EPA 907/9-74-005
WASTEWATER SAMPLING METHODOLOGIES
AND
FLOW MEASUREMENT TECHNIQUES
BY
U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION VII
SURVEILLANCE AND ANALYSIS DIVISION
TECHNICAL SUPPORT BRANCH
FIELD INVESTIGATIONS SECTION
DANIEL J. HARRIS
AND
WILLIAM J. KEFFER
JUNE 1974
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EPA 907/9-74-005
WASTEWATER SAMPLING METHODOLOGIES
AND
FLOW MEASUREMENT TECHNIQUES
IroiKv-iUl P-otcotloa Ageney
Re^'IcT, V - .... ;;,v?."'2'
230 £or...L I ^ .:-rc.^ Steaot
C-.-*«-K~'. ::"0.°"-^i-3 60504
BY
U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION VII
SURVEILLANCE AND ANALYSIS DIVISION
TECHNICAL SUPPORT BRANCH
FIELD INVESTIGATIONS SECTION
DANIEL J. HARRIS
AND
WILLIAM J. KEFFER
JUNE 1974
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The Superintendent of Documents
Classification Number is:
EP 1.2:
W28/10
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ACKNOWLEDGEMENTS
The Environmental Protection Agency, Region VII Field Investi-
gations Section wishes to acknowledge the cooperation of the cities
of Kansas City, Kansas; Kansas City, Missouri; Lincoln, Nebraska;
and Ashland, Nebraska, and Richards-Gebaur Air Force Base in allow-
ing the section to conduct sampler comparison studies at their
wastewater treatment facilities.
The section is also indebted to the Instrumentation Specialties
Company of Lincoln, Nebraska; the N-Con Systems Company of New
Rochelle, New York; and to Sirco Controls Company of Seattle,
Washington, for loan of sampling equipment which was used in the
sampler comparison studies.
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m
TABLE OF CONTENTS
PAGE NO.
DISCLAIMER i
ACKNOWLEDGEMENTS ii
TABLE OF CONTENTS iii
LIST OF FIGURES vii
LIST OF TABLES viii
I. INTRODUCTION 1
II. STRUCTURE AND ACTIVITIES OF THE FIELD
INVESTIGATIONS SECTION 4
III. SAMPLER RELIABILITY, INSTALLATION, AND OPERATION . . 10
A. SAMPLER RELIABILITY 10
1. SAMPLER INVENTORY 10
a. SIGMAMOTOR MODELS WA-2 AND WD-2 .... 12
b. BRAILSFORD MODEL EV-1 13
c. BRAILSFORD MODEL DU-1 14
d. BRAILSFORD MODEL EP-1 15
e. HANTS MARK 3B 16
f. ISCO MODEL 1391-X 17
g. ISCO MODEL 1392 18
h. SIRCO MODEL MKV7S 18
i. PRO-TECH MODEL C6-125P 20
j. QCEC MODEL CVE 21
k. N-CON SCOUT 22
1. N-CON SURVEYOR 23
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IV
PAGE NO.
m. N-CON SENTINEL 23
2. INCIDENCE OF SAMPLER MALFUNCTION 24
B. INSTALLATION AND OPERATION OF SAMPLING
EQUIPMENT 27
IV. SAMPLING METHODS AND DATA VARIABILITY 32
A. PERFORMANCE OF AUTOMATIC WASTEWATER
SAMPLING EQUIPMENT 32
1. RICHARDS-GEBAUR AFB STUDY 32
2. THERESA STREET SEWAGE TREATMENT PLANT
- LINCOLN, NEBRASKA 50
3. ASHLAND, NEBRASKA, SEWAGE TREATMENT PLANT . 53
4. KANSAS CITY, KANSAS, KAW POINT SEWAGE
TREATMENT PLANT - OCTOBER 1973 57
5. KANSAS CITY, KANSAS, KAW POINT SEWAGE
TREATMENT PLANT - DECEMBER 17-19, 1973. .. 59
B. COMPARISON OF TWO MANUAL GRAB SAMPLING METHODS . 65
C. INTERLABORATORY VARIATIONS 72
D. SUMMARY AND DISCUSSION 75
1. SAMPLER PERFORMANCE 75
2. ADDITIONAL PERFORMANCE STUDIES 79
3. SELECTION OF SAMPLING EQUIPMENT 80
4. FLOW PROPORTIONAL SAMPLING 81
5. SAMPLING METHODOLOGY 83
6. THE IDEAL AUTOMATIC SAMPLER 85
7. -THE PROFESSIONAL IN THE FIELD 87
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PAGE NO.
V. HYDRAULIC MEASUREMENTS . . 89
A. WEIRS, FLUMES, AND RECORDING EQUIPMENT 90
1. WEIRS 90
2. FLUMES 92
3. FLOW RECORDING EQUIPMENT 93
a. FACILITY RECORDERS 93
b. PORTABLE RECORDERS 94
(1) BELFORT LIQUID LEVEL RECORDER . . 94
(2) MANNING DIPPER RECORDER 95
c. DISCHARGE CALCULATIONS 96
B. WET WELL VOLUME DISPLACEMENT 96
C. FLOW RATES IN PIPES 97
i. "VOLUMETRIC MEASUREMENT 97
2. PIPE WEIRS 97
3. TRAJECTORY METHODS 98
a. CALIFORNIA PIPE METHOD . 98
b. PURDUE METHOD 99
4. ORIFICE BUCKET 99
5. MANNING FORMULA TOO
6. FLOWMETER 101
D. OPEN CHANNEL FLOW 102
1. STREAM GAGING 102
2. ELECTROMAGNETIC WATER CURRENT METER 104
E. PRECISION OF THREE MEASUREMENT METHODS 105
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PAGE NO.
VI. CONCLUSIONS 110
APPENDIX - NAMES AND ADDRESSES OF MANUFACTURERS AND
SUPPLIERS OF SAMPLERS LISTED IN TABLE I. . . 113
BIBLIOGRAPHY 115
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V11
LIST OF FIGURES
FIGURE NO. ' PAGE NO.
Flow Rates - Richards-Gebaur Sewage
Treatment Plant , 40
Extraneous Flow Project - Grab: Sampling of
Influent With Bucket - September 7, 1972 ... 69
Extraneous Flow Project - Grab Sampling of
Influent With Submersible Pump - November 6,
1972 70
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viii
LIST OF TABLES
TABLE NO. PAGE NO.
I INVENTORY OF AUTOMATIC WASTEWATER SAMPLERS .. 11
II INCIDENCE OF SAMPLER MALFUNCTION 26
III RICHARDS-6EBAUR SEWAGE TREATMENT PLANT
RAW WASTE 37
IV RICHARDS-GEBAUR SEWAGE TREATMENT PLANT
PRIMARY EFFLUENT 38
V RICHARDS-GEBAUR SEWAGE TREATMENT PLANT
FINAL EFFLUENT 39
VI RICHARDS-GEBAUR SEWAGE TREATMENT PLANT NFS
COMPARISON RATIO OF SAMPLING METHOD VALUE TO
MANUAL FLOW VALUE 41
VII APPARENT REMOVAL EFFICIENCIES OF RICHARDS-
GEBAUR FACILITY WITH VARIOUS COMBINATIONS OF
24-HR SAMPLING METHODS 43
VIII RICHARDS-GEBAUR, NONFILTERABLE SOLIDS REMOVAL
EFFICIENCY AS A FUNCTION OF NUMBER OF GRAB
SAMPLES, TIME OF COLLECTION, COLLECTION
INTERVAL, AND DAYS OF SAMPLING 45
IX RICHARDS-GEBAUR AIR FORCE BASE STUDY -
ANALYSES OUTSIDE RANGE OF MANUAL
FLOW-COMPOSITED SAMPLES 49
X STATISTICAL SUMMARY OF RICHARDS-GEBAUR STUDY . 51
XI THERESA STREET SEWAGE TREATMENT PLANT -
LINCOLN, NEBRASKA - WASTEWATER
CHARACTERIZATION 54
XII ASHLAND, NEBRASKA, SEWAGE TREATMENT PLANT -
RAW WASTE 55
XIII ASHbAND, NEBRASKA, SEWAGE TREATMENT PLANT -
FINAL EFFLUENT 56
XIV APPARENT REMOVAL EFFICIENCIES OF ASHLAND,
NEBRASKA, SEWAGE TREATMENT PLANT 58
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ix
TABLE NO. PAGE NO.
XV RAW DATA AND STATISTICAL SUMMARY OF SAMPLER
COMPARISON STUDY AT KANSAS CITY, KANSAS,
KAW POINT SEWAGE TREATMENT PLANT 62
XVI INFLUENT - EXTRANEOUS FLOW PROJECT -
SEPTEMBER 7, 1972 - GRAB SAMPLING WITH
BUCKET 67
XVII INFLUENT - EXTRANEOUS FLOW PROJECT -
NOVEMBER 6, 1972 - GRAB SAMPLING WITH
SUBMERSIBLE PUMP 68
XVIII INTERLABORATORY ANALYTICAL AND SAMPLE
VARIATION - KAW POINT SEWAGE TREATMENT
PLANT - KANSAS CITY, KANSAS - APRIL 1973. . 74
XIX SUMMARY OF FLOW DATA OBTAINED USING A PRICE
TYPE PYGMY METER (PPM) AND A MARSH MCBIRNEY
CURRENT METER (MMCM) 107
AND
108
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I. INTRODUCTION
The Environmental Protection Agency, Region VII, Field Inves-
tigations Section has been responding to an increasing number of
requests for information resulting from its water/wastewater sam-
pling activities and its experience with various commercial sampling
and flow measurement devices. These requests have come from state
environmental agencies, other EPA regions, engineering consulting
firms, commercial laboratories, industries, universities, vocational
schools, and individuals. It is the purpose of this report to
consolidate and summarize the activities, experience, sampling
methods, and field measurement techniques of the Field Investigations
Section in order to provide a ready source of information for these
interested parties.
During the past two years there has been a dramatic expansion
in demand for wastewater chemistry data on point source discharges
and a concurrent shift away from general purpose stream studies.
In order to meet these needs and to provide data for enforcement
efforts, compliance monitoring, water quality standards evaluations,
and waste treatment facility operational assistance and performance
evaluation, the Field Investigations Section has minimized efforts
requiring manual methods of sample collection and has placed
increasing reliance upon commercially available automatic wastewater
sampling equipment.
Emphasis on point source sampling has been accompanied by a
corresponding increase in the need for hydraulic discharge
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measurements for the purposes of making up flow-proportional
samples, calculating pollutant loadings, and setting effluent
limitations. With the hundreds of discharges sampled every year,
the Field Investigations Section has been forced to resort to an
ever expanding variety of flow measurement techniques as a result
of the plethora of sampling site configurations encountered in its
field surveys.
As the section gained familiarity and experience with various
compositors and hydraulic measurement methods and with the accumu-
lation of large volumes of water quality information, it became
apparent that different sampling equipment and flow measurement
techniques resulted in significant data dissimilarity. These dis-
crepancies raised several questions regarding: (a) the reliability
of various commercial sampling equipment, (b) the representative-
ness of samples collected by different automatic sampling equipment,
(c) the variation in wastewater chemistry data which can be expected
as a result of differences in performance of equipment and changes
in manual collection methods, (d) the adequacy of discrete grab
sample analysis for routine surveys and monitoring programs, (e)
the necessity of flow-proportional sampling of raw municipal
wastewaters, and (f) the precision of flow measurement methods.
During the past twelve months the Field Investigations Section
has mounted several special sampling efforts and has extracted data
from past and continuing surveys and has drawn upon the collective
experience of the section's staff to gain insight into the preceding
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considerations. This report details the results of that twelve-
month effort.
It is not the function of this report to serve as a substitute
for the judgement of the professional in the field but rather to
provide a basis for the development of sound sampling programs and
to focus attention upon those sources of error and data variability
which the section has gained knowledge of, often at considerable
time and expense. It is the opinion of the Field Investigations
staff that data quality control should start in the field instead
of the laboratory.
As the experience of the section continues to grow, as new
sampling situations are encountered, and as new equipment comes on
the market and becomes available to the section for testing and
evaluation, it is expected that this report will be revised and
expanded.
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II. STRUCTURE AND ACTIVITIES OF THE FIELD INVESTIGATIONS SECTION
The Field Investigations Section, which is located in the
offices of the EPA, Region VII Laboratory*, consists of eight pro-
fessional and subprofessional employees who are responsible for
planning the field surveys and sample collection activities of the
Surveillance and Analysis Division. This division, with its labo-
ratory capability, provides the water quality information of the
agency in the four-state region of Missouri, Nebraska, Kansas, and
Iowa.
The Field Investigations professional staff includes two
sanitary engineers (GS-13 and 11), one chemical engineer (GS-11),
and one hydro!ogist (GS-9). The subprofessional staff consists of
four engineering technicians in grades ranging from GS-3 to 6. The
regional laboratory, with a staff of eight professional chemists
(GS-7 to 13) and three microbiologists (GS-7, 9 and 12), is respon-
sible for operating the mobile laboratories of the section during
field surveys.
In areas outside the range in which analytical support can be
provided by the regional laboratory, field sampling teams normally
operate within a 161-km (100-mile) radius of a mobile laboratory
which is generally set up at a wastewater treatment facility in
a community within the area of interest. Because of logistics
problems in some of the more sparsely populated areas of the
region, it is frequently necessary to work field teams outside of
*~25 Funston RoacU Kansas City, Kansas 66115 ™~™
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this 161-km (100-mile) radius. Ten to twenty-five percent of the
total field activity may be conducted at distances up to 322 km
(200 miles) from the laboratory base. Operating at these greater
distances reduces the section capability by an estimated fifty per-
cent and greatly increases the unit cost of sample collection.
Prior to mounting a survey the section makes every effort to
ascertain and consolidate the various data needs of the agency and
of the state in order to avoid duplication of effort and to minimize
the number of laboratory set ups. It requires a minimum of one wk
to ten days to prepare and stock a mobile laboratory; get it on
site; have electricity, water, and phone installed; and then torn
down and returned to Kansas City following completion of a survey.
If possible, field activities in areas requiring mobile laboratory
support are restricted to surveys, of thirty days duration or
longer.
Major field equipment currently available to the Field Inves-
tigations Section, in addition to analytical equipment permanently
housed in the regional laboratory, are listed below with the.
approximate initial costs:
1 Mobile Laboratory $15,000
1 Mobile Laboratory (on loan)
7 6SA Vehicles (monthly operating cost) 800
5 .Boats and Motors 5,000
50 Composite Sample Collectors
(approximately $560 each) 28,000
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Flow Recording and Measuring Equipment* $ 6,600
Current meters
Weirs
Float recorders
Conductance liquid level recorders
Field Analysis Equipment 6,100
pH meters
Conductivity meters
Fluorometers
Dissolved oxygen meters
Sonar depth meters
Portable Generators 1,200
Metal Detector 300
The section attempts to carefully review the locations to be
sampled in order to limit sample collection and to reduce the
analytical work load on the laboratory to the absolute min required
to provide the necessary information. In the routine monitoring of
municipal wastewater treatment facilities, the section normally
utilizes unattended compositors to collect three 24-hr composites
at all influent and effluent stations. Lagoon effluents are
generally grab sampled due to the more uniform character of these
discharges. Scheduling three days of sampling at each site allows
the section some latitude in the event of compositor malfunction or
T~
missed dilutions in the laboratory. In the absence of any evidence
* See Chapter V
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indicating a significant industrial waste problem, data collected
on municipal wastewaters include:
Water temperature
Flow (instantaneous or continuous depending upon plant
recorders and/or flow measurement devices)
pH
Specific conductance
Five-day biochemical oxygen demand
Chemical o^gen demand
Nonfilterable solids (Total suspended solids)
Ammonia nitrogen
Total kjeldahl nitrogen
Nitrite-nitrate nitrogen
Total phosphorus
Fecal coliform
Industrial wastewaters offer almost endless variety and it is
difficult to generalize sampling efforts. Current industrial sam-
pling has been oriented toward a 5-day work period at each plant
with unattended mechanical time-composite sample collectors
installed at each point of interest. Sample collection periods
are generally 24 hr and samples are split with company personnel.
Analytical requirements vary widely but generally include the same
analyses as for municipal wastewaters plus several metal analyses
and frequently oil and grease. Those industrial wastes which
require use of the gas chromotography-mass spectrometer (GC-MS) for
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8
analyses require analytical times'which are orders of magnitude
greater than the time necessary for other determinations. A single
sample for GO-MS analysis can demand as much as one man-month of
professional analytical time.
Under favorable conditions a mobile laboratory field operation
works best with a crew of seven people including: (a) two engi-
neers, (b) two engineering technicians, (c) one chemist, (d) one
microbiologist, and (e) one laboratory technician. Working
entirely within a 161-km (100-mile) radius of the mobile labora-
tory this staff (which is rotated at 2-wk intervals) would be able
to install compositors and collect approximately 100 samples per
wk for field and laboratory analyses. Total time and cost for a
30-day field survey is estimated as follows:
Engineers
1 man-month office preparation
2 man-months field work
2 man-months data analyses and report writing
Engineering Technicians
2 man-months mobile laboratory and equipment
repair and preparation
4 man-months field work
Laboratory Personnel
6 man-months mobile laboratory work
6 man-months regional laboratory analytical work
Clerical
2 man-months planning and report preparation
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Costs
Salaries* $23,500
Per Diem 7,300
Travel of Personnel 400
Government Bill of Ladings 400
Vehicles .1,000
Miscellaneous Equipment 1,500
(Ice, batteries, containers,
utilities, chemicals, etc.)
$34,100
This results in an average cost per sample of $85.25 for survey
work not requiring use of the GC-MS. The cost for estimating pur-
poses should be raised to $100.00 per sample to cover management
and other overhead.
* Salaries are multiplied by a factor of 1.2 to account for com-
pensatory time allotted following the 10-to-12-hr, 7-day-a-week
work schedule normally used in the field.
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III. SAMPLER RELIABILITY, INSTALLATION, AND OPERATION
A. SAMPLER RELIABILITY
Within the past two yr the Field Investigations Section has
purchased fifty commercial compositors of fifteen makes and models
and, as a result of numerous surveys, has collectively accumulated
approximately 90,000 hr of field operational experience with the
units on municipal and industrial raw and treated wastewaters under
summer and winter conditions. This experience has pointed out
design weaknesses, operational difficulties, and maintenance prob-
lems and has given the section an understanding of the capabilities
and limitations of each sampler.
A previous evaluation (1) of commercially available samplers
reported little in the way of field operational information. It is
believed that this summary of on-site experience with these instru-
ments will be of value to others in the water pollution control
field in selecting compositors for specific applications and in
avoiding some of those operational problems encountered by the
Field Investigations Section.
