United States Environmental Monitoring and EPA-600/4-82-029
Environmental Protection Support Laboratory September 1982
Agency
Cincinnati OH 45268
Research and Development
Handbook for
Sampling and Sample
Preservation of
Water and
Wastewater
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EPA-60Q/4-82-029
HANDBOOK FOR
SAMPLING AND SAMPLE PRESERVATION
OF WATER AND WASTEWATER
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and
Support Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement.
11
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FOREWORD
Environmental measurements are required to determine the quality of
ambient waters and the character of waste effluents. The Environmental
Monitoring and Support Laboratory - Cincinnati:
Develops and evaluates techniques to measure the pres.ence and
centration of physical, chemical, and radiological pollutants
con-
water, wastewater, bottom sediments, and solid waste.
o Investigates methods for the concentration, recovery and
identification of viruses, bacteria, and other microbiological
organisms in water. Conducts studies to determine the responses of
aquatic organisms in water.
o Conducts an Agency-wide quality assurance program to assure
standardization and quality control of systems for monitoring water
and wastewater.
Standardized analytical methods and quality control procedures become
academic if samples are not representative of their original environment or
if constituents change between time of sampling and analysis. This
publication"provides guidelines and recommendations on techniques for
sampling and sample preservation to help alleviate these problems.
Procedures have been standardized as much as possible throughout this
document. However, sampling techniques cannot be predetermined for all
situations, so the use of statistical procedures to establish location and
frequency of sampling, number of samples, and parameters to be analyzed is
recommended when other guidelines do not exist. Sample preservation methods
and holding times are included for the parameters listed for the National
Pollutant Discharge Elimination System and Primary Drinking Water
Regulations. Special handling or sampling techniques are also included for
the individual constituents. Personnel establishing a sampling program
should find sufficient information to determine the best techniques to
apply.
This manual can not detail all aspects of sampling for water and
wastewater samples, therefore, references are provided for further study in
areas of interest.
m
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Finally, the guidelines and recommendations are not intended to super-
cede EPA enforcement requirements, rather to provide information to sampling
personnel. Sampling and sample preservation requirements for inhouse and
extramural projects, compliance monitoring and enforcement proceedings, and
other mandatory activities are specified by the responsible program.
Robert L. Booth
Acting Director
Environmental Monitoring & Support
Laboratory - Cincinnati
iv
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ABSTRACT
The four basic factors which affect the quality of environmental data
are sample collection, sample preservation, analyses, and recording.
Improper actions in any one area may result in poor data from which poor
judgements are certain. This manual was developed to provide general and
specific guidance in sample collection and preservation.
A review of the literature and a survey of field practices provide the
basis for guidelines in general sampling techniques, samplers, flow
measuring devices, a statistical approach to sampling, preservation of
samples for physical, chemical, biological and radiological analyses,
procedures for sampling waters from municipal, industrial, and agricultural
sources, surface waters, and sludges.
Finally this handbook does not supersede sampling, preservation, or
chain of custody procedures specified by enforcement, compliance monitoring,
or program offices of the U.S. Environmental Protection Agency. Rather it
is intended to complement their requirements.
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CONTENTS
Foreword iii
Abstract v
Acknowledgement xi
1. Introduction ...... . 1
2. General Considerations for a Sampling Program 2
2.1 Objectives of Sampling Programs 2
2.2 Sampling Locations 4
2.3 Sample Collection Methods . 6
2.4 Type of Sample 19
2,5 Planning a Sampling Program . 30
2.6 Field Procedures ........ . 37
2.7 References ........... 39
3. Flow Measurements . . 41
3.1 Closed Conduit Flow Measurement 41
3.2 Flow from Pipes Discharging to the Atmosphere 53
3.3 Open Channel Flow Measurements 57
3.4 Miscellaneous Flow Measurement Methods . 81
3.5 Secondary Devices 88
3.6 References 102
4. Statistical Approach to Sampling 105
4.1 Basic Statistics and Statistical Relationships 105
4.2 Determination of Number of Samples 141
4.3 Determining Sampling Frequency 144
4.4 Determination of Parameters to Monitor 146
4.5 In-Plant Sampling and Network Monitoring . . 154
4.6 References 168
5. Sampling Municipal Wastewaters .... 170
5.1 Background 170
5.2 Objectives 170
5.3 Frequency of Sampling 170
5.4 Location of Sampling Points 171
5.5 Number of Samples 176
5.6 Parameters to Measure 177
5.7 Type of Sample 177
VI
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5.8 Methods of Sampling 177
5.9 Volume of Sample and Container Type 178
5.10 Preservation and Handling the Samples 178
5.11 Flow Measurements 179
5.1? References ........... 179
6. Sampling Industrial Wastewaters .... 180
6.1 Background * . . . * 180
6.2 Objectives of Sampling Programs 180
6.3 Frequency of Sampling 181
6.4 Location of Sampling Points 181
6.5 Number of Samples 183
6.6 Parameters to Measure 183
6.7 Type of Sample 186
6.8 .Method of Sampling 186
6.9 Volume of Sample and Container Type ..... 187
6.10 Preservation and Handling of Samples 187
6.11 Flow Measurement 187
6.12 References 187
7. Sampling Agricultural Discharges 188
7.1 Background 188
7.2 Objectives 188
7.3 Frequency of Sampling ......... .... 188
7.4 Location of Sampling Points ,,..,.......,.. 189
7.5 Number of Samples 189
7.6 Parameters to Analyze ..... 189
7.7 Type of Sample 190
7.8 Method of Sampling 190
7.9 Volume of Sample and Container Type '. 190
7.10 Flow Measurement 190
7.11 References 194
8. Sampling Surface Waters, Aquatic Organisms and Bottom Sediments 195
8.1 Background 195
8.2 Objectives of the Study 195
8.3 Parameters to Measure 195
8.4 Location of Sampling Points 195
8.5 Random Sampling 200
8.6 Frequency of Sampling 203
8.7 Method of Sampling 203
vii
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8.8 Types of Samples for Aquatic Organisms ... 203
8.9 Volume of Sample and Container Type 203
8.10 Preservation and Handling of Samples 217
8.11 Flow Measurement 217
8.12 References 217
9. Sampling of Ground and Drinking Water 218
9.1 Background 218
9.2 Objectives of Ground Water Sampling 218
9.3 Ground Water Subsurface Characteristics . 219
9.4 Location of Ground Water Sampling Points 220
9.5 Construction of Ground Water Monitoring Wells 227
9.6 Collection of Ground Water Samples 234
9.7 Sampling Ground Water Subsurface Solids 250
9.8 Preservation and Handling Procedures for Ground Water
Parameters 251
9.9 Sampling of Drinking Water 255
9.10 References 267
10. Sampling Sludges 269
10.1 Background . 269
10.2 Objectives of Sampling Programs 269
10.3 Parameters to Analyze . 270
10.4 Location of Sampling Points 270
10.5 Frequency of Sampling 272
10.6 Number of Samples 272
10.7 Type of Sample 272
10.8 Method of Sampling 273
10.9 Volume of Sample and Container Type 273
10.10 Preservation and Handling of Samples 273
10.11 Flow Measurement 273
10.12 References ......... 273
11. Suspended Solids Sampling 275
11.1 Representative Sampling Theory 275
11.2 Segregation Sampling Error 275
11.3 Field Sampling 280
11.4 Laboratory Subsampling 281
11.5 Guidelines of Sampling of Suspended Solids 285
11.6 References 285
vm
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12. Sampling, Preservation and Storage Considerations for Trace
Organic Materials 286
12.1 Sample Collection Method 292
12.2 Sediment Sampling 293
12.3 Sampling Location 303
12.4 Sample Container 303
12.5 Sampling Procedure and Pretreatment of Sample Equipment . 305
12.6 Sample Preservation and Storage 306
12.7 References 310
13. Sampling Radioactive Materials 313
13.1 Background 313
13.2 General Considerations 315
13.3 Frequency of Sampling 316
13.4 Location of Sampling 318
13.5 Sample Volume 318
13.6 Sample Containers 319
13.7 Sample Filtration 319
13.8 Sample Preservation 320
13.9 General Sampling Procedure - Water & Wastewater 320
13.10 Radiation Safety 321
13.11 References 321
14. Collecting and Handling Microbiological Samples 323
14.1 Background 323
14.2 Analytical Methodology 323
14.3 Sample Bottle Preparation 326
14.4 Sample Methods and Equipment 327
14.5 Sample Frequency and Site Selection 337
14.6 Preservation and Transit of Samples 343
14.7 References 344
15. Sample Control Procedures and Chain of Custody 345
15.1 Sample Identification 345
15.2 Chain of Custody Procedures 348
15.3 Field Notes 355
15.4 References 355
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16. Quality Assurance ..... 356
16.1 Objectives of Quality Assurance Program 356
16.2 Elements of a Quality Assurance Plan 357
16.3 Personnel Training 357
16.4 Quality Assurance in Sampling 359
16.5 EPA Quality Assurance Program ..... 365
16.6 References 367
17. Sample Preservation 368
17.1 Methods of Preservation 368
17.2 Containers 394
17.3 Holding Time 397
17.4 Sample Volume 397
17.5 References ........ ......... 397
Appendix A 401
Appendix B 402
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ACKNOWLEDGEMENT
The material in this handbook covers a wide range of subject areas with
respect to Sampling and Sample Preservation of waters and wastewaters. Many
people, too numerous to list, made worthwhile contributions to the
successful completion of this Handbook. However, I wish to express my
appreciation and special thanks to the following:
(a) Envirex, Inc., who provided the original contract report,
EPA 600/4-76-049, upon which this handbook was built.
(b) Bionetics, Inc., particularly, V. Kowalski, A.J. DiPuccio,
T.V. Gala and other administrative and clerical personnel, who
were responsible for conducting an extensive literature search and
condensing the information into subsequent chapters in this handbook.
(c) U.S. Environmental Protection Agency Personnel, M.R. Scalf, J.F.
Cosby; and Robert S. Kerr Environmental Research Lab, Ada Oklahoma,
for authoring the chapter on ground water sampling.
(d) U.S. Environmental Protection Agency personnel, J.W. Winter, R.H.
Bordner, EMSL-Cincinnati, for authoring the chapter on
microbiological sampling.
(e) U.S. Environmental Protection Agency personnel, R.L. Graves and
H.E. Kolde, for authoring the chapters on trace organics and
radiological sampling, respectively.
(f) U.S. Environmental Protection Agency, P. Britton for his valuable
input and editing of the statistics chapter.
(g) U.S. Environmental Protection Agency, E.L. Berg, EMSL-Cincinnati
for authoring chapters on drinking water, flow measurement, and
suspended solids.
(h) Finally, special thanks to the over 250 reviewers representing the
federal, state and local governments, commercial manufacturers of
sampling equipment, industry, and engineering consulting firms.
Edjtor
Edward L. Berg, P.E.
Environmental Monitoring & Support Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio
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CHAPTER 1
INTRODUCTION
Obtaining representative samples and maintaining their integrity
are critical parts of any monitoring or enforcement program. Analytical
methods have been standardized but the results of analyses are only as good
as the sampling and the sample preservation methods. The purpose of this
handbook is to present the best techniques currently available for sampling
and sample preservation. The recommendations were developed after an
extensive literature review and survey of current laboratory and field
practices. The handbook will allow personnel to determine the most
effective procedures for their specific applications.
In sampling, the objective is to remove a small portion of an environ-
ment that is representative of the entire body. Once the sample is taken,
the constituents of the sample must stay in the same condition as when
collected. The length of time that these constituents will remain stable is
related to their character and the preservation method used.
The sampling technique is determined by the type of water or wastewater
to be sampled. This handbook primarily addresses the water and wastewater
types shown below and addresses in a limited way, sampling of oceans and
estuaries..
1. Municipal wastewaters 4. Agricultural run-off
2. Industrial wastewaters 5. Wastewater sludges
3. Surface waters and 6. Ground water
sediments 7. Drinking water
General information on automatic samplers, flow monitoring and
statistical methods used to determine number of samples, frequency of
sampling, location of sampling, and parameters to be measured are included.
Special consideration is given to sampling for suspended solids, trace
organics and radioactive substances.
Since preservation methods relate to the parameters to be analyzed,
these techniques are classified by parameter.
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CHAPTER 2
GENERAL CONSIDERATIONS FOR A SAMPLING PROGRAM
Most definitions of water quality are use-related. Each user produces
wastewaters containing pollutants which impacts the environment in different
ways. For example, power plants discharge thermal pollution that impacts
the biological population, household nutrient discharges lead to
eutrophication of lakes, industrial discharges cause oxygen depletion or
discharge toxic substances which kill fish. The broad spectrum of ground
water, surface waters, lakes, estuaries, coastal waters, municipal wastes,
industrial wastewaters and surface r'un-offs make monitoring of water quality
a formidable task. Sampling is the first key element in a monitoring
program that must be performed properly to assure valid data. No single
sampling program can apply to all types of waters, nevertheless, each
sampling program must consider:
1. Objectives of Sampling Program 4. Sample Collection Methods
2. Location of Sampling Points 5. Flow Measurements
3. Types of Samples 6. Field Procedures
2.1 OBJECTIVES OF SAMPLING PROGRAMS
There are four major reasons for sampling and analyses program;
planning, research or design, process control, and regulation. These
objectives in an overall water quality program are interrelated and cover
different stages from planning to enforcement. Based upon these objectives,
the different sampling programs are compared in general terms in Table 2.1.
Since the objectives of a program directly affect sampling and laboratory
analyses, specifying the objectives is the first step in planning a sampling
program.
2.1.1 PIanning Obj ecti ves
An area-wide or basin planner monitors to:
1. Establish representative baseline water quality conditions;
2. Determine assimilative capacities of streams;
3. Follow effects of a particular project or activity;
4. Identify pollutant source;
5. Assess long term trends;
6. Allocate waste load; or,
7. Project future water characteristics.
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2.1.2 Research Objectives
Water/wastewater research projects conduct sampling and analyses toi
1. Determine the treatment efficiency for a unit process or overall
treatment system,
2. Determine the effect of changes in process control variables,
3. Characterize influent and effluent streams and sludges,
4. Optimize chemical dosages, loadings for carbon adsorption columns,
for advance waste treatment processes or treatment of drinking
water, or
5. Ascertain health effects of effluents, sludges, drinking waters and
ambient waters.
2.1.3 Process Control Objectives
Water/wastewater treatment process and associated systems conduct
sampling and analyses to:
1. Produce an effluent of the highest quality,
2. Optimize and maintain physical, chemical, and biological process
control variables that affect treatment efficiency, i.e. mixed
liquor suspended solids, sludge withdrawal rate, dissolved oxygen,
chemical dosages, etc,
3. Determine resource recovery from unit processes,
- 4. Allocate the cost of treatment to a unit within a complex of unit
processes, or
5. Determine substances that are toxic or interfere with the treatment
system.
TABLE 2.1 COMPARISON OF SAMPLING PROGRAMS BASED ON OBJECTIVES
Objectives
Scope
Goals
Effort
Planning
General
Establish
trends
Benchmarks
Background
levels
Non-intensive
and unlimited
Research
Design
Specific
New Develop-
ments
Modifications
Improvements
Intensive
and limited
Process
Control
Specific
Operation
quality
control
Non- intensive
and limited
Regulatory
Specific
Verification
compliance
enforcement
Non-intensive
and limited
\
\ ; /, ,
2.1.4 Regulation Objectives
Most sampling surveys and subsequent analyses are performed to meet the
requirements of federal, state, or local regulations. An example of reguTa-
tory monitoring is the National Pollutant Discharge Elimination System
(NPDES') established in accordance with the Federal Water Pollution Control
-------
Act Ammendments of 1977 and 1978 (P.L. 92-500). Specific objectives in
collecting regulatory data vary considerably and often overlap, but
generally are performed to:
1. Verify self-monitoring data,
2. Verify compliance with NPDES permit,
3. Support enforcement action,
4. Support permit reissuance and/or revision, or
5. Support other program elements such as water quality standards
requiring wastewater data.
2.2 SAMPLING LOCATIONS
2.2.1 General Considerations
Usually, the sampling program objectives define the approximate
locations for sampling, for example, influent and effluent to a treatment
plant or water supply intake. Often, however, the sampling program
objectives give only a general indication, such as the effect of a surface
runoff on a river quality when assessing the quality of drinking water
supplies for a community.
Since water quality varies from place to place in most water systems,
locations appropriate to the information needs of a particular program must
be selected. The nature and extent of spatial heterogeneity can vary with
time, and can also differ markedly between systems of the same type. A
typical case may be a zone where fresh and saline waters are mixing.
No specific guidelines can be given on the exact locations for sampling;
however, some general points are given in Section 2.2.2 and 2.2.3 when
considering sampling locations.
2.2.2 Relevant Factors in Selecting Sampling Locations
The selected sampling locations must be representative sites. The term
"representative point" is defined in 40 CFR, Part 35, subpart B, Appendix A,
p. 224, 1976 as a location in surface waters or ground waters at which
specific conditions or parameters may be measured in such a manner as to
characterize or approximate the quality or condition of the water body; or
a location in process waters or wastewaters where specific conditions or
parameters are measured that adequately reflect the actual conditions of
those waters or wastewaters.
Factors influencing the selection of sampling locations are:
homogenity of the water or wastewater. Turbulence and good
mixing resulting from a hydraulic jump and spring and fall
turnovers of a lake, respectively, enhance the homogenity or
the uniform distribution of the contituents in the body of
water.
Non-homogenity of the water or wastewater. Poor mixing, for
example, stratification in lakes or a river downstream of a
4
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waste discharge. Different densities of the constituents, such
as floating oils or settling suspended solids. Chemical or
biological reactions, such as growth of algae in upper layers
of the body of water, causing changes in pH,
Other considerations such as pronounced degradation of water
quality in specific areas, suitability for flow measurements,
convenience and accessability.
2.2.3 Selection of Sampling Locations (1)
The selection of the location of sampling must consider:
1. Homogeneity of water or wastewater:
At significant outlets and inputs of lakes, impoundments,
estuaries or coastal areas that exhibit eutrophic
characteristics.
At locations upstream and downstream of major population and/or
industrial centers which have significant discharges into a
flowing stream.
Upstream and downstream of representative land use areas and
morphologic zones.
From several locations to obtain the required information.
2. General characteristics of water or wastewater: (1)
At representative sites in mainstream of rivers, estuaries,
coastal areas, lakes or impoundments.
In major water use areas, such as public water supply intakes,
commercial fishing areas and recreational areas.
At representative sites in the individual waste streams.
At the mouths of major or significant tributaries to
mainstreams, estuaries or coastal areas.
3. Pronounced water quality degradation:
At critical locations (which have the potential for displaying
the most pronounced water quality or biological problems) in
water quality limiting areas.
At critical locations within eutrophic or potentially eutrophic
lakes, impoundments, estuaries, or coastal areas.
4. Flow Measurement:
Locations where corresponding discharges are known or can be
estimated.
5. Convenience, accessibility and practicability are certainly
important but they must be secondary to representativeness of sampling.
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2.3 SAMPLE COLLECTION METHODS
Samples can be collected manually or with automatic samplers. Whichever
technique is adopted, the success of the sampling program is directly
related to the care exercised in the sample collection. Optimum performance
will be obtained by using trained personnel.
2.3.1 Manual Sampling
There is minimal initial cost involved in manual sampling. The human
element is the key to the success or failure of manual sampling programs.
It is well suited to a small number of samples, but is costly and time
consuming for routine and large sampling programs. Table 2.2 lists some of
the advantages and disadvantages of manual and automatic sampling. Various
types of manual grab samplers are described throughout the Handbook.
2.3.2 Automatic Samplers
Automatic samplers are being used increasingly because of their cost
effectiveness, versatility and reliability, improved capabilities - greater
sampling frequency, and increased sampling needs because of the NPDES
permit program.
Automatic samplers are available with widely varying levels of
sophistication, performance, mechanical reliability and cost. Table 2.3
lists different automatic samplers and their characteristic features.(3)
However, no single automatic sampling device is ideally suited for all
situations. For each application the following variables should be
considered in selecting an automatic sampler: (4)
Variation of water or wastewater characteristics with time.
Variation of flow rate with time.
Specific.gravity of liquid and concentrations' of suspended
solids.
Presence of floating materials.
Selection of a unit or a variety of units for sampling should be
preceded by a careful evaluation of such factors as:
The range of intended use.
The skill level required for installation of the automatic
sampler.
The level of accuracy desired.
References 5,6,7,8, and 9 have useful information on the theoretical
design considerations and actual field performance data for automatic
samplers.
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TABLE 2.2 THE ADVANTAGES AND DISADVANTAGES OF MANUAL AND AUTOMATIC SAMPLING
Type
Advantages
Disadvantages
Manual Low capital cost
Compensate for various
situations
Note unusual conditions
No maintenance
Can collect extra samples in
short time when necessary
Automatic Consistent samples
Probability of decreased
variability caused by
sample handling
Minimal labor requirement
for sampling
Has capability to collect
multiple bottle samples for
visual estimate of variability
& analysis of individual
bottles
Probability of increased
variability due to sample
handling
Inconsistency in collection
High cost of labor*
Repetitious and monotonous
task for personnel
Considerable maintenance for
batteries & cleaning;
susceptible to plugging by
solids
Restricted in size to the
general specifications
Inflexibility
Sample contamination
potential
Subject to damage by vandals
* High cost of labor assumes that several samples are taken daily, large
distances between sampling sites, and labor is used solely for sampling.
'2.3.2.1 Criteria for Evaluating Automatic Sampler Subsystems
There are usually five interrelated subsystems in the design of an
automatic sampler. The criteria for selecting subsystems are briefly
described below; more detailed information can be found in references 5,6,
and 9.
2.3.2.1.1 Sample Intake Subsystem
The success of an automatic sampler in gathering a representative sample
depends on sampling site conditions (4) and the design of the sample intake
subsystem. The reliability of a sample intake subsystem is measured in terms
of:
. Freedom from plugging or clogging.
Non-vulnerability to physical damage.
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TABLE 2.3 AUTOMATIC SAMPLERS AND THEIR CHARACTERISTIC FEATURES (3)
MAHUFUCTVIEH
BIFSanitrol
Brailsford
Brailsford
Brailsford
Brailsford
BVS
BVS
BVS
BVS
Bristol
Chandler
Collins
EMA
ETS
Fluid Kinetics
FMC Corp,
Horizon
Hydragard
Hydra-Numatic
ISCO
ISCO
ISCO
Lakeside
Manning
Manning
Manning
Manning
Manning
Markland
Markland
MOOR M.
414
EVS-3B
DC-F
DU-2
EP
PP-100
PPR-100
SE40Q
SE-600
M-4KT
SR-10
40-2 R
200 AC
FS4
Custom
Design
Tru-Test
7578
FP
HNS
1392
1480
1S80
T2
S-3000
S4040
S4050
S-5000
S-6000
1301
2104T-CLK
rf_
Is
10.2
23.2
23.2
23.2
H
H
L
93.3
75
96.3
24.1
96.3
H
H
H
H
M
*-*_.
=£*
£K
.gja
762
182
213
213
213
6096
6096
975
671
610
77
883
457
914
457
790
790
790
870
670
670
670
670
914
.914
ci
si
3.16
3.16
3.16
3.16
3.16
12.7
50.8
9.5
9.5
50.8
4.8
9.5
12.7
6.35
6.35
6.35
12.7
9.5
9.5
9.5
16
16
6.35
6.35
TYP E Of
PUMP
Dipper
Vacuum
Piston
Piston
Piston
Pressure
Pressure
Submersible
Submersible
Plunget into
Pipeline
Vacuum
Moyno
Solenoid
Plunger
Peristaltic
Centrifugal
Peristaltic
Pressure
Impeller
Peristaltic
Peristaltic
Peristaltic
Scoop
Vacuum
Vacuum
Vacuum
Vacuum
Vacuum
Pressure
Pressure
sa
2B
X
X
X
X
X
X
X
X
X
ct
It
X
X
X
X
X
X
X
X
X
X
X
X
mo
II
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
s
ss
S3
X
X
X
X
X
X
X
X
X
X
X
X
X
X
tJ
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
ram
"M
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1
X
X
X
X
X
r
•e
So
S3
I*
F
p
p
p
p
p
p
F
F
F
F
F
F
P
F
F
P
P
F
P
P
P
F
P
P
P
F.
F
P
F
00
X-HAS, U-USER SUPPLIED, L-LOW, H-HIGH
Costs are 1975 prices, except Manning which are 1981 prices.
(continued)
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TABLE 2.3 AUTOMATIC SAMPLERS AND THEIR CHARACTERISTIC FEATURES (3)
MMUMCntER
N-Con
N-Con
N-Con
N-Con
N-Con
NP Enterprises
PhipsS Bird
Pro-Tech
Pro-Tech
Pro-Tech
Pro-Tech
QCEC
QCEC ,
QCEC
QCEC
Sigmamotor
Sigmamctor
Sigmamotor
Sigmamotor
Sigmamotor
Sigmamotor
Sigmamotor
Sigmamotor
SIRCO
SIR CO
SIRCO
SIRCO
Sonford
Sonford
TMI
TMI
Tri-Aid Sciences
Waste Watcher
KHMH. NO.
Surveyor
Scout
Sentry
Trebler
Sentinel
NPE
8392-300
CG-125
CG-150
CEL-300
DEL-240S
CVE
E
CVE II
LF
WD-1
WD-5
WM-4-24
WM-B-24
WAP-2
WAP-5
WM-1-24R
WAC-5R
B/ST-VS
B/IE-VS
B/OP-VS
MK-VS
NW-3
HG4
MARK 3B
MARK 48
Cuitom
Ossign
CS/TP
M«5"
IK
<*c
275
520
1100
1600
850
800
aoo
1500
5700
570
1000
950
980
650
1100
1100
1400
700
1050
1525
1300
two-
2350
HOC-
mt
nn-
mi
B75-
1364
1000
500
845
950
1425
OIKEHSIMS
WO. i OEPTH i Ht.
or Oil. 1 HI
(mi)
Small
35.6x15.3x43.2
40.6x35.6x33
68.5x25.4x147.4
33 x 25.4 x 43.2
33 x 25.4 x 43.2
33 x 48.3 x 43.2
^6.2x81.2x182.9
38.1 x 38.1 x 60.9
20.3 x 33 x VAR.
38.1x43.2x38.1
39.4 x 7.7
34.3 x 25.4 x 36.9
50 x 37 x 64
50x37x64
50 x 37 x 64
34.3 x 25.4 x 38.9
50 x 37 x 64
53.4x55.9x86.4
63.4 x 55.9 x 125
40.7x40.7x55.9
39.4 x 39.4 x 68
33.8x31.4x33,5
36.8x66
38 x 38 x 47
20x20x7
r
L
10
15.9
84
9.1
9.1
13.7
24.9
45.4
15.9
10
14
27
25.4
29
11.4
19.1
56.8
44.5
127
123
91
17
23.2
14.5
20.2
10.5
SMPtE
units
NIL
1
1
24
1
1
1
1
1
1
1
24
1
1
1
1
1
1
24
24
1
1
24
1
24
1
24
!
24
24
1
12
24
1
cm.
M
U
3785
450
U
7570
U
5678
5678
5678
100
1893
U
3785
U
9462
18,925
450
450
9462
18,925
450
18,925
473
16.110
500
473
3785
570
570
U
M,S
EB
t»
Ref.
Ref.
Ref.
Ref.
Ice
Ice
Ref.
Ref.
Ref.
Ref.
Ref.
Ref.
l*!EItl«,S EIPOSEO
TO SAMPLES
imnu
U
Polypropylene
Glass
U
Polyethylene
U
TFE Resins
TFE Resins
TFE Resins
TFE Resins
Glass
Glass
U
Plastic
Plastic
Plastic
Plastic
Plastic
Plastic
Plastic
Plastic
Polyethylene
Stainless
Polyethylene
Plastic
Glass
Polyethylene
Glass
Glass
U
Tubing
U
Tygon
Tygon
TFE Resins
TFE Resins
PVC
Stainless
Tygon
Plexiglas
U
Tygon
Tygon
Tygon
Tygon
Tygon
Tygon
Tygon
Tygon
Plexiglas
PVC
PVC
PVC
Tygon
Tygon
Tygon
Silicone
Tygon
Otto
Buna-N
Silicone
Silicone
PVC
PVC
Stainless
PVC
PVC
PVC
PVC
Plexiglas
Stainless
Brass
Stainless
PVC
Plexiglas
Plexiglas
Stainless
Stainless
Stainless
Stainless
Silicone
*%
fif
«s-
H
12,1
12.1
H
99.7
99.7
H
H
9.7
4.2
9.7
4.2
9.7
4.2
9.7
Var.
H
140
34
HUULUf!
[cm HjO)
182
457
457
L
305
914
914
914
914
610
610
670
548
670
548
670
548
670
670
6096
670
396
53
300
300
762
670
s
gl
12.7
6,35
6.35
50.8
3,16
3.16
12.7
12.7
6.35
12,7
3.16
6.35
3.16
6.35
3,18
6.35
3.16
3.16
9,53
9.53
6.35
6.35
6.35
9.53
7.9
TYPE OF
PUMP
Impeller
Peristaltic
Peristaltic
Scoop
U
Vacuum
D ipper
Pressure
Pressure
Submersible
Submersible
Vacuum
Dipper
Vacuum
Planfler into
Pipeline
Nutating
Finger
Nutating
Finger
Nutating
Finger
Nutating
Finger
Vacuum
Dipper
Pressurized
Sou cce
Vacuum
Evacuated
Bottle;
Telescoping
Tube
Evacuated
Bottles
Evacuated
Bottles
Peristaltic
Peristaltic
Sj
«C3
X
X
X
X
X
X
X
X
X
X
X
X
CONTROLS
II
X
X
X
X
X
X
II
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
S~
Rm
X
X
X
POWER
U
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
S
x
X
X
X
X
X
X
X
X
X
X
1
X
X
w
X
X
X
X
mm «
)is»mod
P
P
P
F
F
F
F
P
P
P
F
•P
F
P
F
P
P
P
P
P
P
F
F
F
F
F
P
P
P
P
P
F
F
X-HAS, U-USER SUPPLIED, L-LOW, H-HIGH
Costs are 1975 prices, except Manning which are 1981 prices.
-------
. Minimum obstruction to flow.
. Capability to draw a representative sample.
. Multiple intakes.
Rigid intake tubing or facility to secure or anchor the intake
tubing. Avoidance of sharp bends, twists, or kinks to prevent
clogging of intake line.
. Compatible materials
2.3.2.1.2 Sample Gathering Subsystem
Three basic sample gathering methods available in commercial samplers
are: mechanical, forced flow, and suction lift. Figures 2.1 and 2.2
illustrate forced flow and suction lift sample gathering subsystems,
respectively. Figures 2.3 and 2.4 illustrate a mechanical sample gathering
subsystem at a weir and flume installation respectively. These subsystems
are compared in Table 2.4.
2.3.2.1.3 SampleTransport System
A majority of commercially available composite samplers have fairly
small diameter tubing in the sample train which is vulnerable to plugging,
due to the buildup of fats-, other solids and insoluble components. Adequate
flow rates must be maintained throughout the sampling train to effectively
transport suspended solids.
To optimize sampler performance and reliability, the following features
and procedures are desirable:
Use a sample transport line with at least a 6 mm (i inch)
internal diameter.
For most applications, select samplers which minimizes contact
of the water/wastewater with metal surfaces during sample
transport.
For peristalic pumps, use a sample line which is transparent
and flexible, and made of an inert material such as Tygon. For
collection of organics, use sample lines constructed of
silicone rubber. Do not, use silicone rubber transport lines
for trace metal sampling since zinc is a major contaminant.(8)
Conduct tests on sample transport lines and containers to
assure that the sample is not contaminated.
Prevent clogging of sample lines by avoiding sharp bends,
twists, or kinks.
Flush the sample line prior to and immediately after each
sample collection. A clean water flush is effective (4) but
not feasible in most instances. A complete air purge is
sufficient for non-permanent or winter operation.
Select a sample pump capable of lifting a sample a vertical
distance of 6.1 m (20 feet) and maintaining a line velocity of
0.6 to 3.0 m/sec. (2 to 10 ft/sec.).(7)
10
-------
PRESSURE OPERATION
Propellant under pressure from a source (A)
is metered by a control valve (B) for rate-
meter (C) into accumulator tank (0). On
reaching a preselected pressure, a pneu-
matic relay (E) releases the accumulated
propellant through inlet line (F) to the sample
intake chamber (G). Pressure in the chamber
closes its chor.-k valve (H) and propels the
sample through outlet line (I) and into the
sample bottle (J). Excess propellant vents
through the sample line, thereby purging it of
liquid and incidentally providing protection
against line freezing in cold weather. The
resulting pressure drop recloses the relay (E)
and the sampling cycle repeats at a repeti-
tion rate determined by adjusting the control
valve (B).
PRESSURE
OPERATION
H"
Figure 2.1 Schematic of Forced Flow Type Sampler
-------
COMPRESSOR
CONTROLS
FILL SENSOR
n
INLET HOSE
VALVE
SAMPLE SIZE
ADJUSTMENT
MEASURING
CHAMBER
T"
STEPPING
MOTOR
I
SPOUT ROTARY UNION
DISCRETE
SAMPLE BOTTLES
] VALVE
COMPOSITE
INTAKE
Figure 2.2 Schematic of Suction Lift Type Sampler
12
-------
Parts List
No.
Description
1. Motor-Reducer
2. Drive Sprocket
3. Driven Sprocket
4. Roller Chain
5. Scoop
6. Scoop Counter Weight(not shown)
7. Limit Switch
8. Time Clock
9. Alum. Sampler Casting
10. Alum. Sampler Support
11. Outlet Coupling
12. Unilet Body & Cover
V-NOTCH WEIR
(RSCTANGULAB OR CIFOLLSTT1
WEIRS ARE OPTIONAL)
CALV. ANCHOR
iOLTS OR ACKERMAN
Figure 2.3 Schematic of Mechanical Type Sampler (Weir Installation)
13
-------
Parts List
No.
Description
1. Motor — Reducer
2. Drive Sprocket
3. Driven Sprocket
4. Roller Chain
5. Scoop
6. Scoop Counter Weight(not shown)
7. Limit Switch
8. Time Clock
9. Alum. Sampler Casting
10. Alum, Sampler Support
11. Outlet Coupling
12. Unilet Body S. Cover
Q*LV.*HCMO«
•OlTSO« AC***"**.
Figure 2.4 Schematic of Mechanical Type Sampler (Flume Installation)
14
-------
TABLE 2.4 COMPARISON OF SAMPLE GATHERING SUBSYSTEMS
Feature
Lift
Sample intergra-
tion over the
entire depth
Obstruction to
flow
Explosion-proof
Dissolved gasses
Fouling
Sample Volume
Flexibility
Maintenance
Mechanical
High
Possible
Significant
Some
No problem
Exposed parts
have a
tendency to
foul
Suitable for
wide range
Limited
Heavy
Forced Flow
High
Possible with
pumps but not
with ejection
units
Less than mechan-
ical subsystem
Pneumatic ejection
units meet this
requirement
No problem
Not easily
fouled
Pump suitable
for wide range
Pneumatic ejection
units suitable
for sample volume
Moderate
Moderate but
costly
Suction Lift
Limited to 7.6 m
25 feet) or less
Possible with
multiple intakes
Very little
Some
Not suited but if
used, the initial
flow should be
discarded
Intake tubing of
less than 6 mm
(1/4") I.D. is
prone to fouling
Should be inde-
pendent of ver-
tical lift
Maximum
Little
The importance of line velocity and isokinetic conditions
(intake velocity same as velocity of flow of water) depends on
the concentration and density of the non-filterable suspended
solids in the water, the program requirements for accuracy of
suspended solids determinations, and any other parameters
affected by suspended solids concentrations. If a program
requires maintaining isokinetic conditions, dial adjustment of
intake velocity is a desired feature.
15
-------
All materials should be examined to assure that they do not
contaminate the sample.
2.3.2.1.4 Sample Storage Subsystem
Discrete samples are subject to considerably more error introduced
through sample handling, but provide opportunity for manual flow compositing
and time history characterization of a waste stream during short period
studies. The desired features of sample storage subsystems are:
Flexibility of discrete sample collection with provision for
single composite container.
Minimum discrete sample container volume of 500 ml (0.13 gal.)
and a minimum composite container capacity of 7.57 L (2.0
gal.).
Storage capacity of at least 24 discrete samples.
Containers of conventional polyethylene or borosilicate glass
and of wide mouth construction.
Capability for cooling samples by refrigeration or a space for
packing ice and maintaining samples at 4 to 6 C(39 to 43 F)
for a period of 24 hours at ambient temperature range between
-30° to 50°C (-22° to 122°F).
Adequate insulation for the sampler to be used in either warm
or freezing ambient conditions.
2.3.2.1.5 Controls and Power Subsystem
The following are desired power and controls features which may be
necessary depending upon whether the sampler is to be portable or a permanent
installation:
Capability for either AC (Electrically grounded system) or DC
operation.
Battery life for two to three days of reliable hourly sampling
without recharging.
Battery weight of less than 9 kg (20 Ib.) and sealed so no
leakage occurs.
Solid state logic and printed circuit boards.
Timing and control systems contained in a waterproof
compartment and protected from humidity. Timer should use
solid state logic and a crystal controlled oscillator.
Controls directly linked to a flow meter to allow both
flow-proportional sampling and periodic sampling at an
adjustable interval from 10 minutes to 4 hours.
Capability of multiplexing, that is, drawing more than one
sample into a discrete sample bottle to allow a small
composite over a short interval. Also capability for
filling more than one bottle with the same aliquot for
addition of different preservatives.
Capability of adjusting sample size and ease in doing so.
16
-------
2.3.2.1.6 General DesirableFeatures
For safety, maintenance, reliability and security in field applications,
the following general features are desired in an automatic sampler:
Water tight casing to withstand total immersion and high
humidity.
Vandal proof casing with provisions for locking.
A secure harness or mounting device if sampler is placed in a
sewer.
Explosion proof construction.
Sized to fit in a standard manhole without disassembly.
Compact and portable for one-man installation.
Overall construction, including casing, of materials
resistant to corrosion (plastics, fiberglass, stainless steel).
Exterior surface painted a light color to reflect sunlight.
Low cost, availability of spare parts, warranty, ease of
maintenance, reliability and ruggedness of construction.
2.3.2.2 Installation and Use
2.3.2.2.1 General Consideration
Sampling equipment will yield good results only when properly installed
and maintained. A few general guidelines follow:
When a sampler is installed in a manhole, secure it either
in the manhole, for instance, to a rung above the high water
line or outside the manhole to an above ground stake by means
of a rope.
Place the intake tubing vertically or at such a slope to ensure
gravity drainage of the tubing between samples, avoiding loops
or dips in the line.
Clean sample bottles, tubing and any portion of the sampler
which contacts the sample between setups. Whatever methods of
cleaning are used, all parts of the sampler which come in
contact with the sample should be rinsed with tap water and
then given a final rinse with distilled water. A distilled
water rinse may not be necessary between setups on the same
waste stream.
Inspect the intake after each setup and clean, if necessary.
Exercise care when placing the intake(s) in a stream containing
suspended solids and run the first part of the sample to waste.
Maintain sufficient velocity of flow at all times to prevent
deposition of solids. When a single intake is to be used in a
channel, place it at six-tenths depth (point of average
velocity). (10)(11) For wide or deep channels where
stratification exists, set up a sampling grid as shown in
section 8.4.
Maintain electrical and mechanical parts according to the
manufacturer's instructions. Replace the desiccant as needed.
If a wet-cell lead-acid battery is used, neutralize and clean
17
-------
up any spilled acid.
Position the intake in the stream facing upstream. Limit the
orientation of the intake 20 degrees on either side of the
head-on. Secure the intake by a rope at all times with no drag
placed on the inlet tubing.
After the installation is complete, collect a trial sample to
assure proper operation and sample collection. The sampler
must give replicate samples of equal volume throughout the flow
range. If the sampler imposes a reduced pressure on a waste
stream containing suspended solids, run the first part of the
sample to waste.
2.3.2.2.2 Winter Operation
For outdoor use in freezing temperatures, use special precautions to
prevent the collected sample(s) from freezing. These include:
Place the sampler below the freezing level or in an insulated
box.
When AC is available, use a light bulb or heating tape to
warm sampler. When installation below the freezing level is
not possible and line current is available wrap 1.2 to 1.8 m
(4 to 6 ft.) heat tapes (thermostatically protected 3 C (38°F))
around the sample bottle and the intake lines. Loosely wrap a
large 10 mL plastic trash bag over the heat tape on the intake
lines. Place a large plastic bag over the sampler as loosely
as possible.(7)
Place the line vertically or at such a slope to ensure gravity
drainage back to the source. Even with a back-purge system,
some liquid will remain in the line unless gravity drainage is
provided. If an excess length of tubing exists, cut it off.
Keep all lines as short as possible.
Do not use catalytic burners to prevent freezing since vapors
can affect sample composition. When power is unavailable, use
a well insulated box containing the sampler, a battery and
small light bulb to prevent freezing.
2.3.2.3 Selection of an Automatic Sampler
To choose an automatic sampler, list the desired features needed for a
particular sampling program and select the sampler that best fits the
requirements consistent with the sampling objectives.
The following is a list of features to be considered in selecting an
automatic sampler:
1. Vertical lift
2. Submergence
3. Explosion proof
4. Intake tube: diameter/material
5. Dissolved gases
6. Suspended solids
18
-------
7. Oils and grease and floating material
8, Materials - Organic pollutants
9. Isokinetic sampling
10. Sample type: continuous, composite: time proportional, flow
proportional, and so on.
11. Multiple intakes
12. Multiplexing
13. Dependability
14. Ease of operation
15. Maintenance
16. Availability
2.4 TYPE OF SAMPLE
The type of sample collected depends on the variability of flow,
variability of water or wastewater quality, the accuracy required and the
availability of funds for conducting the sampling and analytical programs.
2.4.1 Grab Sample
A grab sample is defined as an individual discrete sample collected
over a period of time not exceeding 15 minutes. It can be taken manually,
using a pump, scoop, vacuum, or other suitable device. The collection of a
grab sample is appropriate when it is desired to:
1. Characterize water quality at a particular time.
2. Provide information about minimum and maximum concentrations.
3. Allow collection of variable sample volume.
4, Corroborate composite samples.
5. Meet a requirement of a discharge permit.
2.4.2 Composite Sample
A composite sample is defined as a sample formed by mixing discrete
samples taken at periodic points in time or a continuous proportion of the
flow. The number of discrete samples which make up the composite depends
upon the variability of pollutant concentration and flow. A sequential
composite is defined as a series of periodic grab samples each of which is
held in an individual container, then composited to cover a longer time
period. Six methods are used for compositing samples. Table 2.5 lists
those methods with their advantages and disadvantages. Choice of composite
type is dependent on the program and relative advantages and disadvantages
of each composite type.
2.4.3 Selection of Sample Type
Use grab samples when: (12)(13)(14)
1. The stream does not flow continuously such as batch dumps.
2. The water or waste characteristics are relatively constant.
3". The parameters to be analyzed are likely to change with storage such
19
-------
TABLE 2.5 COMPOSITING METHODS
Sample
mode
Compositing
Principle
Advantages
Disadvantages
Comments
Continuous
Continuous
ro
.o
Periodic
Periodic
Constant
pumping rate
Sample pumping
rate proportional
to stream flow
Constant sample
volume, constant
time interval
between samples
Constant sample
volume, time
interval between
samples propor-
tional to stream
flow
Minimal manual Requires large
effort, requires sample capacity;
no flow measure-
ment
may lack represen-
tativeness for
highly variable
flows
Practical but not
widely used
Most representa- Requires accurate Not widely used
tive especially
for highly vari-
able flows;
minimal manual
effort
Minimal instru-
mentation and
manual effort;
requires no
flow measurement
flow measurement
equipment, large
sample volume,
variable pumping
capacity, and
power
May lack represen-
tativeness espe-
cially for highly
variable flows
Minimal manual Requires accurate
effort flow measurement/
reading equipment
Manual compositing
from flow chart
Widely used in both
automatic samplers
and manual sampling
Widely used in
automatic as well
as manual sampling
(Continued)
-------
TABLE 2.5 (Continued)
Sample
Compositing
principle
Advantages
Disadvantages
Comments
Periodic
Periodic
Constant time
interval between
samples, sample
volume propor-
tional to total
stream flow
since last sample
Constant time
interval between
samples, sample
volume propor-
tional to total
stream flow at
time of sampling
Minimal
instrumentation
Minimal
instrumentation
Manual compositing
from flow chart
In absence of
prior information
on the ratio of
minimum to maximum
flow, there is a
chance of collecting
either too small or
too large individual
discrete samples for
a given composite
volume
Manual compositing
from flow chart
In absence of prior
information on the
ratio of minimum to
maximum flow, there
is a chance of
collecting either
too small or too
large individual
discrete samples
for a given com-
posite volume
Not widely used in
automatic samplers
but may be done
manually
Used in automatic
samplers and widely
used as manual
method
-------
as dissolved gases, residual chloHn'e, soluble sulfide, oil and
grease, microbiological parameters, organics, and pH.
4. Information on maximum, minimum or variability is desired.
5. The history of water quality is to be established based on
relatively short time intervals.
6. The spatial parameter variability is to be determined, for example,
the parameter variability throughout the cross section and/or depth
of a stream or large body of water.
Use composite samples when:
1. Determining average concentrations.
2. Calculating mass/unit time loading.
2.4.4 Method of Manual Compositing
When using a constant volume/time proportional compositing method, use
previous flow records to determine an appropriate flow volume increment so a
representative sample is obtained without exceeding the bottle capacity or
supply.
The preparation of the flow rated composite is performed in various ways,
Table 2.6 summarizes the techniques necessary for preparing composites from
time constant/variable volume samples.
2.4.5 Examples of Manual Compositing
Example 2.1 illustrates the method of manual compositing for time
constant/volume proportional to discharge since last sample, when records of
totalized flow are available.
Example 2.2 illustrates the method of manual compositing for time
constant/volume proportional to discharge since last sample, when records of
flow rates are available.
Example 2.3 illustrates the method of manual compositing for time
constant/volume proportional to instantaneous flow rate.
Example 2.4 illustrates the method of manual compositing for the
constant volume/time proportional to equal increment discharge passing the
sampling point, based on the past records of totalized flow.
Example 2.5 illustrates the method of manual compositing for the
constant volume/time proportional to equal increment discharge passing the
sampling point, based on the past records of flow rates.
Example 2.1: Manually preparing a composite sample using the method, time
constant/volume proportional to discharge since last sample.
Given: A 500 ml discrete sample was taken at the end of each hour over
an eight hour shift. A 3,000 ml composite is desired. A recording of
totalized flow is available.
22
-------
TABLE 2.6 MANUAL PREPARATION OF VARIABLE VOLUME COMPOSITE
Type
Time constant/propor-
tional to total
flow
Preparation
Determine volume since
last sample by inte-
gration
Equation
a. - *Ql
1 2AQi
Vc
ai
V_ =
q. =
Q, =
aliquot volume to
be extracted from
ith discrete
sample
composite volume
(known)
flow rate when ith
discrete sample was
taken (from flow
record)
flow volume when ith
discrete sample was
taken
Q. , = flow volume when ith
-1 discrete sample
was taken
Time constant/volume
proportional to
instantaneous flow
Note flow rate at each
time of discrete sample
collection
ai
where: a.
q. =
V =
flow volume or rate
since last sample
(integration)
total flow volume
(estimated)
aliquot volume to be
extracted from ith
discrete sample
flow rate when ith
discrete sample was
taken (from flow
record)
composite sample
volume
n = number of discrete
samples
23
-------
a. (adjusted) =
I / r"/"\/\ /__. _ i
Sample No.
(i)
0
1
2
3
4
5
6
7
8
(liters)
0
858
3,462
8,462
12,347
17,950
21,225
24,600
25,750
ZAQ.
(liters)
-
858
2,604
4,792
4,093
5,603
3,275
3,375
1,150
= 25,750
ai
(ml)
-
100
303
558
477
653
382
393
134
Ea.. = 3,000
a.! (500/max a^)
(ml)
-
77
232
427
365
500
292
301
103
2,297
max a- = 653 ml
Steps:
1. Enter Q. from the record and calculate Q. = Q. - Q. ,
1 V
2. Calculate a. = c (AQ.), where V = 3000 ml
1 EAQ.
i
3. Check to see if maximum a. exceeds discrete sample volume, that is
653 ml > 500 ml. n
4. If it does, adjust aliquot sizes using the relationship:
-«, [d1screte^mpl;vo1ume] - li - »•"
5. Determine the adjusted composite volume from a. (adjusted). This
example illustrates that although desired composite volume was
3,000 ml (V ) because of discrete sample volume size, only 2,297 ml
w
of composite sample can be obtained.
Example 2.2 Manually preparing a composite sample using the method, time
constant/volume proportional to discharge since last sample.
Given: A 500 ml discrete sample was taken at the end of each hour over
an 8 hour shift. A 3,000 ml composite is desired. A recording of flow rate
is available.
24
-------
Sample No.
..(D
0
1
2
3
4
5
6
7
8
11
(1 iters)
sec.
961
2,025
3,700
5,212
6,004
5,018
4,002
3,089
1,847
i
(liters)
sec.
1,483
2,862
4,456
5,608
5,511
4,510
3,546
2,468
ai
(ml)
146
282
439
553
543
444
349
244
a. (adjusted) =
a. (500/max a.)
(ml)
132
255
397
500
491
401
316
221
. = 30,444 zai = 3,000 2,713
Max a. = 553 ml
Steps:
1. Enter q. from record and use trapezoidal rule to calculate
(AQ. = q. + q._,)/2 (another integration scheme could be used if
warranted).
Vr
2. Calculate a. = — - — (AQ.) where V,, = 3,000 ml
1 Z&Q. n C
3. Check to see if maximum a. exceeds discrete sample volume
4. If it does, adjust aliquot sizes using the relationship:
5. Determine the adjusted composite volume from a. (adjusted). This
example illustrates that although desired composite volume was
3,000 ml (V ) because of discrete sample volume size, only 2,713 ml
\*
of composite sample can be obtained.
Example 2.3: Manually preparing a composite sample using the method,
time constant/volume proportional to instantaneous flow rate.
Given: 500 ml discrete samples were taken at hourly intervals over an
25
-------
eight hour shift. A 2,000 ml composite is desired.
recording of flow rate is available.
A
Sample No.
(D
ai
(adjusted) =
x 500/max a.
1
2
3
4
5
6
7
8
(liters)
Sec.
600
1,000
1,700
2,800
1,800
1,400
1,000
700
(ml)
109
182
309
509
327
255
182
127
(ml)
107
179
304
500
321
250
179
125
Zq. = 11,000
Steps:
la. = 2,000
max a. = 509 ml
1,965
1. Enter q. from record and sum.
2. Calculate a. = q. V /q,
I I v» I
3. Check to see if maximum a.. (500/509) = a. (adjusted). This example
illustrates that with an individual discrete sample capacity of 500
ml only 1,965 ml volume of composite sample can be obtained. If it
is desired to collect a composite sample of 3,000 ml volume,
obviously larger sized (750 ml) capacity bottles or greater
sampling frequency will be required for collecting individual
discrete samples.
Example 2.4 Manually preparing a composite sample using the method,
constant volume/time proportional to equal increment discharge.
Given: A 500 mL discrete sample was taken each time an average hourly
flow flowed past the sample point. Sampling period is eight
hours.
In addition, a 500 ml sample was taken at the end of the
sampling period. A composite of 4,000 ml is desired. A
recording of total flow from past record is available.
26
-------
Past Record
Period Q,. (past) AQ1 (past)
ith hour (liters) (liters)
0
1
2
3
4
5
6
7
8
Steps:
1.
2.
0 0
868 868
4,024 3,156
7,616 3,592
11,453 3,837
16,629 5,176
20,377 3,748
22,625 2,248
25,000 2,375
Actual
Q.J (actual) AQ. (actual) a. Sample
(liters) (liters) (ml) No.
0 0
797 797
500 1
3,648 2,851
500 2
8,002 4,354
500 3
11,709 3,707 500 4
500 5
16,056 4,347
500 6
19,763 3,707
500 7
24,321 4,558
500 8
26,650 2,229 264 9
EAQj (past) = 25,000 SAQ.J (actual) = 26,650
Enter Q. from past record and calculate AQ, = Q. - Q.
Determine the number of samples from the overall sampling period.
On the basis of the number of samples required for the overall
sampling period, P, determine the average flow from the past
records for the time interval, T, between the successive discrete
samples. In our case, the number of samples for the sampling
period = 8. Overall sampling period, P = 8 hours.
Time interval , T = 8 hours = 1 hour
Average flow for the time
from past = n (past)
P
8
interval between successive samples
25,000 = 3,125 L.
8
3. Aliquot size a. = 500 ml
4. Collect each discrete sample every time 3,125 L passes the sampling
point; and an additional one 500 ml sample aliquot at the end of the
sampling period.
5. Record the actual flow.
27
-------
6. Note the total flow for the sampling period. In our case it is
EAQ,. (actual) = 26,650 L.
7. Calculate the difference between ZAQ. (actual) and ZAQ. (past)
which is 26,650 - 25,000 = 1,650 L. This is the flow which passes
the sampling point after taking the last sample for equal
incremental discharge, up to the end of sampling. This flow is
sampled by the sample taken at the end of the sampling period.
8. Compute the representative aliquot required for the unbalanced flow
in step 7 in proportion to the equal increment flow.
Required aliquot volume = ^ (actual) -
equal increment discharge volume i
26.650 L - 25.000 L ,cnn . % ,c. ,
= - ~ -ipc I - (500 mL) = 264 mL
9. Composite volume: = £a. = 8 aliquots of 500 ml + 264 ml from the
aliquot taken at the end of the sampling period for a total of
4,264 mL.
Example 2.5 Manually preparing a composite sample for constant volume/time
proportional to equal increment discharge.
Given; A 500 ml discrete sample was taken each time an average hourly
flow flowed past the sample point. Sampling period is eight hours.
In addition, a 500 ml sample was taken at the end of the sampling period,
A composite of 4,000 ml is desired. A recording of instantaneous flow
rate from past records is available.
28
-------
Period Q. (past) AQ. (past) Q. (actual) AQ. (actual) a. Sample
1th hr. (liters) (liters) (liters) (liters) (ml) No.
0
1
2
3
4
5 '
6
7
8
Steps:
1.
2.
40 - 30
50
60 50
80
100 110
110
120 110
140
160 150
160
160 180
155
150 180
130
110 110
105
100 90
XAQ.. (past) = 930 ZAQ
Enter Q. from past record and use trapezoid
AQ,- = (Q,- + Q,- -,)/2 (another intergration s
warranted).
Determine the number of samples for the ove
the basis of number of samples required for
period, P, determine the average flow from
time interval, T, between the successive di
case the number of samples for the sampling
sampling period, P = 8 hours
T- • i IT- 8 hours
Average flow for the time interval between
past records = ZAQ. = 93Q = U6
40
80 500
110 500
130 500
500
165 500
500
180
500
145
500
100
86
1
2
3
4
5
6
7
8
9
. (actual) = 950
al rules to calculate
cheme could be used if
rail sampling period. On
the overall sampling
the past records for the
screte samples. In our
period = 8. Overall
1 hour.
successive samples from
L
3. Aliquot size a. = 500 ml.
4. Collect a discrete sample each time 116 liters passes the sampling
point and one additional aliquot of 500 ml at the end of the sampling
period.
5. Record the actual flows per unit of time interval selected. For
example; hours, minutes, days.
29
-------
6. Calculate the total actual flow for the the sampling period. In our
case it is EAQ. (actual) = 950. L.
7. Calculate the difference between ZAQ. (actual) and ZAQ. (past)
which is 950-930 = 20 L. This is the flow which passes the
sampling point after taking the last sample for equal incremental
discharge, up to the end of the sampling period.
8. Compute the representative aliquot required for the unbalanced flow
determined in step 7 in proportion to the equal increments.
. (actual) - EAQ.(past)
Required aliquot volume = _ (a.') =
equal increment discharge
(20 L)(500 ml) volume
116 L = 86 mL
9. Composite volume = Za. =8 aliquots of 500 mL + 86 mL from the
aliquot taken at the end of the sampling period = 4,086 mL.
2.5 PLANNING A SAMPLING PROGRAM
The following considerations can help to plan an appropriate sampling
program. The planning process can be divided into four stages: preliminary
plan, evaluation of preliminary plan, final plan, and program evaluation.
2.5.1 Preliminary Plan
In this stage, emphasis is on the collection of preliminary information
on the entity to be sampled, the sampling sites and the flow
characteristics. This information may be available from records of previous
surveys. Where such information is not available, carry out a
reconnaissance survey to become thoroughly familiar with actual site
conditions. Table 2.7 shows the type of information needed in most cases.
Collect the appropriate information for Table 2.7 and based on this
information, draw up a preliminary sampling plan. Delineate preliminary
sampling objectives and details of the plan such as anticipated parameters,
sample type, sample size, and frequency, specified. Record this information
in a tabular form similar to Table 2.8.
Make an estimate of the resources (manpower and equipment) needed for the
sampling program. Table 2.9 illustrates one form for keeping records of
available resources and estimated needs of a sampling program. Include into
the preliminary sampling plan, sample preservation and chain of custody
procedures.
3"0
-------
TABLE 2.7 PRESURVEY INFORMATION
Entity
Treatment Plant ( ) 1.
Process Details
Industry ( ) 2.
River ( ) 3.
Estuary ( ) 4.
Sewer ( ) 5.
Water Mains () 6.
Plans:
Sewer maps
Water 1 ine net-
work maps
River and tribu-
tary maps
Treatment plant maps
Estuary zone maps
Channel
Width
Depth
Pipe
Diameter
Material
P = pipe flow C =
Yes No Waste sources
( ) ( ) 1.
( ) ( ) 2.
( ) ( ) 3.
( ) ( ) 4.
( ) ( ) 5.
Flow Variability
Hourly Max
Hourly Min
Hourly Average
Daily Max
Daily Min
Dally Average
open channel flow
Flows
P/C
P/C
P/C
P/C
P/C
Manholes ( )
other
Diameter
or width
Depth
(continued)
31
-------
TABLE 2.7 (Continued)
Topography
Level ( )
Slopes ( }
Vegetation ( )
Swamp ( )
Other ( )
Specify
Sampling Sites
Distance:
Near ( )
Remote ( )
Physical Charac- Safety
ten* sties of Flow
Odor
Temperature
Oil & Grease
Clear ( )
Turbid ( )
Suspended Sol
concentration
Numbers :
Few ( )
Many ( }
Steep banks
Soft grounds
Gases
specify
Security
( ) Fence (
( ) Open (
( ) Guarded (
)
)
)
Lighted ( }
Stream Currents
ids Turbulent
Sluggish
Accessibility:
Road ( )
Bridge ( )
Other ( )
Specify
Other (
( ) Specify
( }
Convenience;
Sheltered ( )
Power available (
Other ( }
Specify
•
Additional Information
32
-------
TABLE 2.8 DETAILS OF SAMPLING
'araaetert of
interest
Staple
Saapl*
Frequency
Suabcr
of
Sanples
Field or
Lab
Volune
Preservation
Holding
Tine*
Methods
Chain of
. Custody
Procedure
Remarks
-------
TABLE 2.9 MANPOWER AND EQUIPMENT FOR A SAMPLING PROGRAM
Manpower; Available Needed
Sampling Program Coordinator
Quality Assurance Coordinator
Laboratory Custodian
Field Sampling Crew Chief
Field Laboratory Crew
Shipment Truck Driver
Others
Equi pment:
Automatics Samplers
Type
Manual Samplers:
Type
Flow Meters: 'Type and Size
(Continued)
34
-------
TABLE 2.9,-(Continued)
Portable Weirs:
Portable Flumes:
Sounding Equipment:
Wading rods
Cable lines
Sounding rods
Sounding Weight:
Boats:
Trucks:
Available
Needed
(Continued)
35
-------
TABLE 2.9 (Continued)
Available Needed
Field Laboratory:
Other Equipment:
2.5.2 Evaluation of Preliminary Plan
Circulate the preliminary sampling plan among other divisions
(laboratory, field personnel, and quality assurance branch) connected with
the sampling program for their considerations and further deliberations
before drawing up a final sampling program.
2.5.3 Final Plan
Base the final sampling plan on the preliminary plan and subsequent
deliberations and coordination with the personnel involved. Spell out the
final plan in detail including: objectives, sampling locations, number and
frequency of samples, sample types, quality assurance samples (field spikes,
replicates, etc.), preservation and chain of custody procedures, designation
of authorities, field procedures and other pertinent information so that the
sampling plan can be executed in an efficient and well coordinated manner.
Pre-sampling briefing should be a key element in any sampling program.
2.5.4 Program Evaluation
Evaluate the entire program after the samples are collected and
analyzed to determine the effectiveness of the final plan and to avoid
future pitfalls and problems. The performance evaluation should enhance the
efficiency of the program and quality of the data generated from a sampling
program.
36
-------
2.6 FIELD PROCEDURES
The heart of the sampling program is field operations. If proper
precautions and care are not exercised in the field procedures, the entire
sampling program will become meaningless despite adequate planning,
analytical facilities, and personnel. The key to the success of a field
sampling program lies in good housekeeping, collection of representative
samples, proper handling and preservation of samples, and appropriate chain
of custody procedures.
2.6.1 Good Housekeeping
1. Compose written instructions on field sampling procedures.
2. Prior to use, check sampling equipment to insure good operating
conditions and cleanliness. Keep the equipment ready to be used.
After the sampling has been completed, clean the equipment and keep
it in neat environments. Follow manufacturer's specifications in
carrying out routine maintenance of the equipment.
3. Check primary (e.g. flume) and secondary (e.g. Recorder/transmitter)
devices for the following:
a. Locations
. At the appropriate place as defined in sampling program.
. Upstream and downstream conditions meet the requirement of
specific installation of primary and secondary devices.
b. Dimensions of primary devices such as flumes, weirs, and still
wells to be sure they are within tolerance limits.
c. General conditions of channel, primary and secondary devices
and stilling wells. Note any unusual wear, debris in channel
or distortion of chart paper.
d. Calibration of primary and secondary devices before actual
measurements of flow are taken.
4. Check all sample bottles to avoid contamination. Clean the bottles
as indicated in Section 17.2.5 and 17.2.6. If this cannot be done,
do not collect the sample.
5. In the laboratory, clean the sample intake tubing by flushing with
hot water and then rinsing with distilled water. In the field,
rinse several times with sample water.
6. Maintain record of breakdowns in the sampling operations, the
problems encountered with different equipment and how they were
resolved. This information indicates the reliability of the
equipment, the problem areas that need to be brought to the
manufacturer's attention, and considerations for future procure-
ments.
7. Hold training sessions for field sampling teams.
37
-------
2.6.2Guidelines for Representative Sample
To obtain representative samples, follow these guidelines;
1. Collect the sample where water is well mixed, that is near a
Parshall flume or at a point of hydraulic turbulence such as
downstream of a hydraulic jump. Certain types of weirs and flumes
tend to enhance the settling of solids upstream and accumulate
floating solids and oil downstream, therefore such locations should
be avoided as a sample source. For low level turbulence,
mechanical or air mixing should be used to induce turbulence except
when dissolved gases or volatile materials are being sampled.
2. Collect the sample in the center of the channel at 0.4 to 0.6 depth
from the bottom where the velocity of flow is average or higher
than average and chances of solids settling is minimum. This
depth avoids bottom bed loads and top floating materials such as
oils and grease.
3. In a wide channel, divide the channel cross section into different
vertical sections so that 'each section is equal width. Take a
representative sample in each vertical section.
4. In a deep stream or lake, collect the samples at different depths.
In those cases of.wide and deep streams the samples can be
composited or analyzed individually depending upon the program
objective.
5. When manual sampling with jars, place the mouth of the collecting
container below the water surface and facing flow to avoid an
excess of floating material. Keep the hand away from the mouth of
the jar as far as possible.
7. Additional guidelines for manual sampling:
Sample facing upstream to avoid contamination.
Force sampling vessel through the entire cross section of the
stream wherever possible.
Drop an inverted bucket and jerk line just before impact with
the water surface.
Be certain that the sampler closes and opens at the proper time
when sampling with a depth integrating sampler; with a point
sampler, be certain that sampler opens at a proper depth. If a
doubt exists, discard the sample and re-sample.
8. When sampling, it is necessary to fill the bottles completely if the
samples are to be analyzed for volatile organics, CL, CO-, NH.,, HpS.
free chlorine, pH, hardness, SCL. NH,. FE , oil and grease,
acidity or alkalinity. When sampling for bacteria or suspended
solids, it is necessary to leave an airspace in the sample
container to allow mixing before subsampling.
9. Collect sufficient volume to allow duplicate analyses and quality
assurance testing (split or spiked samples). The required sample
volume is a summation of that required for each parameter of
interest. Refer to USEPA's Methods for Chemical Analyses for Water
38
-------
and Wastewater, 1979, EPA 600/4-79-0202 for the volume required for
analysis of a specific parameter (8), or the laboratory director for
minimum volumes to be collected.
10. Maintain an up-to-date log book which notes possible interferences,
environmental conditions and problem areas.
11. Since mathematical relationship between volumetric flow and height
(or depth) of flow is nonlinear, composite flow proportional samples
in relation to the total volume of flow as opposed to gauge height
or raw measurement of a secondary device.
12. If samples are taken from a closed conduit via a valve or faucet
arrangement, allow sufficient flushing time to insure that the
sample is representative of the supply, taking into account the
diameter, length of the pipe to be flushed and the velocity of the
flow.
2.6.3 Sample Preservation, Handling and Chain of Custody Procedures
When immediate analysis of the collected sample is not possible, take
precautions so that the sample characteristics are not altered. Follow these
guidelines for sample handling and preservation:
1. Minimize the number of people handling the sample.
2. Follow the guidelines given in chapters 15 and 17 on chain of
custody procedures and sample handling.
3. Store the sample in a manner which insures that the parameters to be
analyzed are not altered, and use the preservation methods and
holding times pertinent to the parameters shown in chapter 17.
4. Insure that the container material does not interfere with the
analysis of the specific parameters. Refer to EPA's Methods for
Chemical Analyses for Water and Wastewaters, 1979.
EPA 600/4-79-020.(8)
2.6.4 Field Analysis and Procedures
The sampling program should specify the various analyses to be
performed in the field and the corresponding analytical methods. Field
laboratories must also have standard procedures and methods for handling and
analyzing samples such that identification, integrity and representativeness
of the samples are maintained at all times.
2.7 REFERENCES
1. Water Monitoring Task Force. R.L. Crim, editor, Model State Water
Monitoring Program. U.S. Environmental Protection Agency, Office of
Water and Hazardous Materials, Washington, D.C., EPA-440/9-74-002.
2. Black, H.H. Procedures for Sampling and Measuring Industrial Wastes.
Sewage and Industrial Wastes, 24, pp. 45-65, January 1952.
