The system disclosed is for controlling the iodine level in a water supply in a spacecraft. It includes an iodine accumulator which stores crystalline iodine, an electrochemical valve to control the input of iodine to the drinking water and an iodine dispenser. A pump dispenses fluid through the iodine dispenser and an iodine sensor to a potable water tank storage. The iodine sensor electronically detects the iodine level in the water, and through electronic means, produces a correction current control. The correction current control operates the electro-chemical iodine valve to release iodine from the iodine accumulator into the iodine dispenser

Powell, J. D.

Schubert, F. H.

Wynveen, R. A.

English

NASA Technical Reports Server

United States Patent [19] P 1 1  4,061,570 
Fletcher et al. P I  Dec. 6, 1977 
[54] IODINE GENERATOR FOR RECLAIMED 
[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. Schubert, Mentor, 
all of Ohio 
WATER PURIFICATION 
[21] Appl. No.: 571,459 
[22] Filed: Apr. 25, 1975 
[51] Ist, C1.2 ............................ BOlJ 1/06; BOlJ 4/02; 
GOlN 21/02; GOlN 33/18 
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 
WI References Cited 
[52] US. CI. ................................. 210/96 M 210/192; 
U.S. PATENT DOCUMENTS 
3,288,708 11/1966 Cordle et al. .......................... 210/62 
3,351,542 11/1967 Oldershaw et al. ................... 210/62 
3,464,555 9/1969 Schneider .............................. 210/96 
3,528,545 9/1970 Frazel et al. ........................... 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 0. Wolk 
Assistant Examiner-Bradley Garris 
Attorney, Agent, or Firm-Carl 0. McClenny; John R. 
Manning; Marvin F. Matthews 
1571 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 
CURRENT INTEGRATOR - 
I I I SOURCE 
CONCEN TRA TlON ERROR - - 
SET POT AMPLIFIER 
18a 
i7 
WATER TANK 
STORAGE 
I 
/ 1OC 
I 
10 d 
----c 17 
https://ntrs.nasa.gov/search.jsp?R=19780006841 2020-03-20T13:00:57+00:00Z
U.S. Patent Dec. 6, 1977 4,061,570 
CONCEN TRA TION 
SET POT 
19 - ERROR - INTEGRATOR - CURRENT - 
SOURCE t AMPL INER 
32 
t 
FIG. 2 
49- 
FIG. 3 
1 
4,06 1,570 
2 
IODINE GENERATOR FOR RECLAIMED WATER 
PURIFICATION 
5 j 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). 10 
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 electrochemical 15 
iodine valve which can be operated by an electrical 
current in response to detection of iodine levels in the 
water sopply 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 weight, 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 amplifier 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- 
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 I2 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. 
35 
change. 50 
60 BKIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a schematic illustration of the system em- 
bodying the present invention; 
FIG. 2'is a schematic illustration of an I2 sensor for 
the system; and 65 
FIG. 3 is a view in cross-section through an iodina 
ing device embodying the principles of the present in- 
vention. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
e of system is illustrated in FIG. 1. Conduits 
lO(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 1Oc from a water stor- 
age tank 11 via a conduit 1Od. An input conduit 1Oa 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 12 accumulator 
1%. The I2 accumulator 13c contains a slurry of iodine 
crystals and water. The valve 136 is electrically con- 
trolled to pass iodine into the dispensing compartment 
1%. 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 
1% and iodine sensing means 14 to the storage tank 11. 
The storage tank 11 is coupled to the output conduit 
1oC. , 
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 
supplied to an error amplifier means 20. The error am- 
plifier means 20 is also input with a calibrated electrical 
signal from a potentiometer 18u. 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 
des a tubular chamber 22 with flow inlets 14a and 
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 
outlet 146 similarly is angled with respect 
chamber 22 so that a washing action oc- 
curs (as fluid exits from the chamber) on an end cap 
glass lens 24. A detector 25 is aligned with the axis of 
4 
4,06 1,570 
3 
chamber 22 and includes a glass lens 26, a 45" beam dine and the electro-chemical valve controls the flow of 
splitter mirror 27 and light sensors 28 and 29 aligned at iodine to the water supply. 
90" relative to one another and relative to the axis of the In the operation system, a pump circulates liquid to 
detector 25 and to the mirror 27. The light sensors 28 be iodinated through the iodination means 13, the sensor 
and 29 are respectively coupled to a ratio circuit 30 5 14 and the storage tank 11. The I2 level sensed by the 
which provides an output if the ratio between the input sensor 14 produces electrical Signals which are corn- 
signals varies. A light source 32 and lens 34 provide pared with an established It level set point Signal (set pot 
light for transmission through the cell 22 to the light 18)- Any difference in voltage between these Signals 
Sensors 28 and 29. The sensors 28 and 29 are respec- (the error) is sent to an integrator 18. The integrator 18 
tively provided with a 465 mm interference filter and a 10 has an output which is constant only when its input 
630 nm interference filter. Thus, a given ratio of signals voltage is zero. The integrator output signal is used to 
