Environmental Protection Technology Series
SUSPENDED SOLIDS MONITOR
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-670/2-75-002
April 1975
SUSPENDED SOLIDS MONITOR
By
John W. Liskowitz
Newark College of Engineering
Newark, New Jersey 07102
Gerald J. Franey
Joseph Tarczynski
American Standard Inc.
New Brunswick, New Jersey 08903
Contract No. 14-12-494
Project No. 11024DZB
Program Element No. 1BB034
Project Officer
Allyn St. C. Richardson
U.S. Environmental Protection Agency
Region I
Boston, Massachusetts 02203
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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REVIEW NOTICE
The National Environmental Research Center—Cincinnati
has reviewed this report and approved it for publication.
Approval does not signify that the contents necessarily re-
flect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation
for use.
ii
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FOREWORD
Man and his environment must be protected from the adverse
effects of pesticides, radiation, noise and other forms of pollu-
tion, and the unwise management of solid waste. Efforts to
protect the environment require a focus that recognizes the inter-
play between the components of our physical environment—air,
water, and land. The National Environmental Research Centers provide
this multidisciplinary focus through programs engaged in
o studies on the effects of environmental
contaminants on man and the biosphere, and
o a search for ways to prevent contamination
and to recycle valuable resources.
Both of these objectives require instrumentation to measure
pollution and its effects, and to control the processes used to
prevent discharge of pollutants to the environment and to recover
reusable resources. The instrument described herein is expected
to find application for all of these needs.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center -, Cincinnati
111
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ABSTRACT
A method for measuring concentration of suspended solids in liquid
media, based on depolarization of backscattered polarized light, has
been developed and instrumented. Feasibility studies and field evalu-
ation of the instrument, using sewage influent, effluent and sludge,
showed that there is a specific relationship between concentration of
solid particles and polarization ratio. It was also shown that the
relationship is independent of size distribution and density of par-
ticles, color of particles or solution, sludge consistency, velocity,
and build-up of solids on the optical window. The field evaluation
results indicate that this instrument provides a continuous instan-
taneous in situ measurement of suspended solids concentrations in com-
bined sewers and other wastewater flows.
This report was submitted in fulfillment of Project No. 11024DZB,
Contract No. 14-12-494 by American Standard Inc. under the sponsor-
ship of the U.S. Environmental Protection Agency. Work was completed
in August, 1970.
IV
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CONTENTS
Page
Abstract iv
List of Figures vi
List of Tables vii
Acknowledgments viii
Sections
I Conclusions 1
II Recommendations 2
III Introduction 4
IV Design of Experiments 7
V Laboratory Evaluation of Feasibility 9
VI Design of Model for Field Tests 26
VII Field Evaluation 30
VIII References 36
IX Publications and Patents 37
X Appendix 38
v
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FIGURES
No. Page
1. Optics Diagram 5
2. Polarization Ratio vs. Gravimetric Suspended 10
Solids Measurement - 5.5 cm Optical Path
3. Intensity of Backscattered radiation vs. Gravimetric 12
Suspended Solid Measurement - 5.5 cm Optical Path
4. Polarization Ratio vs. Gravimetric Suspended Solids 13
Measurement - 2.3 cm Optical Path
5. Log Polarization Ratio - 5.5 cm Optical Path 14
6. Log Polarization Ratio - 2.3 cm Optical Path 15
7- Refractive Index vs. Dissolved Solids Concentration 19
8. Thermogravimetric Analysis of Dissolved Solids in 21
Bernardsville and Middlesex Influent
9 • Absorption Spectra of Influent Filtrate 22
10 • Optical and Mechanical Components of Suspended 27
Solids Monitor
11. Developmental Suspended Solids Monitor System 28
12. Polarization Ratio vs. Gravimetric Suspended Solids 32
Measurement, Perth Amboy Sewage Treatment Plant
13- Polarization Ratio vs. Gravimetric Suspended Solids 33
Measurement, Perth Amboy Sewage Treatment Plant,
Heavy Oil Contamination
14. Log Polarization Ratio vs. Gravimetric Suspended 35
Solids Measurement, Perth Amboy Sewage Treatment
Plant
vi
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TABLES
No. Page
1. Characterization of Bernardsville and Middlesex 16
Influents
2. Effect of Color on Total Backscattered Light 18
3- Total and Volatile Dissolved Solids in Bernardsville 20
and Middlesex Influents
4. The Effect of Solid Deposits on Polarization Ratio 23
and Total Backscattered Light
5. Flow vs. Polarization Ratio 25
6. Field Evaluation Data for Suspended Solids Monitor 31
vii
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ACKNOWLEDGMENTS
The authors wish to acknowledge the many helpful discussions
with William Hodes, and the assistance of Patrick Duffy of the
Perth Amboy Sewage Plant, and R. L. Buckingham of the Bernardsville
Sewage Plant. In addition, we would like to thank R. A. Rowe and
Sam Capano of the Middlesex County Sewage Treatment Plant for the
collection of samples. We especially wish to thank Allyn Richardson
for his guidance throughout this investigation.
viii
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SECTION I
CONCLUSIONS
1. The feasibility study indicates that using the depolarization
measurement to monitor concentration of suspended solids in sewage
samples gives more closely repeatable results than standard gravi-
metric methods, and correlates well with them.
2. Suspended solids concentrations ranging from a few mg/1 to at
least 5000 mg/1 can be measured using the depolarization technique.
3. The relationship between the polarization ratio and concentration
of suspended solids in sewage samples has been shown to be sub-
stantially invariant for the range of particle size and density
encountered in sewage.
4. The relationship between the polarization ratio and concentration
of suspended solids is unaffected by sample source (industrial,
domestic sewage, treatment plant influent, effluent or sludge).
5. Depolarization measurements are valid indicators of suspended
solids concentration in the presence of organisms and aggregates
generally found in sewage sludge.
6. Neither rate of flow of the sewage past the optical window nor
buildup of solids deposits on the optical surfaces affect the
polarization ratio measurement, provided that light intensity is
above the response threshold of the detectors.
7. In the sewage treatment plant, at Perth Amboy, New Jersey, which
receives a substantial flow and diversity of industrial wastes,
a specific relationship was found between suspended solids con-
centration and polarization ratio, which held for combined -
sewer influent, storm water overflow, and plant effluent.
8. The instrument can be used to monitor suspended solids in treat-
ment plant influent and effluent, in the presence of contamina-
tion such as oil or soap suds, which affect the gravimetric
determinations or in highly colored solutions.
