EPA-600/4-77-028
May 1977
Environmental Monitoring Series
INVESTIGATION OF THE ORION RESEARCH
AMMONIA MONITOR
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. fnteragency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/4-77-028
May 1977
INVESTIGATION OF THE ORION RESEARCH AMMONIA MONITOR
by
Robert J. 0'Herron
Instrumentation Development Branch
Environmental Monitoring and Support Laboratory
Cincinnati, Ohio 45268
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and
Support Laboratory - Cincinnati, U.S. Environmental Protection Agency,
and approved for publication. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
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FOREWORD
Environmental measurements are required to determine the quality
of ambient waters and the character of waste effluents. The Environ-
mental Monitoring and Support Laboratory - Cincinnati (EMSL) conducts
research to:
Develop and evaluate techniques to measure the presence
and concentration of physical, chemical, and radiological
pollutants in water, wastewater, bottom sediments and
solid waste.
Investigate methods for the concentration, recovery, .and
identification of viruses, bacteria and other microbio-
logical organisms in water, and conduct studies to
determine the responses of aquatic organisms to water
quality.
Conduct an agency-wide quality assurance program to
assure standardization and quality control of systems
for monitoring water and wastewater.
This report is part of a continued effort by the Instrumentation
Development Branch, EMSL - Cincinnati, to investigate instruments and
provide information to both users and suppliers. The intention is also
to upgrade instrumentation and to make it possible to .choose the most
suitable instrument for a particular application.
Dwight G. Ballinger
Director
Environmental Monitoring and
Support Laboratory - Cincinnati
111
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ABSTRACT
The Orion Research ammonia monitor was investigated using the
Orion specifications and environmental considerations as a guide.
Laboratory tests under controlled environmental conditions showed the
electronic stability (drift) to be well within ±10 percent of reading
over the temperature range 5C to 42C. Sensor stability over the tempera-
ture range 5C to 42C was tested by applying ammonia nitrogen (standard
solutions of 10 mg/1, 50 mg/1, and 100 mg/1) as direct input to the
monitor. The results of these tests showed that automatic restandardi-
zation maintained readings within Orion's specified tolerance of ±10
percent of reading.
Dynamic on-stream measurements were made of a secondary sewage
treatment plant effluent in a field installation. These measurements
were periodically compared with those of the standard method of distil-
lation and titration. Sixty-five percent of these comparisons were
within ±10 percent of reading. Steady-state comparisons were made of
field-collected samples with the standard method for determining ammonia
nitrogen. It appeared from these tests that a 5 percent loss in ammonia
concentration resulted from the required straining and filtering of the
sample input to the monitor. Eight of the nine samples compared were
within 10 percent of the standard method.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures . vi
Tables vi
Acknowledgments vii
1. Introduction 1
2. Conclusions 4
3. Recommendations 6
4. The Orion Ammonia Monitor . 8
5. Laboratory Investigation 13
6. Field Installation of the Ammonia Monitor, 23
•References 30
v
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FIGURES
Number Page
1 The Orion Ammonia Monitor ?
2 Ammonia Electrode 10
3 Fluids Panel H
4 Ammonia Electrode Installation Transient 14
5 PVC "Y" Strainer 20
6 Field Sample Test Apparatus 21
7 Mobile Van Installed at Muddy Creek Treatment Plant 24
8 Intake Pump Installation 24
9 Inlet Strainer After Test 24
10 PVC "Y" Strainer and Associated Components 24
11 Regression Line with 95 Percent Confidence Limits for the
Mean Response 27
12 Relative Frequency Histogram 28
TABLES
1 Test Over Complete Operating Range With Ammonia Standards.... 15
2 Slope Per Decade at 20C, mv. . 15
3 Electronic Stability with Temperature 16
4 Module Temperature After Stabilization 17
5 System Stability at 20C 18
6 System Stability Over the Temperature Range 5C to 42C 19
7 Laboratory Test with Secondary Effluent Waste from the
Muddy Creek Waste Treatment Plant 22
8 Additional Sample from the Muddy Creek Waste Treatment
Plant -. 22
9 Comparison of Ammonia Monitor Field Installation Data
with Laboratory Analysis by the Standard Method. 26
VI
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ACKNOWLEDGMENTS
We gratefully acknowledge the support and help of Dr..D. F. Bender,
Research Chemist (Physical and Chemical Methods Branch, EMSL) in preparing
standards and analyzing samples; W. T. O'Connell (Orion) for installation
assistance; T. J. Stasiak (former Manager, Monitor Systems - Orion) for
helpful discussions on the theory and operation of the ammonia monitor;
G. G. Seymour (Assistant Superintendent of Operations, Metropolitan Sewer
District, Cincinnati, Ohio) for permission to install the ammonia monitor
in a sewage treatment plant; C. Weider (Plant Superintendent, Muddy Creek
Waste Treatment Plant) for cordial cooperation; and Dr. R. N. Kinman,
(University of Cincinnati) for -technical assistance on this project.
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SECTION 1
INTRODUCTION
AMMONIA LEVELS IN SEWAGE TREATMENT PLANT EFFLUENTS
Unpolluted surface waters contain relatively small amounts of
ammonia and ammonium compounds. Higher levels than 0,1 mg/1 ammonia
nitrogen usually indicate organic pollution.^ A principle source of
ammonia in surface waters is from treated wastes discharged from waste
treatment plants. Domestic wastewaters are essentially urine, feces,
and cellulose dispersed in relatively large volumes of water. Approxi-
mately 80 percent of the total nitrogen is introduced into wastewater
as urea, which is rapidly converted to ammonia by the enzyme urease.
The amount of nitrogen introduced into domestic waste is approximately
53 mg/1, of which 80 percent may be attributed to urea. Substantial
variations from these values are encountered and are attributed to
larger or smaller volumes of dilution water or additional sources of
nitrogen.
Ammonia nitrogen discharged from waste treatment plants has several
undesirable features^
(1) ammonia consumes dissolved oxygen in the receiving water,
(2) ammonia reacts with chlorine to form chloramines, which are
less effective than free chlorine,
(3) ammonia is toxic to fish life,
(4) ammonia is corrosive to copper fittings, and
(5) ammonia increases the chlorine demand at waterworks down-
stream.
Several methods have been developed to convert, reduce, or remove
ammonia nitrogen from wastewaters. These include biological nitrifi-
cation - denitrification, selective ion exchange, air stripping at
elevated pH, and breakpoint chlorination. The characteristics of the
wastewater, the extent of treatment, and the inclusion of one of the
various ammonia removal techniques, then, results in a wide variability
in ammonia levels discharged from waste treatment plants.