39
-------
3. Lauch, R.P. A Survey of Commercially Available Automatic Wastewater
Samplers. Environmental Monitoring and Support Laboratory, Office of
Research and Development, U.S. Environmental Protection agency,
Cincinnati, Ohio. Available through National Technical Information
Service, Springfield, Virginia 21161. EPA 600/4-76-051, September
1976, PB 241085/AS.
4. Shelley, P.E. and G.A. Kirkpatrick. An assessment of Automatic Sewer
Flow Sample. Prepared for the Office of Research and Monitoring, U.S.
Environmental Protection Agency, Washington, D.C. 20460, EPA R2-76-261
June 1973.
5. Shelley, P.E. and G.A. Kirkpatrick. An Assessment of Automatic Sewer
Flow Sampler. Prepared for the Office of Research and Monitoring, U.S.
Environmental Protection Agency, EPA 600/2-76-065 Washington, D.C.,
December 1975.
6. Shelley, P.E. Design and Testing of a Prototype Automatic Sewer
Sampling System. Prepared for the Office of Research and Monitoring,
U.S. Environmental Protection Agency, EPA 6001/2-76-006, Washington,
D.C., March 1976.
7. Harris, E.J. and W.J. Keffer. Wastewater Sampling Methodologies and
Flow Measurement Techniques. USEPA Region VII, EPA 907/9-74-005,
Kansas City, Missouri, June 1974.
8. Segar. E.A. amd A.A. Berberian. Contamination by Oceanographic
Samplers. Analytical Methods in Oceanography, American Chemical
Society, 1975.
9. U.S. Environmental Protection Agency. National Field Investigation
Center, Denver. Comparison of Manual (Grab) and Vacuum Type Automatic
Sampling Techniques on an Individual and Composite Basis. EPA
330/1-74-001.
i
10. Metcalf and Eddy Inc. Wastewater Engineering: Collection, Treatment,
Disposal. New York, McGraw-Hill Book Company, 1972, p. 710.
11. Water Measurement Manual. U.S. Bureau of Reclamation. U.S. Government
Printing Office, Washington, D.C. 1967. p. 16.
12. Wander, W.E. Jr. Water Pollution Control Federation Highlights, 10 D-l,
March 1973.
13. Tarazi, D.S. et aj. Comparison of Wastewater Sampling Techniques
J.W.P.C.F. 42_ pp. 708-732 May 1970.
14. Associated Water and Air Resource Engineers, Inc. Handbook for
Industrial Wastewater Monitoring. U.S. Environmental Protection
Agency, Technology Transfer, August 1973.
40
-------
CHAPTER 3
FLOW MEASUREMENTS
Methods of flow measurements are presented in this section. More
detailed information can be found in a number of noteworthy publications
such as ASME Monograph of Fluid Meters, (1) USDI Bureau of Reclamation's
Water Measurement Manual, (2) publications of Techniques of Water Resource
Investigations, by USDI, U.S. Geological Survey, as well as texts or
manuals on hydraulics. (3-13)
Inaccurate flow measurements will lead to inaccurate flow proportional
composite samples which in turn will lead to inaccurate results. Therefore,
care must be exercised in selecting a flow measurement site. The ideal site
gives desired flow measurement to meet program objectives, provides ease of
operation and accessibility; personnel and equipment safety, and freedom
from vandalism.
A flow measurement system usually consists of a primary device having
some type of interaction with the fluid and a secondary device which
translates this interaction into a desired readout or recording.(5)
Flow measurement methods can be broadly grouped into four categories:
1. Closed conduit flow measurement
2. Flow measurement for pipes discharging to atmosphere
3. Open channel flow measurement
4. Miscellaneous methods of flow measurement
Table 3.1 lists different methods of flow measurement and their
application to various types of problems.
3.1 CLOSED CONDUIT FLOW MEASUREMENT
Some of the most commonly used devices and methods for closed conduit
primary flow measurement are described briefly in this section.
3.1.1 Venturi Meter
The Venturi meter is one of the most accurate primary devices for
measuring flow rates in pipes. Basically the Venturi meter is a pipe segment
consisting of an inlet section (a converging section), a throat and an
outlet section (a diverging section) as illustrated in Figure 3.1. A
41
-------
ro
TABLE 3.1 METHODS OF FLOW MEASUREMENT AND THEIR APPLICATION
TO VARIOUS TYPES OF PROBLEMS (14)(15)
Device or
Method
Mathematical
formula
Water meters
Bucket &
stopwatch
tump capa-
city i oper-
ation
Floating
objects
Dyes
Salt
Dilution
Orifice
meter
Venturi
tubes
Flow Range
Measurement
Snail to
large
Small to
large
Small
Small to
large
Small co
medium
Small to
medium
Small co
med lum
Small td
large
Snail to
large
Applicable
to Type of Ease of
Water and Cost Installation
Wastewater
All Low NA
All Low Fair
All Low Fair
All LOB Fair
All Low NA
Al 1 Low NA
All Lou NA
Clean Medium Fair
water
Clean High Fair
uater,
limited
for waters
with sus-
pended solids
Accuracy*
of Data
Fair
Excellent
Good
Good
Good
Fairly
good
Fair
Excellent
1/4 - 2%
Excellent
1/4 - 3%
Pressure Volumetric Flou
Loss Thru Flou Rate Transmitter
the Device Detector Sensor Available Application
NA NA NA NA Open channel.
pipe flow
Medium NA NA NA Pipe flou
HA HA NA NA Small pipes with
ends or joints
can be discon
nected
NA NA NA NA Lines where water
is being pumped
NA NA NA NA Open channels
NA NA NA NA Pipe flou and
open channels
NA NA NA NA Pipe flou and
open channels
High Yes Yes Yes Pipe flou
Minimal Yes Yes Yes Pipe flou
* Assumes proper installation and roalntenace of primary device
(continued)
-------
TABLE 3.1 (Continued)
•*»
CO
Device or
Method
Flow nozzle
Pitot tubes
Elbow taps
Rotameters
Magnet ic
flow-
tnetcrs
Heirs
Flumes
Acoust ic
flow-
meters
Flow Range
Measurement
Snail to
large
Sawll to
medium
Small to
medium
Small to
medium
Small to
large
Small to
large
"Small to
large
Small to
large
Applicable
to Type of . Ease of
Water and Cost Installation
Uastewater
Clean water Medium Fair
Clean water Medium Fair
Clean water, Medlun Fair
limited for
water with
suspended
solids
Clean water, Medium Fair
limited for
water with
suspended
solids
All High Fair
All Medium Difficult
All High Difficult
All High Fair
Accuracy*
of Data
Excellent
1/4 - 3X
Good
2 - 5%
Fair
Excellent
Excellent
1/2 - 1%
Good to
Excellent
2 - 5%
Good to
Excellent
2-5%
Excellent
IX
Pressure Volumetric Flow
Loss Thru Flow Rate Transmitter
the Device Detector Sensor Available Application
Minimal Yes Yes Yes Pipe flow
Minimal Yea Yes Yes Pipe flow
fione Yes Yes Yes Pipe flow
Average Yes Yes Yes Pipe flow
None Yes Yes Yes Pipe flow
Minimal Yes Yes t'es Open channel
flow
Minimal Yes YOB Yes Open channel
flow
None Yes Yes Yes Pipe and open
channel flow
-------
THROAT
INLET SECTION SECTION
OUTLET SECTION
HIGH
PRESSUR
TAP
LOW PRESSURE TAP
THROAT DIA.
Figure 3.1 Venturi Meter (5)
10
10
10
« 9
<4-l
o 9
w Q
-------
portion of potential energy transferred to kinetic energy in the throat
section causes a pressure differential which is proportional to the flow
rate. One of the advantages of the Venturi meter is that it has low
pressure loss.
Manufacturers of Venturi meters routinely size their meters for a
specific use. The accuracy of the Venturi meter is affected by changes in
density, temperature, pressure, viscosity and pulsating flow of the fluid.
To obtain accurate flow measurements:
1. Install Venturi meter as per manufacturer's instructions.
2. Install Venturi meter downstream from a straight and uniform section
of pipe, at least 5-20 diameters, depending upon the ratio of pipe
diameter to throat diameter and whether straightening vanes are
installed upstream. Installation of straightening vanes upstream
will reduce the upstream piping.
3. For wastewater application, insure that the pressure measuring taps
are not plugged.
4. Calibrate Venturi meter in place either by volumetric method
(Section 3.4.5) or comparative salt dilution method (Section
3.3.1.3) to either check the manufacturer's calibration curve or to
develop a new calibration curve.(16)
The formula for calculating the flow in a Venturi meter is as follows:
Q = CAK /TT
Where:
Q = volume of water, in cubic meters per second (cubic feet per second)
C = discharge coefficient, approximately 0.98. C varies with Reynold's
number, meter surfaces and installation.
- d 2
A = Throat area, in square meters (feet) . 2
H = H, - H£, differential head, in meters (feet) of water.
H, = pressure head at center of pipe at inlet section, in meters
(feet) of water.
H9 = pressure head at throat, in meters (feet) of water
K =\l l-faY (Obtain values of K from Figure 3.2)
Where:
2 2
g = acceleration due to gravity, 9.82 m per sec (32.2 feet per sec )
45
-------
dp = throat diameter, in meters (feet).
- d, = diameter of inlet pipe, in meters (feet).
3.1.2 Flow Tubes
Included in the class of flow tubes are Dall tube, "Lo-Loss" tube, and
gentle tube.
The Dall tube is a Venturi type device, in which the differential
pressure results from the streamlined bending as well as the velocity head
(Figure 3.3).
The Dall tube is almost as accurate and has a higher head recovery than
the standard Venturi, being one of the lowest permanent head loss devices
known. It is more sensitive to system disturbances than the Venturi, and
straight upstream pipe runs of 40 pipe diameters or more may be required.
Installation of straightening vanes upstream will reduce the upstream piping
requirement. Although somewhat cheaper than the Venturi, the Dal! tube must
still be considered expensive. It'is much shorter than either long or short
tube Venturi meters. Calibration and other installation guidelines for
Venturi meters also apply to flow tubes.
3.1.3 Flow Nozzle
A flow nozzle is a measuring device with characteristics between the
Venturi meter and an orifice as far as head loss and cost are concerned
(Figure 3.4). It operates on the same principles as the Venturi meter. The
flow formula for the Venturi tube is also applicable to the nozzle. Flow
nozzles can be used in wastewater flows containing moderate amounts of
suspended solids. Each manufacturer uses a slightly different nozzle
ranging from a Venturi to an orifice. Accuracy, installation and
calibration guidelines for Venturi meters also apply to flow nozzles.
3.1.4 Orifice Meter
An orifice meter is relatively inexpensive, easy to install, and a
reliable flow measuring device. Basically, an orifice is an obstacle placed
in the path of flow in a pipe.
The principles of operation of an orifice are the same as for nozzles
and Venturi meters since the stream lines of the flow and the basic formula
are similar to those of a Venturi meter.
Q = CAK/TT (Same as Venturi tube)
The coefficient, C, is illustrated for several forms of orifices in
Figure 3.5 and tabulated in Table 3.2. The nominal coefficients are
applicable for relatively large orifices operating under comparatively large
heads of water.
The orifice measures flow over a wide range by varying the throat width.
Orifice plates are the most sensitive of all the differential pressure
46
-------
FLOW
LOW PRESSURE TAP
HIGH PRESSURE TAP
Figure 3.3 Dall Flow Tube (5)
HIGH
PRESSURE TAP
LOW PRESSURE TAP
ENTRANCE
CONE
— THROAT
Figure 3.4 Typical Flow Nozzle Installation (5)
47
-------
ORIFICES AND THEIR NOMINAL COEFFICIENTS
HARP EDGED
ROUNDED
SHORT TUBE
BORDA
0.61 to
0.71
0.98
0.80
0,51
Figure 3.5 Coefficients of Several Types of Orifices (13)
100
I I I I T
THIN PLATE ORIFICE
STANDARD VENTURI
LONG FORM.VENTURI
P/MLO - LOSS TUB
0
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Diameter Ratio
Figure 3.6 Relative Permanent Loss of Primary Elements (3)
48
-------
TABLE 3.2 DISCHARGE COEFFICIENTS FOR PRESSURE TAP. ORIFICES (13.)
Orifice Diameter (d2) 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Pipe Diameter /d,*
Coefficient C — 0.61 0.61 0.61 0.61 0.61 0.64 0.71
devices to effects of upstream disturbances. It is not uncommon to need 40
to 60 pipe diameters of straight run upstream of the installation. (3) The
main disadvantage to the orifice is the large permanent pressure loss that
occurs across the section. The other disadvantage of the orifice is
susceptibility to clogging in waters with high suspended solids
concentration. The relative permanent pressure losses for the Venturi tube,
the nozzle, P/M Lo-Loss tube (Badger Meter Inc.) and the orifice are
compared in Figure 3.6.
3.1.5 Elbow Meters
Flow acceleration induced in a fluid going around a bend such as an
elbow produces a differential pressure that can be used to indicate flow.
The pressure on the outside of an elbow is greater than on the inside, and
the pressure taps located midway around the bend at about 45 degrees from
either flange can be connected to a suitable secondary element for
indicating or recording.
For accurate flow measurement, straight pipe runs of at least 20 pipe
diameters should be provided both upstream and downstream of the elbow.
accuracies of 3 to 10% are generally encountered although accuracies of 1 to
2% or better in some cases may be achieved if calibrated in place. (5)
3.1.6 Pitot Tube
A schematic diagram of a simple Pitot tube is shown in Figure 3.7. In
operation, the velocity of the flow is calculated from the difference in
head measured on the manometer. Pitot tubes measure the flow velocity at a
point.
The basic formula is:
V = velocity at a point (at center of pipe V = V )
X A C
C = coefficient of discharge obtained by calibration
V = velocity at the center
Vm = mean velocity - 0.83 VG
H = measured pressure differential (P~ - Pi in Figure 3.7)
49
-------
/ /// //.////////// tf/lift f / f f i / / / /TV ////././_//_/// / / / ////If ifl
IP •
cl
Vl
t jf.
"
V
L.
j
-7
PJ
i
*^x
-^
" d
r
•..
=
•^
— _.
, P2
Figure 3 ,.7 Pitot Tube Schematic
Annular
Orifice
Jloat
Figure 3.8 Rotameter
50
-------
Q = discharge volume
A = area of cross section of stream at the point of measurement
Commercially available Pitot tubes consist of a combined peizometer and
total head meter. Pitot tube measurements should be made in a straight
section upstream and free of valves, tees, elbows, and other fittings with a
minimum distance of 15 to 50 times the pipe diameter. When a straight
section is not possible, a velocity profile should be obtained
experimentally to determine the point of mean velocity. Pitot tubes are not
practical for use with liquids with large amounts of suspended solids
because of the possibility of plugging. In large pipes, the Pitot tube is
one of the most economical means of measuring flows, except for low
velocities.
3.1.7 Rotameters
Rotameters (Figure 3.8) are tapered tubes in which the fluid flows
vertically upward. A metal float in the tube comes to equilibrium at a point
where the annular flow area is such that the velocity increase has produced
the necessary pressure difference. Rotameters are simple, inexpensive and
accurate devices for measuring relatively small rates of flow of clear,
clean liquids (no suspended solids). For this reason they are used to
measure the water rate into individual processing steps in manufacturing
operations. To maintain accuracy in a rotameter, it is essential that both
the tube and float be kept clean.
3.1.8 Electromagnetic Flowmeter
The electromagnetic flowmeter operates according to Faraday's Law of
Induction: the voltage induced by a conductor moving at right angles
through a magnetic field will be proportional to the velocity of the
conductor through the field. In the electromagnetic flowmeter, the
conductor is the liquid stream to be measured and the field is produced by a
set of electromagnetic coils. A typical electromagnetic flowmeter is shown
in Figure 3.9. The induced voltage is subsequently transmitted to a
converter for signal conditioning.
Electromagnetic flowmeters are used in full pipes and have many
advantages: accuracies of ± 1 percent, a wide flow measurement range, a
negligible pressure loss, no moving parts, and rapid response time.
However, they are expensive and build-up of grease deposits or pitting by
abrasive wastewaters can cause error. Regular checking and cleaning of the
electrodes are necessary.
3.1.9 Acoustic Flowmeters
Acoustic flowmeters, commonly used in water and wastewater flow
measurements, operate on the basis of travel time difference method. In the
travel time difference method, sound waves are transmitted diagonally across
51
-------
MAGNETIC
COIL
60 CYCLE A-C
Figure 3.9 Electromagnetic Flowmeter
.-TRANSDUCER A
Figure 3.10 Principle of Acoustic Flowmeter (6)
52
-------
the pipe or channel in opposite directions relative to the flow and the
difference in travel times upstream and downstream are measured (Figure
3.10).
Flowmeters must be installed according to manufacturer's instructions
and calibrated in place to eliminate errors due to uncertainties in
non-laminar flow profile, and due to acoustic short circuit (where
transducers are mounted externally on the pipe). According to the
manufacturers, an accuracy of one percent of full scale is achievable.
3.2 FLOW FROM PIPES DISCHARGING TO THE ATMOSPHERE
The common techniques for measuring the flow from open ended pipes
either full or partly full are listed below. The orifice and flow nozzle
techniques which are not listed here are described in Sections 3,1.3 and
3.1.4 respectively. Rotating element meters are described in Section
3.3.1.1.
3.2.1 Pipes Flowing Full
1. Vertical open end pipe (7)
a. Weir flow: Q = 0.249D 1-20H1'24 (Figure S.lla)
b. Jet flow: Q = 0.171D 2-025H°'53 (Figure 3. lib)
3
where: Q = flow, m /s
D = internal pipe diameter, meters
H = distance from pipe outlet to top of crest,
meters
2. Horizontal or sloped open end
Q = 2.264 x 1Q~4 % (Figure 3. lie and e)
3 ^
where: Q = flow, m /s
A = cross sectional area of the pipe, square meters
X = distance from the end of the pipe to where Y is
measured, meters
Y = vertical distance measured at a distance X from
the pipe end, meters
3. Purdue Method (6)
It is similar to the trajectory method for the horizontal open ended
53
-------
en
a. Weir Flow b. Jet Flow
Vertical Open-End Pipe
i
c. Horizontal Pipe Flowing
Full
( I
0 i
t
I
1. Horizontal P
„ X „
\\N\\
ipe \\\\\
r'
Y
_L
Partially Full
e. Discharge From Open-End Pipe Xj\ Y
"1
•^mj»4~\
*l
.•SSS?S-TK«
Open End
-at least 6d-
->
Hose
6d
\\
f. California Pipe Method
Figure 3.11 Techniques for Pipes Discharging to the Atmosphere (7)
-------
pipe, described in (2) above. To obtain the flow, the trajectory
measurements X and Y, Figure 3.12, are used with curves derived from Purdue
University experiments on pipes 0.05 to 0.15 m (2 to 6 inches) in diameter.
Figure 3.13 gives discharge data for Purdue trajectory method for X = 0, 6,
12, and 18 Inches and inside pipe diameters of two, four and six inches.
3.2.2 Pipes Flowing Partially Full
1. Horizontal or sloped open end (7)
Q- 2.264 x^O-4AX(CF) (F1gure 3.nd)
ft
where:
Q = flow, m /s
A = cross sectional area of the pipe, square meters
X = distance from end of pipe to where Y is measured, meters
Y = vertical distance measured at a distance X from the pipe end,
meters
CF = correction factors which are given in Table 3.3
2. Purdue Method (6)
This method can be used for partially full pipe discharging to
atmosphere using the curves (Figure 3.12) for X = 0, provided the
brink depth is less than 0.8 diameter.
3. California Pipe Method (6)(7)
Q = TW, (Figure 3.11f)
where:
3
Q = flow, m /s
T = 8.69 (1 - *) l'8B
W - d2'48
d = Inside pipe diameter, meters
a = Inside distance from the top of pipe to water surface, meters
The empirical equation is derived from experiments performed on steel
pipes from 3 to 10 inches in diameter and it is imperative that a/d
should be less than 0.5 and the straight pipe length to the end of
pipe should be at least 6d.
55
-------
Figure 3,12 Trajectory Measurements, Purdue Method
_ 1 1 I 1
-
-
1
Inside
1 '
diameter =
X = 18 inches
" X = 12 inches
iiii
i
i i
V '\
\ '
\
2in~^
i i i i
1
^
\
•—-A
X,
•-.
.
\' v
\ \
\ \
4 1n-<3t--
^\
\
i i
V '\'
\ >
\
•A N
\
V
X
\,M,
1 _
-
\
""S
k \
V-
\,
10 20
50 100 200
500 1000 2000
Inside diameter = 2 in
50 100 200 500 1000 2000
Flow, gallons per minute
Figure 3.13 Discharge Data, Purdue Method
56
-------
TABLE 3.3 CORRECTION FACTORS FOR DISCHARGE FROM PIPES
PARTLY FULL (7). HORIZONTAL OR SLOPED END
R*
0.10
0.11
0.12
0.13
0.14
0.15
0.16
0.17
0.18
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
0.32
0.33
0.34
0.35
0.36
Correction
Factor
0.948
0.939
0.931
0.922
0.914
0.905
0.896
0.886
0.877
0.867
0.858
0.847
0.837
0.826
0.816
0.805
0.793
0.782
0.770
0.759
0.747
0.735
0.723
0.712
0.700
0.688
0.676
R*
0.37
0.38
0.39
0.40
0.41
0.42
0.43
0.44
0.45
0.46
0.47
0.48
0.49
0.50
0.51
0.52
0.53
0.54
0.55
0.56
0.57
0.58
0.59
0.60
0.61
0.62
0.63
Correction
Factor
0.664
0.651
0.639
0.627
0.614
0.602
0.589
0.577
0.564
0.551
0.538
0.526
0.513
0.500
0.487
0.474
0.464
0.449
0.436
0.423
0.411
0.398
0.386
0.373
0.361
0.349
0.336
R*
0.64
0.65
0.66
0.67
0.68
0.69
0.70
0.71
0.72
0.73
0.74
0.75
0.76
0.77
0.78
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.86
0.87
0.88
0.89
0.90
Correction
Factor
0.324
0.312
0.300
0.288
0.276
0.265
0.253
0.241
0.230
0.218
0.207
0.195
0.184
0.174
0.163
0.153
0.142
0.133
0.123
0.114
0.104
0.095
0.086
0.078
0.069
0.061
0.052
* R = F/D (Free board 1n pipe/inside pipe diameter), (see Figure 3.lid)
3.3 OPEN CHANNEL FLOW MEASUREMENTS
Methods of flow measurements for open channels can be applied to flows
in non-pressure sewers since both have the same hydraulic characteristics.
Different methods in use can be grouped into the following broad
classification:
57
-------
1. Velocity Methods
2. Head-Discharge Methods
3. Miscellaneous Techniques
3.3.1 Velocity Methods
Velocity flow can be measured using drag body current meters,
eddy-shedding current meter, acoustic velocity meter, doppler-shift velocity
meter, electromagnetic current meter, and rotating element current meters.
Various drag body current meters are compared in Table 3.4 and Pitot tubes
in Section 3.1.6.
3.3.1,1 Rotating Element Current Meters
Of the rotating element current meters, Price and Pigmy meters are
commonly used. The principle of operation is based on the proportionality
between the velocity of water and resulting angular velocity of the meter
rotor. In conventional current meters there is a wheel which rotates when
immersed in flowing water and a device which determines the number of
revolutions of the wheel. The general relation between the velocity of the
water and number of revolutions of the wheel is given by:
V = a + bN,
where:
V = velocity of water meters per second
a and b are constants
N = number of revolutions per second
These current meters can be grouped into two broad classes:
1) vertical -axis rotor with cups or vanes and 2) horizontal -axis with vanes.
Figure 3.14 shows the propeller current meter which is typical of a
horizontal -axis current meter with vanes. Figure 3.15 shows the Price
current meter which is typical of a vertical-axis rotor current meter with
cups.
Practical considerations limit the ratings of these meters to
velocities of 0.030 m/s (0.11 fps) to about 4.57 m/s (15 fps). The
comparative characteristics of these two types are summarized below: (4)
1. Vertical -axis rotor with cups or vanes
a. Operates in lower velocities than do horizontal-axis meters.
b. Bearings are well protected from silty water.
c. Rotor is repairable in the field without adversely affecting the
rating.
d. Single rotor serves for the entire range of velocities.
58
-------
TABLE 3.4 COMPARISON OF DRAGBODY CURRENT METERS (17)
Factor
Dragbody Current Meter Type
Vertical Axis
Deflection Vane
Horizontal Axis
Pendulum Type
Deflection Vane
Pendulum
Current
Meter
Inclinometer
Drag Sphere
Velocity Range
Submerged
Installation
Debris
Wide range but Wide range
not suitable for
low velocities
No
Problem
Possible
Not a Problem
Wide range
Pendulum ball
is submerged
Affects drag
on line and
hence accuracy
of velocity
measurement
Output Recording
Readout of
Deflection
Mechanical
output
Visual
Electrical
output
No visual
readout
No, manual
operation
Suitable for low
velocities-only
single velocity
range
Possible
Not a problem
Single velocity
range
Possible
Not a problem
No, data manually
processed
Electrical
output
Deflection can
be resolved-no
visual readout
Simplicity
Simp!e
Simple
Complex
-------
Counter
Propeller
Wjding rod
Figure 3.14 Propeller Meter (16)
Revolution counter
Anemometer
Figure 3,15 Price Meter (16)
60
-------
2. Horizontal-axis rotor with vanes
a. Rotor disturbs flow less than do vertical-axis rotors because of
axial symmetry with flow direction.
b. Rotor is less likely to be entangled by debris than are
vertical-axis rotors.
c. Bearings friction is less than for vertical-axis rotors because
bending moments on the rotor are eliminated.
d. Vertical currents will not be indicated as positive velocities as
they are with vertical-axis meters.
e. They have a higher frequency of mechanical problems.
To determine the discharge (flow volume), in additions to velocity of
flow it is necessary to determine the area of flowing water or wastewaters.
This holds especially for large flows in rivers, lakes, and wide and deep
channels. A depth sounding is necessary at each vertical and width
measurement of the cross-section of flow to determine the area of flowing
water or wastewater. Sounding rods, sound weights and reels, handlines, and
sonic sounders are common equipment used for depth determinations. Marked
cableways and bridges, steel or metallic taps or tag lines are used for
width determinations. For details or procedures for depth and width
determinations, see reference.(4)
3.3.1.2 Measurement of Velocity
To determine the discharge at a particular cross-section, it is
necessary to determine the mean velocity of flow at that section. In drag
body current meters such as vertical-axis deflection vane, horizontal-axis
pendulum type deflection vane and pendulum current meters, it is possible to
integrate velocities at different depths in a particular section to obtain
the mean velocity of flow, whereas inclinometer, drag sphere, rotating
element current meters and pitot tubes measure velocity at a point.
Therefore, to obtain the mean velocity of flow at a particular vertical
section, it is necessary to take velocity measurements at different depths.
The various methods of obtaining mean velocities are:
1. Vertical-velocity curve
2. Two-point
3. six-tenths depth
4. Two-tenths depth
5. Three point
6. Subsurface
Table 3.5 compares these methods in relation to application, flow depth,
velocity measuring point(s), and accuracy.
3.3.1.3 Time of Travel-Velocity Methods
1. Salt Velocity Method (1)(2)(5)(6)
The method Is based on the principle that salt in solution increases the
conductivity of water. This method is suitable for open channels of
61
-------
TABLE 3.5 COMPARISON OF VARIOUS METHODS TO OBTAIN MEAN VELOCITY
en
ro
Methods
Considerations
Application
Flow depth
requirement
Velocity
measuring
point(s)
Mean velocity
Accuracy
Vertical-Velocity
Curve Method
Not for routine
discharge and
measurements
To determine
coefficients
for application
to the results
obtained by
other methods
Greater than
2.5 feet
At 0.1 depth
Increments be-
tween 0 . 1 and
0.9 depth
From vertical-
velocity curve
Host Accurate
Two-point Six-tenth depth
Hethod Hethod
Generally Primarily uaed
used for depths less
than 2,5 feet
Greater than 0.3 foot to
2,5 feet 2,5 feet
0.2 and 0.8 0.6 depth
depth below below the
the water surface water surface
V0«2 4- V0'.8 Observed velocity
2 is the mean
velocity
Gives consistent Gives reliable
and accurate re- results
suits
Two— tenth
Depth Method
During times of
high velocities
when measurements
at 0.6 and 0.8
depth are not
possible
Ho depth
constraint
0.2 depth
below the
water surface
Van -<*V0.2
C-Coefflclent
obtained from
vertical-velocity
curve. At that
vertical for the
particular depth
of flow
If C Is accu-
rately known can
give fairly reli-
able results
Three point
Hethod
When velocities
in a vertical
are abnormally
distributed
When more
weight to 0.2
and 0.8 depth
observatloni
is desired
Greater than
2.5 feet
0.2, 0.6 and
0,8 depth below
the water sur-
face
Vmean -
V0.2+V0.8+V0.6
4
Gives reliable
results
Subsurfnce
Hethod
When it is
impossible
to obtain
soundings
and the depth
cannot be es-
timated to an
approximate
0.2 depth
setting
Greater than
2.5 feet
At least 2
feet below
the water
surface
wean •
C x V observed
C-Coefflcient
obtained from
vert leal- velo-
city curve at
that vertical
for the parti-
cular depth of
flow
Gives rough
estimate as C
is difficult
to determine
accurately
V_ 2 " Velocity at 0,2 depth from water surface
^0.6 " Velocity at 0.6 depth from water surface
V _ " Velocity at 0.8 depth from water surface
0.8
» Mean velocity
-------
constant cross-section and for flow In pipes. Sodium chloride and lithium
chloride are commonly used. The basic procedure Is as follows:
a. Install two pairs of conductivity electrodes down stream from the
salt injection point at known distances and sufficiently far
apart in the stretch of the channel.
b. Connect the recording galvanometer to the electrodes.
c. Inject the slug of salt solution.
d. The time for salt solution to pass from the upstream to the down-
stream electrodes, in seconds, is determined by the distance on
the graph between the centers of the gravity of the peak areas.
e. Calculate the discharge, using the formula;
fli
Q « _£>iL_ f where,
T
Q = discharge in cubic meters per second
A = cross-sectional area of flow, square meters
L = distance between the electrodes, meters
T = recorder time for salt solution to travel the distance
between the electrodes, seconds.
2. Color Velocity Method
The color velocity method is used to estimate high velocity flows in
open channels. It consists of determining the velocity of a slug of dye
between two stations in the channel. This velocity, taken as the mean
velocity, multiplied by the cross-sectional area of flow gives an estimate
of the discharge. Commercially stable dyes (see section 3.4.3} or potassium
permanganate may be used as the coloring matter. The color velocity is
computed from the observations of the time of travel of the center of the
mass of colored liquid from the instant the slug of dye is poured at the
upstream station to the instant it passes the downstream station, which is
at a known distance from the upstream station.
With fluorescent dyes, the use of a fluorometer to detect the center of
the colored mass will enhance the accuracy of the results.
3. Floats
«.
There are three types of float methods used for estimating flow
measurements; surface floats, subsurface floats and integrating floats. To
determine the flow velocity, one or more floats are placed in the stream and
their time to travel a measured distance is determined. These methods are
simple, but from an accuracy standpoint, they should only be used for
estimating the discharge.
Various surface floats such as corks and stoppered bottles and
submerged floats like oranges, measure the surface velocity. The mean
velocity of flow is obtained by multiplying with a coefficient which varies
from ff.66 to 0.80.(2)
63
-------
A more sophisticated version is the rod-floats, which are usually round
or square wooden rods. These rods have a weighted end so that they float in
vertical position with the immersed length extending about nine-tenth of the
flow depth. Velocity measured by the time of travel by these rods is taken
as the mean velocity of flow. These floats are used in open channels and
sewers.
To obtain better results, the velocity measurements should be made on a
calm day when in a sufficiently long and straight stretch of channel or sewer
of uniform cross-section and grade with a minimum of surface waves. Choose a
float which will submerge at least one-fourth the flow depth.
A more accurate velocity measurement is obtained by using integrating
float measurements. The method is simple and consists of the release of
buoyant spheres resembling like ping pong balls from the channel floor. As
these spheres rise, they are carried downstream by the flow velocity. The
time from the moment of release to the moment when they surface, and the
distance traveled downstream are measured and inserted into the following
equations to determine the flow rate.
Q = DV and V = -~
where: Q = discharge per unit width of channel in cubic meters/sec.
(cubic ft/sec.)
D = flow depth, meters, (feet)
V = terminal velocity of the float, meters/sec, (ft./sec.)
L = distance traveled downstream by float, meters, (feet)
t = time of rise of the float in seconds.
In flows of large depth and velocity, integrating float methods with two
floats of different velocities of rise are used.(18)(19) The discharge is
calculated using the relationship:
D(L2-LJ
Q = * *
tg-tj where, I_2 and Lj are distances traveled
downstream by float 2 and float 1 respectively; and t2 and t, are times
of rise of float 2 and float 1 respectively.
The integrating float method is simple and does not require any
laboratory calibration. It integrates the vertical velocity profile and
yields the mean velocity or discharge per unit width of the section. The
method is suited to low velocities and is especially useful for flows having
abnormal velocity profiles, and it has practically no lower velocity limit.
To get better accuracy, the reach of the stream to be measured should be
sufficiently long and straight and the bed fairly uniform. Use a fast
rising float so that distance travelled downstream is of short length. The
shape of the float should be spherical. (18)
64
-------
3.3.2 Head Discharge Methods
This technique takes advantage of the head discharge relationship that
exists when a liquid flows over an obstruction or through a specific
(convergent-straight-divergent) channel section.
3.3.2.1 Weirs
A weir is an overflow structure built across an open channel to measure
the rate of flow of liquid.
Depending upon the shape of the opening, weirs may be termed
rectangular, trapezoidal, or triangular. When the water level in the
downstream channel is sufficiently below the crest to allow free access of
air to the area beneath the nappe, the flow is said to be free. When the
water level under the nappe rises above the crest elevation the flow may be
considered submerged: the degree of submergence depends upon the ratio of
upstream and downstream head (height of water above crest elevation) The
effect of submergence is to cause large inacuracies in the the flow
measurements. Therefore, the use of submerged weirs as the flow measuring
device is avoided.
In a sharp crested weir, flowing liquid does not contact the bulk head
but springs past it. If the bulk head is too thick for the liquid to spring
past, the weir is classed as broad crested.
Weirs may be contracted or suppressed. When the distances from the
sides of the weir notch to the sides of the channel (weir pool) are great
enough (at least two or three times the head on the crest) to allow the
liquid a free, unconstrained lateral approach to the crest, the liquid will
flow uniformly and relatively slowly toward the weir sides. As the flow
nears the notch it accelerates, and as it turns to pass through the opening,
it springs free laterally with a a contraction that results in a jet
narrower than the weir opening. If a rectangular weir is placed in a
channel whose sides also act as the sides of the weir, there is no lateral
contraction, and the weir is called a suppressed weir. Various types of
weirs are shown in Figure 3.16.
Most of the flow measurements are conducted on sharp crested weirs
without submergence and the subsequent discussion is limited to this type.
For information on sharp crested weirs with submergence and broad crested
weirs, refer to reference 2 and other books on hydraulics.
A typical sharp crested weir is shown in Figure 3.17. Figures 3.18 a,b
and c, show the various dimensions required for fully contracted rectangular
Cipolletti and V-notch weirs.
The relationship between head and discharge for different weirs is given
in Table 3.6. For rectangular weirs, the Francis formula is widely used for
flow measurements. However, it should be born in mind that it is applicable
and accurate only for sharp crested fully contracted or suppressed weirs. On
65
-------
SHAPE OF THE WEIR CREST
SHARP CRESTED BROAD CRESTED WEIR
Flow
Flow
a.
Flow
Flow
SHAPE OF THE NOTCH
RECTANGULAR
c.
"j^-JT
INVERTED
TRAPEZOIDAL
Flow
POEBING
V-NOTCH
TRAPEZOIDAL
COMPOUND
PROPORTIONAL
APPROXIMATE
LINEAR
APPROXIMATE
EXPONENTIAL
FLOW CONTRACTION
SUPPRESSED
CONTRACTED
Figure 3.16 Types of Weirs
66
-------
Point to measure Depth»H
Approx. 5.08 cm <2")
I
_ -",, 'I
, S J
Figure 3.17 Typical Sharp Crested Weir (3)
Chacn*!
B
I
y
*
r
c
a — — •
ontractio
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^i
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Contractions
a. Contracted Rectangular Weir
Contractions
b. Contracted V - Notch Weir
For Full Contraction
, P>2H and
B
con trac t Ions > 2H
c. Contracted Cipolletti Weir
Figure 3.18 Various Dimensions for Fully Contracted Rectangular,
Cipolletti and V-Notch Weirs (6)
67
-------
TABLE 3.6 HEAD-DISCHARGE RELATIONSHIP FORMULAS
00
Weir Type
Rectangular
Francis Formulas
Kindsvater-Carter
formula
Cipolletti
V-Notch
Cone formula for
90° V-Notch only
Kindsvater-shen
formula
Contracted
Q = 3.33(L-0.2H3/2J
Q = 3.33((H4-h)3/2-h3/2}
(L-0.2H)
Q - C L H 1>s
Q = 3.367 LH3/2
Q = 3.367L(H+1.5h)3/2
Q = 2.49 H2-1*8
8
Q -15 C tanr9s (2gH 5) ll
e (j) e
Suppressed Remarks
Q = 3,33LH3^2 Approach velocity neglected
Q = 3.33L((H+h)3/2-h3/2} Approach velocity taken
into consideration
o = r i H 1>s
Q ce Le He
NA Approach velocity neglected
NA Approach velocity taken
into consideration
NA V-Notch weirs are not
appreciably affected by
approach velocity
2 NA
Q » discharge in cubic feet per second L = crest length in feet
H » head in feet h = head in feet due to the approach velocity (V), = 62/2g
coefficient, L = LH-ku, where k, = ratio of crest (L) to channel width (B) , k,=L/B
6 NA = Not applicable
8 = Angle of the notch He«H+k,
ie- H-H),003
-------
the other hand the Kindsvater-Carter formula is applicable to any type of
sharp crested rectangular weir. It gives accurate results and is being
increasingly used.
The rate of flow determines the type of weir to use. A rectangular
weir is preferable for flows greater than 3.4 cubic meters/min. (2 cubic
feet/ sec.) V-notch weirs are used for flows of less than 0.17 cubic
meters/min. (1.0 to 10 cubic feet/sec.).(2) The Cipolletti weir is also
used in the same range as the rectangular weir. The accuracy of
measurements obtained by the use of Cipolletti weirs, based on the formulas
given in Table 3.6 is inherently not as great as that obtained with
suppressed rectangular and V-notch weirs. (2)
With these ranges in mind, the minimum head should be at least 5 cm
(0.2 ft.) to prevent nappe from clinging to the crest, and because at
smaller depths it is difficult to get sufficiently accurate gauge readings.
The crest should be placed high enough so that the water flowing over will
fall freely, leaving an air space under and around the jets. Requirements
for standard weir installations are shown in Figures 3.18 a,b, and c for
rectangular, Cipolletti and V-notch weirs, respectively.
For shapes other than those mentioned above, head-discharge relationship
must be established through field calibration using the salt-dilution
(Section 3.4.3) or other methods.
Flow rates for 60° and 90° V-notch weirs can be determined from the
nomographs in Figure 3.19. Figures 3.20a and 3.20b should be used for flow
rates of V-notch weirs in conjunction with the Kindsvater-Shen formula; (6)
the cone formula should be used only with fully contracted V-notch weirs.
Flow rates for Cipolletti weirs can be obtained from Figure 3.21. Figure
3.22 is a nomograph for flow rates for rectangular weirs using the Francis
formula; whereas Figure 3.23a and 3.23b should be used with the
Kindsvater-Carter formula.
3.3.2.1.1 Criteria for Installing Standard Weirs
To achieve the best accuracy in flow measurement the following criteria
should be met in installing standard weirs: (2)
1. The upstream face of the bulkhead should be smooth and in a vertical
plane perpendicular to the axis of the channel.
2. The upstream face of the weir plate should be smooth, straight, and
flush with the upstream face of the bulkhead.
3. The entire crest should be a level, plane surface which forms a
sharp, right-angled edge where it intersects the upstream face.
ihe thickness of the crest, measured in the direction of flow
should be between 1 and 2 mm (about 0.03 to 0.08 in.) Both side
edges of rectangular weirs should be truly vertical and of the same
thickness as the crest.
4. The upstream corners of the notch must be sharp. They should be
machined or filed perpendicular to the upstream face, free of burrs
69
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Figure 3.19 Nomograph for Capacity of 60° and 90°
V-Notch Weirs (17)
70
-------
0.012
0.008
0.004
0 20 40 60 80 100 120
Notch angle, degrees
Figure 3.20a Value of K^ Kindsvater-Shen Formula for
V-Notch Weir
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Figure 3.22 Nomograph for Capacity of Rectangular Weirs (7)
73
-------
0.020
0.010
V ft
-0.003
-0,010
0 0.20 0.40 0.60 0.80 1.00
L/B
Figure 3.23a Value of f
-------
or scratches, and not smoothed off with abrasive cloth or paper.
Knife edges should be avoided because they are difficult to
maintain.
5. 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 or mo.re to the surface of the
crest.
6. The distance of the crest from the bottom of the approach channel
(weir pool) should preferably be not less than twice the depth of
the water above the crest and in no case less than 0.31 m (1 foot).
7. The distance from the sides of the weir to the sides of approach
channel should preferably be no less than twice the depth of water
above the crest and never less than 0,31 m (1 foot). (Exception:
suppressed rectangular weir for which sides of the notch should be
coincident with the sides of the approach channel).
8. The overflow sheet (nappe) should touch only the upstream edges of
the crest and sides.
9. Air should circulate freely both under and on the sides of the nappe,
10. 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 maximum
head on the crest.
11. The cross-sectional area of the approach channel should be at least
8 times that of the overflow sheet at the crest for a distance
upstream from 15 to 20 times the depth of the sheet.
12. If the weir pool is smaller than defined by the above criteria, the
velocity of approach may be too high and the staff gauge reading too
low, and the head discharge relationship given in Section 3.3.1.1
will not hold good.
3.3.2.2 Flumes
In contrast to weirs which have a tendency to settle the suspended
particles near their upstream side, most flumes have a self cleansing
feature which makes them a preferred flow measuring device where sediment is
a factor in the stability of the stage (head) discharge relation.
Flumes are comprised of three sections: a converging upstream section,
a throat or contracted section, and diverging downstream section. The flume
size is given by the width of the throat section.
Consider the following factors in the location of a flume:(2)
1. Do not install flume too close to turbulent flow, surging or
unbalanced flow or poorly distributed velocity pattern.
2. Locate flume in a straight channel section having no bends upstream
of the flume.
3. For convenience install flume at a location which is readily
accessible, near the diversion point, and near the devices installed
to control the discharge.
Some of the flumes commonly used as flow measurement devices are
75
-------
described below.
a. Parshall Flumes
Parshall flumes have been developed with throat width from 2.50 mm (1
inch) to 15.24 m (50 feet). The configuration and standard nomenclature for
Parshall flumes is given in Figure 3.24. Strict adherence to all dimensions
is necessary to achieve accurate flow measurement.
Flow through a Parshall flume may be either free or submerged. The
degree of submergence is indicated by the ratio of the downstream head to
the upstream head (Hb/Hg) - submergence ratio. The flow is submerged if the
submergence ratio is:
. greater than 0.5 for flumes under 0.076 m (3 inches) size
. greater than 0.6 for flumes 0.15 m - 0.23 m (6 inches - 9 inches)
size
. greater than 0.7 for flumes 0.3 m - 2.44 m (1 to 8 feet) size
. greater than 0.8 for flumes bigger than 2.44 m (8 feet) size
a) Plan
b) Section
Figure 3.24 Parshall Flume Configuration and Nomenclature (16)
76
-------
For a free flow in a Parshall flume of size (W), the upstream head (H )
3
and discharge (Q) relationship is given by the general equation Q = CWHn.
Table 3.7 gives the values of c, n, and Q, for different sizes (W) of
the Parshall flume. Nomographs, curves or tables are readily available to
determine the discharge from head observations. Flow curves are shown in
Figure 3.25 to determine free flow through 0.07 m to 15.24 m (3 inches to 50
feet) Parshall flumes.(4)
For submerged conditions, apply a correction factor to the free flow
determined using the relationship Q = CWHn. These correction factors are
given in Figure 3.26 for different sizes of the Parshall flume.
TABLE 3.7 FREE FLOW VALUES OF C AND N FOR PARSHALL FLUME
BASED ON THE RELATIONSHIP Q = CWHn (7)
Flume Throat,
Max. Q, cfs
1
2
3
6
9
1
1.5
2
3
4
5
6
7
8
10
12
15
20
25
30
40
50
in
in
in
in
in
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
ft
0.338
0.676
0.992
2.06
3.07
4 W(*)
"
"
"
11
"
"
n
"
39.38
46.75
57.81
76.25
94.69
113.13
150.00
186.88
1.55
1.55
1.55
1.58
1~522W °"°26
n
n
H
n
n
n
ii
11
1.6
1.6
1.6
1.6
1.6
1.6
1.6
1.6
0.2
0.5
1.1
3.9
8. -9
16.1
24.6
33.1
50.4
67.9
85.6
103.5
121.4
139.5
200
350
600
1000
1200
1500
2000
3000
(*) W in feet
77
-------
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4000
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2000
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800
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400
300
20O
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6O
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30
2O
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800
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90
100
Submergence,
in percentage
Figure 3.26
Correction Factor for Flow Discharge Determination
for Parshall Flumes (22)
b- Palmer Bowl us Flumes
Palmer Bowlus flumes are venturi flumes of a supercritical flow type
designed to be inserted into an existing conduit with minimal site
requirements other than sufficient slope. Figure 3.27 shows various types
of Palmer Bowlus flumes. A laboratory study indicates that accuracies
within 3% of the theoretical rating curve could be obtained at depths as
great as 90% of the pipe diameter. (23) The chief advantage of Palmer
Bowlus'flumes over Parshall flumes is their ease of installation in existing
79
-------
End View
(a) l
Longitudinal Mid Sections
Vertical Horizontal
c
;>
(b)
XJ
(c)
Figure 3.27 Palmer Bowl us Flumes (3)
STILLING WELL
FOR H v
•»? *
STILLING WELL
PLAN
SUBMERGED
FLOW
TRANSITION
FREE FLOW
Figure 3.28 Rectangular Cut throat Flumes (5)
80
-------
conduits and sewers. Standard Palmer Bowlus flumes are available to fit
pipe sizes 15.2 cm (6 inches) to 2.4 meters (8 feet), A disadvantage of
Palmer Bowlus flumes is that they have a small range of flow, about 20:1.
Diskin flumes, (24) an unconventional type of Palmer Bowlus flume, are
portable devices but have limiting submergence, (H./H ), between 0.75 and
0.85, and are not suited to trashy or debris laden fl8ws.
c. Cut-throat Flumes
These are in a way modified Parshall flumes without throat section and
flat bottom. (Figure 3.28). They are suitable for flat gradient channels;
level flow and every flume size having the same wall lengths makes
construction easy and less costly. Analytical and experimental background
on these flumes can be found in reference 24.
d. Type HS, H, HI Flumes
These flumes are primarily used in irrigation channels and small water
sheds. Figure 3.29 illustrates these flumes. Their main advantage is
simplicity of construction, and they have a wide range of flow. Details on
discharge ratings can be found in references 2 and 25. Their design
incorporates the sensitivity of a sharp crested weir and the self cleansing
feature of a Parshall flume.
e. Other Flumes
Trapezoidal flumes (Figure 3.30) have much larger capacities than
rectangular flumes of the same bottom width. Two common types of flumes are:
1) trapezoidal flumes with bottom slope, and 2) trapezoidal critical depth
flume. Accuracy of ± 2% is claimed for trapezoidal critical depth flumes.
The San Dimas flume (Figure 3.31) was developed specifically to pass
large amounts of sediment and debris. These flumes have the advantage that
neither approach conditions nor disturbances upstream or downstream affect
their discharge ratings. Their rectangular cross-section makes them less
sensitive or accurate at low flows.
3.4 MISCELLANEOUS FLOW MEASUREMENT METHODS
3.4.1 Frictlon Forrnula
Measurements of channel or sewer bottom slope, depth of flow and flow
velocity can be used to only roughly estimate the flow. The Manning formula
is commonly used for estimating flow:
0.453 R2/3 s1/2
n
V = Average velocity, m/s
81
-------
oo
HS
H
Figure 3.29 Type HS, H, and HL Flumes (5)
HL
]
fc
v
c=>
/
L=R+2h
, 3.0' .
1x\
I-
(J \
PLAN
STILLING WELL
INTAKE
MV
JLU
FLOOR ON
£3% SLOPE
ZERO DATUM
•FREE FALL
SIDE VIEW
Figure 3.30 Trapezoidal Flume {5}
Figure 3.31 San Dimas Flume (5)
-------
n = coefficient of roughness
cross sectional area of flow
R = hydraulic radius, m wetted perimeter
s = slope of energy grade line.
The Manning formula is widely used for the engineering design of sewers
and channels. However, for flow measurement, its usefulness is limited for
a number of reasons. It is difficult to assign an appropriate value to the
roughness coefficient which varies with the channel or sewer material
(concrete or brick), and the surface of the channel or sewer (new or old).
For sewers, it varies also with the ratio of depth of flow to the depth when
flowing full.
The other inaccuracy that may enter into the flow measurement is due to the
slope of the energy grade line which is taken as the slope of the channel or
sewer. However, these two slopes may or may not be identical. For various
charts, tables and nomographs on the use of the Manning formula refer to
reference 26.
3.4.2 Radioactive Tracer Techniques (7)
Radioactive tracer techniques measure the flow rate at the time of the
measurement. These techniques require a license from Nuclear Regulatory
Commission, are simple and relatively inexpensive, and the equipment is
portable. These techniques require a section of the pipe or channel free of
branch connections and turbulence at the injection point for thorough mixing
of the tracer. The tracer must be a gamma-ray emitter, must be compatible
with the flowing liquid, and must have a half-life longer than the duration
of the test. Tracers generally used are salts of cesium-134, iodine-131,
sodium 24, "or gold-198. There are two methods of flow measurements by the
radioactive tracers: 1) Two-Point Method and 2) Total-Count Method.
Accuracies within 2% to 5% of the actual flow can be achieved using these
methods.
a. Two-Point Method
This method uses the time interval for the surge of tracer to pass
between two points separated by a determinable volume of the liquid. This
time interval is determined by peaks on the chronological chart of a common
amplifier-recorder connected to two G-M counters separated by a known or
determinable volume of a section of a pipe. The schematics of the the
arrangement of the test is shown in Figure 3.32.
b. Total- Count Method
The basic principle of the total-count method is that a well mixed
finite quantity of radiotracer, A, passing through a measurement point will
produce a total number of N counts on a Sealer connected to a Geiger counter
fixed in or near the stream some distance downstream. The value of N is
inversely proportional to the flow rate q and is directly proportional to A,
the quantity of the tracer mixed:
83
-------
RATEMETER
TRACER
INJECTOR
TJ-
Figure 3.32 Schematic of Two Point Method (7)
TRACER
INJECTOR
A MILLICURIES V
n
fl
SCALER
N COUNTS
COUNTER
CUBIC METER
MINUTE
COUNTS / MILLICURIES
M
MINUTE/ CUBIC METER
NQ
A
Figure 3.33 Schematic of Total Count Method (Upper Post) and arrangement
for the Determination of F-Factor (Lower Post) (7)
84
-------
N =
A F
, where F is a proportionality factor which is characteristic of
the isotope, the counter, and geometrical relationship of the stream. Note
that q is the flow rate at the tracer injection point.
The Total-Count Method gains versatility through the divided-stream
principle: The same number of counts is obtained on the fraction or split
flow as is obtained on the total flow. This allows one to measure a small
fraction or bypass of the total flow.
To obtain accurate results, the numerical value of F must be determined
in the laboratory by exposing the counter to a tracer solution in the same
geometrical arrangement as in the field test, to find the counting rate that
corresponds to a certain concentration of the tracer.
For example, if one desires to measure the flow of water/wastewater
through a 30.4 cm (12 inch) pipe, take a 60.8 cm (2 foot) length of 30.4
(12 inch) pipe closed at one end, and fill it up with water/wastewater
containing a known concentration of the radioactive tracer C to obtain
mi Hi curies per cubic meter (gallon). Strap the Geiger counter to the
and connect it to a sealer. Determine the number of counts per minute
Then the factor, G, for cubic meters per minute (gallons per min.) is:
cm
pipe
n.
F m /min =
n Counts perminute
C mi 11icuries per cubic meter
Arrangement for the field measurement is schematically shown in Figure
3.33, upper post. To place the measurement, inject a known amount of tracer,
A, either in a slug or gradually and record the total number of counts, N.
Calculate the flow using the formula:
Q -
M N
F substituting these values, and value of F m /minute obtained above.
The divided-stream principle is used in
sample-bucket technique, in which a fraction
a bucket containing the counter. The factor
bucket and the counter.
a modified technique, the
of total flow is passed through
F is determined with the actual
The procedure for measuring flow of a large open stream, such as a
river, is accomplished by floating the counter any place in the flow
downstream from the injection point. The value of F, is predetermined by
submerging the counter at least 15.2 cm (6 inches) under the surface of
liquid in a tank at least 1.2 m (4 feet) in diameter.
For better sensitivity a bundle of four counters connected in parallel
and enclosed in lucite pipe is used.
85
-------
3.4.3 Chemical Dilution (2)(6)(7)(27)
Chemical dilution technique also known as the salt dilution technique,
is applicable to both the open channel and pipe flow. It does not require
measurement of the stream dimensions or the measurements of fluid levels or
pressures. The flow is determined by measuring the concentration of the
chemical at two points downstream from the injection point. The following
should be considered when using this technique for flow measurements in
waters and wastewaters:
Turbulence at the point of injection of the chemical should assure
thorough mixing (especially the lateral mixing) of the chemical in
the field.
Flow in the channel or pipe should be steady.
Chemical used should meet the following requirements:
. Compatible with the fluid; no loss or deterioration of the
chemical in the fluid.
. Non-toxic to plant and animal life.
Easy and accurate quantitative detection at low concentration.
Low cost of the chemical and the equipment.
Chemicals commonly used are lithium chloride (atomic adsorption analysis
of lithium) and fluorescent dyes (fluorometer measurement) such as sodium
fluorescein, Rhodamine B, Pontacyl Brilliant Pink B, and Rhodamine WT.
However, use of sodium fluorescein is not recommended as it is easily
affected by light and bacterial action. In waters/wastewaters with high
suspended solids, there will be a pronounced loss of Rhodamine B dye.
Recommended dyes, Pontacyl Brilliant Pink B and Rhodamine WT, are compared
in Table 3.8.
TABLE 3.8 COMPARISON OF RHODAMINE B, RHODAMINE WT AND
PONTACYL BRILLIANT PINK B DYES (27)
Pontacyl Brilliant
Factors Rhodamine B Rhodamine WT (Pink B)
pH 5-10 Stable Stable Stable
Absorption 550 mu 556 mu 560 mu
peak-visible
light range
Fluorescence 570 mu 580 mu 578 mu
peaks
Suspended Pronounced Low Low
solids absorption absorption absorption
The chemical dilution technique is used in two ways: 1) continuous
addition or 2) slug injection.
86
-------
a. Conti nous-Addi ti on-of-Chemi cal-Method
In this technique the chemical of known concentration is added at a
uniform rate to the stream and the dilution is determined after it has
traveled downstream far enough to assure complete mixing. Samples collected
at various points across the cross-section which show the same dye
concentration will verify complete mixing.
r _r
L1 U2
A = q -p—==- where,
L?.Q
A = stream discharge
C« = natural (or background) concentration of the chemical in
the stream
C, = concentration of the chemical injected
C~ = final concentration of the chemical at downstream sampling
point
q = rate of injection of the chemical
b. Slug Injection Method
In this method, a known amount, S, of the chemical is added to the
stream at a point sufficiently downstream to assure complete mixing. The
concentration, C, of the chemical during its time of travel, At, is
determined by continuously sampling from the stream during the passage of
the chemical wave and mixing this constant continuous sample into a single
container to obtain an "integrated sample ," The flow is determined by the
C
relationship Q = —— where,
CAt
g _ strearn discharge
S = amount of chemical injected
IT = average concentration of chemical during its passage over a
downstream point during time interval At
3.4.4 Water Meters
An estimate of the flow can be obtained from water meter readings when
an instantaneous flow rate is not critical. This technique is used in a
confined area, such as the industrial plant. Water meters should be
certified periodically. When using the incoming and outgoing flow for an
initial estimate of the flow rate, all changes in the water quantity that
occur in various processes must not be overlooked. These changes may be due
87
-------
to water actually consumed In the process, for example, cement manufacturer,
conversion of quick lime to slaked lime, or the change of phase.
3.4.5 Measuring Level Change in Tank
In some instances the level change in a tank can be used to estimate
flow. To accomplish this, the .volume of the tank related to depth must be
established; then the flow is allowed to enter and the level change with
time is recorded. Figure 3.34 gives the relationship of depth to volume for
various shapes of the tank.
3.4.6 Pump Rates
When other methods are not available for flow measurement and a pump is
used in the system, the operating characteristics of the pump can be used to
estimate flow. One method is to multiply the pumping time and the pump
capacity at the discharge pressure as obtained from manufacturer's head
curves versus flow. (28)
Another technique is to establish the pump's horsepower and determine
the capacity from the manufacturer's curves. However, these techniques
should be used only for estimates of flows.
3.4.7 Calibrated Vessels
Another technique useful for free falling water is to capture a known
volume of water over a recorded time interval. The flow rate is then
established for a specific time. More than one measurement is necessary to
allow accurate estimates; the volume chosen should allow time for collection
to be more than 10 seconds. (29)
3.5 SECONDARY DEVICES
Secondary devices are the devices in the flow measurement system which
translate the Interaction of primary devices in contact with the fluid into
the desired read-out or records.
These devices can be classified into two broad classes:
1. Non-recording type with
a. Direct read-out such as a staff gauge.
b. Indirect read-out from fixed points as in a chain, wire weight
and float type.
2. Recording type, where the recorders may be graphic or digital.
Examples of recording type devices are: float in well, float in
flow, bubbler, electrical and acoustic.
The advantages and disadvantages of the various secondary devices are
88
-------
SPHERE
RIGHT CYLINDER
ANY RECTANGULAR CONTAINER
TRIANGULAR CONTAINER
H
Case 1
Case 2
ELLIPTICAL
CONTAINER
H
f
A
•*M
Total Volume
V «= 1/6 iiD3 = 0.523498D3
Partial Volume
V = 1/3 ird2 (3/2 D-d)
Total Volume
V = 1/4 irD^H
Partial Volume
V = 1/4 irDzh
Total Volume
V - HLW
Partial Volume
V = hLW
Partial Volume (Case 1)
V •= 1/2 hBL
Total Volume
V = 1/2 HBL
Partial Volume (Case 2)
V - 1/2 L (HB - hB)
Total Volume
V • nBDH
V - irBDh
Figure 3.34 Equations for Container Volumes
89
-------
FRUSTUM OF A CONE I
Case 1
Case 2
CONE
Case 1
Case 2
PARABOLIC CONTAINER
Case 1
Case 2
W
\
Total Volume
V = n/12 H(D12 + Dj D2 + D22)
d + d2)
Partial Volume
V = n/12 h(D!2 +
Partial Volume
(Case 1)
V = 1/12 n d2h
Total Volume
V = 1/12 TI D2H
Partial Volume (Case 2)
V = 1/12 n(D2H - d2h)
Partial Volume
V = 2/3 hdL
Total Volume
V = 2/3 HDL
Partial Volume
V = 2/3 (HD - hd) L
Figure 3.34 (Continued)
90
-------
given in Table 3.9 and relative comparison of primary and secondary open
channel flow measurement devices 1s shown in Table 3,10. Table 3.11 compares
various recording type secondary devices.
TABLE 3.9 ADVANTAGES AND DISADVANTAGES OF SECONDARY DEVICES
Device
Advantages
Disadvantages
Hook gauge or
stage board
Differential Pressure
Measurement
a. Pressure bulb
b. Bubbler tube
Surface float
Dipper
Ultrasonic
Common, accurate
No compressed air
source can be directly
linked to sampler
Self cleaning, less
expensive; reliable
Inexpensive, reliable
Quite reliable, easy
to operate
No electrical or
mechanical contact
Manual only, stilling
well may be needed
Can clog openings,
expensive
Ne.ed compressed air
or other air source;
Can't stand much abuse
In-stream float catches
debris
Oil and grease will
foul probe, possible
sensor loss
Errors from heavy
turbulence and foam
3.5.1 Non-recordingTypeSecondary Devices
3.5.1.1 Staff Gauge
A staff gauge, shown in Figure 3.35a, is usually a graduated enameled
steel plate bolted to a staff. Care must be taken to install the gauges
solidly to prevent errors caused by change in elevation of the supporting
structure.
3.5.1.2 Hook Gauge
A hook gauge, shown in Figure 3.35b, is a modification to a staff
gauge. The gauge (hook) is manually brought to the water surface and the
water elevation read.
91
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TABLE 3.10 RELATIVE COMPARISON OF PRIMARY AND SECONDARY OPEN CHANNEL
FLOW MEASUREMENT DEVICES (a)
Characteristic
Suitable for continuous
measurement
Capability for sending
signal to sample (flow-
proportional sampling)
Need for stilling well
Low initial cost
Easy to install
High accuracy of measurement
Low maintenance (incl, cleaning)
Suitable for high solids
wastewater
Low susceptibility to fouling
(rags, debris, grease)
Wide flow range
Low headless
Low auxiliary requirements
(manpower, compressed air,
AC power)
Primary devices Secondary devices
Channel-char's
only (Manning Hook gauge Differential Float
formula) Weir Flume stage board pressure Device
+ + + + +
na na na - + +
na na na + - 4-
3213 2 3
na 2 1 3 2 1
1232 3 3
3133 2 2
3233 3 2
3133 2 1
323+ + +
313+ + +
na na na 1 2 3
Ultra-
Dipper sonic
+ +
+ +
_
1 1
2 2
3 3
3 3
2 3
1 3
+ +
+ +
3 1
(a)na » not applicable
- * no or not suitable
+ • yes or suitable
1 • fair frequently a problem
2 • good, sometimes a problem
3 * excellent, seldom or never a problem
-------
TABLE 3.11 COMPARISON OF RECORDING TYPE SECONDARY DEVICES
Features
Stilling Well
Sensing Flow
Level
<*> Purge System
Moving Parts
Floating in Well
Necessary
Indirectly
Not required
Presence of
moving parts
Float in Flow
Not necessary
Directly
Not required
Presence of
moving parts
Bubbler
Not necessary
Flow level
translated
into air
back pressure
May be
required
Absence of
moving part
Electrical
Not necessary
Flow level
translated
into electri-
cal property
Not required
Absence of
moving part
where sensing
element is
physically in
the flow.
Present where
probe is lowered
for flow sensing,
Acoustic
Not necessary
Flow level
translated
into acoustic
response
Not required
Absence of
moving parts
»
-------
••
A
*
4
g SS
r,r
7, •<•»
r:=~
•g ss
B-l
B^
2-§
f-1
V,
-t....t.t.».a
a) Staff gauge
u
b) Hook gauge
Chain index mark.,
/--Scale
^-Weight
c) Chain gauge
d) Wire Weight gauge
Figure 3.35 Various Non-recording Type Secondary Devices
94
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3.5.1.3 Chain Gauge
The chain gauge, shown in Figure 3.35c, is a substitute for the staff
gauge and consists of a horizontal seal and a chain that passes over a pulley
to fasten a hanging weight. Water level is indicated by raising or lowering
the weight until it just touches the water surface. Sources of errors in the
measurement are; settling of supporting structure, temperature changes,
changes in length due to wear and wind action.
3.5.1.4 Wire Weight Gauge
Wire Weight gauge, shown in Figure 3.35d, is a modification of the chain
gauge and uses a wire or small cable wound on a reel. The reel is graduated
or a counter is used to give readings from a reference check bar of the
water elevations to the tenths and hundredths of a foot.
3.5.2 Recording Type Secondary Devices
3.5.2.1 Float in Well
It essentially consists of a float (sensor weight) and a counter weight
connected via a cable to a wheel which rotates as the float rises or falls
with changes in the water level. The wheel is connected mechanically or
electronically to the read-out or recorder. The float is installed in a
stilling well.
3.5.2.2 Bubbler
In a bubbler, Figure 3.36, a pressure transducer senses the back
pressure experienced by a gas which is bubbled at a constant flow rate
through a tube anchored at an approximate point with respect to a primary
device. This back pressure can be translated into water depth and
subsequently related to discharge.
3.5.2.3 Electrical
These devices measure the change in a electrical property (capacitance
or resistance) to sense liquid depth. The probe or sensor is part of an
electrical circuit, and its behavior in a circuit is a function of its
degree of immersion. Dippers touch the surface of the water and this
completes a ground circuit; measurement of level is then accomplished by
measuring the change in cable/reel rotation.
3.5.2.4 Acoustic
With acoustic devices, continuous measurement of liquid depth is
accomplished by measuring the time required for an acoustic pulse to travel
to the liquid-air interface and return. Of the two physical arrangements,
-liquid path and air path measurement, the air path arrangement is commonly
used since installation is simplified, is independent of fluid velocity, and
avoids any contact with the fluid.
95
-------
Air Supply
£
Pressure gauges and
reducing valve - normally
in meter box as part of
meter
This method can be
used in an open channe
or stilling well to
measure depth of flow
Meter box and
Recorder
Bubbler Pipe
Figure 3.36 Bubbler
3.5.3 Errors in Flow Measurement (20)(30)
The final measurement accuracy of a system (primary and secondary
devices included) depends on many factors.
3.5.3.1 Sources of Errors Related to the Primary Devices
Sources of errors described here are for weirs and flumes, but similar
errors are associated with other devices:
Basic errors in the discharge/head tables or formulas. In many
instances, the discharge tables, charts or formulas have been
developed empirically. They show experimental relationships.
Therefore, extrapolation beyond the range of observations from
which they were developed can lead to serious errors.
96
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Faulty fabrication or construction. Erroneous Length: An error of
0.1 foot in the length of a rectangular or Cipolletti weir will
cause an error of 1% in the flow measurement of a one foot weir. A
corresponding error in 0.30 meter (one-foot throat width) flume will
be 0.86% and that in a four foot flume 0.231.
Error due to transverse slope of weir crest. When the crest of the
rectangular or Cippoletti weir is sloped, the common practice is to
measure the head at the center of the crest. This leads to an error
of ? ?
100S L „ where:
- p - 7o
32 \r
S = Slope of the weir crest
L = Length of the weir
H = Head at the center of the weir crest
This error can be reduced to an insignificant amount if the
discharge is calculated as the difference of the discharges based on higher
and lower heads on the weir crest.
Stilling well not at a proper location. The head of the weir must
be measured beyond the effect of the drawdown. For standard weirs
the stilling well for the head measurement should be placed at a
distance upstream of four times the maximum head on the weir. For
Parshall flumes the locations of stilling wells for the head
measurement bear a definite relationship with the throat width.