9. The data indicate that a higher degree of repeatability is
attained by depolarization measurements than by gravimetric
measurements.
10. The present model will operate in any type of sewage environment.
It requires a 120 VAC power source. During measurements the
present instrument requires attention for adjustments in electro-
nics. A design change recommended in the RECOMMENDATIONS Section
should eliminate this problem.
11. Linearization of the response function of the suspended solids
monitor over several decades of suspended solids concentration
shows promise if use is made of the logarithm of the polarization
ratio and an optical path longer than 5.5cm (2.17 inches).
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SECTION II
RECOMMENDATIONS
Since resources available under this contract were exhausted
after very limited field testing of the model, a program of continued
testing is recommended. This program would have two major objectives;
to establish the optical measurements as a valid indicator of suspended
solids under as wide a range of conditions (waste parameters, ambient
light, time since maintenance, etc.) as possible, and to determine the
optimum design parameters for instruments tailored to operate in
specific ranges of suspended solids concentration and environmental
conditions.
Following this study (and contingent upon a favorable evaluation
of its results) a further development should be undertaken, using the
new information produced by the study and incorporating three changes
first suggested by the Environmental Protection Agency Project Officer
when reviewing design of the present model:
1. In place of the mechanical chopper, use an electronically
modulated light source, such as a sinusoidally-modulated
or pulse-modulated gas discharge tube.
2. Eliminate the separate measurement of background illumination
and the analog computation necessitated thereby, by AC
coupling the light sensor and pulse amplifier. This also
eliminates troublesome sensor drift problems, permits
operation of the sensor photodiodes in the photoconducting
mode rather than the narrow-dynamic-range photovoltaic mode,
avoids the need for manual adjustment to changing ambient
light levels, and provides substantial advantages in re-
liability, size, and cost.
3. Use the polarization ratio EM - E( as the measure, rather
E,t + EA
than degree of depolarization E± /E|( as was used in earlier
work. As detailed in Section VI, the logarithm of this
polarization ratio should relate linearly to suspended
solids concentration. Further theoretical and empirical
linearization effort, as needed, should be included in the
next development.
This further development will provide an instrument that can be
installed in collection lines or at the plant to monitor in-situ the
suspended solids concentration in municipal sewage influents and
effluents and in combined storm sewer overflows. This will provide
instantaneous intelligence signals that can be used to automate and
control waste treatment operations and regulate and minimize combined
storm sewer overflows.
Field evaluation of this instrument should be carried out using
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a system such as the test facility developed by FMC Corporation, Santa
Clara, California (1), where the concentration of suspended solids can
be regulated and defined accurately. Field evaluation of the monitor
in actual waste streams using grab sampling techniques does not provide
the representative samples to which the monitor is continuously re-
sponding.
Fiber glass filters rather than membrane filters should be used
for the gravimetric determination of suspended solids concentrations
in waste streams when correlating this determination with the readout
of the suspended solids monitor. The use of membrane filters can lead
to errors in the gravimetric determination. The membrane filters were
observed in a recent investigation (2) to remove both suspended and
dissolved solids; whereas, the fiber glass filter removed only the
suspended solids.
As an accessory to the suspended solids monitor, the possibility
exists that a differential refractive index measurement can be developed
to monitor in-situ the dissolved solids (organic plus inorganic) on a
continuous basis. This differential instrument used in conjunction
with the suspended solids monitor can further characterize the waste
stream by providing a continuous measurement of total solids in a
waste stream.
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SECTION III
INTRODUCTION
A novel method, based upon the depolarization of scattered light,
has been developed in our laboratories for the rapid and continuous
determination of the concentration of particles in suspensions. This
approach has been shown to respond to a greater concentration range
of particles and is less dependent on particle size than the commonly
used transmission and light scattering techniques (3). A polarization
ratio serves as a measure of the degree of depolarization of scattered
light. This ratio is readily determined by the measurement of the
intensity of scattered radiation passing through a polarizing prism
with its optical axis perpendicular (E±) and parallel (EM) to the
plane of incident polarized light (see Figure 1). The ratio of in-
tensities, E(| - E± represents the polarization ratio.
E,, + Ex
In a solution containing particulate matter, incident light
scattered by the individual particles (primary scattering) is in turn
rescattered by other particles. This phenomenon is known as multiple
scattering. It is known that as the concentration of the particulate
matter in solution is increased, multiple scattering also increases.
Thus, the fraction of backscattered light which has been multiply
scattered should increase with concentration of scattering particles.
It is possible to devise an optical system, using polarization
techniques, to measure the degree of multiple scattering. This con-
sists of a collimated source of plane polarized light illuminating
the suspension to be measured, and a collimated light sensor "looking"
at a zone of illuminated suspension, accepting light which has been
scattered through a deflection angle of close to 180 degrees, say
170 degrees. The sensor is located so that the plane of this deflec-
tion beam is perpendicular to the plane of polarization of the in-
cident light, as shown in Figure 1. The sensor is equipped with a
plane polarizing device, permitting measurement of the energy com-
ponents of the light it receives in the polarization planes parallel
to the incident polarization plane (EM) and perpendicular thereto (E ).
With this optical configuration, light which has been scattered only
once (primary scattering) will not exhibit any energy in the EX
component; that is, there will be no depolarization. Multiple
scattering, however, through various deflection angles in random
planes aggregating 170 degree in the required plane, will be depolari-
zed (4).
The measurement parameter used herein is (EM - Ej_)/(En+ E^) ,
which defines the polarization ratio, P- At very low concentration
of suspended particles, virtually all the light reaching the sensor
will be from primary scattering, and multiply-scattered illumination
of the sensor will be negligible. As these conditions are approached,
E± will approach zero, and therefore the ratio P will approach unity.
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WINDOW
LENS AND
POLARIZER
CHOPPER
LIGHT SOURCE
Ex DETECTOR
E, ANALYZER
LENS
BEAM SPLITTER
E,, ANALYZER a
LENS
E,, DETECTOR
FIGURE 1 - OPTICS DIAGRAM
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The other extreme, approached at very high, concentrations of suspended
solids, is complete randomization by- multiple scattering with E^
approaching equality to E([ » and therefore P approaching zero.
There may be some preference for a parameter which increases
monotonically with increasing suspended solids, and we may define a
depolarization ratio D, equal to 1-P» which will traverse the range
0 to 1 as suspended solids concentration changes from zero to infinity.