LABORATORY METHODS OF DETERMINING AMMONIA CONCENTRATION
Methods for Chemical Analysis of Water and Wastes^ contains the
analytical procedures used in U.S. Environmental Protection Agency (EPA)
laboratories for the examination of ground and surface waters, domestic
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and industrial waste effluents, and treatment process samples. Where
economics and sample load do not warrant the use of automated equipment,
the distillation procedure is the method of choice for determining
ammonia nitrogen per liter (NH3 - N/l). The method is applicable in
drinking, surface, saline, and domestic and industrial wastes. Samples
are buffered with borate buffer and then distilled into a solution of
boric acid. The method covers the range 0.05 to 1.0 mg/1 NH3 - N/l for
nesslerization-colorimetric procedures, from 1.0 to 25 mg/1 NH3 - N/l
for the titrimetric procedure with standard sulfuric acid, and from 0.05
to 1400 mg/1 NH3 - N/l potentiometrically by the ammonia electrode. The
ammonia selective electrode method is described for the range 0,03 to
1400 mg/1 NH/3 - N/l where distillation is not necessary. The automated
colorimetric phenate method describes the determination of ammonia for
the same type waters in the range 0.10 to 2.0 mg/1 NHg - N/l. Higher
concentrations can be determined by sample dilution. The Technicon
AutoAnalyzer apparatus is used for this method.
Standard Methods^ requires preliminary distillation when interfer-
ences are present in determining ammonia nitrogen. Sensitivity is said
to approximate 200 Mg/1 NH^ - N/l for direct nesslerization measurements.
The phenate method is given tentative status and it lists a sensitivity
for estimating ammonia of 10 yg/1 NH3 - N/l and a usefulness up to 500
Mg/1. The titrimetric procedure, although subject to amine interfer-
ences, is said to be free of interferences from neutral organic compounds.
The ASTM Standards^ lists methods of test for ammonia in industrial water
and industrial wastewater. Two methods are described, the Referee Method
(Distillation Method) and the Non-Referee Method (Direct Nesslerization
Method).
PREVIOUS INVESTIGATION OF THE AMMONIA ELECTRODE
The Orion ammonia selective electrode was employed in the deter-
mination of ammonia in surface waters, sewage samples, and saline waters
by Thomas and Booth.' River and sewage samples were tested for ammonia
by the electrode method and the indophenol blue method on a Technicon
AutoAnalyzer and were found to be comparable. Advantages cited in the
use of the ammonia electrode were minimal sample and reagent preparation
prior to analysis, wide concentration range, precision and accuracy
comparable to accepted methods, speed of determination, and moderate
cost of the electrode.
LeBlanc and Sliwinski^ analyzed biologically treated effluent
samples, wastewaters from a food processing plant, an acid and explo-
sive plant, a sulfite pulp mill, a kraft pulp and paper mill, and a
chemical plant. Good correlation was obtained between the ammonia
electrode method and by distillation with nesslerization and/or acid
titration. Poor agreement, however, was obtained with untreated waste
from the kraft mill. It was concluded that the ammonia electrode's
good correlation with standard methods made it an excellent analytical
tool for the measurement of ammonia nitrogen in wastewater.
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Gilbert and Clay^ evaluated the ammonia electrode on samples from
different marine life display tanks and sea water samples. It was con-
cluded the electrode provides an accurate means of analyzing ammonia in
sea water and that it is usually more precise than the spectrophoto-
metric method. Field analyses were equally favorable as those in the
laboratory. Favorable results were also obtained by the ammonia elec-
trode in sea water samples by Srna, et al.^0
Orion has stated that monitoring systems can be designed for all
laboratory methods of analysis utilizing ion-selective electrodes. The
ammonia selective electrode is the focal point of an ammonia monitor
developed by Orion Research. Physical and chemical pretreatment of a
sampled stream enables continuous monitoring of the ammonia concentra-
tion. The monitor is designed for installation in an industrial
environment with built-in capabilities for control. This report is
the result of an investigation to evaluate the Orion Research Ammonia
Monitor for its intended applications.
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SECTION 2
CONCLUSIONS
1. When a new or refurbished ammonia electrode is installed, a 16-hour
transient drift occurs before equilibrium is established.
2. Although the lower decade slopes of three ammonia electrodes tested
were somewhat less than the upper decade slopes, they were suffi-
ciently close to warrant a 2-decade output range for the ammonia
monitor.
3. The ammonia electrode's 90 percent of a decade change within 8
minutes appears to be adequate for the r-lowly changing ammonia
concentration observed in a sewage treatment plant.
4. Electronic drift at constant temperature (20C) was less than 0.1
percent for a 3-day interval.
5. Electronic drift over the temperature range 5C to 42C averaged
1.8 mv per degree centigrade for a midscale setting. This drift
did not exceed Orion's specified tolerance of ±10 percent of
" reading
6. Automatic restandardization restores sensor drift as a result of
temperature change to within ±10 percent of reading over the tem-
perature range 5C to 42C.
7. The steady-state performance of the ammonia monitor on a field
sample was within ±10 percent of reading on eight of nine compari-
sons with a standard method. The samples were secondary effluent
from a sewage treatment plant that were spiked over the range of
the distillation and titration procedure for ammonia nitorgen.
8. The data from the.laboratory test of a field sample suggest that
a 5-percent loss of ammonia nitrogen occurs across the strainer
and filter.
9. Dynamic on-stream measurements of ammonia of a secondary clarifier
effluent were made with the ammonia monitor. Sixty-five percent
of 23 sample sets analyzed with the standard method and the monitor
were within ±10 percent of reading.
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10. When tested at the 0.05 level of significance, there were no
differences noted between the monitor data and data obtained by
the standard method.
11. Improvement in the sample handling* characteristics of the ammonia
monitor would be desirable so that the introduction of solids would
be less disruptive.
12. The tubing associated with the electrode holder of the constant
temperature assembly (CTA) appears to be a chronic source of
blockage problems.
13. The Orion ammonia monitor includes stable electronics that performed
well under changing environmental conditions. The basic design of
the monitor appears adequate for measuring ammonia nitrogen under
changing environmental conditions and dissolved samples character-
istics. Careful consideration, however, needs to be given to the
sample intake to avoid excessive solids with the present sample
handling. Care and attention, such as periodic backflushing of
intake plumbing, is necessary to avoid clogging. The filter life,
also, is reduced when excessive particulate matter is encountered.
Interruptions in sample and reagent flow or filter breakthrough
clog tubing within the CTA of the monitor. The present design
requires complete replacement of the electrode holder when such
clogging occurs.
Correspondence from Orion indicates an awareness of clogging problems
and they have developed a Linear Membrane Filter (LMF) that eliminates
"breakthrough" and the resultant clogging of the monitor.