Substantial errors in the field measurements have been traced to
changes in the location or design of the stilling well entrance.
Errors due to neglecting velocity of approach to weir. When the
velocity of approach is greater than 0.5 fps it should be
considered in the discharge formula. For a 0.2 feet head on the
weir, this error for approach velocities of 0.15 m/s, 0.30 m/s, and
0.46 m/s (0.5 fps, 1.0 fps, and 1.5 fps) is 2.7, 9.8, and 20.8%
respectively. This error is less when the head on the weir is
greater. For a 0.30 m (1 foot) head, corresponding figures are
0.6, 2.2 and 4.7%. Use of the Kindsvater-Carter formula will help
alleviate this error.
The error due to the reduction of depth of the weir pool. The
height of the weir, when less than twice the head on the weir, will
introduce an error of 5.6, 2.7 and 1.5% for .06 meter (0.2 foot)
head and 0.15, 0.30 and 0.61 meter (0.5, 1.0, 2.0 feet) height of
the weir. A corresponding error of a 0.5 foot head will be 13.1,
6.4 and 3.4% respectively. This error can be corrected by using
Rehbock's formula:
Q = /2q LH3/2 (0.605 + + °-08 ~~) or the
Kindsvater-Carter formula. In a standard sized weir pool, this
error can be minimized or eliminated by proper maintenance and
97
-------
cleaning.
Weir blade sloping upstream or downstream. The error introduced is
normally small. It becomes significant, however, if the face goes
out of plumb by a few degrees.
Roughness of upstream face of weir or bulkhead. The roughness of
the upstream face of weir or bulkhead can cause an increase in the
discharge. The discharge is observed to increase by changing the
roughness of the upstream face of the wier bulkhead from that of a
polished brass plate to that of a coarse file for a distance of
30.48 cm (12 inches) below the crest. The increase ranges from 2%
for 0.15 meters (0.50 foot) head to about 1% for 0.412 meter (1.35
foot) head.(30)
Aeration of the nappe. Insufficient aeration of the nappe will
increase the discharge over the weir. It has been observed that
for a drop in pressure under the nappe by 20.32 mm (0.8 inches) of
water below atmosphere pressure, the discharge increased by 3.5% at
0.15 meter (0.5 foot) head and about 2.0% at 0.30 meter (1.0 foot)
head.(30)
Other errors may be due to submergence of the weir, obstructions in
the measuring section, changes in the viscosity and surface tension,
and unstable flow at very low heads.
3.5.3.2 Errors in the Secondary Devices
Error due to incorrect zero setting of the head gauge. This error
is of the same magnitude as the error for misreading the head.
Error due to misreading the head. Popular causes of this error are
incorrect location of the gauge, a dirty head gauge, not using the
stilling well, considerable fluctuations of the water surface and
carelessness on the part of the reader. For 30.48 cm-121.9 cm
(12-14 inch) Cipolletti and 90° V-notch weirs, a small error of
3.05 cm (0.1 foot) in reading will introduce an error
approximately 7.5% in discharge results for the lower heads. For
greater heads, the error is less.
The chart related errors are common to all the recording type
devices.
These errors are the result of the variations in the chart due to
humidity, paper expansion and shrinkage.
The error common to the totalizers is the variation in the speed of
totalizer drive motors.
Other errors which are characteristics of particular secondary
devices are:
. Float Devices (12)
The error due to a float lag which is similar to the "play"
between gears. Once the index is set to the true water level
while the water is rising, it will thereafter show the correct
water level. For a falling water level however, the index will
be above the true water level by the amount of the float lag as
shown in Figure 3.37a. If the index is set at true water level
at some intermediate point between rising and falling water
levels, the index will be proportionately low by the amount of
98
-------
the float lag for rising water levels and high a similar amount
on the falling water level, as shown in Figure 3.37b. For
recorders and indicators, float lag =
0.37 — 5- , where F = force required to move the mechanism,
r
ounces. D = diameter of the float, inches, and float lag in
feet.
The error due to line shift. For every change in the water
level, there is a movement of float line from one side of the
float pulley to the other. This change of weight changes the
depth of floatation of the float, consequently the stylus
deviates from the true water height by a small amount. This is
dependent on the change in the water level since the last
correct setting, and weight of the line used between the float
and the counter weight.
p
Error from live shift = 0.37 — ~ AH where:
\T
P = weight per unit length of the line, ounces
D = diameter of the float, inches
AH = change in water level, feet and error from line shift,
shift in feet.
If the error from line shift occurs when the counter weight is
submerged, the error = p
0.34 -Af AH
The error for the submergence of the counter weight is the
result of the reduced pull on the float which leads to the
increased depth of floatation. The error for the submergence is
given by X.
AX - C PCL-2B) ,2 1_ ,
X ~ SWA WA (d ~ S, '
w X
where:
C = the counter weight
S = specific gravity of the counter weight
W - weight of the float
P = weight per unit length of the float line
L = total length of the float line from float to counter
weight
B = length of the float line, on the counter weight side
A = area of the float
S, = specific gravity of the float line
99
-------
d>
QJ
Float Lag
True Water Level
Time
a) Showing float lag when
True Water Level while
index is set
the water is
to
rising
CD
>
0)
«3
Float Lag
True Water Level
Time
b) Showing float lag when index is set at some
intermediate point between rising and
falling water levels
Figure 3.37 Float Lag (12)
100
-------
. The error due to fouling by trash or debris.
Bubbler
. clogging of the exit and base of the bubble tube
. aspiration effects due to velocity of flow
Errors due to temperature and aging
. Errors due to hysteresis (lag effect)
Electrical
Main error is due to foam, floating oil or grease in the liquid.
Acoustic
The main errors are due to foam, highly turbulent-flow and false
echo in restricted sites like manholes, meter vaults, etc.
3.5.3.3 Total Error in the Flow Measurement
Often, the total error in the flow measurement in a system is
incorrectly taken as the sum of the errors in the primary and the secondary
devices. However, the total error in the flow measurement is the square
root of the sum of the squares of the individual errors. (31) Illustrative
example is given below:
In the flow measurements through a 30.48 cm (12 inch) Parshall flume,
the flow was 0.21 m3/s (7.41 cfs) at 457.20 mm (18 inches) of head. It was
observed that there was a 3% error in the flow measurement for the Parshall
flume. The error introduced by the use of a flow measurement formula was
1.5%. There was an error of 6.350 mm (0.25 inches) in the measurement of
the throat. The error due to incorrect setting of zero was 3.175 mm (1/8
inches) and the error in the reading of the head was 3.18 mm (1/8 inches).
Calculate the total percentage error.
Percentage error in the head //error zero /error
measurement (secondary device) = Xn(e) = 100 x j\ setting J + I head-
2 '_ V reading.
(Head)2
Xn(e) = 100 ./(3.175r + 3.175)'
(457.20)2 = .982 = 1% approximately
Percentage error in the Xu(e) ~ 100 x 004 on = 2% approximately
primary device dimensions
101
-------
Percent total error In the system =
/y Percent \
[ error of ]
1 the flow/
\ /
Percent
t error of
i the formula
/Percent \
+ / error of I
I primary /
\ device /
2
/Percent \
/ error of j
( secondary)
xdevice /
i/32
1.52 + 22
= 4% approximately
3.6 REFERENCES
1. The American Society of Mechanical Engineers. Fluid Meters-Their Theory
and Application, Report of the ASME Research Committee on Fluid Meters,
6th Edition, New York, NY 1971.
2. U.S. Department of Interior. Water Measurement Manual. Bureau of
Reclamation, 2nd Edition, revised, 1974.
3. Associated Water and Air Resource Engineers Inc. Handbook for
Industrial Wastewater Monitoring. U.S. Environmental Protection
Agency, Technology Transfer, August 1973.
4. Buchanan, T.J. and W.P. Somers. Discharge Measurements at Gaging
Stations. U.S. Geological Survey, Techniques of Water Resource
Investigations, Book 3, Chapter A8, 1976.
5. Shelley, P.E. and G.A. Kirkpatrick. Sewer Flow Measurement-A State of
the Art Assessment. U.S. EPA, EPA-600/2-7 5-027, November, 1975.
6. Kulin, Gerson and P.R. Compton. A Guide to Methods and Standards for
the Measurement of Water Flow. U.S. Department of Commerce, National
Bureau of Standards, Special Publication 421, May 1975.
7. American Petroleum Institute. Manual on Disposal of Refinery Wastes.
Chapter 4, 1969 p. 1-26.
8. King, H.W. Handbook of Hydraulics. 4th Edition, McGraw Hill, 1954.
9. Strater, V.L. Fluid Mechanics, McGraw Hill, 1966.
10. Perry, R.H. and Chi! ton, C.H. Chemical Engineers' Handbook, 5th Edition,
McGraw Hill, 1974.
11. American Society of Testing Materials. Annual Book of ASTM Standards,
Part 31-Water. Philadelphia, Pennsylvania, 1967,
12. Leupold and Stevens Incorporated. Stevens Water Resource Data Book. 2nd
Edition (revised), Beaverton, Oregon, 1975.
102
-------
13. Kennard, J.K. Elementary Fluid Mechanics. 4th Edition, John Wiley &
Sons, Inc., New York.
14. Blasso, L. Flow Measurement Under and Conditions. Instruments and
Control Systems, 48, 2, pp. 45-50, February 1975.
15. Thorsen, T. and R. Oen. How to Measure Industrial Wastewater Flow,
Chemical Engineering, 82, 4, pp. 95-100, February 1975.
16. Simon, Andrew. Practical Hydraulics. John Wiley & Sons, Inc. New
York, 1976.
17. Smoot, 6.F. A Review of Velocity-Measuring Devices. USDI, U.S.
Geological Survey, Open File Report, Reston, Virginia, 1974.
18. Liu, H. Analysis of Integrating-Float Flow Measurement. Proceedings
of the American Society of Civil Engineers, HY5, September 1968.
pp. 245-1260.
19. Hajos, S. Neves. Verfahren zur Messung Kleiner Wassergeschwindigkeitan.
Zentralhlav der Bauvewaltung 24 (44), 1904 pp. 281-283.
20. Bos, M.G. Discharge Measurement Structures. Working group on Small
Hydraulic Structures, International Institute for Land Reclamation and
Improvement, Wageningen, The Netherlands. 1076
21. Kindsvater, C.E. R.W. Discharge Chacteristics of Rectangular Thin-Plate
Weirs. Paper No. 3001, Transactions. ASCE Vol. 124, 1959.
22. Robinson, A.R. Simplified Flow Corrections for Parshall Flumes Under
Submerged Conditions. Civil Engineering, ASCE. Sept., 1965.
23. Wells, E.A. and H.B. Gotass. Design of Venturi Flumes in Circular
Conduits. American Society of Civil Engineering, 82, p. 23, April 1956.
24. Skogerboc, 6.V., R.S. Benett and W.R. Wallcer. Generalized Discharge
Relations for Cut-Throat Flumes. Proc American Society of Civil
Engineering, 98. IR4, pp. 569-583, December 1972.
25. Shelley, P.E. and G.A. Kirkpatrick. An Assessment of Automatic Sewer
Flow Samplers. Office of Research and Monitoring, U.S. Environmental
Protection Agency, EPA-600/2-76-065, Washington, D.C., December 1975
26. Water Pollution Control Federation, American Society Civil Engineers,
Design and Construction of Sanitary and Storm Sewers, WPCF Manual No. 9,
ASCE Manual and Reports on Engineering Practice No. 37, New York 1969.
27. Regpolo, J.A. L.E. Myers and K.J. Brust. Flow Measurements with
Fluorescent Tracer. Proceedings of ASCE. HY5, 1966, p. 1-15.
28. Forester, R. and D. Overland. Portable Device to Measure Industrial
Wastewater Flow. Jour. WPCF 46, pp. 777-778, April 1974.
103
-------
29, Rabosky, J.G. and D.L. Koraldo. Gauging and Sampling Industrial
Wastewaters. Chemical Engineering, 80, pp. 111-120, January 1973.
30. Thomas, C.W. Errors 1n the Measurement of Irrigation Waters. Proc,
Paper 1362, ASCE IR2, 1957. P. 1-24.
31. Mougenot, G. Weirs and Flumes. Water and Sewage Works, pp. 79-81,
July 1974.
104
-------
CHAPTER 4
STATISTICAL APPROACH TO SAMPLING
For every sampling program four factors must be established:
1. Number of samples
2. Sampling frequency
3. Parameters to be measured
4. Location(s) of sampling
These variables are usually established by the discharge permit
requirements which may or may not be scientifically sound. When a new
program is being initiated or the permit requirements need review,
statistical methods and scientific judgment should be used to establish the
best procedures.
This chapter explains various statistical terms and techniques and their
applications to sampling. Each new concept is introduced with 'an example to
illustrate its use. After the basic terms are defined and illustrated,
statistical methods are introduced for analyzing data and determining the
above four factors. These methods are also illustrated with examples.
4.1 BASIC STATISTICS AND STATISTICAL RELATIONSHIPS
Data representing a physical phenomenon are broadly classified as
Continuous, such as temperatures measured constantly and recorded as a
continuous curve; Discrete, such as temperatures recorded hourly, and as
Deterministic, those capable of description by an explicit mathematical
relationship or formula; or Non-deterministic, which are random. Due to
water quality changes and the complexity of the processes affecting the
water or wastewater characteristics, one cannot predict an exact value for a
datum at a future instant in time. Such future data are random in character
and are conveniently described in terms of probability statements and
statistical averages rather than by explicit equations. However, long-term
changes in water quality tend to have a functional character with random
fluctuation components. Statistical evaluation techniques provide a tool
with which to detect and quantify both the deterministic and random
components of a water or wastewater quality record.
4.1.1 Statistical Sample Parameters - Definitions and Examples (1)
A wastewater stream is sampled once a week for a period of one year and
the concentration of a certain parameter recorded. (See Table 4.1)
105
-------
TABLE 4.1 WASTEWATER PARAMETER DATA
Week
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
TABLE 4.2
Observation
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Concentration (mg/L)
35.8
33.0
33.6
35.0
33.5
34.7
33.6
36.9
38.8
35.5
32.2
32.2
33.3
33.5
33.0
33.1
33.5
31.9
31.7
32.4
34.8
33.5
33.9
32.0
34.2
33.4
WASTEWATER PARAMETER
# Concentration (mg/L)
39.6
38.8
37.4
36.9
36.5
36.0
35.8
35.8
35.6
35.5
35.0
34.8
34.8
34.7
34.6
34.4
34.3
34.2
34.2
33.9
33.6
33.6
33.6
33.5
33.5
33.5
Week Concentration (mg/L)
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
DATA IN DECREASING
31.1
33.6
28.9
35.6
32.9
31.8
37.4
32.0
34.8
31.7
32.7
36.0
34.2
30.3
39.6
34.6
31.7
30.3
34.4
32.4
31.1
36.5
33.2
34.3
35.8
32.4
NUMERICAL ORDER
Observation # Concentration (mg/L)
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
33.5
33.4
33.3
33.2
33.1
33.0
33.0
32.9
32.7
32.4
32.4
32.4
32.2
32.2
32.0
32.0
31.9
31.8
31.7
31.7
31.7
31.1
31.1
30.3
30.3
28.9
106
-------
These data do not give much information as presented, so certain
calculations are performed to give more meaning. Two things providing
useful information about a set of data are: measures of central tendency,
such as arithmetic mean and median; and measures of deviation, such as
range, variance and standard deviation.
4.1.1.1 The Arithmetic Mean
The arithmetic mean or simply the mean is used to locate the "center"
of a data set. It is defined to be the sum of all the observations divided
by the number of observations (N):
X"
N
X.
1=1
IT
where: X. are the observations, with i ranging from 1 to N
N is the number of observations
N
I is the operator "sum" of all values of the variable following
i=l it (in this case X.) as i covers the integers from 1 to N.
A • ~ A-t ' A ^ ' A o ' ••••"•" A • i
In the above example (from Table 4.1), X, = 35.8, X9 = 33.0, . . . , Xw = X,
32.4; ' d IN
N
£
1=1
X. = 35.8 + 33.0 + 33.6 + ...+ 35.8 + 32.4 = 1748.3; and so the mean,
which is denoted I (read "X-bar"), is:
N
X
1748.3
Z Xi
- i=r
IT
FO
-3-3 K m /,
= 33.6 mg/L.
The mean can be greatly affected by extreme values. If in Table 4.2 the
first observation is replaced by 396.0 the mean becomes:
T 396.0 + 38.8 + 37.4 + ... + 28.9 _ 2104.7 _ An K mnft
X = - = - = — cj — 40.5 mg/L
1=2
107
-------
which is considerably greater than the former value of 33.6.
The mean is the most often used measure of the "center" of a data set.
4.1.1.2 The Median
The median of a set of data is the observation in the middle, that is,
the number that is located such that half of the observations are less than
it and half are greater. To find the median of a set of observations,
arrange the data in numerical order as in Table 4.2.
If N is the number of observations in the ordered data set (in this
case, N, is 52), then the median is defined to be the mean of the ^-th and
N
•k- * 1st observations if N is even (between the 26th and 27th here, which
would be 33.5) or the « — th observation if N is odd (that is with 15
ordered observations, the median is the 8th value).
The median is a good measure of the location of the center of a set of
data because it is unaffected by extreme values, since if the largest
observation were 396.0 instead of 39.6, the median would still be 33.5.
Unfortunately, it does not make use of all the information contained in the
data, but rather uses only the relative sizes of the observations.
4.1.1.3 The Range
In addition to knowing where the "center" of a data set is, it is useful
to know how spread out the data set is. One indicator of the spread of a
data set is the range, which is defined as the difference between the largest
and the smallest values in the set. For example, in Table 4.2, the largest
is 39.6 (II) and the smallest is 28.9 (#52) and so the range is R = 39.6 -
28.9 = 10.7.
Like the median, the range is simple to compute, once the data are
arranged in decreasing or increasing order, but does not use all the
information in the data.
4.1.1.4 The Variance
The variance, which is the average of the squares of the deviations of
the data from their mean, is another indicator of how spread out the
observations are. To find the variance, subtract the mean from each
observation, square each of these differences, sum the squared terms, then
divide the sum by one less than the number of observations, or in symbols:
N _?
2 s (x. - xr
s = 1=1 1
__
108
-------
Table 4.3 shows how this is done:
corresponding concentration.
i is the week and X, is the
52
E (X. -
<,
26
52
= E (X. - T) + £ (X.
1=1 1 i=271
= 67. 00 + I5l.ll = 218.11(mg/L)
Variance = s = i=1
N
7 (Y XV
L \ A _• A ;
1=1 n
N - 1
5 52
r> / y
2- ^ A
= 1=1
_
. - 33. 6T
51
= 218.11 = 4.28(mg/L
51
2
There is another formula for computing S» which will be given here
without an example:
N „
E (X Z)
This formula says to square each observation and sum the squares. Then
multiply the square of the mean (found earlier) by the number of observations
(N), subtract this from the sum of squares just computed, then divide by N-l.
This formula involves fewer steps since there is only one subtraction, as
opposed to N subtractions using the other method, and less time since there
is just one pass through the data.
4.1.1.5 The Standard Deviation
The units of the variance are the square of the units of the mean and of
the original data. That is, if the data are expressed in mg/L, the variance
2 2
is in mg /L . Because of this, the standard deviation, which is the square
root of the variance, is more commonly used as a measure of dispersion. In
2
our example, the variance, S», is 4.28, and so the standard deviation is:
SY = ^sf = /4~28 = 2,07 mg/L
A A
Since the data are expressed as mg/L.,the standard deviation is also in mg/L.
The mean (Y) and standard deviation (S ) are actually only estimates of
X
parameters known as the population mean (u ) and population standard
X
deviation (o), which are discussed in Appendix A.
X
An interesting and useful fact about these two numbers is that in a
normally distributed population (which is discussed later and is a
109
-------
TABLE 4,3 COMPUTATION OF THE VARIANCE
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Xi
35.8
33.0
33.6
35.0
33.5
34.7
33.6
36.9
38.8
35.5
32.2
32.2
33.3
35.5
33.0
33.1
33.5
31.9
31.7
32.4
34.8
33.5
33.9
32.0
34.2
33.4
26
z (X-
i=l 1
(x1 - x)
2.2
-0.6
0.0
1.4
-0.1
1.1
0.0
3.3
5.2
1.9
-1.4
-1.4
-0.3
-0.1
-0.6
-0.5
-0.1
-1.7
-1.9
-1.2
1.2
-0.1
0.3
-1.6
0.6
-0.2
- X)2 = 67.00
(xi - I)2
4.84
0.36
0.00
1.96
0.01
1.21
0.00
10.89
27.04
3.61
1.96
1.96
0.09
0.01
0.36
0.25
0.01
2.89
3.61
1.44
1.44
0.01
0.09
2.56
0.36
0.04
1
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
'43
'44
45
46
47
48
49
50
51
52
Xi
31.1
33.6
28.9
35.6
32.9
31.8
37.4
32.0
34.8
31.7
32.7
36.0
34.2
30.3
39.6
34.6
31.7
30.3
34.4
32.4
31.1
36.5
33.2
34.3
35.8
32.4
52
I (X.
i=27 ]
(x1 - x)
-2.5
0.0
-4.7
2.0
-0.7
-1.8
3.8
-1.6
1.2
-1.9
-0.9
2.4
0.6
-3.3
6.0
1.0
-1.9
-3.3
0.8
-1.2
-2.5
2.9
-0.4
0.7
2.2
-1.2
- X)2 = 151.11
(X. - X)2
6.25
0.00
22.09
4.00
0.49
3.24
14.44
2.56
1.44
3.61
0.81
5.76
0.36
10.89
36.00
1.00
3.61
10.89
0.64
1.44
6.25
8.41
0.16
0.49
4.84
1.44
-------
TABLE 4.4 COMPUTATION OF THE COEFFICIENT OF SKEWNESS
i
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
i
2.2
-0.6
0.0
1.4
-0.1
1.1
0.0
3.3
5.2
1.9
-1.4
-1.4
-0.3
-0.1
-0.6
-0.5
-0.1
-1.7
-1.9
-1.2
1.2
-0.1
0.3
-1.6
0.6
-0.2
(x1 - I)3
10.648
-0.216
0.000
2.744
-0.001
1.331
0.000
35.937
140.608
6.859
-2.744
-2.744
-0.027
-0.001
-0.216
-0.125
-0.001
-4.913
-6.859
1.728
1.728
-0.001
0.027
-4.096
0.216
-0.008
1
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
52
I (X, - I)3
X,-T
-2.5
0.0
-4.7
2.0
-0.7
-1.8
3.8
-1.6
1.2
-1.9
. -0.9
2.4
0.6
-3.3
6.0
1.0
-1.9
-3.3
0.8
-1.2
-2.5
2.9
-0.4
0.7
2.2
-1.2
= 272.765
(x1 - I)3
-15.625
0.000
-103.823
8.000
-0.343
-5.832
54.872
-4.096
1.728
-6.859
13.824
0.216
-35.937
216.000
1.000
-6.859
-35.937
0.512
-1.728
-15.625
24.389
-0.064
0.343
10.648
-1.728
-------
phenomenon which occurs quite frequently), 68.3% of the observations will
fall within juv ±a , 95.5% will be found within $ ± 2o , and 99.7% within
*x±3V
Since "X approximates AIV and S approximates o , these percentages will hold
/> A /\ '
approximately for J ± S. J ± 2SV and X" ± 3SV.
XX X
4.1.1,6 Coefficient of Variation
This statistic provides a measure of the dispersion relative to the
location of the data set, so that the spread of the data in sets with
different means can be compared.
S
Coefficient of Variation = CV = -~2-
X
4.1.1.7 The Coefficient of Skewness
The coefficient of skewness is a measure of the degree of assymetry of
the data about its mean.
Coefficient of Skewness = k =
N
NE (X, - X)
(N-1)(N-2)S3
x
In our example, k = 52 (272.765) = _63 ^see Table 4>4^
51 (50) 8.870
A positive coefficient of skewness indicates high extreme values and as
shown on pages 136 and 137, leads to a mean greater than the median.
4.1.2 Harmonic Variations (2)
The use of the statistical concepts discussed so far depends on the
assumption that the data record is random. The identification and estimation
of the transient variations of a wastewater monitoring record is extremely
important. It reduces the standard deviation, thereby making estimators more
reliable. The techniques used in identifying and evaluating these components
are trend removal and time series analysis.
4.1.2.1 Trend Removal
A trend in a wastewater monitoring record can usually be detected
graphically. Trends can be either linear (increasing or decreasing) or
non-linear (exponential or logarithmic). A trend may be defined as any
harmonic component whose period is longer than the record length. Trend
removal is an important step in data processing. If trends are not removed,
large distortions can occur both in further data processing and in
conclusions on the probability distribution of the measured parameter. In
many wastewater monitoring programs the evaluation or detection of the trend
112
-------
is a desired result in itself.
The usual method for evaluating a trend is the least-square procedure
which can be used if a random or harmonic component is superimposed on a
linear trend such that:
X(t) = X(t) + X'(t)
where X(t) is the data record expressed as a function of time. In the
Table 4.1 data, t is expressed in weeks, and so X(l) = X, = 35.8,
X(2) = X2 = 33.0,..., X(52) = X§2 = 32.4. '
X(t) is the linear trend.
X'(t) is the random component.
In this case, the trend can be approximated by a straight line of the form
X(t) = a + bt.
The coefficients a and b are computed by regression analysis and can be
proven to be:
a - It2 EX(t) - Et It X(t)
3 - n
NEt -
NZt X(t) - Et SX(t)
'
where: N = the number of samples.
t = the sampling interval
N
E = is the equivalent to i and means, "sum the following
t=l
terms for t=l through N".
After removal of this linear trend, X(t), the new time series is:
X'(t) = X(t) - (a + bt)
Table 4.5 contains a data set with a linear trend. There follows an example
of identifying and removing this trend.
It can be seen in Figure 4.1 that the data contain an upward trend and
also a harmonic component. The trend is identified by finding X(t) = a +
bt.
13685(104.90) - 595(2139.5) = i 45
34(13685) - (595)2
113
-------
TABLE 4.5 DATA SET WITH LINEAR TREND
t
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
34
It a
t-1
Data
X(t)
1.0
1.4
1.9
2.0
2.5
2.4
2.5
2.8
2.1
2.2
1.7
1.8
1.5
1.8
1.9
2.8
2.7
34,
595 It*
t-1
Computation
tX(t)
1.0
2.8
5.7
8.0
12.5
14.4
17.5
22.4
18.9
22.0
18.7
21.6
19.5
21.6
28.5
44.8
45.9
34
= 13685 z
t-1
TABLE 4.6 ADJUSTED
t
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Computation
X(t)
1.6
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.9
3.0
Adjusted Data
X'(t)
-0.6
-0.2
0.2
0.2
0.6
0.4
0.4
-0.6
-0.2
-0.2
-0.8
-0.8
-1.2
-1.0
-1.0
-0.1
-0.3
t
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
x(t) =
Data
X(t)
3.8
3.7
4.8
4.4
4.3
4.6
4.3
4.4
4.3
3.9
4.3
3.6
3.2
3.8
3.4
4.5
4.6
34
104.90 z tX(t)
t-1
Computation
tx(t)
68.4
70.3
96.0
92.4
94.6
105.8
103.2
110.0
111.8
105.3
120.4
104.4
96.0
117.8
108.8
148.5
156.4
- 2139.5
DATA SET OF TABLE 4.5
Computation Adjusted Data
t
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
X(t)
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
4.2
4.3
4.4
4.5
4.6
X'(t)
0.7
0.5
1.5
1.0
0.8
1.0
0.6
0.6
0.4
-0.1
0.2
-0.6
-1.0
-0.5
-1.0
0
0
114
-------
Figure 4.1 Series before removal of trend
115
-------
(U
3;
X
Figure 4.2 Series after removal of trend
116
-------
b = 34(2139.5) - 595(104.90) = c
34(13685) - (595)2
Therefore the line X(t) = 1.46 + 0.093 t. Since a linear trend is removed by
subtraction, the new time series is:
X1 (t) = X(t) - (a + bt) = X(t) - (1.46 + 0.093 t)
Table 4.6 lists the adjusted data and Figure 4.2 shows the series after the
removal of the trend.
4.1.2.2 Time Series Analysis
Time series analysis is the most powerful method of analyzing a large
volume of data, such as continuous records with high frequency of data
acquisition. Since large amounts of data are required, time series analysis
should not be used for short surveys or low frequency monitoring when limited
amounts of data are available, or if part of the record is missing.
1. Auto-Covariance and Auto-Correlation Analysis
These functions describe the dependence of the values of the data at
one time on the values at another time. An estimate of the
auto-covariance function (acvf) between two observations X(t) and
X(t + u), separated by a lag time, u, is given by:
i N-u _
c(u) = TJ E {(X(t)- X) (X(t + u) - X)}
N t=l
where: N is the number of observations in the record
T is the mean of the N observations
c(u) is called the sample auto-covariance function of the
time series, and is a function of the lag time, u.
Using the data in Table 4.5, we find that
X" = 104.9 = 3 l
and so, for u = 4,
c(4) =3-^ z(X(t) - 3.1) (X(t + 4) - 3.1) =3^ (1.0 - 3.1)(2.5 - 3.1) +
(1.4 - 3.1)(2.4 - 3.1) + ....+ (3.2 - 3.1)(4.6 - 3.1) = J- (22.19) = .65
34
117
-------
Since the aevf is a measure of the dependence between values separated
by a specific time period, looking at c(u) for various values of u will give
information on this dependence. For example, in this set of data, c(4) =
0.65, c(l) = 1.06, and c(10) = 0.12, This shows that the auto-correlation
decreases with increased lag time and is quite small when u reaches 10.
o
Notice that, except for N rather than N-l in the denominator, c(0) = Sv
A
the sample variance. This says that the variance is just the serial -
covariance of each observation with itself.
When the acvf is normalized by dividing by c(0), it becomes the sample
serial -correlation function (acf)
which is an indicator of how much one observation is dependent on those
around it. It gives a visual picture (when plotted against the lag, u,
between points) of how the dependence damps out as the lag increases. This
graph is called the auto-correlogram. Figure 4.3 is the auto-cbrrelogram
for the data in Table 4.5. The fact that the curve in Figure 4.3 is
somewhat like a sine wave is reflected in the auto-correlation, which begins
to show negative correlation after u passes 11. For purely random data the
acf would approach zero as u increases. A periodic component in the record
would result in a periodic auto-correlogram with period similar to that of
the original data. The principal application of the acf is to establish the
influence of values at any time over values at a later time. It provides a
tool for detecting deterministic data which might be masked in a random
background.
2. Variance Spectral Analysis
In the analysis of time series, the "variance spectrum" more commonly
known as "power spectrum" is a basic tool for determining the mechanism
generating an observed series. The power spectrum is just the Fourier
Transform of the theoretical acvf, Y(U), and so is defined, as a function of
frequency f,
by r(f) = fZ y(u) cos (2irfu) du
where y(u) = E {(X(t) - u) (X(t+u) - u)}.
(The expectation operator E is defined in Appendix A).
By definition (Section 4.1.1), variance is a measure of the dispersion of
observations about their mean value. This dispersion may result from purely
random fluctuations (noise) in the observed data as well as from deterministic
(non-random) fluctuations. These deterministic fluctuations may be the result
of trends (linear) as well as periodic components in the record. Spectral
analysis is a useful tool for the analysis of data records in which both
random and deterministic fluctuations may be present as it allows its user
118
-------
I i i i i i i ^""H i i i i i i i I i i i i i i i i i
CO
LO
Jut
0)
o>
O)
E
»r*"
+»
O)
o
•
oa
o
Figure 4.3 Serial-eorrelogram
119
-------
to separate these two types of fluctuations.
In spectral analysis of a data record, which ideally but not necessarily
should be continuous, the power spectrum r(f) of the series is plotted
against frequency f. Figure 4.4 shows six hypothetical data records and
their corresponding power spectra.
Figure 4.4a shows a record on which all observed values are equal and
therefore equal to their mean. Their variance is zero and therefore the
power spectrum plot is zero at all frequencies.
Figure 4.4b shows a record with a linear trend. The variance in this
record is a result of the time dependent linear trend in the record. There
is no random or periodic dispersion about the mean, consequently all of the
variance (or power) spectrum is concentrated at the zero frequency.
Figure 4.4c shows a record exhibiting periodic harmonic fluctuations with
frequency f\. The variance in this record is a result of the harmonic
fluctuation of frequency f^ about the mean. All the power spectrum is
concentrated at the f\ frequency.
Figure 4.4d shows a record with purely random fluctuations (white noise)
about a constant mean value. The variance in this record is a result of
these purely random fluctuations. There is no trend or harmonic
fluctuations. The power spectrum is uniformly distributed over all
frequencies.
Figure 4.4e shows a record with purely random fluctuations superimposed
on a linear trend. Its power spectrum is the superposition of power spectra
corresponding to the linear trend record and the purely random record.
Figure 4.4f shows a record with purely random fluctuation superimposed
on harmonic variations of frequency f x. Its power spectrum is the
superposition of power spectra corresponding to the harmonic record and the
purely random record.
The power spectra depicted in Figure 4.4 are theoretical power spectra.
They are based on infinite continuous records. In practice, records will be
of finite duration and discrete. When evaluating the power spectrum of a
finite duration record it is assumed that this finite record repeats itself
periodically at intervals of length equal to the duration of the given
record.
When dealing with discrete records or digital treatments of a continuous
record, the frequency of data acquisiton is a frequency foreign to the
phenomenon under study which would appear in the power spectrum. These two
practical limitations on spectral analysis lead to distortion in the low and
high frequency regions of the spectrum known as "aliasing". The highest
frequency which can be resolved from a discrete record with sampling interval
At is the "Nyquist frequency"
f max = --
120
-------
x(t)
u
91
Q.
t, time.
frequency
(a) Constant record
X(t)
time
frequency
(b) Linear trend record
X(t)
wave length
;., ».i
[Corresponding to I
ttae
frequency
(c) Harmonic record
Figure 4.4 Typical theoretical power spectra for several records
121
-------
X(t)
tltae frequency
(d) Purely random fluctuations
X(t)
W***^**^
time frequency
(e) Linear trend with random fluctuations
X(t)
tine
frequency
(f) Harmonic record with random fluctuations
Figure 4.4 (Continued)
122
-------
Furthermore, the length of the record should be large enough to resolve
its periodic fluctuations. For example, spectral analysis of the portion AB
of the record in Figure 4.4f would lead to a power spectrum similar to that
of Figure 4.4e and not the actual power spectrum of Figure 4.4f,
Also, purely random fluctuations (white noise) are never met in
practical applications where the theoretical power spectra depicted in
Figures 4.4d-f would not be obtained. Rather, spectra similar to those of
Figures 4.5a-c would be encountered. In Figure 4,5a the absence of any
significant peak in the spectrum reflects the absence of any significant
periodicity in the record of 4.4d. In Figure 4.5b the presence of a
significant peak at the low frequency end of the spectrum is indicative of
the linear trend in the record of Figure 4.4e. The significant peak at
frequency fl on the spectrum of Figure 4.5c reflects the presence of the
harmonic component of frequency f^ in the record of Figure 4.4f.
The following rules of thumb should be followed when using spectral
analysis;
. The length of the record should be at least 10 times as long as the
longest period of interest. For example, 10 years of data, if the
annual period is the longest period of interest.
. The sampling interval should be less than half the shortest period
of interest, which would then have the Nyquist frequency. A sampling
interval of one third or one fourth the length of the shortest period
of interest is recommended.
In view of the length of record and the high frequency of data
acquisition necessary for accurate spectral analysis, an overwhelming number
of Calculations will have to be carried out and treatment of the data on a
digital computer in necessary. In carrying out spectral analysis with the
aid of a digital computer, the practitioner may wish to write his own
program or take advantage of existing programs such as BMD02T, BMD03T,
BMD04T, or SPECTRA which are described in references (3)(4).
4.1.3 Probability Density Functions (1)(5)(6)
When data are not deterministic, that is when they cannot be defined by
an explicit function, there may be a probability density function (pdf),
denoted by fv(x), which describes the probabilistic properties using the
formula:
x
FV(X) = P(X -x) = /oofx(u)du, for continuous functions, or
x
MX) = P(X -x) = u = £ f¥(u), for discrete functions
A —oo A
where P(X - x) is read "the probability that X is less than or equal to a
certain fixed value, x".
123
-------
frequency
1/2 At
(a)
r\
frequency
1/2 At
(b)
frequency
1/2 At
(c)
Figure 4.5 Typical practical powe
for the records of Figure 4.4 d»
r spectra
d»e» and f
124
-------
4.1.3.1 The Gaussian or Normal Distribution
This is a widely used and frequently found distribution because many
natural occurrences tend to behave according to this distribution in the
long run (sometimes very long). If X has a normal distribution with mean u
and variance o 2, then
A
f (X) _J /-(x-Wx)2\
T¥W = _ exp 1—land so
^ 2a 1
x
p(X
-------
4.1.3.5 Determination of the Type of Distribution (5)
To apply the concepts of statistics, the type of distribution from which
the observations came must be determined (or approximated). There are both
graphical and numerical methods from accomplishing this.
Graphical Procedure for Small Sample (N <30)
Step 1. Arrange the da'ta in increasing order of magnitude as for finding the
median, and assign a ranking number, m, to each value. The
smallest observation will have rank 1 and largest will have rank N.
(See column 1 of Table 4.7).
Step 2. Calculate the percent probability for each value, using the formula
P = —i m" ' where m is the rank as defined above and P is
m N m
the percent probability of an observation being less than
or equal to the m— value.
Step 3. Plot each value against its corresponding percent probability on the
appropriate probability paper for the distribution of interest.
An example of data treatment is shown in Table 4.7 and Figure 4.7. If
the data have a normal distribution, the plot will be a straight line on
normal probability paper. If the data have a log-normal distribution, then
they will yield a straight line when plotted on log probability paper.
Notice that in this example the data approximate a straight line fairly well
except near the upper end and at one point at the lower end. Even these do
not show a large deviation from the straight line. This indicates that the
data have an approximately normal distribution.
Using the facts that approximately 68.3% of the values are within the
interval T ± S , and the percent probability of the mean of the normal
X
distribution is 50 since the mean is equal to the median, S can be
/\
graphically estimated from Figure 4.7. To do this, we find the interval on
the horizontal axis, with the mean of 50 at its center and width 68.3,
(making the end-points 15.85 and 84.15. Then, move up from the larger of
these points to meet the line that approximates the distribution. Then,
moving horizontally to the left, we read from the vertical axis the
observation corresponding to this percent probability. The observation on
the vertical axis corresponding to 50 on the horizontal axis, is also found,
which, as was mentioned before, is the mean and also the median of the
distribution, and could therefore be determined by finding the median of the
data which are already arranged in increasing order. The difference between
these two numbers is approximately equal to S , the standard deviation of
j\
128
-------
TABLE 4.7 COMPUTATIONAL TABLE FOR GRAPHICAL NORMAL OR PEARSON TYPE III
DISTRIBUTION DETERMINATION
rxj
<£>
Week (1)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24 '
25
26
Concentration (X.) f
30.8
28.6
28.5
28.6
30.0
27.2
28.3
28.5
28.1
26.7
27.4
29.8
27.4
29.2
26.1
25.9
27.9
32.4
27.0
26.8
30.6
34.6
29.6
26.0
31.5
29.5
Rank (m)
23
16
14
15
21
7
12
13
11
4
9
20
8
17
3
1
10
25
6
5
22
26
19
2
24
18
Plotting p_ 50(2m-l)
Position N
86.6
59.6
51.9
55.8
78.8
25.0
44.2
48.1
40.4
13.5
32.7
75.0
28.8
63.5
9.6
1.9
36.5
94.2
21.2
17.3
82.7
98.1
71.2
5.8
90.4
67.3
-------
X
X
X
X
X
X
XX
X
X
CT>
to
en
in
en
o
en
o
CO
o
1^
o
U3
O
O ' £
_
-------
the data. {Note that the more the plotted points deviate from a straight
line, the less accurate this estimate will be). Figure 4.8 shows the data
have an approximate normal distribution with mean 28.7 and standard
deviation (30.8 - 26.6)/2 = 2.1.
Computational Method (8)
Another method for estimating the distribution of a data set uses the
coefficient of skewness, along with the mean and standard deviation, all of
which were defined earlier. The following has been recommended as a
relationship between the coefficient of skewness and the best approximating
probability distribution:
Best Fitting
Coefficient of Skewness, (k) Probability Distribution
< 0.5 Normal
0.9 - 1.6 Pearson Type III
> 1.7 Log-Normal
Since these ranges of skewness were empirically determined and it is
impractical to have gaps between the ranges, it seems reasonable to
interpolate and thus end up with the following adjusted table:
Best Fitting
Coefficient of Skewness, (k) Probability Distribution
<0.7 Normal
0.7 - 1.7 Pearson Type III
> 1.7 Log-Normal
Using the data from Table 4.1 compute the coefficient of skewness using
N _3
N 2 (X. - XT
k = 1=1 1
(N-1KN-2) $K
which was found in Section 4.1.1. to be 0.63. As recommended above assume
that these data have a normal distribution with mean 33.6 and standard
deviation 2.07 (that is, X ~ N(33.6, 4.28)).
Admittedly, this is a rather informal way of selecting an assumption for
the underlying distribution. If more rigorous justification is required to
support the distribution assumption, please consult a qualified statistician
for more formal techniques.
131
-------
4.1.3.6 Normal Tables (Table 4.8)
Statistics texts and books of mathematical tables usually contain a table
which gives the area under the standard normal curve to the right of a given
value z, which is P{ X>z} (= P{X< - z>), so that one need not evaluate the
•f- CO
integral / f (t)dt, to find the probabilities. Appendix B briefly
Z. X
discusses the relation between the integral and Table 4.8.
Example 1:
Find P{X<-1.93> 1f X-N(O.l)
This probability is equivalent to P{X>1.93)= 0.0268 from Table* 4.8.
Example 2:
Find the number z such that P{X>z) = .14345. Looking in the body of the
table, it is necessary to interpolate between 1.06 and 1.07 to find z, since
.14345 is halfway between 0.1423 and 0.1446.
z = L06 * 1.07 = 1-065
4.1.4 Hypothesis Testing(l)(5)
A common use of statistics is in testing whether a sample came from a
particular distribution with specific parameters. It is known that if X has
2
a normal distribution with mean u and variance a , then
X X
Z = "^x has a standard normal distribution. A theorem
0x
in statistics states that for a large sample (usually N > 30) from any
distribution, X"will have an approximately normal distribution with mean *J—
A
2 2
= u and variance a- =0 /N. Using this information, the hypotheses about
X XX
ju can be tested.
f\
Example:
Choose a random sample of 100 observations from a population with u =
X
300 and o = 70. Find the probability that T, the sample mean, is 286 or
X
less. Assume that X" is normally distributed, and so
132
-------
TABLE 4.8 AREAS UNDER STANDARDIZED NORMAL DENSITY FUNCTION (9)
Value oC a - /'," /-" »X|>(-z2/2)-P(x>x }
za
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1,2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
9
0
0.00
5000
0.4602
0
0
0
0
4207
3821
3446
1085
0.2743
0.2420
0.2119
0
0
0
0
1841
1587
1357
1151
O.Q96B
0.0808
0
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0668
0584
0446
0359
0287
0228
0179
0139
0107
00820
00621
00466
00347
00256
00187
0.01
0.4960
0.4562
O.A16H
0.37B3
0 , 3409
0.3050
0,2709
0.2389
0.2090
0.1814
0.1562
0.1335
0.1131
0.0951
0.0793
0.0665
0.0537
0.0436
0.0351
0,0281
O.OZ22
0.0174
0.0136
0.0104
0.00798
0.00604
0.00453
0.00336
0.00248
0.00181
•"-"
0.02
0,4920
0.4522
0.412')
0,17*5
0,3372
0.3015
0.2676
0.2358
0.2061
0.1?88
0.1539
0,1314
0.1112
0.0934
0.0778
0.0643
0.0526
0.0427
0.0344
0.0274
0.0217
0.0170
0.0132
0.0102
0.00776
0.00587
0.00440
0.00326
0.00240
0.00175
^
0.03
0.4880
0.44R3
0,4 {I'm
0.3707
0,'J33fl
0.2981
0.2643
0.2327
0.2033
0.1762
0.1515
0, 1292
0.1093
0.0918
0.0764
0.0630
0.0516
0.0418
0.0336
0.026B
0.0212
0,0166
0.0129
0.00990
0.00755
0.00570
0.00427
0.00317
0.00233
0.00169
\
».!
0.04
0,4840
0.4441
O.'lOM
a, MM
0.3300
0.2946
0.2611
0.2296
0.2005
0.1736
0.1492
0.1271
0.1075
0.0901
0.0749
0.0618
0.0505
0,0409
0.0329
0.0262
0.0207
0.0162
0.0125
0.00964
0.00734
0.00554
0.00415
0.00307
0.00226
0.00164
Area »
$Saraa
0,05
0.4801
0.4404
0,4013
0.3632
0.3264
0,2912
0,2578
0.2266
0.1977
0.1711
0.1469
0.1251
0.1056
0,0885
0.0735
0.0606
0.0495
0.0401
0.0322
0.0256
0.0202
0.0158
0.0122
0.00939
0.00714
0,00539
0.00402
0.00298
0.00219
0.00159
a
0.06
0,4761
0.4364
0. W74
0.359'.
0.3228
0.2877
0.2546
0.2236
0.1949
0,1685
0.1*46
0.1230
0.1038
0.0869
0.0721
0.0594
0.0485
0.0392
0.0314
0.0250
0.0197
0.015ft
0.0119
0.00914
0.00695
0.00523
0.00391
0.00289
0.00212
0.00154
0.07
0.4721
0.4325
0.3936
0.3W7
0.3192
0.2843
0.2514
0.2206
0.1922
0.1660
0.1423
0.1210
0.1020
0,0853
0.0708
0.0582
0.0475
0.0384
0,0307
0.0244
0.0192
0.0150
0,0116
0.00889
0,00676
0.00508
0.00379
0.00280
0.00205
0.00149
0.08
0,4681
0.4268
0.3897
0.3520
0,3156
0.2810
0.2483
0.2177'
0.1894
0.1635
O.H01
0,1190
0.1003
0,0838
0.0694
0,0571
0.0465
0.0375
0,0301
0.0239
0.0188
0.0146
0.0113
0.00866
0.00657
0,00494
0.00368
0.00272
0.00199
0.00144
0.09
0.4641
0.4247
0,3859
0.3483
0.3121
0.2776
0.2451
0.2148
0.1867
0.1611
0.1379
0.1170
0.0985
0.0823
0.0681
0.0559
0.0455
0,0367
0.0294
0.0233
0.0183
0.0143
O.OUO
0.00842
0.00639
0.00480
0.00357
0.00264
0.00193
0.00139
133
-------
X - u- X -
0 Y °Y/ i/M
x x/ IN has a standard normal
7 —•
distribution. In this example, Z = • = -2
70 /100
Turning to a table of areas under the standard normal curve (Table 4.8), the
area to the left of -2, which is the same as the area to the right of 2, is
0.0228, which is, then, the probability that X is less than or equal to 286
and is written P(X-286) = 0.0228. This means that if a larger number of
samples of size 100 are taken from this population, approximately 2.3% of
them will have sample means of 286 or less.
2
If the population parameters (u and 0 ) are unknown, this method can be
X X
used to make inferences about them. Suppose it is known that o = 70 and
that the mean of a random sample (X) with N = 100 is 318. Can it be
reasonably assumed that the population mean, JLI is 300?
X
Test to see if u = 300. This hypothesized value is called u and the
A w
hypothesis that ju = u is called H (the null hypothesis). Write the null
hypothesis: H : JLI = u (in this case, H : ju = 300)
iJ f\ w C? A
The alternative is that u f 300. This is called the alternative hypothesis
X
and is denoted H, : u f u . Z /9 = Z n9r- = 1.96 and so the
I X 0 Ot/ £ * \JC* 0
critical region for the re;
The test statistic used is
critical region for the rejection of H is {z:z - - 1.96 or z - 1.96}.
z » X - uo - 318-300 =2.57
Oj 70 /lOtf
In this case z = 2.57 > 1.96 = Z ,2* anc' so reject H and conclude that the
distribution from which the sample was taken has a mean other than 300.
If both u and a are unknown, the z-statistic as above cannot be used,
s\ J\
since its calculation involves a . so use the statistic
/v
* = " U° which has a Student's t-distribution.
..
Sx/
134
-------
Example:
If in the above example, the standard deviation is unknown, but the
sample standard deviation is found to be 70.5, then the test statistic is
t = 318-300 = 2 5g
70.5/400
Using Table 4.9 which gives values of t (which is the number such that
n jQ.
P(*n > *„, ) = a> where t has a Student's t-distribution with n degrees of
n n $ ct , n
freedom), look under a = .025 (since a two-tailed test at the .05 level of
significance is being used) and n=99. (The degrees of freedom, n, is just
N-l). Since n=99 does not appear in the table, take the number
a-pproxitnately 2/3 of the way between n=60 and n=120. The test statistic,
t=2.55, is greater than that for n=60, and so reject H : u = 300 in favor
of H, : u¥ + 300. ° x
I /\
Example:
If a different sample is taken, say of size 121, from the same
population and a sample mean of 310 and a sample standard deviation 70.2 are
computed, the following results:
* x - u 310-300 , K,
t = o = = 1.56.
Sx
70.2/^21
Loo'king in Table 4.9 for a = .025 and n - N - 1 = 120, it is discovered that
t!20> 025 = 1-980» and so tfie test statistic does not fall in the critical
region. Therefore, H cannot be rejected.
4.1.5 Confidence Intervals
4.1.5.1 Confidence Intervals for the Mean (1)(5)
In the example above, a hypothesis about the population mean was tested.
In a similar way, an interval could be constructed within which would be
considered a hypothesis for the mean tenable and outside of which such a
hypothesis would be untenable. This interval is called a confidence
interval and its end-points confidence limits.
In the previous example, a population mean of 300 was found to be
consistent with the computed statistics. Suppose H ;u = 295 was tested
against H-,:u ^ 295. Then _ ° x
4. _ x - u _0 ~r- which is greater than
u "~* 0 ""£• • *30
135
-------
TABLE 4.9 PERCENTAGE POINTS OF STUDENT t-DISTRIBUTION (9)
Value of tn;« such that P(t > tn;a)=a
It
1
2
3
4
5
6
7
8
9
JO
11
12
J3
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
40
60
J20
0.10
3.078
1,886
1.638
1.533
1,476
1.440
1.415
1.397
1.383
1.372
1.363
1.356
1.350
1.345
1.341
1.337
1.333
1.330
1.328
1.325
1:323
3.321
1.319
1.318
3.316
1.315
1.314
1.313
1.311
1.310
1.303
1.296
1.289
S
0.050
6.314
2.920
2.353
2.132
2.015
1.943
1.895
1. 860
1.833
1.812
1.796
J.782
1.771
1.761
1.753
1.746
1.740
1.734
1.729
1.725
1.721
1.717
1.714
1.711
1.708
.706
.703
.701
.699
.697
1.684
1.671
1.658
H
**••
a.
0.025
12.706
4.303
3.182
2.776
2.571
2.447
2.365
2.306
2.262.
2.228
2.201
2.179
2.160
2.145
2.131
2.120
2.110
2.101
2.093
2.086
2.080
2.074
2.069
2.064
2.060
2.056
2.052
2.048
2.045
2.042
2.021
2.000
1.980
VJZ%?
a
0.010
31.8Z1
6.965
4.541
3.747
3.365
3.143
2.998
2.896
2.821
2.764
2.718
2.681
2.650
2.624
2.602
2.583
2.567
2.552
2.539
2.528
2.518
2.508
2.500
2.492
2.485
2.479
2.473
2.467
2.462
2.457
2.423
2.390
2.358
ea = a
0.005
63.657
9.925
5.841
4.604
4.032
3.707
3.499
3.355
3.250
3.169
3.106
3.055
3.012
2.977
2.947
2.921
2.898
2.878
2.861
2.845
2.831
2.819
2.S07
2.797
2.787
2.779
2.771
2.763
2.756
2.7SO
2.704
2.660
2.617
a s= 0.995, 0.990, 0.975, 0.950, and 0.900 follow
from tn;l-a = -tn;a
136
-------
- 025 = 1*980» so reject H in favor of H-,. Somewhere between 295 and
300 is a mean such that the computed t is equal to t . and this number is
n » ct j
the lower confidence limit for the population mean. Similarly, if H :ju =
O A
322 is tested against H^n j* 322, t = -1.88, which is greater than -t120.
n9R, and so H is acceptable. But a test of H :u = 323 yields t= - 2.03 <
• \J t~ \J \J \J A>
-1.98 and so H is rejected. Therefore, the upper confidence limit is
between 322 and 323. The actual confidence limits for u can be computed
J\
from _ _ _ _
X - JJX X - M
= - and "
-1; a/2
which in this example yield:
Sx _ , 70.2
' ' x) =(~ l'9* * ' 310) = 297'4
and: ju,, = -(-1.98 . _ 310) = 322.6
Since a = 0.05 { and l-a= .95), 95% of all intervals constructed in this
way will contain the population mean u , and so are called 95% confidence
» s\
intervals or limits for u (If ct= .01, we construct a 99% confidence
X •
interval). Without going through the above derivation, the confidence
limits can be computed using the following formulas:
Sv t
" = x + ( N"1; a/2)
*
JJL = X - -*- (VU a/2)
4.1.5.2 Confidence Interval for the Variance
2
4.1.5.2.1 Confidence Interval for °x if ^x is known
If X has a normal distribution, then
137
-------
X - ^x has a standard normal distribution.
o
x
If X,, Xp, . ...,X,, all have a normal distribution with the same mean
2
and the same variance a , then
N (X.-jj)2 2
Y = £ _ has a x distribution (i.e. a chi-square
i=1 —j- n
distribution with n degrees of freedom).
Using a chi-square table (Table 4.10), construct a 95% confidence
2
interval for o as follows:
2
Find: X M . f> which is the number that:
IH J OS/ C. ,
P(Y< X2N. Q/2) = a/2 = .025, for a = .05
Also find: xjj. j_ a/2 = 4-,. 975
Now P
/ x.a/2
-------
10 2 10 2
S (X_.-uv) = EX.. Let this sum be equal to 113.45.
1=1 1 x i=l 1
2
A 95% confidence interval (a/2 = .025) for a is then:
| 113.45 , 113.45 1 {ti K -. Q,
[ 20.48 3.25 J " VD-D' ^-y>-
2
4.1.5.2.2 Confidence Interval for CTx If xis Unknown
2
It is also true (by the definition of S ) that
(N-l)S2
2
°x
2
has a chi-square distribution with N-l degrees of freedom (XN_-i) and so if
2
JLI is unknown, a confidence interval can be found using S , the sample
X A
variance. Suppose in the above example, S = 3.6. Turn to Table 4.10 again
/\
2 2
and find x g. 005 and x g. gjc which are 19.02 and 2.70, and so the
interval is:
2 2
us, N^
'N5x , N:>x _ 9x12.96, 9x12.96 _ ,, , d, 9^
2 2 2.70 19.02 w'if ™*fc'
x 9;.975 x 9;.025
The confidence limits for the standard deviation are found by taking the
square root of those for the variance.
4.1.5.3 Relative Error of the Standard Deviation
2 )"J - ( 2
c N-IJl- O-/L N-l} tt;
\
where 0 is the width of the confidence interval of the standard deviation
x M I. ••_ a,y 1S defined above
(1-a) x 100% is the level of confidence of the interval.
140
-------
4.2 DETERMINATION OF NUMBER OF SAMPLES (10)
The number of samples necessary to reasonably characterize a water or
wastewater is determined after collecting some background data on the
concentration and variance of the concentration of the parameters under
consideration. These values can be estimated; however, estimation will
decrease the confidence in the results. Two techniques can be used to
calculate the number of samples, one based on the allowed sample
variability, the other on the accuracy of the sample mean. Each will give a
desired value of N, the number of samples needed, with the larger value to
be chosen for application.
4.2.1 Determining Number of Samples from a Constraint on the Variability
To apply this method, the following information is needed:
JL
1. Allowable error of the standard deviation S
X
2. Confidence level required (1-a)
Therefore, for this situation, one is estimating that the value of a
certain variable will occur'within a specific interval. A normal
distribution of the data is assumed. The data should be checked for
normality as in Section 4.1.3.1.
Example:
Determine the number of samples required from a wastewater monitoring
program such that the estimated standard deviation will be within 25% of its
true value ,(i.e.± 12.5%) at a confidence level of 98%.
_n_ _fi_
Here a = 1-.98 = .02 and S = 0.25. From Figure 4.8, the value of S
A X
= 0.25 is found on the vertical axis and a horizontal line is followed until
the curve for a = .02 is met. Then a vertical line is dropped to the
horizontal axis to find the number of observations needed (N = 180 in this
case) .
4.2.2 Determining Number of Samples from a Constraint on the Mean Value
To apply this method, the following information is required:
1. Confidence level required (1-a) <-
2. Coefficient of variation of the source to be sampled /~v _ _x_\
3. The required accuracy of the sample mean * TT '
A double iteration procedure is recommended, especially if the number of
samples is found to be small (N < 30). For this calculation a normal
distribution is assumed.
141
-------
10.0
5,0
= = 0.02 |H« = 6.01
• CC a 0.05 "
0.2
J 1 I I 1 II
Graphical Solution to Equation
N-1;1-CC/2
N-1;cc/2
1.D
\
Or5
n
s
0.1
P.p5
4
I
0,01
I
I
10
50 100
= 180
500 1000
Sample Size, N
Figure 4.8 Determination of the number of samples based
on the required accuracy of extreme values
142
-------
(rv x 7 \2
a/2 ]
D/100 /
where:
D is the allowed deviation of the sample mean from the true mean,
expressed as a percent of the true mean.
Z ff) is found in Table 4.8.
a/2
For the second iteration, use: N = |CV x tg/2;N'-1
where t /O.MII is found in Table 4.9.
Example:
D/100
For a wastewater stream with an average daily concentration of 120 mg/1
BOD and a standard deviation of 32 mg/1, determine the number of daily
samples which would provide an accuracy of the daily averages within 5%.
D = 5
J = 120
S = 32
x
^x 3?
r\i = *. = Jf- = f\ 97
V V ~™^— _ ^_-~~~ _ \J t £_ /
X 120
If a = .05 (95% confidence level) is chosen, then Z /9 = I n9(- is
found in Table 4.8 to be 1.96. a/£ 'u"
Step 1 N1 = /0.27 x 1.962\ = 109.3 = 110 samples
\^ 5/100 /
Step 2 Using N1 = 110, find t a/2.N«_i = * 025-109 1'n Table 4-9 to
be approximately 1.983 (using linear interpolation), so
/ \2
N = /0.27 x 1.983 p = 114.6 = 115 samples
^5/TOOJ
If the accuracies of both the standard deviation and the mean are used
as criteria, choose the larger of the two values of N. In the example
above, N = 180 from the constraint on S, and N = 115 from the constraint on
X, so 180 daily samples should be taken.
143
-------
4.3 DETERMINING SAMPLE FREQUENCY
Although it requires the use of a digital computer, spectral analysis is
the method that should be used for determining sampling frequency because of
its accuracy and the simplicity of the final interpretation.
4.3.1 Determination of the Sampling Frequency from Power Spectra (11)(12)
It is imperative that a good set of historical data be available for
analysis. Ideally, these data should be a continuous record of the
characteristics being studied. Practically, they should be taken at a
frequency that is higher than the highest expected frequency of harmonic
variation components of the record. For example, if daily trends are to be
analyzed, hourly samples may be called for. At any rate, the length and
sampling interval of the record should satisfy the rules of thumb governing
spectral analysis (cf. Section 4.1.2.2). Ideally, in a record of discrete
data, there should be no missing points. Interpolation may be used if a few
data points are missing, when these are widely scattered on the record.
Interpolated data should account for no more than five percent of the total
data.
The following examples illustrate the use of spectral analysis in the
determination of sampling frequency.
Example 1:
The wastewater influent for the city of Racine, Wisconsin, was sampled
hourly in the summer of 1974 and TOC analyzed. The record is shown in
Figure 4.9. The mean and variance were calculated to be 70.56 mg/L and
2 2
1262.07 mg /L respectively. Determine the optimal sampling frequency for
this plant.
The power spectrum corresponding to the record of Figure 4.9 is obtained
as depicted in Figure 4.10. This power spectrum exhibits a significant peak
at the 1/24 hour frequency and a less significant peak at 1/8 hour. Most of
the variability on the data occurs in the frequency band from 1/48 hour to
1/16 hour. Since the last significant peak in the spectrum occurs at the
1/8 hour frequency, the sampling frequency which should be at least two
times the frequency of the last significant peak, corresponding to the
Nyquist frequency, should be at least 1/4 hour. In order to clearly show
the 1/8 hour variability a sampling interval of 3 hours or even 2 hours is
recommended in accordance with the second rule of thumb. Note that this
example, the first rule of thumb stated in Section 4.1.2.2 is violated as
the length of the record in Figure 4.9 (7 days) is less than 10 times the
longest period of interest (one day). However, the peak at the 1/24 hour
frequency is so significant that it cannot be explained by aliasing
distortion alone.
144
-------
oo
s
N-X
c
o
•H
S
(U
o
c
o
200 _
70.56 mg/1
1262.07
o
o
H
100
Tues Wed Thur Pri
Sun
CM
00
6
0!
4-1
Cti
•H
4-1
CO
w
I
M
4J
O
0)
cx
i-l
01
Figure 4.9 Time record of TOC of municipal wastewater at
Racine, Wisconsin
Frequency 1/hour
Figure 4.10 Power spectrum of TOC concentration of municipal waste-
water at Racine, Wisconsin
145
-------
Example 2:
The power spectra of wastewater variation corresponding to two
typical types of industrial discharges are shown in Figures 4.11 and 4.12.
Determine the optimal sampling frequency.
The spectrum of Figure 4.11 exhibits two strong peaks in the frequency
band from 1/16 hour to 1/5 hour. This spectrum is typical for industrial
plants working 24 hours a day, seven days a week, with three shifts a day.
Note the absence of peaks on the low frequency region reflecting the absence
of uniform, short-period cycles in the record, which would then appear to be
random. Inasmuch as the last significant peak occurs between the 1/6 hour
and 1/5 hour frequency, a sampling frequency of 1/2 hour is recommended
(that is, 2 times 1/4 hour).
The spectrum of Figure 4.12 displays a strong peak at the 1/24 hour
frequency and less significant peaks at the 1/12 hour and 1/6 hour
frequencies. This spectrum is typical /or industrial plants working with
one daily shift. Here again, the absence of peaks in the low frequency
region of the spectrum is an indication of the randomness of the record for
short periods in the data. In order to clearly exhibit the 1/6 hour
frequency component of the .data a sampling interval of 2 hours is
recommended in accordance with the second rule of thumb.
4.4 DETERMINATION OF PARAMETERS TO MONITOR
There are two statistical methods to help determine the parameters to
monitor if prior regulations do not exist. The decision variable for the
first method is the probability of exceeding a standard and the second is
the correlation between parameters.
4.4.1 Probability of Exceeding a Standard
This method requires knowledge of:
1. The mean, y , or sample mean, X"
2. The standard deviation, a , or sample S.D., S
P\
3. The standard, X , not to be exceeded for the parameter.
For normally distributed data, the probability of exceeding the standard is:
P(X > Xs) = P(Z > Za ) = a
where: Za = s " ^
After computing Za , the probability, a , can be found in Table 4.8.
Parameters with the largest value of a have the highest sampling priority.
146
-------
3
O
OJ
+->
to
u
0)
0.05
0.10
0.15
0.20
0.25
Frequency (I/hour)
Figure 4.11 Power Spectrum of Industrial
Plant Discharge, Case 1
O
-C
X
CO
X
CJ
VO
O
O
O)
a.
0.05
0.10
0.15
0.20
0.25
Frequency (I/hour)
Figure 4.12 Power spectrum of industrial
plant discharge, Case 2
147
-------
Example 1:
The effluent standard for an industry was determined to be 100 mg/L of
Cl~, Experience has shown that the mean concentration of chlorides is 75
mg/L and standard deviation is 18 mg/L.
To determine the probability of the standard being exceeded:
1. Determine Za = Xs " u = 1QQ " 75 = 1.39
0 18
2. Find a from Table 4.8 such that Z = 1.39. The value is 0.0823, or
8.23%.
Often effluent standards will be specified for several parameters. Then
the parameters can be ranked in descending order of their probability of
exceeding the standard. The priority of sampling will be in the same order.
Table 4.11 is an example of how this is done.
Example 2:
The standard for another parameter is four parts per million. The
average in the past was found to be 7 ppm, with a standard deviation of 2
ppm.
Here:
and so: Z = Xs " u 4 " 7 = - 1.5
a - _ — _ -
a £
Because of symmetry, P(Z <-Za) = P(Z > Za), and so, since Za = - 1.5 in
this case, look up +1.5 in the table, finding a = 0.0668. Since P(Z> -Z }
is desired, use the fact that P(Z >-Z0) = 1 - P{Z > -Z0) = 1 - a. So the
probability of exceeding the standard is 1 -a = 1 - 0.0668 = 0.9332, or
about 93.3%.
4.4.2 Correlation Between Measured Parameters (15)
Ideally, all important water quality parameters should be monitored, but
since this is usually not economically feasible, a method is needed for
deciding which parameters to omit. This is done by checking the closeness of
correlation among parameters of interest. It is known that a correlation
exists between many water quality parameters such as:
148
-------
TABLE 4.11 SAMPLING PRIORITIES OF PARAMETERS FOR A TYPICAL WASTEWATER
UD
Parameter
PH
TOC
COD
BOD
TKN
Phosphates
Conductl bity
Total dissolved
solids
Suspended Solids
Turbidity
Lead
Mercury
Iron
Copper
Alkalinity
Acidity
Calcium
Hardness
Magnesium
Total col i forms
Fecal coliforms
Chlorides
Water Quality
Standard, Xg
6.5 - 8.0
None
70
30
5
1
None
500
30
20
5
5
10
7
None
None
None
None
None
100
10
200
Mean, X
7.8
31
§0
20
3.5
0.5
320
491
28
19
3
2.5
' 7.8
0.8
-_
—
__
__
-_
81
5
156
Standard
Deviation, S
0.4
7.9
11
8
1.5
0.2
80
125
5
3
1.0
1.5
1.9
0.15
—
—
-_
-_
—
65
64
59
Z
0.50
__
0.91
1.25
1.00
2.50
--
0.072
0.40
0.33
2.0
1.67
1.16
1.33
—
-_
__
__
0.29
1.25
0.90
P(X > xs)
0.308
0
0.181
0.125
0.158
0.006
0
0.472
0.34
0.37
0.0228
0.047
0.123
0.0918
0
0
0
0
0
0.386
0.125
0.134
Sampling
Priority
5
16 - 22
7
9-10
8
15
16 - 22
1
4
3
14
13
11
12
16 - 22
16 - 22
16 - 22
16 - 22
16 - 22
2
9 - 10
6
-------
BODg and TOC
COD and TOC
Chlorides and Conductivity
Total Dissolved Solids and Conductivity
Suspended Solids and Turbidity
Acidity, Alkalinity and pH
Hardness, Calcium and Magnesium
Hardness and Alkalinity
If a strong correlation exists between two or more parameters, the
monitoring of one parameter may be discontinued or monitored at a reduced
frequency. In order to apply the technique, the following must be
available:
1. A data record for all parameters of interest
2. A computer program for calculating correlation coefficients.
The relationship between two variables X and Y can be linear or non-linear
(such as exponential, logarithmic or random). If a non-linear relationship
exists, attempt to linearize the relationship, by using logarithms of the
values of X and Y, or some other functional approximation. Then^linear
regression analysis provides a linear approximation of the form Y = a + bX.