This parameter, however, is unsuited for linearization by the logarith-
mic relationship proposed below.
Without undertaking rigorous treatment of the theory involved, we
propose that the decrement dP in degree of polarization resulting from
an incremental increase in solids concentration dC should be proportion-
al to the remaining degree of polarization P, That is,
f - •* a)
where k is a positive constant of proportionality- This has the
familiar form of a logarithmic relationship.
f1 = -kdC (2)
LnP = -kC + const. (3)
Evaluating the const., when P
const. = 0, and we are left with
1, then C = 0, and therefore
The experimental results give some evidence of linearity of the
relationship between -Log P and C. Further work as recommended will
confirm or refine these assumptions.
Object of Investigation
The first objective of the investigation was to verify the
feasibility of the measurement of depolarized backscattered radiation
as a method of determining concentration of solid particles in an
aqueous suspension. The second objective was to construct a proto-
type instrument which would continuously monitor suspended solids in
flowing sewage systems.
In pursuing these objectives, some unexplored parameters were
investigated to prove feasibility. The instrument was designed to
accommodate these parameters. Factors considered in feasibility,
and in design, will be discussed briefly.
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SECTION IV
DESIGN OF EXPERIMENTS
Parameters Investigated
Previous depolarization measurements (3) on model hydrosol systems
proved that the degree of depolarization is dependent upon the ratio of
the refractive index of the solid to that of the medium and upon the
volume concentration of particles in suspension. Correlation of de-
polarization with weight concentration is obtained by measuring the
density of the solids. Selection of the wavelength of incident radia-
tion so that it is comparable to, or smaller than, the size of the
smallest particles to be measured in the sewage will reduce the effect
of particle size upon the determination.
Thus devising a technique using the depolarization of backscattered
polarized radiation for monitoring the amount of the suspended solids
in combined sewer overflows and other storm or wastewater flows in-
volves as significant parameters the size distribution of the suspended
solids, and the density, color variations, and refractive index ratios
of particles and mediums. These are examined in sewage samples for
their effect on depolarization. The effect of optical surfaces coated
with deposited solids and the effect of flow on the measurement, also
must be considered.
Prototype Design
The prototype includes means for remote changing of the optical
path length from 2 cm (0.8 inches) to 30 cm (12 inches) while the
suspended solids monitor is in a given sewer environment. Thus, an
optical path length can be selected that provides maximum sensitivity
for monitoring the concentration of suspended solids for a specific
environment.
The prototype also allows the depolarization measurements to be
performed in the presence of ambient light radiation. The effect of
ambient radiation on measurements is eliminated by chopping the in-
cident illumination to the sample. The receiver optics in the proto-
type measures the energy resulting from both the backscattered and
ambient radiation, and from ambient radiation alone. The backscattered
radiation energy is found by difference.
The prototype also permits the angular acceptance of the receiver
unit to be regulated; so that the levels of ambient radiation entering
the receiver can be controlled. The magnitude of the ambient radia-
tion which may result from sunlight in open channels when low con-
centration of suspended solids are monitored, can drive the photo-
diodes in the receiver unit into saturation. Hence, means to reduce
the levels of ambient radiation that enters the detector are necessary.
Analytical Procedures
Since the effect of particle size and distribution on depolari-
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zation was not known at the time this study was undertaken, the
analysis of the suspended solids in sewage was carried out by filtration
and weighing of the solids on 10}i and 0.3ji membrane filters. Particles
less than 0.3p will be mainly smaller than half the wavelength of in-
cident radiation used and for the most part will not be detected either
by the gravimetric technique using a 0.45ji membrane filter as recommended
by the EPA or by the suspended solids monitor.
It was found that the dissolved solids in sewage could be determined
directly on the unfiltered sample. A linear correlation was found be-
tween the refractive index of the solution and the dissolved solids.
A differential refractometer was used, since the difference in the re-
fractive index from that of pure water was in the fourth and fifth
decimal place.
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SECTION V
LABORATORY EVALUATION OF FEASIBILITY
Feasibility Study (Phase I)
The investigations comprising Phase I were conducted in the
laboratory, using actual sewage in place of the idealized test suspen-
sions of preproposal experiments. Two sewage sources were utilized;
Middlesex Sewage Authority's treatment plant, Middlesex, New Jersey,
where influent is composed of 50 per cent industrial and 50 per cent
domestic sewage, and Bernardsville, New Jersey Sewage Plant handling
100 percent domestic sewage. The suspended solids concentration
range covered in these experiments was from 30 mg/1 up to 4800 mg/1.
The suspended solids in the influent and effluent were from 30 mg/1
to about 400 mg/1, and the concentration in the sludge samples ranged
from about 1300 mg/1 to 4800 mg/1.
The results of the depolarization measurements in the laboratory
show that the backscattered polarization decreased with increasing
suspended solids concentration regardless of the source of the sewage
samples. The relationship between polarization and concentration of
suspended solids was found to be the same whether the sample was in-
fluent, effluent or sludge. A Bernardsville activated sludge sample
diluted with effluent to reduce its solids concentration below 400 mg/1
exhibited the same polarization ratio as the influent and effluent at
the same concentration of suspended solids (Figure 2). The Bernards-
ville plant effluent was used for dilution because it contains low
solids concentration (30 mg/1 to 40 mg/1) and it did not cause floccu-
lation of the suspended solids in the sludge. When water was used as
a diluent, flocculation of the particles occurred. The sharpest
decrease in the polarization ratio with concentration occurred below
a concentration of about 1000 mg/1, (Figure 2). These measurements
were made when the detectors were directed at the incident beam in the
center of 11 cm (4.33 inches) I.D. sample cell. Above 1000 mg/1,
there was a more gradual depolarization with increasing concentration.
At these high concentrations, complete attenuation of the incident
beam was observed before it reached the center of the sample cell. At
the low end of the concentration range, the instrument responded
satisfactorily to concentrations as low as 20 mg/1. These samples
were taken from the Bernardsville, New Jersey, sewage plant effluent.
Overhead laboratory illumination had no effect on polarization measure-
ments .
Repeatability and Scatter
The scatter in experimental data, especially at high suspended
solid concentrations as shown in Figure 2, is probably caused more by
lack of repeatability in the gravimetric determination of suspended
solids in sewage as well as the inability to obtain the samples to
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o: 07 —
z
o
N
(E
O
a.