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SECTION 3
RECOMMENDATIONS
The Orion Research ammonia monitor performed adequately in the
measurement of ammonia nitrogen where moderate amounts of particulate
matter were encountered. Present monitor input sample handling require-
ments prevent its use in some locations where it is desirable to measure
ammonia. Redesign or modification of sample input requirements, can
extend the applicability of the ammonia monitor. Meanwhile, it is
recommended that EPA place emphasis on research efforts to provide better
sample conditioning for continuous monitors in general. Chopper pumps
are available to reduce particle size of solids in liquids to 3.175 mm
(1/8 in.). Further reduction of particle size is necessary. Present
blenders are not manufactured to withstand the rigors of continuous
operation. What is needed is rugged, dependable means of reducing
particle size of solids in liquids. The small orifices and tubing
requirements of reagent addition monitors are necessary for speed of
response and to reach an economic compromise in reagent consumption.
This being true, the particle size encountered must be controlled.
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Figure 1. The Orion Ammonia Monitor
7
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SECTION 4
THE ORION AMMONIA MONITOR
MONITORS EMPLOYING GAS-SENSING ELECTRODES
The Orion Series 1000 monitors are continuous monitors which
duplicate laboratory methods utilizing ion-selective electrodes. These
monitors can be grouped in two general categories; those that employ
solid-state electrodes and those that employ gas-sensing electrodes.
Characteristics of monitors utilizing solid-state electrodes have been
described in a previous report on the Orion Cyanide Monitor.H The
model 1110 Orion Research ammonia monitor is equipped with a combina-
tion (internal reference electrode) gas-sensing electrode.
A paper by Ross, et al, describes a theoretical model relating
time response, electrical potential, and limit of detection as a function
of membrane properties, geometry, and internal electrolyte composition
for gas-sensing electrodes. Furthermore, the model predicts that the
time response depends on the direction of concentration change:
t =
1m
Dk
dC
1.0 +
dC
in £ (1)
'2
where 1 = thickness of internal electrolyte
m = thickness of membrane
D = membrane phase diffusion constant
k = partition coefficient of species between the aqueous sample,
internal electrolyte phase, and the membrane phase
C = concentration of neutral species in internal electrolyte
Cn = sum of concentration of all other forms, and
13
AC = concentration difference between inner and outer membrane
interfaces
C_ = new equilibrium concentration of internal electrolyte
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e =
c2-c
C2
The combination electrode is composed of a fluorocarbon body with a
hydrophobic, gas permeable membrane affixed with spacers at the tip. An
epoxy inner electrode contains a flat pH glass electrode at the tip and a
chloride ion electrode on the outer surface. A measured volume of inter-
nal electrolyte, ammonium chloride in solution with a nonaqueous additive,
is introduced into the probe. The inner electrode is carefully placed
within the probe, such that a small volume of internal filling solution is
enclosed between the pH glass tip and a chloride ion electrode on the
outer surface. A measured volume of internal electrolyte, ammonium
chloride in solution with a non-aqueous additive, is introduced into the
probe. The inner electrode is carefully placed within the probe, such
that'a small volume of internal filling solution is enclosed between the
pH glass tip and the gas permeable membrane. The rest of the electrolyte
forms a reservoir surrounding the inner electrode, in contact with the
chloride ion electrode. The chloride ion electrode establishes a fixed,
stable, reference potential with the high chloride ion in solution. To a
small extent the ammonium chloride in solution forms the following equi-
librium:
NH3 + H20 5? NH* + OH" (2)
Ammonia gas, penetrating the gas permeable membrane, shifts this reaction
and a change in pH is detected by the glass electrode. The high concen-
tration of NH * in the filling solution results in the OH" being directly
proportional to the concentration of NHg. The measuring electrode poten-
tial may be described by:
E = S logJNH3J (3)
where E = half-cell potential of the pH electrode
S = slope
= ammonia concentration
The half-cell potentials of the measuring and reference electrodes serve
as input to a high-impedance-electrometer preamplifier in the electronics
section of the monitor. A cross-sectional of the ammonia electrode is
shown in Figure 2.
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outer body
inner body
spacer
sensing element
reference
element
internal
filling
solution
O-ring
bottom cap
membrane
Figure 2. Ammonia electrode (courtesy of Orion Research Incorporated).
CHEMICAL SENSING PANEL
Sample handling within the monitor takes place on a fluid handling
panel. Either sampling or standardizing solutions are selected by the
operation of a valve controlled by circuitry within the electronics sec-
tion. A proportioning pump feeds 1 ml per minute of sample and 0.22 per
minute of reagent to a mixing chamber. A motor agitates two small magne-
tic stirrers to mix the sample/reagent as it is being fed to a constant
temperature assembly (CTA). Air scrubbed of ammonia in a dilute acid
solution is also pumped into the CTA. A block diagram of the fluids panel
is shown in Figure 3.
An aluminum block in the CTA is machined to form the electrode holder
and terminus for the fluids flow. The cool side of a thermoelectric
cooler is butted up against the aluminum block under pressure. Heating
elements and thermistor are imbedded within the block. The overall
design is intended to maintain the electrode, with its internal components
and filling solution, the aluminum-block-electrode holder, and the con-
tinuous flow of sample and air, all at a low temperature differential. A
low operating temperature (18C-20C) is pursued in Orion's design so that
water vapor (an interference at 28C and above] is reduced.
Tubing for the sample and airflow is coiled about the aluminum-block
electrode holder and enters at a chamber in the lower end of the block.
Here the sample tumbles down a ramp where the ammonia gas can escape into
an air gap above. The airflow provides a continuous mixing so that rapid
equilibrium is attained by the partial pressure of ammonia gas in contact
with the electrode suspended from above. The electrode, therefore, is
not in contact with the sample solution and, in fact, it is disruptive
should this occur.
10
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constant
temperature
assembly
ammonia
scrubbed air
1 4-channel
• proportioning
I pump
waste
standard sample
Figure 3.
reagent
Fluids panel.
The reagent contains buffered EDTA that raises the pH of the sampled
solution to 10.5". A sufficient fraction of gaseous ammonia exists at this
pH and an economical compromise in reagent concentration is attained.
Known gaseous interferences are mostly ionized at this high pH. Calcium
and magnesium ions commonly encountered in sampled waters are complexed by
the EDTA. If the osmotic pressure of the sample solution differs from
that of the internal filling solution in-the electrode, water vapor will
diffuse across the membrane causing the concentration of ammonia inside
the membrane to slowly change. A nonaqueous additive in the internal
filling solution, and the osmotic strength adjustment of the reagent raise
the osmotic pressure of each to an equally high and unchanging value.
The thermoelectric cooler is an interesting application of the
Peltier Effect. -^ It involves the heating or cooling of the junction of
two thermoelectric semiconductor materials by passing current through the
junction. A power supply with a low voltage, high current output passes
a continuous current across the junction of an array of semiconductor
11
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materials. The hot side is connected to a copper-block heat sink. A fan
and a thin fin heat exchanger conduct the heat away. The cool side, as
mentioned earlier is in contact with the aluminum block that forms the
electrode holder. A thermistor imbedded in the block, in conjunction with
a temperature control circuit in the electronics section, controls the on-
off rate of the heating elements.