The coefficient of correlation, Ryy, will then be a measure of the closeness
of fit. The coefficient of correlation is determined from the equation:
£ (X- - X)(Yi -Y)
N
(x. -
1/2
Numerous computer package subroutines are available for the above analysis.
The hypothesis that a relationship exists between X and Y can be tested
at a given level of significance a (where 1 - a is the confidence that the
hypothesis is true). If the obtained coefficent of correlation is such that
RW! >R^» where R,, is the minimal correlation coefficient, which can be
AT 1C C
found in Table 4.12, the null hypothesis (that the correlation is zero) is
rejected.
If a pair of parameters has a correlation coefficient significantly
greater than the value from the table, one parameter in the pair is eligible
for elimination from or reduction of monitoring. The decision on which a
parameter should be eliminated will be based on the cost of data aquisition
and the priority of the parameter.
Example:
A wastewater system was surveyed for an extended period of time. As a
150
-------
TABLE 4.12 VALUES OF CORRELATION COEFFICIENT, p, FOR
TWO LEVELS OF SIGNIFICANCE (16)
Degrees of Freedom -
. n = N - 1
1
2
3
4
5
6
7
8
9
10
11
12
13
14 .
, 15
16
17
18
19
20
21
22
23
24
25
30
35
40
45
50
60
70
80
90
100
125
150
200 ,
300
400
500
Percent Level
Five
0.997
0.950
0.878
0.811
0.754
0.707
0.666
0.632
0.602
0.576
0.553
0.532
0.514
0.497
0.482
0.468
0.456
0.444
0.433
0.423
0.413
0.404
0.396
0.388
0.381
0.349
0.325
0.304
0.288
0.273
0.250
0.232
0.217
0.205
0.195
0.174
0.159
0.138
0.113
0.098
0.088
of Significance, a
One
1.000
0.990
0.959
0.917
0.874
0.834
0.798
0.765
0.735
0.708
0.684
0.661
0.641
0.623
0.606
0.590
0.575
0.561
0.549
0.537
0.526
0.515
0.505
0.496
0.487
0.449
0.418
0.393
0.372
0.354
0.325
0.302
0.283
0.267
0.254
0.228
0.208
0.181
0.148
0.128
0.115
151
-------
result of the survey, 25 sets of wastewater quality data were gathered.
Each set contained data on pH, TOC, COD, BOD, TKN, phosphorus, conductivity,
total dissolved solids, suspended solids, turbidity, lead, mercury, iron,
copper, alkalinity, acidity, hardness, calcium, magnesium, coliform
bacteria, fecal coliform and chlorides.
1. Determine the sampling priority of each parameter.
2. Determine which parameter measurements can be eliminated or reduced.
First, the probability exists that a parameter will exceed its standard.
This will determine the sampling priority of the standard.
The correlation analysis of the 22 parameters in Table 4.11 was
performed by a computer, using the formula given previously. From Table
4.12, it was determined that:
„ 0.388 for a = .05
Kc " { 0.496 for a » .01
[able 4.13 shows the results of the analysis.
Sampling for total dissolved solids (TDS) has the highest priority, but,
because of the high correlation between TDS and conductivity, analyses for
conductivity need not be considered. Total coliforms have the second
highest priority, but since the correlation between total and fecal
coliforms is high, analyzing for fecal coliforms is not necessary. The high
correlation among BOD, COD and TOC makes it possible to eliminate or reduce
one or two of them. Testing for turbidity could also replace that for
suspended solids. It is also possible to eliminate at least one analysis
from the group hardness, coliform and alkalinity. Metals have relatively
low priority and so at least one of them can be reduced. Thus, the
following streamlined program is feasible:
Parameter
pH
TOC .or COD
BOD
TKN
Phosphates
Total Dissolved Solids
Suspended Solids or Turbidity
Lead
Mercury
Iron
Copper
Alkalinity
Hardness
Total Coliforms
Fecal Coliforms
Priority of Sampling
high
high
reduced
high
reduced
high
high
reduced or not necessary
reduced or not necessary
reduced
reduced or not necessary
reduced
reduced
high
reduced or not necessary
152
-------
TABLE 4.13 MATRIX OF CORRELATION COEFFICIENTS
tn
CO
Parameter
pH
TOC
COD
BOD5
TKM
Phosp
Conduct
fDS
ss
Turb
Pb
Hg
Fe
Cu
Alk
Acid
Ca
Hard
Mg
T. Coll
F, Coll
Chlor
PH
0
0
0
0
0
0
0
0
0
0.18
0
O.I
0
0.6
0.6
0
0.1
0
0
0
0
roc
—
0.8
0.68
0
0
0.30
0.25
0.25
0.4
0
0
0
0
0
0
0
0
0
0.31
0.10
0
COD
—
0.63
0.15
0.18
0.41
0.35
0.40
0.51
0
0
0
0
0
0
0
0
0
0.35
0.18
0
BODs
—
0.18
0.21
0.35
0,48
0.38
0.33
0
0
0
0 •
0
0
0
0
0
0.38
0.21
0
TKN
—
0,69
0.33
0.41
0.25
0.18
0
0
0
0
0
0
0
0
0
0
0
0
P
__
0.17
0.20
0.75
0.68
0
0
0
0
0
0
0
0
0
0
0
0
Cond
—
0.91
0.10
0.18
0.28
0.30
0.41
0.30
0.38
0.20
0.31
0.61
0.40
0
0
0.58
IDS
—
0.18
0.59
0.31
0.23
0.39
0.25
0.41
0.15
0.35
0.68
0.31
0
0
0.88
ss •
—
0.89
0.18
0.25
0.58
0.31
0
0
0
0
0
0.12
0.11
0
f
—
0.15
0.31
0.61
0.25
0
0
0
0
0
0.11
0.08
0
Pb
—
0.70
0.18
0.69
0
0
0
0
0
0
0
0
Hg
—
0.23
0.59
0
0
0
0
0
0
0
0
Fe
—
0.41
0
0
0
0
0
0
0
0
Cu
—
0
0
0
0
0
0
0
0
Alk Ac Ca Hard Mg Tc FC Cl
—
0,49 —
0.65 0
0.61 0.18 0.88 —
0.18 0 0.35 0.18 --
00000 —
0 0 0 0 0 0.79 —
0000000 —
Q •= no engineering relevance; assumed no relation.
-------
4.5 IN-PLANT SAMPLING AND NETWORK MONITORING
If the sampling locations have not been predetermined, there are
systematic methods of determining the location of sampling points. However,
these methods are only tools to aid sampling personnel and do not replace
professional judgment and experience.
4.5.1 Segmentation - Priority Technique
This technique can be applied to any large flowing network including an
industrial plant collection system, a municipal sewerage system, or even a
watershed network. To apply this technique the following information must
be known at a node j between segment points A and B:
1. The mass flow rate of the parameter of interest (Q. C.)»
where Q = volumetric flow rate, C = concentration1-1 J
2. The range of variation of the parameter input p. = (Q. C.) max -
(Qj Cj) min.
3. The approximate frequency of the fluctuations, P.
j •
4. Values for the coefficient of transformation through each
segment SAB
5. Values for the reduction in variation through each segment, ano*
Segmentation of the system is done by first isolating the locations
which modify the waste stream condition, such as junctions of wastewater
treatment units, overflows, stormwater inflow, sidestreams, or lateral
sewers. An example of a municipal wastewa-ter system segmentation is shown
in Figure 4.13. The system has 16 segments, 12 inside the waste system and
four on the receiving water body. In an ideal situation, sampling stations
can be located in all segments of the system. With a limited budget,
however, the number of sampling points will be limited. Therefore, there is
a necessity for a measure to establish priorities of sampling for each
segment. The measure can be the correlation coefficient between the
segments. If a high correlation exists for the measured parameter between
two segments, one can rely on measurement of the parameter in only one
segment and sampling of the other segment is not necessary. Unlike the
large river monitoring systems, wastewater systems have at least one fixed
location of a monitoring point, such as the influent and/or effluent of a
treatment plant. Using the correlation analysis between the monitored
segment and other upstream and downstream segments, it is possible to
identify segments with low correlation to the monitored segment. A second
consideration should be the worth of the data measured at the segment. For
example, if the magnitude of a measured parameter and its variability are
insignificant when related to other segments, the segment will have a low
priority for monitoring.
4.5.1.1 First Priority Sampling Points
The location of at least one sampling point is strictly determined by
the basic objectives of a monitoring program, i.e. protection of the
154
-------
Plant 1
in
tn
Storm
Water
Plant 2
Water
Intake
13
Plant 3
14
7 J',
Sanitary Waste
Treatment
Plant
10
12
Bypass
15
16
11
Figure 4.13 Segmentation of a wastewater system
-------
environment. This objective requires that a sampling point be located just
before a wastewater discharge to a receiving water body. If the industry
has several wastewater outfalls, a sampling point should be located
downstream from the last outfall. In the case that the monitoring point is
located in the receiving water body, an upstream station to monitor the
upstream water quality and quantity is necessary. This will allow the
effect of the wastewater discharge on the receiving water body to be clearly
identified. If the water intake for the industry is situated on the same
water body, the upstream sampling point can be conveniently located at the
water intake.
4.5.1.2 Second Priority Sampling Points
Other important objectives of a sampling program can be to monitor the
quality of raw wastewater and to evaluate the efficiency of a treatment
process. Thus, a location for a second priority sampling point would
normally be at the influent to a treatment plant.
For small and medium sized wastewater systems, sampling at the first
and second priority sampling points should be sufficient to meet most of the
objectives and requirements established by regulatory agencies.
4.5.1.3 Third Priority Sampling Points
The location of additional sampling points may be necessary for large
wastewater systems with many inputs. Their purpose is to provide additional
information or warning. In this case, the method of segmenting the
wastewater system and determining sampling priorities for each segment can
be of use in establishing additional sampling points. Segmentation of a
wastewater system is accomplished by isolating the locations which
substantially modify the waste stream conditions. These locations include
junctions of wastewater streams, treatment units, wastewater overflow, flow
dividers, storm and cooling water inflows, and storage reservoirs. The
following outlines a method of segmentation.
1. It is best to represent the wastewater system by a linear graph
technique. Such a graph consists of nodes or junctions and
branches or lines. All wastewater inputs will enter the system
through the nodes, and the nodes also separate branches with
different characteristics. A branch is considered as a segment
with uniform geometric, hydraulic, and transform characteristics.
The following depicts the classification of some typical elements
of a wastewater system.
Nodes - manholes, changes of slope, changes in conduit diameter,
flow dividers, junctions of sewers and channels, outfalls,
influents and effluents to treatment steps, etc.
Branches - conduits, channels, treatment steps, bypasses, adjacent
receiving water bodies, storage reservoirs, holding ponds, and so
on.
For the industrial water/wastewater system of Figure 4.14, a linear
156
-------
INW
SEDIMENTATION
AND
NEUTRALIZATION
SANITARY
WASTE
SANITARY
WASTE
FLOATATION
AND TOXICITY
REMOVAL
QUALIZATIOI
AND
STORAGE
BIOLOGICAL
TREATMENT
PLANT
SLUDGE
SOLIDS
EFFLUENT
MONITORING
Figure 4.14 An industrial water/wastewater system
-------
U1
oo
(V-*\) Segment - Sewer _/}_ Node
W ^ or Channel W
Segment - Treatment^ j Wastewater Input
-..Primary Sampling Segment]
S h-*~Secondary Sampling Segment
Figure 4.15 Linear graph representation of the system
-------
graph representation is shown in Figure 4.15.
In segmenting the system, each node should be uniquely numbered.
Wastewater input to each node should be characterized by the range
of variation:
Pj = (Qj C..) max. - (QjC..) m1n.,
which is, basically,, the range of waste loads to the node j.
The units of P. will be g/sec if the flow Q is expressed in
3 ^
m /sec and concentration C in mg/L. It might be convenient also
to know the approximate frequency of fluctuations of the input P..
A node table should be prepared such as is shown in the following
example (Table 4.14).
3. Each branch is identified by a double subscript AB, where A is the
number of the upstream node and B is the number of the downstream
node.
Coefficients of transformation B ,g and a.g should be assigned for
each branch. The coefficient of transformation B.R describes
roughly how the variability of the wastewater is reduced in this
segment. In most cases BAD can be determined approximately from
the geometry of the segment and treatment parameters. The
coefficient «. describes how the correlation is reduced in the
segment. The following values of the coefficients are recommended:
Let PAB = Let aAB =
Short sewers and channels ' 1.0 1.0
Plug flow treatment steps,
long sewers and channels exp(-KT) 0.9 to 1.0
with decay
Completely mixed treatment
steps with short detention 1-E. /100 0.85 to 0.95
time (t« 1/f) Tr
Completely mixed treatment f 1 i 4
steps with long detention 2(l+Kt)tf "2 (2tf)"*
time (t» 1/f) v ;
Storage and equalization , ,
reservoirs and holding (2tf)~* (2tf)~
ponds with no decay
159
-------
where:
K = decay coefficients in the segment (in units of day ~ )
t = detention time in the segment (in days)
f = frequency of fluctuations of waste inputs
E. = treatment efficiency (in percent)
Determine and approximate ranges of wastewater quality variations
for each segment. This can be done by starting at the most
upstream nodes containing wastewater inputs and moving downstream,
by the buffering capacity of segments and by new wastewater inputs
(such as process discharges) in downstream nodes.
Figure 4.16 illustrates how this procedure is accomplished. JK is
the most upstream node containing a wastewater input and would
therefore be the starting point. The range of wastewater
variability will be
r,., = P. where r,K is the wastewater quality
variation range in segment JK downstream from J. Above, the
downstream node K the variation range is determined by
r = r x 8
rJK rJK x PJK
At a node the variability range can be changed by wastewater inputs
to the node and by other upstream branches entering the node. For
a case where more than one input enters a node, the following
relationship (propagation of errors) can be used to compute the
variability range:
.2
A
AB
A
)
where A denotes the node under consideration, B denotes the node
immediately downstream from A, iA represents the i— upstream
branch entering node A, and jA represents the j — wastewater input
entering node A. In Figure 4.16, the above formula is used for
node L.
The variability ranges for all segments in a network can be
computed using the relationship described above and shown in Figure
4.16. It is recommended that the variability range be checked by
known data from a survey or monitoring. The above procedure should
give adequate results assuming that all inputs to the system are
random and uncorrelated to each other.
160
-------
Variability Range
f . \ J
V
VrJK
PJK
K
k rJK
C K )
( 1 )
V
p— -M
K
rKL
L PKL
VKL
I""7 L
1
^^J
fLM
PLM
fM ) M
^1
rMN
X
1
PMN
Monitoring (fT\
Point V y
J
rJK
K
rJK
K
rKL
L
rKL
L
rLM
+ (P
M
rl_M
= PJ
J
= rJKX
K
= rJK
K
~rKL
L
= [(rK
L)211/2
L
~rLM
Figure 4.16 Estimation of variability and correlation in segments
161
-------
5. Determine the approximate correlation coefficient between each
segment's water quality variations and variations in the monitored
segment. The correlation coefficient, MM, for the monitored
segment itself equals 1.0. Moving further downstream or upstream
causes the correlation coefficient to decrease as the relation
between the wastewater fluctuations in the monitored segment and
the segment downstream or upstream diminishes. The change in the
correlation coefficient can be roughly estimated as follows:
In a Branch - multiply P by the coefficient
R / R
In a Node - multiply p by the ratio r,,n
where B is the node under consideration, AB is the branch located
farther away from the monitored segment, and BC is the branch
located closer to the monitored segment.
6. Additional sampling points should be located at the segment where,
theoretically, the correlation with the monitored point ends.
Since the correlation influence of both points extends both down
stream and upstream, there will be an overlap such that each
sampling point will have an influence of r = t/~%l, where R is the
critical point found in Table 4.12. If the number of samples is
now known, a value of R between 0.25 and 0.30 will give a good
estimate.
7. If there are several segments to be monitored, that is, one or more
segments have a correlation level less than R , the priority can be
determined according to the magnitude of the variability range r. .
' \J
for the segment ij. The segment with the highest r.. will have the
highest priority. 1J
8. Once a new sample location is established, the procedure is
repeated to find the next sampling location.
9. The entire procedure should be repeated for each important
parameter.
Example:
Determine the locations of sampling points for the wastewater system
given in Figure 4.14. The analysis will be based on the COD information
representing the organic load to the system.
Step 1 - Divide the system into segments using the linear graph representa-
tion, as in Figure 4.15.
162
-------
TABLE 4.14 .WASTEWATER LOADS TO NODES
CONSTITUENT: COD
Node Maximal Loading Minimal Loading Pj
g/sec g/sec
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0
0
0 . • •
0
10
0
30.0
0
o -• , . •
175.0
0 • .-: •
0
66.0
109.0
0
0 .
42.0
121.50
0
0
0
0
1.2
0
6.0
0
0
100.0
0
0
17.0
21.0 '
0
0
23.0
93.0
0
0
0
0
8.8
0
24.0
0
0
75.0
0
0
49.0
88.0
0
0
19.0
28.5
Fluctuations of maximum and minimum at most nodes - 1/8 hours"
TABLE 4.15 COEFFICIENTS OF VARIATION IN BRANCHES
Branch Description
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-11
5-12
12-13
13-14
14-15
7-16
16-17
17-18
16-19
Effluent Channel
Activated Sludge Plant
Equalization Basin
Sewer
Sewer
Sewer
Sewer
Sewer
Neutralization Plant
Sewer
Sewer
Floatation Unit
Sewer ; . •
Sewer
Sewer
Sewer
Chemical Coagulation
Sewer
1.0
0.1
0.2
1.0
1.0
1.0
1.0
1.0
0.9
1.0
1.0
0.5
1.0
1.0
1.0
1.0
0.7
1.0
1.0
0.4
0.2
1.0
1.0
1.0
1.0
1.0
0.9
1.0
1.0
0.5
1.0
1.0
1.0
1.0
0.7
1.0
163
-------
Step 2 - Locate a first priority sampling point (P) at the effluent channel
(segment 1-2). Locate second priority sampling points (S) at the
influent to the treatment plant (segment 4-5) and in the receiving
water body, upstream and downstream from the waste discharge.
Step 3 - Estimate the variability range of the inputs to the system (Table
4.14).
Step 4 - Estimate B and a for each segment (Table 4.15).
Step 5 - Estimate the variation range in each segment. Proceed upstream
from the most downstream segment (Table 4.16).
Step 6 - Estimate the coefficient of correlation between wastewater
variations in each segment and the nearest monitored segment to
segment 4-5. Proceed from the monitored segment (where R = 1,0)
and work upstream (Table 4.16 right portion). Each segment is
correlated to the segment immediately downstream toward the
monitored point. Developing a correlograph (Figure 4.17) at this
stage will aid in the decision process in Step 7.
Step 7 - Once the correlation coefficients are estimated, find those where
R.< R , with R estimated to be 0.30. Based on this criterion, the
\* Xj
priority for monitoring the upstream segments will usually have a
high correlation and, therefore, only one segment needs to be
monitored. The second criterion is the magnitude of the
variability, r.., for the segments with low correlation levels.
* w
Both the values of R and of r.- should be examined for these
* U
segments, the requirements and objectives of the program should be
considered, and then professional judgment must be exercised.
In this example, segments 17-18, 16-17 and 16-19 are neighboring
segments with low correlation levels. Looking at the variability
values, it is obvious that segment 16-19 has the highest value,
indicating the great fluctuations in wastewater quality. Therefore,
of these three, segment 16-19 might have the highest priority.
Segments 14-15, 13-14 and 12-13 are also neighboring segments with
low correlation levels. Segment 13-14 has the greatest variability
and would therefore be chosen. Since its variability is much
higher than that of segment 16-19, it would have the highest
overall priority. At this stage, correlation and variability
values can be recalculated to see if monitoring at these points
would satisfy the program requirements. If not, the procedure
should be repeated.
4.5.2 Probability of Exceeding aStandard (17)
In locating sampling points in a receiving water body, the probability of
exceeding a receiving water standard should be considered. For all
conservative substances and all nonconservative substances except oxygen and
possibly temperature and nitrates, the critical section would be located
immediately downstream from the outfall. The section with the highest
probability of violating the dissolved oxygen standard will be further
downstream near the "sag point". The location of the critical point can be
164
-------
TABLE 4.16 DETERMINATION OF THE SAMPLING PRIORITIES OF SEGMENTS
Segment
16-19
17-18
16-17
7-16
10-11
9-10
8-9
7-8
6-7
5-6
14-15
13-14
12-13
5-12
4-5
Upstream variation range
28.5
19.0
13,3
(28.52 + 13.3')0-5 =31.45
75
75
67.5
(67.52+242)°-5=71.64
(71.642 +31.452)0-5 =78.24
(7S.242 +8.82)0-5 =78.73
88.0
(882+492)0-5 =100.72
100.72
50.36
(78J32 +50.362)0-5 =96.12
Downstream variation range
rd " ru * 0
28.5
19 » 0.7 = 13.3
13.3
31.45
75
75 * 0.9 = 67.5
67.5
71.64
78.24
78.73
88.0
100.72
100.72 "0,5 = 50.36
50.36
96.12
Correlation coefficient
at the downstream node
0.33*28.51/31.45 = 0.30
0.14
0.33* 13.3/31.45 = 0.14
0.81 '31.45/78.24 = 0.33
0.63
0.70
0.75 * 67.6/7 1.64 = 0.70
0.81 * 71. 64/78.24 = 0.75
0.82 '78.24/78.73 = 0.81
1.0 '78.73/96.12 = 0.82
0.26*88/100.72 = 0.23
0.26
0.52
1.0 '50.36/46.12 = 0.52
1.0
in the branch
at the upstream node
0.30
0.14 0.7 = 0.10
0.14
0.33
0.63
0.7 * 0.9 = 0.63
0.70
0.75
0,81
0.82
0.23
0.26
0.52 * 0.5 = 0.26
0.52
1.0
Priority for
tertiary monitoring
T2
T3
T1
Initial segment
monitoring
-------
15
en
N_
S = Monitored segment
' If >2f ' 3 =
First, second, third
priority segments ^J
rp = 0.23
r = 88
r,. HB
>v ~
7\ for monitoring 0^) ^xl '!
J
/""N
M9)
p = 0.63 S
„ „. TC
SV75
°J
p - 0.63 v
v<
r
p = 0.30 T3
r.. = 28.5
J* M! ^ *
I r..- 87.5 W V7)
K'J ^
r
p = 0.70
r.. = 67.5
p = 0.14 p = 0.
-s_
J*~
*p = 0.26
r..= 100.72
ij
•"*»*.
(13)
V.
fp = 0.26
r. = 50.36
10 fa
r..= 13.3 r..= 13.3 \^S
ij ij
p = 0.33
r:. = 31.45
b O'J (
p = 0.75 ^p = 0.81
r.. = 71.64 r.. = 78.24
U U
p = 0.52
r.. = 0.52
tj
TN (A) G)
^p = 0.82 p^1.0 1
r.. = 78.73 r- = 96.12[_ Monitored
U U •— ) b [ segment
Figure 4.17 Correlograph for segments
-------
approximately evaluated as follows:
The probability that the dissolved oxygen standard will be exceeded is;
P(C< Cs) = P(D> Ds) - P>Z ^Zs = PS - D^T 1
which can be found in Table 4.9, where:
C is the dissolved oxygen concentration
C is the dissolved oxygen standard
D is the oxygen deficit
D is the maximum allowable oxygen deficit
D(x)
K2"K1
exp
.K Y
*l\1 A
exp
u
exp
'/
which is the average oxygen deficit at distance x from the outfall S(x)
A, x S. x u is the standard deviation at distance x. (15 to 17)
17 is the average BOD discharge
SL is the S.D. of the BOD discharge
K, is the coefficient of deoxygenation
K? is the coefficient of re-aeration
D is the initial oxygen deficit
u is the stream velocity
^1 f i ^lx i /-KoX
Ai = i^[exprir/"exptir
To find a maximal P(C < C ), it is sufficient to find a location x such
that Z = (D - D(x))/S(x) is a minimum. This can be accomplished by
finding the location x at which D(x)/S(x) is a maximum (and so P(D(x) > D )
is a maximum. The distance x can be found by plotting D(x)/S(x) against x
for given K,, K2, DQ, L and u, and then finding the x value corresponding
to the highest value of DTx7/S(x).
167
-------
4.6 REFERENCES
1. Haber, Audrey and Richard P Runyon. "General Statistics". Reading,
Massachusettes Addison-Wesley, 1969.
2, Bendat, J. S. and A.G. Peirsol. "Random Data: Analysis & Measurement
Procedures". New York, Wiley-Interscience, 1971.
3. Dixon, W.J. "BMD Biomedical Computer Programs. University of California
Press. Berkley, California 1973.
4. Barr, A.J., J.H. Goodnight, J.P. Sail, and J. T. Helwig. "Spectra
Procedure, in a User's Guide to SAS 76". SAS Institute, Inc. Raleigh,
North Carolina., 1976.
5. Hogg, Robert V. and Allen T. Craig. "Introduction to Mathematical
Statistics, 3rd Edition". London, The Macmillan Company, 1970
6, Foster, H.A. "Theoretical Frequency Curves and Their Application to
Engineering Problems". Trans. ASCE Paper, 1523, p. 142-173, 1924.
7. Associated Water & Air Resources Engineers, Inc. "Handbook for
Industrial Wastewater Monitoring". U.S. EPA Technology Transfer, 8-8
to 8-12, August 1973.
8. Sparr, T.M. and R.W. Hamm Jr. "Variations of the Municipal Waste
Effluent Quality and the Implications for Monitoring". Proc. of the
International Seminar and Exposition on Water Resources
Instrumentation, Chicago, June 4-6, 1974 Water Resources
Instrumentation, Volume 1: Measuring and Sensing Methods". Ann Arbor
Science Publishers, Inc. Ann Arbor, Michigan, 1974.
9. Owen, Donald, B. "Handbook of Statistical Tables". Addison-Wesley
Company, Reading, Massachusetts. 1962.
10. Montgomery, H.A.C. and I.C. Hart. "The Design of Sampling Programs for
Rivers and Effluents". Water pollution Control (London, England), 73:
77-98, 1974.
11. Drobny, N.L. "Monitoring for Effective Environmental Management".
Proc. ASCE National Water Resources Engineering Meeting. Atlanta,
Georgia, January 24-28, 1972.
12. Gunnerson, C.G. "Optimizing Sampling Intervals". Proc. IBM Scientific
Computing Symposium, Water and Air Resources Management. White Plains,
New York, 1968.
168
-------
13. Sparr, T.M. and P.O. Schaezler. "Spectral Analysis Techniques for
Evaluating Historical Water Quality Records". Proc. of the
International Seminar and Exposition on Water Resources
Instrumentation, Chicago, June 4-6, 1974. Volume 2: Data Acquisition
and Analysis. Ann Arbor Science Publishers, Inc. Ann Arbor Michigan,
1974.
14. Wastler, T.A. "Application of Spectral Analysis to Stream and Estuary
Field Studies". U.S. Department of HEW, Cincinnati, Ohio, p 27,
November, 1963.
15. Kaester, R.L., J.J. Cairns, and J.S. Grossman. "Redundancy in Data
from Stream Surveys". Water Research. 8^: 637-642, August 1974.
16. Fisher, R.A. and F. Yates. "Statistical Tables for Biological,
Agricultural and Medical Research". London, Oliver and Boyd, 1949.
17. Chamberlain, S.G., C.V. Beckers, G.P. Grimsrad, and R.D. Shull.
"Quantitative Methods for Preliminary Design of Water Quality Surveillance
Systems". Water Resources Bulletin, 10: 199-219, April, 1974.
169
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CHAPTER 5
SAMPLING MUNICIPAL WASTEWATERS
5.1 BACKGROUND
Municipal wastewaters are collected and treated by chemical, physical,
and/or biological means prior to discharge to surface waters. Up to three
stages, primary, secondary and tertiary, are commonly used at municipal
treatment plants.(1) The wastewater characteristics vary with the size and
habits of the community, the type of collection system (combined or
separate), the amount of infiltration and the volume and type of industrial
discharges entering the system.
5.2 OBJECTIVES OF SAMPLING PROGRAMS
5.2.1 Regulatory
Sampling of municipal wastewaters is required by regulatory agencies
for the NPDES permit program. The location of sampling points, frequency,
sample type, and the like are specified in the NPDES permit.
5.2.2 Process Control
In addition, sampling is performed at municipal treatment plants for
process control. This monitoring provides a check on the efficiency of the
process allowing the operator to make adjustments to optimize the process
efficiency.
5.2.3 Research and Development
The special needs of research projects dictate the sampling
program. Each project must be considered individually and no general
guidelines can be given.
5.3 FREQUENCY OF SAMPLING
5.3.1 Established by Regulation
Follow the frequency requirements in the permit issued by the
regulatory agencies.
170
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5,3.2 Use of Statistics
Apply spectral analysis techniques (Section 4.3.1) to establish the
optimum frequency. If the data required for this technique are not
available;
1. Conduct a week-long survey collecting hourly samples. For combined
municipal and industrial wastewaters choose a week of high
industrial production.
2. Determine if any unusual industrial or community discharge occurred
during the sampling period, for example, an extensive spill or
extremely heavy rainstorm, which may invalidate the data and
necessitate a repeat of the survey.
After data collection, the analysis of data should be performed as
outlined in Section 4.3.1.
5.3.3 Compliance Purposes
The NPDES Compliance Sampling Manual (2) indicates that sampling
programs must include a minimum of a 24 hour of operating day composite
supplemented by two or more grab samples. With highly variable wastewater
characteristics or flow rate changes, additional sampling is required. A
composite sample is defined as a minimum of eight discrete samples taken,
proportional to flow rate, over the compositing period.
5.3.4 Other Considerations
Follow interim sampling frequencies prior to the generation of data for
statistical analysis. Frequencies appear in Tables 5.1 (3) and 5.2.(4)
5.4 LOCATION OF SAMPLING POINTS
Collect the sample at the location(s) specified in the permit. At
these locations collect the sample in the center of the channel at 0.4 to
0.6 depth where the flow is turbulent, well mixed, and the settling of
solids is minimal. Sampling at 0.4 to 0.6 depth will avoid skimming of the
water surface or dragging the channel bottom.
For BOD analyses, collect the samples prior to disinfection.(5) For
BOD and suspended solids, samples of plant influent and effluent must be
collected In order to calculate the removal of these constituents. The
sampling of wastewater for immiscible liquids, such as oil and grease,
requires special attention and no specific rule can be given for selection
of the most representative site because of wide range of conditions
encountered in the field. In such cases, experience of the sampling team
should be the guide in the selection of the most representative site.(6)
171
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TABLE 5.1 PROCESS TESTING GUIDE5 (3)
Process
Grit
Removal
Primary
Sedimentation
Activated
Sludge
Trickling
Filter
Oxidation
Ponds
Final
Sedimentation
Test
PRETREATMENT
Volatile Solids
Total Solids
Moisture Content
PRIMARY TREATMENT
Settleable Solids
pH
Total Sul fides
Biochemical Oxygen Demand
Suspended Solids
Chemical Oxygen Demand
Dissolved Oxygen
Grease
SECONDARY TREATMENT
Suspended Solids
Dissolved Oxygen
Volatile Suspended Solids
Turbidity
Suspended Solids
Dissolved Oxygen
Dissolved Oxygen
Total Sul fides
Total Organic Carbon
Total Phosphorus
Settleable Solids
pH
Total Sulfides
Biochemical Oxygen Demand
Suspended Solids
Chemical Oxygen Demand
Dissolved Oxygen
Turbidity
MBAS
Frequency
Daily
Dally
Daily
Daily
Daily
Daily
Weekly
Weekly
Weekly
Weekly
Weekly
Daily
Daily
Weekly
Daily
Daily
Daily
Daily
Daily
Weekly
Weekly
Daily
Dally
Daily
Weekly
Weekly
Weekly
Weekly
Daily
Weekly
This is a minimum sampling guide, and is subject to change with plant
site, complexity of operation, and problems encountered.
(continued)
172
-------
TABLE 5.1 (continued)
Process
Test
Frequency
Chi orination
Thickening
Digestion
Centrlfuging
Vacuum Filters
Incineration
Chemical
Coagulation &
Fl peculation
Activated
Carbon
Recarbonatlon
Ammonia
Stripping
Filters
Microscreen
DISINFECTION
Chlorine Residual
MPN Coliform
SOLIDS HANDLING
Suspended Solids
Volatile Solids
Total Solids
Volatile Solids
pH
Gas Analysis
Alkalinity
Volatile Acid
Suspended Solids
Volatile Solids
Sludge Filterability
Suspended Solids
Volatile Solids
Ash Analysis
ADVANCED TREATMENT
Jar Test
Phosphorus Analysis
Apparent Density
COD
TOC
pH
Ammonia Nitrogen
pH
Suspended Sol Ids
Turbidity
Suspended Solids
Chemical Oxygen Demand
Daily
Weekly
Daily
Daily
Weekly
Weekly
Daily
Weekly
Weekly
Weekly
When in Operation
When in Operation
When in Operation
When In Operation
When in Operation
When in Operation
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Weekly
Daily
Daily
Daily
Weekly
173
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TABLE 5.2 RECOMMENDED MINIMUM SAMPLING PROGRAMS FOE MUNICIPAL
WASTEWATER TREATMENT PROCESSES (4)
T«np
pH
BOD
DO
SS
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£ 5
S F S
C
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C
C 3/H C
C
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c
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* C B.
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2/U C 2/U
S/U C 1/D C 1/U
S/U
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1/D
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3/U
3/U
2/U C 2/U
u
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s
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-------
TABLE 5.2 (continued)
1— >
•M
tn
Micro Analysis
Ortho-F
Chlor. lesld.
Collfora
Fecal Collform
ilk.
Jar Test
Hardness
Sludge Vol.
Oil. S
NBAS
Metals
Flant Flow
13
5
"rl
V*
rt U
5 A
1 °
t« «j B
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c a/u
G 3/D
c a/H
C 2/M
B
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f
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ta «
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s £
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•
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u
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u
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M
o
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E
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6
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f AO=»H u»
f
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5.2
j*
m o
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Q C
m <
S F_
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t. S • type of sample
2. F » frequency
C • Cr«b
C - 24 hour compos He
D *> Day
H - Ueek
M • Honth
K • lecord continuously
l%> * Kooltor continuously
-------
5.4.1 Influent
Influent 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. Preferable raw waste sampling
points are:{6)
a. the upflow siphon following a comminutor (in absence of grit
chamber)
b. The upflow distribution box following pumping from main plant wet
well
c. aerated grit chamber
d. flume throat
e. pump wet well
In all cases, samples should be collected upstream from recirculated
plant supernatant and sludges.
5.4.2 Effluent
Collect effluent samples at the most representative site downstream from
all entering waste streams. When manually compositing effluent samples
according to flow where no flow measuring device exists, use the influent
flow measurement without any correction for time lag. The error in influent
and effluent flow measurement is insignificant except in those cases where
extremely large volumes of water are impounded, such as in reservoirs, as a
result of influent surges coupled with highly restrictive effluent
discharge.(7)
5.4.3 Pond Sampling
Composite samples from ponds with long detention times may not be
representative because of the tendency of lagoons to short circuit. If dye
studies or past experience indicate a homogeneous discharge, grab samples
may be representative of the waste stream.
5.4.4 In-PlantLocation
Apply the statistical technique outlined in Section 4.5 to determine
in-plant sampling locations. In addition to these locations, sample all
other unit processes periodically or when the variability of a parameter
adversely affects the efficiency of a unit process.
5.5 NUMBER OF SAMPLES
Use one or more of the following methods to determine the number of
samples:
1. Follow permit requirements by regulatory agencies.
176
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2. Apply statistical methods in Section 4.2 to the data from the
preliminary survey.
3. Use the frequency data to establish number of samples. For
example, one sample every six hours will establish four samples
per day.
5.6 PARAMETERS TO MEASURE
The NPDES permit for each municipal treatment plant dictates the
effluent limitations and monitoring requirements for that particular plant.
For evaluating the plant performance, regardless of the size, BODg, solids,
pH and flow should be monitored routinely.(8)
Secondary analyses may include:
1, Fecal Coliform 8. Chlorine Residual
2. Temperature 9. Dissolved Solids
3. Dissolved Oxygen 10. Alkalinity
4. Total Solids 11. Metals
5. Total Volatile Solids 12. COD
6. Nitrogen Series 13, Oil and Grease
7. Phosphorus 14. Organic Priority Pollutants
as required
Table 5.2 indicates the parameters to analyze the efficiency or the
effectiveness of the various unit processes. Changes are allowed to
compensate for specific plant conditions.
5.7 TYPE OF SAMPLE
Collect composite samples for overall monitoring,(6) and grab samples
for checking individual unit processes. Use one of the following types of
composite samples to properly estimate mass loading:
1. Periodic, time constant, sample volume proportional to stream flow.
2. Periodic, sample volume constant, time proportional to stream flow
since the last sample.
Other composite types may be used if comparable results can be demon-
strated.
5.8 METHODS OF SAMPLING
Choose manual or automatic sampling depending on how the advantages and
disadvantages of the methods apply to the specific program. (Refer to
Chapter 2). Only trained personnel should be entrusted the task of sample
collection. Much of the uncertainty regarding the collection of suspended
solids can be minimized if samples are collected at isokinetic conditions or
177
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at higher intake velocities.
5.8.1 Automatic Sampler
Automatic samplers for municipal wastewaters must be capable of
collecting representative suspended solids samples throughout the collection
and treatment system. While sampler selection will depend on site
conditions, the following guidelines are suggested;
1. For sampling raw wastewater and primary effluent, use a sampler
having an intake velocity greater than 0.76. m/sec. (2.5 ft./sec.).
For sampling a final effluent with no visible solids, a sampler
having a lower intake velocity may be acceptable.(2)
2. To determine the effectiveness of an automatic sampler to collect
suspended solids, statistically compare the suspended solids value
of the composite sample from the automatic sampler with the mean
value of the manual grab samples. The minimum compositing period
should be six hours with a maximum individual sample frequency of
one hour.(7) The ratio of the automatic sampler suspended solids
value to the manual grab suspended solids value varies throughout
the plant. For influent and primary effluent the acceptable ratio
is 1.6 - 2.0 and for the final effluent it is 0.9 - 1.3.(9)
5.9 VOLUME OF SAMPLE AND CONTAINER TYPE
The volume of sample obtained should be sufficient to perform all the
required analyses plus an additional amount to provide for any split samples
or repeat examinations. Although the volume of sample required depends on
the analyses to be performed, the amount required for a fairly complete
analysis is normally 7.57 liters (two gallons) for each laboratory receiving
a sample. The laboratory receiving the sample should be consulted for any
specific volume requirements. Individual aliquot portions of a composite
sample should be at least 100 milliliters (0.21 pints). Depending on the
sampling frequency and sample volume, the total composited sample should be
at least 7.57 liters (two gallons).(6) Use a separate sterilized container
for coliform analysis. See Chapter 12 for trace organic collection methods.
Collect chlorine residual and oil and grease samples in glass containers
with teflon lined lids. Plastic is acceptable for the other inorganic and
general organic analyses. Additional information for sampling organic
parameters is given in Chapter 17.
5.10 PRESERVATION AND HANDLING THE SAMPLES
Follow the guidelines provided in Chapter 17 for the preservation and
handling of samples.
178
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5.11 FLOW MEASUREMENTS
The flow measurement technique selected should be 1n relation to the
sampling location, type of flow, and other similar characteristics. Follow
the guidelines enumerated in Chapter 3 on Flow Measurements. Primary and
secondary flow measurement devices should be calibrated prior to taking flow
measurements.
5.12 REFERENCES
1. Metcalf and Eddy, Inc. Wastewater Engineering. McGraw Hill, New York,
1972.
2. NPDES Compliance Sampling Manual. U.S. Environmental Protection Agency,
Washington, D.C., June, 1977.
3. URS Research Co. Procedures for Evaluating Performance of Wastewater
Treatment Plants. PB 228 849/6, National Technical Information Service,
Springfield, Virginia.
4. Estimating Laboratory Needs for Municipal Wastewater Treatment
Facilities. PB 227 321/7. National Technical Information Service,
Springfield, Virginia.
5. Henderson, P.M. Open Channel Flow. MacMillan Co., New York, 1966.
v
6. Harris D.J. and W.J. Keefer. Wastewater Sampling Methodologies and
Flow Measurement Techniques. EPA 907/9-74-005, U.S. Environmental
Protection Agency, Region VII, 1974. 117 pp.
7. Earth, E.F. U.S. EPA Inter-Office Memo dated August 22, 1975.
8. Water Pollution Control Federation Highlights. Vol. 12 H-I, April,
1975.
9. Comparison of Manual (Grab) and Vacuum Type Automatic Sampling
Techniques on an Individual and Composite Sample Basis.
EPA-330/1-74-001, U.S. Environmental Protection Agency, Denver,
Colorado, 1974. 29 pp.
179
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CHAPTER 6
SAMPLING INDUSTRIAL WASTEWATERS
6,1 BACKGROUND
Industrial wastewaters vary significantly in pollution characteristics.
This chapter presents general guidelines and considerations so that effective
sampling programs can be established for varied situations.
6.2 OBJECTIVES OF SAMPLING PROGRAMS
6.2.1 Regulatory
Sampling of industrial wastewaters is required by regulatory agencies
for the NPDES permit program. The location or sampling points, frequency
and sample type are specified in the NPDES permit. At the time of NPDES
permit modifications, incorporate the recommendations of Compliance Sampling
Inspections.
6.2.2 Process Control
In addition, sampling is performed within the plant to monitor
individual waste streams, as a check on the process efficiencies and to
compute material balances.
6.2.3 Research and Development
The special needs of each research and development project on
industrial waste treatment will dictate the sampling program. No general
guidelines can be given. Projects are normally conducted:(1)
1. To explore potential recovery from a given department or unit
process. Projects consider process modifications and study the
economics of changes.
2. To define factors influencing character of wastes from a given
department or unit process.
3. To investigate and demonstrate variations in the character and
concentration of combined wastes.
4. To establish a sound basis for the treatment of residual wastes.
180
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6.3 FREQUENCY OF SAMPLING
6.3.1 Established by Regulation
Use permit requirements when compliance monitoring is the objective. If
the sampling frequency is not specified by regulation, sampling interval
should be one hour or less, (2) and if data is available use the statistical
methods as a tool to determine the frequency of sampling.
6.3.2 Use of Statistics
Apply the statistics outlined in Section 4.3, to obtain frequency of
sampling whenever possible. Background data must be collected to determine
mean and variance. One of the following procedures can be used to obtain
this information (listed in order of preference) if it has not been
previously collected:
1. Conduct a week long preliminary survey consisting of the hourly
samples to characterize the system.
2. Conduct one 24 hour survey taking hourly samples (as outlined in
Chapter 2). Analyze individual samples if batch dumps are
suspected. Any weekly pattern must be considered and samples taken
on the day of the greatest variation of the parameters of interest.
3. Obtain data from a plant with the same type of industrial operation.
However, where processes differ, take samples to quantify the
variation.
After data collection, use production figures to estimate extreme
values, assuming a linear operating relationship (which is not always the
case).
6.3.3 Other Considerations
Consider variable plant operations when determining frequency:
1. Seasonal operation
2. Less than 24 hour per day operation
3. Special times during the day, week or month set aside for cleanup
4. Any combination of the above
When monitoring these types of operations, it is necessary to sample
during normal working shifts in the season of productive operation. Figure
6.1 gives procedures for the various situations.
6.4 LOCATION OF SAMPLING POINTS
6.4.1 Effluent Monitoring
Regulatory permits establish effluent monitoring points within a plant.
The permit may specify only the total plant discharge or a specific
discharge from a certain operation or operations. Consult permits for these
181
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Plant
Operation
oo
Year round
operation
Less than
2*i hour day
Sample at all
tines with
special empha-
sis on worse
than average
days
Sample
during
working
shifts
Figure 6.1 Factors of plant operation to be considered In
the design of the sampling program*(2)
-------
locations, or use those recommendations for obtaining representative samples
given in Chapter 2.
6.4.2 In-Plant Locations
To achieve process control or to design and implement in-plant pollution
control programs, selection of proper in-plant sample location is important.
Use the following procedures to determine the sampling locations:
1. Become familiar with the plant processes and sources of wastes from
unit operations.
2. Ascertain the sewer layout in the plant. If a sewer plan exists
thoroughly review the sewer plan and examine each sewer to
determine its course and destination. Where a sewer plan is not
available, the only practical way to determine the sewer layout is
by dye-tracing.
3. Determine the exact source and the point at which each waste stream
enters the sewer.
4. Sample each waste stream and plant outfall. By doing so, each waste
stream is charactertized and the outfall characterizes the total
plant effluent.
5. Sample each batch discharge.
6. If a point of upset exists within the plant, establishment of a
sampling station or monitoring equipment at that point will allow
early detection.
7. If data on different waste streams is available from past
records, use statistical techniques outlined in Section 4.5.1 as an
aid to establish the critical sampling locations within the plant.
6.5 NUMBER OF SAMPLES
Determine the number of samples from the following:
1. Follow NPDES permit requirements
2. Where NPDES permit is not applicable:
. Apply statistical methods (Section 4.2) to data from a
preliminary survey.
To effectively determine the concentration and types of
pollutants discharged, collect, no less that three operating day
composite samples.(2)
6.6 PARAMETERS TO MEASURE
6.6.1 NPDES Requirements
Parameters required for measurement in NPDES permits are listed by
industry in Table 6.1.(3) These are the parameters commonly required and
are minimal guidelines where exact permit specifications do not exist.
183
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TABLE 6,1 NPDES EFFLUENT LIMITATION PARAMETERS BY INDUSTRY
M —
CO
T*np*raturi Dlichirgit X X
Suspended Sol Ids XXX X X X X 1
Ollt, Fats * Brut* X X
Ammonia
Mltrlu-Nltrogtn
Kltmt-Nltrogen
Nitrogen (Kj»ld»bl)
X XX
X X X X
X X
X
X
X X X X XX
X X
X
X
,x
Phosphorus
Sulflte
Sulfld.
Sulf*t*
Chlorldt
Chlorlr*
F*e*t Coll fora lact.
Fluorld.
Birlwi
Boron
Chro.li*
Cobalt
Copper
-------
TABLE 6.1 (Continued)
1— »
CO
tn
Uad
pH
n*ns«n«««
Nircury
Nickel
Zinc
Phenols
PCB;
Aldrln
BleUHn
H*ptachler
Color
COO
Cyanide
Iron
Surfactant!
Alunlnum
Artinlc
Sattlaibla Solids
a
« — •» S1 e
11 5 1 I « . 1 * 3 "g . . s . . a - 1?
!- i J !-U»t!Si1* IflliHIiUUi
iiii'SliiHlHIliiiiilliiiiiMFP
X XX
X XX
X X
X X
XX XX
X XX XX
X X
X XXXXXX XXXX
XX X XX
X
X
X
X
X
-------
6.6.2 Other Parameters
Apply the techniques from Section 4.4 to establish parameters to
measure. If process control is desired, measure the critical constituent.
For example, if a distillation tower is to be controlled, monitoring the
organic carbon content of the discharge stream may provide early information
of leaks in the system.
6.7 TYPE OF SAMPLE
The permit will specify the type of sample, grab or composite, for
effluent monitoring, but consider both types for in-plant monitoring. Where
in-plant data do not exist, conduct a preliminary survey with production
personnel of each unit process to determine the chemical reactions,
production variability, location of individual waste streams and their
potential variability, and potential chemical constituents in each waste
stream. After careful analysis of the unit process, select the appropriate
type of sample to be collected. Collect proportional composite samples to
determine the average amount of pollutant or collect grab samples:
1. If a batch discharge is to be characterized.
2. If the flow is homogeneous and continuous with relatively constant
waste characteristics so a grab sample is representative of the
stream.
3. When the extremes of flow and quality characteristics are needed.
4. When one is sampling for a parameter requiring that the entire
sample be used for analysis with no interior transfers of
containers, for example, oil and grease.
5. When sampling for parameters which change character rapidly such as
dissolved gases or those which cannot be held for a long length of
time before analyses, for example, bacteria counts, chlorine,
dissolved oxygen and sulfide.
6.8 METHOD OF SAMPLING
Choose manual or automatic sampling depending upon which method is best
for the specific sampling program. (Refer to Chapter 2). Only trained
personnel should be entrusted the task of sample collection.
6.8.1 Automatic Samplers
If an automatic sampler is to be used, the actual type of sampler is
determined by the constituents in the wastewater. A list of samplers and
their features are given in Table 2.3. The features and techniques for use
of automatic samplers are discussed in Section 2.3.2. To choose a sampler,
list the features needed for sampling the type of industrial wastewater, as
outlined in Section 2.3.2.3. If the variability of the wastewater is not
186
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known or is large, use a sampler containing a multiplex feature, which
permits the collection of a composite sample in a single container while
collecting one or several discrete samples during a preset time interval.
Once the needed features have been established, the sampler which best
matches these features can be selected. Available samplers may need
adaptation. It is imperative that the stream be well mixed at the sampling
point to avoid problems when using automatic samplers in streams with a high
sol ids content.
6.9 VOLUME OF SAMPLE AND CONTAINER TYPE
The volume of sample to be taken is determined by the number of analyses
to be performed on the sample. If this has not been determined, a grab
sample volume, a minimum of 7.57L (2 gallon) and an individual composite
volume of 100 milliliters (0.21 pints) should be taken. The container type
is also contingent upon the analysis to be run.
6.10 PRESERVATION AND HANDLING OF SAMPLES
The preservation, holding times, and materials associated with sampling
depends upon the parameters to be analyzed. Guidance submitted for approval
to the 304 h committee, U.S. Environmental Protection Agency, is shown in
Chapter 17. Because approval and subsequent publication in the Federal Reg-
ister has not taken place as of publication of this Handbook, the reader is
urged to keep abreast of future changes through Federal Register publica-
tions.
6.11 FLOW MEASUREMENT
Flow measurement techniques adopted should be in relation to the
sampling location, type of flow, and other similar characteristics. Refer
to Chapter 3 on Flow Measurements. Primary and secondary devices should be
calibrated prior to taking flow measurements.
6.12 REFERENCES
1. Black, H.H. Procedure for Sampling and Measuring Industrial Waters.
Sewage Industrial Wastes. 24:45, January, 1952.
2. Rabosky, J.G. and D.L, Koraido. Gaging and Sampling Industrial
Wastewaters. Chemical Engineering 80 p. 111-120, January 8, 1973.
3. N.F.I. C-Denver. Effluent Limitations Guidelines for Existing Sources
and Standards of Performance for New Sources for 28 Point Source
Categories. Denver, Colorado, p. 122, August, 1974.
187
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CHAPTER 7
SAMPLING AGRICULTURAL DISCHARGES
7.1 BACKGROUND
Agricultural discharges can be separated into three types: concen-
trated animal waste or manure from a confined feedlot, run-off from an
agricultural watershed, and irrigation return flow. These three types of
run-off differ mainly in the concentration of pollutants. Field run-off
from rainfall, irrigation and snowmelt is characteristically the least
polluted, while feedlot run-off is the most concentrated waste. The
concentrations of pollutants from field run-off and irrigation return flow
vary with the amount and intensity of rainfall or snowmelt, irrigation
practices, land use, topography, soil type and use of manure or fertilizer.
7.2 OBJECTIVES
Agricultural discharges are sampled to study both field and feedlot
run-off, or to monitor field or treated feedlot run-off for regulation.
7.3 FREQUENCY OF SAMPLING
7.3.1 Feedlot Discharge
7.3.1.1 Regulatory
The sampling frequency must follow that given in the discharge permit.
Daily sampling is the maximum requirement in most permits.
7.3.1.2 Other
Apply the spectral analysis techniques as outlined in Section 4.3.1.
Collect preliminary data if not available by conducting one of the following
(in order of preference)
a. A one week survey collecting hourly grab samples where the
discharge is continuous.
b. A 24-hour survey collecting hourly grab samples.
188
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Calculate the mean and variance as indicated in Sections 4.1.1.1 and
4.1.1.4 and apply a computer program for spectral analysis.
7.3.2 Field Run-off and Irrigation Return Flow
Apply the statistical methods outlined in Section 4. If possible,
collect preliminary data by sampling every five minutes for the duration of
several run-off events.(1) Collect and analyze samples individually or
composite them proportional to flow, depending on the objectives of the
study. Since most of the variability in the run-off occurs during the
initial part of the run-off hydrograph on the rising side of flow crests,
sampling is the most critical at this time.
7.4 LOCATION OF SAMPLING POINTS
7.4.1 Feedlot Discharge
Channel feedlot run-off to a central point by sloping or trenching if
no treatment is provided. If treatment is provided, sample effluent from
the treatment system.
7.4.2 Field Run-off and Irrigation Return Flow
Select a site downstream of the run-off area at a point where run-off
collects into a channelized flow. Use the topography of the area to locate
this point. Choose a location with sufficient depth to cover the sampler
intake without excavation. Irrigation tailwater should be sampled and
measured quantitatively at the lower end of the field before it comingles
with other waters in the drainage ways.
7.5 NUMBER OF SAMPLES
The number of samples for both feedlot discharge and field run-off are
determined by 1) Following regulatory requirements, and 2) Applying the
statistics in Section 4 after the mean and variance are determined through a
preliminary survey (see Section 7.3).
7.6 PARAMETERS TO ANALYZE
7.6.1 Established by Regulation
Analyze all parameters required by discharge permits.
7.6.2 No Reg u i reme n t s
Analyze for (2,3,4,5,6), Nutrients (total phosphate and nitrogen
series), Demand (BOD,COD,TOD), Physical/Mineral (total and suspended
solids), fecal coliform and fecal streptococci, Total Dissolved Solids, and
other analyses such as metals, pesticides, or herbicides.
189
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7.7 TYPE OF SAMPLE
Do not collect a single grab sample due to the high variability of
run-off. Collect a series of samples for analyses, or form a composite sam-
ple according to flow using one of the methods described in Section 2.4.5.
7.8 METHOD OF SAMPLING
Collect samples automatically or manually. Collect discrete samples
separately or composite them proportional to flow. For sampling field
run-off, use an automatic system activated by run-off through the flume.
Typical sampling/flow measurement stations are shown in Figures 7.1 and 7.2,
If feedlot run-off contains large particulate matter such as corn cobs,
manual sampling will be necessary.
7.9 VOLUME OF SAMPLE AND CONTAINER TYPE
Use multiple containers for samples to provide the best preservation
for specific parameters. For example, if the parameters given in Section
7.6.2 (nutrients, demand, physical/mineral, microbiological) are to be
analyzed, three containers and three preservation techniques would be
required for each sample.
Container
Parameter Group
Nutrients
2
3
Demand, TDS
(Physical/Mineral)
Microbiological
Technique
Add H2S04 to pH 2 or
40-400 mg/1 Hgd2 and
refrigerate at 4°C
Ice as soon as possible
after collection
Collect grab sample in
sterile container and
ice as soon as
possible, hold for no
longer than six hours
7.10 FLOW MEASUREMENT
Select the flow measurement device based on the specific application
and the necessary degree of accuracy. A type H flume is advantageous
because of its wide range of accuracy.(3)(7) Instrumentation should include
a continuously recording flow chart, with a pressure-sensitive record
preferred to ink. A schematic of a typical installation is shown in Figure
7.3. More detailed information on flow measurement is given in Chapter 3.
190
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H Flume
Automatic
Sampler
Self Starting
Stage Recorder
_Still ing Well
Figure 7.1 View of field
installation (from 8)
-------
.Jt
Motorized
Sampl ing
Slot
Self Starting
Stage Recorder
Flume
Figure 7.2 View of field installation (9)
-------
STRIP CHART
FLOW
HYDR06RAPH
12 v.
SOLENOID
SAMPLE
BOTTLE'
7
—RECORDING PEN
L SAMPLING
CONTACTS
SAMPLE
CLAMP
-FLOAT
RUNOFF
Figure 7,3 Schematic of water level recorder
and sampler arrangement (from 8)
-------
7.11 REFERENCES
1. Miner, J.R., L.R. Bernard, L.R. F1na, G.H. Larson, and R.I. Upper.
Cattle Feedlot Runoff Nature and Behavior. Journal WPCF. 38;
834-847, October, 1966.
2. Humenik, F.J. Swine Waste Characterization and Evaluation of Animal
Waste Treatment Alternatives. Water Resources Research Inst., Univ.
of North Carolina, Raleigh, North Carolina, June, 1972. 152 p.
3. Harms, L.L., J.N. Dornbush and J.R. Anderson. Physical and Chemical
- Quality of Agricultural Runoff. Journal WPCF. 46; 2460-2470,
November, 1974.
4, Robbins, J.W.D., D.W. Howells and S.J. KHz. Stream Pollution from
Animal Production Units. Journal WPCF. 44: 1536-1544, August, 1972.
5. Fitzsimmons, D.W., C.E. Braceway, J.R. Busch, L.R. Conk!in and R.B.
Long. Evaluation of Measures for Controlling Sediment and Nutrient
Losses from Irrigated Areas. EPA-60Q/2-78-138, Robert S. Kerr
Environmental Research Laboratory, Ada, Oklahoma, July, 1978.
6. Skogerboe, G.W., W.R. Walker and R.6. Evans. Environmental Planning
Manual for Salinity Management In Irrigated Agriculture.
EPA-600/2-79-062, Robert S. Kerr Environmental Research Laboratory,
Ada, Oklahoma, March, 1979.
7. Madden, J.M. and J.N. Dornbush. Measurement of Runoff and Runoff
Carried Waste from Commercial Feedlots. Proc. Int. Symposium on
Livestock Wastes. Ohio State Univ., Columbus, Ohio. April 19-22,
1971. 44-47
8. Harms, L.L. South Dakota School of Mines and Technology. Rapid City,
South Dakota. Personal Communication to Environmental Sciences
Division. December 20, 1974.
9. Leonard, R.A., C.N. Smith, 6.W. Langdale and 6.W. Bailey. Transport of
Agricultural Chemicals from Small Upland Piedmont Watersheds.
Environmental Research Laboratory, Office of Research and Development,
Athens, Georgia, EPA-600/3-78-056, May, 1978.
194
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CHAPTER 8
SAMPLING SURFACE WATERS, AQUATIC ORGANISMS, AND BOTTOM SEDIMENTS
8.1 BACKGROUND
The sampling of rivers and streams, lakes and aquatic organisms, and
their associated bottom sediments are considered in this chapter. For a
more detailed discussion on aquatic sampling, consult the EPA biological
methods manual.(1) The decisions regarding analytical parameters must be
made at the beginning of the study in order to develop a rational sampling
program.
8.2 OBJECTIVES OF THE STUDY
The main objectives of sampling surface waters, aquatic organisms, and
sediments are:
1. Evaluation of the standing crop, community structure, species
diversity, productivity and stability of aquatic organisms.
2. Evaluation of the quality and trophic state of a water system.
3. Determination of the effect of a specific discharge on a certain
water body.
8.3 PARAMETERS TO ANALYZE
Surface waters and sediments are commonly analyzed for the chemical and
biological parameters listed in Table 8.1.
8.4 LOCATION OF SAMPLING POINTS
Select the study site based on the program objectives, the parameters
of interest, and the type of sample. For example,, the following guidelines
are suggested in the EPA Model State Water Monitoring Program (2) for
selecting long term biological trend monitoring stations:
1. At key locations in water bodies which are of critical value for
sensitive uses such as domestic water supply, recreation,
propagation, and maintenance of fish and wildlife.
195
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TABLE 8.1 COMMON MEASUREMENTS FOR SURFACE WATER, AQUATIC ORGANISMS
AND SEDIMENT SAMPLING
Chemical
Physical
Biological
Dissolved
Phosphate
oxygen
Nitrogen series
Alkalinity
Silica
pH
Specific Conductance
Solids (IDS, TS, TSS)
Organic matter and demand
Pesticides
Heavy Metals
Color
Turbidity
Water temperature
Stream velocity
Water depth
Sediment composition
Fish
Benthic Macroin-
vertebrates
Periphyton
Phytoplankton
Zooplankton
Macrophytes
Macroalgae
Bacteria
2. In the main stream upstream and downstream from the confluence of
major tributaries and in the tributary upstream from the confluence
with the main stream.
3. Near the mouths of major rivers where they enter an estuary.
4. At locations in major water bodies potentially subject to inputs of
contaminants from areas of concentrated urban, industrial, or
agricultural use.
5. At key locations in water bodies largely unaffected by man's
activities.
Use one of the following random or non-random sampling plans to
determine sampling points within the study site. Sample selection is
discussed in more detail in the EPA biological methods manual.(1)
8.4.1 Simp1e Ran dpm Sampling
Use a simple random sampling plan when there is no reason to subdivide
the population from which the sample is drawn. Draw the sample such that
every unit of the population has an equal chance of being selected. First,
number the universe or entire set of sampling units from which the sample
will be selected. This number is N. Then from a table of random numbers
select as many random numbers, n, as there will be sampling units selected
for the sample. Select a starting point in the table and read the numbers
consecutively in any direction (across, diagonal, down, up). Determine the
number of observations, n (sample size), prior to sampling. For example, if
n is a two digit number, select two digit numbers ignoring any number
greater than n or any nunjber that has already been selected. Select these
as the sampling units.
196
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8.4.2 Stratified Random Sampling
Use a stratified random sampling plan if any knowledge of the expected
size or variation of the observations is available. To maximize precision,
construct the strata such that the observations are most alike within strata
and most different among strata, in order to substain minimum variance
within strata and maximum variance among strata. Perhaps the most
profitable means of obtaining information for stratification is through a
prestudy reconnaissance or piTot study. For information on conducting a
pilot study, consult the EPA biological methods manual.(1) Stratification
is often based upon depth, bottom type, isotherms, or other variables
suspected of being correlated with the parameter of interest. Select as
many strata as can be handled in the study. In practice, however, gains in
efficiency due to stratification usually become negligible after only a few
divisions unless the characteristic used as the basis of stratification is
very highly correlated with the parameter of interest.(2)
8.4.3 Systernatjc_ Random Samp!ing
Use a systematic random sampling plan to assure an adequate cross
section while maintaining relative ease of sampling. A common method of
systematic sampling involves the use of transect (Figures 8.1) or grid
(Figure 8.2). However, choose a random starting point along the transect or
grid to introduce the randomness needed to guarantee freedom from bias and
allow statistical inference.
8.4.4 Nonrandom Sampling
Use a nonrandom sampling plan if justified by the study site, or
parameters of interest, or the type of study being undertaken. For example,
the following sample locations might satisfy the program objectives:
Parameter
Fish
Benthic maeroinvertebrates
Periphyton
Phytoplankton
Zooplankton
Macrophytes
Chemical
8.4.4.1 Impact of Point Discharges
Sampling Location
Shoreline sampling
Right, left bank, midstream or
transect
Shoreline sampling
Transect or grid
Transect or grid
Shoreline sampling or transect
Transect or grid
Use transect sampling scheme to determine the impact of a point
discharge. A presurvey is recommended to determine the zone of influence.
1. Place lines transecting the receiving water at various angles from
the discharge point.
2. Choose sampling intervals randomly or uniformly or by the methods
described in Section 8.4.4.2.
197
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3. Choose one or two remote control points to use as background.
4. See Figure 8.1 for example.
Point
Source
o Control
Point
o Control
Point
Shoreline
Figure 8.1 Example of transect sampling scheme in reservoirs,
lakes and coastal waters
A grid sampling scheme may be used for some biological parameters.
The grid must fit in a single environment, such as all riffles or all pools
for a valid comparison.
1. Set up grids across and through the area to be sampled (that is, in
both width and depth directions versus length) as required by the
program.
2. The grid size is dependent upon the degree of lateral and vertical
mixing. If the amount of mixing is unknown, then take a larger
number of samples across and through the stream than would be
otherwise desirable.
3. Choose the number of samples randomly, uniformly or using the
procedure in Section 8.4.4.2.
4, Choose a control point upstream of the grid system and point
source.
5. See Figure 8.2 for an illustration of the grid method.
198
-------
Point
Source
Figure 8.2 Example of grid sampling scheme in rivers
8.4.4,2 Spatial Gradient Technique
This technique may be used for the rational selection of sampling
station locations.(3)(4) It presupposes the existence of historical data or
some reasonable estimate of the expected variability of the parameters to be
monitored over the region of interest, say, along the length of the river.
This technique has greater applicability for chemical than biological
parameters.
1.
2.
3.
4.
5.
Collect historial or comparable data to estimate the mean and
variance of the parameter of interest, Y.
Plot the maximum and minimum values of the parameter concentration
versus distance along the river (Figure 8.3).
Calculate a slope for both lines (6 and Gm4r%).
max
mm'
Determine the difference between the slopes, i.e., G - G . ,
Determine the maximum allowable error in the estimates of the
parameter value at Point B.
Y.
d
max
max
G - G .
max mm
Use this d to determine distance between points on a transect or
grid in a grid pattern.
199
-------
Distance Along River
Figure 8.3 Use of spatial gradient technique for
maximum spacing of sampling stations
8.5 RANDOM SAMPLING
The following information is summarized from the EPA biological methods
manual.(1)
8.5.1 Simple RandomSampling
Use one of the following two methods depending on the decision
variable.
1. Estimation of a Binomial Proportion - An estimate of the proportion
of occurrence of the two categories must be available. If the
categories are presence and absence, the probability of observing a
presence is P (0 < P < 1) and the probability of observing and
absence is Q (0 < Q < 1, P + Q = 1). The second type of
aoo
-------
information which is needed is an acceptable magnitude of error, d,
in estimating P (and hence Q). With this information, together
with the size, n, of the population, the formula for n as an
initial approximation (n ), is:
a. For n > 30, use t - 2. This n ensures with a 0.95
probability that P is within d of its true value.
b. For n < 30, use a second calculation where t is obtained from
a table of "Student's t" with n - 1 degrees of freedom. If
the calculation results in an n , where
-in2- < 0.05
no further calculation is warranted. Use n as the sample
o
n
size If -n— > 0.05 make the following computation:
no
no -
2. Estimation of a Population Mean for Measurement Data - In this case
2
as estimate of the variance S , must be obtained from some source,
and a statement of the margin of error, d, must be expressed in the
same units as are the sample observations.
n -&1
a. For n >30, use o .,2
n
b. For n <30, recalculate using t from the tables, and if M >
0.05 ° N
n
g_
n = n_
After a sample size, n, is obtained from the population, the
basic sample statistics may be calculated. If the sample size,
n, is greater than 5% of the population (S- > 0.05), a
201
-------
correction factor is used so that the calculation for the
sample variance is:
N-n
n-1
8.5.2 Stratified Random Sampling
Conduct a pilot study or obtain reliable estimates of the variance
within strata from other sources. If historical data have been collected,
use optimal allocation to determine the total number of samples.
n=^£
N2d2
Where t = Student's t value (use 2 for estimate)
N. = number of sampling units in stratum k
2
s,. = variance of stratum k
2
. = standard deviation of stratum k
K. <
N = total number of sampling units in all strata
d = acceptable parameter error
If no data are available, use proportional allocation to determine the
total number of samples:
2 2
tzNksk
N2d2
Use the following equations to determine the number of samples to be
collected in each stratum, n.:
nNksk
Optimal allocation: n. = T*.\
k Nksk
202
-------
nN,
Proportional allocation: n. = —n—
8.5.3 Systemati c Random Sampl1ng
Determine the number of samples to be taken on the grid or transect
using the methods given in Section 8.4.4.2 or 8.5.1.