WAVELENGTH OF INCIDENT RADIATION
POLYCHROMATIC LIGHT (WHITE)
SCATTERING ANGLE « 170°
200
400 600 800 1000 1200
SUSPENDED SOLIDS CONC, mg/l
1400 1600
O
4500 4700 4900
FIGURE 2 - POLARIZATION RATIO vs GRAVIMETRIC SUSPENDED SOLIDS MEASUREMENT, 5.5 cm
OPTICAL PATH
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which the instrument is responding than by the variability in polariza-
tion measurements or their correlation with actual suspended solids in
the size range they measure. As a basis for comparison, conventional
approaches, such as the measurement of the intesity of backscattered
radiation indicated poor correlation with the gravimetric determination
on samples taken from the Middlesex Treatment Plant (see Figure 3).
The data in Figures 2 and 3 were obtained on the same samples. A check
of the reproducibility of the gravimetric determination showed a 16
per cent range in the results of three separate determinations on the
same influent sample. Also, the suspended solids instrument provides
an instantaneous readout whereas the gravimetric determination of su-
spended solids on a number of samples required filtration times of
some ten to twelve hours. Marked variations in the correlation between
the readout and the gravimetric determinations was encountered in such
cases.
Optical Path Length
Reducing the optical path length for the polarization measurements
from 5.5 cm (2.17 inches) to 2.3 cm (0.9 inches) resulted in a more
gradual decrease in polarization with increasing concentrations below
1000 mg/1 (see Figure 4). The above findings indicate that reducing
the optical path length from 5.5 cm to 2.3 cm will lead to an increase
in the sensitivity of polarization measurements in the concentration
range above 1000 mg/1. However, the relationship between the polari-
zation ratio and concentration of suspended solids above 1600 mg/1,
using the shorter optical path lengths, was not examined; during the
measurement period the suspended solids content of sludge at both
Middlesex and Bernardsville was low. Additional data to fill this gap
are needed.
Linearization of Relationship
Replotting the data in Figure 2 according the Equation 5 (page 6)
reveals the existence of a linear relationship for the concentration
range 300 mg/1 - 1700 mg/1 using an optical path of 5.5 cm (see Figure
5). Similarly, the data in Figure 3 shows linearity for the concen-
tration range 600 mg/1 - 1700 mg/1, using an optical path of 2.3 cm
(see Figure 6). Increasing the optical path length increases the
range over which the logarithm is linear (compare Figure 5 with
Figure 6). These findings suggest that the results of the depolari-
zation measurements may be linearized at lower concentrations by
using optical paths longer than 5.5 cm.
Sample Characteristics
Analysis of the Middlesex and Bernardsville influents indicated
marked variations in the particle density and size distribution (see
Table I).
The solids in Sample No. 1 separated into two layers in the
density gradient column. These ranged from 1.20 to 1.40 g/cc and
from 1.50 to 1.59 g/cc. The solids in the remaining samples formed
11
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K>
§
M
CJ
CO
o
<
M
6.0 r
5.0
3.0
2.0
M 1.0
H
S
M
O O
O
O
WAVE LENGTH OF INCIDENT RADIATION-POLYCHROMATIC LIGHT
(WHITE) SCATTERING ANGLE = 170 DEGREES
200 400 600 800 1000 1200 1400 1600 1800 2000
SUSPENDED SOLIDS CONCENTRATION mg/1
FIGURE 3 - INTENSITY OF BACKSCATTERED RADIATION vs GRAVIMETRIC
SUSPENDED SOLID MEASUREMENT, 5.5 cm OPTICAL PATH.
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u>
Z
o
N
5:
o
O.
WAVELENGTH OF INCIDENT RADIATION'
POLYCHROMATIC LIGHT (WHITE)
SCATTERING ANGLE- 170°
200 400 600 800 1000 1200 1400
SUSPENDED SOLIDS CONG, ing/1
j
1600 1800
FIGURE 4 - POLARIZATION RATIO vs GRAVIMETRIC SUSPENDED SOLIDS
MEASUREMENT, 2.3 cm OPTICAL PATH
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o
I-
(C
z
o
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o:
o
0.
o
1.7
1.6
1.5
1.4
1.3
1.2
I.I
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
I.I
0
1
200 400 600 800 1000 1200 1400 1600
SUSPENDED SOLIDS CONC, mg/l
FIGURE 5 - LOG POLARIZATION RATIO, 5.5 cm OPTICAL PATH
1800
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200
400
600
800 1000 1200 1400 1600 1800
SUSPENDED SOLIDS CONC, mg/l
FIGURE 6 - LOG POLARIZATION RATIO, 2.3 cm OPTICAL PATH
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TABLE 1
CHARACTERIZATION OF BERNARDSVILLE AND
MIDDLESEX INFLUENTS
Sample
No. Source
1 Middlesex
2 Middlesex
3 Middlesex
4 Bernardsville
Date
Collected
5/23/69
5/27/69
7/10/69
7/15/69
Suspended
Solid
(mg/1)
275
300
476
228
Dissolved
Solid
(mg/1)
1733
1133
2236
435
Density
Range
(g/cc)
1.20-1.40
1.50-1.59
1.52-1.66
1.14-1.39
1.56-1.65
Size
Distributions
13%>54)J
19%>44u
68%>15p
6%>54n
54%>15y
10%>36y
25%>26p
38%>19n
18%>34p
43%>24y
58%>20y
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single layers that ranged in density from 1.52 to 1.66 g/cc. In compari-
son, a Middlesex influent sample collected on 5/15/69, not shown in Table I,
also formed a single layer, but ranged in density only from 1.14 to 1.39 g/cc.
The color variation in these sewage samples was quite marked. The
influent, effluent and sludge from the Middlesex plant ranged from light to
dark brown; the influent and effluent from Bernardsville ranged from white
to clear, and the activated sludge sample was black when tested in the
laboratory. The wide range of color variations is indicated by the range
of intensities of total backscattered radiation (Table 2), since color
attenuates both the incident and scattered light.