1. SAMPLER INVENTORY
Table I is an inventory of fourteen various makes and models
of commercially available compositors which the Field Investigations
Section has used routinely on field sampling efforts or has gained
some experience with, courtesy of the manufacturer. The section
also has two additional compositors which were either special order
or were made in the laboratory; however, as these are nonstandard,
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TABLE I
INVENTORY OF AUTOMATIC WASTEWATER SAMPLERS
11
Samp! er
Sigmamotor WA-2
Sigmamotor WD-2
Brailsford EV-1
Brailsford DU-1
Brailsford EP-1
Hants Mark 3B
ISCO 1391-X
ISCO 1392
Sirco MKVS7
Pro-Tech CG-125P
QCEC CVE
N-Con Scout
N-Con Surveyor
N-Con Sentinel '•c'
Cost
450
650
583
325
300
595
995
995
1,275
580
620
450
275
Unknown
Power
Supply
AC
AC-DC
AC -DC
DC
DC
Manual
Vacuum
AC-DC
AC -DC
AC-DC
Gas
AC
DC
AC
AC
Type Of
Sample
Time
Time
Time or
Flow
Time or
Flow
Time
Time
Time or
Flow
Time or
Flow
Time or
Flow
Time or
Flow
Time
Time
Time or
Flow
Time or
Flow
Type Of
Pump
Peristaltic
Peristaltic
Vacuum Pump
Piston
Piston
Manual
Vacuum
Peristaltic
Peristaltic
Piston
Gas Lift
Piston
Peristaltic
Impel 1 er
Optional
Intake
Tube
ID
3.17
3.17
4.76
4.76
4.76
6.35
6.35
6.35
9.52
3.17
6.35
6.35
12.70
NA
Liquid
Intake
Velocity
cm/sec(b)
7.9
7.9
0.45
0.45
0.45
75«>
21
61
98
207
61-152
7.6
36
Variable
Purge
Cycle
No
No
No
No
No
No
Yes
Yes
Ye.s
Yes
Yes
Yes
Gravity
NA
(a) Multiply by 0.0394 to obtain inches
/
(b) Multiply by 0.0328 to obtain fps
'c' Loaned courtesy of manufacturer
(d) Mean
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12
not readily available items, they will not be discussed in this
report.
The names and addresses of the manufacturers of the composi-
tors shown in Table I can be found in the appendix. The cost
figures for each compositor represented the basic unit only and do
not reflect such optional extras as rechargeable battery packs,
flow-proportioning devices, or multiplexing units, etc. Type of
sample refers to whether the instrument is restricted to taking a
time-composite sample or if it has flow-proportional capability
(optional extra). It can be seen that most of the units can
collect both types of samples. Intake tube ID and liquid intake
velocity refer, respectively, to the inside diameter of the sample
intake line and to the velocity of the liquid in this line during
the sampling cycle. Table I also indicates whether or not the
sampler has a purge cycle to prevent hose clogging and to reduce
cross contamination of discrete samples or aliquots.
a. SIGMAMOTOR MODELS WA-2 AND WD-2
The operation of these two compositors is identical with the
exception of the alternate battery pack power source on Model WD-2.
These units rely on a timer and peristaltic pump for collection of
time-composite samples. Six of these units have been used for
several thousand hours of running time. The units are durable and
easily installed in manholes. Routine sampling with 4.5-m (15-ft)
heads is possible. Because of the 3.17-mm (1/8-in.) ID intake line
and the 7.9-cm/sec (0.26-fps) liquid intake velocity, these units
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13
are best suited to waste streams without large or high density
suspended material.
Field use has revealed some operational problems with these
units. These compositors have no by-pass switch on the timer and
during installation it is necessary to reset the timer to zero
several times to check the operation of the pump prior to setting
the timer to the appropriate sample collection cycle.
The motor unit of these compositors is at the bottom of the
fiber glass case which has a 1.2-cm (0.5-in.) lip on it. If the
sample container overflows, this lip will retain enough water to
short out and permanently damage the motor. This situation
occurred during one of the field surveys of the section and motor
replacement cost was $37.40.
Battery operation of the WD-2 model is restricted unless
extra batteries and recharger are available. Only one day of
operation is possible from a fully charged battery pack.
b. BRAILSFORD MODEL EV-1
This unit collects a single 3.8-1 (1-gal) sample during an
8-, 16-, 24-, or 48-hr period. Operation is dependent upon a
vacuum pump and metering chamber. Maximum pumping head for this
compositor is about 1.2 to 1.8 m (4 to 6 ft). The unit will operate
continuously for five days on a 12-v, rechargeable battery. For
reliable operation this compositor should be installed level and
the metering chamber cleaned at frequent intervals. A build up of
solids in the metering chamber will cause the float to stick and
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14
will result in incomplete composites. Because of the small diam-
eter sampling hose and low liquid intake velocity, this sampler is
best utilized for sampling wastewaters with low suspended solids
concentrations.
With an optional head detector and a suitable weir this unit
will collect flow-proportional samples.
c. BRAILSFORD MODEL DU-1
This compositor utilizes a small piston pump to collect a
single 7.6-1 (2-gal) sample over a variable time period. When used
in conjunction with a linear head detector and an appropriate weir,
this compositor will collect flow-proportional samples. The
instrument, with the exception of the optional head detector, is
self-contained and can be easily installed in a manhole. Overflow
of the sample bottle is prevented by a float activated cut off
switch which fits in the top of the bottle. This switch is sensi-
tive to positions from vertical and necessitates level installation
of the compositor. If routine servicing is assured, this switch
can be by-passed. Maximum head is about 1.2 to 1.8 m (4 to 6 ft).
Battery voltage must be checked routinely on these units.
When batteries under power show less than 5.5-v, they should be
replaced. Iron and/or lime precipitation and scouring of the
piston chamber has been a problem with boiler blowdown and water
plant wastes. The discharge nipple of the piston pump is in a
restricted location behind the pump mounting plate. Attaching
tubing to this nipple is difficult, especially under winter field
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15
conditions. Because of the 4.76-mm (3/16-in.) ID intake line and
the 0.45-cm/sec (0.18-fps) liquid intake velocity, this sampler is
best used on waste streams with low suspended solids concentrations.
d. BRAILSFORD MODEL EP-1
This compositor'is an "explosion proof" unit with a cast
aluminum housing for motor and 6-v lantern battery power source.
Sampling is by a piston pump with a stroke which can be adjusted
for different sample volumes or composite periods. The unit does
not have flow proportioning capability. Head limitations are
about the same as for the Brailsford EV-1 and DU-1.
Operational reliability of these units has been very good
with wastewaters having low suspended solids levels. Because of
the relatively low cost of these compositors, they are the unit of
choice in situations where equipment security is minimal and van-
dalism is of concern. One of these samplers sustained a shotgun
blast with minimal damage.
One operational difficulty with the instrument is the necessity
of having to remove nine screws in order to get the aluminum back
plate off to change or check the battery. This procedure is time
consuming and it would appear that a design using a spring loaded
clasp of some sort would be just as effective. Inadvertently,
these units have been totally submerged several times and have
continued to operate; however, as there is no gasket between the
back plate and the motor housing, they will admit water. Whether
or not these units are actually explosion proof has not been
determined by the authors.
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16
e. HANTS MARK 3B
This sampler is a vacuum operated sampler which collects
twelve discrete 400-ml (13.5-oz) samples at time intervals ranging
from 0.5 up to 12 hr, depending upon the particular spring-wound
timer that is interfaced with it. Samples can be analyzed indi-
vidually, combined on an equal volume basis, or proportioned on
the basis of readings taken from external flow measuring equip-
ment. The sample bottles are evacuated by means of a manually
operated pump supplied with the unit.
These compositors are reliable, relatively well constructed,
and almost goof proof. Because of the high liquid velocity, these
units are well suited for sampling wastewater with high solids
levels.
This unit has a separate intake tube for each sample con-
tatner and it is difficult to adequately clean these twelve intake
lines in the field. The large tube nest and screened intake make
it impossible to use this compositor in flow velocities above
0.46 m/sec (1.5 fps) or in depths of less than 15 cm (6 in.).
Also, the screened intake is not streamlined and tends to collect
solids which should be removed at frequent intervals to avoid
possible bias in the sample data.
Replacement parts are not readily available for this sampler
since the United States distributor does not maintain an inventory
and needed items must come from England. Parts orders take more
than sixty days, even for the simplest items, and the company will
not accept parts orders for less than $25.
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17
f. ISCO MODEL 1391-X
The Field Investigations Section has accumulated about 1,500
hr of experience with three of these units and has had minimal
operational problems with them. As many as 28 discrete, 500-ml
(17-oz) samples are collected at a preset time interval by a
peristaltic type pump which purges the intake line after each
cycle. Flow-proportional sampling is possible by interfacing the
unit with a flow metering device or by manually compositing indi-
vidual samples according to an external flow measurement record.
The unit is self-contained, operates from either line or
battery power source, and is designed to fit in a manhole. The
bottom half of the unit, which holds the sample containers, is
insulated and has room for about 2.3 kg (5 Ib) of ice. Data com-
piled by the section (Chapter IV) would indicate that these units
are best suited for sampling wastewaters with low suspended solids
concentrations.
The only significant operational problem has been due to
occasional clogging of the intake line. Although the pump back
cycles after each collection interval, this is not always sufficient
to clear the line. The case of these units is molded of a black
plastic and the manufacturer suggests that the units be painted
white if they are to be operated in direct sunlight. This
precaution will increase the life of the electronics and of the
ice in the sample container. In warm weather, ice will not last
for 24 hr in these units.
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18
As of this writing, the Model 1391 is no longer being produced
i
and has been replaced by the Model 1392 which has a higher liquid
intake velocity. The 1391 can be modified at the factory to
increase the intake velocity. The Field Investigations Section
has had its three units modified at a cost of $125 each.
g. ISCO MODEL 1392
The section has accumulated about 600 hr of experience with
four of these units. This model is practically identical to the
1391-X with the exception of the liquid intake velocity which has
been increased to 61 cm/sec (2 fps) in an attempt to improve
solids capture efficiency. The water chemistry data accumulated
by the section are too limited to determine whether or not this
unit can effectively be used on high solids level wastes.
h. SIRCO MODEL MKV7S
Field experience with this unit has been limited to about 300
hr of operation of a model which was loaned to the section prior
to receipt of its own sampler. The primary reasons for purchasing
this instrument were the AC-DC operation, discrete (24-bottle)
sample collection, and the high, 98-cm/sec (3.2-fps), liquid
intake velocity which was believed to be more suitable for high
solids level raw wastes.
To date, field use has not revealed any operational diffi-
culties with the sampler; however, cleaning of parts which come
in contact with the sample is somewhat laborious.
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19
The unit purchased by the section was checked out in the
laboratory upon arrival and several deficiencies were noted:
(a) polarity of battery was reversed and not as indicated on bat-
tery terminals, (b) an electrical component and some wiring were
burnt out and were replaced at a cost of about twenty dollars, and
(c) functions of electrical toggle switches on the instrument panel
were not well marked, i.e. off-on switch reads left to right and
switch moves vertically. The operation manual supplied with this
unit is extremely "sketchy" and should be expanded to give more
detailed operational information.
The precision of the discrete sample volumes was also checked
out in the laboratory by putting the intake line in a container
filled with tap water and running the unit through the 24-bottle
collection cycle. With a mean sample volume of about 280 ml (9.5
oz) the standard deviation was ±30 ml (1 oz). One reason for this
variation is due to the design of the sample container compartment
which is a round plastic tub and the 24 sample bottles which are
wedged shaped segments of the sampler compartment. Although there
is a retainer plate to hold the*sample bottles in position, the
bottles are somewhat undersized in relation to the diam of the
container compartment and there is an accumulated space of about
1.3 cm (0.5 in.) in the 24-bottle sample ring. Consequently, the
mouths of the sample bottles are not self-centering with respect
to the stops of the sample distributor arm. This space is suffi-
cient to allow the arm to discharge samples outside the mouths of
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20
some of the sample bottles and down into the plastic tub. Another
reason for the sample volume variation is the high velocity of the
sample as it enters the metering chamber. Discrete sample volumes
are controlled by the vertical spacing of electrical probes within
the metering chamber. The turbulence in the metering chamber as a
result of the liquid intake velocity is sufficient to vary the
water level at which the electrical probes sense completion of the
sampling cycle.
i. PRO-TECH MODEL C6-125P
Two of these compositors were purchased because of the
explosion-proof feature and because of the partial purge of the
intake screen during each sampling interval.
This unit is pressure operated with small canisters of freon
gas and collects a single 3.8-1 (1-gal) sample over a variable
time period. With an optional sensing device the instrument will
collect flow-proportional samples.
Personnel in the Field Investigations Section have accumulated
about 600 hr of experience with this compositor and have been
plagued with minor problems related to poor assembly. Most of the
case screws have fallen out at one time or another and all internal
hoses have been replaced due to leaks in the gas system. When
repaired, the samplers performed very well on wastes with high
solids because of the screen area of the intake and the purging
action of the gas flow.
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21
Experience has revealed several operational difficulties:
(a) the 22.9-cm (9-in.) intake sample chamber must be installed
vertically in the waste stream and requires about 30.5 cm (12 in.)
of water for reliable operation, (b) considerably more individual
expertise is required to obtain satisfactory performance with this
unit than with other compositors, (c) the unit is difficult to
repair and service due to restricted access to the case interior,
and (d) the design is such that only a 3.8-1 (1-gal) sample con-
tainer can be housed inside the case.
j. QCEC MODEL CVE
These samplers were developed by the Dow Chemical Company and
are made under license. Sampler operation is accomplished by a
solenoid-controlled vacuum pump similar to laboratory pumps used by
microbiologists for Millipore filtrations. The variable timer
activated pump draws sample portions through a 6.35-mm (0.25-in.)
ID tube at a velocity which can be adjusted from 61 to 152 cm/sec
(2 to 5 fps). The intake and discharge line of the unit are blown
clear before and after each sampling cycle. Equal volume sample
increments composited at a preset time interval or according to
flow based on signals from external flow metering equipment are
drawn into a 3.8-1 (1-gal) glass jug.
Because of the high vacuum and the purge cycle this unit
seldom clogs and is the compositor of choice for sampling raw
wastewaters with high solids levels.
Use of these units has revealed several operational defi-
.ciencies: (a) lid retaining straps break and rubber gaskets
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22
around the edges of the fiber glass case have to be reglued on a
regular basis, (b) samples have frequently been missed due to loss
of vacuum in the system; vacuum loss commonly occurs at the mouth
of the glass jug sample container because of vibration or tempera-
ture changes which cause the rubber stopper to lose its seal; screw
caps over the stopper have been used to rectify this problem but
are an inconvenience, (c) if one wants to use the self-contained
sample container compartment sample volumes are limited to 3.8 1
(1 gal) because of space restrictions, (d) because the compositor
draws a vacuum in the sample container glass containers must be
used, (e) the sample container compartment is not insulated and
ice cannot be maintained for a practical length of time, and (f)
the sampler is not suited for installation in manholes or other
restricted areas because of its weight and apparently unnecessarily
large bulk.
k. N-CON SCOUT
The Field Investigations Section has one of these compositors
in use. They are a well-made, DC-powered unit equipped with a
peristaltic pump and a very flexible timer. This instrument is
suited only for time-composite samples and because of the 7.6-cm/
sec (0.25-fps) liquid intake velocity it is best utilized on
wastewaters with low concentrations of suspended solids.
Although the timing mechanism is somewhat complex and fragile*
"s.
this unit is preferred by the Field Investigations Section over
other similar samplers .due to the self-purging feature, DC
capability, and lower cost.
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23
1. N-CON SURVEYOR
Operational problems include the limited 1.8-m (6-ft) suction
head and a 12.7-mm (0.5-in.) ID constriction on the intake side of
the pump which is threaded for a standard garden hose coupling.
This constriction has been a constant source of clogging when the
compositor is used to sample wastewaters with appreciable suspended
solids concentrations. An additional problem is the diverter tube
which transports about fifteen percent of the throughput to the
sample contained. This tube must be kept above the liquid level
in the sample container or back siphoning of the sample will occur.
Transport through the diverter tube seems to work best when back
pressure on it is maintained by raising a portion of the intake
line to an elevation which is above the point where the diverter
tube couples to the pump.
m. N-CON SENTINEL
The Field Investigations Section does not have any of these
compositors and experience has been limited to about forty, hours
of operation on a raw waste with a unit provided courtesy of the
manufacturer.
This is the only unit the section has had the opportunity to
evaluate which has a refrigerated sample container compartment. In
operation, a portion of the waste stream is continuously diverted
to an integral flow through sampling chamber by gravity or external
pump. In the sampling chamber a dipper arm rotates through an arc
of approximately 90 degrees at a preset time interval or in
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24
response to signals from an integrating flow meter and collects a
sample from the diverted waste stream. As the dipper rotates above
level, it pours the collected aliquot into a funnel which delivers
it to a container in the refrigerated compartment below.
Although this unit appears to be almost clog proof, two fea-
tures were noted which could possibly bias the representativeness
of the collected composite. On the model tested, the discharge end
of the dipper was not centered over the funnel. On the upstroke of
the dipper arm during a sampling cycle, the dipper was observed to
pour some of the collected waste outside of the funnel and back
into the flow-through, sampling chamber. It would appear that
heavier suspended material could have been lost. Secondly, the
sampling chamber has a relatively large cross-sectional area with a
flow-through velocity which is dependent upon the volume of water
supplied to it. This increase in area and corresponding decrease
in velocity could result in heavier material settling to the bottom
of the sampling chamber below the reach of the dipper arm.
This sampler because of its size, 0.64 x 0.79 x 1.52 m
(25 x 31 x 60 in.), and weight, 113 kg (250 Ib), 1s best suited for
long-term or permanent monitoring programs.
2. INCIDENCE OF SAMPLER MALFUNCTION
The information presented in Table II shows the incidence of
malfunction of eleven different makes and models of samplers. These
data resulted from two surveys of industrial and municipal waste-
water treatment facilities in the greater Kansas City Metropolitan
Area.
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25
Referring to Table II, the data show the total number of times
each sampler was used as well as whether it was used on raw or
treated waste. The reason for the lower use of compositors at
effluent stations was due to the number of lagoons included in the
surveys. Lagoon effluents were manually grab sampled. Incidence
of sampler failure is also broken down as to influent or effluent
station. Those incidents of failure are only those instances in
which a 24-hr composite was short or missed altogether as a direct
result of a sampler malfunction which could not reasonably have
been prevented by the field sampling team. The predominate cause
of malfunction was plugging of the intake lines with suspended
solid material; secondary causes included loose tubing and assorted
hardware. In considering the data on the three Brailsford samplers
(DU-1, EV-1, and EP-1), it should be pointed out that these units
are termed effluent samplers by the manufacturer. However, because
of site conditions and the absence of line current at many sampling
points the section has found it necessary to use these compositors
on raw wastes. It should also be pointed out that the data in
Table II do not include all possible combinations of field team
personnel and, therefore, could be biased as a result of differences
in field routine and individual expertise of team members.
Statistically, the data are too limited to recommend or reject
any particular compositor; however, it is apparent that sampling of
raw wastewaters produces the major number of compositor malfunctions
aftd that considerably more reliable operation can be expected when
sampling treated wastewaters.
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26
TABLE II
INCIDENCE OF SAMPLER MALFUNCTION
Automatic
Wastewater
Sampler
Sigmamotor WA-2
Sigmamotor WD-2
Brail sford DU-1
Brail sford EV-1
Brailsford EP-1
QCEC CVE
Pro-Tech C6-125P
ISCO 1391-X
ISCO 1392
N-Con Scout
N-Con Surveyor
Totals and
Mean Failure
Rates
Total
Times
Used
24
31
45
29
63
90
10
16
17
14
7
346
Total
Times
Failed
6
4
15
5
6
4
4
4
1
2
3
54
Overall
Failure
Rate
Percent
25
13
33
17
10
4
40
25
5
14
43
16
Influent Sampling Stations
Used
8
15
40
26
55
77
Failure
4
2
13
5
6
4
Failure
Rate
Percent
50
13
33
19
11
5
Effluent Sampling Stations
Used
16
16
5
3
8
13
Failure
2
2
2
0
0
0
Failure
Rate
Percent
13
13
40
0
0
0
NOT BROKEN DOWN
t>
16
15
14
5
271
4
1
2
3
44
25
7
14
60
16
0
2
0
2
65
0
0
0
0
6
0
0
0
0
9
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27
The overall ability of the Field Investigations Section to
obtain a complete 24-hr composite sample probably runs between 80
and 84 percent since the 16 percent compositor malfunction rate
does not reflect mistakes in installation, variations in the exper-
tise of different field teams, excessive drops in head, submerging
of compositors, or winter operation.