GENERAL CONSIDERATIONS
The intended usage of the Orion ammonia monitor is for fixed instal-
lation in an industrial location. Unless it is firmly mounted in a
trailer, its overall design, physical dimensions, and weight rule out
portability. The ammonia monitor is enclosed in a NEMA 12 case with over-
all" dimensions of 167 cm high, 69 cm wide, by 36 cm deep (66 in. x 27 in.
x 14 in.) and it has a mass of 145 kg (320 Ibs). The input power may be
selected from 100/115/220/240 VAC, 50/60 Hz, at 220 watts. A single
reagent is supplied in a 3.785 liter (5 gal) container.
The purchase price of the Orion ammonia monitor is $7,950. With con-
tinuous operation, there are sustaining reagent and supply costs. A
service contract is available from Orion that provides replacements for
reagents and for all expendable monitor supplies on a yearly basis for
$1,750. The replacement schedule is based on 1 year of continuous, 24-
hour-per-day operation. For those who wish to operate intermittently,
unit costs for items range approximately 20-30 percent greater.
12
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SECTION 5
LABORATORY INVESTIGATION
INVESTIGATION OBJECTIVES
Tests were conducted in the laboratory to investigate the performance
capabilities of the Orion ammonia monitor. The objectives of these labo-
ratory tests were to commence with the measurement of ammonia standards
under favorable conditions, to continue under more difficult conditions
and, eventually, to measure wastewater treatment plant effluent samples
containing ammonia. Orion specifications and environmental considerations
were used as a guide.
Monitor readings were compared with the ammonia of samples determined
using analytical procedures from Manual of Methods for Chemical Analysis
of Water and Wastes. Dr. Daniel F. Bender of the Physical and Chemical
Methods Branch of EMSL performed these determinations at first and he
later provided guidance to the author in determining the ammonia concen-
tration of wastewater samples from a waste treatment plant effluent.
Ammonia standards for most of the tests and all of the calibrations were
derived from Orion 95-10-07 ammonia standard solutions. Large volume
samples for long-term tests were prepared in-house.
Each individual test involved refurbishment of an ammonia electrode
by changing the membrane and internal filling solution. This was done to
avoid any possibility of there being undesirable characteristics to the
electrode's performance as a result of idle periods between tests. The
ammonia electrode was then installed in the monitor and operated overnight
to reach complete equilibrium with an ammonia sample-input. Calibrations
were performed the following day using the panel meter as the primary
indicator. The zero and span controls of the Leeds and Northrup (L§N)
recorder were also adjusted during calibrations for each test. Although
Orion has indicated the greatest accuracy is attained by use of the panel
meter, much of the data were derived from periods of unattended operation.
Because of this, all data were extracted from the L&N strip chart. Diffi-
culty was encountered in estimating values between the logarithmic chart
marking of the L§N recorder. To eliminate guesswork, measured values were
proportionately replaced on 8-1/2 by 10 inch, 2-cycle semilogarithmic
graph paper.
13
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AMMONIA ELECTRODE CHARACTERISTICS
The time interval required to reach chemical and thermal equilibrium
for an installation of a refurbished ammonia electrode is illustrated in
Figure 4. The resulting long-term transient requires that calibrations
be made after a 16-hour interval. Certainly, calibrations cannot be made
within a few short hours of electrode installation with any assurance of
there being sufficient accuracy for important measurements or control.
Approximate calibrations can be made within 3 hours but full calibrations
should be made within 16 hours to assure maximum accuracy. All test data
herein have been after calibration with at least 16 hours allowance to
reach complete equilibrium.
Three electrodes were tested in the ammonia monitor with ammonia
standards that covered the two logarithmic decade range of the instrument.
The specified accuracy of the ammonia monitor is ±10 percent of reading
and the lower-limit of detection is 1 ppm on the standard model (0.17 ppm
with special scale and reagents). Each of the electrodes were installed,
in turn, and the monitor was precalibrated with 10 mg/1 and 100 mg/1
standards. Standards ranging from 1 mg/1 to 100 mg/1 i^ere applied as
input to the monitor in, consecutively, decreasing and increasing concen-
trations. To establish uniformity and to assure complete electrode
response readings were recorded from the strip chart 30 minutes after
concentration changes. The longest response time, however, was encoun-
tered at the lowest-limit of detection (1.0 ppm). Therefore, these values
were taken after 60 minutes; the results are illustrated in Table 1.
100 c-
Figure 4. Ammonia electrode installation transient,
14
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Table 1. TEST OVER COMPLETE OPERATING RANGE
WITH AMMONIA STANDARDS
Ammonia standards, mg/1 (decreasing cone.)
Electrode
A
B
C
100.0
100.0
100.0
100.0
50,0
51.0
48.0
50.0
10.0
10.4
9.5
10.0
5.0
5.1
4.8
5.1
1.0
1.1
1.15
1.2
Ammonia standards, mg/1 (increasing cone.)
1
A 1
B 1
C 1
.0
.1
.15
.2
5
5
4
5
.0
.0
.6
.0
10
10
9
10
.0
.2
.5
.0
50
51
49
51
.0
.0
.0
.0
100
100
95
99
.0
.0
.0
.0
The results of this test indicate that the instrument falls slightly
short of being logarithmic over two full decades. With the exception of
the 1 ppm lower-limit of detection, however, the performance of all of the
electrodes were within Orion's specifications of ±10 percent of reading.
Depending on the accuracies desired, the instrument should be calibrated
over the decade of most interest. The error can be split between the
extremes, for instance, by calibrating with 5 mg/1 and 50 mg/1 standards.
Table 2 illustrates the results of a test to determine the slope, in
millivolts per decade change of ammonia standards, for three separate
ammonia electrodes. The ammonia electrodes were installed in the CTA of
the monitor which maintained a 20C temperature. The proportioning pump
applied standards, reagent, and airflow as usual. The electrode leads,
however, were disconnected from the monitor and applied to a Keithley
model 616, digital electrometer. A unity gain output from this instru-
ment was measured by an Esterline Angus model S601S adjustable zero and
span recorder. The results of this test indicate a difference in slope
between the lower (1 - 10 mg/1) and upper (10 - 100 mg/1) decades. The
percentage decrease in slope of the lower decade is listed for the
respective electrodes in the A percent column.