Refractive Index Measures Dissolved Solids
The results of refractive index measurements on sewage samples indi-
cate small differences between the sample and distilled water. A sample
containing 1800 mg/1 of dissolved solids exhibited a refractive index dif-
ference of only 3.7 x 10~^. However, a linear relationship was found to
exist between the concentration of total dissolved solids and increase in
(organic plus inorganic components) refractive index of the sewage sample
(Figure 7). The same relationship was found to exist, regardless of whether
the sewage samples were collected from Middlesex or Bernardsville. The dis-
solved solids in the Middlesex and Bernardsville influent was analyzed to es-
tablish this relationship. The volatile portion was found to range from 19
to 31 percent (Table 3). The fixed portion of the dissolved solids was
found by x-ray diffraction measurements to consist mainly of NaCl. Compari-
son of representative thermogravimetric curves obtained by heating Bernards-
ville and Middlesex influent indicates that organic constituents are similar
(Figure 8). Both influents exhibited inflection points between 200 and 300°C
and between 500 and 600°C. The light absorption spectra obtained for both
influents are also similar. Absorption maxima were observed at 223 mp and
275 mp (see Figure 9). Further measurements on the influent and effluent of
seven treatment plants located in New Jersey indicated that the same linear
relationship exist between the refractive index and total dissolved solids
concentration for a variety of waste streams (1). These measurements were
performed directly on the waste samples and are uneffected by the presence
of suspended solids. [The discovery that dissolved solids concentration in
sewage can be estimated by differential refractometry is interesting. As an
accessory to the suspended solids monitor, this method would provide for a
measurement of dissolved solids.]
Deposits on Optical Surfaces
A slow and irregular rate of buildup of solids was observed on the sur-
face of the beakers submerged in the activated sludge tank at the Bernards-
ville sewage plant. Six days were required before any significant deposits
were observed. These deposits were distributed unevenly and covered only a
small portion of the beaker's surface. Depolarization and backscattering
intensity measurements on the Middlesex influent, using a beaker that was sub-
merged for 42 hours, indicate that cleaning the beaker had no effect on
either depolarization or the intensity of the total backscattered radiation
(see Table 4). However, when the beaker was submerged for six days, the
17
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TABLE 2
EFFECT OF COLOR ON TOTAL BACKSCATTERED LIGHT
00
Sample
Effluent
Influent
Sludge from
Clarrifloccs
Effluent
Influent
Activated
Sludge
Source
Middlesex
Middlesex
Middlesex
Bernardsville
Bernardsville
Bernardsville
Date
Collected
6/17/69
6/17/69
6/17/69
6/13/69
6/13/69
6/13/69
Total
Backscattered
Radiation Intensity
(Millivolts)
9.97
7.28
10.83
2.41
6.43
1.79
Suspended
Solids
Ong/1)
165
379
4797
37
206
1516
Color of
Suspension
light brown
dark brown
dark brown
clear
white
black
-------
400 i—
350
300
• 250
o
x
B-
<
x 200
uj
o
UJ
>
I-
CJ
150
uj 100
tr
Z
UJ
o:
UJ
50
H, ®, A, BERNARDSVILLE SAMPLES COLLECTED
ON DIFFERENT DAYS
O.O, A, D,O. MIDDLESEX SAMPLES COLLECTED
ON DIFFERENT DAYS
200
400
1600
600 800 1000 1200 1400
DISSOLVED SOLIDS CONG, mg/l
FIGURE 7 - REFRACTIVE INDEX vs DISSOLVED SOLIDS CONCENTRATION
1800 2000
-------
TABLE 3
TOTAL AND VOLATILE DISSOLVED SOLIDS IN
BERNARDSVILLE AND MIDDLESEX INFLUENTS
Source
Middlesex
Bernardsville
Middlesex
Bernardsville
Middlesex
Date
Collected
7/10/69
7/15/69
7/17/69
7/22/69
7/22/69
Dissolved
Solids
(mgA)
2236
435
1256
287
904
Per Cent
Volatile
(By Weight)
30.5
24.9
23.2
19.5
31.0
-------
MIDDLESEX SEWERAGE AUTHORITY-
INFLUENT
--BERNARDSVILLE
INFLUENT
SEWERAGE AUTHORITY -
100
200 300
TEMPERATURE
400
500
600
700
FIGURE 8 - THERMOGRAVIMETRIC ANALYSIS OF DISSOLVED SOLIDS IN
BERNARDSVILLE AND MIDDLESEX INFLUENT.
21
-------
2\0 215 220 225 230 240 250
235
270 290 320 370
260 280 300 340 400
500 700
600
WAVELENGTH (m/O
FIGURE 9 - ABSORPTION SPECTRA OF INFLUENT FILTRATE
-------
TABLE 4
THE EFFECT OF SOLID DEPOSITS ON POLARIZATION RATIO AND TOTAL
BACK-SCATTERED LIGHT
NJ
OJ
Date
Influent
Collected
8/19/69
8/25/69
8/25/69
9/16/69
Polarization Ratio
Time Beaker
Submerged
42 hours
6 days
8 days
1 month
Before
Cleaning
.569
.421
.422
.435
After
Cleaning
.570
.421
.421
.432
%
Change
0
0
0
0*
iotal Backscattered
Radiation (mv)
Before
Cleaning
3.116
6.485
3.935
0.464**
After
Cleaning
3.118
7.000
6.670
0.504**
%
Change
0
7.5
40.8
9.0
* Within experimental error
** The low detector voltage with the beaker submerged, for one month, both before and after clean-
ing, was the result of an optical readjustment; the width of the incident beam was reduced in
anticipation of a large solids buildup on the beaker's surface. Studies with artificial de-*-
posits had indicated that a large surface buildup could introduce error in the measurement.
Reducing the width of the incident beam eliminated this problem.
-------
intensity of backscattered radiation measured through the deposited
solids was reduced 7.5 per cent. The polarization ratio measurement
was not affected. This was also found to be the case for the beaker
submerged for eight days. A 40.8 per cent reduction in intensity of
the backscattered radiation was observed, but the polarization ratio
was still unaffected by the deposited solids.
Visual examination of the beaker submerged for one month indicated
less of a solids buildup than was observed after eight days. The total
backscattered radiation was reduced only 9 per cent (see Table 4). The
polarization ratio was again unaffected by the solids buildup. Solids
build-up on the optical surfaces apparently do not influence the de-
polarization measurements because the E± and E,, components in the
backscattered radiation are combined into a ratio. Since both compo-
nents are equally attenuated by scattering when the backscattered
radiation passes through the buildup. The effect of this attenuation
is cancelled by the use of a ratio.