B. INSTALLATION AND OPERATION OF SAMPLING EQUIPMENT
In the field, the engineering staff works closely with the
technicians. At new locations which have not been previously sam-
pled it is a policy of the Field Investigations Section to have a
professional present to select the sampling point, to inspect the
flow measurement equipment of the facility or determine a suitable
measurement method, and to supervise installation of the sampling
equipment. It is felt that this practice reduces the risk of
compositor malfunction and missed samples, improves the representa-
tiveness of the data, and results in a more detailed and informative
report.
The primary reason for the large variety of compositors used
by the section is due to the plethora of sampling requirements,
waste stream characteristics, and site conditions encountered in
the field. Utilization of the sampling equipment of choice is often
precluded by the physical characteristics of the point of interest
including accessibility, site security, and the availability of
power.
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28
Raw municipal wastewaters are preferably sampled at points of
highly turbulent flow in order to insure good mixing; however, in
many instances the desired location is not accessible. Raw waste
sampling points in order of preference are: (a) the upflow siphon
following a barminutor*, (b) the upflow distribution box following
pumping from main plant wet well, (c) aerated grit chamber, (d)
pump wet well, and (e) flume throat.
In order to provide position stability and to reduce velocity
displacement, a sash weight, sole plate or other weight, secured
with a rope, is tied to the end of the sampler intake tube which is
positioned at mid-depth in the flow.
The section has experienced incidents of theft and vandalism
of equipment. This is an item of major concern at sites which are
outside the confines of fenced treatment facilities. Manhole
installations in which battery-operated equipment can be put in the
manhole and the cover replaced will generally provide sufficient
security. In exposed locations which require composite samples,
one must either risk loss and tampering with equipment or utilize
manual sampling methods. If manpower limitations require use of
unattended equipment, obviously only low-value compositors should
be considered. As "water pollution" is a popular subject with the
general public, tampering with equipment can sometimes be reduced
if people in the area are aware of the nature and purpose of the
"c
activity. One of the authors experienced this situation during a
* In absence of grit chamber
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29
survey of a receiving stream i,n a rural area downstream from a
treatment facility.
In every case the field team will utilize electrical line
current if it is available at the sampling site. Generally, line-
operated compositors are more reliable than battery-operated models
and, in the sampling of raw wastewaters, the incidence of intake
tube plugging is reduced due to the high vacuum and purging feature
of the samplers which are preferably used on these wastes. Line
current has been available at about 50 percent of the treatment
facilities which the section has surveyed. In a survey of over
100 private, municipal, and industrial waste treatment plants in
the greater Kansas City area, only 45 percent of the facilities had
an electrical power source. Power availability at lagoons, which
accounted for 55 percent of the survey, was even less.
The physical and chemical characteristics of the waste stream
also play a part in determining the type of sampler to use. Wide
fluctuations in pH, strength, color, and volume encountered with
some industrial wastewaters will generally require a discrete
sample collector in order that aliquots can be analyzed individ-
ually.
With the exception of cold weather sampling conditions, all
samples are kept on ice during the composite period. The ISCO,
QCEC-CVE, and Sirco units are the only compositors used by the
section which have an integral ice compartment. With the other
units samples are chilled by placing the sample collection container
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30
in an ice chest* along with a 2.27-kg (5-lb) bag of ice. The ice
chest is stood on end with the drain hole on top and the discharge
tube of the sampler is threaded through this hole and into the
sample contained.
Winter operation of sampling equipment can be a trying experi-
ence. During particularly cold weather sampler malfunctions due to
freezing of intake lines may run as high as 60 percent.
If possible, the samplers should be installed in manholes
below the freezing line by taping (fiber glass tape) the unit to
steps or by suspending with a rope tied securely to a stake in the
ground. When installing samplers in manholes or wet wells, care
should be taken to position it at a level which will not result in
submergence of the compositor in the event of precipitation.
Because of the limited suction head of many of the battery-operated
compositors, it is not always possible to maintain an adequate
elevation. If heavy rainfall appears probable, the sampling should
be postponed or use of a Brailsford EP-1 considered. Section per-
sonnel have inadvertently submerged several of these units without
any apparent damage. However, they do admit water to the case and
it is recommended that the backing plate be removed and the interior
of the case allowed to dry prior to additional usage.
If below ground installation is not possible during freezing
weather and line current is available, 1.2- to 1.8-m (4- to 6-ft)
heat tapes** can be wrapped around the sample container and the
* Progress Refrigeration Company, Louisville, Kentucky - Model A-52
** Thermostatically protected 3°C
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31
intake lines. To provide insulation, large plastic bags* can be
wrapped around the intake line and heat tape and loosely placed
over the sampler.
When using the Brailsford EP-1 models where 110 v AC is avail-
able, it is possible to place the entire unit with sample bottle in
an ice chest and wrap a heat tape around the bottle for protection.
If the chest drain plug is removed and the chest set or hung verti-
cally with the drain plug on the bottom, the intake tube can be run
out the drain hole and also heat taped to provide sampling reliably
below 0°C.
As of this writing, the vast majority of the samples collected
by the section (estimated 95 percent) have been time composited.
When flow-proportional sampling is done, discrete samples are
manually composited on the basis of readings from external flow or
level recorders. As a result of data presented and discussed in
Chapter IV, the Field Investigations Section continues to have mixed
opinions regarding flow-proportional samples.
* Airline trash bags, 10 mil, 6SA FSN #8105-848-9631
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32
IV. SAMPLING METHODS AND DATA VARIABILITY
A. PERFORMANCE OF AUTOMATIC WASTEWATER SAMPLING EQUIPMENT
As the Field Investigations Section acquired and gained expe-
rience with a number of different makes and models of commercially
available samplers and with the accumulation of large volumes of
water quality information, discrepancies in data were noted which
appeared to result from variations in compositor performance.
As of this writing, the section has conducted five field
studies for the purpose of comparing the water chemistry data of
samples collected concurrently with the various compositors listed
in Table I. Samples were analyzed according to Standard Methods
(2) for five-day biochemical oxygen demand (BODs), chemical oxygen
demand (COD), and nonfilterable solids (NFS)*. Data obtained from
different compositor combinations were compared to each other and
to those data resulting from manual sampling methods.
1. RICHARDS-GEBAUR AFB STUDY
The AFB is served by a 5,680 cu m/day (1.5 mgd) standard rate
trickling filter plant with effluent chlorination. Three sampling
stations were set up at this plant. The stations were: (a) the
raw waste (upstream of the Parshall flume and digester supernatant
return), (b) the effluent from the primary clarifier, and (c) the
final effluent.
A QCEC ModeJ CVE sampler was installed to collect time-
composite samples (15-min cycle time) at the influent and,
* Also termed total suspended solids
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33
concurrently, an ISCO Model 1391-X was used to collect discrete
samples at 2-hr intervals for manual flow proportioning and com-
positing. Flow measurements were obtained with a Manning Dipper
Stage Recorder* and a staff gage installed in the throat of the
22.9-cm (9-in.) Parshall flume located at the plant influent.
At the effluent of the primary clarifier a Sigmamotor Model
WD-2 compositor was used to collect time-composite samples (15-min
cycle time) and a Hants Mark 3B was used to collect discrete
samples at 2-hr intervals for manual flow proportioning and com-
positing. A 90-degree, V-notch weir equipped with a Manning Dipper
Stage Recorder* and a staff gage was temporarily installed in order
to get flow measurements at this station.
At the plant final effluent a Brails ford DU-1 mechanical
compositor was used to collect time-composite samples (4-min cycle
time) and a Hants Mark 38 sampler was installed to collect samples
at 2-hr intervals for manual flow compositing. For flow measure-
ments a 90-degree, V-notch weir was temporarily installed and
equipped with a Belfort Float Stage Recorder* with stilling well
and staff gage.
At each of the three stations the intake lines of the
compositors were tied together and suspended at mid-depth in the
waste stream. Grab samples were manually collected at 4-hr
intervals .for individual analysis and for flow compositing at each
of the three stations in order to provide additional data for
comparison.
* See Page 95"
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34
Because of plant operation problems, compositor malfunctions,
s
and a heavy rainfall, there were some departures from the planned
sampling effort. On May 21 the plant operators by-passed for two
10-min periods at 1300 and 1400 hr in order to facilitate rodding
out of a clogged digester line. On May 22 a period of heavy rain-
fall occurred between 0030 and 0530 hr with about 5 cm (2 in.) of
total precipitation. The temporary weir at the primary effluent
was submerged for several hr during this period and flow rates were
taken from readings on the Parshall flume located at the influent.
Because of this rainfall the plant by-passed a portion of the raw
waste for a period of nine hr. The total by-passed waste volume
was estimated to be 17,000 cu m (4.5 mil gal). Several afternoon
thundershowers also occurred on May 22 and increased plant flows
but did not necessitate further by-passing.
Difficulty was experienced with the clock mechanism of the
Hants 3B samplers located at the primary and final effluent. At
the primary effluent the flow-composite samples obtained with this
instrument were short two and four hr, respectively, on May 22-23
and 23-24. At the final effluent the May 22-23 composite was short
two hr and on May 23-24 four of the twelve bottles of the Hants
sampler were about twenty to thirty percent short of the volume
necessary to make the flow composite.
In addition to sampler malfunctions, a cursory examination of
the facility during the study revealed the following plant opera-
tional problems:
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35
a. Comminutor seals were gone and large solids passed
the comminutor without removal.
b. Sludge removed from the primary tanks was accom-
panied by large volumes of water which caused
excessive amounts of digester supernatant to be
returned to the plant. During the entire survey
the primary effluent appeared black and septic.
c. Only one trickling filter was in operation and no
recirculation was practiced. There were 27 hourly
periods during the 72-hr survey when plant flows
exceeded the 2,840-cu m/day (0.75-mgd) capacity of
the trickling filter unit. Filter capacity was
exceeded several times each day during the survey
at periods which were not related to rainfall.
d. One of the secondary clarifier units was septic
during the entire investigation and clumps of
sludge up to 15.2 cm (6 in.) in diam continuously
rose to the surface and were discharged with the
clarifier overflow.
All samples were kept on ice and delivered to the EPA, Region
VII, Laboratory where they were analyzed according to Standard
Methods (2). No special attempts were made during the collection
period to refine compositing methods or sample delivery procedures.
In the laboratory, normal personnel assignments and rotations were
observed; consequently, the water chemistry data represented the
work of several professional analysts. These data are presented
in Tables lit, IV, and V. The flow data are shown graphically in
Figure 1.
An examination of Table III, which shows the water chemistry
data of the samples collected from the raw waste by the four dif-
ferent sampling methodologies, would indicate that the results
obtained with the QCEC compositor differed significantly from the
data of samples collected by the other methods. Looking at the
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36
BOD5, COD, and NFS of the grab samples collected manually, it can
be seen that there was a definite decrease in strength of the waste
during the early morning hours. Discounting other factors, the
time-composite samples collected with the QCEC would be expected to
have been biased low because the samples included equal volume
aliquots of the low-flow, low-strength, early-morning waste. How-
ever, for each of the three parameters it is evident that the QCEC
samples were of higher strength than the flow-composited ISCO
samples, the manually-collected flow-composited samples, or the
arithmetic mean of the manually-collected grab samples. In all but
four out of fifty-four analyses for the three parameters, the QCEC
samples were of greater strength than any of the discrete, manually-
collected grab samples.
Table IV, which shows the water chemistry data of samples
collected from the primary effluent, also indicates a bias. Except
for BODs on May 22 and COD on May 23, the flow-composited samples
obtained with the Hants unit were of higher strength than those
flow-composited samples collected manually.
Table V presents the water chemistry data of the final effluent
samples and does not indicate any apparent bias with respect to the
four different sampling techniques.
The NFS data for the three days of sampling are summarized in
Table VI and presented in the form of ratios after unitizing the
results on the basis of the concentrations found in the manually-
collected and flow-composited samples. Examination of this table
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37
TABLE III
RICHARDS-GEBAUR SEWAGE TREATMENT PLANT
RAW WASTE
Date.
May
1973
21-22
22-23
23-24
Sample Type And Time
24-hr Mech Flow Comp (ISCO)
24-hr Mech Time Comp (QCEC)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ± mg/1
Coefficient of Variation, percent
24-hr Mech Flow Comp (ISCO)
24-hr Mech Time Comp (QCEC)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ± mg/1
Coefficient of Variation, percent
24-hr Mech Flow Comp (ISCO)
24-hr Mech Time Comp (QCEC)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ±. mg/1
Coefficient of Variation, percent
Arithmetic Mean Of All Data Points
May 21-22
May 22-23
May 23-24
BOD5
mg/1
95
215
113
124
195
183
165
104
22
73
63
51
84
140
99
97
107
111
162
109
18
74
44
45
153
153
107
98
131
97
153
80
16
no
43
44
123
137
105
128
COD
mg/1
330
588
279
356
492
467
539
238
72
328
163
46
165
388
223
177
171
223
351
143
40
135
95
54
306
526
252
236
282
304
334
197
50 '
250
94
40
319
388
238
330
NFS
mg/1
120
254
121
148
250
278
153
86
68
52
88
60
47 '
126
109
74
128
72
106
62
9
66
37
50
149
186
106
87
107
81
141
80
16
94
38
44
127
161
89
132
-------
38
TABLE IV
RICHARDS-GEBAUR SEWAGE TREATMENT PLANT
PRIMARY EFFLUENT
Date
May
1973
21-22
22-23
23-24
Sample Type And Time
24-hr Mech Flow Comp (Hants)
24-hr Mech Time Comp (Sigmamotor)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ± mg/1
Coefficient of Variation, percent
24-hr Mech Flow Comp (Hants)
24-hr Mech Time Comp (Sigmamotor)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ± mg/1
Coefficient of Variation, percent
24-hr Mech Flow Comp (Hants)
24-hr Mech Time Comp (Sigmamotor)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab : 1 200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ±. mg/1
Coefficient of Variation, percent
Arithmetic Mean- Of All Data Points
May 21-22
May 22-23
May 23-24
BOD5
mg/1
150
97
57
94
127
155
104
no
29
39
45
48
125
100
132
124
102
133
125
117
54
213
47
38
180
175
158
152
126
129
163
160
141
192
23
15
129
99
120
166
COD
mg/1
480
209
151
226
279
309
249
290
139
94
81
36
324
192
264
235
179
243
203
243
145
394
79
34
268
318
318
317
260
296
308
310
324
495
75
23
275
267
253
305
NFS
mg/1
333
83
106
104
112
144
88
82
142
58
32
30
123
56
80
78
80
84
73
60
32
138
32
41
187
125
129
151
96
124
136
128
178
246
49
32
129
156
84
148
-------
TABLE V
RICHARDS-GEBAUR SEWAGE TREATMENT PLANT
FINAL EFFLUENT
39
Date
May
1973
21-22
22-23
23-24
Sample Type And Time
24-hr Mech Flow Comp (Hants)
24-hr Mech Time Comp (Brailsford)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ±_ mg/1
Coefficient of Variation, percent
24-hr Mech Flow Comp (Hants)
24-hr Mech Time Comp (Brailsford)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
• Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ± mg/1
Coefficient of Variation, percent
24-hr Mech Flow Comp -(Hants)
24-hr Mech Time Comp (Brailsford)
24-hr Manual Flow Comp (4-hr Grabs)
Mean of 4-hr Interval Grab Samples
Grab: 1200
1600
2000
2400
0400
0800
Grab Sample Standard Deviation, ± mg/1
Coefficient of Variation, percent
Arithmetic Mean Of All Data Points
May 21-22
May 22-23
May 23-24
BODg
mg/1
43
35
29
28
25
33
25
26
34
27
3.7
14
23
23
16
24
32
27
19
21
—
22
4.7
20
26
17
12
15
11
21
22
14
12
8
5.1
35
24
33
22
18
COD
mg/1
143
137
128
137
143
181
154
141
98
105
28
20
147
137
153
126
146
199
96
109
96
110
37
29
173
181
141
149
133
137
185
173
141
123
22
15
146
136
141
161
NFS
mg/1
84
51
62
59
60
53
51
59
78
56
8.8
15
29
30
39
31
35
49
30
28
16
28
9.9
32
86
76
62
75
86
86
82
78
55
61
12
16
57
64
32
75
-------
40
S 8
o
O
RAW WASTE
o
o
o
-o
"e"
53
O
PRIMARY EFFLUENT
o
o
o
E
ns
o
8
FINAL EFFLUENT
T2002400
flay 21 i
1200 2400 1200
May 22 ' May 23
2400
May 24
FIGURE 1 - Flow Rates - Richards-Gebaur Sewage Treatment Plant
-------
TABLE VI
RICHARDS-6EBAUR SEWAGE TREATMENT PLANT NFS COMPARISON
RATIO OF SAMPLING METHOD VALUE TO MANUAL FLOW VALUE
41
Station
Influent
Primary Effluent
Final Effluent
Sample Method
QCEC
ISCO
Manual Flow
Manual Grab
Hants
Sigmamotor
Manual Flow
Manual Grab
Hants
Brailsford
Manual Flow
Manual Grab
Date
May 21
2.099
0.991
1.0
1.223
3.141
0.783
1.0
0.981
1.354
0.822
1.0
0.951
May 22
1.155
0.431
1.0
0.679
1.537
0.700
1..0
0.975
0.743
0.769
1.0
0.794
May 23
1.755
1.406
1.0
0.820
1.449
0.968
1.0
1.170
1.387
1.225
1.0
1.209
Average
1.669
0.942
1.0
0.907
2.042
0.817
1.0
1.042
1.161
0.939
1.0
0.985
-------
42
would show that in eight out of nine comparisons with the high
vacuum (650- to 700-mm Kg) QCEC and Hants units the solids levels
exceeded those of the manually collected samples. In seven of nine
cases the samples collected by the slower-acting peristaltic and
pfston type compositors (ISCO, Sigmawtor, and Brailsford) yielded
lower solids levels. One could also calculate similar ratios for
BOD5 and COD. These calculations would show that in eight out of
nine and seven out of nine cases for BOD5 and NFS, respectively,
the QCEC and Hants samplers resulted in higher parameter concentra-
tions.
The apparent removal efficiencies of the Richards-Gebaur
facility can be calculated in a number of ways. Table VII shows
the sixteen combinations of sampling methods and removal efficien-
cies resulting from the four 24-hr sampling methods used on the
plant raw waste and final effluent. An examination of this table
would indicate that the apparent removal efficiencies for BODs, COD,
and NFS ranged between 71-89, 39-73, and 36-72 percent, respectively.
The table also shows that apparent removal efficiencies of COD and
NFS with the QCEC on the influent increased significantly and that
there was a corresponding increase in the coefficients of variation.
