrical potential is ap-
plied across the anode and cathode 46 and 48, the mem-
brane 47 permits an ion exchange. The chamber sections
44 and 45 are fluidly interconnected and in chamber
section 45 is a slurry of water and I2 crystals. A perfo-
rated sheet 52 which can be plexiglass, together with a
stainless steel screen 53 retains the crystals in the section
45. The chamber section 44 contains dissolved I2 in
solution. I2 crystals are advantageous for this applica-
tion because they are solid at room temperature.
The anion exchange membrane 47 is preconditioned
by soaking in a stirred solution of 0.6 potassium iodine
solution for one-half hour. The membrane is then rinsed
and again soaked this time in a 0.1 normal potassium
iodide solution for one-half hour. The second step of
rinsing and soaking is then repeated. The membrane
immobilizes the iodine and prevents the water being
iodinated from contacting solid I2 crystals.
When a cmrent is passed between the anode and
cathode, the reactions occurring at the electrodes are:
Anode 21~ = h + 2e~
13“ = I2 +1“
Cathode I 2 + 2e~ = 21“
I2 +1“ = I3
The membrane is conductive to anions (I-, I3- and
OH-) and the cation portion of the electrolyte is immo-
bilized within the membrane. Hydrogen ions, water, I2,
HOI, etc., do not pass through the membrane as a result
of the anion exchange mechanism.
It will be appreciated that the iodinating means 13
can continuously iodinate the water passing through the
dispenser where the accumulator stores crystalline io-
4
dine and the electro-chemical valve controls the flow of
iodine to the water supply.
In the operation system, a pump circulates liquid to
be iodinated through the iodination means 13, the sensor
5 14 and the storage tank 11. The I2 level sensed by the
sensor 14 produces electrical signals which are com-
pared with an established I2 level set point signal (set pot .
18). Any difference in voltage between these signals
(the error) is sent to an integrator 18. The integrator 18
10 has an output which is constant only when its input
voltage is zero. The integrator output signal is used to
control the bipolar current source circuit 19 which, in
turn, produces a constant current directly proportional
to the signal received at its input. The valve 136 gener-
is ates iodine ions and disp>enses ions into the liquid loop as
a function of the electrical current flowing through it.
In this system, the sensor signal and set point signal
must be equal to cause the valve to release as much l2as
is being consumed. If the I2 level in the circulatory loop
20 should decrease, the output from the error amplifier
will increase from zero which will cause the output of
the integrator to start increasing. This causes a higher
current generation and therefore a higher I2 dispensing
rate.
25 To use the sensor to measure discontinuously, the
storage system 16 is inserted between the sensor 15 and
error amplifier 20. The clock 17 times the control sam-
pling and inputs. The amplifier 20 and integrator 18
operate to increase current values to a point when I2
30 generation and consumption are equal. The I2 sensor
measures I2 concentration at discrete time intervals of
one minute or longer. The sensor signal storage circuit
16 accepts an I2 level signal and stores it until a new
sensor signal is obtained. When a signal from the I2
35 system is to be stored, -a clock system will cause the I2
sensor signal to be converted to an eight-bit digital
number that is stored. Output from the storage circuit
16 is converted from digital to analog signals which are
used in the I2 control system. The stored signal is as-
40 sumed to be the latest I2 control signal representative of
the latest I2 concentration and will be maintained until a
new clock signal is received, at which time the system
will store the updated I2 sensor signal. By storing the
digital form of the I2 sensor signal, the length of time
45 which the signal is stored can be extended indefinitely.
The system clock 17 is a freenmning oscillator feeding
an eight-bit binary divider. Outputs from the binary
divider intitiate a signal to the I2 sensor 15 to initiate a
reading. The other output provides a signal to initiate
50 storage in the storage circuit 16. These two sisals
occur at different times so that the sensor 14 is automati-
cally instructed to measure and, after the measiu-ement,
the signals are allowed to stabilize and are stored.