8.6 FREQUENCY OF SAMPLING
While the frequency of sampling will often be determined by the
program, use the Model State Water Monitoring Program (1) guidelines for
guidance in trend monitoring (Table 8.2).
8.7 METHOD OF SAMPLING
While compositing of individual grab samples is permitted for most
chemical parameters, as a rule biological samples are not composited. For
biological parameters, collect single grab samples.
8.8 TYPES OF SAMPLES FOR AQUATIC ORGANISMS
Choose the type of sampler that meets the needs of the sampling program
by considering the advantages and disadvantages of the sampler type. In
general, equipment of simple construction is preferred due to ease of
operation and maintenance plus lower expense. Advantages and disadvantages
of various water bottles are shown in Table 8.3 and illustrated in Figure
8.4. This equipment is useful for chemical, phytoplankton and zooplankton
sampling. Corers and bottom grabs (Tables 8.4 and 8.5 and Figures 8.5 and
8.6) are useful for sediment sampling. Nets and substrate samplers are
covered in Tables 8.6 and 8.7 and Figures 8.7 and 8.8.
There are inherent advantages of using a diver for sediment sampling.
The diver can ascertain what is a representative sample in addition to
taking pictures and determining qualitatively the current velocity.
8.9 VOLUME OF SAMPLE AND CONTAINER TYPE
Refer to Chapter 17 for specific information relative to the chemical
parameters which are to be analyzed. In general, do not use metal samplers
for trace metal nor use plastics for sampling trace organics. Refer to the
biological methods manual (1) for container type and sample volumes, where
applicable.
203
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TABLE 8.2 MODEL STATE HATER MONITORING PROGRAM GUIDELINES FOR BIOLOGICAL MONITORING (1)
Community
Parameter
Collection & .
Priority analysis method
Sampling frequency
INS
o
Plankton Counts and identification 1
Chlorophyll a;
Biomass as ash-free weight
Periphyton Counts and identification 1
Chlorophyll a; 2
Biomass as ash-free weight 2
Macrophyton Area! coverage; 2
Identification; 2
Biomass as ash-free weight 2
Macroinver- Counts and identification 1
tebrate Biomass as ash-free weight 2
Flesh tainting; , 2
Toxic substances in tissue
Fish Toxic substances in tissue 1
Counts and identification 2
Biomass as wet weight; 2
Condition factor;
Flesh taining 2
Age and growth 2
Grab samples
Artificial
substrate
Once each;
and fall
in spring, summer
As circumstances
prescribe
Artificial and
natural
substrates
Electroffshing
or netting
Minimally once annually
during periods of peak
periphyton population
density and/or diversity
Minimally once annually
during periods of peak
macrophyton population
density and/or diversity
Once annually during periods
of peak macroinvertebrate
population density and/or
diversity
Once annually during
spawning runs or other
times of peak fish
population density
and/or diversity
a Priority: 1) Minimum program; 2) Add as soon as capability can be developed.
b See EPA Biological Methods Manual.
c Keyed to dynamics of community,
d See "Analysis of Pesticide Residues in Human and Environmental Samples," USEPA, Perrine Primate
Research Lab, Perrine, FL 32157 (1970), & "Pesticide Analytical Manual," USDHEW, FHA, Wash, D.C.
-------
TABLE 8.3 COMPARISON OF WATER SAMPLERS
Device Application
Nansen Bottle Phytoplankton
Kemmerer Bottle Chemical*
Bacteriological
no Zooplankton
en
Van Dorn Bottle Chemical*
Bacteriological
Zooplankton
Phytoplankton
Simple Bottle Chemical*
Bacteriological
Pumps Chemical*
Zooplankton
Phytoplankton
Material
Contacted
Teflon lined
PVC
Brass
Acrylic plastic
PVC
Glass
430 Stainless Steel
Advantages
Able to use in series
No metal contamination
No metal contamination
No metal contamination
No metal contamination
No metal contamination
Inexpensive
Large volume, samples
a vertical water column,
continuous sample
Disadvantages
Small volume
Fixed capacity
from 0.4-16 L
Metal toxicity
Fixed capacity
from 2-30 L
No depth control
Possible metal
contamination,
physical dammage
to organisms
* Organic chemicals such as pesticides, priority pollutants, etc. should be sampled with materials type
such as teflon, glass, or other proven non-contaminating materials.
-------
TABLE 8.4 COMPARISON OF BOTTOM GRABS/SAMPLERS
Device
Advantages
Disadvantages
Ponar
o
en
Ekman
Tall Ekman
Peterson
Smith-Mcintyre
I
Diver
Safe, easy to use, prevents escape of
material with end plates, reduces shock
wave, combines advantages of others,
preferred grab in most cases
Use in soft sediments and calm waters,
collects standard size sample
(quantitative), reduces shock wave
Does not lose sediment over top; use
in soft sediments and calm water,
standard sample size, reduces shock wave
Quantitative samples in fine sediments,
good for hard bottoms and sturdy and
simple construction
Useful in bad weather, reduces premature
tripping, use in depths up to 1500 m
(3500 ft), flange on jaws reduces
material loss, screen reduces shock waves,
good in all sediment types
Can determine most representative
sampling point and current velocity
Can become buried in soft sediments
Not useful in rough water; not useful
if vegetation on bottom
Not useful in rough waters, others as
for Ekman
May lose sampled material, premature
tripping, not easy to close; does not
sample constant areas; limited
sampling capacity
Large, complicated and heavy, hazardous
for samples to 7 cm depth only, shock
wave created
Requires costly equipment and
special training
-------
TABLE 8.5 COMPARISON OF CORING DEVICES
Device
Advantages
Disadvantages
O
-x)
Kajak or
K.B. Corer
Does not impede free flow of
water, no pressure wave, easily
applied to large area
Moore (Pfleger) Valve allows sample to be held
0'Conner
Elgmork's
Jenkins
Enequist
Kirpicenko
Can sample water with hard bottoms
Sample easily removed, good in soft
muds, easy to collect, easy to
remove sample
Good in soft sediments and for
collecting an undisturbed
sediment-water interface sample.
Visual examination of benthic
algal growth and rough estimates
of mixing near the interface after
storms can be made
Good in soft/medium sediments,
closing mechanism
Soft and hard bottoms, various
sizes, closes automatically
Careful handling necessary to avoid
sediment rejection, not in soft
sediments
Not in deep water
Not in hard sediments
Complicated
Does not penetrate hard
bottom
Not for stony bottoms
-------
TABLE 8.6 COMPARISON OF NET SAMPLING DEVICES
Devices
Application
Advantages
Disadvantages
Wisconsin Net
Clarke-Bumpus
Zooplankton
Zooplankton
Efficient shape
concentrates
samp!e
Quantitative
Qualitative
No point sampling,
difficult to mea-
sure accurately
depth of sample
208
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TABLE 8.7 COMPARISON OF SUBSTRATE SAMPLERS
Type of Substrate
Advantages
Disadvantages
o
10
1. Artificial
Modified
Hester-Dendy
Fullner
EPA Basket Type
EPA Periphyton
Reduces compounding effects of
substrate differences, multiplate
sampler
Wider variety of organisms
Comparable date, limited extra
material for quick lab processing
Floats on surface, easily anchored,
glass slides exposed just below
surface
Long exposure time, difficult
to anchor, easily vandalized
Same as modified Hester-Dendy
No measure of pollution on
strata, only community formed
in sampling period, long
exposure time, difficult to
anchor, easily vandalized
May be damaged by craft;
easily vandalized
2. Natural
Any bottom or
sunken material
Indicate effects of pollution, gives
indication of long term pollution
May be difficult to Quantitate
Possible lack of growth, not
knowing previous location or
duration of exposure
-------
Nansen Water Bottle
f "%l ^•^Swfe?- j.
' " "i^f^k"! 'vs,'-'r/Xif %
- ' <
-. -• .' V ,..-: .<• VV'A5/; - ,-p'-»i£f-^-
•• -. -X
'-> * * * ^ *''*'?
Van Dorn Sampler
8.4 Water Bottles
(Courtesy of Wildlife Supply Co.)
210
-------
°onar Sampler (two sizes)
Fiqure 8.5 Bottom Grab Samplers
(Courtesy of Mildlife Supply Co.)
211
-------
Smith-Mclntyre (Aberdeen) Grab
Figure 8.5 (continued) Bottom Grabs
212
-------
£
a.
m
tn
o
o
vO
od
3
05
4)
\- •—
ft) Q.
— £
Q. TO
iE V5
(0
>
V —
tfl (0
o o
-\
213
-------
Clark-Bumpus Sampler
Wisconsin Net
Figure 8.7 Nets and Related Samplers
214
-------
Surface
Side View
: ! I
Hi*
0
oei 0
Top View
EPA Periphyton sampler. Plexiglass frame supported by
two styrofoam floats. Rack holds eight glass microscope
slides.
Figure 8.8 Periphyton samplers
215
-------
Modified Hester-Dendy
type multiple-plate
artificial substrate
Limestone filled
basket sampler
Figure 8.8 (Continued)
216
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8.10 PRESERVATION HANDLING OF SAMPLES
Refer to Section 17.1 for specific information regarding preservation
and handling of samples relative to the chemical parameters to be analyzed,
and to the EPA biological methods manual (2) for aquatic organism
preservatives.
8.11 FLOW MEASUREMENT
Flow measurement in rivers is accomplished by the combined use of a
current meter to measure the stream velocity and a stage recorder to measure
the surface elevation of the river. Consult USGS gaging stations for
additional or historic information. See Secton 3 for more details.
8.12 REFERENCES
1. Weber, C.I., editor. Biological Field and Laboratory Methods for
Measuring the Quality of Surface Waters and Effluents. National
Environmental Research Center, Office of Research and Development, U.S.
EPA, Cincinnati, Ohio, EPA 670/4-73-001, 1973.
2. National Water Monitoring Panel. Model State Water Monitoring Proqram.
U.S. EPA Report No. EPA-440/9/74-002. U.S. EPA Office of Water and
Hazardous Materials, June, 1975.
3. Hill, R.F. Planning and Design of a Narragansett Bay Synoptic Water
Quality Monitoring System. NEREUS Corp., 1970.
4. Drobny, N.L. Monitoring for Effective Environmental Management. Proc.
ASCE National Water Resources Engineering Meeting. Atlanta, Georgia.
January 24-28, 1972.
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CHAPTER 9
SAMPLING OF GROUND AND DRINKING WATER
9.1 BACKGROUND-GROUND WATER
Ground water accounts for the base flow of all perennial streams', over
90 percent of the world's fresh water resources, and one half the drinking
water in the United States, yet has traditionally received only token
scientific attention. Although surface and ground waters are inseparable
parts of the same hydro!ogic system with the waters of each flowing
alternately between the two components, water resource planners have often
considered them as separate entities.
The Safe Drinking Water Act (PL 93-523) of 1974 has done much to
rectify this neglect by recognizing ground water quality protection. This
Act plus subsequent legislation, the Toxic Substances Control Act (PL
94-469) and the Resource Conservation and Recovery Act(PL 94-580) further
recognizes that ground water quality is being increasingly threatened by
various human activities, particularly the disposal of waste materials to
the land.
In order to assess the impact of such activities on ground water
quality and, hence, to provide a rational basis for its protection, the
behavior of pollutants in the subsurface and the processes governing this
behavior must be evaluated. However, many water resource planners,
inexperienced in ground water investigations, are learning that techniques
applicable to surface waters do not necessarily apply to ground water.
Methods of collecting a representative ground water sample are much
more difficult and expensive in this often remote and relatively
inaccessible environment. The subsurface is an extremely complex system
subject to extensive physical, chemical and biological changes within small
vertical and horizontal distances.
The purpose of this chapter is to provide some of the most prevalent
methods of sampling the subsurface and drinking waters. A more detailed
and comprehensive discussion of ground water can be found in an unpublished
EPA report entitled Manual of Ground Water Quality Sampling Procedures,(1)
9.2 OBJECTIVES OF GROUND WATER SAMPLING
Samples from a monitoring well represent a small part of an aquifer
horizontally and in many cases, vertically. Unlike its surface counterpart
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where a sample can be arbitrarily taken at any point in the system, moving a
ground water sampling point implies the installation of additional
monitoring wells. Because of the difficulty and expense, it is essential
that sampling objectives be firmly established well in advance of field
activities. These objectives will dictate the parameters to be measured,
the necessary reliability of the water quality data, and analytical
methodology and thence the sampling procedures necessary to meet these
objectives.
If the objective is simply to determine the presence or absence of a
conservative pollutant in a particular water supply, it is simple and
relatively inexpensive to collect a sample at a water tap. However, if the
objective is to define the horizontal and vertical distribution of an
organic pollutant or pollutants and predict the eventual fate, then soil
cores, monitoring wells and special sampling equipment may increase efforts
and cost several orders of magnitude.
In the former case, the purpose of the sample collection activity is
known and limited in scope. In the latter case, there is a need to be
concerned not with point data as an end in itself, but as a component of a
network approach wherein information on the ground water system is developed
as a basis for extrapolating information to areas where samples were not
collected and/or for predicting the effects of natural and man made stresses
on the subsurface system.
9.3 GROUND WATER SUBSURFACE CHARACTERISTICS
The unstable nature of many chemical, physical, and microbial
constituents in ground water and subsurface limit the sample collection and
analyses options. However, certain factors should be considered when
collecting representative samples:
1. Ground water moves slowly, therefore a slow rate of change of water
quality parameters.
2. Temperatures are relatively constant in the subsurface, therefore
the sample temperature may change significantly when brought to the
surface. This change can alter chemical reaction rates, reverse
cationic and anionic ion exchanges on solids, and change microbial
growth rates.
3. A change in pH can occur due to carbon dioxide adsorption and
subsequent changes in alkalinity. Oxidation of some compounds may
also occur.
4. Dissolved gases such as hydrogen sulfide may be lost at the
surface.
5. Integrity of organic samples may be affected by problems associated
with either adsorption or contamination from sampling materials and
volatility.
6. Both soils and ground waters may be so severely contaminated as to
present a health or safety problem to sampling crews.
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9.4 LOCATION OF GROUND WATER SAMPLING POINTS
9.4.1 General Considerations
The area of consideration, the time available for monitoring, and
potential concentration levels of pollutants all influence the sampling
procedures selected. A regional or large area monitoring program may permit
the use of existing wells, springs or even the baseflow of streams if these
systems are compatible with the parameters of interest. If time is critical,
existing sampling locations may be the only alternative. However, if the
possible pollution source is relatively small, such as a landfill or lagoon,
or if pollutant concentrations may be very low, such as with organics,
special monitoring wells will almost surely be necessary. The number and
location of additional wells needed depends on the purpose of monitoring,
aquifer characteristics, and mobility of pollutants in the aquifer.
If the potential contamination source is above the water table, it may
be necessary to sample the unsaturated zone to get a true picture of the
threat to ground water. With the exception of chlorides, and to a lesser
extent nitrates and sulfates, most pollutants can be sorbed to materials in
the unsaturated zone and removed to some extent under favorable conditions.
(2) Therefore, it is possible to sample the ground water beneath a waste
source for years and observe no contamination. This can give a false sense
of security when actually pollutants are still moving very slowly through
the unsaturated profile toward the ground water.
9.4.2 Hydrogeologic Data
Geologic factors relate chiefly to geologic formations and their water
bearing properties, and hydro!ogic factors relate to the movement of
water in the formations.
Knowledge of the hydrogeologic framework is important from two
standpoints: (a) prediction of ground water movement; and (b) geochemical
considerations which affect the quality of ground water. The geologic
framework includes lithology, texture, structure, and mineralogy, and the
distribution of the materials through which ground water flows. The
hydraulic properties of the earth materials depend upon their origin and
lithology, as well as the subsequent stresses to which the materials have
been subjected. Ground water movement depends upon the effective
permeability and the hydraulic gradient within an aquifer. Permeability is
related to the nature, size and degree of interconnection of pores,
fissures, joints, and other openings.
Prior to initiating any field work, all existing geologic and
hydro!ogic data should be collected, compiled and interpreted. Data that
may be available include: geologic maps, cross-sections, aerial photographs,
and an array of water well data including location, date drilled, depth,
name of driller, water level and date, well completion methods, use of well,
electric or radioactivity logs, or other geophysical data, formation
samples, pumping test(s) and water quality data. After compiling and
thoroughly reviewing the collected data, the investigator can properly plan
220
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the type of investigation needed, including the data necessary to fill the
gaps and the sampling necessary (parameters, frequency and locations(s)).
Water level measurements are important basic preliminary data often used
in selecting ground-water sampling sites, equipment and procedures.
Water level data can be obtained from wells, piezometers, or from
surface-water manifestations of the ground water system such as springs,
lakes, and streams. The depth of water may detemine the type of pumps or
samplers used and procedures and cost of constructing monitoring wells.
Water level contours drawn from static levels in wells penetrating the same
aquifer can be used to make a preliminary determination of gross direction
of flow. Note that nearby pumping wells or other artificial discharges or
recharges may alter the natural gradient.
9.4.3 Hydrogeologic Considerations
The heterogeneous nature of subsurface environments makes the location
of sampling points a complicated and unpredictable science when trying to
intercept a pollutant plume. Hydrogeologic conditions are site specific and
it is impossible to prescribe standard locations for sampling points that
would be applicable to all sites. In an aquifer with intergranular
porosity, such as sands, gravels, sandstones and silts, water occurs in
interconnected void spaces between individual particles of aquifer material.
Some simplified "typical" flow patterns are illustrated in Figure 9.1. It is
readily apparent that the horizontal location of a monitoring well in
relation to the pollutant source determines whether or not contaminated
water is intercepted. Further, vertical location of the well screen and
other well construction aspects also affect the quality of a sample
collected from the well. Should the well screen be located above or below
the zone of contamination, and assuming proper seals are located above and
below the screen, samples from this well will very likely indicate no
contamination unless it is pumped sufficiently to change the ground water
flow pattern. On the other hand, if the well screen is not properly sealed
from other subsurface zones or if the entire saturated thickness is
screened, samples from the well may represent a composite of water from
several different zones and concentrations will not be representative.
Furthermore, such well construction may provide a conduit for the movement
of contamination from one zone to another.
Ground water flow patterns can be developed from water level contours.
However, the actual movement of a plume may be somewhat more complex. For
example, in a geologic environment such as alluvium or terrace deposits
involving intergranular permeabilities, the shape of the plume may be
controlled by abrupt changes in permeabilities such as the channel gravels
as shown in Figure 9.2. Such changes in permeability are common in river
deposited geologic formations and can greatly affect the shape and rate of
movement of pollution plumes.
The hydrogeology is further complicated by the different flow patterns
of different pollutants. Ground water contaminated with a dense pollutant
such as chloride creates a plume that tends to migrate to the base of the
aquifer. Conversely, lighter pollutants such as hydrocarbons tend to
"float" near the top of the saturated zone. In addition, different
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UPPER
—_ —- **•",•? -TV ""* i** **V\r**l ,v**i*jt,,T*••!***,*r%-Tf _*y'.y^-*i !•• ...-. ,. . i
-*•*• l__i." ii, I * •*-!!..'_±- *1T i*L t.-.j**....'.-_. _*- 'a.-''. '..
BED
Two-Aquifer System with Opposite Flow Directions. Leachate first
moves into and flows with the ground water in the upper aquifer.
Some of the leachate eventually moves through the confining bed
into the lower aquifer where it flows back beneath the landfill
and away in the other direction.
fiiROUND
TABLE
Permeable Sand Layer Underlain by a Clay Layer - The water
table is deep. Leachate percolates downward under the landfill,
forming a perched water table before finally reaching the
actual water table.
Figure 9.1 Typical Flow Patterns of Pollutant Plumes
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^^ •
A
Pollution
Source
CROSS SECTION
PLAN VIEW
Gravel-fi1 led
—^ channel
CROSS SECTION
PLAN VIEW
Figure 9
2 Effective
Pol 1uti on
of Permeability Change on Shape of
PI ume
223
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pollutants move through the subsurface at different rates relative to the
rate of water movement because of sorption, desorption, ion-exchange ;and
biodegradation. Therefore, points of maximum concentration of the different
pollutants along the ground water flow path will probably vary considerably.
Ground water flow patterns are even less predictable in fractured rock
or solution porosity aquifers than in aquifers with intergranular porosity.
Flow patterns are generally controlled by fracture patterns such as those
illustrated in Figures 9.3. Obviously, the problem in locating monitoring
wells in such geology is to intercept fractures or solution channels that are
hydraulically connected to the source of contamination. It is possible in
many formations of this type to drill a well that is dry and move only a few
feet away and drill another that has plenty of water. However, neither well
may be hydraulically connected to a source of pollution only a few feet away.
In some fractured rock formations where caving is not a problem it is
possible to complete a monitoring well as an open hole without using a well
screen. In most such wells it is advisable, however, to install casing
(grouted in place) to at least the depth planned to set the pump. Care must
be exercised especially in fractured rock formations such as limestone to
maintain the depth-specific factor for monitoring wells. Wells with much
open hole may intercept several fractured zones resulting in
intercommunication betweeen layers and sampling of mixed waters.
In spite of the complexity and in lieu of a detailed hydrogeologic
study, there are some basic guidelines that can be used in locating
monitoring wells based on the considerations noted previously. A more
detailed examination of locating monitoring wells for a landfill is
described in Procedures Manual for Ground Water Monitoring at Solid Waste
Disposal Facilities .(2)
9.4.4 Background Considerations
A necessary component of any ground water monitoring program is
background sampling. Occasionally, it is possible to sample the ground
water quality of an area before a source of contamination is introduced.
This is desirable and may become more common in the future as ground water
quality protection becomes a greater part of normal operations. In most
instances, a potential source of contamination is already a reality and the
objective is to collect a sample for comparison that is out of the influence
of that source. Another consideration is that an analysis of an earlier
sample may not have included a parameter that is of current interest or that
analytical capabilities may have improved for certain parameters in the
meantime.
One recommended monitoring method for detecting contamination at
landfills is location of a background well upgradient from the landfill and
a minimum of three wells downgradient and at an angle perpendicular to
ground water flow, penetrating the entire saturated thickness of the
aquifer. Such an arrangement is illustrated in Figure 9.4 and is applicable
to most potential point sources of contamination.
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* as™. ™-
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LEGEND
A,B - MONITORING
WELLS
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-------
If there is adequate reason to suggest that contamination has already
occurred and the objective is to define the pollutant plume, this remains af
reasonable initial approach. However, it is extremely important to locate
subsequent monitoring wells one at a time, sample, and base succeeding welt
locations on results of previous sampling. Under no circumstances should
the entire drilling budget be expended on a series of monitoring wells based
entirely on the initial prediction of the direction of a pollutant plume.
Even with the best'of background information, there is a high probability
that a large percentage of these wells will miss the pollutant plume becails^
of the heterogeneous nature of subsurface permeabilities.
9.5 CONSTRUCTION OF GROUND WATER MONITORING WELLS
The success of a ground water monitoring program depends on numerous,
factors; however, the location, design, and construction of the monitoring
well is usually the most costly and non-repeatable factor. Hence it is
extremely important that the well construction be accomplished properly at
the outset. The primary objective of monitoring wells are: (a) provide
access to ground water; (b) determine which pollutants are present in the
ground water and their concentrations; and (c) determine the area! and
vertical distribution of pollutants. In order to accomplish these
objectives in the most competent and cost effective manner, consideration
must be given the proper well design and construction method that will
fit the specific objectives and the hydrogeologic conditions.
9.5.1 General Requirements
9.5.1.1 Diameter
The diameter of the casing for monitoring wells should be just
sufficient to allow the sampling tool (bailer or pump) to be lowered into
the well to the desired depth. The diameter of the hole into which the
casing is placed must be at least 2 inches larger to permit placement of a
grout seal around the outside of the casing.
Casings and/or holes drilled much larger than the necessary minimum
can, in fact, have undesired effects on the data. For example, in
formations of very low permeability, the excessive storage in an
unnecessarily large boring can cause the water level inside the boring to be
erroneously low for days or even weeks. Also, because it is usually
necessary to remove water standing in the well before taking a sample of tHe
formation water, excessive storage can complicate the water sampling
procedure.
9.5.1.2 Depth
The intake part of a monitoring well should be depth-discrete. That
part of the well, the screen or other openings, through which water enters
the well or casing should be limited to a specific depth range.
Water supply wells that may exist in an area to be monitored are often
used as sampling points. Substantial care must be exercised when this is
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done and the results are often questionable. Water supply wells are
constructed to produce a given quantity of water, hence, they may be
screened throughout a thick aquifer, through several permeable layers of an
aquifer, or sometimes through two or more aquifers or discrete water bearing
layers. When this situation exists,- it is probable that the hydrostatic
heads are different between different layers. Under nonpumping conditions,
this interconnection permits water from the layer with the higher head to
flow through the well and into the formation with the lower head. This can
occur between layers of different permeability separated by only a few feet
of low permeability material. This condition can, of course, have
substantial effect on the concentration of a pollutant obtained by pumping
for a short time before sampling.
Therefore, it is important that monitoring wells be constructed to be
depth-discrete and to sample only from one specific layer without
interconnection to other layers. In order to assure that this depth-
discrete requirement is met, provisions for placing cement grout above and,
if necessary, below the well screen on the outside of the casing must be
made in the design of the wells.
Commonly (especially when sampling for contaminants lighter than water)
it is desirable to sample at the water table, or top of the saturated zone
in an unconfined aquifer. The screen or intake part of the well should then
extend from a few feet above to a few feet below the anticipated position of
the water table to allow for future water table fluctuations. Often, under
semi confined aquifer conditions, the water will rise in the well above the
top of the more permeable layer and above the top of an improperly
positioned screen. Care must be exercised in these cases to extend the
screen high enough to be above the water level in the formation; otherwise,
light organics or other contaminants could be undetected or at least not
properly quantified.
On the other hand, a contaminant can migrate along fairly restricted
pathways and go undetected by depth-discrete wells which are not completed
at the proper depth. This danger is particularly present in a geologic
environment of highly stratified formations, and in fractured rock
formations.
9.5.1.3 Intake Portion of Monitoring Wells
That part of the well through which water enters the casing must be
properly constructed and developed to avoid subsequent sampling problems.
Commercially made well screens used in water supply wells are recommended
for most monitoring wells even though well efficiency is not a primary
concern. Other choices are sawed or torch cut slots in the well casing to
let the water flow in. The design criteria for the intake part of,the well
are:
(1) The screen or intake part should have sufficient open area to
permit the easy inflow of water from the formation
(2) The slot openings should be just small enough to keep most of
the natural formation out, but as large as possible to allow
228
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easy flow of water.
(3) The well should be developed.
9.5.1.4 Well Casing
Sampling equipment, including well casings, should be constructed of
materials that have the least potential for affecting the quality parameters
of the sample. The usual dilemma for the field investigator is the relation
between cost and accuracy. Obviously, PVC is far less costly than Teflon, a
major consideration when contemplating well construction for a major ground
water monitoring effort. On the other hand, bleeding of organic
constituents from PVC cements, as well as adsorption, poses a significant
potential for affecting the quality of samples where the contaminants under
consideration may be in the parts per billion range.
In many situations, it may be realistic to compromise some accuracy
with cost, particularly in regard to casing materials used in well
construction. For example, if the major contaminants are already defined
and they do not include substances which might bleed from PVC or cemented
joints, it might be reasonable to use wells cased with the less expensive
and readily obtainable PVC. Or, wells constructed of less than optimum
materials might be used with a reasonable level of confidence for sampling
if at least one identically constructed well was available in a nearby,
uncontaminated part of the aquifer to provide ground water samples for use
as "blanks," Obviously, such a "blank" will not address the problems of
adsorption on the casing material nor leaching of casing material induced by
contaminants in the ground water. Careful consideration is required in each
individual case, and the analytical laboratory should be fully aware of
construction materials used.
Care must be given to preparation of the casing and well screens prior
to installation. As a minimum, both should be washed with a detergent and
rinsed thoroughly with clean water. Care should also be taken that these
and other sampling materials are protected from contamination by using some
type of ground cover such as plastic sheeting for temporary storage in the
work area.
9.5.1.5 Drilling Methods
Selection of the drilling method best suited for a particular job is
based on the following factors in order of importance:
1. Hydrogeologic Environment
(a) Type(s) of formation(s)
(b) Depth of drilling
(c) Depth of desired screen setting below water table
2. Types of pollutants expected
3. Location of drilling site; dry land or inside a lagoon
4. Design of monitoring well desired
5. Availablity of drilling equipment
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The principles of operation, advantages and disadvantages of the more
common types of drilling techniques suitable for constructing ground'water
monitoring wells are discussed in detail in the manual of Ground Water
Quality Sampling Procedures.(1)
9.5.1.6 Use of Bore Hole Geophysics
The use of geophysics can greatly enhance the amount of information
gained from a borehole as shown in Figure 9.5. Each geophysical logging
method is designed to operate in specific borehole conditions, involves
lowering a sensing device into the borehole and can be interpreted to
determine lithology, geometry, resistivity, bulk density, porosity,
permeability.moisture content and to define the source, movement, chemical
and physical characteristics of ground water.(3)
1. Spontaneous Potential Log: These logs are records of the natural
potentials developed between the borehole fluid and the surrounding
rock/soil materials. The SP log is mainly used for geologic corre-
lation, determining bed thickness and separating non porous from
porous rocks in shale sandstone and shale carbonate sequences. It
can be run only in open, uncased and fluid filled boreholes.
2. Normal Resistivity Logs: Normal logs measure the apparent resis-
tivity of a volume of rock/soil surrounding. The short normals
give good vertical detail and records the apparent resistivity of
the mud invaded zone. The log normals record the apparent
resistivity beyond the invaded zone. The radius of investigation
is generally equal to the distance between the borehole current
and measuring electrodes. These logs can be run only in open,
uncased and fluid filled boreholes.
3. Natural Gamma Logs: Natural gamma logs or gamma ray logs are
records of the amount of natural gamma radiation emitted by rocks/
soils. The main use of this logging method is for the identifi-
cation of lithology and stratigraphic correlation. These logs can
be run in open or cased, fluid or air filled boreholes. The radius
of investigation extends to about 6 to 12 inches of the borehole
wall.
4. Gamma Gamma logs: These logs record the intensity of gamma
radiation from a source in the probe after it is^backscattered and
attenuated within the borehole and surrounding rocks/soil. The
main uses of gamma gamma logs are for identification of lithology
and measurement of bulk density and porosity of rocks/soils. They
are also used for locating cavities and cement outside the casing.
The radius of investigation is about 6 inches from the borehole
wall. These logs can be run in open or cased, fluid or air filled
boreholes.
5. Call per Log: A callper log is the record of the average borehole
diameter. Its major use is to evaluate the environment in which
other logs are made in order to correct for hole diameter effects.
They also provide information on lithology and borehole conditions.
Caliper logs can be run in fluid or air filled, cased or open bore-
holes.
230
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SPONTANEOUS
POTENTIAL
RESISTIVITY
SHORT
LONG
GEOLOGIC
LOG
GAMMA
RAY
NEUTRON
CLAY
V SAND
FEW CLAY
LAYERS
(FRESH
WATER)
1
SHALE
DENSE ROCK
LMS
r
SANDSTONE
SH LAYERS
(BRACKISH
WATER)
SHALE
FEW
SS LAYERS
SANDSTONE
(SALINE
WATER)
(WEATHERED)
DENSE
ROCK
PROBABLY
GRANITE
Figure 9.5 Comparison of Electric and Radioactive Bore Hole Logs
231
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6. Temperature Log: These logs provide a continuous record of the
fluid temperature immediately surrounding the probe. The data can
be interpreted to provide information on the source and movement
of ground water and the thermal conductivity of rocks/soils. Temp-
perature logs are best applied in fluid filled, open boreholes
although they can also be run in air filled and cased boreholes.
The zone of investigation is limited to that fluid immediately
surrounding the probe which may or may not be representative of the
temperature in the surrounding rock/soils,
7. Fluid Conductivity Logs: These logs provide a measurement of the
conductivity of the borehole fluid between the electrodes in the
probe. When properly corrected, they provide information on the
chemical quality of the borehole fluid. They are best applied in
open, fluid filled boreholes.
9.5.1.7 Well Development
Well development is the process of cleaning the face of the borehole
and the formation around the outside of the well screen to permit ground
water to flow easily into the monitoring well. During any drilling process,
the side of the borehole becomes smeared with clays or other fines. This
plugging action substantially reduces the permeability and retards the
movement of water into the well screen. If these fines are not removed,
especially in formations having low permeability, it then becomes difficult
and time consuming to remove sufficient water from the well before obtaining
a fresh ground water sample because the water cannot flow easily into the
well.
The development process is best accomplished for monitoring wells by
causing the natural formation water inside the well screen to move
vigorously in and out through the screen in order to agitate the clay and
silt, and move these fines into the screen. The use of water other than the
natural formation water is not recommended. Methods suitable for the
development of monitoring wells are discussed in detail in the Manual of
Ground Water Quality Sampling Procedures.(1)
9.5.1.8 Multiple Completion Sampling Wells
Occasionally, it is desired to sample numerous permeable layers at
considerable depth, perhaps at a few hundred feet. If, for example, it is
desired to define the bottom of the pollution plume and then to periodically
sample the lower most contaminated layer, a cemented and gun-perforated well
can be constructed. Or, if permanent monitoring in several deep layers is
required such as for underground injection wells, then the permanent type
multiple completion well should be considered.
Figure 9.6 illustrates the construction of a gun-perforated well. This
type of well is commonly drilled and logged to define the depth of !all the
permeable layers. The casing is installed with centralizers and cement
grout is placed in the annul us from the bottom up to surround the casing.
The grout prevents intercommunication between permeable layers along the
outside of the casing. Other types of multicompletion wells are covered in
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*•
•*.*,:**.*.•.*.• t i •: *sus
.V*i* •.•*»<*•*..%•. *n"«'.^
•V:--^-*-,-,:"-^ .^r
-—•" ;---;-feo
••&
borehole
casing
cement grout
layer open for testing
layers perforated,
tested, and plugged
Figure 9.6 Multiple Completion Well, for One-Time Sampling
233
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detail in the Manual of Ground Water Quality Sampling Procedures.(1)
9.6 COLLECTION OF GROUND WATER SAMPLES
The importance of proper sampling of wells cannot be overemphasized.
Even though the well being sampled may be correctly located and constructed,
special precautions must be taken to ensure that the sample taken from that
well is represent!ve of the ground water at that location and that the
sample is neither altered nor contaminated by the sampling and handling
procedure.
9.6.1 Representative Samples
To obtain a representative sample of the ground water it must be
understood that the composition of the water within the well casing ;and in
close proximity to the well is probably not representative of the overall
ground water quality at that sampling site. This is due to the possible
presence of drilling contaminants hear the well and because important
environmental conditions such as the oxidation reduction potential may
differ drastically near the well from the conditions in the surrounding
water bearing materials. For these reasons it is highly desirable that a
well be pumped or bailed until the well is thoroughly flushed of standing
water and contains fresh water from the aquifer. The recommended length of
time required to pump or bail a well before sampling is dependent on many
factors including the characteristics of the well, the hyrogeological nature
of the aquifer, the type of sampling equipment being used, and the
parameters being sampled. The time required may range from the time needed
to pump or bail one bore volume to the time needed to pump several bore
volumes. A common procedure is to pump or bail the well until a minimum of
four to ten bore volumes have been removed.
Other factors which will influence the time required to flush out a
well before sampling include the pumping rate and the placement of the
pumping equipment within the column of water in the well bore. Care should
be taken to ensure that all of the water within the well bore is exchanged
with fresh water. For example, recent studies have shown that if a pump is
lowered immediately to the bottom of a well before pumping, it may take some
time for the column of water above it to be exchanged if the transmissivity
of the aquifer is high and the well screen is at the bottom of the casing.
In such cases the pump will be pumping primarily water from the aquifer.
Gibb notes that removing all water from the well bore is only possible if
the well is pumped dry and suggests two alternative approaches: (a) monitor
the water level in the well while pumping. When the water level has
"stabilized" most if not all of the water being pumped is coming from the
aquifer; (b) monitor the temperature and pH of the water while pumping.
When these two parameters "stabilize," it is probable that little or no
water from casing storage is being pumped.
9.6.2 Sample Collection
This section is primarily concerned with the collection of water
234
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samples from the saturated zone of the subsurface. The type of system used
is a function of the type and size of well construction, pumping level, type
of pollutant, analytical procedures and presence or absence of permanent
pumping fixtures. Ideally, sample withdrawal mechanisms should be
completely inert; economical to manufacture; easily cleaned, sterilized and
reused; able to operate at remote sites in the absence of external power
sources; and capable of delivering continuous but variable flow rates for
well flushing and sample collection.
Most water supply wells contain semi permanently mounted pumps which
limit the options available for ground water sampling. Existing in place
pumps may be line shaft turbines, commonly used for high capacity wells;
submersible pumps very commonly used in domestic wells for high head, low
capacity applications, and more recently for municipal and industrial uses;
and jet pumps commonly used for shallow, low capacity domestic water
supplies. The advantage of in place pumps are that water samples are
readily available and non representative stagnant water in the well bore is
generally not a problem. The disadvantages are that excessive pumping can
dilute or increase the contaminant concentrations from what is
representative of the sampling point, that water supply wells may produce
water from more than one aquifer, and contamination and/or adsorption may be
a problem when sampling for organics.
The advantage to collecting water samples from monitoring wells without
in place pumps is in the flexibility of selecting equipment and procedures.
The principal disadvantage is the possibility of a non representative sample
either through collecting stagnant water that is in the well bore or
introducing contamination from the surface by the sampling equipment or
procedures.
9.6.2.1 Bailers
One of the oldest and simplest methods of sampling water wells is the
use of bailers. A bailer may be in the form of a weighted bottle or capped
length of pipe on a rope or some modification thereof which is lowered and
raised generally by hand. Two examples are represented in Figures 9.7 and
9.8. The modified Kemmerer Sampler is often used for sampling surface
waters as well as ground waters. The Teflon bailer was developed
specifically for collecting ground water samples for volatile organic
analysis.
Advantages of Bailers:
1. It can be constructed from-a wide variety of materials
compatible with the parameter of interest.
2. Economical and convenient enough that a separate bailer
may be dedicated to each well to minimize cross contamination.
3. No external power source required.
4. Low surface to volume ratio reduces outgassing of volatile
organics.
235
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Figure 9.7 Modified Kemmerer Sampler
236
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NICKEL WIRE
CABLE
1-1/4" O.D. x 1" I.D. TEFLON
^-EXTRUDED TUBING,
18 TO 36" LONG
3/4" DIAMETER
GLASS MARBLE
1" DIAMETER TEFLON
EXTRUDED ROD
.5/16" DIAMETER
HOLE
Figure 9.8 Teflon Bailer
237
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Disadvantages of Bailers:
1. Sometimes impractical to evacuate stagnant water in a well
bore with a bailer.
2. Transfer of water sample from bailer to sample bottle can
result in aeration.
3. Cross-contamination can be a problem if equipment is not
adequately cleaned after each use.
9.6.2.2 Suction Lift Pumps
There are a variety of pumps available that can be used when the water
table is within suction lift, i.e., less than about 20 feet. Centrifugal
pumps are the most commonly available, are highly portable and have pumping
rates from 5 to 40 gpm. Most of these require a foot valve on the end of
the suction pipe to aid in maintaining a prime. .
Peristaltic pumps are generally low volume suction pumps suitable for
sampling shallow, small diameter wells. Pumping rates are generally low but
can be readily controlled within desirable limits. One significant
limitation is the low pumping rates used initially to flush out the well
bore. Another limitation is that electrical power is required. Hand
operated diaphragm pumps are available that can be operated over a wide
range of pumping rates which facilitates rapid evacuation of a well bore
initially and lower controlled pumping rates for subsequent sampling. One
major advantage is portability.
Advantages:
1. Generally, suction lift pumps are readily available, relatively
portable, and inexpensive.
Disadvantages:
1. Sampling is limited to ground water situations where water
levels are less than about 20 feet.
2. May result in degassing and loss of volatile compounds,
9.6.2.3 Portable Submersible Pumps
Ground water investigations.routinely require the collection of samples
from depths which often exceed the limitations of conventional sampling
equipment. One such system consists of a submersible pump which can be
lowered or raised in an observation well, using 300 feet of hose that
supports the weight of the pump, conveys the water from the well, and houses
the electrical cable and an electrical winch and spool assembly. A portable
generator provides electricity for both the pump and the winch and the
entire assembly can be mounted in a pickup or van.
Advantages:
1. Portable. Can be used to sample several monitoring wells in a
238
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brief period of time.
2, Dependent upon size of pump and pumping depths, relatively
large pumping rates are possible.
Disadvantages:
1. Submersible pumps currently available require a minimum well
casing inside diameter of three inches.
2. Requires the services of a relatively large service type
vehicle, either a van or truck.
3. With conventional construction materials, it is not suitable
for sampling for organics.
9.6.2,4 Air Lift Samplers
There are a number of adaptations to the basic method of applying air
pressure to a water well to force a water sample out the discharge tube. A
high pressure hand pump and any reasonably flexible tubing can be used as a
highly portable sampling unit. A small air'compressor and somewhat more
elaborate piping arrangements may be required at greater depths as shown in
Figure 9.9. The primary limitation to this sampler is the potential
alteration of water quality parameters, the amount of air pressure that can
be safely applied to the tubing and finding a suitable source of compressed
air.
Advantages:
1. Can be used as portable or permanently installed sampling
system.
2. Can be used to both pre pump and sample.
Disadvantages:
1. Not suitable for pH sensitive parameters such as metals.
2. If air or oxygen is used, oxidation is a problem.
3. Gas stripping of volatile compounds may occur.
9.6.2.5 Nitrogen Powered, Continuous Delivery, Glass and Teflon
With the interest in sampling ground water for trace organic pollutants
has come the need for a noncontaminating, nonadsorbing pump, for collecting
samples below the suction lift. Based on an initial design by Stanford
University, Rice University has developed a ground water sampling system
consisting of a two stage all glass pump'connected by Teflon tubing and
powered by nitrogen gas. The system contains four basic units as shown in
Figure 9.10: (a) a two stage glass pump;'(b) solenoid valve and electronic
timer; (c) nitrogen tank and regulator; and (d) columns for organic removal
from the ground water.
Advantages:
1. Portable, AC power not required.
239
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Di scharge
Needle valve
Pressure gage
Iron cap
Quick air hose
coupler
Ground, surface
* •
/
yX;V,
siss
. ».*..* •*•;•
41
**^I*.*« **••*."
MS
* *^****»** *
* * _*** »***_*» *
•1-1/4" or 1-1/2" plastic
Figure 9,9 Air-Lift Sampler
240
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H20
H20
N2
1
o
N2
Thick Wall Glass
Diameter 1.5"
Length 17"
BOTTOM
PUMP
TOP
PUMP
N2
*Inf1uent Water f
Figure 9.1CJ Nitrogen Powered, Glass-Teflon Pump
241
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2. Constructed of noncontamlnating, nonadsorbing materials.
3. Variable flow rates up to 45 gallons/hour are obtainable.
4. Can be used in well casings with minimum diameters of about
two inches.
Disadvantages:
1. Requires high purity nitrogen gas.
2. Glass construction is somewhat more fragile than otherimater-
ials.
3. Stripping of CCL from water may be a problem for pH sensitive
parameters.
4. Gas stripping of volatile compounds may occur.
9.6.2.6 Gas Operated Squeeze Pump
These systems consist principally of a collapsible membrane inside a
long rigid housing, compressed gas supply and appropriate control valves.
When the pump is submerged, water enters the collapsible membrane through
the bottom check valve. After the membrane has filled, gas pressure is
applied to the annular space between the rigid housing and membrane, forcing
the water upward through a sampling tube. When the pressure is released,
the top check valve prevents the sample from flowing back down the discharge
line, and water from the well again enters the pump through the bottom check
valve. A diagram of the basic unit is shown in Figure 9.11.
Advantages:
1. Wide range in pumping rates are possible. :
2. Wide variety of materials can be used to meet the needs of the
parameters of interest.
3. Driving gas does not contact the water sample, eliminate
possible contamination or gas stripping.
4. Can be constructed in diameters as small as one inch and
permits use of small economical monitoring wells.
5. Highly portable.
Disadvantages:
1. Large gas volumes and long cycles are necessary for deep
operation,
2. Pumping rates cannot match rates of submersible, suction or
jet pumps.
3. Commercial units relatively expensive; approximately $1000
for units currently available.
9.6.2.7 Gas Driven Piston Pump
A modification of pumps developed by Bianchi (4) and Smith (5) has been
reported by Signer (6) for collecting samples from wells of two inch or
larger diameter. The pump is a double acting piston type operated by
compressed gas. The driving gas enters and exhausts from the gas chambers
242
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1/4" AIRLINE
CHECK VALVE
1" PVC PIPE
FLEXIBLE
DIAPHRAM
CHECK VALVE
Figure 9.11 Gas-Operated Squeeze Pump
243
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between the two pistons and the intermediate connector that joins them.
Buil't in check valves at each end of the pump allow water to enter the
cylinders on the suction stroke and to be expelled to the surface on the
pressure stroke. Present designs are constructed basically of stainless
steel, brass and PVC. Pumping rates vary with the pumping head but pumping
rates of 2.5 to 8 gallons/hour have been noted at 100 feet of pumping head.
Advantages:
1. Isolates the sample from the operating gas.
2. Requires no electrical power source.
3. Operates continuously and reliably over extended periods of
time.
4. Uses compressed gas economically.
5. Can be operated at pumping heads in excess of 500 meters.
Disadvantages:
1. Relatively expensive; in excess of $3000 for the continuously
operating unit.
2. Particulate material may damage or inactivate pump unless the
suction line is filtered.
3. Low pumping rates.
9.6.2.8 Special Sampling Considerations For Organic Samples (7)(8)
Sampling for organic parameters is a new and in no way, a routine
procedure at this time. The equipment and methods in current use are
largely in the research state. The concepts are fundamental, however, and
any particular item can be modified to suit actual field needs.
Furthermore, these rather expensive and sophisticated procedures may not be
.necessary for sampling or monitoring all areas. New techniques and
materials are continuously being examined, which in turn should lead to the
development of more sophisticated yet more economical sampling methods. The
points that must be kept in mind include the potential for sample
contamination and the extremely fine detail, subject to expert rebuttal,
that may be necessary in a legal action.
9.6.2.9 Grab Samples
Grab samples of ground water for non volatile organic analysis may be
collected by utilizing the system shown in Figure 9.12 where the sampled
water contacts only sterile glass and Teflon, and the water table is within
suction lift. The sampled water is then carefully transferred to
appropriate glass sample containers for shipment to the laboratory.
For sampling at depths beyond suction lift, a noncontaminating
submersible pump should bemused to pump the ground water to the surface,
through scrupulously cleaned Teflon tubing, directly into appropriate sample
containers.
The most commonly employed sample containers are 40 ml glass ;vials for
244
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TEFLON CONNECTOR
6MM I.D.
,GLASS TUBING
6MM O.D.
r
TEFLON TUBING
6MM 0,0.
WELLCASING
TYGON
TUBING
OUTLET
1-LITER ERLENMEYER
PERISTALTIC
PUMP
Figure 9.12 System for Grab Sampling
245
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analyses requiring small sample volumes, such as extractable organics. Both
types of containers are equipped with Teflon lined screw caps. Like;all
glassware used in the sampling and analytical procedures, sample containers
are thoroughly cleaned prior to use by washing with detergent, rinsing
extensively with tap water followed by high purity deionized water and
heating to 560 C for two hours.
Grab samples of ground water to be analyzed for highly volatile
organics are usually obtained by means of a Teflon bailer noted in Figure
9,8. Use of the systems described previously is less desirable than bailers
for volatile organic samples because of possible stripping of highly
volatile constituents from the sample under the reduced or elevated pressure
occurring in systems using pumps.
9.6.2.10 Continuous Procedures :
Continuous procedures, using selected adsorbents to concentrate and
recover organic constiuents from relatively large volumes of ground water,
may be employed for sampling organic pollutants in situations where the
analytical sensitivity and sample uniformity attainable by grab sampling are
inadequate. These procedures are applicable for most organic pollutants
except those of very high volatility.
A special sampling system is shown in Chapter 12, Figure 12.10 in which
the water is pumped directly from the well through Teflon tubing (6 mm O.D.)
to two glass columns of adsorbent in series. In this illustration, ;a
peristaltic pump is located on the outlet side of the columns for sampling
with suction lift. A noncontaminating submersible pump may be used,at
greater depths and may be superior for practically all sampling uses. All
components of the systems that contact the water sample prior to emergence
from the the second column are, with the exception of the adsorbent, glass
or Teflon.
Columns prepared from macroreticular resins, activated carbon,: and
polyamide particles are also shown in Chapter 12, Figures 12.7 and 12.8.
Of these materials, macroreticular resin (XAD-2, Rohm and Haas Company,
Philadelphia, Pennsylvania) has been the most convenient and generally
useful and is the current adsorbent of choice.
Sampling is conducted by continuously pumping ground water through the
sampling systems at flow rates usually ranging from 10 to 30 mL/min. The
volumes sampled are dependent on the desired sensitivity of analysis. For
analysis by modern gas chromatographic techniques, sampling of 50 liters of
water is sufficient to provide a sensitivity of at least one ug/liter (1 ppb)
for almost all compounds of interest. Volumes sampled are determined by
measuring the water leaving the sampling systems in calibrated waste
receivers.
9.6.2.11 Volatile Organics in the Unsaturated Zone
For investigations pertaining to organic pollution of ground water, it
is often desirable to sample water in the unsaturated zone to detect and
246
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follow the movement of pollutants that are migrating toward the water table.
This is a particularly difficult task in the case of highly volatile
compounds, including the low molecular weight chlorinated hydrocarbons such
as trichloroethylene.
Soil water samples may be collected using the device depicted in Figure
9.13, which consists of a sampler, a purging apparatus, and a trap connected
to sources of nitrogen gas and vacuum. The soil solution sampler consists of
a 7/8 in. O.D.(2.2 cm) porous ceramic cup, a length of 3/4 in. O.D. Teflon
or PVC pipe and a Teflon stopper fitted with 3 mm O.D. Teflon exhaust and
collection tubes. The length of the pipe is dictated by the depth of
sampling desired, which is limited to a maximum of about 20 feet. The
device is basically a suction lysimeter and, consequently, suffers from the
limitations of such equipment.
The purging apparatus and trap are parts of the Tekmar LSC-1 liquid
sample concentrator to which have been added Teflon valves and "Tape-Tite"
connectors. The purging apparatus is borosilicate glass, while the trap
consists of Tenax GC porous polymer (60/80 mesh), packed in a 2 mm x 28 cm
stainless steel tube plugged with silane treated glass wool. The purge gas
is ultra high purity, oxygen free nitrogen. Vacuum is provided by a
peristaltic pump.
Prior to sample collection, the purging apparatus is cleaned with
acetone and distilled water and then baked at 105 to 108 C for at least an
hour. In the field, it is rinsed thoroughly with distilled water between
samples with special care being exercised to force the rinse water through
the glass first.
The soil solution sampler is driven to the bottom of a pre augered 19
mm (0.75 in) diameter hole. This is done very carefully to insure intimate
contact between the ceramic cup and the soil.
Prior to collection of a sample, the exhaust tube is opened to the
atmosphere and the collection tube disconnected and pumped to remove any
solution that may have leaked into the tube through the porous cup. Then,
the collection tube is reconnected to the purging apparatus, the exhaust
tube closed with a pinch clamp, and 5 to 10 ml of solution is collected by
closing valve C and opening valves A and B. After sample collection, the
exhaust tube is opened to remove from the sampler and collect on the trap
any of the compounds that may have volatilized in the sampler. Following
this procedure, A is closed and C opened. Nitrogen gas is then bubbled
through the solution at a rate of 40 mL/min for ten minutes to purge
volatile organics from solution. Traps are capped and returned to the
laboratory for analysis within six hours of collection or for storage at
-20 C for later analysis.
Low density, immiscible organics include gasoline and other chemicals
and petrochemicals which have specific gravities less than water and which
are likely to be present in aquifers as a separate phase because of low
solubility in water. These chemicals tend to float on the v/ater surface in
a water table environment and commonly occupy the capillary fringe zone
247
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TRAP
ro
-p»
oo
EXHAUST
TUBE
POROUS
CERAMIC
CUP
VACUUM
SOIL SOLUTION
SAMPLER
FRITTED-"
GLASS
DISC
PURGING
APPARATUS
Figure 9.13 Soil-Water Sampling Device for Volatile Orgam'cs
-------
above the water table. In a confined aquifer these chemicals are found
along the upper surface of the permeable material and also within the
overlying confining layer.
Care must be exercised to insure that the well screen extends
significantly into both the water saturated zone and the overlying
formation. This design will insure that contaminants in the capillary
fringe or overlying aquitard, as well as ground water, enter the well to be
•observed. A well screen with abundant open area such as a wire wrapped
screen is important in allowing free flow of the petrochemicals into the
well.
With the above considerations in mind, nearly any of the drilling
methods which permits a well of at least 3 inches ID to be constructed is
satisfactory.
Sampling procedures for low density, immiscible organics differ
substantially from those for other pollutants. It is necessary to sample at
least two and sometimes three distinct layers of depths within the sampling
well.
After the well is initially constructed it should be developed and
pumped to remove invaded water, then, it should sit idle for at least
several days to allow the water level and floating layer of petrochemicals
to fully stabilize.
Measurement of the thickness of the petrochemical layer may then be
accomplished by using a water level indicator gel with a steel tape to
determine the depth to the water surface. A weighted float may be used to
determine the depth to the top of the petrochemical layer. The difference
between these two readings is the thickness of the petrochemical layer.
Electric water-level sounders will not work properly for these
determinations.
A sample of the floating petrochemicals may then be taken using a
bailer which fills from the bottom. Care should be taken to lower the
bailer just through the petrochemical layer, but not significantly down into
the underlying ground water.
Samples of the ground water at the bottom of the screen and at some
intermediate location, such as the mid point of the screen, may also be
obtained with a bailer. However, in order to avoid mixing the waters, a
separate casing is temporarily lowered inside the permanent well casing.
This casing is equipped with an easily removed cap on the bottom so that no
fluid enters the casing until it has reached the desired depth for sampling.
The cap is then knocked free of the bottom of the casing, allowing water to
enter from that specific depth to be sampled by bailer. At significant
depths below the petrochemicals, several full bailers of water may be
withdrawn and discarded before the sample is taken to obtain a fresh
formation sample.
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9.7. SAMPLING GROUND WATER SUBSURFACE SOLIDS
A common misconception regarding ground water monitoring is that
absence of contaminants in the ground water precludes a contamination
problem. In many cases, an effective evaluation of the potential impact on
ground water quality of activities releasing pollutants into the earth's
crust, requires samples of subsurface earth materials, both saturated and
unsaturated, as well as ground water samples. There are several principal
reasons for this requirement: (a) only by analysis of earth solids from the
unsaturated zone underlying pollutant releasing activities can those
pollutants which are moving very slowly toward the water table because of
sorption and/or physical impediment be detected and their rates of movement
and degradation measured. Almost all pollutants are attenuated to some
degree in the subsurface, especially in the unsaturated zone. The degree of
attenuation and rate of movement varies greatly between different pollutants
and different subsurface conditions but many of the mobile pollutants may
not be detected in ground water until the activities releasing them have
been in operation for protracted periods. Because of their potential for
long term pollution of ground water, it is imperative that the behavior of
these pollutants in the subsurface be established at the earliest
practicable time; (b) analyses of pollutants in subsurface solid samples
from the zone of saturation are needed for a realistic evaluation of the
total extent and probable longevity of pollution in an aquifer. Such
analyses provide a measure of the quantity of pollutants which are sorbed on
aquifer solids and which are in equilibrium with, and in essence serve as a
reservoir for, pollutants in solution in the adjacent ground waterj (c)
microbial populations which may be involved in the biological alteration of
pollutants in subsurface formations are likely to be in such close ,
association with subsurface solids that they will not be present in well
waters in numbers which are quantitatively indicative of their presence in
the formations; hence, analysis of subsurface solids are needed for accurate
evaluation of such populations and; (d) even when the best well construction
and ground water sampling procedures are used, it is difficult to completely
eliminate the possibility that contaminating surface microbes may be present
in ground water samples. Solids taken from the interior of cores carefully
obtained from the zone of saturation probably provide the most authentic
samples of aquifer microorganisms that can be obtained.
As with ground water samples, successful sampling of subsurface earth
solids requires both acquisition of cores of subsurface solids at desired
depths in a manner minimizing potential contamination and proper handling
and processing of the core material obtained to insure its integrity and
produce samples suitable for analyses.
There are a variety of procedures and equipment that have been used to
collect earth materials for classification and identification of physical
characteristics. Tools as simple as a shovel or backhoe can and have been
used and a number of designed samplers have also been used for this purpose.
Because of the ability to penetrate greater depths and to maintain the
physical integrity of the samples, most designed samplers employ some type
of coring mechanism. The most common procedures use a thin-wall steel tube
(core barrel) which is forced into the undisturbed soil at the bottom of a
250
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bore hole. This is sometimes refered to as drive sampling. Core barrels
are generally from one inch to three inches in diameter and 12 to 24 inches
long. When the core barrel is retrieved, friction will usually retain the
sample inside, at least in most unsaturated materials. Additional details
on subsurface solid sampling are covered in the Manual of Ground Water
Sampling Procedures.(1)
9.8 PRESERVATION AND HANDLING PROCEDURES FOR GROUND WATER PARAMETERS
9.8.1 Organic and InorganicParameters
Follow the preservation and handling procedures outlined in Chapter 17
for inorganic and organic parameters.
9.8.2 H1c rob i o1ogjc a1 Pa ramete rs
There are several different methods for obtaining a ground water
sample. Each of these methods differ in their advantages and disadvantages
for obtaining samples for microbiological analyses.
The majority of ground water samples are obtained using preexisting
wells which have existing in place pumps. This limits the precautions the
sampler can take to ensure a non-contaminated sample. Samples should be
obtained from outlets as close as possible to the pump and should not be
collected from leaky or faulty spigots or spigots that contain screens or
aeration devices. The pump should be flushed for 5 to 10 minutes before the
sample is collected. A steady flowing water stream at moderate pressure is
desirable in order to prevent splashing and dislodging particles in the
faucet or water line.
To collect the sample, remove the cap or stopper carefully from the
sample bottle. Do not lay the bottle closure down or touch the inside of
the closure. Avoid touching the inside of the bottle with your hands or the
spigot. The sample bottle should not be rinsed out and it is not necessary
to flame the spigot. The bottle should be filled directly to within 2.5 cm
(1 inch) from the top. The bottle closure and closure covering should be
replaced carefully and the bottle should be placed in a cooler (4 to 10 C)
unless the sample is going to be processed immediately in the field.
If a well does not have an existing in-place pump, samples can be
obtained by either using a portable surface or submersible pump or by using
a bailer. Each method presents special problems in obtaining an
uncontaminated sample.
The main problem in using a sterilized bailer is obtaining a
representative sample of the aquifer water without pumping or bailing the
well beforehand to exchange the water in the bore for fresh formation water.
This is difficult since such pre sampling activities must be carried out in
such a way as to not contaminate the well. Care must also be taken with
bailers to not contaminate the sample with any scum on the surface of the
water in the well. This is usually done by using a weighted, sterilized
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sample bottle suspended by a nylon rope and lowering the bottle rapidly to
the bottom of the well.
The use of portable pumps provides a way of pumping out a well before
sampling and thus providing a more representative sample, but presents a
potential source of contamination if the pumping apparatus cannot be
sterilized beforehand. The method of sterilization will depend on what
other samples are taken from the well since the use of many disinfectants
may not be feasible if the well is also sampled for chemical analyses. If
disinfection is not ruled out by other considerations, a method of
sterilizing a submersible pump system is to submerge the pump, and any
portion of the pump tubing which will be in contact with the well water,
into a disinfectant solution and circulating the disinfectant through the
pump and tubing for a recommended period of time.
The most widely used method of disinfection is chlorination due to its
simplicity. Chlorine solutions may be easily prepared by dissolving either
calcium or sodium hypochlorite in water. Calcium hypochlorite, CaCOCl^j is
available in a granular or tablet form usually containing about 70 percent
of available chlorine by weight and should be stored under dry and cool
conditions. Sodium hypochlorite, NaOCl, is available only in liquid form
and can be bought in strengths up to 20% available chlorine. Its most
available form is household laundry bleach, which has a strength of about 5%
available chlorine, but should not be considered to be full strength if it
is more than 60 days old. The original percentage of available chlorine
will be on the label.
Table 9.1 gives the quantities of either calcium hypochlorite or
laundry bleach required to make 100 gallons of disinfectant solution of
various concentrations. Fresh chlorine solutions should frequently be
prepared because the strength will diminish with time. The proper strength
to use in disinfection is dependent upon many factors including pH and
temperature. As a rule of thumb, hypochlorite solutions of 50 to 200 ppm
available chlorine and a contact time of 30 minutes should be effective at
pH ranges of 6 to 8 and temperatures of greater than 20 C. After
disinfection the pump should be carefully placed in the well and then pumped
to waste until the chlorine is thoroughly rinsed from the pump system.
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TABLE 9.1 QUANTITIES OF CALCIUM HYPOCHLORITE, (70 PERCENT)
AND HOUSEHOLD LAUNDRY BLEACH (5 PERCENT) REQUIRED
TO MAKE 100 GALLONS OF DISINFECTANT SOLUTION
Desired Chlorine
Strength
Dry Calcium
Hypochlorite, 1b.
5% Household
Bleach, Quarts
50 ppm
100 ppm
15 ppm
200 ppm
0.07
.14
.20
.30
0.4
0.8
1.2
1.6
If the pump cannot be disinfected, then the pump and tubing should be
carefully handled to avoid gross surface contamination and the well should
be pumped for 3 to 10 bore volumes before taking a sample. It may be
desirable after pumping to pull the pump and take the sample with a sterile
bailer.
In those cases where the water level in the well is less than 20 to 30
feet below the surface, a surface vacuum pumping system can be used for
flushing out the well and withdrawing a sample. An ideal apparatus for this
is depicted in Figure 9.14. This apparatus consists of two lengths of tubing
which are sterilizable by autoclaving and portable vacuum system. The two
tubing lengths which are attached side-by-side to each other, are sterilized
in the laboratory in large covered containers. In the field they are lowered
into a well using sterile gloves, attached to a vacuum flask on the inlet side
of the pump. Large volume sampling for viruses or pathogenic bacteria can be
accomplished by substituting filters or columns with various adsorbents in
place of~the vacuum flask.
Standing water is prevented from entering the sampling tubing upon
insertion into the well by making the sampling tube a few feet shorter than
the flushing tubing and turning on the pump to the flushing system as the
tubing is put into the well.
To sample wells using this type of system requires a relatively large
autoclave, several sets of sampling tubing, and a relatively shallow ground
water.
Springs are unlikely to yield representative samples of an aquifer due
to surface contamination close to a spring's discharge unless the spring has
an extremely fast flow and the outlet is protected from surface
contamination.
Lastly, interpretation of analytic results may be difficult in some
cases since surface contamination of wells due to poor drilling and
completion practices is common. In cases where drinking water supplies are
involved, a thorough inspection of the well is required to eliminate surface
contamination down the well bore as a source of contaminants. Disinfection
of the well by approved methods (9),(10), and resampling may be advisable,
if disinfection will not affect the well for other sampling purposes.
253
-------
Autoclavable
Tubing for
flushing
we! 1
Bypass system for
flushing well
K
Autoclavable Tubing
for sampling well
1 foot shorter than
flushing tubing
WELL CASING
1-LITER ERLENMEYER
(Sterile)
Figure 9.14 System for Microbiological Sampling of Wells Using
a Suction-Lift Pump
254
-------
9.9 SAMPLING OF DRINKING WATER
Under the Safe Water Drinking Act, Public Law 93-523, Section 1412, EPA
or states are required to regulate contaminants that may adversly affect
public health. Subsequent regulations may require the monitoring of one or
more of the following parameters:
PRIMARY DRINKING WATER PARAMETERS
Arsenic Silver 2,4 D
Barium Fluoride 2,4,5-TP(Silvex)
Cadmium Nitrate Turbidity
Chromium Endrin Coliform bacteria
Lead Lindane Gross alpha and beta
Mercury Methoxyclor Total trihalomethanes
Selenium , Toxaphene
SECONDARY DRINKING WATER CONTAMINANTS
CopperChlorideColor
Manganese Sulfates Odor
Iron pH Foaming Agents
Zinc Corrosivity Total Dissolved Solids
9.9.1 Sampling Location
The sampling locations required by Interim Primary Drinking Regulations
for each parameter group are shown in Table 9.2.
The two major considerations in determining the number and location of
sampling points are that they should be: 1) Representative of each different
water source entering the system, and 2) representative of conditions within
the system, such as dead ends, loops, storage facilities and pressure zones.
Examples of selecting sampling points are as follows:(15)
Example 1. One Source to Distribution System
Figure 9.15 demonstrates one source, in this case the clear
well effluent, entering the distribution system. Therefore,
only one sampling location is needed for such parameters as
turbidity and trihalomethanes.
Example 2. One Source to Distribution System
Figure 9.16 demonstrates one" source, in this case the treatment
plant, entering the distribution system. Therefore, only one
sampling location is needed for such parameters as turbidity
and trihalomethanes.