Table 2. SLOPE PER DECADE AT 20C, mv
Electrode
A
B
C
Ammonia decade change ,
1-10 mg/1 10-100 mg/1
51.2 mv 53.2 mv
49 . 5 mv 5 2 . 5 mv
49.5 mv 53.2 mv
A mg/1
A%
4 decrease
6 decrease
7 decrease
15
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Orion's specifications for response times are in terms of 90 percent
of a decade change within 8 minutes. Preliminary tests in the laboratory
have indicated response times within this interval. Without additional
transit time of the sample through strainer, filter and related tube
lengths, 90 percent response times between 5 and 6 minutes have been
observed by three electrodes. The total response time is generally within
30 minutes. However, the decade change from 10 mg/1 to 1 mg/1 results in
a total response time closer to 2 hours. Ross, et al, have derived a
model for the time response (equation 1). Gilbert and Clay have also
discussed the extended response times near the lower limit of detection,
and have related them to leaching of ammonia from the internal filling
solution reservoir. Nevertheless, one should be aware of the extended
drift interval for the total response near the lower limit of detection.
ENVIRONMENTAL STABILITY
The ammonia monitor was installed in an environmental chamber.
Shorting straps were inserted across the input to the preamplifier of the
ammonia monitor and the slope and calibrate controls were adjusted for
midscale deflection of the panel meter. This provided a suitable base
signal for testing the electronic stability. The monitor was operated
continuously under these conditions for 3 days with the environmental
chamber controlled at 20C. A ±50 niv (zero midscale) recorder was placed
on the preamplifier output (input to the L&N recorder). The drift range
was a mere 3 mv during the 3-day interval. When related to the ±2.5 VDC
output over the full scale range of the 2-logarithmic decade span of the
ammonia monitor, the drift is less than 0.1 percent for the test interval.
This small drift was not detectable on the less sensitive L§N recorder
provided with the ammonia monitor.
The electronic stability was tested next over the temperature range
5C to 42C. The zero and span controls of the L§N recorder were adjusted
at midscale and full scale. A midscale deflection was adjusted with the
slope and calibrate controls. The environmental chamber's temperature
was varied from the calibration temperatures of 20C over the 5C to 42C
range. The recorded values from the 100 mv span auxiliary recorder and
the output of the L§N recorder are listed in Table 3.
Table 3. ELECTRONIC STABILITY WITH TEMPERATURE
Temperature, C Auxiliary Rcdr., mv LSN Rcdr., ppm Remarks
20
35
42
20
5
13
39
52
13
-14
10.0
10.4
10.6
10.1
9.9
calibration
16
-------
The values of Table 3 were taken after complete stabilization of
temperature transients within several selected modules of the ammonia
monitor. These temperatures were recorded once every 2 minutes from
copper/constantan thermocouples. The maximum environmental chamber tem-
perature selected adhered to Orion's specified operating limits. The
drifts recorded by the I4N recorder were within Orion's specified accuracy
of ±10 percent of reading. Although recorded values are with preamplifier
input shorted, a thermocouple was placed within the CTA. An electrode was
installed and fluids were pumped through the system so that temperature
readings would approximate operating conditions. Overnight operation at
each chamber temperature produced stabilization of the respective modules
within the ammonia monitor,, the results are illustrated in Table 4.
Table 4. MODULE TEMPERATURE AFTER STABILIZATION
Chamber
temp. ,
C
20
35
42
20
5
20
CTA
temp. ,
C
15
19.5
24.5
15.5
14
15
Monitor
enclosure,
C
26.5
39
48
27
11.5
26.5
Electronics
module
C
29.5
42
51
30
13.5
29
L§N
rcdr . ,
C
35
49
57.5
39
22.5
36
Thermoelectric
cooler power
supply, C
39
53
58
39
24
38.5
The thermoelectric cooler and heating elements (CTA] maintained the
temperature of the electrode-holder block within a range of IOC over the
complete 37C temperature change (5C-42C). Thermal heat generated within
the L§N recorder and the thermoelectric cooler power supply resulted in
the highest temperatures recorded. Specifications for the L§N recorder
restrict its operation to ambient temperatures of 50C. The maximum
ambient temperature of 42C in this test was well within this restriction.
The operational stability of the overall system was tested at con-
stant temperature in the environmental chamber. Calibration and
restandardization solutions were derived from ammonia standards provided
by Orion. A large volume (18 liter) sample was derived from stock
solutions prepared by the Physical and Chemical Methods Branch. The
concentration of this sample was 5.5 mg/1, and it was applied as input
to the monitor for a 10-day interval. The environmental chamber was
maintained at 20C; the results are illustrated in Table 5.
17
-------
Table 5. SYSTEM STABILITY AT 20C
Day
1
2
3
4
5
6
7
8
9
10
UN
rcdr. ,
ppm
5.1
5.2
5.1
5.2
5.1
-
-
5.1
5.0
5.4
5.4
Colorimetric L§N rcdr. overnight
determinations extremes, ppm Restandardization,
mg/1
5.5
5.4
5.4
5.5
5.4
-
-
5.6
5.5
5.5
5.5
Minimum
5.1
5.1
5.2
5.1
5.1
5.1
5.0
4.9
5.1
5.2
Maximum
5.2
5.2
5.4
5.1
5.3
5.3
5.2
5.0
5.5
5.4
y amperes
0
0
0
-1
-I
-
-
-1
-1
0
-1
A sample removed each day was analyzed colorimetrically by nessleri-
zation and spectrophotometric determination for ammonia nitrogen
concentration. A comparison reading from the LdN recorder was taken at
the same time. The minimum and maximum daily extremes were recorded in
the intervening period, while discounting a 2-hour period for restand-
ardization and the resultant transient response involved. During
restandardization, 10 mg/1 is applied to the monitor under the control of
a timer. If a deviation from midscale is encountered, a servo motor
automatically feeds back a signal to return the meter deflection to mid-
scale. A restandardization meter measures the current in microamperes
that results from these corrections. Nesslerization readings were
consistently higher than the monitor readings, but the monitor was always
within 10 percent. It is interesting to note that the lowest minimum and
maximum values, listed on the eighth day, resulted in a correction that
improved the accuracy of the monitor the following day.
The system stability was observed while varying the temperature of
the environmental chamber over the range of 5C to 42C. The monitor was
calibrated at 20C. Standards of 10, 50, and 100 mg/1 were measured by
the monitor at .each temperature. A large volume sample (18 liters) was,
again, derived from laboratory stock solution for continuous measurement.
Colorimetric determinations of the sample were made after extreme tempera-
ture changes to assure that the ammonia concentration remained stable.
The resulting data are illustrated in Table 6.
The minimum and maximum values indicate the overnight drift extremes
during transients as a result of temperature changes. The L&N recorder
column, however, were sample concentrations recorded after temperature
stabilization and restandardization. The 10, 50, and 100 mg/1 standards
were also measured after stabilization. Estimates were made, where
possible, for the 100 mg/1 standard which deflected beyond full scale
i'8
-------
Table 6. SYSTEM STABILITY OVER THE TEMPERATURE RANGE 5C TO 42C
Day Temp. , C.