With the QCEC combinations excluded the mean 6005, COD, and NFS
removals were 77, 43, and 47 percent, respectively. Considering
the QCEC combinations alone these corresponding percentages
increased to 86,*71, and 70 percent, respectively. Considering
all the sixteen combinations of sampling methods the coefficients
-------
TABLE VII
APPARENT REMOVAL EFFICIENCIES OF RICHARDS-GEBAUR FACILITY
WITH VARIOUS COMBINATIONS OF 24-HR SAMPLING METHODS
43
Sample Method Combination
Influent
Manual Flow Comp
ISCO Flow Comp
Mean of Manual Grabs
QCEC Time Comp
Effluent
Manual
Flow Comp
Hants Flow Comp
Mean of Manual Grabs
Brail sford - Time Comp
Manual
Flow Comp
Hants Flow Comp
Mean of Manual Grabs
Brail sford - Time Comp
Manual
Flow Comp
Hants Flow Comp
Mean of Manual Grabs
Brail sford - Time Comp
Manual
Flow Comp
Hants Flow Comp
Mean of Manual Grabs
Brail sford - Time Comp
Mean and Coefficient of
Variation Including QCEC
Combinations
Mean and Coefficient of
Variation Excluding QCEC
Combinations
Mean, mg/1
Coefficient
Variation, %
Mean, mg/1
Coefficient
Variation, %
Mean with QCEC Combination Alone, mg/1
Removal Efficiencies
Percent
BOD5
82
71
79
76
83
72
80
77
82
71
79
76
89
82
87
85
79
6.6
77
5.3
86
COD
44
39
45
39
47
42
49
43
45
40
46
41
72
69
73
70
50
25
43
7.2
71
NFS
52
41
51
54
49
37
48
50
48
36
47
50
71
65
71
72
53
21
47
12
70
-------
44
of variation of the removal efficiencies were 6.6, 25, and 21
percent for BOD5, COD, and NFS, respectively.
Given the present refinement of sampling technology, these
variations in removal efficiencies are believed to be typical of
what can be expected with routine surveys and monitoring programs.
The impact of these variations in determining whether or not a
particular facility is in compliance with permit requirements is
obvious.
The grab sample data in Tables III, IV, and V indicated wide
fluctuations in water chemistry data over a 24-hr period which
decreased as the wastewater passed through the plant. The coeffi-
cient of variation of the NFS data range from 44-60, 30-41, and
15-32 percent, respectively, in the raw waste, primary effluent,
and final effluent.
Table VIII was constructed using the three days of grab
sampling data and the manual, flow-composite data of the raw waste
and the plant final effluent. This^able shows apparent NFS
removal efficiencies as a function of number of grab samples col-
lected per day, time of collection, collection interval (24, 12, 8,
or 4 hr), and the number of days of sampling. These grab sample
efficiencies are compared to the removal efficiencies resulting
from the manual-collected and flow-composited, 24-hr samples. An
examination of this table would indicate that the NFS removal
efficiency as a result of collecting one sample from the influent
and effluent at 2400 hr on the first day of sampling was thirty-one
-------
TABLE VIII
RICHARDS-GEBAUR
NONFILTERABLE SOLIDS REMOVAL EFFICIENCY AS A FUNCTION OF NUMBER OF GRAB SAMPLES, TIME OF COLLECTION, COLLECTION INTERVAL, AND DAYS OF SAMPLING
Sli
I
=3
UJ
.5
LL.
Raw Waste
Days ol
ampling
1st
2nd
M
1st JnrJ 3rd
Erik
Samples
per day
1
2
3
6
24-hr
1
>
3
6
24-hr
1
2
3
i
1
Grab
Sample
Inlenal
(hounl.
14
12
8
4
an Flow
14
12
8
4
in fin
24
12
8
4
24
Slarling
Time
(mil)
1200
1600
2000
1400
0400
0800
1200
1600
2000
1100
1200
Comp.
Fl200
1600
2000
1400
0400
0800
1200
1600
2000
1200
1600
1200
UUP
•|20f
1600
2000
2400
0400
0100
1200
liOO
2000
1200
1600
1200
24-1. Nil. HH Cmp.
tail,
Men
KFS mg/l
60
53
51
59
78
Si
60
66
53
63
56
60
62
35
49
30
28
16
28
32
32
29
27
35
31
39
86
82
18
55
61
82
70
72
74
75
75
62
ally Cum
Mean
NFS mg/l
60
53
SI
59
78
Si
iO
66
53
63
56
iO
62
48
51
40
44
47
42
4i
49
41
45
46
46
51
iO
63
54
55
50
48
58
56
51
55
55
55
54
S
250
150
16
79
10
76
69
18
i
278
278
78
81
81
79
7!
80
r-j
153
153
il
65
61
6!
49
63
1
86
86
30
38
41
31
09
35
g
68
68
11
22
25
13
-IS
18
§
52
52
-15
-02
01
-13
-50
-01
1
11
S
168
168
64
61
68
I
173
173
iS
il
69
1
102
101
41
35
48
3
S
§
157
157
ID
64
i
139
139
55
60
6
4
S
148
148
59
J '
J
£
2
§
121 128
121 189
A
75
73
79
77
75
18
§
72
175
73
71
77
75
73
li
§
f+4
106
129
63
60
69
66
64
67
g
<2
74
35
31
46
41
it
43
i
9
38
-26
-34
-OS
-16
-24
-It
i
66
59
19
14
31
15
20
29
2
12
S
95
132
65
63
69
i
41
107
57
54
62
1
86
94
51
48
56
3
8
S
SI
119
62
61
S
67
103
56
55
6
4
g
74
111
59
24-hr Nan. Flow Cmp
1
24
S
10! 107
115 162
56
63
61
67
66
69
70
i
81
144
58
56
63
62
65
67
1
141
133
55
53
59
59
62
64
i
80
76
21
17
29
28
34
37
|
li
31
-103
-74
-77
-55
i
94
71
li
11
24
23
30
32
, 2
12
§
94
119
51
53
57
§
48
88
34
36
42
I
IIS
102
43
45
50
3
8
I
SS
109
50
50
§
85
97
43
43
6
4
g
86
103
47
24-hr Mai. Flo. Comp.
106
112
52
-------
46
percent. It can be seen that the removal efficiency based on the
'first day 24-hr manual flow composites was 49 percent. In a
similar manner, the treatment efficiency resulting from collecting
one sample per day at 2400 hr for three days from the influent and
effluent was 28 percent based on the mean of the three samples
collected at each station. The mean flow-composite sample effi-
ciency over this three-day period was 52 percent. Table VIII also
shows those efficiencies based on collecting: (a) two samples per
day at 12-hr intervals as a result of collecting the first sample
at 1200, 1600, or 2000 hr, (b) three samples per day at 8-hr
intervals as a result of collecting the first sample at 1200 or
1600 hr, and (c) six samples per day at 4-hr intervals as a result
of collecting the first sample at 1200 hr. All efficiencies on the
diagonal of the table are the result of collecting samples from
each of the two stations at the same time. Those efficiencies
shown below and above the diagonal resulted from the effluent sam-
ples which were collected at multiples of 4-hr intervals following
or preceding collection of the raw waste samples.
The table clearly indicates the fallacy of relying upon single
grab samples and demonstrates that varying collection time will
change apparent plant efficiency over a broad range. Looking at
the efficiencies resulting from collecting one sample per day for
three days it can be seen that the removals ranged from -103 to
+70 percent. It is1 apparent that as the daily frequency of grab
sampling increased the resulting efficiency range narrowed and
-------
47
approached those efficiencies resulting from the manual, flow-
composited samples. Comparing six grab samples per day with the
flow composites for one, two, and three days the differences were
10, 3, and 5 percent, respectively.
The variation in analytical results obtained with different
sampling techniques can be studied in relation to the interlabora-
tory variation resulting from analytical quality control (AQC)
studies. Standard Methods (2) contains a discussion of precision
and accuracy for BODs, COD, and NFS based on the results of a
number of cooperating laboratories analyzing artificially prepared
identical samples. These discussions are excerpted below.
6005 Precision and Accuracy
"There is no standard against which the
accuracy of the BOD test can be measured. To
obtain precision data, a glucose-glutamic acid
mixture was analyzed by 34 laboratories, with
each laboratory using its own seed material
(settled stale sewage). The geometric mean
of all results was 184 mg/1 and the standard
deviation of that mean was ±31 mg/1 (17%).
The precision obtained by a single analyst in
his own laboratory was ±11 mg/1 (5%) at a BOD
of 218 mg/1." (2, p. 494)
COD Precision and Accuracy
"A set of synthetic unknown-samples con-
taining potassium acid phthalate and sodium
chloride was tested by 74 laboratories. At
200 mg/1 COD in the absence of chloride, the
standard deviation was ±13 mg/1 (coefficient
of variation, 6.5%). At 160 mg/1 COD and
100 mg/1 chloride, the standard deviation
was ±10 mg/1 (6.5%), while at 150 mg/1 COD
and 1,000 mg/1 chloride, the standard deviation
was ±14 mg/1 (10.8%).
The accuracy of this method has been
determined by Moore and Associates. For most
-------
48
organic compounds the oxidation is 95 to 100%
of the theoretical value. Benzene, toluene
, and pyridine are not oxidized." (2, p. 499)
NFS Precision and Accuracy
"The precision of the determination varies
directly with the concentration of suspended
matter in the sample. The standard deviation
was ±5.2 mg/1 (coefficient of variation 33%)
at 15 mg/1, ±24 mg/1 (10%) at 242 mg/1, and
±13 mg/1 (7.6%) at 1,707 mg/1 (n = 2; 4 x 10).
There is no satisfactory procedure for obtain-
ing the accuracy of the method on wastewater
samples, since the true concentration of sus-
pended matter is unknown." (2, p. 538)
Table IX was constructed using the coefficients of variation
resulting from the AQC studies reported in Standard Methods (2) and
the water chemistry data of the manually flow-composited samples.
In construction of this table, it was assumed that the manually
flow-composited samples most accurately described actual wastewater
characteristics and that data resulting from the other techniques
were normally distributed about the manual flow analyses. This
table indicates that 62 of the analyses (77 percent) resulting from
the other sampling methods were outside the range of the manual
flow sample data ±1 standard deviation* (s). In a similar manner,
it can be shown that 39 analyses (48 percent) were outside the
range of ±3s. Since the range of ±3s for COD and NFS included all
inter!aboratory analyses (assuming normal distribution) it is
apparent that the variation in data from the Richards-Gebaur study
is greater than can'be explained by laboratory analytical variation
* Arrived at by multiplying manual flow data by Standard Methods
coefficient of variation.
-------
49
TABLE IX
RICHARDS-GEBAUR AIR FORCE BASE STUDY
ANALYSES OUTSIDE RANGE OF MANUAL FLOW-COMPOSITED SAMPLES
HatA
UQ l,C
May
1973
Type Of Sample
Inf 1 U6nt
21-22
22-23
23-24
Manual Flow
ISCO - Flow
Manual Time
QCEC - Time
Manual Flow
ISCO - Flow
Manual Time
QCEC - Time
Manual Flow
ISCO - Flow
Manual Time
QCEC - Time
Primary Effluent
21-22
22-23
23-24
Manual Flow
Hants - Flow
Manual Time
Sigmamotor - Time
Manual Flow
Hants - Flow
Manual Time
Sigmamotor - Time
Manual Flow
Hants - Flow
Manual Time
Sigmamotor - Time
Final Effluent
21-22
22-23
23-24
Manual Flow
Hants - Flow
Manual Time
Brail sford - Time
Manual Flow
Hants - Flow
Manual Time
Brail sford - Time
Manual Flow
Hants - Flow
Manual Time
Brail sford - Time
Analyses out of Range
Analyses Out Of Range (*)
BOD5
Cone.
mg/1
Std.*
Dev.
± mg/1
COD
Cone.
mg/1
Std.*
Dev.
± mg/1
NFS
Cone.
mg/1
Std.*
Dev.
± mg/1
Standard Methods Coefficient of Variation
5%
113
95
124
215
99
84
97
140
107
153
98
153
5.6
*
*
*
5.0
*
*
5.4
*
*
*
6.5%
279
330
356
588
223
165
177
388
252
306
236
526
18.1
*
*
*
14.5
*
*
*
16.4
*
*
10%
121
120
148
254
109
47
63
126
106
149
87
186
12.1
*
*
10.9
*
*
*
10.6
*
*
*
Standard Methods Coefficient of Variation
5%
57
150
94
97
132
125
124
100
158
180
152
175
2.8
*
*
*
6.6
*
*
*
7.9
•*•
*
6.5%
151
480
226
209
264
324
235
192
318
268
317
318
9.8
*
*
*
17.2
*
*
*
20.7
*
10%
106
333
104
83
80
123
78
56
129
187
151
125
10.6
*
*
8.0
*
*
12.9
*
*
Standard Methods Coefficient of Variation
5%
29
43
28
35
16
23
24
23
12
26
15
17
-
1.4
*
*
0.8
*
*
*
0.6
*
*
*
24
6.5%
128
143
137
137
153
147
126
137
141
173
149
181
-
8.3
*
*
*
10.0
*
*
9.2
*
*
22
33%
62
84
59
51
39
29
31
30
62
86
75
76
-
20.5
*
12.9
20.5
*
16
Total
Out Of
Range
8
8
8
8
8
5
6
5
5
62
* Manual flow data multiplied by coefficient of variations reported in
Standard Methods
-------
50
alone. Real variations in sampling methods become particularly
evident when one considers that 17 BODs analyses (63 percent) were
outside the ±3s (3x5 percent) variation reported by a single
laboratory and that the AQC statistical data used for the COD and
NFS comparisons include interlaboratory systematic variation which
was not a factor in the AFB study.
The standard deviation and coefficient of variation of the
three water chemistry parameters resulting from the four sampling
techniques employed at each of the three stations are shown in
Table X. The coefficients of variation are all greater than those
values reported in Standard Methods (2, p. 494, 499, 538) for the
corresponding parameters. Included in the statistical data shown
in Table X would be: (a) differences in compositor performance
and manual sampling methods, (b) actual variations in water quality s
and (c) laboratory analytical random errors.
2. THERESA STREET SEWAGE TREATMENT PLANT - LINCOLN, NEBRASKA
A comparative study of compositor performance was undertaken
at the Theresa Street Sewage Treatment Plant in Lincoln, Nebraska,
June 25 through 28, 1973.
The Theresa Street facility is currently undergoing an exten-
sive expansion with the addition of expanded activated sludge facil-
ities. The present plant is a 113,550-cu m/day (30-mgd) facility
with all wastes receiving preaeration grit removal and primary
clarification. Approximately 18,900 cu m/day (5 mgd) of the flow
is then treated by a trickling filter system while the remaining
-------
TABLE X
STATISTICAL SUMMARY OF RICHARDS-GEBAUR STUDY
Station
Influent
Prinry Effluent
Final Effluent
BOD5
Mean
mg/1
123.3
128.6
24.2
S
t mg/1
35.5
29.2
8.5
Coefficient
Of Variation
Percent
28.7
22.7
35.1
COD
Mean
mg/1
318.8
275.2
146.0
S
t mg/1
125.1
81.5
15.7
Coefficient
Of Variation
Percent
39.2
29.6
10.7
NFS
Mean
mg/1
126.3
129.5
57.0
S
t mg/1
51.7
72.4
20.1
Coefficient
Of Variation
Percent
41.9
55.9
35.3
-------
52
waste is treated by a high rate activated sludge system with
secondary clarifiers.
The three sampling stations selected were the raw waste at the
distribution box to the preaeration tank and the plant final efflu-
ent with one station at the overflow of the secondary clarifiers
and the other at the outfall to Salt Creek. At the influent an
ISCO Model 780 sampler* with an uniced sample container compartment
was set to collect discrete samples at 1-hr intervals for manual
flow compositing each morning between 0730 and 0800 hr. This sam-
pler was installed and operated by city laboratory personnel who
provided a portion of the composited sample to the EPA field inves-
v
tigations team each morning. Concurrently, the EPA field team used
a QCEC-CVE compositor with icecl sample chamber at the same sampling
point. This sampler was set to take 25-ml sample aliquots at
14-min intervals. A portion of this time-composite sample was
split with city laboratory personnel.
The EPA field team used a Brails ford DU-1 (6-min cycle time)
with an iced sample chamber set to collect final effluent samples
at the secondary clarifiers. A portion of this sample was given
to city laboratory personnel. At the outfall to Salt Creek city
personnel used an ISCO Model 780 compositor with an uniced sample
compartment to collect discrete samples at 1-hr intervals for manual
flow compositing according to hourly readings taken from the plant
influent flow recorder. A portion of this composite sample was
supplied to the EPA field team.
* Similar to Model 1391 but not suitable for manhole installation
-------
53
Table XI presents the results and arithmetic means of the
analyses reported by the EPA, Region VII, Laboratory on the samples
collected by the city and by EPA. An examination of this table
would show that the 8005, COD, and NFS concentrations of the raw
waste samples collected with the QCEC compositor were, respectively,
125, 134, and 182 percent greater than the levels found in the sam-
ples collected with the ISCO unit. The corresponding percentages
for the effluent samples were 104, 129, and 92.
3. ASHLAND, NEBRASKA, SEWAGE TREATMENT PLANT
A third comparison study was conducted at the Ashland,
Nebraska, sewage treatment plant during the week of July 28, 1973.
An ISCO Model 1391 and a Hants Mark 3B sampler were paired
and set to simultaneously sample the raw waste in the throat of a
15.24-cm (6-in.) Parshall flume and the final effluent at the dis-
charge of the chlorine contact chamber overflow weir. The intake
lines of the samplers were tied together and suspended at mid depth
at each of the two stations. The instruments collected discrete
samples at 2-hr intervals which were manually flow composited
according to the flow recordings of the influent Parshall flume.
The data resulting from the 5-day sampling effort at the
influent and effluent are shown in Tables XII and XIII, respectively.
The variation in wastewater chemistry data resulting from the two
different compositors is apparent. The arithmetic mean BODs, COD,
and NFS concentrations of the raw waste samples collected with the
Hants compositor were, respectively, 179, 183, and 334 percent
-------
54
TABLE XI
THERESA STREET SEWAGE TREATMENT PLANT
LINCOLN, NEBRASKA
WASTEWATER CHARACTERIZATION
Station And
Compositor
Influent
ISCO-780
City Operated
Influent
QCEC-CVE
EPA Operated
Effluent
ISCO-780
City Operated
Effluent
Brailsford
EPA Operated
• Influent '
Effluent
Date
June
1973
25-26
26-27
27-28
Time
Military
0800 To 0800
0800 To 0800
0800 To 0800
Arithmetic Mean
25-26
26-27
27-28
1025 To 0945
0945 To 0745
0745 To 0745
Arithmetic Mean
25-26
26-27
27-28
0800 To 0800
0800 To 0800
0800 To 0800
Arithmetic Mean
25-26
26-27
27-28
1015 To 1015
1015 To 0750
0750 To 0755
Arithmetic Mean
Mean QCEC Data Y ,nn
Mean ISCO Data A luu>
Mean Brailsford Data
Mean ISCO Data '
Flow*
cu m/day
103,000
104,000
108,000
105,000
--
—
;;
--
—
--
%
( 100, %
BOD5
mg/1
335
360
173
289
310
465
310
362
37
51
57
48
80
48
22
50
125
104
COD
mg/1
536
598
661
598
875
610
924
803
107
92
106
102
188
88
121
132
134
129
NFS
mg/1
186
190
192
189
385
328
322
345
53
31
32
39
58
16
35
36
182
92
Multiply by 264.2 to obtain gpd
-------
TABLE XII
ASHLAND, NEBRASKA, SEWAGE TREATMENT PLANT
RAW WASTE
Date
July
1973
23-24
24-25
25-26
26-27
27-28*
Arithmetic Mean
BOD/COD-BOD/NFS Ratio
W-xioo, %
BOD5
mg/1
ISCO
180
136
277
258
~
213
~
Hants
220
246
520
450
470
381
-
179
COD
mg/1
ISCO
622
424
728/688
556
-
604
0.35
Hants
1 ,064/900
669
1,744
972
1,270
1,103
0.34
183
NFS
mg/1
ISCO
180
no
320
300
—
228
0.94
Hants
476
330
805
ago
1,335
761
Q.50
334
ISCO Compositor Malfunctioned
en
en
-------
56
TABLE XIII
ASHLAND, NEBRASKA, SEWAGE TREATMENT PLANT
FINAL EFFLUENT
Date
July
1973
23-24
24-25
25-26
26-27
27-28
Arithmetic Mean
BOD/COD-BOD/NFS Ratio
Hants v inn *
1SCU~X 100' %
BOD5
mg/1
ISCO
13
15
22
8
6
13
--
Hants
22
10
39
17
11
20
-
154
COD
mg/1
ISCO
41
29
28
32
36
33
0.39
Hants
65
45
44
40
48
48
0.42
146
NFS
mg/1
ISCO
8
<1
2
3
10
5
2.6
Hants
3
5
9
10
27
11
1.8
220
-------
57
higher than the values resulting from these samples collected with
the ISCO compositor. The effluent samples also indicated a signifi-
cant difference in compositor performance with the 8005, COD, and
NFS values resulting from use of the Hants compositor being,
respectively, 154, 146, and 220 percent greater than the concentra-
tions of the samples values collected with the ISCO sampler.