255
-------
TABLE 9.2 SAMPLING LOCATIONS AND FREQUENCIES
ro
en
CTl
What Tests
(Community
System)
Inorganics
and
SWDC*
Organics
Total Tri-
halome thanes
MTP
Turbidity
Col i form Bacteria
Radiochemicals
(Natural )
Radiochemicals
(Han-made)
Sodium
SDHC
What Tests
( No n -community
System)
Inorganics
and
SWDC
(at state option)
Organics
(at state option)
Total Tri-
halomethanes
MTP
Turbi di ty
CoHform Bacteria
Radiochemicals
(Natural )
(at state option)
Radiochemicals
(Man-madej-
(at state option)
Sodium
SOHC
Samp! e
Location
At the consumer's
faucet
At the consumer's
faucet
Consumer's tap
25 percent of
samples have
maximum residence
time in system
At the point (s)
where water enters
the distribution
system
At the consumer's
faucet
At the consumer's
faucet
At the consumer's
faucet
At the point(s)
where water from
each plant enters
-distribution system
At the point(s)
where water enters
the distribution
System
Frequency
(Community System)
Systems using surface water:
EVERY YEAR
Systems using ground water only:
EVERY THREE YEARS
Systems using surface water:
EVERY THREE YEARS
Systems using ground water only:
STATE OPTION
Systems using surface water:
See Figure 9.21
Systems using surface water:
See Figure 9.21
Systems using surface water:
DAILY
Systems using ground water only:
STATE OPTION
Depends on number of people
served by the water system (See
Table 9.1
Systems using surface water:
EVERY FOUR YEARS
Systems using ground water only:
EVERY FOUR YEARS
Systems using surface water serving
populations greater than 100,000:
EVERY FOUR YEARS
All other systems:
STATE OPTION
Systems using surface or
part surface water
ANNUALLY
Systems using ground. water:
EVERY THREE YEARS
All Systems:
STATE OPTION
How Often
(Non-Comraunity System)
All Systems;
STATE OPTION
All Systems:
STATE OPTION
Systems using surface water:
See Figure 9.21
Systems using ground water;
See Figure 9,21
Systems using surface or surface
and ground water:
DAILY
Systems using ground water only:
STATE OPTION
AH Systems:
ONE PER QUARTER
(for each quarter water is
served to public)
All Systems;
STATE OPTION
All Systems:
STATE OPTION
All Systems:
STATE OPTION
Al 1 Systems :
STATE OPTION
* Secondary Drinking Water Contaminants
-------
Treatment
Plant 1
Treatment
Plant 2
Clear
Well
Treatment
Plant
Clear
Well 1
Clear
Well 2
Figure 9.15 One Source Figure 9.16
Entering Distribution System Water From One Treatment Plant
Entering Two Clear Wells
V
/
ter Lines
S
/
0,
<^
c© G
/^
Main Water
t
/
/x
Treatment Plant
Fi gure 9.17
Branch Distribution System
©
s\
Figure 9.18
Loop Distribution System
257
-------
Example 3. Conditions Within the System .
Figure 9.17 demonstrates sampling locations to determine
representative sampling locations in a branch distribution
system. Sampling location A is for the entry into the
distribution, point B representative of the water in the main
line, point C of water in the main dead end, and D and. E of
water quality in the branch and branch dead end, respectively.
Turbidity and trihalomethanes are sampled at point A whereas
all others parameteres are sampled at points B through D.
The frequency of microbiological sampling is proportioned
to the population served. For a a population of 3500,'
the required minimum number of samples per month is four.
Thus, all four microbiological samples could be taken at the
same time from points B, C, D and E. However, representative
sampling means representative in time and location. Therefore,
sampling should occur at points B and E at mid-month and points
C and D at the end of the month.
Example 4. Conditions Within the System
Figure 9,18 demonstrates sampling locations for a Loop distri-
bution system. Sampling location A is for entry into the
distribution whereas locations D and C represent water
quality in the main line loop and point C in one of the
branch line loops.
Example 5. Combined Branch and Loop Systems
Figure 9.19 demonstrates sampling locations for entry into
the distribution system and conditions within a combined branch
and loop system. An evaluation of sampling locations ifollows:
Sampling Point
A Unacceptable. Point not located in the distribution
system or at its entry. Point to be maintained for
operational monitoring only.
B Acceptable. Point on main loop in high-pressure zone;
should produce representative samples for that part of
system.
C. Acceptable. Point on branch loop in the high-pressure
zone; serves for storage flow to the system.
D. Judgmental. Many authorities advise against dead end
sampling points as they do not produce representative
samples. Possibly true; however, consumers do take water
from branch-line dead ends. In this example there;are
seven branch-line dead ends, no doubt serving significant
numbers. It would be representative to have one or two
sample points on these branch lines at or near the end.
(Two in here because of the three source waters and two
pressure zones.)
258
-------
I\J
B and SDWA
O
O
T3
to
c*
(D
Booster Pump . .*" Check Valves -* , .
SDWA (11
SDWA
SDWA f6
Storage
1
High Pressure Zone T
Low Pressure Zone I
~i n n *
SDWA
SDWA
Well
Water
Source
SDWA
i D &nd SDWA
E and
SDWA{T
Storage
F and SDWA (5)
Storage
-------
E. Acceptable. Located on the main loop of low pressure
zone and representing water from treatment plant 2, the
well, the storage tanks at F, or any combination.
(Depending on system demand at sampling time.)
F, Judgmental. Although important to sample water
quality into system from storage, it might be better
to collect the sample at junction of stored water li-ne '
and main loop, unless consumers are served directly
from the storage branch.
G. Judgmental. Only one dead end need be sampled in low-
pressure system. If D selected, A not needed.
Two turbidity sampling points are shown as points 11 and 12, since
waters from parallel treatment plants enter two separate clear wells.
Notice there is no sampling point where the well water source enters the
system since groundwater sources need not be monitored for turbidity.
Sample location is somewhat judgmental, however, general guidelines for
selection are:
1. Distribute the Sampling points uniformly throughout the system.
2. Locate the sample points in both types of distribution system
configurations: loops and branches and in proportion to the
relative number of loops and branches.
3. Locate adequate representative sample points within each zone if
there is more than one pressure zone.
4. Locate points so that water coming from storage tanks can be
sampled and sample during time of high-demand times.
5. For systems having more than one water source, locate the sample
points in relative proportion to the number of people served by
each source. [
6. Check pressures during the proposed sampling times so that the
source of sampled water can be determined. It is possible that
excessive demand in one part of the distribution system can cause
water to be brought into that area from other parts of the system
and perhaps other sources.
9.9.2 Sampling Frequency ;
Sampling frequencies required fay the Interim Primary Drinking Water
Regulations (11-14) depend on the parameter group being monitored:
1. Microbiological Sampling - Take coliform bacteria samples at
regular time intervals in proportion to the population being served
as shown in Table 9.3.
Based on a history of no coliform bacterial contamination and on a
sanitary survey by the State showing the water system to be
supplied solely by a protected ground water source and free of
sanitary defects, a community water system serving 25 to 1,000
persons, with written permission from the State, may redute this
260
-------
Table 9.3 FREQUENCY OF MICROBIOLOGICAL SAMPLING
Population
Served
Min. No. of
Samples per
Month
Population
Served
Min. No. of
Samples per
Month
25 to 1,000 1 90,000 to 96,000 95
1,001 to 2,500 2 96,001 to 111,000 100
2,501 to 3,300 3 111,001 to 130,000 110
3,301 to 4,100 4 130,001 to 160,000 120
4,101 to 4,900 5 160,001 to 190,000 130
4,901 to 5,800 6 190,001 to 220,000 140
5,801 to 6,700 7 220,001 to 250,000 150
6,701 to 7,600 8 250,001 to 290,000 160
7,601 to 8,500 9 290,001 to 320,000 170
8,501 to 9,400 10 320,001 to 360,000 180
9,401 to 10,300 11 360,001 to 410,000 190
10,301 to 11,100 12 410,001 to 450,000 200
11,101 to 12,000 13 450,001 to 500,000 210
12,001 to 12,900 14 500,001 to 550,000 220
12,901 to 13,700 15 550,001 to 600,000 230
13,701 to 14,600 16 600,001 to 660,000 240
14,601 to 15,500 17 660,001 to 720,000 250
15,501 to 16,300 18 720,001 to 780,000 260
16,301 to 17,200 19 780,001 to 840,000 270
17,201 to 18,000 20 840,001 to 910,000 280
18,001 to 18,900 21 910,001 to 970,000 290
18,901 to 19,800 22 970,001 to 1,050,000 300
19,801 to 20,700 23 1,050,001 to 1,140,000 310
20,701 to 21,500 24 1,140,001 to 1,230,000 320
21,501 to 22,300 25 1,230,001 to 1,320,000 330
22,301 to 23,200 26 1,320,001 to 1,420,000 340
23,201 to 24,000 27 1,420,001 to 1,520,000 350
24,001 to 24,900 28 1,520,001 to 1,630,000 360
24,901 to 25,000 29 1,630,001 to 1,730,000 370
25,001 to 28,000 30 1,730,001 to 1,850,000 380
28,001 to 33,000 35 1,850,001 to 1,970,000 390
33,001 to 37,000 40 1,970,001 to 2,060,000 400
37,001 to 41,000 45 2,060,001 to 2,270,000 410
41,001 to 46,000 50 2,270,001 to 2,510,000 420
46,001 to 50,000 55 2,510,001 to 2,750,000 430
50,001 to 54,000 60 2,750,001 to 3,020,000 440
54,001 to 59,000 65 3,020,001 to 3,320,000 450
59,001 to 64,000 70 3,320,001 to 3,620,000 460
64,001 to 70,000 75 3,620,001 to 3,960,000 470
70,001 to 76,000 80 3,960,001 to 4,310,000 480
76,001 to 83,000 85 4,310,001 to 4,690,000 490
83,001 to 90,000 90 4,690,001 or more 500
261
-------
sampling frequency except that in no case shall it be reduced to
less than one per quarter. The supplier of water for a non-
community water system shall sample for coliform bacteria in each
calendar quarter during which the system provides water to the
public. If the State, on the basis of a sanitary survey,
determines that some other frequency is more appropriate, that
frequency shall be the frequency required. Such frequency may be
confirmed or changed on the basis of subsequent surveys. ;
When the coliform bacteria in a single sample exceed four'per 100
milliliters, at least two consecutive daily check samples shall be
collected and examined from the same sampling point. Additional
check samples shall be collected daily, or at a frequency
established by the State, until the results obtained from at least
two consecutive check samples show less than one coliform'bacterium
per 100 milliliters. When coliform bacteria occur in three or more
10 ml portions of a single sample, at least two consecutive daily
check samples shall be collected and examined from the same
sampling point. Additional check samples shall be collected daily,
or at a frequency established by the State, until the results
obtained from at least two consecutive check samples show[no
positive tubes. .
When coliform bacteria occur in all five of the 100 ml portions of
a single sample, at least two daily check samples shall be
collected and examined from the same sampling point. Additional
check samples shall be collected daily, or at a frequency
established by the State, until the results obtained from at least
two consecutive check samples show no positive tubes.
2. Other Parameter Groups - See table 9,2, Sampling Locations and
Frequencies.
3. Total Trihalomethanes - See Figures 9.20 and 9.21.
9.9.3 Representative Samples
Follow the procedures specified below to assure the collection of a
representative sample and to maintain the integrity of the sample:
1. Collect samples at faucets which are free of contaminating devices
such as screens, aeration devices, hoses, purification devices or
swiveled faucets. Check faucet to be sure it is clean; if the
faucet is in a state of desrepair, select another sampling
location. ',
2, Collect samples in areas free of excessive dust, rain, snow or
other sources of contamination.
3. Collect samples from faucets which are high enough to put; a bottle
underneath, generally the bath tub, without contacting the mouth of
the container with the faucet.
4. Open faucet and thoroughly flush. Generally 2 to 3 minutes will
suffice, however longer times may be needed, especially in the case
of lead distribution lines. Generally, the water temperature will
262
-------
THE MINIMUM MONITORING REQUIREMENT IS FOUR SAMPLES PER
QUARTER PER PLANT. REDUCED MONITORING REQUIREMENTS MAY BE
APPROPRIATE IN CERTAIN CASES; UPON WRITTEN REQUEST FROM THE
PUBLIC WATER SYSTEM, STATES MAY REDUCE THE REQUIREMENTS
THROUGH CONSIDERATION OF APPROPRIATE DATA AS FOLLOWS:
SURFACE WATER SYSTEM
1
4 SAMPLES PER QUARTER
FOR TTHM
ONE YEAR OF DATA:
TTHM CONSISTENTLY
BELOW 0.10 MG/L
fc
NO
CONTINUE 4
SAMPLES PER QUARTER
YES
CHANGE IN
TREATMENT
OR SOURCE
4
STATE JUDGMENT ON
REDUCED MONITORING*
MINIMUM: 1 SAMPLE PER
QUARTER FOR TTHM
TTHM >0.10 MG/L
•FACTORS FOR CONSIDERATION:
• MONITORING DATA, MTP, TTHM, TOC
• QUALITY AND STABILITY OF SOURCE WATER
• TYPE OF TREATMENT
Figure 9.20
Total trihalomethanes sampling frequency for
surface water systems
263
-------
THE MINIMUM MONITORING REQUIREMENT IS FOUR SAMPLES PER
QUARTER PER PLANT; SYSTEMS USING MULTIPLE WELLS DRAWING RAW
WATER FROM A SINGLE AQUIFER MAY WITH STATE APPROVAL BE
CONSIDERED AS ONE TREATMENT PLANT. REDUCED MONITORING
REQUIREMENTS MAY BE APPROPRIATE IN CERTAIN CASES; UPON
WRITTEN REQUEST FROM THE PUBLIC WATER SYSTEM, STATES MAY
REDUCE THE REQUIREMENTS THROUGH CONSIDERATION OF APPROPRIATE
DATA AS FOLLOWS:
GROUNDWATER SYSTEM
SAMPLE FOR MTP
MTP > 0.10 MG/L
MTP < 0.10 MG/L
STATE JUDGMENT ON
REDUCED MONITORING*
MINIMUM: 1 SAMPLE
PER YEAR FOR MTP .
4 SAMPLES PER QUARTER
FOR TTHM
I
ONE YEAR OF DATA:
TTHM CONSISTENTLY
BELOW 0.10 MG/L
CONTINUE 4
SAMPLES PER QUARTER
STATE JUDGMENT ON
REDUCED MONITORING*
MINIMUM: 1 SAMPLE PER
QUARTER FOR TTHM
TTHM >0.10 MG/L
"FACTORS FOR CONSIDERATION:
• MONITORING DATA, MTP,TTHM, TOC
• QUALITY AND STABILITY OF SOURCE WATER
» TYPE OF TREATMENT
Figure 9.21 Total trihalomethanes sampling frequency for
ground water systems
264
-------
TABLE 9.4 PRESERVATION AND HOLDING TIMES FOR SDW PARAMETERS
Parameter
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Nitrate
Selenium
Silver
Fluoride
Chlorinated
hydrocarbons
Chlorophenoxys
Fecal Col i form
TTHM's
Residual
Chlorine
Turbidity
1,2
Preservative
Cone HNO-j to pH 2
Cone HNO^ to pH 2
Cone HNO^ to pH 2
Cone HMO- to pH 2
Cone HNO~ to pH 2
Cone HNO~ to pH 2
o
Cone H2S04 to pH 2
Cone HNO- to pH 2
Cone HNOj to pH 2
None
Refrigerate at 4 C
as soon as possible
after collection
Refrigerate at 4°C
as soon as possible
after collection
Refrigerate at 4°C
as soon as possible
after collection
See Chapter 17
None
None
3
Container
P or G
P or G
P or G
P or G
P or G
G
P
P or G
P or G
P or G
P or G
G with foil or
Teflon-lined
cap
G with foil or
Teflon-1 ined
cap
Sterile P or G
P or G
P or G
1 4
Maximum '
Holding
Time
6 months
6 months
6 months
6 months
6 months
38 days
14 days
14 days
6 months
6 months
1 monthc
14 days0
7 days
30 hours
1 hour
1 hour
1
If a laboratory has no control over these factors, the laboratory director
must reject any samples not meeting these criteria and so notify the
authority requesting the analyses.
?
"If HN03 cannot be used because of shipping restrictions, sample may be
initially preserved by icing and immediately shipping it to the laboratory.
Upon receipt in the laboratory, the sample must be acidified with cone
to pH 2. At time of analysis, sample container should be thoroughly
rinsed with 1:1 HN03; washings should be added to sample.
P = Plastic, hard or soft; G = Glass, hard or soft.
i
In all cases, samples should be analyzed as soon after collection as
possible.
5Well-stoppered and refrigerated extracts can be held up to 30 days.
265
-------
TABLE 9.5 PRESERVATION AND HOLDING TIMES FOR SOW RADIOLOGICAL PARAMETERS
Parameter
Gross alpha
Gross beta
Stronti um-89
Strontium-90
Radium-226
Radium-228
Cesium-134
Iodine-131
Tritium
Uranium
Photon
emitters
2
Preservative
Concl
Concl
Concl
Concl
Concl
Concl
Concl
None
None
Concl
Concl
.HC1
.HC1
.HC1
.HC1
.HC1
.HC1
.HC1
.HC1
.HC1
or
or
or
or
or
or
to
or
or
HNO,
HNO,
HNO,
HNO:;
HNO^
HNO,
PH 3
HNO,
o
HN03
to
to
to
to
to
to
2
to
to
pH
PH
pH
pH
PH
PH
pH
pH
25
25
2
2
2
2
2
2
P
P
P
P
P
P
P
P
G
P
P
or
or
or
or
or
or
or
or
or
or
G
G
G
G
G
G
G
G
G
G
Instru-, ,
mentation'
A or B
A
A
A1
A^B, or D
A ;
A 'or C
A,
E
F
C
1
FEDERAL REGISTER Vol. 41 No. 133 July 9 1976
"It is recommended that the preservative be added to the sample at the time
of collection unless suspended solids activity is to be measured. However,
if the sample must be shipped to a laboratory or storage area,
acidification of the sample (in its original container) may be delayed for
a period not to exceed 5 days. A minimum of 16 hours must elapse between
acidification and analysis.
P = Plastic, hard or soft; G = Glass, hard or soft.
i
A = Low background proportional system; B = Alpha scintillation system; C =
Gamma spectrometer (Nal(Tl)or GE(Li}); D = Scintillation cell (radon)
system; E = Liquid scintillation system (section C.2.a); F = Fluorometer
(section C.1.1).
3If HC1 is used to acidify samples which are to be analyzed from gross alpha
or gross beta activities, the acid salts must be converted to nitrate salts
before transfer of the samples to planchets. ;
266
-------
stabilize which indicates flushing is completed, then adjust the
flows so it does not splash against the walls of bathtubs, sinks or
other surfaces. Collect samples.
5. Collect microbiological samples with sterile containers and caps.
Handle container caps aseptically, i.e hold the cap in one hand
without touching the inner surface while sampling. It
necessary to flame the faucet, however faucets in good
be flushed thoroughly before microbiological sampling.
6. For most samples, fill container to one to one and one
from the top. For Trihalomethanes and other organics,
procedures specified in Chapter 12.
7. Handle, preserve, and adhere to holding times between sampling and
analyses as shown in Tables 9.4 and 9.5: (4)
8. Identify sample immediately after collection using an appropriate
numbering system. Identification includes such written information
(non-smearing ink) as water source, location, time and date of
collection, and collectors name. Record chlorine residual if
applicable.
9. Record above data and any additional remarks in a field notebook.
is not
repair must
half inches
follow
9.10 REFERENCES
1.
2.
3.
4.
5.
6.
7.
8.
Marion, R..D. Scalf, J.F. McNabb W.J. Dunlap R.L. Cosby and J.S.
Fryberger. Manual of Ground Water Quality Sampling Procedures. Robert
S. Kerr Environmental Research Lab, Office of Research and Development,
U.S. Environmental Protection Agency, Ada, Oklahoma, May 1980.
Procedures Manual for Ground Water Monitoring at Solid Waste Disposal
Facilities. U.S. Environmental Protection Agency. EPA 53Q/SW-611.
August, 1977.
Keys, W.S. and L.M. MacCary. Application of Borehole Geophysics to
Water Resources Investigations. U.S. Geological Survey Techniques of
Water Resource Investigations. Book 2 Chapter E-l pp. 1-126. 1971.
Bianchi, W.C. C.E. Johnson and E.E. Haskell. A Positive Action Pump
for Sampling Small Bore Wells. Soil Science Society of America.
Proceedings, Vol. 26. No.l. 1962.
Smith, A.J. Water Sampling Made Easier with New Device.
Drillers Journal. July-August, 1976.
The Johnson
Signer, D.C. Gas Driven Pump for Ground Water Samples. U.S.G.S. Water
Resources Investigation. 78-72 Open file report. July, 1978.
Minning, R.C.
1980.
Keck Consulting Services, Inc. Private Communication.
Dunlap, W.J. J.F. McNabb M.R. Scalf and R.L. Cosby. Sampling for
Organic Chemicals and Microorganisms in the Subsurface. EPA - 600/2-
77-176. August, 1977.
267
-------
9. Cambell, M.D. and J.H. Lehr. Water Well Technology. McGraw Hill Book
Company. New York. 1973. :
10. Manual of Individual Water Supply Systems. EPA - 430/9-74-007. USEPA
OWP. Washington. 1974.
11. Environmental Protection Agency. Office of Water Supply. National
Interim Primary Drinking Water Regulations. EPA-570/9-76-003. July
1976.
12. Environmetnal Protection Agency. Interim Primary Drinking Water
Regulations-Control Of Organic Chemical Contaminants in Drinking Water.
Federal Register 40 CFR part 141 volume 43 No.28 February 9 1978.
13. Environmental Protection Agency. Interim Primary Drinking Water
Regulations-Amendments. Federal Register, 40 CFR part 141 Volume 45
No.168 August 27 1980.
14. Environmental Protection Agency. Manual For The Interim Certification
Of Laboratories Involved In Analyzing Public Drinking Water Supplies.
EPA 600/8-78-008. May 1978. :
15. American Water Works Association. The Safe Water Drinking Act'- Hand-
book for Water System Operators. Report Number IP-10M-1/78-1612.
268
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CHAPTER 10
SAMPLING SLUDGES
10.1 BACKGROUND
The quantity and composition of sludge varies with the characteristics
of the wastewater from which it is concentrated and with the concentration
process used. Some common types of sludge are:
1. Coarse screenings from bar racks
2. Grit
3. Scum from primary settling tanks
4. Primary settling tank sludge
5. Return and waste activated sludge
6. Floatation or gravity thickened sludge
7. Aerobic or anaerobic digester sludge
8, Drying bed sludge
9, Vacuum filter cake
10. Sludge press cake
11. Centrifuge sludge
12. Fine screening backwash water
13. Sand filter backwash water
14. Sludges from special treatment processes such as the treatment of
industrial wastes or combined sewer overflows.
Sludge sampling methods are usually confined to municipal or
industrial plants. The sampling programs employed are concerned mainly
with the following sludges: primary settling tank sludge, return and waste
activated sludge, thickened sludge, digester sludge, and the resulting
cakes produced by sludge drying methods.
10.2 OBJECTIVES OF SAMPLING PROGRAMS
10.2.1 Process Control
Most sludges are measured for the following process control reasons:
1. Optimization of sludge drawoff procedure
2. Determination of the efficiency of a concentration process
3. Determination of the loadings to the process
4. Evaluation of feed material for subsequent sludge conditioning
techniques which may vary with changing feed characteristics
5. Control of the activated sludge process, i.e., the mixed liquor
269
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suspended solids (MLSS) concentration
6. Control of blanket depths in clarifiers
7. Determination of sludge characteristics that may be detrimental
to digester processes
10.2.2 Research
Research projects require specific sampling techniques which are
determined by the program.
10.3 PARAMETERS TO ANALYZE
The parameters to analyze will depend on the objective of the process.
For example, analysis of total and suspended solids content of the sludge
is necessary to determine the efficiency of a sludge thickening process. A
guide for parameters to analyze is shown in Figure 10.1 Additional
parameters to analyze include: heavy metals, pesticides, and nutrients.
10.4 LOCATION OF SAMPLING POINIS
10.4.1 Flowing Sludges
10.4.1.1 Piping
Collect samples directly from the piping through a sampling cock
having a minimum I.D. of 3.8 cm (1.5 inches). (1)
10.4.1.2 Channels
Collect samples at the measuring weirs, or at another point where the
sludge is well mixed. ;
10.4.2 Batch Sludges
10.4.2.1 Digesters :
Collect samples from a mixed sink which is fed through lines attached
at different levels in the digester. Be certain to waste sludge
accumulated in the lines prior to sampling. (1)
10.4.2.2 Tanks i
Mix tank thoroughly and collect samples. Collect samples at various
depths and locations in the tank. Mix samples together prior to analysis.
10.4.3 Specific "In Plant" Locations
The following locations are recommended for sludge sampling at
wastewater treatment plants:
270
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Temperature
PH
BOD
SS
TS
TVS
Alknljnlcy
Volatile Acids
Settleable Solids
00
c
c
4)
£
(J
•ft
&
r»»
>
Q
hi
0
F1
2/W
1/D
1/D
L2
Su
Su
1
P
c
o
•H
jj
(0
O
p-1
^
a
r
2/W
1/D
1/D
00
n
c
^
u
1
i
Su
Su
1
P
c
o
*J
(9
00
3
•H
*J
c
ft)
u
1/W
1/D
1/D
1/H
C
c
1
P
c
HI
v
3
0
n
oi
LJ
(X
6
3
3
-W
n
>
p
2/W
1/D
1/D
c
o
•r4
4J
%
i<
n
•a
c
o
u
Is
S
S
u
u
c
0
U
(0
•o
1-(
K
O
kJ
<
u
u
3
Mn
1/D
2/D
1/D
1/D
Is
S
S
S
1
U
1. F • frequency
2. L " location
Where:
Mn - monitor
H - hour
D * day
W - week
AD - at drauoff
Su « subnatant
1 - influent
P - product cludge or cake
C • centrate
F - filtrate
Is - in situ
S - supernatant or decant
U - underflow
Figure 10.1 Recommended minimum sampling programs for
municipal wastewater sludge treatment
processes (2)
271
-------
1. Primary Sludge - Draw sludge from the settling tank hoppers into a
well or pit before pumping, mix well and then collect a
representative sample directly from this well. Alternately,
collect samples from openings in pipes near the sludge pumps or
from the pump itself. (3)
2. Activated Sludge - Collect samples at:
a. the pump suction well
b. the pump or adjacent piping ,
c. the point of discharge of the return sludge to the
primary effluent.
The sample point should be located in a region of good agitation
to the suspension of solids. (3)
3. Digested Sludge - Collect samples at the point of the discharge of
the digester drawoff pipe to the drying beds or the drying
equipment. (4) :
4. Bed Dried Sludge - Collect equal sized samples at several points
within the bed without including sand. Mix thoroughly. (3)
5. Filtered Sludge - Collect equal size portions (possibly by using a
cookie cutter) at the filter discharge. (3)
10.5 FREQUENCY OF SAMPLING
The extreme variability of sludges creates a need for frequent
sampling to achieve accurate results. Each composite sample should be
composed of at least 3 individually obtained samples. (3) Sample batch
operations at the beginning, middle and end of a discharge, or more
frequently if high variability is suspected. (3) Tapped lines should also
be sampled in three separate intervals because of variations in the sludge
.at the drawoff source (i.e., clarifier, digester, etc.). Minimum ;
frequencies for various sludge processes are included in Figure 10.1
10.6 NUMBER OF SAMPLES
The number of samples is determined from the frequency and the number
to include in the composite. Refer to Figure 10.1 for minimum guidelines.
10.7 TYPE OF SAMPLE :
Collect grab samples when analyzing for a parameter which is unstable,
for example ammonia, or when analysis is required as soon as possible (for
example, sludge volume index test for activated sludge samples).
Analysis of composite samples is recommended in all other situations
to reduce the effects of sludge variability. Use at l.east three individual
samples to form the composite. Wherever possible, collect frequent
discrete samples and composite according to flow rate. (5)
272
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10.8 METHOD OF SAMPLING
Automatic samplers are not commonly available for sludge sampling due
to the high fouling potential and solids content of the wastewater. Use
manual sampling techniques in most situations unless special adaptations
can be made.
10.9 VOLUME OF SAMPLE AND CONTAINER TYPE
Use a wide mouth container to sample sludges. The size and material
of container depends on the parameters to be analyzed. In general, a clean
borosilicate glass container is preferable to reduce the possibility of
adsorption of organics to the container wall; however, polyethylene can be
used for inorganic analyses. See Chapter 17 for more details.
10.10 PRESERVATION AND HANDLING OF SAMPLES
Preservation methods are discussed in Chapter 17. Completely mix the
sample after a preservative is added to disperse the chemical for adequate
preservation. Considerable mixing or homogenization is required prior to
aliquot removal to insure representative portions are obtained.
10.11 FLOW MEASUREMENT
For flowing lines do not use flow measuring devices which will be
easily fouled by solids (for example, orifice, venturi meter). Use a
permanently installed self-cleaning or non-obstructive device such as a
magnetic flow meter.
Batch sludge discharges are not easily quantified in terms of volume
discharged. Make estimates from pump capacity, the change in depth in a
tank or well and time of pumping or other appropriate methods.
10.12 REFERENCES
1. Joint Committee of American Society of Civil Engineers and Water
Pollution Control Federation. Sewage Treatment Plant Design - WPCF
Manual of Practice, No 8, 1967.
2. Estimating Laboratory Needs for Municipal Wastewater Treatment Plants.
U.S. EPA, Office of Water Program Operations, Washington, D.C., Report
No. EPA 430/9-74-002. Operation and Maintenance Program. June 1973,
pp. A-l to A-29.
3. New York State Department of Health. Manual of Instruction for Sewage
Treatment Plant Operators, New York, New York, Health Education
Service, 308 p.
273
-------
Technical Practice Committee - Subcommitte on Operation of Wastewater
Treatment Plants. Operation of Wastewater Treatment Plant - WPCF
Manual of Practice No. 11, 1970.
Technical Practice Committee - Subcommittee on Sludge Dewatering,
Sludge Dewatering - WPCF Manual of Practice No. 20, 1969.
274
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CHAPTER 11
SUSPENDED SOLIDS SAMPLING
Suspended solids are a key water quality parameter since they impact
such activities as the design of wastewater treatment plants, turbidity
removal in drinking water, sediment control in streams, and disinfection.
The concentration of other water quality parameters is related to suspended
solids, since the solid structure may contain biochemical and chemical
oxygen demand materials, trace metals, nutrients, pesticides and toxic or
hazardous materials adsorbed on the surface.
11.1 REPRESENTATIVE SAMPLING THEORY
For solids distributed uniformly within a given system and containing
the same chemical and physical properties, any sample taken shall be
representative. However, most systems in practice contain suspended solids
varying in physical and/or chemical properties; in practice, the degree of
non-uniformity ranges from slight to large and subsequently causes problems
in obtaining a representative sample.
11.1.1 Sampling Error
The error in sampling suspended solids in the field or subsampling from
a previously collected sample is attributed to two factors: 1) solid
segregation effects; and 2) random distribution of solids:
a) Segregation Effects - Error in sampling due to significant
differences between solid particles in specific gravity, size, and
shape.
b) Random Solid Distribution - Error due to imperfect sampling or
homogenization procedures. For example, a mixture of 1,000 green
beads and 5,000 yellow beads, color being the only difference, is
homogenized as completely as possible. However, a sample of 24
beads will not always contain four green beads but may vary from
zero to eight. The magnitude of this type of error depends on the
size of the sample being withdrawn.
Segregation effects are more pronounced in field sampling since solids
are difficult to mix throughly or process through devices that eliminate
solid segregation. Random effects are more pronounced in the laboratory
since segregation effects can be minimized by homogenization of the
wastewater sample.
275
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11.2 SEGREGATION SAMPLING ERROR
Typical waters/wastewaters contain solid particles which vary in size,
shape, and specific gravity. These properties influence the particle
settling rate which must be exceeded to keep the solid suspended and prevent
segregation of solids within the water/wastewater system being sampled. The
theoretical settling rate of a spherical solid in a quiescent aqueous medium
is given by Stokes1 Law: ;
18 v
Where: V = settling velocity
D = sphere diameter
S = specific gravity of solid
& '
S = specific gravity of water
w
v = kinematic viscosity of water
g = acceleration of gravity ;
11.2.1. Particle Size
Stokes1 Law indicates that the settling velocity increases with
increasing particle diameter. The size of solids found in water/wastewater
varies as shown in Figure 11.1. Approximately 90% of all solids are less
than 1 mm in size.
41.2.2 Specific Gravity of Solids
Stokes' Law also indicates that the settling rate increases with
increasing specific gravity of the solid. The specific gravity erf suspended
solids found in waters/wastewaters varies from 0.8 to 3.5, examples are
shown below:
Material
Oils, other organics
Flocculated mud particles with 95% water
Municipal
a) Effluents
b) Influent
c) Grit
Aluminum Floe
Iron Floe
Sand
Calcium Carbonate Precipitate
Specific
Gravity
0.95
1.03
1.15
0.8 - 1.6
1.2 - 1.7
1.18
1.34
2.65
2.70
276
-------
I I I I
1
0.9
0.8
0.7
0.6
0.5
0.4
g 0.3
0.2
0.1
.09
.08
.07
.06
.05
.04
."03
.02 -
.01
CODE
M Secondary Effluent
© Surface Runoff
O Municipal Grit Chamber Effluent
0 Areated Grit Chamber Effluent
W Digested Sludge
9 Ohio River Water
Qj Combined Storm Sewers
10 15 20 30 40 50 60 70
Percentage Less Than By Weight
80 85 90
98
Figure 11.1 Suspended solid particle sizes in various waters/waste waters (1).
277
-------
11.2.3 Shape of Solids
The settling velocity formula of Stokes applies to spherical particles,
however, most waters/wastewaters contain solids of non-spherical shape. In
general solids with irregular shapes settle at lower rates than spherical
particles of the same specific gravity. (2) Shapes encountered in
waters/wastewaters include:
Type Shape
a) Microbiological and paper scraps Placoid
b) Sand grains Angular
c) Plastic monomers Spherical
d) Fibers - wood, rayon, nylon Cylindrical-stringy
11.2.4 Settling Velocities
Experimentally determined settling velocities (1) for various solid
types are:
a) Erosion soil run-off - Ranges from .015 - 10.1 cm/sec
(.0005 - 0.33 ft/jsec).
b) Grit chamber effluent - Mean of 0.54 cm/sec (.0017 ft/sec).
c) Primary clarifier design for settable solids removal - .028 - .043
cm/sec (.0009 - .0014 ft/sec).
11.2.5 Scouring Velocity
Sampling of horizontal flowing open channels and pipes for suspended
solids must be conducted at velocities which assures adequate mixing.
Stratification or segregation of solids are classified as follows:
a) Bed load - Solids that move by saltation, rolling, or sliding along
or near the bottom surface.
b) Suspended solids or suspended load - solids that are supported by
the upward components of turbulent currents and that they stay in
suspension for appreciable amounts of time. The equation for
estimating the velocity (3) to transport solids is: '
Vs = (9) (S - 1} Dg = Rl/6 B (S - 1) Dg
Where:
V = Scouring velocity
S = Specific gravity of the particle
Dg = Diameter of particle
B = 0.04 to start scouring and 0.8 for scouring
f = Friction factor - .03 for concrete
n = Manning roughness factor - See Table 11.1
278
-------
R = Hydraulic Radius - See Table 11.2
g = 32.2 ft/sec2.
TABLE 11.1 VALUES OF MANNING'S ROUGHNESS COEFFICIENT n
Glass, plastic, machined metal 0.010
Dressed timber, joints flush 0.011
Sawn timber, joints uneven 0.014
Cement plaster 0.011
Concrete, steel troweled 0.012
Concrete, timber forms, unfinished 0.014
Untreated gunite 0.015 - 0.017
Brick work or dressed masonry 0.014
Rubble set in cement 0.017
Earth, smooth, no weeds 0.020
Earth, some stones and weeds 0.025
Natural river channels:
Clean and straight 0.025 - 0.030
Winding, with pools and shoals 0.033 - 0.040
Very weedy, winding and overgrown 0.074 - 0.150
Clean straight alluvial channels O.OSld1/6
d D-75 size in ft.
TABLE 11.2 VALUES OF HYDRAULIC RADIUS RH FOR
VARIOUS CROSS SECTIONS _ _
R _ area of stream cross section; "equivalent diameter" = 4R.,
H ~ wetted perimeter
Shape of Cross Section
H
Pipes and ducts, running full:
Circle, diam. = D 7-
Annulus, inner diam. = d. outer diam. = D •* — ^ — L.
Square, side = D -r
(continued)
279
-------
TABLE 11.2 (continued)
Shape of Cross Section R,,
Rectangle, sides a,b gff + Dy
Ellipse, major axis = 2a, minor axis = 2b Ki a+
Open channels or partly filled ducts:
Rectangle, depth = y, width = b .
Semicircle, free surface on a diam. D
Wide shallow stream on flat plate, depth
Triangular trough, = 90°, bisector
vertical, depth = y, slant depth = d
Trapezoid (depth = y, bottom width = b) : . ,
Side slope 60° from horizontal yp y/ —
b + 4y/ /T
K >?
Slide slope 45° Y +
b + 2/2y
* Values of K. If S = (a - b)/(a + b) ,
S = 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
K = 1.010 1.023 1.040 1.064 1.092 1.127 1.168 1.216 1.273
11.3 FIELD SAMPLING
Collection of suspended solids 1n the field can be performed manually
or automatically, however significant differences in results can be expected
when sampling non-homogeneous systems such as raw municipal wastewaters as
shown 1n Table 11.3.(4) In addition, automatic samplers with high intake
velocities, of 2-10 ft/sec, will capture about one and a half to two times
more solids than manual flow proportional or manual grab sampling methods.
However, as the system becomes more homogeneous with respect to solids,
intake velocities or sampling method becomes less important in obtaining
comparable results as indicated by the final effluent values in Table 11.3.
280
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Intake velocities above or below stream velocities for suspended
sediment solids (specific gravity 2.65) within Stokes1 Law, for example,
Reynolds' number less than 1,0, do not result in any significant error as
shown in Figure 11.2.(5) However, as the particle size increases,
significant error occurs when the intake/stream velocity ratio varies from
1.0. This relationship (Figure 11.3) between the Relative Sampling Rate
Ratio as error in concentration has a negative slope. When the intake
velocity is less than the stream velocity, more solids will be collected and
when the intake velocity exceeds the stream velocity, less solids shall be
collected.
The rationale for this inverse relationship is illustrated in Figure
11.4. Therefore, in order to insure representative sampling, the
intake/stream velocity ratio should be unity (isokinetic flow).
TABLE 11.3 RICHARDS-GEBAUR SEWAGE TREATMENT PLANT NON-FILTERED SOLIDS
COMPARISON RATIO OF SAMPLING METHOD VALUE TO MANUAL FLOW VALUE
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
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
Date
May 22
1.155
0.431
1.0
0.697
1.537
0.700
1.0
0.975
0.743
0.769
1.0
0.794
May 23
1.755
1.046
2.0
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
Intake
Velocity
ft/sec.
2-5
2
__
— —
2.5
0.25
__
--
2.5
.02
__
•"" —
11.4 LABORATORY SUBSAMPLING
Subsampling from previously collected field samples may be subject to
error resulting from segregation effects, such as particle size and specific
gravity. As shown in Figure 11.5, the shake and pour technique achieves 93%
recovery of solids with specific gravities in the range of 2.2-2.6 and
particle sizes less than 50 microns; magnetic stirring improves percent
recoveries.
281
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1201
100
S 80
ID
O
t-
o
B.
60
S 40
o 20
-20
-40
Sampling rates
O — 0.25 normal
•jr — 0.50 normal
D — 3.0 normal
Normal sampling rate: ratio
of intake velocity to stream
velocity equals 1.0.
Range of Stokes* Law
0.01 0.02 0.03 0.04 0.06 0.1 0.2 0.3 0.4 0.5
Sediment Size in Millimeters
Figure 11.2 Relation of sediment size to errors in sediment concentration.
ID
O
t»
e
o.
80
60
40
» 20
2
c
-------
' stream lines
sediment path
intake
//////
a. Normal sampling rate intake velocity equal to stream velocity.
b. Sampling rate below normal as illustrated, ratio of intake velocity to
stream velocity approximately 1/3.
c. Sampling rate above normal as illustrated, ratio of intake velocity
approximately 3.
Figure 11. A Flow patterns at mouth of sampler intake.
283
-------
ro
oo
100
90
80
,5 70
« 60
•D
o
-------
Subsampling recoveries of 100% for solids having specific gravities
ranging from 1.05-1.14 can be expected up to 500 microns. Therefore, to
insure representative subsampling, the entire sample should be thoroughly
blended and as large an aliquot used as possible.
11.5 GUIDELINES FOR SAMPLING OF SUSPENDED SOLIDS
Minimize sampling errors caused by segregation effects by sampling in a
well mixed or turbulent zone.
Minimize random sampling errors in the laboratory by homogenizing the
sample and using as large a sample aliquot as possible.
Maintain the flow rate in the sample lines to effectively transport
suspended solids. For horizontal runs, the velocity must exceed the
scouring velocity and in vertical runs, the velocity must exceed the
settling velocity of the particle.
For solids falling within the range of Stokes' Law, consistent
representative samples can be obtained at intake/stream ratio either greater
or less than 1.0. For solids falling outside Stokes1 Law, an intake/stream
ratio of 1.0 is recommended.
The geometry of the intake has little effect upon the representa-
tiveness of the sample, however, the intake should face into the stream at
no more than 20 degrees from the direction of stream flow.
11.6 REFERENCES
1. Physical and Settling Characteristics of Particulates in Storm and
Sanitary Wastewaters. EPA 670/2-75-011, April, 1975.
2. Design and Testing of a Prototype Automatic Sewer Sampling System.
EPA 600/2-76-006, March, 1976.
3. WPCF Manual of Practice. No. 9, ASCE, 1970. p. 88.
4. Harris, D.J., W.J. Keffer. Wastewater Sampling Methodologies and Flow
Measurement Techniques. EPA 907/9-74-005, 1974.
5. Interagency Committee on Water Resources, A Study of Methods Used in
the Measurement of Analysis of Sediment Loads in Streams: Laboratory
Investigation of Suspended Sediment Samplers, Report No. 5, 1940.
285
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CHAPTER 12
SAMPLING, PRESERVATION AND STORAGE CONSIDERATIONS
FOR TRACE ORGANIC MATERIALS
Organic compounds in water and wastewater are regulated by the Safe
Drinking Water Act (SDWA) and the Clean Water Act (CWA).
The SDWA has established maximum contaminant levels (1}(2) for the
following organic chemicals:
a) Chlorinated hydrocarbons:
Endrin Methoxychlor
Lindane Toxaphene
b) Chlorophenoxys:
2,4-D 2,4,5-TP (Silvex)
c) Trihalomethanes: '
Trichloromethane Bromodichloromethane
Dibromochloromethane Tribromomethane
Listed in Table 12.1 are chemicals which have been detected in drinking
water supplies and for which the possibility of adverse health effleets
exists. The presence of these chemicals is indicative of chemical
pollution; this list is not exhaustive, but serves merely as a guide.(3)
A court settlement agreement involving the Natural Resources Defense
Council, et al. and the U.S. Environmental Protection Agency (EPA Consent
Decree) resulted in EPA publishing a list of 65 compounds and classes of
compounds (Table 12.2). The Consent Decree required that EPA regulate these
compounds via the Federal Water Pollution Control Act (subsequently amended
by the Clean Water Act). EPA's expanded list of organic priority pollutants
(Table 12.3) is an outgrowth of the Consent Decree's list of 65. '
Specific toxic pollutant effluent standards will be promulgated for the
organic priority pollutants, thus far they have been promulgated (4)(5)(6)
for the following:
Aldrin/Dieldrin Endrin
Benzidine Toxaphene
DDT (ODD, DDE) PCB's
286
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TABLE 12.1 CHEMICAL INDICATORS OF INDUSTRIAL CONTAMINATION (23)
I. Aliphatic halogenated hydrocarbons:
Methane derivatives:
Dichloromethane Dichlorodifluoromethane
Trichlorofluoromethane Carbon Tetrachloride
Ethane derivatives:
1,1-dichloroethane 1,1,1-trichloroethane
1,2-dichloroeth.ane ; 1,1,2-trichloroethane
hexachloroethane 1,1,2,2-tetrachloroethane
Unsaturated hydrocarbons:
Trichloroethylene 1,2-dichloroethene
letrachloroethylene 1,3-dichloropropene
Vinyl chloride Hexachlorobutadiene
1,1-dichloroethene 2-chlorovinyl ether
Other halogenated compounds:
1,1-dichloropropane Bis(2-chloroethyl) ether
bis(2-chloroisopropyl) ether
II. Cyclic aliphatic compounds:
Chlorinated hydrocarbons:
Lindane Kepone
BHC Toxaphene
Cyclodienes:
Chlordane Heptachlor
Aldrin Heptachlor epoxide
Dieldrin Endrin
Hexachlorocyclopentadiene
III. Aromatic hydrocarbons:
3,4-benzof1uoranthene f1uoranthene
benzo(k)fluoranthene indeno(l,2,3,c,d)pyrene
1,12-benzoperylene benzo(a)pyrene
Benzenes: . . • , :
Benzene Ethyl benzene
Toluene Propylbenzene
Xylenes • • , Styrene
Halogenated aromatics:
Chlorinated naphthalenes DDE
Chlorobenzene ODD
287
-------
TABLE 12.1 (continued)
Halogenated aromatics:(continued)
Dichlorobenzenes Chlorophenols
Polychlorinated biphenyls Trichlorobenzenes
Pentachlorophenol 4-bromophenylphenyl ether
Bromobenzene 4-chlorphenylphenyl ether
DDT Hexachlorobenzene
Other aromatic hydrocarbons:
Nitrobenzene Phthalate esters
Dinitrotoluene Atrazine
288
-------
TABLE 12.2 65 TOXIC POLLUTANTS OR CLASSES OF TOXIC POLLUTANTS (21)
ro
CO
M3
Acenaphthene
Acrolein
Acrylonitrile
Aldrin/Dieldrin
Antimony and compounds
Arsenic and compounds
Asbestos
Benzene
Benzidine
Beryllium and compounds
Cadmium and compounds
Carbon tetrachloride
Chlordane (technical mixture and metabolites)
Chlorinated benzenes (other than dichlorobenzenes)
Chlorinated ethanes (including 1,2 dichloroethane
1,1,1-trichloroethane, and hexachloroethane)
Chloroalkyl ethers (chloromethyl, chloroethyi,
and mixed ethers)
Chlorinated naphthalene
Chlorinated phenols
Chloroform
2-chlorophenol
Chromium and compounds
Copper and compounds
Cyanides
DDT and metabolites
Dichlorobenzenes (1,2-,1,3- and 1,4-dichlorobenzenes)
Dichlorobenzidine
Dichloroethylenes (1,1- and 1,2-dichloroethylenes)
2,4-dichlorophenol
Dichloropropane and dichloropropene
2,4 Dimethyl phenol
Dinitrotoluene
Diphenylhydrazine
Endosulfan and metabolites
Endrin and metabolites
Ethyl benzene
Fluoranthene
Haloethers
Halomethanes
Heptachlor and metabolites
Hexachlorobutadiene
Hexachlorocyclohexane (all isomers)
Hexachlorocyclopentadiene
Isophorone
Lead and compounds
Mercury and compounds
Naphthalene
Nickel and compounds
Nitrobenzene
Nitrophenols (including 2,4-dinitrophenol,
dinitrocresol)
Nitrosamines
Pentachlorophenol
Phenol
Phthalate esters
Polychlorinated biphenyls (PCB's)
Polynuclear aromatic hydrocarbons (including
benzanthracenes, benzopyrenes, benzofluoran-
thene, chrysenes, dibenzanthracenes and
indenopyrenes)
Selenium and compounds
Silver and compounds
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)
Tetrachloroethylene
Thallium and compounds
Toluene
Toxaphene
Trichloroethylene
Vinyl Chloride
Zinc and compounds
-------
TABLE 12.3 PRIORITY POLLUTANTS
I. Phthalate esters:
Dimethyl phthalate Di-n-octyl phthalate
Diethyl phthalate Bis(2-ethylhexyl)phthalate
Di-n-butyl phthalate Butyl benzyl phthalate
II. Haloethers
Bis(2-chloroethyl)ether Bis(2-ehloroethoxy)methane
Bis(2-chloroisopropyl)ether 4-chlorophenylphenyl ather
2-chloroethylvinyl ether 4-bromophenylphenyl ether
III. Chlorinated hydrocarbons:
Hexachloroethane 1,3-dichlorobenzene
Hexachlorobutadiene 1,4-dichlorobenzene
Hexachlorocyclopentadlene 1,2,4-trichlorobenzene
1,2-dichlorobenzene Hexachlorobenzene
2-chloronaphthalene
IV. Nitroaromatics and Isophorone:
Nitrobenzene 2,4-dinitrotoluene ;
2,6-dinitrotoluene Isophorone
V. Nitrosoamines:
N-nitrosodimethyl amine N-nitrosodipropylamine
N-ni trosodi pheny1 ami ne
VI. Dioxin:
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
VII. Benzidines:
Benzidine 3,3-dichlorobenzidine
VIII. Phenols:
Phenol Pentachlorophenol
2,4-dimethylphenol 4-chloro-3-methylphenol
2-chlorophenol 2-nitrophenol
2,4-dichlorophenol • 4-nitrophenol
2,4,6-trichlorophenol 2,4-dinitrophenol
4,6-dinitro-2-methylphenol
290
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TABLE 12.3 (continued)
IX. Polynuclear aromatics:
Acenaphthene
Fluoranthene
Naphthalene
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(k)f1uoranthene
Chrysene
X. Pesticides & PCB's:
Aldrin
Dieldrin
Chlordane
DDD
DDE
DDT
A-endosulfan
B-endosulfan
Endosulfan
Endrin
Endrin aldehyde
Heptachlor
Toxaphene
XI, Purgeables:
Benzene
Chlorobenzene
Toluene
Ethyl benzene
Carbon tetrachloride
1,
1,
1,
1,
2-dichloroethane
1,1-trichloroethane
1-diehloroethane
1,2-trichloroethane
1,1,2,2-tetrachloroethane
Chloroethane
Chlorodibromomethane
Tetrachloroethyl ene
XII. Acrolein & Acrylonitrile:
Acrolein
Acenaphthylene
Anthracene
Benzo(g,h,i)perylene
Fluorene
Phenanthrene
Dibenzo(a,h)anthracene
Indeno(l,2,3-cd)pyrene
Pyrene
Heptachlor epoxide
Alpha-BHC
Beta-BHC
Delta-BHC
Gamma-BHC
Toxaphene
Aroclor 1242
Aroclor 1254
Aroclor 1221
Aroclor 1232
Aroclor 1248
Aroclor 1260
Aroclor 1016
Chloroform
1,1-dichloroethylene
1,2-transdichloroethylene
1,2-di chloropropane
1,1-dichloropropylene
Methyl chloride
Methylenechloride
Methyl bromide
Bromoform
Dichlorobromomethane
Trichloroethylene
Vinyl chloride
Acrylonitrile
291
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Analytical procedures for the identification of organic compounds can
be found in a number of publications.(7 - 22) However, analytical results
are only meaningful if the sample analyzed is truly a representative sample
of the media you are testing. Chemical analysis for organics present at
trace levels places high demands on sampling techniques.
12.1 SAMPLE COLLECTION METHOD
The method of sampling can either be manual or automatic. Sampling
practices, as specified in Chapter 2, should be followed, except as
indicated in this chapter,
12.1.1 Manual Sampling
The considerations outlined in Chapter 2 are applicable. However, the
sample collector and container should be constructed of borosilicate glass
to minimize sample contamination. Grab samples obtained for analyses
of purgeable organics are sealed to eliminate entrapped air.(7) This
sample collected without headspace, is illustrated in Figure 12.1.!
Screw cap
Teflon/Silicon Septum
(Pierce #12722 or equiva-
lent)
Convex Meniscus (Sample)
40 mL borosilicate glass
vial (Pierce #13075 or
equivalent)
Figure 12.1 Collection Bottle (2.1,22)
12.1.2 Automatic Sampling
Although continuous automatic sampling is probably the best method for
collecting truly representative samples, certain precautions must be taken.
292
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Automatic sampling equipment must be free of Tygon and other potential
sources of contamination such as plastic, or rubber components.(23) Tygon
tubing is a potential source of phthalate ester contamination. Teflon is •
acceptable and may be used in the sampling system as required.
Automatic samplers used to obtain samples for trace organics analyses
may need special design features. An experimental sampler has been
developed which is capable of collecting grab samples for purgeable organics
analysis and collecting samples on accumulator columns (adsorption/absorp-
tion columns) for non-purgeable organics analyses.(24) All system
components in contact with the sample are either constructed of Teflon or
glass; this includes a specially designed Teflon-bellows pump.
Illustrations of this system are shown in Figures 12.2 through 12.6.
Sampling systems utilizing carbon or macroreticular resin in columns
have been employed for sampling organics in ground water.(25 - 27) The
accumulator column in these systems is located between the water to be
sampled and the pump, therefore, special Teflon type pumps are not needed.
These type systems are illustrated in Figures 12.7 through 12.10.
Automatic samplers can be used to collect composited samples. EPA's
600 series methods for analyzing non-volatile organic priority pollutants
reference these types of automatic samplers.
12.2 SEDIMENT SAMPLING
Sediment sampling can be classified into two general categories:
1. suspended sediments
2. bottom sediments
12.2.1 Suspended Sediment Samplers
Suspended sediment samplers should be in accordance with the suspended
solids sampling considerations of Chapter 11. When employing any suspended
sediment sampler for the collection of samples to be analyzed for organics,
materials such as Neoprene and Tygon must be replaced by inert materials
such as Teflon. In addition, valves must be cleaned to remove oil.
12.2.2 Bottom Sediment Samplers
Bottom sediment samplers are designed to obtain a sample of the
sediment mixture of which the stream bed is composed. This should be dif-
ferentiated from the bed-load. Refer to Chapter 8, Tables 8.4 and 8.5 for a
listing of these types of samplers. Replacement of contaminating materials,
such as Tygon or Neoprene, with inert materials should be considered. When
replacement of contaminating materials is not possible Or not practical, it
may be necessary to obtain specially constructed sediment collectors.
293
-------
Figure 12.2 Automatic sampler opened to show the 26 purgeable
sample bottles in position.
294
-------
Figure 12.3 A 140 ml purgeable sample bottle for the
automatic sampler.
295
-------
Figure 12.4 Automatic sampler opened to show 7 or the 14
accumulator columns. Another bank of 7 is
located behind the visible bank.
296
-------
12.5
1.8
er.
umn for
297
-------
Figure 12.6 Automatic sampler pump with container removed,
Teflon bellows are at the bottom.
298
-------
TY60N
TEFLON
TUBE
LAND SURFACE
TUBE
>*'•
CARBON
COLUMN
(3"xl8")
PERISTALTIC
WELL CASING
TEFLON
TUBE
WATER TABLE
o
GROUND WATER
PUMP
TO CALIBRATED
RECEIVER
Figure 12.7 Ground water Sampling System (26)
299
-------
30 MM
:f'--H
GLASS WOOL
PLUG
23O
MM
§ SO/SO JOINT
Figure 12,8 Carbon adsorption column (27)
300
-------
STOPCOCK
3-WAY TEFLON
GLASS WOOL
PLUG
TEFLON
CONNECTOR
12 MM 1.0.
TEFLON TUBING
6 MM I.D,
Figure 12.9 Resin adsorption column (27)
301
-------
GLASS TUBI
6 MM O.D.
TEFLON-
CONNECTOR
6 MM I.D.
TEFLON TUBING
6 MM O.D.
WELL CASING :
TYGON
TUBING
TO WASTE
RECEIVER
PERISTALTIC
PUMP
Figure 12.10 Ground-water sampling system (27)
302
-------
12.2.2.1 Sampling Site (28)
The selection of sampling sites when collecting bottom sediments for
organic analyses is extremely important. Bottom sediments, within any
river, stream, or other body of water tend to be heterogeneous. Some bottom
areas are primarily sand, while others are primarily silt and clay. Organic
pollutants adsorbed on sediments that possess a large surface-to-volume
ratio, therefore, finer sediments such as silts and clays will exhibit
higher concentrations of organics, than will coarser sediments such as sands
and gravels. Sample sites should be selected at depositing areas where silt
and clay settle out due to low current speeds. Examples are: inside of
river bends, downstream of islands or other obstructions, and near the
center of water mass in ponds, lakes, and reservoirs.
Do not sample areas that are exposed during low flow or low tide
conditions or at points immediately following the confluence of two streams.
Collect representative samples using random sampling techniques and the
grid systems specified in Chapter 8. Particle sizes should not exceed 2 mm.
12.2.2.2 Sampling Equipment (28)
Sampling equipment should be designed to minimize disturbance of the
top layers of sediments and minimize the loss of low density deposits during
the sampling process. Drag buckets and scoops are not recommended for trace
organic sampling. All samplers, regardless of type, disturb sediment fines,
however, if precautions are taken, the disturbance can be minimized.
Recommended sampling equipment and their limitations are summarized in Table
12.4.
12.3 SAMPLING LOCATION
The factors which influence the sampling location should be taken into
account as indicated in Chapter 2.
12.4 SAMPLE CONTAINER
The configuration and materials of a container which can be utilized in
the collection and storage of organic containing samples are somewhat
varied. However, the following criteria should be met:
1. Non-purgeable samples must be collected in amber glass containers
in a liter or quart volume and preferably of French or Boston round
design.(22)(23) Various glass vials have also proved to be
adequate.(22)(27)(29)(30)
303
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TABLE 12.4 SUMMARY OF BOTTOM SAMPLING EQUIPMENT
(DEVICES LISTED IN DESCENDING ORDER OF RECOMMENDATION) (28)
Advantages
Disadvantages
Teflon or Glass Tube
Hand Cover with
removable Teflon or
glass liners.
Eeknan or Box-Dredge,
line or pole operated.
Gravity corers
i.e. Phleger Corer
Panar Crab Sampler
Shallow wadeable waters or deep
waters If SCUBA available. Soil
or semi-consolidated deposits
Small sample size requires
repetitive sampling*
BHH-53 Piston Corer
USBMl 60
Pccerficn Crab Sampler
Orange Peel Crab
Snith Hclntyre Grab
Scoopsi drag buckets
Same as shove except more
consolidated sediments can be
obtained. Use extended to
•waters of 4—6 feet by the use
of extension rods.
Soft to semi~soft sediments.
Can be used from boat, bridge,
or pier in waters of various
depths.
Deep lakes and "rivers.
consolidated sediments
Deep lakes, rivers, and estu-
aries. Useful on sand, silt,
or clay.
Waters of 4-6 feet deep when
used with extension rod. Soft
to semi-consolidated deposits.
moving waters from a
fixed platform.
Deep lakes, rivers, and estu-
aries. Useful on most sub-
strates
Deep lakes, rivers» and est-
uaries. Useful on most sub-
strates.
Various environmental degrad-
ing.
Preserves layering and permits
historical study of sediment
deposition. RAPID - samples
I mined lately ready for laboratory
shipment. Minimal risk of
contamination. Inexpensive.
Handles provide for greater ease Requires removal of liners before
of substrate penetration. repetitive sampling. Slight risk
of metal contamination from
barrel and core cutter.
Obtains s larger sample with
respect to coring tubas. Can
be subsampled through box-lid.
Pole operated sampler provides
greater control and minimizes
disturbance of the "fines".
Low risk of sample contamina-
tion.
Most univerasal grab sampler.
Adequate on most substrates.
Large sample obtained intact,
pe rmi 11Ing subsamp1ing.
Piston provides for greater
sample retention.
Streamlined configuration
allows sampling where other
devices could not achieve
proper orientation.
Large sample; can penetrate
Possible incomplete jaw closure
and sample loss. Possible
shock wave which may disturb
the fines. Metal construction
may introduce contaminants*
Small sample, requires repetitive
operation and removal of liners.
Time consuming.
Shock wave from descent may
disturb "fines". Possible in-
complete closure of jaws and sample
loss. Possible contamination
from metal frame construction.
Sample must be further prepiired
for analysis.
Cores must be extruded on site
to other containers - metal barrel
Introduces risk of metal contamina-
tion.
Possible contamination from metal
construction. Subsarapling diffi-
cult. Not effective'for sampling
line sediments.
Heavy* may require w/inch. Ho
cover lid to permit subsampling.
All other disadvantages of
Eckman and Ponar.
304
-------
2. Container caps should be threaded to screw onto the"container.
Caps must be lined with Teflon.(22)(23) Foil may be substituted if
sample is not corrosive.(22)
3. Purgeable sample must be collected in 40 ml borosilicate glass
vials with screw caps {Pierce #13075 or equivalent). The septa
used must be Teflon faced silicon (Pierce #12722 or equivalent).
(22)
12.5 SAMPLING PROCEDURE AND PRETREATMENT OF SAMPLE EQUIPMENT
12.5.1 Pretreatment of Equipment
The pretreatment technique should be dictated by the analysis to be
performed. The general pretreatment technique for sample and storage
containers is to:
1. Wash bottles with hot detergent water.
2. Rinse thoroughly with tap water followed by three or more rinses
with orgainic-free water.
3. Rinse with interference free redistilled solvent such as acetone or
methylene chloride and dry in contaminant free air at room
temperature. Protect from atmospheric or other sources of
contamination. Caps and liners for bottles must also be solvent
rinsed as above.
If automatic samplers are to he employed, use the peristaltic pump type
with a single 8-10 liter (2.5 - 3.0 gallons) glass container. Vacuum type
automatic samplers can be used if sample containers are glass. The pro-
cedure outlined above should be followed for the pretreatment of the
containers. In addition all tubing and other parts of the sampling system
must be scrubbed with hot detergent water and thoroughly rinsed with tap
water and blank water prior to use. Further rinsing with interference free
acetone or methylene chloride is advised when tubing and other parts permit,
i.e., are not susceptible to dissolution by the solvent.
12.5.2 Sampling Procedure
Purgeables (22)(31)(32)
Collect grab samples in glass containers. The procedure for filling
and sealing sample containers is as follows: Slowly fill each con-
tainer to overflowing. Carefully set the container on a level surface.
Place the septum Teflon side down on the convex sample meniscus. Seal
the sample with the screw cap. To insure that the sample has been
properly sealed, invert the sample and lightly tap the lid on a solid
surface. The absence of entrapped air bubbles indicates a proper seal.
If air bubbles are present, open the bottle, add additional sample, and
reseal (in same manner as stated above). The sample must remain
hermetically sealed until it is analyzed. Maintain samples at 4°C
(39 F) during transport and storage prior to analysis. If the sample is
305
-------
taken from a water tap, turn on the water and permit the system to
flush. When the temperature of the water has stabilized, adjust the
flow to about 500-mL/minute and collect samples as outlined above.
Non-Purgeables (22}(32)
Collect grab samples in glass containers. Conventional sampling
practices should be followed, except that the bottle must not be pre-
washed with sample before collection. Composite samples should be
collected in refrigerated glass containers in accordance with the
requirements of the program. Automatic sampling equipment must be free
of Tygon and other potential sources of contamination.
12.6 SAMPLE PRESERVATION AND STORAGE (32)
Analyze samples as soon as possible. Preserve and store samples
collected for analyses via EPA's 600 Method Series as described below:
i
Method 601 - Purgeable Halocarbons
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction. If the sample contains free or combined
chlorine, add sodium thoisulfate preservative (10 mg/40 ml will suffice
for up to 5 ppm CK) to the empty sample bottles just prior to shipping
to the sampling site.
All samples must be analyzed within 14 days of collection. '•
Method602 - PurgeableAromatics '
Collect about 500 ml sample in a clean container. Adjust the pH of the
sample to about 2 by adding 1:1 diluted HC1 while stirring vigorously.
If the sample contains free or combined chlorine, add sodium thiosul-
fate preservative (10 mg/40 ml will suffice for up to 5 ppm C!A} to the
empty sample bottles just prior to shipping to the sampling site.
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction.
All samples must be analyzed within 14 days of collection,
Method 603 - Acrolein and Acrylonitrlle
The samples must be iced or refrigerated at 4° from the time of
collection until extraction. If the sample contains free or combined
chlorine, add sodium thiosulfate preservative (10 mg/40 ml is
sufficient for up to 5 ppm Clp) to the empty sample bottles just prior
to shipping to the sampling site.
3D6
-------
If acrolein is to be analyzed, collect about 500 ml sample in a clean
glass conatiner. Adjust the pH of the sample to 4 to 5 using acid or
base, measuring with narrow range pH paper. Samples for acrolein
analyses receiving no pH adjustment must be analyzed within three days
of sampling.
All samples must be analyzed within 14 days of collection.
Method 604 - Phenols
The samples must be iced or refrigerated at 4° from the time of
collection until extraction. At the sampling location fill the glass
container with sample. Add 80 rug of sodium thiosulfate per liter of
sample.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 605 - Benzidines
The samples must be iced or refrigerated at 4 C from the time of
collection to extraction. Benzidine and dichlorobenzidine are easily
oxidized by materials such as free chlorine. For chlorinated wastes,
immediately add 80 mg sodium thiosulfate per liter of sample.
if 1,2-diphenylhydrazine is likely to be present, adjust the pH of the
sample to 4 ± 0.2 units to prevent rearrangement to benzidine. The
sample pH should be adjusted to 2-7 with sodium hydroxide or sulfuric
acid.
All samples must be extracted within seven days. Extracts may be held
up to seven days before analysis if stored under an inert (oxidant
free) atmosphere. The extract must be protected from light.
Method 606 - Phthalate Esters
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 607 - Nitrosamlnes
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction. If residual chlorine is present, add
80 mg of sodium thiosulfate per liter of sample. And, if
diphenylnitrosamine is to be determined, adjust the pH of the water
sample to pH 7 to 10 using sodium hydroxide or sulfuric acid. Record
the volume of acid or base added.
307
-------
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 608 - Organochlorine Pesticides and PCB's
The samples must be iced or refrigerated at 4°C from the time.of
collection until extraction. If the samples will not be extracted
within 72 hours of collection, the sample should be adjusted to a pH
range of 5.0 - 9.0 with sodium hydroxide or sulfuric acid. If aldrin
is to be determined, and if residual chlorine is present, add sodium
thiosulfate.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 609 - Nitroaromatics and Isophorone
The samples must be iced or refrigerated at 4 C from the time;of
collection until extraction. ;
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 610 - Polynuclear Aromatic Hydrocarbons
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction. PAHs are known to be light sensitive,
therefore, samples, extracts and standards should be stored in amber or
foil wrapped bottles in order to minimize photolytic decomposition.
Fill the sample bottle and, if residual chlorine is present, add 80 mg
of sodium thiosulfate per liter of sample.
All samples must be extracted within seven days, and analysis
completely analyzed within 40 days of extraction.
Method 611 - Haloethers
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction. If residual chlorine is present, add
80 mg of sodium thiosulfate per liter of water.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 612 - Chlorinated Hydrocarbons
The samples must be iced or refrigerated at 4 C from the time of
collection until extraction.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
308
-------
Method 613 - 2,3,7,8-Tetrachlorodibenzo-p-dioxin
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction. If residual chlorine is present, add
80 mg of sodium thiosulfate per liter of water. Protect the sample
from light from the time of collection until analysis.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
Method 624 - Purgeables (GC/MS)
The sample must be.iced or refrigerated at 4°C from the time of
collection until extraction. If the sample contains residual chlorine,
add sodium thiosulfate preservative (10 mg/40 ml is sufficient for up
to 5 ppm Cl?) to the empty sample bottles just prior to shipping to the
sample site, fill with sample just to overflowing, seal the bottle, and
shake vigorously for one minute.