Suitable non-metallic materials for use in the iodinat-
55 ing means include polypropylene, plexiglass, teflon,
epoxy resins, polysulfones, polyamides and nylons.
Stainless steel is a suitable metallic material and plati-
num is a suitable noble metal to use for the anode and
cathode.
60 Based upon iodine spectroscopy, the absorption char-
acteristics for I2 are such that at a wavelength of 466 nm
a crossover point exists where for a given concentration
of iodine the absorption is constant. This is an “isobestic
point” and at this wavelength iodine can be measured
65 unaffected by varying amounts of potassium iodide.
The sensor 14 is intended to measure iodine at a wave-
length of 466 nm. A dual detector, dual wavelength
system is used and the light measurements are taken at
4,061,570
5
two different wavelengths. In the sampling section,
which is made of anodized aluminum and fitted with
heat-absorbing glass windows, water enters and leaves
at an angle thereby generating a washing action on the
windows. In the detector section 25, there is a beam 5
splitter and two detectors 28 and 29. Collimated light
from the light cell are focused onto separate detectors
by virtue of a beam splitter. The beam splitter transmits
light through a 465 nm interference filter to a sample
detector and reflects light through a 630 nm filter to the 10
reference detector. The beam splitter 27 permits each
detector to “see” the same area of the sample cell win-
dow, thus any localized variation in the window clarity
will not influence the output of one detector more than
that of the other. 15
While particular embodiments of the present inven-
tion have been shown and described, it is apparent that
changes and modifications may be made without de-
parting from this invention in its broader aspects; and
therefore, the aim in the appended claims is to cover all 20
such changes and modifications as fall within the true
spirit and scope of this invention.
What is claimed is:
1. A system for iodinating water comprising
a. an iodine dispensing means having a first and a 25
second chamber separated by an electro-chemical
valve means, said first chamber being adapted to
receive a slurry of iodine crystals, said second
chamber having an inlet and an outlet for the flow
of water to be iodinated, said electro — chemical 30
valve means having an anion exchange membrane
sandwiched between two metal screens which
form electrodes, each of said metal screen elec-
trodes being electrically coupled to an outlet termi-
nal, said electro-chemical valve means being re- 35
sponsive to an electrical current for passing iodine
across said anion-exchange membrane,
b. an iodine sensor means for detecting the concentra-
tion of iodine in the iodinated water, said iodine
6
sensor means having an inlet and an outlet for the
flow of iodinated water, said inlet for the iodine
sensor means being fluidly coupled to said outlet of
the second chamber of the iodine dispensing means,
said iodine sensor means further having means for
producing an electrical signal representative of the
iodine concentration in the iodinated water flowing
through the iodine sensor means,
c. reference means for providing a present electrical
signal representative of a desired iodine concentra-
tion,
d. comparator means electrically coupled to said
iodine sensor means and said reference means for
comparing the electrical signal from said iodine
sensor means with the electrical signal from said
reference means and for producing an error signal
in the event of a difference in signal values, and
e. means for supplying said error signal to said outlet
terminals of said electrodes.
2. The system of claim 1 wherein said anion exchange
membrane is impregnated with potassium iodide.
3. The system of claim 1 wherein a perforated mem-
ber is disposed in said first chamber adapted to separate
crystalline iodine in a slurry of iodine crystals from said
anion exchange membrane.
4. The system of claim 1 wherein said electrodes are
comprised of a noble metal.
5. The system of claim 4 wherein said noble metal is
platinum.
6. The system of claim 1 wherein said electrodes are
comprised of platinum screens, said anion exchange
membrane is impregnated with potassium iodide, and
said first chamber has disposed therem a slurry of iodine
crystals.
7. The system of claim 6 wherein a perforated mem-
ber is disposed in said first chamber so that the iodine
crystals are separated from said anion exchange mem-
brane.
*****
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