Flow Velocity
A gravity flow system was designed and built in the laboratory,
and used for depolarization measurements on flowing sewage. The system
consisted of two 55 gallon drums, one above the other. Opening a ball
valve allows the fluid to flow from the upper to the lower drum through
a clear 3 inch diameter plastic test section. The diameter was selec-
ted to achieve as high a flow rate as possible with an optical path
length which will permit accurate measurements of the polarization
ratio.
A comparison of polarization measurements on static and flowing
sewage samples indicates that the polarization ratio is unaffected by
flow. Little difference in polarization ratio was exhibited by the
static and flowing of Middlesex influent (see Table 5). The fluctu-
ations in the initial measurement of polarization ratios for the
flowing sample was caused by settling of suspended solids. In the
two-chambered gravity flow system used in the experiments, the liquid
was static in the upper reservoir until released to flow through the
test section into the lower chamber.
24
-------
TABLE 5
FLOW vs. POLARIZATION RATIO
to
Ln
Polar-
ization
(Static)
0.634
With
Time
(Sec.)
2
30
45
Orifice
Flow Rate
(ft/sec.)
1.8
1.8
1.8
Polar-
ization
Ratio
0.643
0.654
0.650
Time
(Sec.)
0
1
2
3
4
5
Without Orifice
Flow Rate
(ft. /sec.)
17.9
17.1
16.3
15.5
14.8
14.0
Polar-
ization
Ratio
0.619
0.649
0.663
0.653
0.642
0.626
-------
SECTION VI
DESIGN OF FIELD MODEL
Submerge Unit
The optical and mechanical portion of the suspended solids monitor
is composed of two basic units separated by a light baffle, the light
source and the light sensor sections (see Figure 10). The light source
section consists of a Zeiss microscope lamp operated at 22 watts. The
polarized light is mechanically chopped at the rate of 1 cycle per
second. The chopped light is then passed into the sewage environment
through a quartz window. The receiving unit consists of a beam splitter,
two analyzers, two condenser lenses and a closely matched pair of
photodiodes. The receiving stage is constructed so that the EL and
EN components are measured simultaneously. The outputs are conditioned
electronically to provide a measure of the degree of depolarization
E± / EM . The sum of E^ and EM is also obtained electronically. This
measures the absorption of light by colored particles and lightsource
aging, and indicates when cleaning the window or light-bulb replace-
ment is necessary.
To prevent stray light from passing to the receiver stage, a light
shield is placed between the source light stage and the receiver stage.
These units are housed in a case (see Figure 11) which- was constructed
with a water tight lid using an "0" ring seal. Electrical connections
to the light source unit and the optical receiving unit are brought into
the watertight container through two bulkhead connectors located at the
lower rear section of the watertight container. To insure complete
tightness, latex rubber hoses are pulled over the cables and secured by
clamps to the bulkhead connectors. Division of the cables avoids any
AC field being superimposed on the low-level detector signals.
Electronic System
The detector and electronic parts of the suspended solids monitor
consist of two light sensors, two preamplifiers with independent power
supply, a photocell light system, a synchronizing pulse circuit, a
logic circuit, two amplifier channels providing integration and sub-
traction of signals, a sum and ratio readout circuit and a power
supply. (A circuit diagram is available from the authors upon re-
quest) .
The light sensors for detecting the orthogonally polarized com-
ponents of backscattered radiation are PIN 267 A photodiodes operated
in the photovoltaic mode.
The outputs of the detectors are connected to two identical DC
26
-------
LIGHT BAFFLE
LIGHT SOURCE AND
PHOTO CELL
SERVO DRIVE UNIT
LIGHT CHOPPER
NJ
ROTATIONAL
STAGE
LENS
POLARIZER
TRANSLATIONAL STAGE
FIGURE 10 - OPTICAL AND MECHANICAL COMPONENTS OF SUSPENDED SOLIDS MONITOR
-------
00
FIGURE 11 - DEVELOPMENTAL SUSPENDED SOLID MONITOR SYSTEM
-------
preamplifiers powered by their own dual power supply. These amplifiers
were chosen for low drift and differential output. The output of the
preamplifiers are routed through instrumentation cable to the control
station, from the submersible housing (see Figure 11).
Control Station
The buffer amplifiers and the remaining electronics are located in
the control station (see Figure 11). The negative-agoing signals from
the preamplifiers are applied through 51-ohm resistors to the invert-
ing inputs of the buffer amplifiers. Gain, adjustable from zero to 100,
is provided at this point to adjust for differences in the sensitivity
of the diodes and mismatch of the optical beams. Variable +_ 150 mv
offsets are provided to compensate for drifts of the preamplifiers in
the submersible unit.
A small light projects a beam at the driving gear of the chopper
assembly (see Figure 10). A gold foil mirror is mounted on the chopper
to reflect a beam from the light source into a photocell to produce a
synchronization pulse. The output of the photocell triggers a fixed
25-volt, positive-going pulse of 50 milliseconds duration. The pulse
synchronizes the logic circuits with the rotating chopper.
The logic consists of a network of five pulse generators which
produce 5-volt pulses of adjustable duration to operate the electronic
sample-and-hold switches needed for integration, readout, and can-
cellation. Each of the two channels contains two integrators, to
measure background signal due to ambient light and total signal with
the chopped light added.
After integration of signal plus ambient and ambient, the two are
subtracted at the difference amplifiers. The output of each channel is
applied to the sum amplifier and divider module. After readout, the
integrators are reset to zero for the next cycle. The sum amplifier
has a scale-adjusting potentiometer for calibration., The ratio divider
has no external adjustments and is accurate to +_1 percent.
29
-------
SECTION VII
FIELD EVALUATION
Sewage Source
The field evaluation of the developmental suspended solids monitor
was carried out in the combined sewage influent and in the effluent of
the Perth Amboy, New Jersey Sewage Treatment Plant. This plant is sub-
ject to storm drainage and industrial waste as well as sanitary sewage
and therefore provides a wide range of composition.
Sources of Experimental Scatter
The polarization ratio was found to decrease in a regular manner
with the weight concentration of suspended solids in both the influent
and effluent (see Table 6, Figure 12 and Figure 13). The different
points in these figures represent samples collected at different times.
Replotting the data in Figure 12 according to Equation 5 (page 6),
reveals a linear relationship between Log P and concentration with a
zero intercept (see Figure 14).
The measured polarization ratio can be related to the concentration
of suspended solids only within the reproducibility of the gravimetric
determinations. A spread of as much as 20 percent was encountered in
gravimetric measurements on three samples collected within a period of
minutes, while a maximum range of only 11 percent in degree of depolari-
zation was encountered in the same period of time.