will be indicative of a given iodine level or concentra- control the bipolar current source circuit 19 which, in 
tion in the water supply. As the iodine is used and its turn, produces a constant current directly proportional 
15 ates iodine ions and dispenses ions into the liquid loop as signal on line 31. 
The iodinating device 13 of the present invention is a function of the electrical current flowing through it. 
a generally rectangular box-like configuration with end must be equal to cause the valve to as much It as 
members and 41 and a center member 42. The mem- is being consumed. If the It level in the circulatory loop 
20 should decrease, the output from the error amplifier bers define an interior cavity which is divided into three will increase from which will cause the output of 
the integrator to start increasing. This causes a higher chamber sections 43,44 and 45. Chamber section 43 is defined by the end interior Of the member and current generation and therefore a higher I2 dispensing a valve means 13a. The middle chamber section 44 is rate. defined between the valve means 136 and a retainer 25 to measure discontinuously, the screen The chamber section 45 is defined between storage system 16 is inserted between the sensor 15 and the retainer screen 46 and the interior walls of the mem- errOr amplifier 20. The clock 1, the control -- ber 41. piing and inputs. The amplifier 20 and integrator 18 The valve 136 is comprised of a center, flat member operate to increase current to a point when I2 
47 and Outer, flat metal which form 30 generation and consumption are equal. The Iz sensor 
electrodes. The membrane provides for ion exchange. concentration at discrete tirne intervals of 
The anode electrode 46 is made of a noble metal and one minute or longer. The sensor signal storage circuit 
coupled to an outlet terminal 49 and the cathode elec- 16 accepts an level signal and it until a new 
trode is made of a noble metal and is coupled to an sensor 
Outlet terminal 50* When an 35 system is to be stored, a clock system will cause the 12 
p l id  across the anode and cathode 46 and 48, the mem- sensor signal to be converted to an eight-bit digital 
brane 47 pennits an ion exchange* The chamber number that is stored. Output from the storage circuit 
44 and 45 are fluidly interconnected and in &amber 16 is converted from digital to analog signals which are 
section 45 is a slurry of water and Iz crystals. A perf@ used in the I2 control system. The stored signal is as- 
rated sheet 52 which - be Plexiglass, together With a 40 sumed to be the latest I2 control signal representative of 
Stainless Steel Screen 53 retains the Crystals in the section the latest until a 
45. The d~amber section 44 Contains dissolved 12 in new clock signal is received, at which time the system 
solution. 12 crystals are advantageous for this aPPliCa- will store the updated It sensor signal. By storing the 
tion because they are solid at room temperature. digital form of the I t  sensor signal, the length of time 
extended indefinitely. 
by Soaking in a Stirred solution of 0.6 potassium iodine The system clock 17 is a f r e e m h g  oscillator f&g 
Solution for one-half hour. The membrane is then rinsed an eight-bit binary divider. Outputs from the binary 
and again soaked this t h e  in a 0.1 normal Potassium divider intitiate a signal to the I2 sensor 15 to initiate a 
iodide solution for one-half hour. The second step of reading. The other output provides a s i 4  to initiate 
rinsing and soaking is then repeated. The membrane 50 storage in the storage circuit 16. These two signals 
immobilizes the iodine and prevents the water being occur at different times so that the sensor 14 is automati- 
iodinated from contacting solid I2 crystals. cally instructed to mequre and, after the measurement, 
When a current is Passed between the anode and the signals are allowed to stabilize and are stored. 
cathode, the reactions occurring at the electrodes are: 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- Anode 21- = I2 + 2- 
Cathode I2 + Ze- = 21- num is a suitable noble metal to use for the anode and 
cathode. 
Based upon iodine spectroscopy, the absorption char- 
acteristics for Izare 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 
level decreases, the ratio changes to produce an output to the signal received at its input. The valve 13b gener- 
flustrated in detail in FIG. 3. The iodinating device has In this system, the Sensor signal and set point signal 
To use the 
and 
is obtained. men a signal from the 
potential is 
concentration and will be 
The anion exchange membrane 47 is preconditioned 45 which the signal is stored can 
13- = 12 + I- 
I2 + I- = 13 
The membrane is conductive to anions (I-, Ip -  and 
OH-) and the cation portion of the electrolyte is immo- 
bilized within the membrane. Hydrogen ions, water, 4, 
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- 
60 
5 
4,061,570 
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 d 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 anionaxchange membrane, 
b. an iodine sensor means for detecting the concentra- 
tion of iodine in the iodinated water, said iodine 
40 
45 
50 
55 
60 
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 therein 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. * * * * +  
65 


Iodine generator for reclaimed water purification

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