Tables XII and XIII show that the BOD5/COD ratios of the raw
waste samples collected with the ISCO and Hants compositors were
0.39 and 0.42, respectively. These ratios were 0.35 and 0.34 for
the effluent samples. The close agreement between those ratios
indicates high laboratory analytical quality control and further
emphasizes real differences in sampling efficiency between the two
compositors.
Table XIV presents the apparent removal efficiencies of the
Ashland sewage treatment plant for the three parameters using each
of the four possible combinations of compositors. It can be seen
that the removal efficiency for BODs, COD, and NFS range between
91-97, 92-97, and 95-99 percent, respectively.
4. KANSAS CITY, KANSAS, KAW POINT SEWAGE TREATMENT PLANT -
OCTOBER 1973
A fourth comparison test was conducted on October 10 and 11,
1973, at the Kansas City, Kansas, Kaw Point primary sewage treat-
ment plant.
Three samplers were installed and set to time composite the
raw waste of the plant for a period of about 20 hr at a point
immediately upstream from the bar screens. The compositors used
-------
TABLE XIV
APPARENT REMOVAL EFFICIENCIES OF
ASHLAND, NEBRASKA, SEWAGE TREATMENT PLANT
in
oo
Compositor Combination
Influent
I SCO
ISCO
Hants
Hants
Effluent
ISCO
Hants
Hants
ISCO
Parameter
Percent Removal
BOD 5
Percent
94
91
95
97
COD
Percent
95
92
96
97
NFS
Percent
98
95
99
99
-------
59
included a QCEC Model CVE, a Sircb MKV7S, and an ISCO Model 1391.
These compositors, the intake lines of which were tied together and
suspended about 46 cm (18 in.) below the liquid surface, collected
equal volume aliquots at intervals of 15, 40, and 60 min, respec-
tively.
The collected samples were delivered to the EPA, Region VII,
Laboratory where duplicate analyses for NFS were run. The results
of those analyses are indicated below.
Cpjpj3srto_r
QCEC
Si rco
ISCO
NFS
mg/1
1,250
1,080
760
680
644
520
Mean
NFS
mg/1
1,160
720
582
It can be seen that the Sirco unit produced samples with NFS
data intermediate between those values resulting from the ISCO and
QCEC compositors. Referring back to Table I (page 11), it can be
seen that the liquid intake velocity of the Sirco unit also lies
between the velocities of the other two samplers.
5. KANSAS CITY, KANSAS, KAW POINT SEWAGE TREATMENT PLANT -
DECEMBER 17-19, 1973
A more comprehensive comparison study was conducted at the
Kaw Point sewage treatment plant during December 17, 18, and 19,
1973. Sixteen different methods, including four manual sampling
techniques, and twelve different makes and models of automatic
-------
60
compositors were employed to concurrently sample the raw waste of
this facility.
Time and flow-proportional samples were collected and com-
posited manually at 2-hr intervals using a bucket as well as a
submersible pump*. This variation in manual sampling methods was
introduced to determine if solids were settling out in the bucket
during transfer from the waste stream to the laboratory sample con-
tainers. Using the submersible pump, samples were pumped directly
from the source to the contatner.
The twelve samplers, the intake lines of which were tied
together and suspended in the middle of the waste stream, were used
to take time-composite samples by drawing equal volume aliquots at
intervals which ranged from continuous up to 1 hr. Samples were
collected over a period of approximately 24 hr on both December
17-18 and 18-19. With the exception of an N-Con Sentinel sampler
which has a refrigerated sample container compartment and which was
provided courtesy of the manufacturer, none of the samples were
kept refrigerated during the sampling period. The collected sam-
ples were analyzed by the EPA, Region VII, Laboratory for BODs
(December 18-19 only), COD, and NFS which were run in duplicate.
Random laboratory analytical errors for NFS were minimized by
drawing aliquots with a wide-mouthed pipette from the samples
during agitation with a magnetic stirrer.
* Tee! Submersible Pump,.Model 1P809, Dayton Electric
Manufacturing Company, Chicago, Illinois 60648
-------
61
The results of the comparison test are presented in Table XV
and are arranged according to the liquid intake velocity of the
particular technique or compositor used. An examination of this
table would indicate that there was no correlation between concen-
tration of parameter and liquid intake velocity. Calculation would
also show that there was no correlation between cross-sectional
area of the intake line and concentration nor between an intake
tube cross-sectional area-velocity product factor and concentration.
The data resulting from this comparison test do not support those
results obtained in previous tests and the reason for this is not
entirely understood. The nature of the waste which included meat
processing scraps, soap, grease, and fiber glass was probably a
contributing factor. Without constant attention upon the part of
the two sanitary engineers who were on duty throughout the sampling
period, most of the compositors would have failed. Over the two-
day period the following equipment malfunctions were noted and
corrected:
Brailsford EP-1 - Cleaned eight times, solids visibly
accumulated in the bottom of loops in the intake hose
during the entire sampling period.
Sigmamotor WA-2 - Clogged three times, cleaned with
compressed air.
ISCO 1391-X - Completely clogged twice and one bottle
short on the first day, four bottles empty on the
second day.
N-Con Surveyor - Completely clogged six times with
meat and skin scraps at the constriction on the intake
side of the pump.
-------
TABLE XV
RAW DATA AND STATISTICAL SUMMARY OF SAMPLER COMPARISON STUDY AT
KANSAS CITY, KANSAS, KAW POINT SEWAGE TREATMENT PLANT
Sampling Method
Or Compositor
1. Manual Sampling - Bucket
2. Manual Sampling - Bucket
3. Brailsford EP-1
4. Sigmamotor WA-2
5. ISCO Model 1391-X
6. N-Con Surveyor
7. ISCO Model 1392
8. QCEC-CVE
9. QCEC-CVE
10. Sirco MKV7s'b^
11. QCEC-CVE
12. QCEC-CVE
13. Pro-Tech C6-150
14. Manual Sampling - Pump
15. Manual Sampling - Pump
16. N-Con Sentinel (b)
Intake
Velocity
cm/sec^3'
_
-
0.46
7.9
21
36
61
61
91
98
122
152
207
300
300
332
Time
Or
Flow
Composite
Time
Flow
Time
Time
Time
Time
Time
Time
Time
Time
Time
Time
Time
Time
Flow
Time
Arithmetic Mean, mg/1
Standard Deviation (s), ±mg/l
Coefficient of Variation, Percent
Methods Out of Range(°)
Standard Deviation Due to Sampling (S^), tmg/1
Arithmetic Mean Excluding Brailsford EP-1, mg/1
Standard Deviation (s), ±mg/l
Coefficient of Variation, Percent
Methods Out of Range(c)
Standard Deviation Due to Sample (Sb), ±tng/l
BOD5
Dec. 18-19
mg/1
630
800
550
720
620
780
680
680
710
700
490
560
740
590
590
700
660
84
13
9
--
670
82
13
8
-
COD, mg/1
Date
Dec. 1973
17-18
3,190
3,170
3,580
2,040
2,950
3,680
2,220
3,170
2,770
3,050
2,770
2,750
3,000
2,670
2,730
2,690
2,900
412
14
5
-
2,860
385
13
7
-
18-19
2,120
2,030
1,530
1,960
2,180
1,990
2,400
2,470
2,560
2,250
2,060
1,840
2,090
1,730
1,750
1,890
2,050
270
13
6
-
2,090
242
12
5
-
Mean
2,660
2,600
2,560
2,000
2,560
2,840
2,310
2,820
2,660
2,650
2,420
2,300
2,540
2,200
2,240
2,290
2,480
229
9
7
-
2,470
235
10
6
-
NFS, mg/?
Dec. 17-18, 1973
Determination
1
1,280
1,240
390
810
1,200
940
950
1,310
1,410
910
1,080
1,080
1,250
1,080
1,150
980
1,070
23}
22
5
214
1,110
165
15
5
130
2
1,410
1,530
420
840
1,330
960
930
1,310
1 ,700
1,070
1,190
1,080
1,280
1,080
1,180
1,030
1,150
289
25
8
271
1,190
227
19
9
203
Mean
1,340
1,380
400
820
1,260
950
940
1,310
1,560
990
1,140
1,080
1,260
1,080
1,160
1,000
1,100
260
24
6
240
1,150
193
17
8
164
Diff.
h-zi
130
290
30
30
130
20
20
0
290
160
no
0
30
0
30
50
82
-
-
-
-
86
-
-
-
-
Dec. 18-19, 1973
Determination
1
1,060
1,250
420
1,380
1,070
830
990
1,080
1,240
1,150
1,000
1,000
1,060
970
930
950
1,020
204
20
6
177
1 ,060
137
13
11
92
2
1,010
1,100
440
920
1,000
840
1,020
1,100
1 ,330
960
1,320
1,000
1,070
830
870
950
985
198
20
5
170
1,020
144
14
6
102
Mean
1,040
1,180
430
1,150
1,040
840
1,000
1,090
1,280
1,060
1,160
1,000
1,060
900
900
950
1,000
185
r 18
5
155
1,040
115
11
8
55
Diff.
|l-2
50
150
20
460
70
10
30
20
90
190
320
0
10
140
60
0
101
-
-
-
-
107
-
-
-
-
(a)'Multiply by 0.0328 to obtain fps
(b) Provided courtesy of the manufacturer
(c) Range is result from manual flow sampling with bucket + coefficient of variation'
Oi
IN3
-------
63
ISCO 1392 - Clogged once, three bottles empty and
three short on the first day - two bottles empty on
the second day.
QCEC-CVE (61 cm/sec) - Clogged once, cleaned with
compressed air.
Sirco MKV7S - One bottle short the first day - sampler
time appeared to be about twenty percent fast as all
twenty-four bottles were filled in nineteen hours.
Pro-Tech (6-150) - Clogged completely four times and
cleaned by reversing inlet and outlet lines for one
sample cycle.
Teel Submersible Pump - Twenty-four failures due
primarily to fiber glass batting clumps and in
several instances grease.
It is apparent that only the three QCEC samplers which were
operated at liquid intake velocities above 61 cm/sec (2 fps) and
the N-Con Sentinel performed satisfactorily.
It is felt that the high solids level in the wastewater, par-
ticularly the fiber glass, may have acted as a straining mechanism
in the tubes and orifices of the various compositors to an extent
that would have masked those effects due to liquid intake velocity.
With the exception of the December 18-19 CQD data, the flow-
proportional samples collected with a bucket were of higher strength
than the arithmetic mean of the concentrations found in the samples
collected by other methods. Looking at the arithmetic mean of the
NFS data for each method, it can be seen that only one compositor
(QCEC-CVE set at 91 cm/sec) produced higher strength samples than
those resulting from manual flow-proportional sampling with a
bucket. If this manual technique is assumed to be the most accurate,
-------
64
it is apparent that the data resulting from the other methods are
not normally distributed.
Because the results obtained with the Brailsford EP-1 (method
3} differed significantly from the other data, the mean, standard
deviation (s), and the coefficient of variation were calculated
with and without the Brailsford data. Except for the December
17-18 COD data, deletion of the Brailsford results increased the
mean and decreased the s. Looking at the NFS s, it can be seen
that excluding the Brailsford data resulted in throwing more of
the compositor data outside the range of the manual flow data ±
one standard deviation.
The duplicate analyses for NFS made it possible to determine
the variation due to random laboratory error and that which could
be attributed to variations in sampler performance. Using the
method developed by Youden (3) for statistical analysis of inter-
laboratory collaborative tests, the standard deviation due to
variations in sampler performance can be calculated from the
equations:
s2 = sh2 + sr2 Formula (1)
where:
Formula (2)
s = standard deviation of the raw data
sb"= standard deviation due to variations in
sampling technique and compositor per-
formance
-------
65
sr = standard deviation due to random
laboratory analytical error
d = absolute value of difference between
duplicate analyses
n = number of samples
Because taking the difference between duplicates cancels out
all factors affecting data variability except those due to random
laboratory error, a single estimate of sr can be obtained using the
data for both days (n = 32). Using the differences calculated in
Table XV it can be shown that sr for the NFS data is equal to ±101
mg/1. Solving Formula (1) for s^ and using the s of the raw data
it is a simple matter to calculate 55. These values are shown in
Table XV for the NFS raw data with and without the Brailsford
results. Disregarding the means of the duplicate analysis it can
be seen that s^ ranged from ±92 to 271 mg/1. Computation would
show that the coefficient of variation due to sample performance
varied from 9 to 22 percent.
B. COMPARISON OF TWO MANUAL GRAB SAMPLING-METHODS
In addition to variations in water chemistry data resulting
from differences in performances of automatic wastewater composi-
tors, the Field Investigations staff has also found evidence of
data variability due to different manual grab sampling techniques.
The data shown in Tables XVI and XVII and presented graphi-
cally in Figures 2 and 3 were extracted from an "ongoing" study of
an extraneous flow facility. This facility, which is essentially
a primary treatment plant, is activated by the rising water level
-------
66
in a sanitary sewer resulting from storm water infiltration. This
unit takes flows in excess of sewer capacity, chlorinates, and pro-
vides approximately thirty minutes of sedimentation. The clarifier
overflow is piped to a stream and the settled solids are returned
to the sewer. The raw waste to this facility is residential in
character and becomes progressively weaker in strength as rainfall
and infiltration continue.
The influent and effluent of this facility have been sampled on
three separate occasions during suitable rainfall events. The data
shown in Tables XVI and XVII were selected from the raw waste sam-
pling results from the first two events. During the first event
(September 7, 1972) the raw waste was sampled with a bucket at
10-min intervals from the time the clarifier started filling.
During the second event (November 6, 1972) the raw waste was sam-
pled with a submersible pump* suspended at mid depth in the entering
waste stream. During the first event, five laboratory containers
were filled from the bucket. During the second event, the five
containers were filled directly from the discharge end of the pump
hose which had an estimated liquid velocity of 4.4 m/sec (14.4 fps).
In the laboratory, aliquots for BOD5 and NFS determinations were
extracted from the same sample container. Aliquots for COD analysis
were taken from a separate, preserved, sample.
Comparing Tables XVI and XVII, it can be seen that the duration
of sampling was longer for the second event and that there was a
* Tee! Submersible Pump; Model 1P809, Dayton Electric
Manufacturing Company, Chicago, Illinois 60648
-------
67
TABLE XVI
INFLUENT - EXTRANEOUS FLOW PROJECT - SEPTEMBER 7, 1972
GRAB SAMPLING WITH BUCKET
Time
Military
1030
1035
1040
1050
1100
mo
1120
1130
1140
1150
1200
1210
1220
1230
1240
1250
1300
1310
1320
1330
1340
1350
1400
1410
1420
1430
1440
1450
. 1500
1510
1520
Elapsed Time
Hours + Minutes
00 + 00
00 H- 05
00 + 10
00 + 20
00 + 30
00 +• 40
00 + 50
01 + 00
01 + 10
01 + 20
01 + 30
01 + 40
01 + 50
02 + 00
02 + 10
02 + 20
02 + 30
02 + 40
02 + 50
03 +• 00
03 + 10
03 + 20
03 + 30
03 + 40
03 + 50
04 + 00
04 + 10
04 + 20
04 + 30
04 + 40
04 + 50
Mean
Standard Deviation (s)
BOD5
mg/1
170
185
185
155
170
198
188
163
165
153
168
203
170
215
160
188
273
215
235
230
255
253
235
268
225
205
253
243
265
213
225
207
±36
COD
rng/1
271
427
247
199
632
389
228
226
156
330
192
178
175
194
148
182
190
154
205
203
224
233
207
205
233
195
207
218
247
177
171
234
±95
NFS
mg/1
308
320
312
288
220
388
288
192
168
176
188
120
156
308
152
268
728
216
180
104
728
204
212
200
200
116
124
148
276
144
132
244
±145
Ratio
0.63
0.43
0.75
0.78
0.27
0.51
0.82
0.72
1.06
0.46
0.88
1.14
0.97
1.11
1.08
1.03
1.43
1.40
1.15
1.13
1.14
1.08
1.14
1.31
0.96
1.05
1.22
1.11
1.07
1.20
1.31
0.98
±0.30
-------
68
TABLE XVII
INFLUENT - EXTRANEOUS FLOW'PROJECT - NOVEMBER 6, 1972
GRAB SAMPLING WITH SUBMERSIBLE PUMP
Time
Military
1025
1035
1045
1055
1105
1115
1125
1135
1145
1155
1205
1215
1225
1235
1245
1255
1305
1315
1325
1355
1425
1455
1525
Elapsed Time
Hours + Minutes
00 + 00
00 + 10
00 + 20
00 + 30
00 + 40
00 + 50
01 * 00
01 + 10
01 + 20
01 + 30
01 + 40
01 + 50
02 + 00
02 + 10
02 + 20
02 + 30
02 + 40
02 + 50
03 + 00
03 + 30
04 + 00
04 + 30
05 + 00
Mean
Standard Deviation (s)
1555
1625
1655
1725
' 1755
1825
1855
1925 ''
1955-
2025
2055
2125
05 + 30
06 + 00
06 + 30
07 + 00
07 + 30
08 + 00
08 + 30
09 + 00
09 + 30
10 + 00
10 + 30
11 + 00
BODg
mg/1
255
203
230
303
275
243
195
245
233
188
190
213
145
148
137
140
105
110
130
90
105
110
80
177
± 63
70
118
115
100
100
165
115
140
180
150
168
153
COD
mg/1
416
404
446
544
435
412
879
577
492
356
456
414
326
257
289
305
213
285
180
159
150
183
148
362
±167
115
181
142
140
162
144
167
204
225
252
302
263
NFS
mg/1
192
172
216
320
276
264
400
360
352
356
284
332
290
230
220
174
174
142
102
94
84
70
54
224
±101
44
54
41
37
32
38
35
39
38
40
68
41
BOD
COD
Ratio
0.61
0.50
0.52
0.56
0.63
0.59
0.22
0.42
0.47
'0.53
0.42
0.51
0.44
0.58
0.47
0.46
0.49
0.38
0.72
0.57
0.70
0.60
0.54
0.52
±0.11
0.61
0.65
0.81
0.71
0.62
1.14
0.68
0.69
0.80
0.59
0.56
0.58
-------
Concentration mg/1 BODs, COD, NFS
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BOD/COD Ratio
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Concentration mg/1 BODs, COD, NFS
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-------
71
progressive decrease in strength of the raw waste over this longer
time period. Consequently, the water chemistry data are compared
over the approximate same elapsed time period.