20
1 5
2 5
3 5
20
4 35
5 42
6 20
L5N
rcdr . ,
ppm
5.6
5.4
5.5
5.4
5.S
5.3
5.3
5.3
Colorimetric
determination Standards on L6N
mg/1 10 mg/1
6.0 10
-
-
9.9
5.S 9.8
9.7
9.9
5.9 9.6
50 mg/1
52
-
-
S3
52
53
56
52
rcdr.
100 mg/1
100
-
-
F.S.(106)
F.S.(IOS)
F.S.(IOS)
F.S.
F.S. (104)
Overnight
Minimum
-
S.O
5.4
5:2
-
5.0
5.1
3.9
extremes, ppm
Maximum
-
5.6
5.5
5.3
-
5.3
6.0
5.9
(F.S.) throughout most of the test. All of the other measurements, sample
and standards, remained within 10 percent of their original values over
the full 5C-42C temperature range.
FIELD SAMPLE MEASUREMENT
At this juncture, the ammonia monitor was prepared to accept samples
characteristic of those encountered in the treatment of sewage. Orion
supplies a filter panel that was mounted on the exterior of the monitor
cabinet. Included are valves, a 0.22 micron millipore filter, and a 0-10
ml per minute sampling pump. The majority of the sample is by-passed
across the face of the filter to waste. This continuously flushes parti-
cles away, preventing a build-up of materials that could clog the filter.
A small volume (5 ml) of sample is pumped through the filter to a constant
head chamber within the monitor cabinet. The life of the filter depends
on the rate of flow past the outer surface of the filter element, thus,
it is important that a pressure of 20-25 psi be maintained at the input.
The sample- needs to be strained before entering the filter to prevent
the passage of particles greater than 1/32 inch diameter. To accomplish
this, Orion provided a reworked PVC "Y" strainer in a self-cleaning con-
figuration. Self-cleaning takes place by returning 80 percent of the
sample through a bypass in the strainer to waste. The strained sample
(20%) is passed on as input to the filter panel. Figure 5 shows a cut-
away of the PVC "Y" strainer.
19
-------
Ml - 14 NPT or 1/4 socket (2 places)
RAW SAMPLE
IN (100%)
cap of strainer with .50"
hole drilled thru, and
face counter bored
PVC collar, solvent bonded
to cap, for support
W. schedule 80, PVC pipe
solvent bonded to cap and
collar, used to make conn-
ections to by-pass leg of 'Y'
STRAINED SAMPLE
OUT (20%)
\
-14 NPT (optional)
RAW SAMPLE
OUT (80%)
Strainers that may be reworked
like this are:
Y-type sediment strainer
Yz inch PVC
Hay ward Mfg. Co. YSI-50
or Harvel Plastics, Inc.
Figure 5. PVC "Y" strainer (courtesy
of Orion Research Incorporated).
A pump was selected to continuously recirculate a sample. In the
past, tests that required recirculating a sample were troublesome because
pumps with suitable horsepower ratings to maintain Orion requirements of
pressure and flow, imparted both an undesirable temperature rise and rust
to the sample. Lower horsepower pumps with plastic and rubber materials,
used as an alternative, were marginal in their ability to maintain suit-
able line pressures. A 1/2 hp Deming centrifugal pump with 3/4 inch pump
discharge was instrumental in overcoming these problems. An extended
shaft with a neoprene coupling reduced the temperature rise imparted from
the motor. A corrosion resistant glass-reinforced, polyester casing
and impeller eliminated the rust problem. The apparatus used for the
test of a field sample is illustrated in Figure 6. Valve V^ is throttled
down to obtain the 20 - 25 psig on the pressure gauge.
20
-------
filter pane!
sampling and
priming port
DEWING MOTOR/PUMP ASSEMBLY
Figure 6. Field sample test apparatus.
A sample was collected, prior to chlorination from the secondary
clarifier of the Muddy Creek Sewage Treatment Plant, Cincinnati, Ohio.
Heavy rainfall the previous night resulted in infiltration, such that the
ammonia concentration was below the 1 ppm lower limit of detection of the
monitor. The purpose of this final laboratory test was to compare the
readings of the ammonia monitor with those obtained by distillation and
titration of the standard method. The effluent sample was recirculated
through the 95 liter (25 gallon) tank shown in Figure 7. This was spiked
with ammonium chloride to cover a range of values for the distillation/
titration procedure for NHj - N/l. After equilibrium was reached with
each spiking, samples were taken from within the tank, at the source, and
after transit through strainer and filter. The ammonia concentration of
these samples, determined by the standard method, represents the effect
of straining and filtering under steady-state conditions. The corre-
sponding monitor readings enable determining the accuracy of the ammonia
monitor as a function of the standard method. The results are illustrated
in Table 7.
21
-------
Table 7. LABORATORY TEST WITH SECONDARY EFFLUENT WASTE
FROM THE MUDDY CREEK WASTE TREATMENT PLANT
Distillation/titration.
mg/1 NH3-N/1
source
filtered
Monitor response, Percent Percent
mg/1 NH3-N/1 source filtered
3.92
7.77
11.34
IS.96
21.00
24.40
3.71
7.28
10.86
15.12
19.70
24.20
3.3
7.0
10.8
15.1
20.0
25.0
Averages
84
90
95
95
95
102
93.5
89
96
99
100
102
103
98
The data of Table 7 indicates a favorable steady-state response of the
ammonia monitor when compared with the standard method. All except the
first comparison are within Orion's specifications of ±10 percent of
reading. The data also suggests there is a 5-percent loss of ammonia
across the strainer and filter.
At this point, assistance from Dr. Bender was interrupted because he
was obliged to prepare a paper. All subsequent chemical procedures were
performed by the author with guidance from Dr. Bender. Another sample
was obtained from the Muddy Creek Treatment plant and this time, naturally
occurring ammonia was present. The sampling point was at the tank source.
After determining the ammonia concentration the sample was spiked so that
two more comparisons could be made. The results were similar to those of
Table 7 and are illustrated in Table 8.
Table 8. ADDITIONAL SAMPLE FROM THE MUDDY CREEK
WASTE TREATMENT PLANT
Distillation/titration
mg/1 NH3 - N/l
Monitor response Percent
mg/1 NH3 - N/l source
Remarks
11.69
16.45
22.05
10.8
15.2
20.0
92
92
91
unspiked
spiked
spiked
22
-------
SECTION 6
FIELD INSTALLATION OF THE AMMONIA MONITOR
PRELIMINARY ARRANGEMENTS
Mr. Gerald G. Seymour, Assistant Superintendent of the Division of
Operations, Metropolitan Sewer District, Cincinnati, Ohio, was most help-
ful in selecting a sewage treatment plant where the ammonia monitor could
be installed. Two locations, each with secondary treatment, were visited.