Experimental evidence indicates that some aromatic compounds, notably
benzene, toluene, and ethylbenzene are susceptible to rapid biological
degradation under certain environmental conditions.(3) Refrigeration
alone may not be adequate to preserve these compounds in wastewaters
for more than seven days. For this reason, a separate sample should be
collected, acidified, and analyzed when these aromatics are to be
determined. Collect about 500 ml of sample in a clean container.
Adjust the pH of the sample to about 2 by adding HC1 (1+1) while
stirring. Check pH with narrow range (1.4 to 2.8) pH paper. Fill a
sample container as described in Section 9.2. If chlorine residual is
present, add sodium thiosulfate to another sample container and fill as
in Section 9.2 and mix thoroughly.
All samples must be analyzed within 14 days of collection.
Method 625 - Base/Neutrals, Acids and Pesticides (GC/MS)
The samples must be iced or refrigerated at 4°C from the time of
collection until extraction. The sample must be protected from light.
If the sample contains residual chlorine, add 80 mg of sodium
thiosulfate per liter of sample.
All samples must be extracted within seven days and completely analyzed
within 40 days of extraction.
309
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12.7 REFERENCES
1. National Interim Primary Drinking Water Regulations, EPA-570/9-76-003.
2. Federal Register, Vol. 44, No. 231, November 29, 1979, pp. 68624-68707,
3. Federal Register, Vol. 43, No. 28, Table 1, February 9, 1978, p. 5780.
4. Federal Register, Vol. 41, June 10, 1976, p. 23576.
5. Federal Register, Vol. 41, June 30, 1976, p. 27012.
6. Federal Register, Vol. 41, July 23, 1976, p. 30468.
7. Bellar, T.A. and J.J. Lichtenberg. Determining Volatile Organics at
Microgram-Per-Liter Level by Gas Chromatography. J. AWWA 66,
pp 739-744, December, 1974,"
8. Henderson, J.E., G.R. Peyton, and W.H. Glaze. Identification and
Analysis of Organic Pollutants in Water. L.H. Keith, ed., pp. 105-111,
Ann Arbor Science, Ann Arbor, Michigan, 1976.
9. Glaze, W.H., G.R. Peyton, O.D. Sparkman, and R.L. Stern. Proceedings
of American Chemical Society, Southeast Southwest Regional Meeting.
Paper #128, Memphis, Tennessee, October 29-31, 1975.
10. Duenbostel, B.F. Method of Obtaining GC/MS Data of Volatile Organics
in Water Samples. Internal Report EPA, Region II Edison, New Jersey,
May 14, 1973. ;
11. U.S. Environmental Protection Agency. Methods for Organic Water and
Wastewaters. Cincinnati, Ohio, 1971.
12. Grob, K. Organic Substances in Porable Water and in Its Precursor:
Part I Methods for Their Determination by Gas-Liquid Chromatogr.aphy.
Journal of Chromatography 84, p. 255, 1973.
13. Bertsch, W., E. Anderson, and G. Holzer. Trace Analysis of Organic
Volatiles in Water by Gas Chromatography - Mass Spectrometry with Glass
Capillary Columns. Journal of Chromatography 112, p. 701, 1975.
14. Sugar, J.W. and R.A. Conway. J. WPCF, 40 (9) 1922, September 1968.
15. American Society for Testing Materials. Annual Book of Standards. Part
23, Method D2908-70T, Philadelphia, Pennsylvania, 1973.
16. U.S. Environmental Protection Agency. Manual of Chemical Methods for
Pesticides and Devices. July, 1976.
17. APHA, AWWA, WPCF, American Public Health Association. Standard Methods
for the Examination of Water and Wastewater. 14th ed., Washington, DC,
p. 1193, 1976.
310
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18. Goerlitz, D.F. and E. Brown. Methods for Analysis of Organic
Substances in Water. In: Techniques of Water-Resources Investi-
gations. USGS, Book 5, Chapter A3, p.40, 1972.
19. Keith, L.H. Identification and Analysis of Organic Pollutants in
Water. Ann Arbor Science, Ann Arbor, Michigan, p. 718, 1977.
20. American Society for Testing and Materials. Annual Book of Standards.
Part 31, Philadelphia, Pennsylvania, 1977.
21. Budde, W.L. and J.W. Eichelberger. Development of Methods for Organic
Analyses for Routine Application in Environmental Monitoring Labora-
tories. In: Identification and Analysis of Organic Pollutants in
Water. L.H. Keith, ed. Ann Arbor Science Publishers, Ann Arbor,
Michigan, 1976.
22. Federal Register, Vol. 44, No. 233. Guidelines Establishing Test
Procedures for the Analysis of Pollutants; Proposed Regulations.
Monday, December 3, 1979.
23. U.S. Environmental Protection Agency. Methods for Organic Compounds in
Municipal and Industrial Wastewater. Environmental Monitoring and
Support Laboratory, Cincinnati, Ohio, March, 1979.
24. Garrison, A.W., J.D. Pope, A.L. Alford and C.K. Doll. An Automatic
Sampler, A Master Analytical Scheme and a Registry System for Organics
in Water. In: Proceedings of the Ninth Annual Materials Research
Symposium. National Bureau of Standards, Gaithersburg, MD. April,
1978 in press.
25. Dunlap, W.J., D.C. Shew, M.R. Scalf, R.L. Crosby and J.M. Robertson.
Isolation and Identification of Organic Contaminants in Ground Water.
In: Identification and Analysis of Organic Pollutants in Water, L.H.
Keith, ed. pp. 453-478 Ann Arbor Science Publishers, Ann Arbor,
Michigan, 1976.
26. Dunlap, W.J., J.F. McNabb, M.R. Scalf and R.L. Crosby, Sampling for
Organic Chemicals and Microorganisms in the Subsurface. U.S. EPA
600/2-77-176, 1977.
27. Kopfler, F.C., R.G. Melton, R.D. Lingg, and W.E. Coleman. GC/MS
Determination of Volatiles for the National Organics Reconnaissance
Survey (NORS) of Drinking Water. In: Identification and Analysis of
Organic Pollutants in Water. L.H. Keith, Ed. pp. 87-104 Ann Arbor
Science Publishers, Ann Arbor, Michigan, 1976.
28. Freed, J.R., D.A. Abell, and R.E. Huddleston. Sampling Protocols for
Analysis of Toxic Pollutants in Ambient Water, Bed Sediment, and Fish.
February 3, 1980, Report by Versar, Inc., Springfield, Virginia in
fulfillment of EPA Contract No. 68-01-3852.
311
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i
29. Perry, D.C., C.C. Chuang, G.A Jungclaus, and J.S. Warner. Identi-
fication of Organic Compounds in Industrial Effluent Dischargers. U.S.
EPA-56Q/6-78-QQ9, November, 1978.
30. Keith, L.H., A.W. Garrison, F.R. Allen, M.H. Carter, T.C. Flyd, J.D.
Pope, A.D. Thruston, Jr. Identification of Organic Compounds .in
Drinking Water from Thirteen U.S. Cities. In: Identification and
Analysis of Organic Pollutants in Water. L.H. Keith, ed., pp.329-374
Ann Arbor Science Publishers, Ann Arbor, Michigan, 1976.
31. U.S. Environmental Protection Agency. Methods for Benzidine,
Chlorinated Organic Compounds, Pentachlorophenol and Pesticides in
Water and Wastewater. Environmental Monitoring and Support Laboratory,
Cincinnati, Ohio, September, 1978.
32. U.S. Environmental Protection Agency. Methods for Organic Chemical
nalysis of Water and Wastes by GC, HPLC and GC/MS. Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio, 1981.
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CHAPTER 13
SAMPLING RADIOACTIVE MATERIALS
13.1 BACKGROUND
Radioactivity in the environment results from the decay processes of
individual radionuclides, which are the unstable isotopes of the various
chemical elements. Radioactive isotopes possess the same chemical
properties as the stable isotopes of a given element. The rules and
precautions to be observed for collecting, handling and preserving samples
of a specific element or compound apply likewise to its radioactive forms.
Guidance given elsewhere in this manual should be reviewed when sampling for
radioactive material.
Radioactive waste originates from such diverse nuclear facilities as
uranium and thorium mines and mills, fuel enrichment and fabrication plants,
nuclear power plants, test reactors, fuel reprocessing plants, waste burial
sites, hospitals with nuclear medicine laboratories, nuclear weapons sites,
radiochemical producers, research and test laboratories, and manufacturers
of products incorporating radioactive substances. Routine gaseous or liquid
discharges from nuclear facilities to unrestricted areas contain relatively
low concentrations of radioactive material; high level wastes are condensed,
sealed and stored on site or transported to radioactive waste disposal
sites. The types and amounts of discharged radionuclides vary widely with
facility.
The Nuclear Regulatory Commisssion (NRC) regulates the discharge of
radioactive material from nuclear facilities. Concentrations of
radionuclides permitted in releases to unrestricted areas are specified in
Section 20.106 of 10 CFR 2Q,.(1) The EPA has established permissible
concentrations of biologically significant radionuclides in drinking
water.(2) .
The pathways through which radionuclides in water reach man are shown
in Figure 13.1. (3) The drinking water pathway is usually the one that
contributes the most dose. Others of significance include consumption of
plants and animals that live in water or are fed by irrigation. Less
important generally is the external dose received during work or
recreational activity from radioactivity in nearby surface water, sediment
deposited near shorelines, or irrigated fields. (4)
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Radioactive
materials
Direct radiation
Soil
Surface or
ground
water
Radioacti ve
materials
Sand and
sediment
Irri gation
water
Aquati c
plants
Fishing
and sports
gear
Direct radiation
Aquatic
animals
Land
plants
Land
animals
Ingestion
Figure 13.1 Simplified pathways between radioactive
materials released to ground or surface
waters (including oceans) and man
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13.2 GENERAL CONSIDERATIONS
13.2.1 Background Radioactivity
Many naturally-occurring radionuclides exist in soil, water, air and
living matter. (5) In addition, man-made radionuclides have become
widespread in the natural environment during the past few decades. Due to
their presence, background radioactivity at sampling locations must be
assessed to determine the actual amount contributed by a nuclear facility to
the environment. Control samples taken upstream of the liquid discharge
point provide data on the types and amounts of background radionuclides.
In addition, natural and artificial radionuclides occur as impurities
in many materials used for sample containers, radiation detection equipment
and shields, and chemical reagents. (6) For example, glass contains natural
40
K, natural water contains uranium, thorium, and their decay products.
Cerium compounds contain thorium. Since these contaminants can produce
interferences in radionuclide analyses, their effects must be evaluated
before sampling.
13.2.2 Radioactive Decay
The half-lives of sampled radionuclides relative to the interval
between sampling and measurement must be considered for determining
analytical priority. Those with short (less than one week) half-lives need
immediate measurement.
Radionuclide concentrations are reported at levels occurring at the
time of sampling. This requires that the times of sampling and analyses be
carefully recorded for accurate decay corrections. Note, however, that many
naturally occurring radionuclides possess long half-lives which eliminates
the need for correction.
References 7, 8, and 9 list half-life values as well as radiation
emission data. Reference 9, although comparatively old, provides
comprehensive radionuclide data. Many chemistry handbooks provide data
pertaining to common radionuclides. Use recent editions since research to
obtain more accurate values continues. For this reason, the data used in a
analysis must be recorded since the advent of more accurate values may
require revision of earlier calculations.
13.2.3 Detection Capability
The ability to identify and measure very low concentrations of
radionuclides depends on the types of counting instrumentation on hand and
their sensitivity. An important element affecting detection capability is
the instrument background level that results from radioactivity ambient in
the counting facility and present in the detector shield and the detection
equipment itself. Counting equipment presently available together with
proper background control provides sufficient sensitivity to measure
radionuclides at levels below regulatory standards.
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Knowledge of detection capabilities aids in designing the sampling
program, such as, necessary sample volume.
Minimum detectable levels for radionuclides frequently observed in
water and analyzed by routine techniques are given in Table 13.1 (10) In
some cases, several detection limits are listed to show how they vary with
method. Gross alpha and beta counting are preferred by some because the
instruments are relatively inexpensive and sufficiently sensitive to
determine compliance with certain standards such as those for drinking
water. Effective use of gross measurements, however, requires knowledge of
radionuclide composition.
13.3 FREQUENCY OF SAMPLING
13.3.1 Regulatory ; ;
As specified in: l)license or regulations issued by the NRC or NRC
Agreement State; 2) EPA drinking water standards; or 3) permits from other
governmental agencies.
13.3.2 Surveillance
Base frequency of sampling on an evaluation of:
1. types, amounts and potential hazards of radionuclides discharged,
2. their behavior in the environment,
3. waste discharge practices,
4. nature of use of local environment, and
5. the distribution and habits of potentially affected populations.(5)
A minimum grab sampling program for surveillance of nuclear power
reactors (4) that may be applicable to other types of facilities follows:
1. Surface water — monthly
2. Ground water, from sources likely to be affected — quarterly.
3. Drinking water supplies — sample at the water intake with a
continuous flow proportional sampler. If impracticable, obtain a
monthly grab sample at the reservoir when its holding time exceeds
one month; if less, make sampling frequency equal to reservoir
holding time.
4. Sediment — semi-annually
13.3.3 Other
The frequency for testing effectiveness of waste treatment or control
methods is determined by objectives of investigation.
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TABLE 13.1 RADIONUCLIDE DETECTION CAPABILITIES
Physical Sample Minimal Detect-
Radionuclide Half-life Size, able Level
liters pCi/liter*
3H 12. 4y 0.008 200
14C 5730y 0.2 30
60r 5.27y 0.4 10
L0 3.5 10
89$r 50. 5d 1.0 0.5
90Sf 28. 5y 1.0 0.2
131, 8.04d 2.0 0.1
1 10.0 0.4
0.4 10
137r 30. Oy 0,4 10
us 1.0 0.3
3.5 10
226D = 1600y 1.0 0.02
K3
228D 5.75y 2.0 0.1
Ka
Ra (total) — 2.0 0.06
Gross alpha — 0.1 0.5
0.5 0.1
Gross beta — 0.1 2.0
0.5 0.5
Method
LSC
LSC
Y-spect (Ge)
Y-spect (Nal)
CS and' LBBC
CS and LBBC
CS and LBBC
IOR, Y -spect
Y-spect(Ge)
Y-spect (Ge)
CS and LBBC
Y-spect (Nal)
RE
CS and LBBC
CS and IPC
IPC
IPC
LBBC
LBBC
* Calculated at the 99.7% (three-sigma) confidence level, based on
1000-minute counting intervals and typical counting
instrument background levels.
Methods:
CS Chemical separation technique (10)
IOR Ion-exchange resin
IPC Internal proportional counter
LBBC Low background beta counter
LSC Liquid scintillation counter
RE Radon emanation and counting by alpha sci
efficiencies and
nti llation cell (10)
Y-spect Gamma-ray spectroscopy, "Nal" denotes a 10 cm x 10 cm Nal (Tl)
3
detector and "Ge" an 85 cm Ge (Li) detector
317
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13.4 LOCATION OF SAMPLING
Unless specified in regulatory licenses, requirements or permits,
selection of proper sampling locations is based on judgment (see Section
13.3.2). As a guide, the EPA recommends for surveillance of light-Water
reactor sites: (4) :
1. Surface water — At streams receiving liquid waste, collect one
sample both upstream and downstream of the discharge point. Obtain
downstream sample outside of the restricted area at a location no
closer than 10 times the stream width to allow for mixing and
dilution. At facility sites on lakes or large bodies of water,
sample near but beyond the turbulent area caused by discharge.
Record the discharge flow rate at the time of sampling.
2. Drinking water — Sample all water supplies with intakes downstream
and within 10 miles of a nuclear facility. If none exists, sample
the first water supply within 100 miles.
3. Ground water — Monitoring is necessary when a facility
discharges radioactive waste to pits or trenches. When local
ground water is used for drinking or irrigation, at a minimum,
sample the nearest affected well. Subsurface movement of most
radionuclides is retarded by the filtering and ion-exchange
capacity of soil; tritium, however, moves more rapidly than most
radionuclides. ;
4. Sediment — Samples to detect accumulation of undissolved or
adsorbed radionuclides in beds of streams or other bodies of water
receiving liquid effluents from nuclear facilities are collected:
1) downstream near the discharge outfall but beyond the turbulent
area; 2) downstream of the discharge at locations where sediment is
observed to accumulate, such as at bends of streams or dam
impoundments; and 3) upstream near the discharge outfall but beyond
its influence, to determine background radionuclides.
See also Section 8.4 of this manual for additional guidance in
selecting proper sample locations.
13.5 SAMPLE VOLUME
Determining necessary sample volume depends on the types and number of
analyses to be performed and the sensitivity of available analytical
instruments. For surveillance purposes, obtain the following minimum
volumes:
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Measurement : Volume, liters
Gamma-ray spectroscopy (Nal detector) 3.5*
Gamma-ray spectroscopy (GeLi detector) 0.4
Gross alpha or beta only 0.1
Liquid scintillation - tritium only 0.01
* Water can be subsequently used for analyses requiring chemical separations
(e.g.,89Sr»90Sr^
Sediment analyses usually require 1 kg. of sample. (5)
Increase the volumes or weights when sample splitting or replicate
analyses is required for quality control purposes.
13.6 SAMPLE CONTAINERS
Use sample containers that minimize radionuclide losses by adsorption
or other processes during collection and storage. Containers made of
fluorinated hydrocarbon material (e.g. Teflon) are preferred because of
their resistance to adsorption. Polyethylene and polyvinyl chloride are
also recommended.(11) Glass and metal containers tend to retain
radionuclides.(lZ) Glass bottles also are more subject to breakage during
handling.
When adsorption problems persist, wash containers and sampling
apparatus with HC1 or HNO~ before sampling or flush the containers and
apparatus with the liquid to be collected before final sampling.(13) Test
for adsorption by analyzing used containers by gamma-ray spectroscopy when
this type of radionuclide emission is present. For other emitters, use
successive acid Teachings with hot aqua regia and analyze the leachate.(lZ)
Discard containers after use to eliminate possibility of
cross-contamination through re-usage. If for economic reasons the more
expensive containers must be used again, test for adsorbed contamination as
described above.
13.7 SAMPLE FILTRATION
Filter water and wastewater sample to segregate liquid and solids when
the radionuclide contents are to be determined in either or both the
suspended solids and dissolved matter fractions. Filter as soon as
practicable after collection to assure that no redistribution occurs
during storage before analysis.(12) Use membrane or glass fiber filters
since these types resist adsorption effects.(11) Filter before adding
preservative or other substances to the sample since they can effect changes
in distribution.(14)
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13.8 SAMPLE PRESERVATION
Radionuclides are subject to many little understood chemical and
physical processes at the very low concentrations (parts per bil"h'on:or
less), which are typical of most environmental water samples.(11)(12)(15)
Variations in original sample concentration or homogeneity can result from:
1) adsorption on sampling apparatus, container walls or solid material in
the sample;(5) 2) co-precipitation of radionuclides due to precipitation
of Fe and Mn in ground water samples exposed to air;(15) 3) ionic exchange
with components of glass containers;(12) 4) uptake by bacteria, algae or
other biological matter in the sample;(13) and 5) formation of
colloids.(12) Many of these problems are thought to occur because the
amounts of stable isotopes are insufficient to serve as a carrier for the
radioactive nuclides of the same element.(11)
The standard preservation technique for radionuclides in water and
wastewater samples is acidification to ;a pH of < 2 with HC1 or HN03.(14)(15)
Several exceptions exist: ;
1. Tritium - add no acid; begin analysis immediately upon return to
the laboratory.(10)
2. Carbon 14 - see tritium
3. Radiocesiums - use HC1 only
4. Radioiodines - see tritium: acid oxidizes iodides to iodines which
are rapidly lost through volatilization.(12) For samples
3 14 131
containing H, C or I along with radionuclides requiring
preservatives, obtain duplicate samples and add acid to only one.
Add acid preservative after sample collection (but not before
filtration - see Section 13.7) or as soon as practicable but do not delay
beyond five days.(14) :
When acid preservation is not desirable: 1) add isotopic carriers of
the same elements as the radionuclides;(12) 2) refrigerate samples at or
near their freezing temperature to retard chemical reaction rates and to
inhibit bacterial growth.(16) '
13.9 GENERAL SAMPLING PROCEDURE - WATER AND WASTEWATER
The following procedure summarizes the elements of good practice for
collecting and preserving samples of water and wastewater for radionuclide
measurements. These guidelines apply to the situation where no unusual
circumstances exist:
1. Flush sample lines, equipment or other apparatus and sample
container with sample medium to minimize adsorption effects. Use
type of containers recommended in Section 13.6.
2. Avoid .floating debris and bottom sediments when sampling surface
waters. When aliquoting large samples containing significant
amounts of suspended solids, vigorously shake or mix to assure
320 ;
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representative subsamples.
Wash sampling apparatus with distilled water to minimize
contamination of subsequent samples.
Filter sample as soon as practicable after collection when
radionuclide distribution in soluble and/or insoluble phases is to
be determined (see Section 13.7). Use membrane or glass fiber
filters.
Add preservative of the required type to liquid samples (see
Section 13.8). When concentrated HC1 or HNCL is the indicated
type, add to obtain a pH of < 2. In cases of mixtures of
radionuclides, for some ( H, C, I ) of which acid preservation
is not recommended, collect replicate samples and treat only one
with acid.
Seal sample container tightly. Complete sample data label
including time of collection for decay corrections.
Analyze samples containing short-lived radionuclides as soon as
possible.
Discard sample containers after use or test for contamination if
expensive types of containers are to be used again.
13.10 RADIATION SAFETY
Storage of large numbers or volumes of samples containing radioactivity
is a potential source of exposure to workers occupying the area. However,
this is unlikely with environmental samples due to low radionuclide content.
if in doubt, survey the area periodically with a beta-gamma survey
instrument, such as a Geiger-Mueller (GM) meter. Note that sample
containers reduce all alpha-particle and much beta-particle radiation. If
radiation levels above instrument background occur at work stations, consult
a radiation safety specialist for procedures to reduce exposure levels
and for proper disposal techniques when samples are no longer needed.
13.11 REFERENCES
1. U.S. Nuclear Regulatory Commission. Standards for Protection Against
Radiation. Title 10, Code of Federal Regulations, Part 20, Federal
Register, U.S. Government Printing Office, Washington, D.C. 1975.
2. Office of Water Supply, U.S. Environmental Protection Agency. National
Interim Primary Drinking Water Regulation. EPA-570/9-76-003, U.S.
Government Printing Office, Washington, D.C., 1977.
3. Report by Committee 4 of the International Commission on Radiological
Protection, Principles of Environmental Monitoring related to the
Handling of Radioactive Materials. ICRP Publication 7, Pergamon Press,
Oxford, 1965.
321
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4. U.S. Environmental Protection Agency, Office of Radiation Programs.
Environmental Radioactivity Surveillance Guide. EPA report No. ORP/SID
72-2, 1972.
5. National Council on Radiation Protection and Measurements.
Environmental Radiation Measurements. NCRP Report No. 50, 1976.
6. DeVoe, J.R. Radioactive Contamination of Materials Used in Scientific
Research. National Academy of Sciences - National Research Council,
Nuclear Science Series Report No. 34, 1961.
7, Martin, M.J., editor, Nuclear Decay Data for Selected Radionuclides.
Oak Ridge National Laboratory, O'RNL-5114, March 1976.
8. Martin, M.J. and P.H. Blichert-Toft. Radioactive Atoms. Nuclear Data
/ Tables A8, Nos. 1-2, 1970.
9. Lederer, C.M., J.M. Hollander, and I. Perlman. Table of Isotopes.
John Wiley, New York, 1967.
10. Krieger, H.L. Interim Radiochemical Methodology for Drinking Water.
U.S. Environmental Protection Agency, Report No. EPA-600/4-75-008
(Revised), March 1976.
11. Mitchell, N.T. Manual on Analysis for Water Pollution Control.
Radiological Examination. World Health Organization, to be published.
12. Kahn, B. Determination of Radioactive Nuclides in Water. Water
Pollution Control Handbook, L.L. Ciaccio, ed., Marcel Dekker, Inc.,
New York, 1973. ;
13. Corley, J.P., D.H. Denham, D.E. Michels, A.R. Olsen and D.A. Waite. A
Guide for Environmental Radiological Surveillance at ERDA
Installations. U.S. Energy Research & Development Administration,
Report No. ERDA 77-24, March,1977.
14. American Public Health Association. Standard Methods for the
Examination of Water and Wastewater. 14th edition, Washington, D.C.,
1976.
15. Thatcher, L.L., V.J. Janzer and K.W. Edward. Methods for Determination
of Radioactive Substances in Water and Fluvial Sediments (Chapter A5,
Book 5, Techniques of Water-Resources Investigations of the United
States Geological Survey. U.S. Government Printing Office, Washington,
D.C. 1977.
16. U.S. Environmental Protection Agency, Environmental Monitoring and
Support Laboratory. Methods for Chemical Analysis of Water and Wastes.
EPA Report No! EPA-625/6-74-003a, 1974.
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CHAPTER 14
COLLECTING AND HANDLING MICROBIOLOGICAL SAMPLES
14.1 BACKGROUND
Fecal contamination from warm-blooded animals and man is present in
certain industrial effluents, urban and rural run-off, and in municipal
wastewaters. It can cause serious diseases and other health problems in
drinking water supplies and in recreational, agricultural, or processing
waters used in the food, dairy and beverage industries. Consequently, the
Federal Water Pollution Control Act Amendments (Clean Water Act), the Marine
Protection, Research and Sanctuaries Act (Ocean Dumping Act), and the Safe
Drinking Water Act, require monitoring of water supplies, ambient waters and
wastewater effluents for compliance with bacterial limits. (1)(2)(3)
To control pathogens discharged into these waters, selected groups of
microorganisms are monitored as indicators of the sanitary quality of a
stream or water supply. These include "total" bacteria (standard plate
count), total coliform bacteria, fecal coliform bacteria, and fecal
streptococci. The pathogens Salmonella, Shi gel la, Giardia, Pseudomonas,
Klebsiella, Clostridium spp, and viruses, are not routinely tested because
they are present in such small numbers that the methodology is cumbersome,
time-consuming and seldom quantitative.
14.2 ANALYTICAL METHODOLOGY ,
The bacterial parameters: Standard Plate Count, Total Coliform, Fecal
Coliform, Fecal Streptococci and Salmonella will be discussed.
For a more detailed description of the methodologies see Standard
Methods and the EPA microbiological manual.(4)(5) The specific analytical
methodologies required for compliance monitoring of drinking water, and
wastewater discharges are described in the regulations.
14.2.1 Standard Plate Count
The Standard Plate Count (SPC) Method is a direct quantitative
measurement of the viable aerobic and facultative anaerobic bacteria in a
water environment, that are capable of growth on the plating medium. .This
test is usually performed by suspension of the sample in agar with
subsequent growth and counting of colonies (pour plate). The counts may
also be obtained from surface growth colonies on a spread plate or on a
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membrane filter. Although no one set of plate count conditions can
enumerate all organisms present, the Standard Plate Count Method provides
the uniform technique required for comparative testing and for monitoring
water quality in selected applications.
The Standard Plate Countis a useful tool for determining the bacterial
density of potable waters for quality control studies of water treatment
processes. It provides a method for monitoring changes in the
bacteriological quality of finished water throughout a distribution system
to indicate the effectiveness of chlorine in the system as well as the
possible existence of cross-connections, sediment accumulations and other
problems within the distribution lines. The procedure may also be used to
monitor quality changes in bottled water or emergency water supplies.
14.2.2 Coliforms
The coliform or total coliform group includes all of the aerobic and
facultative anaerobic, gram negative, nonspore-forming, rod-shaped bacteria
that ferment lactose in 24 to 48 hours at 35 in a multiple tube most
probable number (MPN) procedure, or; that produce a golden green metallic
sheen within 24 hours at 35 C in the membrane filter (MF) procedure. The
definition include the genera: Escherichia, Citrobacter, Enterobacter, and
Klebslella.
The coliform group may be subdivided into the two following
categories: :
1. Coliforms normally of fecal origin (primarily Escherichia coli
types).
2. Coliforms usually associated with vegetation and soils
(Citrobacter, Enterobacter, Klebsiella, and Escherichia spp),
which may occur in fecal matter but in smaller numbers than jL
coli.
The two analytical techniques recommended by EPA and Standard Methods
for enumeration of coliforms are the Most Probable Number (MPN},'and the
Single-Step, Two-Step and Delayed Incubation Membrane Filter methods.(4}(5)
Microbiological standards for public water supplies and drinking waters
are based on total coliform numbers which include coliforms from sources
other than human and animal feces. |
14.2.3 Fecal Coliforms j
The trend in recent years is to obtain a more accurate estimate of
the sanitary quality of the ambient, and wastewater by conducting fecal
coliform analyses.
i
The fecal coliform bacteria are part of the total coliform group.
They are normally inhabitants of the gut of warm blooded animals and hence
are tolerant of higher temperatures than other coliforms. The fecal
:324
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coliform group are defined as gram negative nonspore-forming rods that
ferment lactose in 24 ± two hours at 44.5 ± 0.2 C with the production of
qas in the multiple tube procedure, or that produce acidity indicated by
blue colonies in the membrane filter procedure.
The major species in the fecal coliform group is Escherichia coli. It
is indicative of fecal pollution and of the possible presence of enteric
pathogens. No method is presently available which distinguishes human
fecal coliforms from those of other warm-blooded animals.
The analytical techniques for identifying fecal coliforms in water are
the direct MF, the delayed incubation MF, and the multiple tube, MPN
methods.
Both the MF and MPN fecal coliform tests are applicable to the
examination of lakes and reservoirs, wells and springs, public water
supplies, natural bathing waters, secondary non chlorinated effluents from
sewage treatment plants, farm ponds, storm water runoff, raw municipal
sewage, and feedlot runoff. The MF test has been used with varied success
in marine waters.
14.2.4 Fecal Streptococci
The fecal streptococci, can be used to indicate the sanitary quality
of water and wastewater. The group includes the serological groups D and
Q: Streptococcus faecal is, S.faecal is subsp. 1 iquifaciens, S.faecal is
subsp. zymogenes, S.faecium, S.bovis, S.equinus, and S.avium.
The MF, MPN and direct pour plate procedures can be used to enumerate
and identify fecal streptococci in water and wastewater.
Positive fecal streptococci results verify fecal pollution and may
provide additional information concerning the recency and probable origin
of pollution, when used as a supplement to fecal coliform analyses. They
are not known to multiply in the environment.
Speciation of streptococci in the sample may be obtained by
biochemical characterization. Such information is useful for source
investigations.
14.2.5 Salmonella
The genus, Salmonella, is comprised of a large number of serologically
related, gram negative, non-spore forming bacilli that are pathogenic for
warm blooded animals including man, and which are found in reptiles,
amphibians and mammals. They cause enteritis and enteric fevers through
contaminated water, food or food products. Because Salmonella are
responsible for many outbreaks of waterborne disease, increased efforts
have been made to identify and enumerate them.
Generally the numbers of Salmonella present in water or wastewater are
325
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very low, so that sample volumes larger than a liter are required to
isolate this pathogen. Because of the lower numbers of Salmonella in
water, negative results do not assure absence of Salmonella and analyses
for indicator organisms are usually run concurrently to measure the
potential health risk.
Recommended methods for recovery and identification of Salmonella from
water and wastewater are presented in Standard Methods and the EPA
Manual .(4)(5) The methods are particularly useful for recreational and
shellfish harvesting waters. No single method of recovery and
identification of these organisms from waters and wastewaters is
appropriate for all sampling situations. Rather the method is selected
based on the characteristics of the sample and microbiologist's experience
with the procedures. Multiple option techniques are described for sample
concentration, enrichment, isolation and identification.
14.2.6 Enteric Viruses (4)
Viruses excreted by animal and man are present in domestic sewage
after waste treatment and enter streams and lakes that serve as the source
of drinking water supplies for many communities. Viruses are excreted in
much lower numbers than coliform bacteria, and do not multiply outside of
the animal or human host. Dilution in ambient waters, sewage treatment,
and water treatment further reduces viral numbers in the environment.
However, it has been demonstrated that infection can be produced by a few
viral units. ,
Sample concentration is needed to demonstrate and quantitate viruses
in clean or potable waters because the numbers are very low. For clean
waters, 400 liters or more of water must be sampled. The most promising
method for concentrating small quantities of viruses from those waters is
adsorption onto a microporous filter. Viruses are removed from the filter
with a protein eluant or glycine buffer at a controlled pH. Viruses may be
concentrated a second time.
Measuring viruses in wastewaters and natural waters is even more
difficult because of the suspended solids present. For such samples, the
aqueous polymer two-phase separation technique may be used directly for
virus recovery but the sample size is limited to two-four liters.
After concentration of viruses and elution, the eluate is analyzed by
cell culture or whole animal assay. '
At this time, the routine examination of the waters and wastewaters
for enteric viruses is not recommended. However, for special needs such as
wastewater reuse, disease control, or special studies, virus testing can be
done but only by qualified virologists with proper facilities.
14.3 SAMPLE BOTTLE PREPARATION (4)(5)
Sample bottles must be resistant to sterilizing conditions and the
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solvent action of the water. Wide-mouth glass or heat-resistant plastic
bottles with screw-cap or ground-glass stoppers may be used if they can be
sterilized without producing toxic materials. See Figure 14.1. Screw-
capped bottles must be equipped with neoprene rubber liners or other
materials that do not produce bacteriostatic or nutritive compounds upon
sterilization.
14.3.1 Selection and Cleansing of Bottles
Select bottles of sufficient capacity to provide a volume necessary
for all analyses anticipated. Use at least a 125 ml bottle for a minimum
sample volume of 100 ml and to provide adequate mixing space. Discard
bottles which have chips, cracks, and etched surfaces. Bottle closures
must produce a water-tight seal. Before use, thoroughly clean bottles and
closures with detergent and hot water and rinse with hot water to remove
all traces of detergent. Then rinse three times with a good quality
laboratory reagent water. A test for bacteriostatic or inhibitory residues
on glassware is described in Standard Methods and in EPA's Manual. (4)(5)
14.3.2 Use of Dechlorlnating and Chelating Agents
Use a dechlorinating agent in the sample bottle when water and
wastewater samples containing residual chlorine are anticipated. Add
0.1 ml of a 10 percent solution of sodium thiosulfate to each 125 mL(4
oz.) sample bottle prior to sterilization.
Use a chelating agent when waters are suspected of containing more
than 0.01 mg/L concentration of heavy metals such as copper, nickel, zinc,
etc. Add 0.3 ml of a 15 percent solution ethylenediamine tetraacetic acid,
tetra-sodium salt (EDTA), to each 125 ml (4 oz.) sample bottle prior to
sterilization. (6)(7)
14.3.3 Wrapping of Bottles
Protect the tops and necks of glass-stopper bottles from contamination
by covering them with aluminum foil or kraft paper before sterilization.
Screw cap closures do not require a cover.
14.3.4 Sterilization of Bottles
Autoclave glass or heat resistant polypropylene plastic bottles at
121 C for 15 minutes. Glassware may be sterilized in a hot air oven at
170 C for two hours. Ethylene oxide gas sterilization is acceptable for
plastic containers which are not heat resistant. Before use of sample
bottles sterilized by gas, store overnight to allow the last traces of gas
to dissipate.
14.4 SAMPLING METHODS AND EQUIPMENT (5)
These methods are applicable for sampling potable water, streams and'
rivers, recreational waters such as bathing beaches and swimming pools,
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Screw-cap Glass or
Plastic Bottle
Plastic Bag (Whirl -pak)
Glass Stoppered
Bottle
Figure 14.1 Suggested Sample Containers
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lakes and reservoirs, public water supplies, marine and estuarlne waters,
shellfish harvesting waters, and domestic and industrial waste discharges.
In no case should composite samples be collected for microbiological
examination.Data from individual samples show a range of values which
composite samples will not display. Individual results give information
about industrial process variations. Also, one or more portions that make
up a composite sample may contain toxic or nutritive material and cause
erroneous results.
Do not rinse bottle with sample, but fill it directly to within
2.5 - 5 cm (1 - 2 in.) from the top to allow mixing of the sample before
analysis. Use caution to avoid contaminating the sample with fingers,
gloves or other materials. Test any chlorinated sample for absence of
chlorine, to assure that the naturalizing agent (14.3.2) was effective.
Completely identify the sampling site on a field log sheet, label, and
on a chain of custody tag, if this is required. See Chapter 15.
14.4.1 Tap Sampling
Do not collect samples from spigots that leak or that contain aeration
devices or screens. In sampling direct connections to a water main, flush
the spigot for 3 to 5 minutes at moderate flow to clear the service line.
For wells equipped with hand or mechanical pumps, run the water to waste
for 3 to 5 minutes at a moderate flow before the sample is collected.
Remove the cap aseptically from the sample bottle. Hold the sample bottle
upright near the base while it is being filled. Avoid splashing. Replace
bottle closure and hood covering.
14.4.2Surface Sampling By Hand
Collect a grab sample directly into a sample bottle prepared as
described in Section 14.3. Remove the bottle top cover and closure and
protect them from contamination. Avoid touching the inside of the closure.
Grasp the bottle securely at the base with one hand and plunge it mouth
down into the water, avoiding surface scum. Position the bottle towards
the current flow and away from the hand of the collector, the shore, the
side of sampling platform, or boat. See Figure 14.2. The sampling depth
should be 15 to 30 cm (6 to 12 in.) below the water surface. If the water
body is static, an artificial current can be created by moving the bottle
horizontally in the direction it is pointed and away from the sampler. Tip
the bottle slightly upwards to allow air to exit and the bottle to fill.
After removal'of the bottle from the stream, tightly stopper and label the
bottle.
14.4.3 Surface And Well Sampling By Weighted Bottle Frame
When sampling from a bridge or other structure above a body of water,
place the bottle in a weighted frame that holds the bottle securely. See
Figure 14.3. Remove the cover and lower the device to the water. It is
preferable to use nylon rope which does not absorb water and will not rot.
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Figure 14.2 Demonstration of Technique Used in Grab Sampling of
Waters and Mastewaters
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Figure 14.3 Weighted Bottle Frame and Sample Bottle for Grab Sampling
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Swing the sampling device downstream, and then allow it to drop into
the water, while pulling on the rope so as to direct the bottle upstream.
Pull the sample device rapidly upstream and out of the water, simulating
the scooping motion of grab sampling. .Take care not to dislodge dirt or
other material from the sampling platform.
Use a weighted sterilized sample bottle when sampling a well that does
not have pumping machinery. Avoid contaminating the sample with surface
scum or dislodged material from the sides of the well.
14.4.4 Depth Sampling '
i
Several additional devices are needed for collection of depth samples
from lakes, reservoirs, estuaries and the oceans. These depth samplers
require lowering the sample device and/or container to the desired depth,
then opening, filling, and closing the container and returning the device
to the surface. Although depth measurements are best made with a
pre-marked steel cable, the sample depths can be determined by
pre-measuring and marking a nylon rope at intervals with non smearing ink,
paint, or fingernail polish. The following list of depth samplers is not
inclusive but can serve as a guide: The ZoBell J-Z, the Niskin, the New
York Dept. of Health, and the Kemmerer samplers. See Figures 14.4, 14.5,
14.6 and 14.7.
14.4.5 Sediments And Sludge Sampling ;
Microorganisms attach to particles and artifacts in water and are
found in large numbers in the bottom sediment and at interfaces in any body
of water. Sewage solids in treated domestic wastewaters and sludges
contain very large numbers of microorganisms which pass into receiving
streams, lakes and oceans and then settle into the bottom sediments. This
is a particular concern in the ocean dumping program because of the
concentrated disposal of very large amounts of sludge in selected ocean
dump sites. Microorganisms in these materials are periodiclly released
into the overlying waters as the bottoms are disturbed.
Sediments and bottom materials are difficult to sample because of the
variable composition, size, density and shape of particles and the lack of
homogeneity. They vary from light, fluffy particles to compacted high
density, solid layers.
Grab samples are not usually satisfactory for quantitative bottom
sampling because they may contain material which is not representative.
However, they give an indication of the processes that occur.
Corers are used in quantitative work though none is entirely >
satisfactory. The Ekman corer is used when sampling from small boats. The
Wildlife Co. (Saginaw, Michigan) coring device is used in shallow water (15
meters or less). In extremely shallow.water a lucite tube can be inserted
into the sediment by hand, and capped by a stopper. The Van
Donsel-Geldreich sampler can be used to collect soft sediments or muds in
relatively deep waters. It uses a sterile plastic bag in a weighted frame
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D
B
A
E
Figure 14,4 Zobell J-l Sampler. (A) metal frame, (B) messenger,
(C) glass tube, (D) rubber tube and
(E) sterile sample bottle
333
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B
Figure 14.5 Niskin Depth Sampler. (A) hinged plates, (B) plastic bag,
(C) plastic filler tube in sheath, (D) guillotine knife
and (E) closure clamp.
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D
A
B1
Figure 14.6 New York State Dept, of Health Depth Sampler. (A) vane.CB1) lever
in closed position,(B2) lever in open position,(cl) glass stop-
per in closed position,(C2) glass stopper in open position,(D)
suspension line, and (E) metal frame.
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42cm
Figure 14.7 Kemmerer Depth Sampler. (A)nylon line, (B)messenger, (C)catch
set so that the sampler is open, (D)top rubber valve, (E)con-
necting rod between the valves, (F)tube body, (G)bottom rubber
valve, (H)knot at the bottom of the suspension line and, (I)
rubber tubing attached to the spring loaded check valve.
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to collect the sample and then closes the bag with a wire loop. See Figure
14.8.
14.5 SAMPLE FREQUENCY AND SITE SELECTION (5)
14.5.1 Frequency of Sampling
The frequency of sampling depends upon the type of pollution that is
to be measured. Cyclic pollution and its duration are measured as
frequently as practical immediately downstream from the source. Uniform
pollution loads are measured at greater distances downstream from the
source and at less frequent time intervals than cyclic pollution. A common
approach for short term studies is to collect samples from each site daily
and advance the sampling intervals one hour during each 24 hour period to
obtain data for a 7 to 10 day study.
Often the numbers of samples to be collected are specified by NPDES
permits, drinking water regulations, or by State requirements. Some
standards require a minimum number of samples to be collected each month.
Other standards are less explicit and simply indicate that the geometric
mean coliform density shall not exceed a certain level each month, with no
more than 10%, 20%, etc. of samples exceeding a certain value. Where the
number of samples required is undetermined, a sufficient number should be
collected to measure the variations in conditions.
14.5.2 Raw Water Supplies
Reservoirs and lakes used as water supplies are sampled at inlets,
other possible sources of pollution, the draw off point, the quarter point
intervals around the draw off point at about the same depth, and the
reservoir outlet.
14.5.3 Potable Water Supplies
Coliform standards for potable water supplies established by Public
Health Service Act of 1962 were amended by The Safe Drinking Water Act of
1974 (SDWA) and its supporting regulations.(3)(8) The levels for the 1962
PHS Standards were retained in the SDWA but were redefined as Maximum
Contaminant Levels (MCLs). As with the previous standards, the MCLs
emphasize the importance of collecting samples at regular intervals, in
numbers proportionate to the population served, and at points
representative of conditions in the distribution system. A set protocol
was established for repeat sampling when positive coliform results occur.
For application of the MCLs, the frequency of sampling and the location of
sampling points is established jointly by the utility, the Reporting
Agency, and the Certifying Authority.
The SDWA also specifies that any laboratory generating data for public
water supplies, as required under the Act, must be certified according to
the procedures and criteria in the Laboratory Certification Manual.(9) The
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Figure 14.8
VanDonsel-Geldreich Sediment Sampler. (A)sterile "Whirl-Pak
plastic bag, (B)nose piece, (C)weight, (D)mud plate, (E)slide
bar, (F)part of the double noose, (G)attachment for the
suspension line and (H)bag clamp bar.
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laboratory facility, personnel, equipment and instrumentation, sampling
methodology, quality control, data reporting and necessary action responses
are specified.
14.5.4 Distribution Systems
Sample locations should be representative of the distribution system
and include sites such as municipal buildings, public schools, airports and
parks, hydrants, restaurants, theaters, gas stations, industrial plants and
private residences. A systematic coverage of such points in the
distribution system should detect contamination from breaks in water lines,
loss of pressure, or cross connections. The sampling program should also
include special sampling locations such as dead-end distribution lines that
are sources of bacterial contamination, and far reaches of the distribution
lines where chlorine residual may have dissipated.
The minimum number of samples which must be collected and examined
each month is based upon the population density served by the distribution
system. Samples should be collected at evenly spaced time intervals
throughout the month. In the event of an1 unsatisfactory sample, repetitive
samples must be collected until tw.o consecutive samples yield satisfactory
quality water. Check samples from any single point or special purpose
samples must not be counted in the overall total of monthly samples
required for compliance with MCL's.
The standards for microbiological quality are based upon the number of
organisms allowable in a standard sample. A standard sample for the
membrane filter technique is at least 100 ml. For the MPN test, a standard
sample consists of five standard portions of either 10 ml or 100 ml.
14.5.5 Lakes and Impoundments
Sampling points in a recreational impoundment or lake should include
inlets, sources of pollution, grids or transects across the long axis of
the water body, bathing areas and outlets.
14.5.6 Stream Sampling
The objectives of the initial survey dictate the location, frequency
and number of samples to be collected.
1. Selection of Sampling Sites: A typical stream sampling program
includes sampling locations upstream of the area of concern,
upstream and downstream of waste discharges, upstream and
downstream from a tributary. Downstream sites should be located
far enough below entry of discharge or tributary to allow thorough
mixing. For more complex situations, where several waste
discharges are involved, sampling includes sites upstream and
downstream from the combined discharge area and samples taken
directly from each industrial or municipal waste discharge. Using
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available bacteriological, chemical and discharge rate data, the
contribution of each pollution source can be determined.
2, Small Streams: Small streams should be sampled at background
stations upstream of the pollution sources and at stations
downstream from pollution sources. Additional sampling sites
should be located downstream to delineate the zones of pollution.
Avoid sampling areas where stagnation may occur (backwater pf a
tributary) and areas located near the inside bank of a curve in the
stream which may not be representative of the main channel. -
3. Large Streams andRivers: Large streams are usually not well
mixed laterally for long distances downstream from the pollution
sources. Sampling sites below point source pollution should be
established to provide desired downstream travel time and dispersal
as determined by flow rate measurements. Particular care must be
taken to establish the proper sampling points at: the upper reach
control station, non-point sources of pollution, waste discharges
as they enter the stream, quarter-point samples below the pollution
sources to detect channeling, tributaries, and downstream from
tributaries after mixing. Occasionally, depth samples are
necessary to determine vertical mixing patterns,
14.5.7 Recreational Waters
1. Selection of Sampling Sites: Select sampling sites which reflect
the quality of water throughout the recreational area. Boat
marinas, waste drainage from dry well restrooms and other public
buildings, upstream flows from impounded rivers or drainages
into lakes, reservoirs or impounded streams, as well as the lake
or body of water itself should be sampled.
Sampling sites at bathing beaches or other recreational areas
should include upstream or peripheral areas and locations adjacent
to natural drains that would discharge storm water, or run off
areas draining septic wastes from restaurants, marinas, or garbage
collection areas.
Swimming pool water should be monitored at least daily during
maximum use periods, preferably at the overflow.
2» Depths: Sampling in bathing areas should be standardized at 1 foot
for shallow depths and at 3 feet for swimming depths.
3. Frequency and Time Collect samples daily during high use seasons.
Select high use days (Fridays, weekends and holidays) and sample
during peak period of the day, generally in the afternoons. Sample
estuarine waters at high tide, low tide and ebb tide to obtain a
measure of the cyclic changes in water quality.
14.5.8 DomesticandIndustrial Waste Discharges
When it is often necessary to sample secondary and tertiary wastes from
municipal waste treatment plants and various industrial waste treatment
operations, sampling must be adjusted to meet the specific situation.
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If plant treatment efficiency varies considerably, collect grab samples
around the clock at selected intervals for a three to five day period. If
it is known that the process displays little variation, fewer samples are
needed. The NPDES has established treatment plant effluent limits for
wastewater dischargers. These are often based on maximum and mean values.
A sufficient number of samples must be collected to satisfy the permit
and/or provide statistically sound data and give a fair representation of
the bacteriological quality of the discharge.(10)
14.5.9 Marine and Estuarine Sampling
Sampling marine and estuarine waters requires the consideration of
other factors in addition to those usually recognized in fresh water
sampling. They include tidal cycles, current patterns, bottom currents and
counter-currents, stratification, climatic conditions, seasonal
fluctuations, dispersion of discharges and multi-depth sampling
The frequency of sampling varies with the objectives. When a sampling
program is started, it may be necessary to sample every hour around the
clock to establish pollutional loads and dispersion patterns. The sewage
discharges may occur continuously or intermittently.
When the sampling strategy for a survey is planned, data may be
available from previous hydrological studies done by Coast Guard, Corps of
Engineers, National Oceanic and Atmospheric Administration (NOAA), U.S.
Geological Survey, or university and private research investigations. In a
survey, float studies and dye studies are often used to determine surface
and undercurrents. Initially depth samples are taken on the bottom and at
five feet increments between surface and bottom. A random grid pattern for
selecting sampling sites is established statistically.
1. Marine Sampling: In ocean studies, the environmental conditions
are most diverse along the coast where shore, atmosphere and the
surf are strong influences. The shallow coastal waters are
particularly susceptible to daily fluctuations in temperature and
seasonal changes. Sampling during the entire tidal cycle or during
a half cycle may be required. Many ocean studies such as sampling
over the continental shelf involve huge areas where no two areas
are the same.
Selection of sampling sites and depths are most critical in marine
waters. In winter, cooling of coastal waters can result in water
layers which approach 0 C. In summer, the shallow waters warm much
faster than the deeper waters. Despite the higher temperature,
oxygen concentrations are higher in shallow than in deeper waters
due to greater water movement, surf action and photosynthetic
activity from macrophytes and the plankton.
Moving from the shallow waters to the Intermediate depths, one
observes a moderation of these shallow water characteristics. In
the deeper waters, there is a marked stabilization of conditions.
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Water temperatures are lower and more stable. Deep waters have
limited turbulence little penetration of light, sparse vegetation,
and layer of silt and sediment covering the ocean floor.
Estua rine Sampling: When a survey is made on an estuary, samples
are often taken from a boat, usually making an end to end traverse
of the estuary. Another method involves taking samples throughout
a tidal cycle, every hour or two hours from a bridge, or from a
boat anchored at a number of fixed points.
In a large bay or estuary where many square miles of area are
involved, a grid or series of 'stations may be necessary. Two
sets of samples are usually taken from an area on a given day, one
at ebb or flood slack water, and the other three hours earlier, or
later, at the half tide interval. Sampling is scheduled so that
the mid-sampling time of each run coincides with the calculated
occurrence of the tidal condition.
In locating sampling sites, one must consider points at which
tributary waters enter the mafn stream or estuary, location of
shellfish beds, and bathing beaches. The sampling stations can be
adjusted as data accumulate. For example, if a series of stations
one-half mile apart consistently, show similar values, some stations
may be dropped and others added in areas where data shows more
variability.
Considerable stratification can occur in estuaries because of the
differing densities of salt water and fresh water. It is essential
when starting a survey of an unknown estuary to find out whether
there is any marked stratification. This can be done by chloride
determinations at different locations and depths. It is possible
for stratification to occur in one part of an estuary and not in
another.
On a flood tide, the more dense salt water pushes up into the less
dense fresh river water causing an overlapping, with the fresh
water flowing on top and forming the phenomenon called a salt water
wedge. As a result, stratification occurs. If the discharge of
pollution is in the salt water layer, the contamination will be
concentrated near the bottom at the flood tide. The flow or
velocity of the fresh water will influence the degree of
stratification which occurs. If one is sampling only at the
surface, it is possible that" the data will not show the polluted
underflowing water which was contaminated at a point below the
fresh water river. Therefore, where stratification is suspected,
samples at different depths will be needed to measure vertical
distribution.
Shellfi sh-Harvesting Waters; Water overlying shellfish-harvesting
areas should be sampled during periods of most unfavorable hydro-
graphic conditions, usually at low tide after heavy precipitation.
However, shellfish beds are sometimes exposed during low tide and
must be sampled during other tidal conditions. Procedures for
sampling of shellfish and water in shellfish growing areas are
governed by the National Shellfish Sanitation Program's Manual of
Operations. (11)
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14.6 PRESERVATION AND TRANSIT OF SAMPLES (4)(5)
The adherence to sample preservation and holding time limits is
critical to the production of valid data. Samples exceeding the limits
should not be analyzed. Observe the following rules:
14.6.1 Storage Temperature and Handling Conditions
Bacteriological samples should be iced or refrigerated at a temperature
of 1 to 4 C during transit to the laboratory. Insulated containers are
preferable to assure proper maintenance of storage temperature. Care should
be taken that sample bottle tops are not immersed in water during transit or
storage.
14.6.2 Ho1din g T1me Limitatio n s
Although samples should be examined as soon as possible after
collection, they should not be held longer than six hours between collection
and initiation of analyses.(12) This limit is applied to fresh waters,
seawaters and shellfish-bed waters. The exception is water supply samples
mailed in from water treatment systems. Current, drinking water regulations
permit these samples to be held up to 30 hours.
Although a holding time of six hours is permitted sewage samples,
organically rich wastes and marine waters are particularly susceptible to
rapid increases or die-away and should be held for the shortest time
possible, to minimize change.
If the specified holding time limits cannot be observed, the following
alternatives should be considered:
1. Temporary Field Laboratories: In situations where it is impossible
to meet the 6 hour maximum holding time between collection and
processing of samples, consider the use of temporary field
laboratories located near* the collection site.
2. Delayed Incubation Procedure: If sampling and transit conditions
require more than 6 hours, and the use of field laboratories is
impossible, consider the delayed incubation procedures for total
and fecal coliforms and fecal streptococci.
3. Public Transportation: Occasionally, commercial forms of transit
such as airlines, buslines or couriers are used to transport
samples contained in ice chests to the laboratory. These should be
considered only when storage time, temperature requirements and the
proper disposition of the samples can be assured.
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14.7 REFERENCES
1. Federal Water Pollution Control Act Amendments of 1972. Public Law
92-500. October 18 1972. 86 Stat. 8 16. 33 United States Code
(USC). Sec. 1151.
2. Marine Protection Research and Sanctuaries Act of 1972. Public Law
92-532. October 23 1972. 86 Stat. 1052.
3. Safe Drinking Water Act. Public Law 93-523. December 16 1974. 88
Stat. 1660. 42 United States Code (USC) 300f.
4. Standard Methods for the Examination of Water and Wastewater. 15th
Edition. Washington D.C. 1980 1134 pp.
5. Bordner, R.H., J.A. Winter and P.V. Scarpino. editors.
Microbiological Methods for Monitoring the Environment. U.S. EPA
Environmental Monitoring and Support Laboratory, Cincinnati. EPA
600/8-78-017. December 1978.
6. Shipe, E.L. and A. Fields. Comparison of the molecular filter
techniques with agar plate counts for the enumeration of E. Coli
in various aqueous concentrations of zinc and copper sulfate.
Appl. Microbiol. 2_: 382 1954.
7. Shipe, E.L. and A. Fields. Chelation as a method for maintaining
the coliform index in water supplies. Public Health Reports.
71.: 974 1956.
8. 40 CRF 141. National Interim Primary Drinking Water Regulations.
December 24, 1975. pp. 59566-59585.
9. U.S. Environmental Protection Agency. Manual for the Interim
Certification of Laboratories Involved in Analyzing Public Drinking
Water Supplies, Criteria and Procedures. Envrionmental Monitoring
and Support Laboratory, Cincinnati. EPA 600/8-78-008. May, 1978.
10. 40 CFR 136. Guidelines Establishing Test Procedures for Analysis
of Pollutants. October 16, 1973. pp. 28758-28760. December 1,
1976. pp. 52780-52786, and further amendments.
11. Hauser, L.S. editor, 1965. National Shellfish Sanitation Program.
Manual of Operations. Part 1:: Sanitation of shellfish growing
areas. U.S. Public Health Service Washington D.C.
12. Public Health Laboratory Service Water Subcommitte. 1953. The
effect of storage on the coliform and Bacterium coli counts of
water samples. Storage for six hours at room and refrigerator
temperatures. J. Hyg. 51:559.
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CHAPTER 15
SAMPLE CONTROL PROCEDURES AND CHAIN OF CUSTODY
The successful implementation of a monitoring program depends on the
capability to produce valid data and to demonstrate such validity.(1) In
addition to proper sample collection, preservation, storage and handling
appropriate sample identification procedures and chain of custody are
necessary to help insure the validity of the data. The procedures specified
herein are those used by the Office of Enforcement, U.S. Environmental
Protection Agency as of October, 1980. However, changes may occur and the
reader is advised to keep abreast of official uniform procedures.(2)
A sample is physical evidence collected from a facility or from the
environment. An essential part of all enforcement investigations is that
evidence gathered be controlled. To accomplish this, the following sample
identification and chain-of-custody procedures are recommended.
15.1 SAMPLE IDENTIFICATION
The method of identification of a sample depends on the type of
measurement or analyses performed. When in~situ measurements are made, the
data are recorded directly in logbooks or Field Data Records, Figure 15.1,
with identifying information (project code, station numbers, station
location, date, time, samplers), field observations, and remarks. Examples
of in-situ measurements are pH, temperature, conductivity, and flow
measurement.
Samples other than in-situ measurements, are identified by a sample
tag, Figure 15.2, or other appropriate identification (hereinafter referred
to as a sample tag).
These samples are transported from the sample location to a laboratory
or other location for analysis. Before removal, however, a sample is often
separated into portions, depending upon the analyses to be performed. Each
portion is preserved in accordance with applicable procedures and the sample
container is identified by a sample tag. Sample tags shall be completed for
each sample, using waterproof ink, unless prohibited by weather conditions.
For example, a logbook notation would explain that a pencil was used to fill
out the sample tag because a ballpoint pen would not function in freezing
weather. The information recorded on the sample tag includes:
Project Code - A number assigned by S & A
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riCkLS M?\ 1 f\ T\K.\s\jr\LJ
STATION
SAMPLE
NUMBER
DATE OF
COLLECTION
TIME IHBSJ
SAMPLE
TAKEN
SAMPLE
RECEIVED
(H
TEMPERATURE
OTHER PARAMETERS
Figure 15.1 Sample-Field Data Record
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ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT
NATIONAL ENFORCEMENT INVESTIGATIONS CENTER
BUILDING 53, BOX 25227, DENVER FEDERAL CENTER
DENVER, COLORADO 80225
45-EPA
Project Code
Station No.
Mo./Day/Yr.
Station Location
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347
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Station Number - A number assigned by the Project Coordinator
and listed in the project plan or the NPDES
permit number if used for NPDES inspections.
Date - A six-digit number indicating the year, month
and day of collection.
Time - A four-digit number indicating the military time
of collection - for example 0954.
Station Location - The sampling station description as specified in
the project plan.
Samplers - Each sampler is identified.
Tag Number - A unique serial number is stamped on each tag
that identifies Region with consecutive number
- for example 8-1239.
Remarks - The samplers record pertinent observations.
The tag used for water samples (also soil, sediment and biotic samples)
contains an appropriate place for designating the sample as a grab or a
composite, and identifying the type of s'ample collected for analyses and
preservative, if any. The Project Coordinator will detail procedures for
completing tags used for soil, water, sediment, and biotic samples. The
sample tags are attached to or folded around each sample.
After collection, separation, identification, and preservation, the
sample is maintained under chain-of-custody procedures discussed below. If
the composite or grab sample is to be split, it is aliquoted into similar
sample containers. Identical sample tags are completed and attached to each
split and marked "Split." The tag identifies the split sample for the
appropriate government agency, facility, laboratory, or company. In a
similar fashion, all tags on blank or duplicate samples will be marked
"Blank" or "Duplicate" respectively.
15.2 CHAIN-OF-CUSTODY PROCEDURES
Due to the evidentiary nature of samples collected during enforcement
investigations, possession must be traceable from the time the samples are
collected until they are introduced as evidence in legal proceedings. To
maintain and document sample possession, chain-of-custody procedures are
fol1 owed.
15.2.1 Sample Custody
A sample is under custody if:
1. It is in your possession, or
2. It is in your view, after being in your possession, or
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3. It was in your possession and then you locked it up to prevent
tampering, or
4. It is in a designated secure area
15.2.2 Field CustodyProcedures
1. In collecting samples for evidence, collect only that number which
provides a good representation of the media being sampled. To the
extent possible, the quantity and types of samples and sample
locations are determined prior to the actual field work. As few
people as possible should handle samples.
2, The field sampler is personally responsible for the care and
custody of the samples collected until they are transferred or
dispatched properly.
3. The Project Coordinator determines whether proper custody
procedures were followed during the field work and decides if
additional samples are required.
15.2.3 Transfer of Custody and Shipment
1. Samples are accompanied by a Chain-of-Custody Record, Figure 15.3.
When transferring the possession of samples, the individuals
relinquishing and receiving will sign, date, and note the time on
the record. This record documents sample custody transfer from the
sampler, often through another person, to the analyst in a mobile
laboratory, or at the laboratory.
2. Samples will be packaged properly for shipment and dispatched to
the appropriate laboratory for analysis, with a separate custody
record accompanying each shipment (for example, one for each field
laboratory, one for samples driven to the laboratory). Shipping
containers will be padlocked or sealed for shipment to the
laboratory. The method of shipment, courier name(_s) and other
pertinent information are entered in the "Remarks" box.
3. Whenever samples are split with a source or government agency, it
is noted in the "Remarks" section. The note indicates with whom
the samples are being split and is signed by both the sampler and
recipient. If either party refuses a split sample, this will be
noted and signed by both parties. The person relinquishing the
samples to the facility or agency should request the signature of a
representative of the appropriate party, acknowledging receipt of
the samples. If a representative is unavailable or refuses to
sign, this is noted in the "Remarks" space. When appropriate, as
in the case where the representative is unavailable, the custody
record should contain a statement that the samples were delivered
to the designated location at the designated time.
4. All shipments will be accompanied by the Chain-of-Custody Record
identifying its contents. The original record will accompany the
shipment, and a copy will be retained by the Project Coordinator.
5. If sent by mail, the package will be registered with return receipt
requested. If sent by common carrier, a Government Bill of Lading
will be used. Air freight shipments are sent collect. Freight
bills, Post Office receipts, and Bills of Lading will be retained
349
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to
CJI
o
Piroj. No.
Project Name
Samplers: (Signature)
Sta. No.
Date
Time
i
o
o
Relinquished by:
(Signature)
Relinquished by:
(Signature)
Relinquished by:
(Signature)
,0
s
C5
Date
Date
Date
Station Location
/Time
/Time
./Time
No.
of
con-
tainers
/ III Remarks
Received by:
(Signature)
Received by:
(Signature)
Relinquished by: Date/Time Received by;
(Signature) (Signature)
Relinquished
(Signature)
Received for Laboratory by:
(Signature)
Date
by: Date/Time Received by
(Signature)
/Time Remarks
Figure 15.3 Chain of Custody Record
-------
NPDES COMPLIANCE INSPECTION REPORT (Coding Instructions on back oi last page)
TRANSACTION
CODE
MO DA
INSPEC- FAC
TYPE TOn TYPE
u
I I I II I 1 I I I I I I I U U U
REMARKS
ADDITIONAL
SECTION A • Permit Summary
NAME AND ADDRESS of FACILITY (fncluds County, Slate and ZIP code)
EXPIRATION DATE
ISSUANCE DATE
RESPONSIBLE OFFICIAL
TITLE
FACILITY REPRESENTATIVE
TITLE
SECTION B - Effluent Characteristici (Additional sheets a
'ARAMETER/
OUTFALL
MAXIMUM
ADDITIONAL
SAMPLE
MEASUREMENT
PERMIT
REQUIREMENT
SAMPLE
MEASUREMENT
PERMIT
REQUIREMENT
SAMPLE
MEASUREMENT
PERMIT
REQUIREMENT
SAMPLE
MEASUREMENT
PERMIT
REQUIREMENT
SAMPLE
MEASUREMENT
PERMIT
REQUIREMENT
SECTION C • Facility Evaluation (S = Satisfactory. U * Unsatisfactory, ff/A = iVot applicable]
EFFLUENT WITHIN P6RMIT REQUIREMENTS
OPERATION AND MAINTENANCE
SAMPLING PROCEDURES
RECORDS AND REPORTS
COMPLIANCE SCHEDULE
LABORATORY PRACTICES
PERMIT VERIFICATION
FLOW MEASUREMENTS
SECTION O - Comm*ntt
SECTION E • Injptctlon/R»vi«w
SIGNATURES
ENFORCEMENT
CHVISICM
INSPECTED 8Y
INSPECTED BY
COMPLIANCE STATUS
D COMPLIANCE
QNONCOIWUANCE
REVIEWED BY
Figure 15.4 NPDES Compliance Inspection Report
351
1
-------
Sections F thru L: Complete on all inspections, as appropriate, N/A = Not Applicable
SECTION F - Facility and Parmlt Background
PERMIT NO.
ADDRESS OF PERMITTEE IP DIFFERENT FROM FACILITY DATE OF LAST PREVIOUS INVESTIGATION BY EPA/STATE
(Including City, County and ZIP code}
FINDINGS
SECTION G - Rtcordt and Rtport*
RECORDS AND REPORTS MAINTAINED AS REQUIRED 8Y PERMIT, D YES DNO DN/A (Further explanation attached )
DETAILS;
(a) ADEQUATE RECORDS MAINTAINED OF:
in SAMPLING DATi,TIM6, EXACT LOCATION
(II! ANALYSES DATES, TIMES ;
(HI) INDIVIDUAL PERFORMING ANALYSIS
(Iv! ANALYTICAL METHODS/TECHNIQUES USED
!v) ANALYTICAL RESULTS (t,g., consistent with tetf-monttoring report data)
tW MONITORING RECORDS (e,g.,flow, pH, D.O., etc.) MAINTAINED FOR A MINIMUM OF THREE YEARS
INCLUDING ALL ORIGINAL STRIP CHART RECORDINGS (e.g. continuous monitoring Instrumentation,
calibration and maintenance records}.
QUALIFIED OPERATING STAFP PROVIDED.
th) ESTABLISHED PROCEDURES AVAILABLE FOR TRAINING NEW OPERATORS.
(1) FILES MAINTAINED ON SPARE PARTS INVENTORY, MAJOR EQUIPMENT SPECIFICATIONS, AND
PARTS AND EQUIPMENT SUPPLIERS. ;
!J1 INSTRUCTIONS FILES KEPT FOR OPERATION AND MAINTENANCE OF EACH ITEM OF MAJOR
EQUfPMENT.
(V) OPERATION AND MAINTENANCE MANUAL MAINTAINED. ,
(II SPCC PLAN AVAILABLE.
(m) REGULATORY AGENCY NOTIFIED OF BY PASSINU. /Date; 1
(n) ANY BY-PASSING SINCE LAST INSPECTION.