Figure 2 shows the fate of BOD5, COD, and NFS levels with time
for the first event and indicates that the concentrations, parti-
cularly NFS, did not follow or reflect each other very well and
that 19 of the 31 sets of grab samples collected (61 percent) had
BOD5/COD ratios greater than unity. The mean BOD/COD ratio was
0.98 with a standard deviation (s) of ±0.30. Figure 3, which shows
the data for the second event using the submersible pump, indicates
that there was an improvement in the manner in which the parameters
followed each other and that only one data point out of thirty-five
had a BOD5/COD ratio greater than one. An evaluation of the data
from the second event over the same elapsed time period as that of
the first event resulted in a mean BOD/COD ratio of 0.52 with a s
of ±0.11. Table XVII also shows a decrease in the s of the NFS
data from ±145 mg/1 to ±101 mg/1.
A BOD5/COD ratio greater than unity is never encountered in a
domestic waste and very seldom encountered in an industrial waste.
The raw waste of this facility originates in a residential area
with no known industrial wastes or toxicants which would affect
BOD5 values. Analyses from the first event which are not repro-
duced here indicated only negligible concentrations of heavy metals
and a mean effluent BOD5/COD ratio of 0.68 (twenty-four samples)
with all ratios less than one.
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72
Although these two events were completely independent and the
data from the first event could conceivably represent actual waste-
water characteristics, the data resulting from use of the bucket is
at least questionable. Comparing the two events, it can be seen
that there was a decline in BODs and NFS concentrations of the
samples collected during the second event; however, the NFS/BODs
ratios, which were 1.18 and 1.27 for event 1 and 2, respectively,
were in approximate agreement. Although the BODs and NFS levels
decreased during the second event, there was a 55 percent increase
in COD. Since it is impossible to agitate the contents of a pail
and fill a small-mouthed container simultaneously, it is believed
that use of the bucket to collect samples allowed some of the
heavier, nonbiodegradable solids to settle out. The high discharge
velocity of the pump is believed to have effectively prevented any
settlement and to have resulted in a more representative sample.
Data comparison from these two events cast suspicion upon
manual methods of sampling which involved dipping of samples out
of raw waste sources and, consequently, raised the question of
whether or not manual grab sampling is a suitable "yardstick" for
evaluating the performance of automatic wastewater samplers.
C. INTERLABORATORY VARIATIONS
On April 15 through 18, 1973, Field Investigations personnel
conducted a performance test at the 113,500-cu m/day (30-mgd) Kaw
?s.
Point primary wastewater treatment plant in Kansas City, Kansas.
Two Hants 3B samplers were installed at the influent and were timed
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73
to alternately collect samples at'hourly intervals. An ISCO 1391-X
compositor was installed at the effluent and set to collect samples
at hourly intervals. Between 0800 and 1000 hr each morning the
discrete samples collected at each of the two stations were manu-
ally composited according to the hourly pumping rate records for
the three influent pumps serving the plant. The composited samples,
with no preservation other than icing, were split between the
treatment plant laboratory and the EPA, Region VII, Laboratory for
analysis.
In addition to the flow-proportional composite samples, two
grab samples were manually collected each morning at both of the
sampling stations. During the last 24-hr composite period, grab
samples were collected at 2-hr intervals from the influent and
analyzed for COD. The grab samples were not split with city per-
sonnel.
The data resulting from this investigation are presented in
Table XVIII which also shows the calculated removal efficiencies
for the three parameters using the EPA and city analyses of the
composite samples and the EPA analyses of the grab samples. An
examination of this table would indicate wide ranges in removal
efficiencies as a result of variations in interlaboratory analyses
and grab sample characteristics.
It can be seen that the greatest interlaboratory variation
was in COD analysis. The four-day arithmetic mean COD of the
influent samples analyzed by EPA and the city was 1,990 and 1,030
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74
TABLE XVIII
INTERLABORATORY ANALYTICAL AND SAMPLE VARIATION
KAW POINT SEWAGE TREATMENT PLANT - KANSAS CITY, KANSAS
APRIL 1973
Station
Influent
Effluent
Percent R
Influent
Effluent
Percent Re
Influent
Effluent
Sample Collection Times
Grab
Samples
Date
15
15
15
15
moval
16
16
16
16
moval
17
17
17
17
Time
0835
0910
0855
0925
0835
0945
0830
0940
0825
0855
0815
0900
Compc
t
Measur
Dates
14-15
14-15
15-16
15-16
16-17
16-17
Percent Removal
Influent
Effluent
18
18
18
18
0815
0845
0805
0835
17-18
17-18
site Sample
Ind Flow
ement Period
Time
Period
1000-0800
1000-080o'b'
1100-090010'
1000-0900
Flow Rate
cu m/min
Max
129
119
1000- 08001"'
1000-0900 '
1000-0800*e'
1000-0900
106
81
Nin
20
43
38
43
a)
Mean
69
83
63
61
Percent Removal
Four-Day Arithmetic Means
Influent, mg/1
Effluent, mg/1
Percent Removal
Inf 1 uent
17
17
17
17
17
17
17
17
18
18
18
18
Arithmetic
Standard De
Coefficient
1000
1200
1400
1600
1800
2000
2200
2400
0200
0400
0600
0800
BOD, mg/1
Grab
Sampl e
(Mean)
41
175
(108)
96
96
(96)
11
216
540
(378)
150
260
(205)
46
690
485
(588)
250
360
(305)
48
520
650
(585)
300
340
(320)
45
415
231
44
Composite
Sample
EPA
140
97
31
369
104
72
530
270
49
800
430
46
460
225
51
City
186
100
46
488
66
86
651
287
56
858
398
54
546
213
61
COD, mg/1
Grab
Sample
(Mean)
148
527
(338)
250
319
(284)
16
1,020
1,890
(1,455)
330
580
(455)
69
2,300
2,000
(2,150)
570
650
(610)
72
750
1,460
(1,105)
645
675
(660)
40
1,260
502
60
Mean, mg/1
viation, i mg/1
of Variation, Percent
Composite
Sample
EPA
440
318
28
2,320
310
87
2,890
670
77
2,300
785
66
1,990
521
74
2,270
1,050
2,180
2,950
1,820
2,020
1,030
2,110
1,400
1,560
1,540
1,810
545
30
City
420
301
28
493
1,522
596
61
1,681
868
48
1,030
588
43
NFS, mg/1
Grab
Sample
(Mean)
110
148
(129)
76
94
(85)
34
300
1,050
(675)
150
290
(220)
67
430
476
(453)
132
196
(164)
64
184
660
(422)
120
136
(128)
70
420
149
65
Composite
Sample
EPA
696
80
89
2,080
112
95
2,310
204
91
2,250
188
92
1,830
146
92
City
1,620
96
94
1,450
80
94
1,340
144
89
1,220
166
86
1,410
122
91
(a) Multiply by 264.2 to obtain gpm. Flow rate error estimated at +15 to 20 percent.
(b) Nine bottles empty on 24-hr composite
Aliquot collected at 1500 hr was 300 ml short
,_ Aliquot collected at 1400 hr was 200 ml short
(e Five bottles empty on 24-hr comj&site, 7 hr of flow data missing
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75
mg/1, respectively. On April 15 and 16 the variation was even more
pronounced with concentrations of 2,320 and 493 mg/1, respectively.
This difference is in excess of inter!aboratory variations reported
in Standard Methods (2, p. 499). Investigation of laboratory tech-
nique revealed that the EPA laboratory used larger aliquots which
were either drawn from a well-mixed sample with an open tip pipette
or poured into a graduated cylinder. The manner in which these
larger aliquots were drawn is believed to have resulted in greater
and more representativeness amounts of nonfilterable residue.
The data clearly indicate the inadequacy of relying upon a
limited number of grab samples for determining wastewater charac-
teristics or plant performance. In every case, the removal
efficiencies calculated from the grab sample data were less than
those efficiencies determined from the composite sample data
reported by the two laboratories. The COD analyses of the raw
waste grab samples collected at 2-hr intervals April 17-18 ranged
from 1,030 to 2,950 mg/1, had a mean of 1,810 mg/1, and a standard
deviation of ±545 mg/1 (coefficient of variation, thirty percent).
D. SUMMARY AND DISCUSSION
1. SAMPLER PERFORMANCE
In every case, the sampler comparison studies on raw waste
indicated variations in water chemistry data which were greater
than could be explained by laboratory analytical error. This
variation was particularly marked with the NFS parameter. The
Richards-Gebaur study resulted in data which showed that in eight
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76
of nine cases the high-vacuum, high-liquid intake velocity Hants
3B and QCEC-CVE samplers produced time-composite samples with NFS
levels that range from 15 to 214 percent greater than the concen-
trations found in manually-collected, flow-composited samples.
Nonfilterable solids concentration in the raw waste samples
collected with the QCEC compositor range from 15 to 100 percent
greater than the levels present in those samples collected manu-
ally. This sampler was used to collect time-composite samples
which included equal volumes of the early morning low-flow, low-
strength waste that would, in theory, have biased the sample low
in relation to the flow composites.
A statistical analysis of all the raw waste data resulting
from the three-day Richards-Gebaur study resulted in coefficients
of variation of 29, 39, and 42 percent, respectively, for 6005,
COD, and NFS. Included in this variation were: (a) actual changes
in wastewater characteristics, (b) differences in sampler perfor-
mance and manual techniques, (c) field errors in manual compositing
methods, and (d) laboratory random analytical errors. Standard
Methods reports (2, p. 494, 499, 538) coefficients of variation of
5, 6.5, and 10 to 33 percent, respectively, for these three
parameters as a result of inter!aboratory analytical collaborative
tests on identical samples. As an estimate of the analytical error
which could be expected from a single laboratory, the Standard
Methods variance*for COD and NFS are high since systematic errors
of a number of laboratories are included. It is apparent that the
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77
major source of data variability is due to actual changes in water
chemistry and field techniques.
The comparison study of the QCEC-CVE and ISCO samplers at the
Theresa Street sewage treatment plant in Lincoln, Nebraska, showed
that the QCEC compositor produced time-composite samples that were,
respectively, 125, 134, and 182 percent higher in BOD5, COD, and
NFS than those flow-composite samples obtained with an ISCO Model
780. The corresponding percentages for the effluent samples were
104, 129, and 92.
A comparison of raw waste flow-proportional samples collected
over a five-day period with the Hants 3B and ISCO 1391 at Ashland,
Nebraska, also indicated a bias. The mean BOD5, COD, and NFS
concentrations of the Hants samples were 179, 183, and 334 percent
higher than the levels found in the ISCO samples. The corresponding
values for the effluent samples were 154, 146, and 220 percent,
respectively.
Raw waste samples collected concurrently with a QCEC-GVE,
Sirco MKV7S, and an ISCO sampler at the Kansas City, Kansas, Kaw
Point plant had mean NFS concentrations of 1,160, 720, and 582 mg/1,
respectively. These concentrations had the same relationship to
each other as did the liquid intake velocities of the samplers.
The comparison study at the Kaw Point plant using four differ-
ent manual sampling techniques and twelve different compositors did
not show any correlation between liquid intake velocity and param-
eter concentrations. This lack of correlation was felt to be due
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78
to a straining mechanism resulting from the high levels of sus-
pended solids in the waste. Because duplicate analysis for NFS
was run for this study, it was possible to isolate and estimate
data variability due to laboratory random analytical error and that
due to differences in compositor performance. Standard deviation
of laboratory error was ±101 mg/1 (coefficient of variation,
approximately 10 percent). The deviation due to sampler performance
ranged from ±92 to 271 mg/1 (coefficient of variation 9 to 24 per-
cent), depending upon whether or not the Brailsford EP-1 sample
data was included.
The comparison studies indicated that the high vacuum, high
liquid intake velocity samplers were more effective in capturing
solid material. Although these units also produced higher concen-
trations of BOD5 and COD, the increase in NFS was disproportionately
greater. It would appear that the slower-acting peristaltic and
piston pump type samplers are either not capturing settleable
materials or that after introduction to the intake line particle
settling velocities are higher than liquid intake velocities.
Another factor could be the agitation of sample increments during
collection. The greater intake velocities of those compositors
which have yielded high strength samples may be breaking up larger
size suspended material as the aliquot passes through the sampling
train and into the collection container. In the laboratory,
Tj
suspension of smaller sized particles would be more amendable to
extraction of representative amounts of residue with routine
pipetting procedures.
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79
2. ADDITIONAL PERFORMANCE STUDIES
The Richards-Gebaur study indicated extremely wide ranges in
apparent facility removal efficiencies as a function of grab sample
data which was manipulated to show effects of collection time,
sampling frequency and interval, and days of sampling. Additional
comparison studies using identical sampling equipment to collect
discrete, time-composite, and flow-composite samples would be use-
ful in developing more adequate grab sampling methodologies.
At this point the Field Investigations Section is of the
opinion that little more can be gained from field evaluation of
sampling equipment on the basis of sample representativeness.
Under field conditions, variables cannot be controlled, actual
concentrations of wastewater chemistry parameters are unknown, and
manual grab sampling is of questionable value as a "yardstick"
against which to measure the performance of automatic sampling
equipment.
The variability of NFS concentrations indicates that it is
especially difficult to obtain representative sample concentrations
of this parameter because of its sensitivity to changes in collec-
tion methodologies. Given the "state of the art" of currently
available compositors and ever-increasing varieties of equipment
coming on the market, there is an urgent need for development of a
synthetic suspended solids waste to evaluate samplers under con-
trolled laboratory conditions. A suitable synthetic waste: (a)
could be used as a performance specification in purchasing samplers,
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80
(b) could be used to determine the representativeness of samples
collected by various makes and models of compositors, (c) could
determine the suitability of specific equipment for particular
applications, (d) would be a step toward standardization of sam-
pling methods, (e) could result in reduced water chemistry varia-
bility, and (f) would increase data credibility for enforcement
activities.
Development of a synthetic solids waste to be used in con-
junction with laboratory evaluation of sampler performance would
require consideration of the following variables: (a) particle
size and specific gravity, (b) sampler liquid intake velocity, (c)
intake tube diameter, (d) orientation of intake line with respect
to waste stream velocity vectors, and (e) liquid temperature and
viscosity.
3. SELECTION OF SAMPLING EQUIPMENT
Although the results of the sampler comparison studies are not
conclusive and additional work is needed, it is the opinion of the
Field Investigations Section that high-vacuum, sampling equipment
produces more representative samples. On waste sources with
appreciable concentrations of large and/or heavy settleable material
such as a raw municipal wastewater, the section makes every effort
to install a high vacuum unit when compatible with site conditions
and data requirements. Since these units yield higher results,
they are of advantage to treatment plants in determination of
removal efficiencies.
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81
Variations in compositor performance at effluent sampling
stations were found to be smaller due to water chemistry equaliza-
tion resulting from plant retention times and, it is felt, to the
lower levels of suspended material which are smaller, more uniform,
and of lower density than the particles found in raw waste.
Although high-vacuum samplers can be effectively used on these
wastes, the data would indicate that well-treated effluents with
no visible solids can be representatively sampled with the slower
acting compositors.
4. FLOW PROPORTIONAL SAMPLING
With present sampling technology, the section feels that flow
compositing of raw municipal wastewaters and other wastes with
appreciable settleable solids is neither necessary nor justified.
The variations in sampler performance and manual sampling techniques
completely mask actual changes in wastewater chemistry character-
istics. At best, variations traceable to differences in compositor
performance ranged from ±9 to 24 percent. In some instances
differences in NFS levels were over 300 percent. Data discrepancies
of this magnitude do not warrant the extra time and expense involved
in installing sophisticated sampling equipment and flow measurement
devices.
The comparison studies on treated wastes would indicate that
well-treated, sparkling effluent with no visible solids are
amenable to flow-proportional sampling and that a suitable composi-
tor can be selected without regard to variations in performance.
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82
This would also apply to industrial wastes which were all in solu-
tion form.
Because of work load, the need for expediency, and the limited
scope of most surveys the section generally does not collect flow-
proportional samples. Approximately 5 percent of the sampling
stations the section surveys have weirs or flumes equipped with
flow totalizers which are in proper working order suitable for
manual compositing of flow-proportional samples. Most of these
totalizers are located at the facility influent. About 40 percent
of the stations have only a weir or flume and 50 percent have no
measurement device of any sort. It is extremely rare to find a
facility with suitable flow-measurement devices on both influent
and effluent stations.
Most of the flow-proportional sampling efforts of the section
are confined to data gathering for enforcement activities, in-depth
evaluations of new and existing treatment facilities, and investi-
gations of industrial processes where mass balances are of critical
importance.
It should also be pointed out that manual flow compositing of
discrete grab samples, whether collected with an automatic sampler
or manually, introduces another possible source of error and
requires more time of the professional in the field. Sources of
error would include: (a) not shaking the discrete sample prior to
compositing5 (b) miscalculation of correct sample volumes as a
result of having to use a slide rule or electronic calculator to
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83
determine discharge rates from exponential functions based on head
measurements, and (c) misreading of graduated cylinders. It would
appear that those automatic collection devices which collect flow-
proportional aliquots and composite them in a single container
would be most effective in eliminating this source of error.
5. SAMPLING METHODOLOGY
Data from grab samples collected during the comparison studies
showed wide fluctuations in wastewater strength over a 24-hr period.
The Richards-Gebaur study resulted in NFS coefficients of variation
which ranged from 44 to 60 percent on the raw waste, 30 to 41 per-
cent on the primary effluent, and 15 to 32 percent on the final
effluent. Based upon collection of one grab sampler per day for
three days, it was shown that the apparent solids removal effi-
ciency of the Richards-Gebaur facility ranged from -103 to +70
percent depending upon sample collection time. Comparing six grab
samples per day with 24-hr manual flow composites for one, two,
and three days, it was shown that mean grab sample efficiencies
differed from the mean manual composite efficiencies by 10, 3, and
5 percent, respectively.
The raw grab sample data from the Kansas City, Kansas, Kaw
Point sewage treatment plant investigation of April 15 to.18, 1973,
resulted in a COD standard deviation of ±545 mg/1 and a coefficient
of variation of 30 percent. Removal efficiencies of this facility
calculated on the basis of two grab samples were in some instances
only a third of the efficiencies obtained with composite sample
data.
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84
These variations emphasize the importance of an adequate
sampling program and appropriate equipment. A poll of EPA, Surveil-
lance and Analysis staff members around the country resulted in a
general concurrence that for normally variable domestic wastewaters
a minimum of 8 evenly-spaced grab samples collected over a 24-hr
period, repeated for a minimum of 3 wk days, will result in a fair
estimate of water chemistry characteristics.
It is the opinion of the Field Investigations Section that
either time or flow-proportional sampling should be used in routine
surveys and monitoring of municipal treatment plants unless those
variations which occur throughout the day are of interest. Analy-
ses of an adequate number of discrete grab samples to characterize
wastewaters and plant efficiencies is an inordinate drain of labo-
ratory resources and is not economically justified. The use of
automatic compositors can easily be offset by savings in analyses
costs.
The section confines most of its grab sampling efforts to
special studies and enforcement activities. Because of the strict
chain of custody procedures which can be exercised with manually
collected grab samples, they are often used to support those data
resulting from use of unattended compositors.
Considerable judgement is required for industrial wastewater
flows which vary widely in composition and volume throughout the
work day. Initial surveys of industrial wastewaters should be
carried out only after a thorough understanding of plant processes.