Lack of precision in gravimetric determinations could be caused by
limited sample volume. Because of the length of time required for
filtration, samples were restricted to 50 ml. Another source of error
could lie in the sampling procedures used. Comparison of a continuous
readout from the suspended solids monitor with the gravimetric deter-
mination of suspended solids concentration requires samples that are
representative of that to which the monitor is continuously responding.
In field evaluation of the instrument, a grab sampling technique was
used which could lead to considerable scatter of the results. An open
sampling cup was dipped into the sewage and filled at the level of the
optical window. On withdrawal it passed upward through the sewage sur-
face, thus changing composition especially in the presence of oil or
other floating matter.
Periodically there was an influx of heavy oil into the influent
and a carryover into effluent. The relationship between the polariza-
tion ratio and concentration of suspended solids as measured in the
presence of heavy oil contamination is shown in Figure 13. Replotting
the results in Figure 13 according to Equation 5 reveals that a linear
relationship exists between Log P and concentration but this relation-
30
-------
TABLE 6
FIELD EVALUATION DATA FOR DEVELOPMENTAL
SUSPENDED SOLIDS MONITOR
Date of
Measurement
8/14/70
8/14/79
8/17/70
8/17/70
8/17/70
8/17/70
8/18/70
8/18/70
8/18/70
8/19/70
8/19/70
8/20/70
8/20/70
8/21/70
8/21/70
8/21/70
8/25/70
8/25/70
8/25/70
8/25/70
8/25/70
8/27/70
8/27/70
8/27/70
8/27/70
Medium
Influent
Effluent
Polarization
Ratio
0.466
0.417
0.514
0.441
0.396
0.376
0.338
0.358
0.332
0.408
0.370
0.365
0.325
0.446
0.377
0.365
0.555
0.518
0.493
0.483
0.389
0.453
0.438
0.362
0.340
Average
mg/1 Solids
(Gravimetric)
Range
in mg/1
(Gravimetric)
Log
Polarization
Ratio
Comments
165
208
197
184
219
231
245
220
369
269
319
269
247
357
164-167
196-220
186-208
174-194
208-230
228-236
238-252
210-230
344-393
258-280
308-324
246-286
240-258
332-382
-0.332
-0.380
-0.289
-0.356
-0.403
-0.424
-0..471
-0.446
-0.479
-0.386
-0.432
-0.438
-0.488
-0.350
S00 gas, some
/
oil bubbles
heavy oil
heavy oil
oil
oil
emulsion formed,
225
261
206
208
225
218
207
174
171
163
149
218-240
234-278
198-219
198-215
224-226
200-216
171-181
166-179
160-167
148-150
-0.424
-0.438
-0.256
-0.286
-0.307
-0.314
-0.311
-0..344
-0.358
-0.441
-0.468
affected gravi-
metric det. ,
improper sampling
oil
oil
oil
oil
oil
soap suds,affect-
ed grav. det.
-------
1,0
0.9
0.8
2 0.7
£E
N
0.6
0.4
0.3
0.2
O.I
0
LEGEND
O Collected 8/14/70
D Collected 8/17/70
O Collected 8/18/70
O Collected 8/19/70
A Collected 8/20/70
V Collected 8/21/70
100 200
SUSPENDED SOLIDS CO.NC, mg/l
300
400
FIGURE 12 - POLARIZATION RATIO vs GRAVIMETRIC SUSPENDED SOLIDS, MEASUREMENT
PERTH AMBOY SEWAGE TREATMENT PLANT.
-------
u>
Oo
1.0
0.9
0.8
0.7
1 0.6
N
5 0.5
<
O 0.4
0.3
0.2
O.I —
0
100
200
LEGEND
D Collected 8/17/70
O Collected 8/18/70
O Collected 8/19/70
A Collected 8/20/70
• Collected 8/25/70
300
400
SUSPENDED SOLIDS CONG, mg/l
FIGURE 13 - POLARIZATION RATIO vs GRAVIMETRIC SUSPENDED SOLIDS MEASUREMENT,
PERTH AMBOY SEWAGE TREATMENT - HEAVY OIL CONTAMINATION.
-------
ship is displaced to the right of the relationship obtained when the
samples were free of oil contamination (see Figure 14). Predictably,
the suspended solids monitor does not respond to the oil on water surface
which is inadvertantly collected and appears as weight in the gravimetric
measurements. Calculations indicate that when heavy oil was present,
an increase of about 30 percent in weight of solids was found by gravi-
metric measurements.
Effect of Ambient Light
Measurements on the effluent were performed to determine whether the
ambient radiation resulting from sunlight would influence the results.
Sunlight had no affects on the results obtained with the monitor, pro-
vided that the quartz window was located approcimately 18 inches below
the surface of the Perth Amboy effluent. The instrument was positioned
for three days in an open channel which carried the effluent from the
clarifiers to the chlorination chamber. Large amounts of oil were
present in the effluent for two days. The results obtained during the
time agree with the relationship established earlier between degree of
depolarization and concentration of solids when oil is present (see
Figure 14). The data obtained on the third day, in the absence of oil,
agreed well with the relationship previously established when no oil
was present.
Discussion
The development program under the present contract was terminated
by exhaustion of resources and by the contractor's change of corporate
policy leading to discontinuation of instrument development work. The
present development model was tested as described herein; but with
additional resources, it would be useful to conduct a more extensive
program of evaluation and data collection.
Present Status of the Suspended Solids Monitor Development
Badger Meter Inc., Precision Products Division, Tulsa, Oklahoma,
has designed and is presently constructing a second generation sus-
pended solids monitor under subcontract to Onondaga County, New York,
USEPA Grant No. S-802400 (11020 HFR). They have developed a submersible
package which is a small fraction of the size of the submersible por-
tion of the developmental suspended solids monitor described in this
report. A linear readout over the concentration range from 10 mg/1
to 100,000 mg/1 has been achieved in the laboratory on model hydrosols
using this second generation submersible unit.(5)
A commercial model should be available from Badger Meter by late
1974. Its price is estimated to be about $1,500.
34
-------
0.6 i—
O UNCONTAMINATED SAMPLES
D OIL CONTAMINATED SAMPLES
CO
cr
z
o
N
DC
O
0.
o
_l
(T)
0.5
0.4
0.3
0.2
O.I
100
200
OIL CONTAMINATED SAMPLES
300
400
SUSPENDED SOLIDS CONC, mg/l
FIGURE 14 - LOG POLARIZATION RATIO vs GRAVIMETRIC SUSPENDED
SOLIDS MEASUREMENT, PERTH AMBOY SEWAGE TREATMENT PLANT.