The Sycamore plant, employing contact stabilization, provided a readily
accessible shelter for the monitor but it was remotely located insofar as
sample pick-up was concerned. The Muddy Creek Sewage Works, an activated
sludge plant, was selected because of convenience in sampling. Shelter
for the ammonia monitor,, however, needed to be provided at this location.
Shelter requirements were met by the National Field Investigation
Center (NFIC) of EPA in Cincinnati, Ohio. Carl Hirth of NFIC obliged by
providing a mobile van. The van installed at the Muddy Creek plant is
shown in Figure 7. It is adjacent to a sewer located on the conduit from
the secondary clarifier to the chlorine contact tank. The van serves as a
mobile chemistry laboratory, and it includes an air conditioner, cabinet,
sinks, refrigerators, intake and exhaust fans, and an electrical power
panel. The electrical power panel services the aforementioned appliances
and benchtop terminal strips. Many of these features were quite useful
in conducting the field investigation of the ammonia monitor.
SAMPLE INTAKE
Initially a 3/4 hp Jabsco pump was placed within the van, but its
seal failed and another arrangement was pursued. A Jabsco model 12490-09,
a totally enclosed 3/4 hp pump, was placed in operation outside the van.
Figure 8 shows the suction line entering the grating access to the sewer.
The output line feeds the monitor in the van. This arrangement worked
successfully during the interval data were collected at this location.
At the conclusion and prior to moving to the primary effluent, however,
this pump also failed. Apparently, a particularly turbid sample was
collected when the flow decreased such that the inlet strainer sank to
bottom sediments. Figure 9 shows the intake removed from the sewer after
this failure. A plastic strainer is shown attached to the end of the
intake hose. The cylinder protruding is the inlet strainer for the ISCO
sampler used for collecting samples for the laboratory analysis. Thus,
the monitor and sampler intakes, as nearly as possible, represent the
same sample.
23
-------
Figure 7. Mobile van installed
at Muddy Creek Treatment Plant.
• *
:-
Figure 8. Intake pump installation.
Figure 9. Inlet strainer after
test.
Figure 10. PVC "Y" strainer and
associated components.
24
-------
Figure 10 shows the PVC "Y" strainer and associated components on the
inlet line to the monitor. Apparently, the by-pass valve (lower right of
the photo) was the initial point of failure. Clogging of this valve with
sludge from the bottom sediment resulted in a reduction in sample pumped.
This resulted in the pump overheating, but prior to this the inlet pres-
sure to the filter increased excessively, thus, rupturing it. The
unfiltered sludge was pumped through to the 0.032 teflon tubing of the
ammonia monitor, eventually clogging the tubing coiled about the CTA.
Data were collected prior to this, however, to illustrate the performance
of the monitor at this location. Plans to sample at the primary effluent
were cancelled because of this failure.
SAMPLE COMPARISON
The purpose of this installation was to observe, on a short-term
basis, the ability of the ammonia monitor to continuously measure the
ammonia concentration of secondary sewage treatment effluent as compared
to sampled values by the standard method of distillation and titration.
As only a small number of comparison wastewater samples were analyzed at
a single location, this is not intended as a complete and comprehensive
investigation. It is, however, a demonstration of the ability of the
ammonia monitor to perform the measurement of a wastewater effluent. In
addition, following the recommended sample handling practices of Orion,
it was intended to observe the performance under the expected variation
in solids content of the samples encountered. In this respect Orion
and future users may be aware of the pitfalls encountered.
Apparatus for four distillations were set up in the laboratory at
1014 Broadway, Cincinnati, Ohio. Samples were picked up at the treatment
plant and transported to the laboratory each day. These samples were
collected at timed intervals by an ISCO model 1391 water and wastewater
sampler. At each 3-hour interval, a 500 ml sample was collected through
the suction line strainer enclosed within the plastic-intake strainer
previously described. The ISCO container was iced and sulfuric acid was
added to each sample bottle to inhibit overnight changes in ammonia
concentration. Table 9 lists the data collected for this test. Little
difficulty in correlating the timed samples to the chart intervals of
the monitor recording was encountered. This was because the changes in
ammonia concentration recorded were gradual and over long intervals.
Samples 2E and 4E were consecutive samples taken under nearly identical
conditions. Sample 2E was determined the same day, whereas, sample 4E
was iced overnight and determined the following day. Samples IF and 3F
were determined similarly. The preservation, therefore, did not result
in a significant difference after overnight storage.
25
-------
Table 9. COMPARISON OF AMMONIA MONITOR FIELD INSTALLATION DATA
WITH LABORATORY ANALYSIS BY THE STANDARD METHOD
Ammonia Difference
Sample Ammonia standard monitor - j. _ Monitor inf)
number monitor, mg/1 method, mg/1 standard "s ~ standard
4A 2.3 1.9 0.4 121.0
6A 3.1 2.3 0.8 134.8
8A 2.4 2.0 0.4 120.0
22B 7.5 8.3 -0.8 90.4
IOC 5.1 4.7 0.4 108.5
11C 5.5 5.5 0.0 100.0
13C 4.6 4.8 -0.2 95.8
14C 3.6 4.2 -0.6 85.7
17C 7.4 7.1 0.3 104.2
20C 2.7 4.1 -1.4 65.8
12C 3.4 . 3.6 -0.2 94.4
13C 3.0 3.3 -0.3 90.9
IE 3.6 3.5 0.1 102.9
2E 3.6 3.4 0.2 105.9
4E 3.5 3.0 0.5 116.7
12E 9.2 9.0 0.2 102.2
13E 1.3 1.3 0.0 100.0
14E 7.8 7.5 0.3 104.0
19E 2.2 1.4 0.8 157.1
24E 2.0 1.6 0.4 125.0
26E 3.2 2.8 0.4 114.3
IF 2.3 2.2 0.1 104.6
SF 2.3 2.3 O.Q 100.0
1.8 2444.2
mean diff. =0.08
mean % standard = 106.3
Assuming that the standard method is, indeed, superior to the
ammonia monitor results, statistical methods^ were employed. The objec-
tive is to determine if there is a difference between the standard method
and the monitor data of Table 8. Let y^ and ys be the average ammonia
concentration determined by the monitor and the standard method, respec-
tively. Then the null hypothesis, Ho, is that y^ = ys> or that their
difference is zero. The alternative, HI, is that y^ £ VQ, or that their
difference is not zero. Assuming the populations normal, and tested at
the 0,05 level of significance, it was concluded that H0 could not be
rejected. The two methods, therefore, were not seen to be significantly
different.
26
-------
A regression analysis was performed with the data of Table 8. The
estimate of the regression line is illustrated in Figure 11 and is deter-
mined from comparison readings over the period of the test. The 95
percent confidence interval of the mean response is included. The
standard deviation is 0.4919, with an estimated correlation coefficient
of 0.974.
4 6 8 10
AMMONIA (STANDARD METHOD), mg/l
Figure 11. Regression line with 95 percent confidence limits for the mean
response.