Surveys should include 24-hr-a-day composite sampling for a period
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85
of 5 days, including the normal second shift Friday cleanup period.
For max information of wastewater quality and variability, it is
frequently a good idea to install two compositors - one with dis-
crete sample jars and on an hr cycle to provide for a flow propor-
tional composite and also individual hourly samples for analysis.
A second compositor taking small aliquots at more frequent intervals
(10 to 15 min) can be used to obtain a second composite sample
which should contain portions of all of the batch discharges of
short duration. Comparison of analyses from the two composites
should give a good indication of whether or not sampling at a 1-hr
frequency is adequate. There are several varieties of discrete
bottle compositors now on the market with a multiplex capability
which provides for frequent samples to be composited in each of the
hourly sample jars negating the need for a second sampler.
6. THE IDEAL AUTOMATIC SAMPLER
Manufacturers of samplers have yet to produce a unit which
will meet all the sampling requirements and the physical site
conditions encountered by the Field Investigations Section.
Development of such a unit would greatly simplify the logistical
problems of providing an adequate stock of spare replacement parts
and would save that time now spent in becoming familiar with the
operation and repair of a large variety of samplers.
As a result of field experience and sampler performance com-
parison studies, the section has developed a list of the features
which the "ideal" sampler would incorporate.
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86
1. Capability for AC/DC operation with adequate dry
battery energy storage for 120-hr operation at
1-hr sampling intervals.
2. Suitable for suspension in a standard manhole and
still provide access for inspection and sample
removal.
3. Total weight including batteries under 18 kg
(40 Ib).
4. Sample collection interval adjustable from 10
min to 4 hr.
5. Capability for flow-proportional and time-composite
samples.
6. Capable of collecting a single 9.5-1 (2.5-gal)
sample and/or collecting 500-ml (0.13-gal) discrete
samples in a minimum of 24 containers.
7. Capability for multiplexing repeated aliquots into
discrete bottles.
8. One intake hose with a minimum ID of 0.64 cm (0.25
in.) and a weighted streamlined intake screen which
will prevent accumulation of solids.
9. Intake hose liquid velocity adjustable from 0.61
to 3 m/sec (2.0 to 10 fps) with dial setting.
10. Minimum lift of 6.1 m (20 ft).
11. Explosion proof.
12. Watertight exterior case to protect components in
the event of rain or submersion.
13. Exterior case capable of being locked and with lugs
for attaching steel cable to prevent tampering and
provide some security.
14. No metal parts in contact with waste source or
samples.
15. An integral sample container compartment capable
of maintaining samples at 4 to 6°C for a period of
24 hr at ambient temperatures up to 38°C.
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87
16. With the exception of the intake hose, capable of
operating in a temperature range between -10 to
40°C.
17. Purge cycle before and after each collection inter-
val and sensing mechanism to purge in event of
plugging during sample collection and then collect
complete sample.
18. Capable of being repaired in the field.
7. THE PROFESSIONAL IN THE FIELD
The data has shown many sources of data variability and
emphasizes the importance of having a professional in the field to
select sampling locations, equipment, and methodology. It is
obvious that those individuals responsible for surveys and sample
collection activities can use any of the generally accepted sam-
pling techniques and equipment and still intentionally or uninten-
tionally manipulate apparent wastewater chemistry characteristics
and facility removal efficiencies.
The practice of using low-paid, unsupervised personnel to
collect samples for analysis by highly-paid professional chemists
ts a misappropriation of technical and economic resources which
can only result in unrepresentative data.
It is little wonder that there are so many disagreements among
various responsible Federal, state, city, and individual groups
regarding water chemistry characteristics and facility performance.
When variations in sampling methodology and laboratory systematic
and random errors are further compounded by errors in flow
measurements, differences can become astronomical. Without an
adequate monitoring program and tight controls on sampling
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88
techniques, equipment, and laboratory procedures, data interpreta-
tion can be reduced to little more than an exercise in futility.
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89
V. HYDRAULIC MEASUREMENTS
Calculation of loadings, effluent limitation quantities, and
flow-proportional sampling require hydraulic measurements. The
need for accurate rate measurements is just as great, if not
greater than the need for good representative water chemistry data.
Ideally, the professional in the field surveying a wastewater system
strives to develop a materials mass balance using the combination
of flow rate and parameter concentration. Because of biological
activity, errors in flow measurements, sampling methods, and labo-
ratory analytical random errors, a mass balance is seldom achieved
in practice.
Because of the variety of sampling station configurations
encountered and the essentially empirical nature of most measurement
techniques, flow rate accuracy remains as one of the weakest aspects
of the field survey.
The Field Investigations Section has no special expertise in
the area of hydraulics and a detailed discussion of the subject is
beyond the scope of this report and would be presumptuous and redun-
dant in light of the number of excellent references (4, 5, 6, 7, 8,
9) available. Personnel responsible for flow measurement data
would be well advised to obtain and study the first four of these
references, particularly (4) which discusses most of those methods
likely to be of use in the field.
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90
This chapter reports these methods and equipment which the
Field Investigations Section has used in its surveys and indicates
those factors which can result in significant error.
A. WEIRS, FLUMES, AND RECORDING EQUIPMENT
1. WEIRS
Approximately 50 percent of those sampling stations surveyed
by the section have no flow measurement device of any sort and it
is frequently necessary for the section to make temporary installa-
tions of equipment. Weirs can be placed relatively quickly and are
generally used at those sites requiring discharge measurements.
Weirs commonly installed by section personnel or encountered
at wastewater treatment facilities have included: (a) 90° V-notch,
(b) 60° V-notch, (c} contracted rectangular, (d) suppressed rec-
tangular, and (e) Cipolletti. The following necessary conditions
are reported (4, p. 12-13) for setting weirs and getting accurate
discharge rate measurements:
a. The upstream face of the bulkhead should be smooth
and in a vertical plane perpendicular to the axis
of the channel.
b. The upstream face of the weir plate should be smooth,
straight, and flush with the upstream face of the
bulkhead.
c. The entire crest should be a level, plane surface
which forms a sharp, right-angled edge where it
intersects the upstream face. The thickness of
the crest, measured in the direction of flow, should
be between 1 to 2 mm (0.03 to 0.08 in.). Both side
edges of rectangular weirs should be truly vertical
and of the same thickness as the crest.
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91
d. The upstream corners of the notch must be sharp.
They should be machined or filed perpendicular to
the upstream face, free of burrs or scratches, and
not smoothed off with abrasive cloth or paper. Knife
edges should be avoided because they are difficult
to maintain.
e. The downstream edges of the notch should be relieved
by chamfering if the plate is thicker than the
prescribed crest width. This chamfer should be at
an angle of 45 deg or more to the surface of the
crest.
f. The distance of the crest from the bottom of the
approach channel (weir pool) should preferably be
not less than twice the depth of water above the
crest and in no case less than 0.305 m (1 ft).
g. The distance from the sides of the weir to the sides
of the approach channel should preferably be no less
than twice the depth of water above the crest and
never less than 0.305 m (1 ft).
h. The overflow sheet (nappe) should touch only the
upstream edges of the crest and sides.
i. Air should circulate freely both under and on the
sides of the nappe.
j. The measurement of head on the weir should be taken
as the difference in elevation between the crest and
the water surface at a point upstream from the weir
a distance of four times the max head on the crest.
k. The cross-sectional area of the approach channel
should be at least eight times that of the overflow
sheet at the crest for a distance upstream from
fifteen to twenty times the depth of the sheet.
It is probably safe to say that the Field Investigations
Section has never encountered a weir installation which met all of
the preceding requirements. Weir crests are not chamfered, are
covered with debris and biological growth, are not flush with
bulkhead plates, and are too close to bottom and sides of approach
channel. Velocities of approach (Va) are too high as a result of
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the weir pool being underdesigned to start with or as a result of
deposition of solids. A Va between 0.305 and 0.61 m/sec (1 to 2
fps) can result in a discharge rate error ranging from -10 to -35
percent. If weir pool Va are significant, they should be measured
with a current meter* or estimated with floats (if nothing else is
available) and corrected for (4, p. 25-26).
Some observed weir deficiencies can be corrected; however,
from a practical standpoint a loss of accuracy must be expected as
it is seldom feasible to optimize all installation requirements.
Even at those locations at which the section installs equipment,
site conditions such as limited space, hydraulic head, and concrete
abutment structures impose investigative restraints which are a
compromise between time, economics, and data requirements.
2. FLUMES
The Parshall flume is one of the most common types of flow
measurement devices installed at wastewater treatment facilities
and is preferred because: (a) it can operate with relatively small
losses of head, (b) it is relatively insensitive to velocity of
approach, (c) if properly installed, it will give good measurements
over a wide range of downstream submergence, and (d) flow velocities
are sufficiently high to eliminate solids deposition.
Because of the time required to properly install these devices,
the section has not set Parshall flumes at any survey sites and
* See Page 102
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93
experience has been confined to those flumes encountered at waste-
water treatment facilities.
Prior to taking water measurement data, a Parshall flume should
be checked to see that: (a) longitudinal and lateral axes of crest
floor are level, (b) side walls are parallel and throat dimensions
close to design tolerances, (c) approach flows are uniformly dis-
tributed in the upstream convergence section, (d) head measurement
devices (if installed) at correct location, and (e) flow variations
are within the range for which the flume is accurate.
3. FLOW RECORDING EQUIPMENT
a. FACILITY RECORDERS
About 25 percent of those facilities which have weirs or flumes
also have continuous flow recording equipment. Approximately half
of these installations have recorders which are in proper working
order.
Sources of measurement error with recording equipment are
common to both weirs and flumes and include:
(1) Stilling well in wrong location with respect to
weir or flume crest.
(2} Trash and debris in stilling well and conduit
between flume and well plugged.
(3) Float dirty, punctured, not vertical, and rubbing
against side of stilling well. Slack in float
cable.
(4) Wrong recorder multiplier and chart paper. Pen not
inked and not giving responsive trace. Recorder
does not zero. An error in calibration of 1.5 cm
(0.60 in.) can cause an error in rate measurement
ranging to several hundred percent at low depths
on small weirs and twenty to thirty percent for
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94
moderate depths in flumes with throat widths under
30.5 cm (12 in.).
Prior to using flow data from plant recorders, the instrumen-
tation should be manually checked by taking an instantaneous head
measurement with a staff gage or rule, calculating a discharge
rate, and checking this rate against the recorder.
b. PORTABLE RECORDERS
(1) BELFORT LIQUID LEVEL RECORDER
The section has three Bel fort Portable Liquid Level Recorders*
which have been in use for four or five yr. These recorders are
relatively rugged and extremely reliable when properly installed.
X
The units have many positive features which include the following:
(a) Fairly inexpensive at approximately $320 each.
(b) Accurate and easily read head measurements over a
limitless range of water levels because the pin
traverses up and down over the full width of the
chart as water levels rise or fall.
(c) Optional recording times available from six hours
to eight days per chart revolution.
(d) Mechanism is mechanically'simple and in most cases
can be repaired in the field.
The primary disadvantage of the Bel fort Recorder is related to
installation. The unit requires a stilling well for a float and
must be mounted level. One can easily spend an entire day in con-
struction and installation of stilling well and mounting platform
and calibration of recorder. The min diam of the stilling well
?i
(dependent upon float) is about 10 cm (4 in.). This well offers an
* No 5-FW-l, Belfort Instrument Company, 1600 South Clinton
Street, Baltimore, Maryland 21224
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95
obstruction to flow and, consequently, the unit cannot be used for
small channels or in high velocity channels carrying large amounts
of debris. The instrument is almost impossible to install in man-
holes.
(2) MANNING DIPPER RECORDER
The Manning Dipper Recorder* senses and records water levels
by means of a weighted electrical probe on the end of a thin metal
eable which extends from the bottom of the recorder. The probe
follows the surface of the water and merely swings aside when hit
by debris.
The primary advantages of this instrument are an adaptability
to an almost limitless variety of site configurations and its ease
of installation. At most locations the unit can be installed and
calibrated in fi-fteen to twenty min. The adjustable bracket
included with the unit makes it particularly suited for manhole
installations where it can be installed up to 7.6 m** (25 ft) above
the water surface. Since the unit operates on a 6-v battery***,
manhole installation provides good equipment security as all com-
ponents are below street grade and manhole covers are replaced.
The disadvantages of this unit include: (a) cost, units are
about $835 each, (b) limited recorder range with respect to changes
in water level, (c) accuracy, recorder chart cannot be read
* Model P70015, Manning Environmental Corporation, 112 Dakota
Street, Santa Cruz, California 95060
** Longer cables are available
*** Eveready Hot Shot #1461, Ray-0-Vac #641, or equivalent
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96
closer than 1.27 cm (0.5 in.), and (d) units are fairly sophisti-
cated electronically and generally cannot be repaired in the field.
c. DISCHARGE CALCULATIONS
It should be pointed out that many portable recorders, includ-
ing the Bel fort and Manning units discussed previously, record
water level only and do not have an internal integrating mechanism
for totalizing flows. With Parshall flumes and most weirs flow
rate is a nonlinear function of head and must either be determined
from published tabulations (4) or calculated with the different
exponential formulas reported for various flumes and weirs. Since
many tabulations do not cover every variety of flow measurement
device, it is frequently necessary to make these calculations in the
field when flow proportioning samples. Although any good slide
rule is suitable for these calculations, they are slow, introduce a
greater probability of error, and are definitely not "technician
proof." To reduce time and increase accuracy, it is recommended
that the individual have a portable electronic calculator* with an
exponential function key as part of his field equipment.
B. WET WELL VOLUME DISPLACEMENT
Wastewaters are often collected in a wet well prior to intro-
duction to a treatment system. In the absence of flow measurement
devices, these wells can be used to obtain rate measurements by
* Hewlett Packard Model HP-35 or 45, Texas Instruments Model SR-50,,
Sharp PC-1801, or equivalent
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using the cross-sectional area of the well and the frequency of
"pump down" which can be established with the Bel fort or Manning
units.
C. FLOW RATES IN PIPES
1. VOLUMETRIC MEASUREMENT
On small discharges, the section frequently uses a container
of known capacity and a stopwatch to determine instantaneous flow
rates. With the plastic sampling buckets normally used by the
section, discharge rates are limited to a maximum of about 76 1/min
(20 gpm).
2. PIPE WEIRS
The section has three sets of V-notch weirs*, designed for
pipe installation, which were purchased at a cost of approximately
$350 each. The weir is of a clear plastic material calibrated in
gpd and is mounted in a semicircular aluminum frame which has a
rubber gasket around the outside to insure a good pipe fit. Proper
installation of the weir is aided by a bubble level attached to the
frame. The weirs are held in place by extended rods which are
slipped into a screw thread and socket and forced up against the
crown of the pipe.
Maximum weir flow rates with 15.2-, 20.3-, 25.4-, 30.5-, and
38.1-cm (6-, 8-, 10-, 12-, and 15-in.) diam pipes are 143; 244; 586;
1,071; and 2,951 cu m/day (10,000; 17,000; 40,900; 74,750; and
* N. B. Products, 35 Beulah Road, New Britain, Pa.
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206,000 gpd), respectively. The set also has six adaptor plates
which the weirs can be set into in order to fit them to larger size
pipes. These adaptor plates do not increase the weir capacities.
Although these weirs provide a quick method for getting
instantaneous flow rates, the likelihood of error is appreciable
since variations in approach velocities cannot be corrected for.
In addition, max weir capacities are much lower than max pipe
capacities since the weir and frame obstruct a significant part of
the cross-sectional area of the pipe.
3. TRAJECTORY METHODS
a. CALIFORNIA PIPE METHOD
The "Water Measurement Manual" states four essential require-
ments for this method: (1) discharge pipe must be level, (2) it
must discharge partially full, (3) it must discharge freely into
air, and (4) the velocity of approach must be a min. Discharge
rates are computed from the formula:
Q=8.69 (1 - ajl.88d2.48
where: Q = discharge rate, cfs
a = distance measured in the plane at the
end of the pipe, from the top of the
inside surface of the pipe to the water
surface, ft
d = internal diam of the pipe, ft
This formula was developed from experimental data for pipes
7.62 to 25.4 cm (3 to TO in.) in diam and tests have shown that the
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formula does not hold up at an a/d ratio of less than 0.5 (4, p.
197). This formula should not be used with corrugated metal pipes.
b. PURDUE METHOD
This is a more general form of the trajectory method which can
.be used with pipes flowing full and with high velocities. Basically
the method consists of measuring the horizontal (X) and vertical (Y)
coordinates of the path of a jet of water issuing 'from a level pipe.
The reader is referred to the "Water Measurement Manual" (4, p. 200-
203) for a description of this method and for graphs showing dis-
charge rates of different size pipes as a function of the X and Y
coordinates.
4. ORIFICE BUCKET
As of this writing, the Field Investigations Section has no
experience with the orifice bucket and is presently evaluating the
device in the laboratory. Basically the unit is nothing more than
a sturdy 18.9-1 (5-gal) or larger can with a number of rubber stop-
pered holes in the bottom and with a graduated piezometer tube on
the outside for reading water levels. A screen or dispersion
device of some sort should be mounted in the bucket to reduce
direct velocity impingement on the orifices. Prior to field use
the device must be calibrated in the laboratory by removing one of
the rubber stoppers and determining the flow rate through the
orifice at different constant heads with a known, variable water
source. From the laboratory data a rating curve is developed for
the bucket showing gpm versus head for one orifice. If hole size
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100
tolerances are carefully controlled, it is not necessary to develop
a rating curve for two or more orifices open, as flow rate through
each orifice will be the same and equal to that rate determined for
one orifice. Consequently, in the field larger discharge rates are
determined by multiplying the rate for one hole by the number of
holes open. Since it is necessary to have a constant head in the
bucket, this device is obviously not suitable for those discharges
with rapid fluctuations in volume. Additional information can be
found in (10, p. 30) and (11).
5. MANNING FORMULA
Discharge rates can also be calculated by determining the
cross-sectional area of the flow and the average velocity in the
cross section. With circular conduits the section frequently uses
the Manning formula to estimate velocity.
V = 1-486 r2/3sl/2
n
where: V = average velocity, fps
r = hydraulic radius, a/p
a = area of cross section of stream, sq ft
p = wetted perimeter of pipe, ft
s = slope, ft per 100 ft
n = roughness factor
The roughn&ss factors for various pipe materials can be found
in hydraulic reference and text books (12, 13).
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Flow rates for pipes 0.152 to 1.22 m (6 to 48 in.) in diam at
various depths of flow and slopes are available in tabulated form
(6) and are relatively inexpensive.
In the field, section personnel use a carpenters square with
an attached, pocket-size, inclinometer* to measure pipe slopes. If
one is working at the open end of a pipe, the depth of flow should
be measured as far up in the pipe as possible, otherwise errors due
to drawdown will be introduced into the discharge calculation. If
one is interested in a number of measurements and is not certain
about a roughness factor (n), it is frequently possible to gage
pipe discharges at a downstream point in an open channel and then
solve.the Manning Formula for n.
6. FLOWMETER
The section has also used a number of different velocity
meters to determine pipe flow rates. One such meter is a digital
flow** device with a built-in counter that counts the revolutions
of a propeller. Velocities are determined from a rating, curve
supplied with the instrument. This is a rugged instrument which is
not sensitive to low velocities and is, therefore, best suited to
those high velocity flows which might damage other types of meters.
At times the section has also used Price type current meters
to determine pipe velocities. These meters should be used with
t
* Keuffel and Esser Company, New York
** Digital Flowmeter, Model 2030, General Oceanics, Inc., 5535
Northwest Seventh Avenue, Miami, Florida 33127
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caution since they are quite sensitive and subject to damage in
high velocity, turbulent flows.