-------
SECTION VIII
REFERENCES
1. "A Flushing System for Combined Sewer Cleansing." Central Engineering
Laboratories, FMC Corporation. U.S. Environmental Protection Agency,
Edison, N.J. 11020 DNO 03/72. 235 p.
2. Liskowitz, J.W., and Huang, J.M., Water Quality Instrumentation,
Vol. 2, Ed. J. W. Scales, pp. 100-109 (1974).
3. Liskowitz, J.W., Env. Sci. and Tech. 5>, 1206 (1971).
4. Oster, G., Chemical Review, 43, 347 (1948).
5. Bell, S.S., Proceedings of Turbidity Workshop, National Oceano-
graphic Instrumentation Center, N.O.A.A., May 4, 1974.
36
-------
SECTION IX
PUBLICATIONS AND PATENTS
1. Liskowitz, J. W., Environ. Sci. Technol., 5, 43, 1971
2. Liskowitz, J. W. and Franey, G. J., Environ. Sci. Technol.,
6, 43, 1972.
3. U. S. Patent 3,600,094 Suspended Solids Concentration Measurement
Using Circular Polarized Light.
4. U. S. Patent 3,612,688 Suspended Organic Particles Monitor Using Cir-
cularly Polarized Light.
5. U. S. Patent 3,612,689 Suspended Particle Concentration Determin-
ation Using Polarized Light.
6. U. S. Patent 3,653,767 Particle Size Distribution Measurement
Using Polarized Light of a Plurality of Wavelengths.
37
-------
SECTION X
APPENDIX
Gravimetric Procedure
The equipment needed in this project for the gravimetric determination
of suspended solids in sewage is as follows:
1. Three or more Pressure Filtration Funnels, Gelman Type 4280.
2
2. Two-stage regulator with a delivery pressure of 200 Ib/in ..
3. 1A Cylinder of Nitrogen.
4. Necessary valves and tubing to allow applying and relieving pressure
to funnels.
5. Supply of lOy and 0.3y filters such as Gelman Type Polypropylene
10M and GA-70-3M.
6. Supply of plastic petri dishes for filters, available from Millipore
Filter Corporation.
7. Analytical balance with 0.1 mg sensitivity.
8. Duckbill forceps for handling filters.
9. Sampling scoop for obtaining sample in front of the suspended solids
monitor.
10. Vacuum oven for drying samples.
11. 50 ml graduated cylinder and misc. glassware.
The equipment is used as follows:
1. Preweigh the filters and store in petri dishes - record weights.
2. Disassemble filter funnels and .position lOy filters in base.
3. Screw sleeve into base.
4. Take a 500-1000 ml sample of sewage in front of monitor while re-
cording ratio.
5. Mix sample thoroughly and measure out 50.0 ml into graduated
cylinder.
6. Pour sample from cylinder into filter assembly.
7. Secure filter assembly to pressure head.
38
-------
8, Position a beaker below outlet of filter.
9. Apply pressure.
10. When the filtration is complete, relieve pressure and disassemble
filter.
11. Remove the lOy filter with forceps. Store in its petri dish.
12. Position 0.3y filter in base.
13. Screw sleeve into position.
14. Pour the filtrate from the beaker to the assembly.
15. Secure filter assembly to pressure head.
16. Position the beaker below outlet of filter.
17. Apply pressure.
18. When the filtration is complete, as evidenced by bubbles coming
from the outlet of the funnel, relieve pressure and disassemble
filter.
19. Remove the 0.3y filter with forceps and store in its petri dish.
20. Dry the samples overnight at 60 C and 20" Hg in the vacuum oven.,
21. Remove the dried samples from the oven and cool for 5-minutes.
22. Weigh the filters to within + 0.1 mg.
23. Compute the sample weight by subtracting the tare weight of the
filter.
39
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-670/2-75-002
4. TITLE AND SUBTITLE
SUSPENDED SOLIDS MONITOR
2.
3. RECIPIENT'S ACCESSION-NO.
5, REPORT DATE
April 1975; Issuing Date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO.
John W. Liskowitz Gerald J. Franey
Joseph Tarczynski
9. PERFORMING ORGANIZATION NAME AND ADDRESS
American Standard Inc.
New Brunswick, New Jersey 08903
10. PROGRAM ELEMENT NO.
1BB034/ROAP. 21-ASY/TASK 037
11. CONTRACT/MMMW NO.
11024DZB (14-12-494)
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
National Environmental Research Center Final 03/69 - 08/70
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A method for measuring concentr
on depolarization of backscattered p
mented. Feasibility studies and fie
influent, effluent and sludge, showe
concentration of solid particles and
relationship is independent of size
particles or solution, sludge consis
optical window. The field evaluatio
a continuous instantaneous in situ m
combined sewers and other wastewater
This report was submitted in fu
No. 14-12-494 by American Standard I
tal Protection Agency. Work was com
17.
ation of suspended solids in liquid media, based
olarized light, has been developed and instru-
Id evaluation of the instrument, using sewage
d that there is a specific relationship between
polarization ratio. It was also shown that the
distribution and density of particles, color of
tency, velocity, and build-up of solids on the
n results indicate that this instrument provides
easurement of suspended solids concentrations in
flows.
Ifillment of Project No. 11024DZB, Contract
ac. under the sponsorship of the U.S. Environmen-
pleted in August, 1970.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
Measurement, *Measuring instru-
ments, Automatic control, Remote
sensing, Flow control, Flow
measurement, Depolarization,
Remote control, *Qualitative
analysis, *Water analysis
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
b.lDENTIFIERS/OPEN ENDED TERMS C. COS ATI Field/Group
Polarization, Instrumentation,
Flow characteristics, Waste 13B
identification, Suspended
solids, Research and develop-
ment, Multiple light scatter,
In situ measurement, Suspended
solids meter
19. SECURITY CLASS (This Report)" 21. NO. OF PAGES
UNCLASSIFIED 48
20. SECURITY CLASS (This page) 22. PRICE
UNCLASSIFIED
EPA Form 2220-1 (9-73)
&U.S. GOVERNMENT PRINTING OFFICE: 1975-657-592/5351 Region No. 5-11
------- |