Laboratory prototype water quality monitoring system provides automatic system for online monitoring of chemical, physical, and bacteriological properties of recovered water and for signaling malfunction in water recovery system. Monitor incorporates whenever possible commercially available sensors suitably modified

Hartung, W. H.

Misselhorn, J. E.

Witz, S. W.

English

NASA Technical Reports Server

May 1974	 B74-10029 
NASA TECH BRIEF 
Langley Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Automated Monitoring of Recovered Water Quality 
S
A laboratory prototype water quality monitoring 
system has been developed. The system (see Figure 1) 
was designed to provide an automatic system for online 
monitoring of the chemical, physical, and bacteriological 
properties of recovered water and for signaling a mal-
function in the, water recovery system. The parameters 
monitored and the ranges measured are: chloride ion, 
10 to 1000 ppm; ammonium ion, 1 t . 100 ppm; 
pH, .2 to 11; specific conductance, 1 to 1000 pmho/cm;. 
total organic carbon, up to 100 ppm; and bacteria 
(E. coli),.10 to 5x10 3 cells/mi. Water sample size was 
500 ml/hr, and the sensors were integrated into a total 
system with alarms and readouts.  
This , water monitor is a practical approach to 
assessing the potability of reclaimed water, incorporating 
whenever possible commercially available sensors suitably 
modified. These sensors are simple, reliable, able to 
operate in a flow system (up to 2 mI/mm), and capable 
of withstanding pressure up to about 5 psig (136x103
N/rn 2 ); each sensor has a direct readout and an output 
for remote monitoring. The sensor used for monitoring 
the bacteriological quality of recovered water does so by 
a chemiluminescence technique. Signals obtained for 
both incubated and unincubated bacterial samples permit 
differentiation between living and dead organisms, and a 
higher signal for the . incubated sample indicates the 
presence of viable organisms. 
The detection principle is based on measuring the 
increase in cherniluminescence produced by the catalytic 
action of bacterial porphyrins, specifically hematin, on a 
luminol-hydrogen peroxide mixture. Hematin is a sub-
stance found in most organisms, and the reaction is 
virtually instantaneous, occurring immediately on mixing 
the bacterial suspension with the aqueous reagents. 
Mixing is carried out within the view of a photo-
multiplier tube which monitors the light emitted by the 
reaction. The signals generated are directly proportional 
to the number of bacteria present. 
Water 
Recovery 
System 
S
Organic pH	 Ciand NH4 
rbo
n	 F-i Sensor	 Sensors	 f lyzer
 CA i/hr Biosensor 
L __I Waste	 Water Monitor	 I ___
Figure 1. Closed-Loop Monitoring System
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19740000029 2020-03-17T14:01:24+00:00Z
Sample A Supply Sample A Return 
Semple BSupply -- - -- Sample BReturn 
Metering Pumps, Valcen, I and I Fitter Concentrator Control 
1 I Electronic, 
Deotro,. r'I Reactor - - Broth I	 I I Metering Pc,npp and VaIc,, 
4MUrea t
Photo-
multiplier 
-EEl O2
Electronim Eli-
Recorder 
Remote Alarm S.gnal  output Ootpot 
Red Red Green 
Sample	 Sample 
A	 B
Figure 2. Biosensor Block Diagram 
The biosensor is designed to monitor water from two 
sources independently (see Figure 2). Sample A water is 
processed for total bacterial content only. Sample B 
water may be processed for total bacterial content or 
for viable content. All sample processing paths (for both 
incubated and unincubated samples) which have been 
exposed to bacteria are flushed with a bactericide and 
filtered distilled water to minimize the possibility of 
contamination. 
An 18-step programmer performs most of the process 
control. Each step on the programmer has an adjustable 
dwell time ranging from about 5 seconds to 10 minutes. 
The sampling step, 25 minutes, is the only step not 
falling within this time frame. Up to 20 functions are 
controlled during, each step. Signals from the photo-
multiplier tube are sent to the processing electronics 
and also provide a readout which is displayed on a strip-
chart recorder for permanent record and analysis-of-data 
purposes. 
Also sampled is the reagent baseline signal which is 
compared to the signal from the bacterial challenge.
When the signal exceeds a preset limit (over and above 
the reagent signal), an alarm light is turned on and 
remains on until a manual reset switch is activated. 
The single paramount requirement of a water recla-
mation system is to provide water that is safe for human 
consumption, physiologically and psychologically. While 
a monitoring system itself cannot do this, its data can 
provide the governing criteria for judging water pota-
bility. Therefore the selection of parameters to be 
monitored is of prime importance. 
No single set of requirements can be categorically 
considered as the ultimate in potability standards, but 
reasonable judgments must be made based upon many 
diverse factors. These include the iii'dividual and com
-
bined toxicologies of potential and bacteriological con-
taminants, the capabilities of the specific reclamation 
system, and its possible contribution of additional 
contaminants. A complete specification for general 
water quality must necessarily include numerous chem-
ical, physical, and biological property requirements. On 
the other hand, a practical water quality monitor may 
be limited to only those contaminants that are toxic and 
that have a chance, to some acceptable level of 
probability, of being present during normal operation 
or through the malfunction of equipment. This water 
monitor will accomplish these functions. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Langley Research Center 
Mail Stop 139-A 
Hampton, Virginia 23665 
Reference: B74-10029 
Patent status: 
NASA has decided not to apply for a patent. 
Source: J. E. Misselhorn, W. H. Hartung,

and S. W. Witz of
Aerojet Medical & Biological Systems

under contract to

Langley Research Center

(LAR-1 1203)
. 
[1 
B74-10029	 Category 05,04,02,06 


Automated monitoring of recovered water quality

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