27
-------
DISCUSSION
The field installation of the ammonia monitor accomplished the
intended objectives of observing the monitor's performance as compared
to sampling by the standard method and observing Orion's recommended
technique in sample handling on the input. Figure 12 shows that 65
percent of the monitor readings were within ±10 percent of the stan-
dard method values.
0.30
o
UJ
8
LU
ac
0.20
0.10
65
85 95 105 115 125 135
MONITOR-PERCENT OF STANDARD METHOD
155
Figure 12. Relative frequency histogram.
28
-------
Improvement would be desirable in the sample handling requirements
of the ammonia monitor. During the interval in which data were collected,
heavy flow and moderate amounts of solids were encountered. Weekly back-
flushing of the by-pass strainer resulted in successful operation. Later
a reduced flow caused a lowering of the intake such that bottom sludge
was pumped. This resulted in clogging of the by-pass valve, rupture of
the filter, and failure of the pump. The sludge was passed on into the
small diameter tubing within,the monitor, eventually clogging it. Present
requirements to throttle down the by-pass valve (to obtain 20 - 25 psi on
pressure gauge) results in a small bore opening in the valve to waste.
This small opening is vulnerable to clogging and it requires periodic
flushing and the avoidance of excessive solids at the intake. With the
present sample handling, intake placement must be planned carefully to
reduce the likelihood of pumping solids. Preventive maintenance requires
that-the strainer be back-flushed as often as necessary depending on the
sample characteristics.
A problem area within the ammonia monitor, warranting examination by
Orion, is the transport of liquid-sample/reagent through the coiled tubing
about the electrode holder. Blockage can presently occur from failures
resulting in solids breakthrough into the monitor or in interruptions of
the normal flow of liquids. In either case, solidification can occur
within the tubing. When these blockages do occur, the complete electrode
holder assembly .needs to be replaced. A redesign or modification, possi-
bly taking advantage of the electrode's measurement of ammonia in the
gaseous state, would be desirable. That is, Orion might consider the
transport of gaseous ammonia, rather than liquids, through the tubing
into the CTA.
29
-------
REFERENCES
1. Zadorojny, C., S. Saxton, and R. Finger. Spectrophotometric
Determination of Ammonia. JWPCF, 45, 5, p. 90S, May 1973.
2. Hanson, A. M. and G. F. Lee. Forms of Organic Nitrogen in Domestic
Wastewater. JWPCF, 43, 11, p. 2271, November 1971.
3. Earth E. F., and R. B. Dean. Nitrogen Removal from Wastewaters. In:
Proceedings of Advanced Waste Treatment Water Reuse Symposium, Envi-
ronmental Protection Agency, Washington, D.C., "1971.
4. Manual of Methods for Chemical Analysis of Water and Wastes. Tech-
nology Transfer, p. 159, STORET NO. 00610, U.S. Environmental
Protection Agency, Washington, D.C., 1974.
5. American Public Health Association, Standard Methods for the Exami-
nation of Water and Wastewater, 13th Edition, p. 222, Method 132,
New York, 1971.
6. ASTM Standard, Part 23, Water; Atmospheric Analysis, p. 368, Method
D1426-58, 1973.
7. Thomas, R. F., and R. L. Booth. Selective Electrode Measurement of
Ammonia in Water and Wastes. Environmental Science and Technology,
Vol. 7, p. 523, June 1973.
8. LeBlanc, P. J., and J. F. Sliwinski. Specific Ion Electrode Analysis
of Ammonium Nitrogen in Waste Waters. American Laboratory, Vol. 5,
No. 7, p. 51, July 1973.
9. Gilbert, R. R., and A. M. Clay. Determination of Ammonia in Aquaria
and in Sea Water Using the Ammonia Electrode. Analytical Chemistry,
Vol. 45, No. 9, p. 1757, August 1973.
10. Srna, R. F., C. Epifanio, M. Hartman, G. Pruder, and A. Stubbs. The
Use of Ion Specific Electrodes for Chemical Monitoring of Marine
Systems. College of Marine Studies, University of Delaware (DEL-SG-
14-73), June 1973.
11. O'Herron, R. J. Investigation of the Orion Research Cyanide Monitor.
EPA 670/4-75-005, U.S. Environmental Protection Agency, Cincinnati,
Ohio, April 1975.
30
-------
12. Ross, J. W., J. H. Riseman, and J. A. Krueger. Potentiometric Gas
Sensing Electrodes. Pure and Applied Chemistry, Vol. 36, p. 473,
1973.
13. Benner, P. E. Direct-Energy Conversion. Standard Handbook for
Mechanical Engineers, Baumeister and Marks, Editors, 7th Edition,
McGraw-Hill, New York, 1967.
14. Walpole, R. E. and R. H. Myers. Probability and Statistics for
Engineers and Scientists. The Macmillian Company, New York, 1972.
31
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/4-77-028
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
INVESTIGATION OF THE ORION RESEARCH AMMONIA MONITOR
5. REPORT DATE
May 1977 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert J. O'Herron
8. PERFORMING ORGANIZATION REPORT NO.
9, PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Monitoring and Support Lab.
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
- Cin., OH
10. PROGRAM ELEMENT NO.
1HD621
11. CONTRACT/GRANT NO.
In-House
12. SPONSORING AGENCY NAME AND ADDRESS
Same as above
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/06
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Orion Research ammonia monitor was investigated using the Orion specifications
and environmental considerations as a guide. Laboratory tests under controlled envi-
ronmental conditions showed the electronic stability (drift) to be well within ±10
percent of reading over the temperature range 5C to 42C. Sensor stability over the
temperature range 5C to 42C was tested by applying ammonia nitrogen (standard solu-
tions of 10 mg/1, 50 mg/1, and 100 mg/1) as direct input to the monitor. The results
of these tests showed that automatic restandardization maintained readings within
Orion's specified tolerance of ±10 percent of reading.
Dynamic on-stream measurements were made of a secondary sewage treatment plant
effluent in a field installation. These measurements were periodically compared with
those of the standard method of distillation and titration. Sixty-five percent of
these comparisons were within ±10 percent of reading. Steady-state comparisons were
made of field-collected samples with the standard method for determining ammonia
nitrogen. It appeared, from these tests that a 5 percent loss in ammonia concentra-
tion resulted from the required straining and filtering of the sample input to the
monitor. Eight of the nine samples compared were within 10 percent of the standard
method.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lOENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Anunino compounds, Ammonia, Electrodes,
Test chambers, Environmental tests,
Measuring instruments, Monitors,
Performance evaluation, pH, Samples,
Sewage treatment, Specifications,
Waste treatment
Gas-sensing electrodes,
Industrial effluent,
Dsmotic strength, rea-
gent additions,
Suspended solids, Total
concentration
13B
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
40
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
32
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