D. OPEN CHANNEL FLOW
1. STREAM GAGING
In its field activities, the section also does a significant
amount of stream gaging at locations where receiving water quality
is of interest. Basic items of equipment required for stream
gaging include: (a) current meter, (b) wading rod, (c) sound box
or earphones to indicate meter revolutions, (d) stopwatch, (e) tag
line, and (f) small clipboard and discharge measurement forms.
Meters, wading rods, earphones, and tag lines are available from a
number of suppliers*. It is recommended that one purchase equip-
ment from a single manufacturer, as components are not always
interchangeable. The discharge measurement forms** used by the
section are printed on a rubberized paper and are supplied by the
General Services Administration (Form No. 7-EPA-5300-1).
As of this writing, the section has relied upon the Price type
current meter (both standard and pygmy) for stream gaging. In the
near future, the section will also have the Ott meter available.
The Ott meter is of advantage in some situations where vertical
velocity gradients are a problem.
* Weather Measure Corporation, P. 0. Box 41257, Sacramento,
California 95841 - Kahlsico Scientific Corporation, P. 0. Box
1166, El Cajon, California 92022 - EPIC, Inc., 150 Nassau
Street, New' York, New York 10038
** The Field Investigations Section will furnish one copy of this
form for examination or duplication
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Both of these meters are precision instruments and should be
treated accordingly. The Price type meters are especially sensitive
to worn pivots and errors in velocity measurement of 20 percent of
flow under 0.15 m/sec (0.5 fps) are common with worn pivots, bent
cups, and solids under the cup and bushing. When using a current
meter with a questionable pivot pin or old rating, It is better to
look for a site with velocities of about 0.30 m/sec (1 fps) or
better as errors due to inertia of the meter will be minimized.
Regular oils should not be used on these meters during winter
weather as the increase in viscosity can seriously affect the
accuracy of rate measurement. The silicone type lubricants are
not affected by changes in temperature.
Although there are a number of types of wading rods available,
the section uses.the USGS type top-setting rod. These rods are
made under contract for the USGS and sources change from year to
year. Within the Region, current information on these rods would
be available from the USGS Water Resources Division, Roll a,
Missouri. It is understood that this division must endorse orders
for this rod.
The section has received some requests for information con-
cerning meter calibration. Manufacturers no longer supply current
meters which have been calibrated by the National Bureau of
Standards and the section relies upon those rating tables furnished
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with each meter. If desired, the bureau* will calibrate meters.
In 1972 the cost for calibration to government and private agencies
was $116 per meter.
2. ELECTROMAGNETIC WATER CURRENT METER
The section has one of these units** which has received rather
limited use in the past two yr. This is a battery-operated, port-
able instrument which gives a direct meter readout in fps of X and
Y velocity components. The velocity sensing probe is all magnetic,
has no moving parts and is an integral part of a 1.3-cm (0.5-in.)
diam cable leading from the meter. This cable, with attached probe,
can be purchased in desired lengths. The meter has a recorder
output terminal.
This unit has been used, primarily, in pipes with high velocity
discharges and in small open channels. Although the unit is port-
able, it is rather heavy and not suited to a one-man operation for
gaging streams. Since velocity readout is affected by probe orien-
tation, the probe must either be held by hand or fixed on a rigid
rod when taking measurements. The price ($2,500) and complexity of
this unit prohibits rough handling or any service in the field.
A trial run of this instrument (see Section E) when it was
first received resulted in meter fluctuations of 0.5 fps at a full
* (Correspondence Only) National Bureau of Standards, Hydraulics
Section, Washington, D.C. 20234 - (Meters should be sent to)
National Bureau of Standards, Hydraulics Section, Route 705,
Quincy Orchard Road, Gaithersburg, Md. 20760
** Model 721, Marsh-McBirney, Inc., 10453 Metropolitan Avenue,
Kensington, Md. 20795
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scale setting of 1 fps while being held at a single position in a
flowing stream. As a result of this, the meter was returned to the
factory and an alternate 5-sec "time constant" was added to dampen
out meter fluctuations. With this addition the instrument has a
toggle switch to select the standard, 1-sec time constant* or
alternate 5-sec constant. This addition has greatly increased the
usefulness of the instrument.
E. PRECISION OF THREE MEASUREMENT METHODS
Soon after the section received the Marsh-McBirney current
meter (MMCM) a water course was sought in which it could be com-
pared with the Price type pygmy current meter (PPM). As a result
of a previous investigation, the weir pool upstream of a 61-cm
(24-in.), sharp-crested, contracted, rectangular weir** was selected.
With this discharge it was possible to get three independent flow
rates simultaneously. , These three rates were: (1) the rated weir
discharge, (2) the rate resulting from MMCM velocity readings and
the weir pool cross-sectional area (plane parallel to weir bulk-
head), and (3) the rate resulting from the PPM velocity readings
and the pool cross-sectional area.
The cross section selected was about 2.13 m (7 ft) upstream
from the weir bulkhead, had formed vertical sides 1.83 m (6 ft)
apart, and was relatively uniform in depth. The arithmetic mean
* After positioning probe, user must wait three times the time
constant before recording a velocity reading
** Midwest Solvents Company discharge in Atchison, Kansas
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depth (25 measurements) was 30.7 cm (12.1 in.) with max and min
depths being 35.6 cm (14.0 in.) and 26.7 cm (10.5 in.), respectively.
Traversing of the cross section began at 1115 hr and ended at
1535 hr June 3, 1972. Using both the MMCM and PPM, which were
mounted on essentially identical wading rods, velocity measurements
were made at 7.6-cm (0.25-ft) intervals across the section at
depths of 6.1, 12.2, 18.3, and 24.4 cm (0.2, 0.4, 0.6 and 0.8 ft).
The weir head during the cross sectioning ranged from 18.9 cm
(0.62 ft) to 20.4 cm (0.67 ft) and the mean head (8 readings) was
19.8 cm (0.65 ft).
Table XIX shows the flow data resulting from cross sectioning
with each of the two meters. The weir discharge rate and a summa-
tion of the incremental flow rates resulting from each meter were
as follows:
I/sec cfs
Weir 93.2 3.29
Price Pygmy Meter (PPM) 117.2 4.14
Electromagnetic Current
Meter (MMCM) 98.8 3.49
Mean 103.1 3.64 ±(10 to 14 percent)
These data would indicate that under ideal circumstances the
section cannot determine flow rates any closer than ±10 percent.
It should be pointed out that in routine surveys the section would
never take 96 velocity readings in a 1.83-m (6-ft) cross section
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TABLE XIX
SUMMARY OF FLOW DATA OBTAINED USING A PRICE TYPE PYGMY METER (PPM)
AND A MARSH MCBIRNEY CURRENT METER (MMCM)
Distance From
Initial Point, ftw
Depth, ft(a)
Area, ftz(b)
Depth From Water
Surface Of Velocity
Measurement, ftva)
0.2
0.4
0.6
0.8
Mean
Discharge, cfs(c)
Velocity Ratio PPM/MMCM
0.00
1.08
0.27
0.25
1.08
0.27
0.50
1.12
0.28
0.75
1.08
0.27
1.00
1.17
0.29
1.25
1.08
0.27
Velocity, fps
PPM
0.00
0.00
0.00
0.00
0.00
0.00
MMCM
0.0
0.0
0.0
0.0
0.0
0.0
-
PPM
0.08
0.04
0.07
0.05
0.06
0.016
MMCM
0.0
0.0
0.0
0.0
0.0
0.0
-
PPM
0.06
0.06
0.02
0.04
0.05
0.014
MMCM
0.0
0.0
0.0
0.0
0.0
0.0
-
PPM
0.23
0.09
0.03
0.02
0.09
0.024
MMCM
0.20
0.00
0.00
0.00
0.05
0.014
2.0
PPM
0.17
0.12
0.07
0.03
0.10
0.029
MMCM
0.15
0.05
0.00
0.05
0.04
0.014
2.0
PPM
0.45
0.20
0.06
0.24
0.24
0.065
MMCM
0.20
0.30
0.00
0.00
0.13
0.027
2.5
Distance From , >
Initial Point, ftw
Depth, ft(a)
Area, ftz(b)
Depth From Water
Surface Of Velocity
Measurement, ft(a/
0.2
0.4
0.6
0.8
Mean
Discharge, cfs'c'
Velocity Ratio PPM/MMCM
1.50
1.08
0.27
1.75
1.08
0.27
2.00
1.00
0.25
2.25
1.00
0.25
2.50
1.00
0.25
2.75
1.00
0.25
Velocity, fps
PPM
0.56
0.43
0.22
0.09
0.32
0.086
MMCM
0.20
0.40
0.40
0.40
0.35
0.094
0.90
PPM
0.74
0.86
0.42
0.16
0.54
0.146
MMCM
0.60
0.60
0.50
0.15
0.45
0.122
1.20
PPM
0.96
1.11
0.80
0.38
0.81
0.202
MMCM
0.70
0.70
0.60
0.20
0.55
0.137
1.50
PPM
1.21
1.25
1.05
0.57
1.02
0.255
MMCM
0.75
0.85
0.85
0/65
0.80
0.200
1.30
PPM
1.37
1.24
1.09
0.80
1.12
0.280
MMCM
1.00
1.05
0.80
0.65
0.90
0.225
1.25
PPM
1.42
1.28
1.11
0.75
1.14
0.285
MMCM
1.00
1.10
0.90
0.80
0.95
0.237
1.20
(a) Multiply by 0.3048 to obtain m
(b) Multiply by 0.0929 to obtain sq m
(c) Multiply by 1.7 to obtain cu m/min
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108
TABLE XIX (CONTINUED)
SUMMARY OF FLOW DATA OBTAINED USING A PRICE TYPE PYGMY METER (PPM)
AND A MARSH MCBIRNEY CURRENT METER (MMCM)
Distance From , .
Initial Point, ft*8'
Depth, ft^
Area, ft2(b)
Depth From Water
Surface Of Velocity
Measurement, ft(a)
0.2
0.4
0.6
0.8
Mean
Discharge, cfs(c)
Velocity Ratio PPM/MMCU
3.00
1.00
0.25
3.25
0.96
0.24
3.50
0.96
0.24
3.75
0.96
0.24
4.00
0.96
0.24
4.25
0.92
0.23
Velocity, fps
PPM
1.39
1.24
1.08
0.77
1.12
0.280
MMCM
1.15
1.05
0.90
0.65
0.95
0.238
1.20
PPM
1.33
1.20
1.00
0.67
1.05
0.252
MMCM
1.15
1.05
0.80
0.65
0.90
0.216
1.15
PPM
1.30
1.14
0.86
0.28
0.90
0.216
MMCM
1.20
1.05
0.90
0.50
0.90
0.216
1.00
PPM
1.38
1.25
1.06
0.60
1.07
0.257
MMCM
1 .15
1.05
0,80
0.50
0.85
0.204
1.25
PPM
1 .35
1.22
0.96
0.38
0.98
0.235
MMCM
1.20
1.05
0.90
0.15
0.80
0.192
1.20
PPM
1.38
1.22
1.00
0.20
0.95
0.218
MMCM
1 .25
1.15
1.00
0.30
0.90
0.207
1.05
Distance From . .
Initial Point, ft^a'
Depth, ft(fl)
Area, ft2(b)
Depth From Water
Surface Of Velocity
Measurement, ft(a)
0.2
0.4
0.6
0.8
Mean
Discharge, cfs^c'
Velocity Ratio PPM/MMCM
4.50
0.92
0.23
4.75
0.92
0.23
5.00
0.92
0.23
5.25
0.92
0.23
5.50
0.88
0.22
5.75
0.88
0.22
Velocity, fps
PPM
1.38
1.21
1.01
0.62
1.05
0.242
MMCM
1.25
1.10
0.95
0.80
1.00
0.230
1.05
PPM
1.37
1.29
1.07
0.65
1.09
0.251
MMCM
1.35
1.15
0.95
0.50
1.00
0.230
1.10
PPM
1.38
1.30
1.23
0.84
1.17
0.274
MMCM
1.30
1.20
1.00
0.80
1.10
0.253
1.10
PPM
1.12
1.04
1.29
0.81
1.07
0.246
MMCM
1.00
0.80
0.90
0.55
0.80
0.184
1.35
PPM
0.66
0.76
0.80
0.46
0.67
0.147
MMCM
0.70
0.65
0.75
0.50
0.65
0.143
1.05
PPM
0.57
0.74
0.65
0.26
0.56
0.123
MMCM
0.60
0.60
0.45
0.25
0.50
0.110
1.10
(a) Multiply by 0.3048 to obtain m
(b) Multiply by 0.0929rlo obtain sq m
(c) Multiply by 1.7 to obtain cu m/min
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109
that was only 30.7 cm (12.1 in.) deep. In routine work a max of
twelve measurements would have been taken. General flow measurement
precision in routine surveys is probably on the order of ±20 or 25
percent.
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no
VI. CONCLUSIONS
As a result of experience, sampler comparison studies, and
accumulated survey information, the Field Investigations Section
has reached the following conclusions:
1. Overall failure rate of commercially available
samplers is approximately 16 percent.
2. Major cause of sampler malfunction is due to
plugging of intake lines.
3. Operational reliability of commercially available
samplers varies significantly and application is a
major factor in selecting appropriate equipment.
4. Variations in nonfilterable solids concentrations
of raw waste samples as a result of differences in
sampling equipment or collection method are at
least 9 to 24 percent.
5. Currently available sampling equipment cannot be
relied upon to produce representative samples.
6. High vacuum samplers produce more representative
samples and should be used on raw municipal waste-
waters and other wastes with significant levels of
large heavy suspended material.
7. Any sampler compatible with site conditions and
data requirements can be used to sample well-
treated effluents with no visible solids.
8. Flow-proportional sampling of raw municipal waste-
waters with currently available sampling equipment
is neither necessary nor justified.
9. Adequate discrete grab sampling programs for
routine surveys and monitoring of municipal
wastewaters require an inordinate amount of
laboratory resources and should be replaced with
automatic compositing equipment.
10. Current sampling equipment and methodologies need
to be refined to improve data reproducibility and
accuracy.
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Ill
11. Apparent wastewater chemistry characteristics
and facility removal efficiencies can easily be
manipulated by choice of sampling equipment and
methodology.
12. There is need for development of a synthetic
suspended solids waste to evaluate sampler
performance under controlled laboratory condi-
tions. '
13. Under ideal conditions the precision of flow
measurement by section personnel is ±10 percent.
------- OCR error (C:\Conversion\JobRoot\0000031A\tiff\20008TRA.tif): Saving image to "C:\Conversion\JobRoot\0000031A\tiff\20008TRA.T$F.T$F" failed.
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113
APPENDIX
NAMES AND ADDRESSES OF MANUFACTURERS AND
SUPPLIERS OF SAMPLERS LISTED IN TABLE I
Sigmamotor Model WA-2 and WD-2
Sigmamotor, Inc.
14 Elizabeth Street
Middleport, New York 14105
Brailsford Model EV-1, DU-1. and EP-1
Brailsford and Company
Milton Road
Rye, New York 10580
Hants Mark 3B
Testing Machines
400 Bayview Avenue
Amityville, New York 11701
ISCO Model 1391 and 1392
Instrumentation Specialties Company
P. 0, Box 5347
Lincoln, Nebraska 68505
Sirco MKV7S
Sirco Controls Company
401 Second Avenue West
Seattle, Washington 98119
Pro-Tech C6-125P
Pro-Tech, Inc.
Roberts Lane
.Malvern, Pennsylvania 19355
QCEC Model CVE
Quality Control Equipment Company
2505 McKinley Avenue
Des Moines, Iowa 50315
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114
N-Con Scout, Surveyor, and Sentinel
N-Con Systems Company, Inc.
Clean Waters Building
New Roche!le, New York 10801
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115
BIBLIOGRAPHY
1. Shelley, P. E., and Kirkpatrick, G. A., "An Assessment of
Automatic Sewer Flow Samplers," Prepared for Office of
Research and Monitoring, U.S. Environmental Protection
Agency, EPA-R2-73-261, Washington, D. C. (1973).
2. "Standard Methods for the Examination of Water and Wastewater,"
13th Ed., Amer. Pub. Health Assn., New York, N. Y. (1965).
3. Youden, W. J., "Statistical Techniques for Collaborative
Tests," Assn. of Offic. Anal. Chemists, Washington, D. C.
(1973).
4. "Water Measurement Manual," 2nd Ed., U.S. Dept. of Interior,
Bureau of Reclamation (1971) - Available from Super, of
Documents, U.S. Gov. Printing Office, Washington, D. C.
20402 - Order No. I 27.19/2: W29/2.
5. "Hydrographic Data Book," 8th Ed., Leupold Stevens, Inc.,
P. 0. Box 25347, Portland, Oregon 97225.
6. "Flow Tables for Circular Pipes," Manning Environmental Corp.,
112 Dakota Ave., Santa Cruz, Calif. 95060.
7. "Stream-Gaging Procedures," Water Supply Paper 888, U.S. Dept.
of Interior, Geological Survey (1962) - out of print.
8. Bauer, S. W., and Graf, W. H.s "Free Overfall as Flow Measur-
ing Device," Jour. Irrigation Drain. Div. Proc. Amer.
Soc. Civil Engr., 97, IR1., 7987 (1971).
9. "Peerless Pump Cat. B-127," Peerless Pump Div., Food Machinery
and Chem. Corp., 301 West Ave. 26, Los Angeles 31, Calff.
10. Smoot, C. W., "Orifice Bucket for Measurement of Small Dis-
charges from Wells," Water Resources Div. Bull., Illinois
Water Survey, Champaign, Illinois, Nov. (1963).
11. "Memos from Smitty," Water Well Journal, May-June (1955).
12. King, W. K., and Brater, E. F., "Handbook of Hydraulics,"
5th Ed., McGraw-Hill, New York (1963).
13. Davis, C. V., and Sorensen, K. E., "Handbook of Applied
Hydraulics," 3rd Ed., McGraw-Hill, New York (1969).
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116
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 907/9-74-005
3. RECIPIENT'S ACCESSION>NO.
4. TITLE AND SUBTITLE
Wastewater Sampling Methodologies and
Flow Measurement Techniques
5. REPORT DATE
June 1974 - Issue
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Daniel J. Harris and William J. Keffer
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
U.S. Environmental Protection Agency, Region VII
1735 Baltimore - Room 249'
Kansas City, Missouri 64108
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Technical Studies 10/72-11/73
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
The Superintendent of Documents classification number is: EP 1.2:W28/10
16. ABSTRACT
The structure and activities of the Environmental Protection Agency, Region VII,
Field Investigations Section are summarized and some 90,000 hours of collective
field operational experience with thirteen makes of commercially available automatic
wastewater samplers is presented. The results of five separate sampler performance
studies are reported which indicated significant differences in the wastewater
chemistry of samples collected concurrently by different automatic compositors and
manual sampling methods. High vacuum samplers were found to collect concentrations
of nonfilterable solids which were in some instances two and three times as great as
levels found in samples collected by slower acting samplers and by manual methods.
Minimum variations in solids data directly traceable to differences in samplers and
collection methods were on the-order of 9 to 24 percent. Hydraulic measurement
methods related to wastewater sampling activities are discussed. The precision of
three independent flow measurements were found to be approximately ±10 percent.
17.
KEY WORDS AND DOCUMENT ANALYSIS
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wastewater sampling, sampling equipment,
field sampling techniques, sampler
performance, wastewater characterization,
treatment plant performance
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