!o) ANY HYDRAULIC AND/OR ORGANIC OVERLOADS EXPERIENCED.
a
u
a
a
a
n
a
a
a
a
a
a
n
a
a
YES D NO
YES D NO
YES D NO
YES D NO
YES D NO
YES O NO
YES D NO
"YES D NO
YES O NO
YES D NO
YES O NO
YES D NO
YiS D NO
YES O NO
YES D NO
ON/A
ON/A
DN/A
DN/A
ON/A
DN/A
ON/A
ON/A
DN/A
DN/A
DN/A
ON/A
DN/A
ON/A
ON/A
Figure 15.4 (Continued)
352
-------
PERMIT NO.
SECTION J - Compliance Schedules
PERMITTEE IS MEETING COMPLIANCE SCHEDULE. DYES DNO D N/A (l-'urlllt!r explanation attached .
CHECK APPROPRIATE PHASE(S):
D (a) THE PERMITTEE HAS OBTAINED THE NECESSARY APPROVALS FROM THE APPROPRIATE
AUTHORITIES TO BEGIN CONSTRUCTION.
D (b) PROPER ARRANGEMENT HAS BEEN MADE FOR FINANCING (mortgage commitments, grants, etc.I.
D (c) CONTRACTS FOR ENGINEERING SERVICES HAVE BEEN EXECUTED.
D (a) DESIGN PLANS AND SPECIFICATIONS HAVE BEEN COMPLETED.
D (el CONSTRUCTION HAS COMMENCED.
D (f) CONSTRUCTION AND/OR EQUIPMENT ACQUISITION IS ON SCHEDULE.
D (g) CONSTRUCTION HAS BEEN COMPLETED.
D (h) START.UP HAS COMMENCED.
D (i) THE PERMITTEE HAS REQUESTED AN EXTENSION OF TIME.
SECTION K • Self-Monitoring Program
'art 1 - Flow measurement tl-'urtlier explanation attached ;
PERMITTEE FLOW MEASUREMENT MEETS THE REQUIREMENTS AND INTENT OF THE PERMIT.
DETAILS:
D YES
D NO
ON/A
a) PRIMARY MEASURING DEVICE PROPERLY INSTALLED.
D YES
D NO
DN/A
TYPE OF DEVICE: GwEIB D PARSH ALL F LUME D.VlAGMETER D V ENTURI METE R D OTHER /Specify
-I
bl CALIBRATION FREQUENCY ADEQUATE. /Date.- of last calibration .
D YES
D NO
DN/A
c) PRIMARY FLOW MEASURING DEVICE PROPERLY OPERATED AND MAINTAINED.
D YES
O NO
DN/A
^[SECONDARY INSTRUMENTS (totalhers. recorders, etc.I PROPERLY OPERATED AND MAINTAINED.
D YES
D NO
el FLOW MEASUREMENT EQUIPMENT ADEQUATE TO HANDLE EXPECTED RANGES OF FLOW RATES. D Y6S
D NO
DN/A
"ar! 2 — Sampling (Further explanation attached ]
'ERMITTEE SAMPLING MEETS THE REQUIREMENTS AND INTENT OF THE PERMIT.
DETAILS:
D YES
D NO
DN/A
3) LOCATIONS ADEQUATE FOR REPRESENTATIVE SAMPLES.
D YES
D NO
DN/A
h) PARAMETERS AND SAMPLING FREQUENCY AGREE WITH PERMIT.
D YES
D NO
DN/A
CJ PERMITTEE IS USING METHOD OF SAMPLE COL LECTION REQUIRED BY PERMIT.
IF NO, DGRAB DMANUAL COMPOSITE D AUTOMATIC COMPOSITE FREQUENCY.
D YES
D NO
DN/A
:al SAMPLE COLLECTION PROCEDURES ARE ADEQUATE.
D YES
D NO
SAMPLES REFRIGERATED DURING COMPOSITING
D YES
D NO
DIM/
PROPER PRESERVATION TECHNIQUES USED
D YES
D NO
DN/A
FLOW PROPORTIONED SAMPLES OBTAINED WHERE REQUIRED BY PERMIT
D YES
D NO
DN/A
SAMPLE HOLDING TIMES PRIOR TO ANALYSES IN CONFORMANCE WITH 40 CFR 136.3
D YES
D NO
DN/A
el MONITORING AND ANALYSES BEING PERFORMED MORE FREQUENTLY THAN REQUIRED BY
PERMIT.
D YES
D NO
DN/A
f) IF (e) IS YES. RESULTS ARE REPORTED IN PERMITTEE'S SELF-MONITORING REPORT.
D YES
D NO
DM/.
'art 3 - Laboratory /l-'urlher explanation attached.
PERMITTEE LABORATORY PROCEDURES MEET THE REQUIREMENTS AND INTENT OF THE PERMIT.
DETAILS:
D YES
D NO
DN/A
a) EPA APPROVED ANALYTICAL TESTING PROCEDURES USED. (40 Ct-'K I S6.Jf
D YES
D NO
DN/A
b) IF ALTERNATE ANALYTICAL PROCEDURES ARE USED. PROPER APPROVAL HAS BEEN OBTAINED. D YES D NO
DN/A
cl PARAMETERS OTHER THAN THOSE REQUIRED BY THE PERMIT ARE ANALYZED.
D YES
D NO
DN/A
al SATISFACTORY CALIBRATION AND MAINTENANCE OF INSTRUMENTS AND EQUIPMENT.
D YES
D NO
DN/A
el QUALITY CONTROL PROCEDURES USED.
D YES
D NO
DN/A
f) DUPLICATE SAMPLES ARE ANALYZED. .
. % OF TIME.
D YES
D NO
DN/A
Iql SPIKED SAMPLES ARE USED.
OF TIME.
D YES
D NO
DN/A
Ihl COMMERCIAL LABORATORY USED.
D YES
D NO
DN/A
il COMMERCIAL LABORATORY STATE CERTIFIED.
D YES
D NO
DN/A
LAB ADDRESS
Figure 15.4 (Continued)
353
n
-------
•- -;r';n^^^rpi^;|$ii^:;:^^-£S;">f;^ PEBM1T N°-
- .' ::<^'
-------
as part of the permanent documentation.
15.3 FIELD FORMS
Appropriate field sheets must be completed at the time of sample
collection. These would include NPDES Compliance Inspection Report forms
(EPA Form 3560-3), Figure 15.4, (3) and Sample Tags, Figure 15.2.
In addition to sample tags and field sheets, a bound field notebook
must be maintained by the survey leader to provide a daily record of
significant events. All entries must be signed and dated. All members of
the survey party must use this notebook. Keep the notebook as a permanent
record. In a legal proceeding, notes, if referred to, are subject to
cross-examination and admissible as evidence.
15.4 REFERENCES
1. Crim R.L., editor. Model State Water Monitoring Program. EPA
440/9/74/-002, U.S. Environmental Protection Agency, Washington D.C.
1974.
2. NEIC Policies and Procedures Manual, U.S. Environmental Protection
Agency Office of Enforcement, National Enforcement Investigations
Center, Denver, Colorado, EPA 330/9/78/OQ1-R,
3. U.S. Environmental Protection Agency. NPDES Compliance Evaluation
Inspection (MCD-75) Manual, Enforcement Division Office of Water
Enforcement, Compliance Branch, Enforcement Division (EN-338),
Washington, D.C. EPA January, 1981.
355
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CHAPTER 16
QUALITY ASSURANCE
Quality assurance is an integral part of all sampling programs. The
objectives of quality assurance are to assure that the data generated is:
1. Meaningful 4. Precise
2. Representative 5. Accurate
3, Complete 6. Comparable
7. Admissable as legal evidence
Data must be well documented and representative of the condition being
monitored. To enable comparison with different data and with stated program
objectives, data must be presented in standard units. Quality assurance for
a sampling program should address all elements from sample collection to
data reporting while permitting operational flexibility. A quality
assurance plan should include, as an eissential part, a continuing education
and training program for the personnel: involved in the monitoring program.
This will enhance quality assurance capabilities and aid in keeping pace
with the scientific advancement occuring in the field.
16.1 OBJECTIVES OF QUALITY ASSURANCE PROGRAM
For the implementation of an effective and meaningful quality assurance
program it is imperative that its objectives are well defined, documented
and cover all activities that affect the quality of the data. Such written
objectives are needed to assure:
1. Effective participation in the quality assurance program by various
personnel in different organizations involved in a sampling
program.
2. Uniform direction and approach among the personnel participating in
a sampling program.
3. Integrated and planned course of action.
4. Performance evaluation against stated objectives.
To meet the above objectives, one individual within the organization
should be designated the Quality Assurance (QA) Coordinator. The QA
Coordinator should undertake activities such as quality planning, auditing,
and programs to insure reliability, the QA Coordinator should also have the
responsibility for coordinating all quality assurance activity so that
complete integration of the quality assurance plan is acheived.
356
-------
16.2 ELEMENTS OF A QUALITY ASSURANCE PLAN (1)
The quality assurance plan will contain the following elements:
1. A policy to establish parameter analytical criteria (accuracy,
precision, detection limit) for monitoring activities. Field,
sample handling, and test procedures are best established only
after establishment of criteria.
2. A systematic policy for selection and use of measurement and
sampling methodology. Where available, approved methodology must
be used. Where alternate methodology is necessary or where
approved methodology does not exist, the quality assurance plan
should state how the alternate or new methodology will be
documented, justified, and approved for agency use.
3. Documentation of operating procedures. The QA Coordinator should
establish the format for the procedures and see that the
documentation is done.
4. Intra-office quality assurance audits or acceptance criteria. The
QA Coordinator as part of the documented methodology of operating
procedures will approve or specify the intra-office audits.
Detailed quality assurance procedures are necessary for:
Personnel selection.
Sample site selection.
Sample collection, handling and preservation.
Calibration arid maintenance of instruments and equipment (field
and laboratory).
Intra-office audits (field and laboratory) for the data
acceptance with documentation for agency data credibility.
Review and approval of data before they are released.
Scheduled intra-office audits (field and laboratory) through the
QA Coordinator to assess the accuracy of field and laboratory
methodology.
An audit by the QA Coordinator on a systematic basis to see that
all the above activites are being done.
16.3 PERSONNEL TRAINING (1)
Successful implementation of a quality assurance plan ultimately
depends upon the competence of the monotoring personnel. All personnel
involved in any function affecting data quality (sample collection,
analysis, data reduction and quality assurance) should have sufficient
training in their appointed jobs to contribute to the reporting of complete
and high quality data. The quality assurance plan should therefore provide
357
-------
for periodic assessment of training needs and should describe the manner in
which training is to be accomplished. This will include both in-house and
external training and education.
Several methods of training are available to promote achievement of the
desired level of knowledge and skill required. The following are the
training methods most commonly used in the pollution control field:
16.3.1 On the Job Training (OJT)
An effective OJT program could consist of the following:
Observe experienced professionals perform the different tasks in
the measurement process.
Perform tasks under direct supervision of an experienced
professional.
Perform tasks independently but with adequate quality assurance
checks.
16.3.2 Short-term Course Training
A number of short term courses (normally two weeks or less) are
available from EPA regional offices, states, and private schools that
provide knowledge and skills to more effectively implement the NPDES
monitoring program.
16.3.3 Long-term Course Tra i ni ng
Numerous universities, colleges, and technical schools provide
long-term (quarters or semester length) academic courses in wastewater
treatment, analytical chemistry, environmental engineering, and other
disciplines.
16.3.4 Tra in ing Ev a1u a t i o n
The quality assurance plan needs to address training evaluation.
Training should be evaluated in terms of: 1) the level of knowledge
and skill achieved by the operator from the training, and 2) the overall
effectiveness of the training, including determination of training areas
that need improvement.
A good means of measuring skill improvement is to assign the trainee a
work task. Accuracy and/or completeness are commonly used indicators to
assess the trainee's proficiency. The tasks should be similar to the
following forms:
1. Sample Collection. Trainee would be asked to list or preferably
perform all steps in a sample collection for a hypothetical or real
case. This would include selection of sample site, duration and
358
-------
frequency of sampling, type of samples collected (grab or
composite), sampling and flow measuring equipment that would
provide high quality data. In addition, the trainee would be asked
to perform selected calculations. Proficiency would be judged in
terms of completeness and accuracy.
2. Analysis. Trainee would be provided unknown samples for analysis
normally measured in the field. As defined here, an unknown is a
sample whose concentrations are known to the work supervisor (OJT)
or the training instructor (short-term course training) but unknown
to the trainee. Proficiency would be judged in terms of accuracy,
16.4 QUALITY ASSURANCE IN SAMPLING
As a first step for quality assurance in sample collection, the
sampling program should delineate the details on sampling locations, sample
type, sample frequency, number of samples, duration of sampling, sample
volume, sample collection methods and holding times, equipment to be used
for the sample collection, sample containers, pretreatment of containers,
type and amount of preservative to be used, blanks, duplicates/triplicates,
spiked samples, replicates, chain of custody procedures, and any other
pertinent matter which will have a bearing on the quality assurance in
sample collection and handling. Guidelines on the above can be found in
this manual.
Despite a well defined sampling program, appropriate sampling and field
testing procedures, errors crop up due to equipment malfunction which
adversely affects the quality. Therefore, as a second step for quality
assurance, procedures-should be developed for routine testing, maintenance
and calibration of the equipment. Manufacturer's instructions are
appropriate guides on these procedures. These procedures should establish
routine maintenance, testing and calibration intervals, set up written
procedures for maintenance, testing and calibration, list the required
calibration standards, determine the environmental conditions during
calibration, and generate a documentation record system. Equipment should
be labeled to indicate the calibration data and when the calibration or
maintenance was performed and when it expires. Table 16.1 contains a
listing of quality assurange guidelines for selected field analysis,
equipment calibration and documentation.(1)
As a third step in quality assurance, random control checks should be
performed to make sure that appropriate sampling guidelines on sample
collection, handling and chain of custody are followed by the field
personnel; and deviations, if any, are rectified. Analytical quality
control as an aid to quality assurance must be performed through duplicate,
split, and spiked samples; sample preservative blanks, and known standard
solutions, and accuracy may be evaluated using control charts. For more
details on analytical quality control, refer to EPA's Handbook for
Analytical Quality Control in Water and Wastewater Laboratories.(2)
359
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TABLE 16.1 QUALITY ASSURANCE PROCEDURES FOR FIELD ANALYSIS AND EQUIPMENT (1)
Parameter
General
Daily
Quarterly
U)
-------
TABLE 16.1 (continued)
Parameter
General
Dally
Quarterly
2. pH (continued)
CO
en
3. Conductivity
Enter the make, model,
serial and/or ID num-
ber for each meter in
a log book.
Periodically.check the
buffers during the sample
run and record the data in
the log sheet or book.
Be on the alert for erratic
meter response arising from
weak batteries, cracked
electrode, fouling, etc.
Check response/and linearity
following highly acidic
or alkaline samples. Allow
additional time for
equilibration.
Check against the closest
•reference .solution each
time a violation is found.
Rinse electrodes thoroughly
between, samples and after
calibration.
1. Standardize with KC1 stan-
dards having similar
specific conductance
values to those anticipated
in the samples. Calculate
the cell constant using two
different standards
Take all meters to
lab for maintenance
calibration and
and quality control
checks.
Check temperature
compensation.
Check date of last
platinizing and
replatinize if
necessary.
(continued)
-------
TABLE 16.1 (continued)
Parameter
Genera I
Dally
Quarterly
CO
CT>
ro
3. Conductivity (continued)
4. Residual
Chlorine
Amperometric
Titration
Enter the make, model,
ID and/or serial num-
ber of each titration
apparatus in a log
book. Report results
to nearest 0.01 mg/L.
Cell Constant =
Standard Value
Actual Value
Specific Conductance =
Reading multiplied by
Cell Constant
Rinse cell after each
sample to prevent carry-
over.
Refer to instrument
manufacturer's instruc-
tions for proper opera-
tion and calibration
procedures.
Analyze NBS or EPA
reference standard
and record actual
vs. observed
readings in the log.
Return instrument to
lab for maintenance
and addition of fresh,
standardized reagents
Biweekly
(continued)
-------
TABLE 16.1 (continued)
Parameter
General
Daily
Quarterly
5. Temperature
Manual
CO
-------
TABLE 16.1 (continued)
Parameter
General
Daily
Quarterly
en
5. Temperature (continued)
Thermistors;
Thermographs
etc. (cont.)
Flow Measure-
ment
Automatic
Samplers~
If enforcement action is
anticipated, refer to
the procedure listed in
Manual above.
Enter the make, model,
serial and/or ID number
of each flow measurement
instrument in a log
book.
Enter the make, model
serial and/or ID num-
ber of each sampler in
a log book.
Record actual vs. standard
temperature in log book.
Install the devices in
accordance with the manu-
facturer's instructions
and with the procedures
given in this manual.
Preferable ranges are:
58-108, 15°-25°, 35°-
45°C.
, 59°-
. ,
77°, 45°-113°F)*
Affix record of calibra-
tion by NBS, manu-
facturer- or- other, to
the instrument log.§
Check intake velocity
vs. head (minimum of
three samples) and
clock time setting vs.
actual time interval.
* Initially and Bi-annually
§ Annually
-------
16.5 EPA MANDATORY QUALITY ASSURANCE PROGRAM
On May 30, 1979, the Administrator issued EPA policy requiring all
Regional Offices, Program Offices, EPA Laboratories, and the States to
participate in a centrally-managed Agency-wide Quality Assurance (QA)
Program.(3) The stated goal of the Program is to ensure that all environ-
mentally-related measurements which are funded by EPA or which generate data
mandated by EPA are scientifically valid, defensible, and of known precision
and accuracy. In a memorandum dated June 14, 1979, the Administrator
specifically addressed the QA requirements for all EPA extramural projects,
including contracts, interagency agreements, grants, and cooperative agree-
ments, that involve environmental measurements. Contractor or Grantees will
be required to extend the QA requirements of the contract to all
subcontractors. A complete and detailed QA project plan must be submitted
as a deliverable item. The QA project plan must be approved by the Project
Officer and the Quality Assurance Officer and must be adhered to.
16.5.1 Quality Assurance Reports
Contracts of short duration may require only a final QA report.
Contracts of longer duration may require periodic QA reports. The QA
reports will be separately identified from other contractually required
reports and should contain such information as:
1. Changes to QA program plan
2. Status of completion of QA project plan
3. Measures of data quality from the project
4. Significant quality problems, quality accomplishments,
and status of corrective actions
5. Results of QA performance audits
6. Results of QA system audits
7. Assessment of data quality in terms of precision, accuracy,
completeness, representativeness, and comparability
8. Quality-related training
16.5.2 Performance Audits
Quality Assurance Performance Audits. The inclusion of performance
audits will depend on the availabilty of performance evaluation samples or
devices for the measurements to be made. In the event that no performance
evaluation samples or devices are available for the measurements involved,
consideration should be given to the use of quality control or split samples
for cross-comparisons of results from offerers with those of EPA. A list of
QC Samples currently available from the Quality Assurance Branch,
EMSL-Cincinnati, U.S. Environmental Protection Agency, Cincinnati, Ohio
45268, is shown below:
365
-------
WATER QUALITY/WATER POLLUTION SAMPLES
WATER SUPPLY SAMPLES
Chlorophyll Spectro.
Chlorophyll Fluoro.
Demand
LAS
Mineral
Mun. Digested Sludge
Nutrients
Oil & Srease
Organo-P Pesticides
PCB's in Fish
PCB's in Oils
PCB's in Sediments
Other
Other
Urea-based Pesticides
Carbaryl
Cycloate
Diuron
EPTC
Lannate
Monurqn
Pebulate
Petro Hydrocarbons
Phenols (4AAP Method)
Residues
Trace Metals WP I
Trace Metals WP' II
Volatile Organics
WS Herbicides
WS Nitrate/Fluoride
WS Chi. Hyd. Pest. I
WS Chi. Hyd. Pest.II
WS Res. Free Chlorine
WS Trace Metals
WS Trihalomethanes
WS Turbidity
Other
Other
PRIORITY POLLUTANTS
Benzidines
Cyanide
Chi. Hyd. Pest. WP I
Chi. Hyd. Pest. WP II
Haloethers
Halogenated Purgeables I
Halogenated Purgeables II
Aromatic Purgeables
Phthalate Esters
Polynuclear Aromatics I
Polynuclear Aromatics II
PCB's (specific Aroclors)
Aroclor 1016
Aroclor 1221
Aroclor 1232
Aroclor 1242
Aroclor 1248
Aroclor '1254
Aroclor 1260
Aroclor 1262
16.5.3 QualityAssurance Project plan
A QA project plan must address the following: (4)
1. Title Page, with provision for approval signatures
2, Table of Contents
3. Project Descriptions
4. Project Organization(s) and Responsibilities
5. QA Objectives for Measurement Data, in terms of precision, accuracy,
completeness, representativeness, and comparability
6. Sampling Procedures
7. Sample Custody
8. Calibration Procedures, References and Frequency
9. Analytical Procedures
10. Data Reduction, Validation, and Reporting
11. Internal QC Checks and Frequency
12. QA Performance Audits, System Audits, and Frequency
13. QA Reports to Management
14. Preventive Maintenance Procedures and Schedule
366
-------
15. Specific Procedures to be used to routinely assess date precision,
representativeness, comparability, accuracy, and completeness of the
specific measurement parameters involved. This section will be
required for all QA project plans.
16. Corrective Action
16.6 REFERENCES
1. U.S. Environmental Protection Agency. NPDES Compliance Sampling
Inspection (MCD-51) Manual, Enforcement Division, Office of Water
Enforcement, Compliance Branch, May 4, 1977.
2. U.S. Environmental Protection Agency. Handbook for Analytical Quality
Control in Water and Waste-water Laboratories. EPA-600/4-79-019,
March, 1979.
3. U.S. Environmental Protection Agency. Guidelines and Specifications
for Implementing Quality Assurance Requirements for EPA Contracts.
QAMS-002/80, Office of Monitoring and Technical Support, Office of
Research and Development May, 1980.
4. U.S. Environmental Protection Agency, Guidelines and Specifications for
Implementing Quality Assurance Requirements for EPA Contracts, QAMS -
005/80, office of Monitoring and Technical Support, Office of Research
and Development, May 1980.
367
-------
CHAPTER 17
SAMPLE PRESERVATION
Other chapters in this handbook have provided guidance for all aspects
of sampling through collection of the sample. Once collected, it must be
analyzed immediately or stored in a container with a preservative to main-
tain the integrity of the sample. This chapter provides guidance on preser-
vation methods, holding times, storage conditions and container materials.
Complete preservation of samples, either domestic sewage, industrial
wastes, or natural waters, is a practical impossibility. Regardless of the
nature of the sample, complete stability for every constituent can never be
achieved. At best, preservation techniques can only retard the chemical and
biological changes that take place in a sample after the sample is removed
from the parent source. To maintain the integrity of the sample,
appropriate selection of containers, pretreatment of containers if necessary
and the holding times form the integral part of the sample preservation
program.
17.1 METHODS OF PRESERVATION
Methods of preservation are relatively limited and are intended
generally to: 1) retard biological action? 2) retard hydrolysis of chemical
compounds and complexesjand 3) reduce volatility of constituents.
Preservation methods are generally limited to chemical addition, pH
control, refrigeration, and freezing. Combinations of these methods are
often used for the preservation of the sample.
17.1.1 Chemical Addition
The most convenient preservative is a chemical which can be added to a
sample bottle prior to sampling. When the sample is added, the preservative
disperses immediately, stabilizing the parameter(s) of concern for long
periods of time. When the preservative!added interferes with other
parameters being measured, additional samples for those parameters must be
collected. For example, concentrated nitric acid added for the preservation
of some of the metals would interfere with BOD, so an additional sample must
be collected for BOD.
17.1.1.1 pH Control
pH control to preserve the sample is dependent upon chemical addition.
368
-------
As an example, to keep metal ions in a dissolved state concentrated nitric
acid is added to lower the pH to less than 2.
17.1.2 Freezing
Freezing has been the subject of many preservation studies.(1-16) It
is felt by some that freezing would be a method for increasing the holding
time and allowing collection of a single sample for all analysis. However,
the residue solids components (filterable and nonfilterable) of the sample
change with freezing and thawing.(8) Therefore* return to equilibrium and
then high speed homogenization is necessary before any analysis can be run.
This method may be acceptable for certain analysis but not as a general
preservation method.
17.1.3 Refrigeration
Refrigeration or icing has also been studied with various results.
(10-12, 17-21) This is a common method used in field work and has no
detrimental effect on sample composition. Although it does not maintain
integrity for all parameters, it does not interfere with any analytical
methods.
17.1.4 Preservation Guidelines
For NPDES Samples, the permit holder must use specific preservatives if
the sample cannot be analyzed immediately after collection. If preserved,
the analyses must be conducted within a specified time frame. Guidance
submitted for approval to the 304h committee, U.S. Environmental Protection
Agency, is shown in Table 17,1. Because approval and subsequent publication
in the Federal Register has not taken place as of publication of the
handbook, the reader is urged to keep abreast of existing NPDES regulations
and changes through Federal Register publications. In addition, some
parameter holding times differ for drinking water samples, for example,
microbiological and nitrate parameters.
Table 17.2 provides additional references and furnishes data on
preservation methods, storage and holding times for different parameters
found in various literature sources. However, for a specific application of
the data, reference to the original publication should be made.
17.1.5 Alternative Preservation Methods
Alternative preservation methods with different preservatives or
storage conditions can be used if its effectiveness can be demonstrated by
supporting data through preservation studies. Such preservation studies
must specify:
1. Type of water/wastewater used as a sample in the experiment
2. Type of containers used
3. Pretreatment of the container and the glassware used
4. Preservation methods used
5. Specific temperatures or temperature range used
369
-------
TABLE 17.1 REQUIRED CONTAINERS. PRESERVATION TECHNIQUES, AND HOLDING TIMES
Parameter Container
1-4.
5.
1.
GO
o 2.
4.
9.
10.
12.
15.
Bacterial Tests
Coliform, fecal P,G
and total
Fecal streptococci P,G
Inorganic Tests
Acidity P,G
Alkalinity P,6
Ammonia P,6
Biochemical oxygen P,G
demand
Biochemical oxygen P,G
demand, carbonaceous
Bromide P,G
Chemical oxygen P,G
demand
2 12
Preservative *
Cool, 4°C ,
0.0081 Na2S203°
Cool, 4°C R
0.0081 Na2S203
Cool, 4°C
Cool, 4°C
Cool , 4°C
H2S04 to pH <2
Cool, 4°C
Cool, 4°C
None required
Cool, 4°C
H2S04 to pH <2
Maximum 3
Holding Time
6 hours
6 hours
14 days
14 days
28 days
48 hours
48 hours
28 days
28 days
(continued)
-------
TABLE 17.1 (continued)
Parameter Container
2 12
Preservative *
Maximum -
Holding Time
Inorganic Tests
16.
17.
21.
23-24.-
25.
27.
28.
31.
43.
18.
35.
Chloride P,G
Chlorine, total P,G
residual
Color P,6
Cyanide, total and P,8
amenable to chlori-
nation
Fluoride p
Hardness P,G
Hydrogen ion (pH) P,G
Kjeldahl and organic P,G
Nitrogen
Metals4
Chromium VI P,G
Mercury P,G
None required
None required
Cool, 4°C
Cool, 4°C
NaQH to pH >12 6
0.6g ascorbic acid
None required
HN03 to pH<2
None required
Cool, 4°C
H2S04 to pH<2
Cool, 4°C
HN03 to pH<2
28 days
Analyze
immediately
48 hours
14 days9
28 days
6 months
Analyze immediately
28 days
24 hours
28 days
(continued)
-------
TABLE 17.1 (continued)
Parameter
Metals,
except above
38. Nitrate
39. Nitrate-nitrite
40. Nitrite
41. Oil and grease
42. Organic carbon
44. Orthophosphate
Container
P,6
P,G
P,G
P,G
G
P,G
P,G
2 12
Preservative '
HN03 to pH < 2
Cool, 4°C
Cool, 4°C
H2S04 to pH < 2
Cool, 4°C
Cool, 4°C
H2S04 to pH < 2
Cool, 4°C
HC1 or H2S04 to pH< 2
Filter immediately
Cool, 4°C
Maximum 3
Holding Time
6 months
48 hours
28 days
48 hours
28 days
28 days
48 hours
(continued)
-------
TABLE 17.1 (continued)
CO
~d
Parameter
46.
48.
49.
50.
53.
54.
55.
56.
57.
Oxygen, Dissolved
Probe
Winkler
Phenols
Phosphorus
(elemental)
Phosphorus, total
Residue, total
Residue, Filterable
Residue, Non-
filterable (TSS)
Residue, settleable
Residue, volatile
Container
G Bottle
and top
G bottle
and top
G only
G
P,G
P,G
P,S
P,G
P,G
P,G
2 12
Preservative '
None required
Fix on site and
store in dark
Cool, 4°C
H2S04 to pH <2
Cool, 4°C
Cool, 4°C
H2S04 to pH <2
Cool , 4°C
Cool, 4°C
Cool, 4°C
Cool , 4°C
Cool, 4°C
Maximum ^
Holding Time
Ana lyze
immediately
8 hours
28 days
48 hours
28 days
7 days
7 days
7 days
48 hours
7 days
(continued)
-------
TABLE 11.I (continued)
to
Parameter
61.
64.
65.
66.
67.
68.
69,
73.
Silica
Specific conductance
Sulfate
Sulfide
Sulfite
Surfactants
Temperature
Turbidity
Container
P
P»G
P,G
P,G
P,G
P,6
P,6
P,G
2 12
Preservative *
Cool, 4°C
Cool , 4°C
Cool, 4°C
Cool, 4°C, add
zinc acetate plus
sodium hydroxide
to pH>9
Cool, 4°C
Cool , 4°C
None required
Cool, 4°C
Maximum 3
Holding Time
28 days
28 days
28 days
7 days
Analyze
immediately
48 hours
Analyze
immediately
48 hours
(continued)
-------
TABLE 17.1 (continued)
Parameter
5
Organic Tests
Purgeable
halocarbons
Purgeable aro-
matics
OJ
en
3,4. Acrolein and
acrylonitrile
Phenols
Container
G, Teflon-
lined septum
6, Teflon-
lined septum
G, Teflon-
lined septum
G, Teflon-
lined cap
2 12
Preservative *
Cool, 4°C c
0.0081 Na0S0On
, L c. 6
Cool, 4°C ,
0.008% Na2S203°
HC1 to pH <210
Cool, 4°C fi
0.0081 Na2S203
Adjust pH to 4-511
Cool, 4°C ,
0.0081 Na2S203°
Maximum -
Holding Time
14 days
14 days
14 days
7 days until
extraction, 40
days after
extraction
(continued)
-------
TABLE 17.1 (continued)
co
~»i
. CTt
Parameter
Benzi dines
Phthalate esters
Nitrosamines
... „. PCB's
Nitroaromatics and
isophorone
Polynuclear aromatic
hydrocarbons
Haloethers
Container
G, Teflon-
lined cap
G, Teflon-
lined cap
G, Teflon-
lined cap
G, Teflon-
lined cap
G, Teflon-
lined cap
G, Teflon-
lined cap
G, Teflon-
lined cap
2 12
Preservative *
Cool, 4°C ,
0.008% Na2S203D
Cool, 4°C
Cool, 4°C
store in dark K
0.008% Na2$203
Cool 4°C8
— - pH 5-9
Cool, 4°C
Cool, 4°C ,
0.008% Na2S20,°
store in aark
Cool, 4°C ,
0.008% Na2$2Q3
Maximum 3
Holding Time
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction ,
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction
(continued)
-------
TABLE 17.1 (continued)
Parameter
87.
1-70.
1-5.
Chlorinated
hydrocarbons
TCDD
Pesticides Tests
Pesticides
Radiological Tests
Alpha, beta and
radium
Container
G, Teflon-
cap
G, Teflon-
cap
G, Teflon-
lined cap
P,G
2 12
Preservative *
Cool, 4°C
Cool, 4°C ,
0.0081 Na2S203
Cool, 4£c
pH 5-9B
HN03 to pH<2
Maximum ~
Holding Time
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction
7 days until
extraction, 40 days
after extraction .
6 months
(continued)
-------
TABLE 17.1 NOTES
1. Polyethylene (P) or Glass (6).
2. Sample preservation should be performed immediately upon sample
collection. For composite samples, each aliquot should be
preserved at the time of collection. When use of an automated
sampler makes it impossible to preserve each aliquot, then samples
may be preserved by maintaining at 4 C until compositing and sample
splitting is completed.
3. Samples should be analyzed as soon as possible after collection.
The times listed are the maximum times that samples may be held
before analysis and still considered valid. Samples may be held
for longer periods only if the permittee, or monitoring laboratory,
has data on file to show that the specific types of samples under
study are stable for the longer time. Some samples may not be
stable for the maximum time period given in the table. A
permittee, or monitoring laboratory, is obligated to hold the
sample for a shorter time if knowledge exists to show this
is necessary to maintain sample stability,
4. Samples should be filtered immediately on-site before adding
preservative for dissolved metals.
5. Guidance applies to samples to be analyzed by GC, LC, or GC/MS for
specific compounds.
6. Should only be used in the presence of residual chlorine. g
7. For the analysis of diphenylnitrosamine, add 0.008% Na2S203 and
adjust pH to 7-10 with NaOH within 24 hours of sampling.
8. The pH adjustment may be performed upon receipt at the laboratory
and may be omitted if the samples are extracted with 72 hours of
collection. For the analysis of;aldrin, add 0.0081 NagSpO,.
9. Maximum holding time is 24 hours when sulfide is present.
10. Sample receiving no pH adjustment must be analyzed within seven
days of sampling.
11. Samples for acrolein receiving no pH adjustment must be analyzed
within 3 days of sampling.
12. When any sample is to be shipped by common carrier or sent through
the United States Mails, it must comply with the Department of
Transportation Hazardous Materials Regulations (49 CFR Part 172).
The person offering such material for transportation is. responsible
for ensuring such compliance. For the preservation requirements of
Table 17.1, the Office of Hazardous-Materials, Materials
Transportation Bureau, Department of Transportation has determined
that the Hazardous Materials Regulations do not apply to the
following materials: Hydrochloric acid (HC1) in water solutions at
concentrations of 0.04% by weight or less (pH about 1.96 or
greater); Nitric acid (HNO.,) in water solutions at concentrations
of 0.15% by weight or less (pH about 1.62 or greater); Sulfuric
acid (HpSQ*) in water solutions at concentrations of 0.35% by
weight or less (pH about 1.15 or greater); and Sodium hydroxide
(NaOH) in water solutions at concentrations of 0.080% by weight or
less (pH about 12.30 or less).
378
-------
"si
vo
17.2 INFORMATION ON PRESERVATION AND STORAGE OF PARAMETERS IN
VARIOUS WATERS AND WASTEWATERS
Parameters Sample type
DEMAND
PARAMETERS
Biochemical Raw sewage
Oxygen
Demand
(BOD)
Preservation Container
Method Material
N.S. Glass
Temperature
37°C n
10°-24°C
A
Holding Time
6-12 hours (21)
12-24 hours (21)
6 days (21)
Raw Sewage
Raw semi-treated
or fully treated
domestic sewage
N.S.
Frozen in a
mixture of
acetone and dry
ice or finely
ground dry ice
N.S.
4°C
,Up to 1 day in
composite sam-
pling systems (10)
Polyethylene Approximately 6 months; on
C V//1* JUl»J»*.«*»*!• AllfiAf
-5UC
thawing either
with warm water
or at room temp-
erature, analyze
using seeded
technique (5)
Raw wastewater
1:4 settled sewage
to water from a
natural stream
Raw sewage
Freezing Polyethylene -15 C
coated milk
cartons
60-80 mg/L Plastic
HgCl2
890 mg/L HgCl2 Plastic
Room temper-
ature
Room temper-
ature
236 days, analyze
using seeded
technique (8)
18 days (22)
43 days (23)
N.S.-Not Stated.
(continued)
-------
TABLE 17.2 (continued)
CO
00
o
Parameters
DEMAND
PARAMETERS
Chemical
Oxygen
Demand
(COD)
- . . . .
Dissolved
oxygen (DO)
Sample type
1:4 settled
sewage to water
from a natural
stream
Raw sewage
Raw sewage
Raw sewage
Sea water
Sea water
Preservation Container
Method Material
60-80 mg/L Plastic
HgCl2
890 mg/L HgCl2 Plastic
N.S. . Glass
N.S. N.S.
0.51 Chloroform Glass
+ 0.51 phenol
Acidulating Glass
water to pH 1.5
with 2.5 mL
H2S04; 5 mL HC1
per liter of
sample
Temperature
Room temper-
ature
Room temper-
ature
10 -24°C
A
4°C
22°C
22°C
Holding Time
18 days (22)
43 days
6-12 hours (21)
12-24 hours (21)
... 6 days (21)
Several days (10)
20 days (24)
22 days (24)
(continued)
-------
TABLE 17.2 (continued)
CO
00
Parameters
DEMAND
PARAMETER
Total
Organic
Carbon (TOC)
METALS:
Aluminum
Sample Type
Settled sewage,
biological
filter effluent
Waters in the
Preservation
Method
1 ml saturated
Ag?SO» solution
(i.e. 4 mg of Ag+)
to a liter of
sample
Samples frozen
Container
Material
Glass
Polyethylene
Temperature
Refrigerate
at 4°C
-20°C
Holding Time
3 days (25)
In dark, 14
Cadmium
zone of mixing
of river and
sea waters in
estuaries
Natural fresh
water
Stock aqueous
solutions pre-
pared in labor-
atory
rather than
acidified
1 ml 4M H?SO,
per 100 ml
sample and
filtered
through glass-
fiber filters
Acidification to
pH 2 with HNO,
Polyethylene Room temper-
ature
Polyethylene
and borosili-
cate glass
N.S.
days (26)
4 weeks (27)
32 days (28)
Lead
Stock aqueous
solutions pre-
pared in labor-
atory
Acidification to
pH 2 with HN03
Borosili cate N.S.
glass
24 days (28)
(continued)
-------
TABLE 17.2 (continued)
CO
CO
ro
Parameters
METALS: (cont.
Mercury
Potassium
Silver
Sodium
Zinc
Sample Type
Distilled water
solutions con-
taining 0.1-10.0
Distilled water
solutions con- .
taining 0.1-10.0
1:4 settled
sewage and nat-
ural stream water
Stock aqueous
solutions pre-
pared in labor-
atory
1:4 settled sew-
age and natural
stream water
Stock aqueous
solutions pre-
pared in labor-
atory
Preservation
Method
Acidified with 5%
(v/v)2HN03 + .05%
Acidified with 5%
(v/v)2HN03 + .01%
Approx. 1.5 mL
saturated HgCl2
per liter of
sample (60-80
mg/L HgCl2)
Acidification to
pH 2 with HN03
Approx. 1.5 mL
saturated HgCl?
-per liter sample
(60-80 mg/L
Hgci2)
Acidification to
pH 2 with HN03
Container
Material Temperature
Polyethylene N.S
Glass N.S.
Plastic Room Temper-
ature
Polyethylene Room, temper-
ature
Plastic Room temper-
ature
Polyethylene N.S.
preferred
over boro-
silicate
glass
Holding Time
10 days (29)
5 months (29)
18 days (22)
36 days (28)
18 days (22)
60 days (28)
(continued)
-------
CO
03
00
TABLE 17.2 (continued)
Parameters Sample Type
METALS: (cont.)
Cadmium Natural lake
water
Copper Natural lake
water
Manganese Natural lake
water
Zinc Natural lake
water
Preservation
Method
Acidified to
pH 1
Acidified to
pH 1
.25 mL 3.5 N
nitric acid
after arrival
at the lab-
oratory
Acidified to
pH 1
Acidified to
pH 1
.25 mL 3.5 N
nitric acid
after arrival
at the lab-
oratory
Container
Material Temperature
Pyrex glass -15 C
and
polyethylene
Pyrex glass -15°C
and
polyethylene
25 mL glass Room temper-
vials with ature
polyethylene
snap-caps
Pyrex glass -15°C
and
polyethylene
Pyrex glass -15°C
and
polyethylene
25 mL glass Room temper-
vials with ature
polyethylene
snap-caps
Holding Time
184 days (30)
184 days (30)
1 year (31)
184 days (30)
184 days (30)
1 year (31)
^continued)
-------
CO
TABLE 17.2 (continued)
Parameters
NUTRIENTS:
Ammonia
Nitrogen
Sample Type
Relatively
unpolluted
bay waters
Sea waters
(off shore)
Near shore
and estuarine
waters (filtered
and fortified
samples)
Synthetic fresh
water, unpollut-
ed fresh water,
(filtered)
chemically treated
domestic sewage,
polluted sea water
(filtered)
Preservation
Method
+2
40 mg Hg per
liter of sample
0.4 g phenol per
100 ml of sample
Slow freezing
Freezing
• '
Unpreserved
Container
Material Temperature
Plastic 4°C
Glass N.S.
Polyethylene Frozen
Glass tubes ^23°C
polyseal
caps
Polyethylene 4°C
Holding Time
30 days (12)
2 weeks (14)
20 days (14)
3 months (7)
1-3 days (32)
(continued)
-------
co
00
tn
TABLE 17.2 (continued)
Parameters
NUTRIENTS:
Ammonia
Nitrogen
Ammonia
(soluble)
Sample Type
Strongly pollu-
ted water
Strongly pollu-
ted water
Raw Sewage
Surface runoff
Amended and un-
amended river
water
Preservation
Method
Approx. 1,5 ml
saturated HgCl?
per liter (75
mg/L)
Approx. 3.0 ml
40« formalin
solution per
liter of sample
(890 mg/L)
890 mg/L HgCl2
Freezing
Refrigeration
Phenylmercuric
acetate (PMA):
20 mg PMA per
liter of sample
40 mg HgCl2 per
liter of sample
Freezing
Phenylmercuric
acetate (PMA):
20 mg PMA per
liter of sample
Container
Material
Plastic
Plastic
N.S.
Plastic
Plastic
Plastic
Plastic
Plastic
Plastic
Temperature
Room Temper-
ature
Room Temper-
ature
N.S.
-20°C
4DC
4°C
-20°C
4°C
A A
4°C or 23°C
Holding Time
18 days (22)
18 days (22)
43 days (23)
In. dark, 12 wks.
In dark, 12 wks.
(33)
In dark, 12 wks.
(33)
In dark, 12 wks.
(33)
In dark, 12 wks.
(33)
In dark, 12 wks.
(33)
(continued)
-------
TABLE 17.2 (continued)
CO
03
Parameters
NUTRIENTS:
Ammonia
(soluble)
(cont.)
Kjeldahl
nitrogen
Sample Type
(cont.)
Tile drainage water
Relatively unpol-
luted bay waters
Preservation
Method
Freezing
Phenylmercuric
acetate (PMA):
(20 mg PMA per
liter of sample)
40 mg HgClp per
liter of sample
40 mg Hg+2 per
liters of sample
Container
Material
Plastic
Plastic
Plastic
Plastic
Temperature
-20°C
f\
4°C
f\
4°C
4°C
Holding Time
In dark, 12 wks.
(33)
In dark, 12 wks.
(33)
In dark, 12 wks.
(33)
7 days (12)
Synthetic fresh
water, unpolluted
fresh water chem-
ically treated do-
mestic sewage and
polluted sea water
Strongly polluted
water
Unpreserved
I ml 0.02%
mercury (II)
chloride per
100 ml of
sample
Approx. 1.5 ml
of saturated
HgCl« per liter
(75 fcg/L)
Polythylene 4°C
Polyethylene 4°C
Plastic
Room Temp.
Up to 3 days (34)
Up to 3 days (34)
18 days (22)
Raw manure slur-
ries,
ditch
oxidation
mixed liquor
Freezing and
fast thawing
or slow thawing
Refrigeration
Whirl
bags
Whirl
bags
pack
pack
N.S.
6-10°C
5
5
weeks
weeks
(35)
(35)
(continued)
-------
TABLE 17.2 (continued)
00
Parameters Sample Type
NUTRIENTS: (cont.)
Kjeldahl
nitrogen (cont.)
Nitrate Relatively unpol-
Nitrogen luted fresh water
Preservation
Method
Acidification
cone H9SO» to
pH 2 L *
40 mg Hg+2
Container
Material
Whirl pack
bags
Plastic
Temperature
6-10°C
6-10°C
4°C
Holding Time
5 weeks (35)
5 weeks (35)
Up to 3 days
(34)
(filtered), chem-
ically treated do-
mestic sewage,
polluted sea
water (filtered)
4 to 1 mixture of
surface water and
settled sewage
Strongly polluted
water sample
1 ml Q.02% mer-
cury (II)
chloride per
liter of sample
22 or 66 mg mer-
cury (II)
chloride per
liter of sample
Approx. 1.5 ml
saturated mer-
cury (II)
chloride solution
per liter (i.e.
60-80 mg/L of
mercury (II)
chloride)
Polyethylene 4 C
'Glass
22±2°C
Plastic
Room Temp.
28 days (34)
3 weeks (36)
18 days (22)
(continued)
-------
TABLE 17.2 (continued)
Parameters Sample Type
Preservation
Method
Container
Material
Temperature Holding Time
NUTRIENTS: (cont.)
Nitrate
Nitrogen (cont.)
CO
CO
00
Nitrite
Nitrogen
Surface runoff,
tile drainage
water, river
water
Surface runoff
Strongly polluted
water
Sea water (fil-
tered) and nitrate
enriched
Approx. 3,0 ml
40% formalin
solution per
liter sample
(890 mg/L)
Freezing
20 mg PMA per
liter sample
40 mg HgClp per
liter of sample
Approx. 1.5 ml
of saturated
mercuric chlo-
ride solution
per liter sample
(i.e. 60-80 mg/L
mercuric chloride)
Approx. 3.0 ml
40% formalin
solution per
liter sample
(890 mg/L)
Freezing
Plastic
Plastic
Plastic
Plastic
Plastic
Plastic
Pyrex glass
Room Temp. 18 days (22)
-20°C
4°C or 23°C
4°C
In dark, 12 wks,
(33)
In dark, 12 wks,
(33)
In dark, 3 wks.
(33)
Room Temp. 18 days (22)
Room Temp. 18 days (22)
-18°C
220 days (4)
(continued;
-------
CO
00
<£>
Parameters
NUTRIENTS:
Nitrite
Nitrogen
(cont.)
Sample Type
(cont.)
Lake water
(unenriched)
Lake water
(enriched with
TABLE 17.2
Preservation
Method
1 mL saturated
mercuric chlo-
ride per liter
sample
1 mL saturated
mercuric chlo-
(continued)
Container
Material
Glass
Glass
Temperature
Refrigerated
at 7°C
Refrigerated
at 6°C
Holding Time
11 days (20)
6 days (20)
6 days (20)
nitrite)
Relatively un-
polluted bay
waters
4 to 1 mixture of
surface water and
settled sewage
ride solution
per 300 mL
sample
+2
40 mg Hg per
liter sample
66 mg of mercury
(II) chloride
per liter of
sample
Plastic
Glass
4°C
22±2°C
7 days (12)
45 days (36)
(continued)
-------
TABLE 17.2 (continued)
GO
U3
O
Parameters
NUTRIENTS:
Orthophos-
phate or
total phos-
phate
Sample Type
(cont.)
Waters containing
algae
Polluted fresh
water, polluted
sea water, strong-
ly polluted sea
water, biologi-
cally treated sewage
Preservation
Method
Refrigeration
1 ml 8N sulfuric
acid per 100 ml
filtered sample
Container
Material Temperature Holding Time
N.S. 3-5°C Overnight (11)
Polyethylene N.S. For samples tha'
cannot be
analyzed with-
in 8 hrs.
(37)
Estuarine waters
Soluble Inor-
ganic Phos-
phorus (SIP)
Strongly polluted
waters
Surface runoff
Slow freezing
and sediment
removed by centri-
fugation
+2
40 mg Hg per Glass
liter sample
+2
40 mg Hg per Glass
liter sample
Approx. 1.5 ml Plastic
saturated HgCl?
per liter (75
mg/L)
N.S. N.S.
I.S. N.S.
-10°C
4°C
Room Temp.
2°C
-201
One month (12)
Few days (12)
18 days (22)
3 days (37)
3 days (37)
(continued)
-------
TABLE 17.2 (continued)
Parameters
NUTRIENTS:
Soluble
Inorganic
Phosphate
Sample Type
(cont.)
Surface runoff,
tile drainage
Preservation
Method
Freezing
Container
Material
Plastic
Temperature Holding Time
-20°C In dark, 12 wks,
(33)
CO
(£>
Phenylmercuric
acetate (PMA)
20 mg PMA per
liter of sample
40 mg HgCU per
liter sample
Ammended river Freezing
water (45 ml
river water + 5 ml
of solution con-
taining 100 ppm
NH.-N, 100 ppm of
NO--N and 5 ppm
of orthophosphate),
and natural rainwater
40 mg HgClp per
liter sample
Plastic
Plastic
Plastic
Plastic
4°C
4UC
-20°C
4°C
In dark, 6 wks.
(33)
In dark, 6 wks.
(33)
In dark, 12 wks.
(33)
In dark, 12 wks,
(33)
Sea water
Addition of
Chloroform (0.6-
0.835 v/v) before
freezing
Polyethylene -5 to -10°C
Stored until
thawed for
analysis (38)
(continued)
-------
OJ
U3
I\3
.TABLE 17.2 (continued)
Parameters
Sample Type
Preservation
Method
Container
Material Temperature
Holding Time
PHYSICAL/MINERAL
Alkalinity
Chloride
Conductivity
Total
hardness
1:4 settled sewage
to natural stream
water
1:4 settled sewage
and natural stream
water
Raw sewage
1:4 settled sewage
and natural stream
water
Raw sewage
1:4 settled sewage
and natural stream
water
Approx, 1.5 ml
saturated mer-
curic chloride
solution per lit-
er sample (60-80
mg/L HgCl2)
Approx. 1.5 ml
saturated mer-
curic chloride
solution per lit-
er sample (60-80
mg/L HgCl2)
890 mg/L FigCl2
Approx. 1.5 mL
saturated mer-
curic chloride
solution per lit-
er sample (60-80
mg/L HgCl2)
890 mg/L HgCl2
Approx. 1.5 mL
saturated mer-
curic chloride
solution per lit-
er sample (60-80
mg/L HgCl2)
Plastic Room temp.
(Not in
dark)
Plastic Room temp.
(Not in
dark)
N.S. • - N.S.
Plastic Room temp.
(Not in
dark)
N.S. N.S.
Plastic Room temp.
(Not in
dark)
18 days (22)
18 days (22)
43 days (23) -
18 days (22)
43 days (23)
18 days (22.)
(continued)
-------
co
U3
co
Parameters
Sample Type
TABLE 17.2
Preservation
Method
(continued)
Container
Material
Temperature Holding Time
PHYSICAL/MINERAL (cent.)
Magnesium
hardness
Phenols
Raw sewage
All types of water
and wastewaters
*
All types of water
and wastewaters
890 mg/L HgClg
1.5 ml of IN
NaOH per liter
N.S.
3 ml 10% CuSO.
solution per
liter sample
N.S,
N.S.
Stoppered
glass bot-
tles
Stoppered
glass bot-
tles
N.S. 43 days (23)
N.S. (39)
N.S. preferably to
analyze
shortly after
collection
(19)
Refrigeration Analyze within
days (19)
Sulfate
1:4 settled sewage
and natural stream
water
Raw sewage
Approx. 1.5 ml
saturated mer-
curic chloride
solution per
liter (60-80
mg/L HgCl2)
890 mg/L HgCl9
Plastic
I.S.
Room Temp.
(Not in
dark)
I.S.
18 days (22)
43 days (23)
-------
6, Duration of storage
7. Stored in light or darkness
8. Quality Control Samples - spikes, duplicates.
9. Blanks - controls
10. Number of samples analyzed, and results
11. Statistical analysis, precision and accuracy
17.2 CONTAINERS
A variety of factors affect the choice of containers and cap material.
These include resistance to breakage, size, weight, interference with
constituents, cost and availability. There are also various procedures for
cleaning and preparing bottles depending upon the analyses to be performed
on the sample.
17.2.1 Container Material
The two major types of container materials are plastic and glass.(22)
Glass: Plastic:
1. Kimax Or Pyrex brand - 1. Conventional polyethylene
borosilicate 2. Linear polyethylene
2. Vycor - generally lab ware 3. Polypropylene
3. Ray-Sorbor Low-Actinic - 4. Polycarbonate
generally lab ware 5. Rigid polyvinyl chloride
4. Corex - generally lab ware 6. Teflon
All these materials have various advantages and disadvantages. Kimax
or Pyrex brand borosilicate glass is inert to most materials and is
recommended where glass containers are used. Conventional polyethylene is
to be used when plastic is acceptable because of reasonable cost and less
absorption of metal ions. The specific situation will determine the use of
glass or plastic. However, use glass containers for pesticides, oil and
grease, and other organics. Table 17.3 summarizes the advantages and
disadvantages of these materials.
17.2.2 Container Caps
There are two major types of plastic used in container caps:
polyethylene and bakelite with liners. Polythylene caps are recommended for
ease of cleaning unless oil and grease analyses are to be performed. Caps
with Teflon liners should be used for pesticides and oil and grease samples.
Silicone rubber material should be avoided for Trace Metals because of Zinc
contaminations.(40) There are three liner types available and the
advantages/disadvantages are listed in Table 17.4.
394
-------
TABLE 17.3 COMPARISON OF GLASS AND
PLASTIC CONTAINERS
Borosilicate Glass
Conventional Polythylene
Interference
with sample
Weight
Resistance to
breakage
Cleaning
Sterilizable
Space
Inert to all constituents
except strong alkali
Heavy
Very fragile
Easy to clean
Yes
Takes up considerable
space
Good for most constituents
except organics and oil
and grease
Light
Durable
Some difficulty in removing
adsorbed components
In some instances
Cubitainers - Substantial
space savings during
extended field studies.
17.2.3 Container Structure
Use a wide mouth container in most instances. This structure will
permit easy filling and sample removal. It is also easily cleaned, quickly
dried, and can be stored inverted. Use a narrow neck bottle when
interaction with the cap liner or outside environment is to be minimized.
Use a Solvent cleaned glass container for pesticide sample collection.(24)
17.2.4 Disposable Containers
Use disposable containers when the cost of cleaning is high. These
containers should be precleaned and sterile. The most commonly used
disposable container of this type is the molded polyethylene cubitainer
shipped nested and sterile to the buyer. However since their cubic shape
and flexible sides make them almost impossible to clean thoroughly, use
these containers only once.
17.2.5 Container Washing
The following procedure should be followed to wash containers and caps
for inorganic and general parameters:
1. Wash containers and caps with a non-phosphate detergent and scrub
strongly with a brush (if possible wash liners and caps
separately).
2. Rinse with tap water, then distilled water.
395
-------
TABLE 17.4 COMPARISON OF CAP LINERS
Liner Type
Advantages
Disadvantages
Wax coated paper
Neoprene
Teflon
Generally applicable
to most samples,
Inexpensive
Same as wax coated
paper
Applicable for all
analyses
Minimizes container/
sample interaction
Must be inspected prior
to each because of
deterioration. Cannot
use with organics
Same as wax coated paper
High cost
3. Invert to drain and dry.
4. Visually inspect for any contamination prior to storage.
5. If the container requires additional cleaning, rinse with a chromic
acid solution (35 mL saturated sodium dichromate solution in 1
liter of sulfuric acid - this solution can be reused). Then rinse
with tap water and distilled water and dry as indicated above.
17.2.6 Container Preparation
For certain parameters, a special cleaning procedure is needed to avoid
adsorption or contamination due to interaction with container walls. These
procedures are outlined below;
1. Metals: If metals are to be analyzed, rinse the container with a
solution of one part nitric acid to four parts water, then with
distilled water. If phosphorus is to be analyzed, rinse the
container with a solution of one part hydrochloric acid to one part
water, followed by distilled water. Treat the caps similarly.
2. Organics: If Oil and Srease or Pesticides are to be analyzed,
rinse the sample container with methylene chloride, followed by
acetone. For Pesticide analysis, use pesticide grade hexane or
acetone. The container should have been previously cleaned with
chromic acid solution as described in Section 17.2.5. Treat the
container caps similarly.
3. Sterilization: For microbiological analyses, sterilize the
container and its stopper/cap by; autoclaving at 121 C for 15
minutes or by dry heat at 180 C for two hours. Heat-sensitive
plastic bottles may be sterilized with ethylene oxide at low
temperatures. Wrap bottles in kraft paper or cover with aluminum
foil before sterilization to protect against contamination. An
acceptable alternative for emergency or field use is sterilization
of containers by boiling in water for 15 minutes.
396
-------
17.3 HOLDING TIME
Holding time is the time interval between collection and analysis. In
general, the shorter the time that elapses between collection of a sample
and its analysis, the more reliable will be the analytical results.
It is impossible to state exactly how much time may be allowed to
elapse between collection of a sample and its analysis; this depends on the
character of the sample, particular analysis to be made, and the conditions
of the storage.
For NPDES purposes, in accordance with Federal Register, part 136
follow the recommendations given in Table 17.1, and keep abreast of revised
holding times that will be published in the Federal Register.
For information purposes, however, data relating to holding times for
general and inorganic parameters was collected from various literature
sources and is tabulated in Table 17.2.
17.4 SAMPLE VOLUME
The volume of sample collected should be sufficient to perform all the
required analyses plus an additional amount to provide for any quality
control needs, split samples or repeat examination. Although the volume of
sample required depends on the analyses to be performed, the amount required
for a fairly complete analysis is normally about eight liters, (about two
gallons). The laboratory receiving the sample should be consulted for any
specific volume requirements. Individual portions of a composite sample
should be at least 100 milliliters in order to minimize sampler solids bias.
Depending on the sampling frequency and sample volume, the total composited
sample should be a minimum of 8 liters (about 2 gallons). Refer to EPA's
Methods for Chemical Analysis of Water and Wastes 1979, EPA 600/4-79-020,
for the sample volumes required for specific types of pollutant analyses.
17.5 REFERENCES
1. Collier, A.W. and K.T. Marvin. Stabilization of the Phosphate Ratio of
Sea Water by Freezing. U.S. Government Printing Office, Washington,
71-76, 1953.
2. May, B.Z. Stabilization of the Carbohydrate Content of Sea Water
Samples. Limnology and Oceanography, 5: 342-343, 1960.
3. Heron, J. Determination of Phosphate in Water after Storage in
Polyethylene. Limnology and Oceanography, 5: 316-321, 1960.
4. Procter, R.R. Stabilization of the Nitrite Content of Sea Water By
Freezing. Limnology and Oceanography, 7: 479-480, 1962.
397
-------
5. Fogarty, W.J. and M.E. Reeder. BOD Data Retrieval Through Frozen
Storage. Public Works, 88-90, March, 1964.
6. Morgan, F. and E.F. Clarke. Preserving Domestic Waste Samples by
Freezing. Public Works, 73-75, November, 1964.
7. Marvin, K.T. and R.R. Proctor. Stabilizing the Ammonia-Nitrogen
Content of Estuarine and Coastal Waters by Freezing. Limnology and
Oceanography, 10: 288-289, 1965.
8. Zanoni, A.E. Use of Frozen Wastewater as a Test Subtrate. Public
Works, 72-75, November, 1965
9. Tyler, L.P. and E.G. Hargrave. Preserving Sewage Seed for BOD
Analysis. Water and Sewage Works, 12: 181-184, May, 1965.
10. Agardy, F.J. and M.L. Kiado. Effects of Refrigerated Storage on the
Characteristics of Wastes. Industrial Waste Conference (21st) Purdue
University, 1966.
11. Fitzgerald, G.P. and S.L. Faust. Effect on Water Sample Preservation
Methods on Release of.Phosphorous From Algae. Limnology and
Oceanography, 12: 332-334, 1967.
12. Jenkins, D. The Differentiation, Analysis and Preservation of Nitrogen
and Phosphorous Forms in Natural Waters. Advances in Chemistry Series
73. American Chemical Society, Washington, D.C., 265-279, 1968.
13. Philbert, F.J. The Effect of Sample Preservation by Freezing Prior to
Chemical Analysis of Great Lakes Water. Proc 16th Conference. Great
Lakes Res. 282-293, 1973.
14. Degobbis, D. On the Storage of Sea Water Samples for Ammonia Determin-
ation. Limnology and Oceanography, 15: 146-150. January, 1970.
15. Burton, J.D. Problems in the Analysis of Phosphorus Compounds. Water
Research, Great Britain, 7: 291-307, 1973,
16. Harms, L.L., J.N. Dornbush and J.R. Anderson. Physical and Chemical
Quality of Agricultural Land Runoff. Journal WPCF, 46: 2460-2470,
November, 1974.
17. Phillips, G.E. and W.D. Hatfield. Preservation of Sewage Samples.
Water Works and Sewage Journal, 285-288, June, 1941.
18. Moore, E.W. Long Time Biochemical Oxygen Demands at Low Temperature.
Sewage Works Journal, 13 (3): 561-577, May, 1941.
19. Ettinger, M.B., S. Schott and C.C. Ruchott. Preservation of Phenol
Content in Polluted River Water Samples Previous to Analysis. Journal-
AWWA, 35: 299-302, March, 1943.
398
-------
20. Brezonik, P.L. and G.F. Lee. Preservation of Water Samples for In-
organic Nitrogen Analysis with Mercuric Chloride. Air and Water
Pollution (Great Britain), 10: 549-553, 1966.
21. Loehr, R.C. and B. Bergeron. Preservation of Wastewater Samples Prior
to Analysis. Water Research (Great Britain) 1: 557-586, 1967.
22. Hellwig, D.H.R. Preservation of Water Samples. International Journal
of Air Water Pollution, 8: 215-228, 1964.
23. Zobell, C.E. and B.F. Brown. Studies on the Chemical Preservation of
Water Samples. Journal of Marine Research, 5 (3): 178-182, 1976.
24. Hellwig, D.H.R. Preservation of Waste Water Samples. Water Research,
1: 79-91, 1976.
25. Van Steendeven, R.A. Parameters Which Influences the Organic Carbon
Determination in Water. Water South Africa, 2 (4): 156-159, 1976.
26. Hydes, D.J. and P.S. Liss. Fluorimetric Method for the Determination
of Low Concentrations of Dissolved Aluminum in Natural Waters.
Analyst, 101: 922-931, December, 1976.
27. Dale, T. and A. Henricksen. Intercalibration Methods for Chemical
Analysis of Water. Vatten, (1): 91-93, 1975.
28. Struempler, A.W. Adsorption Characteristics of Silver, Lead, Cadmium,
Zinc, and Nickel on Borosilicate Glass, Polyethylene and Polypropylene
Container Surfaces. Analytical Chemistry, 45 (13): 2251-2254, 1972.
29. Feldman, C. Preservation of Dilute Mercury Solutions. Analytical
Chemistry. 31: 99-102, July, 1974.
30. Clement, J.L. Preservation and Storage of Water Samples for Trace
Element Determination. Department of Civil Engineering, University of
Illinois, Urbana, Illinois, 1972. 40 pp.
31. Henricksen, A. and Balmer. Sampling, Preservation a'nd Storage of
Water Samples for Analysis of Metals. Vatten: (1): 33-38, 1977.
32. Dahl, I. Intercalibration of Methods for Chemical Analysis of Water.
Vatten. (4): 336-340, 1973.
33. Klingaman, E.D.M. and D.V. Nelson. Evaluation of Methods for
Preserving the Levels of Soluble Inorganic Phosphorus and Nitrogen in
Unfiltered Water Samples. Journal Environmental Quality, 5 (1):
42-46, 1976.
34'. Dahl, I. Intercalibration of Methods for Chemical Analysis of Water.
Vatten (2): 180-186, 1974.
399
-------
35. Prakasam, T.B.S. Effects of Various Preservation Techniques on the
Nitrogen Profile of Treated and Raw Poultry Waste. Draft Copy, 1975.
36. Howe, L.H. and C.W. Holley. Comparison of Mercury (II) Chloride
and Sulfuric Acid as Preservatives for Nitrogen Forms in Water Samples,
Environmental Science and Technology, 3 (5): 478-481, May, 1969.
37. Nelson, D.W. and M.J.M. Roomkens. Suitability of Freezing as a
Method of Preserving Run Off Samples for Analysis of Soluble Phosphate.
Journal Environmental Quality, 1 (3;): 323-324, 1972.
38. Gilmartin, M. Changes in Inorganic Phosphate Concentration Occurring
During Seawaste Sample Storage. Limnology and Oceanography, 12:
325-328, 1967.
39, Bay!is, J.E. Procedure for Making Quantitative Phenol Determinations.
Water Wastes and Sewage, 79: 341, 1932.
40. Gibb, R.R. Contamination by Oceanographic Samplers. Analytical
Methods in Oceanography, Advances in Chemistry Series 147, American
Chemical Society, 1975. i
400
-------
APPENDIX A - POPULATION PARAMETERS
I. Populations and Samples (1)(3)
Most sampling is done on a non-continuous basis, and so the data
gathered give an incomplete picture of the true condition, of a water or
wastewater. If monitoring were done continuously, the data would be
presented as a curve (f(t), where f is the function which gives the
value of the parameter at time t) rather than as a discrete set of
points (numbers). Therefore, the definitions of mean and variance given
in Section 4.1.1 could not be applied. This continuous function defines
a "population" from which samples are taken. This population has a mean
and a variance of which the sample mean and sample variance (which are
the mean and variance defined in Section 4.1.1) are only estimators.
This is why it is best to take as many samples as possible — more data
reveals more information about the population.
The Popu1 at i on Mean
The population mean, y , is defined by:
X
*JX = E(X) = /~xfx(x) dx, where E(X) is
another expression for the mean and is read "the expected value (or
expectation) of X".
f«(x) is the density function of x, which is a function defining
the distribution of X.
The Population Variance
2
The variance a , of the population is defined by:
02 = Var (X) = E (U-jux)2 ) =/ (x-»K)2 fx(x)
dx
As with the sample standard deviation, the population standard
deviation is just the square root of the population variance
T
401
-------
APPENDIX B
Areas Under the Normal Curve (1)(3)
The graph of the probability density function of the standard
normal distribution:
2
fv(x) - 1 exp (~x /2), is shown in Figure 4.6.
It is the familiar bell -shaped curve. For any point z, the area under
the curve to the left of z is determined by
/zfv(t)dt, which has been seen to be P(Z 1 z), where 2Nl(0,l).
— 03 A
It is also known that the area to the right of z is P(Z > z). The
normal distribution is symmetric about its mean, and so P(Z > p + c) =
P{Z < jj - c) for any constant c, which in the case of the standard
normal distribution, in which the mean is zero, reduces to P(Z > c)=
P(Z < -c).
There is a property of probabilities which says thats under certain
conditions which are not discussed here, P(Z > c or Z < -c) = P(Z > c)+
P(Z < -c) = 2P(Z > c) and so if P(Z > c or Z < -c) = 2 a then P(Z > c)
= a , which is the area of the shaded region in Figure 4.8 .
402
-------
-------
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Environmental Protection
Agency
center-ior tnuiruirrnetua! iesean,->i
Information
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