United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EMB Report 86-CCT-4
October 1986
Air
NESHAP —
Cooling Towers
Chromium
Emission Test
Report
National Bureau
Of Standards
Gaithersburg,
Maryland
-------
EMISSION TEST REPORT
NATIONAL BUREAU OF STANDARDS
STEAM AND WATER CHILL PLANT
GAITHERSBURG. MARYLAND
ESED 85/02
EMB NO. 86-CCT-U
Prepared By
Entropy Environmentalists, Inc.
Post Office Box 12291
Research Triangle Park, North Carolina 27709
Contract No. 68-02-4336
Work Assignment Nos. 3 and
PNS: 3503 and 3505
EPA Task Manager
Dan Bivins
U.S. Environmental Protection Agency
Emission Measurement Branch
Emission Standards and Engineering Division
Research Triangle Park, North Carolina 27711
October 1986
-------
TABLE OF CONTENTS
Section
1.0 INTRODUCTION 1-1
2.0 PROCESS OPERATION 2-1
2.1 Process Description 2-1
2.2 Process Conditions During Testing 2-3
3.0 SUMMARY OF RESULTS 3~1
3.1 Hexavalent Chromium and Total Chromium Emissions 3-3
3.1.1 Flue Gas Conditions and Isokinetic Sampling Rate 3-i*
3.1.2 Hexavalent Chromium Emissions . 3~7
3.1.3 Total Chromium Emissions 3"7
3.2 Size Distribution of Drift and Chromium 3-8
3.2.1 Size Distribution of Drift 3-8
3.2.2 Size Distribution of Chromium 3~8
3-3 Summary of Analytical Results for Hexavalent Chromium 3~10
and Total Chromium
3.3.1 Cooling Water Samples 3-10
3-3-2 Impinger Train Samples 3-1^
3.3.3 Absorbent Papers 3~17
3- 3-4 Blanks and Quality Assurance Samples 3"17
3-4 Absorbent Paper Sampling 3"17
3-5 Drift Rate Determination 3~l8
4.0 SAMPLING LOCATIONS AND TEST METHODS 4-1
4.1 Cooling Tower Cell Stack Outlets (Sampling Locations
A, B, C, and D) 4-1
4.2 Recirculating Water Pipe (Sampling Location E) 4-6
4-3 Water Trough (Sampling Location F) 4-6
4.4 Ambient Meteorological Station 4-6
4.5 Velocity and Gas Temperature 4-6
4.6 Molecular Weight 4-7
4.7 Chromium Collected by Impinger Trains 4-7
ii
-------
TABLE OF CONTENTS (continued)
4.8 Chromium In Cooling Water 4-8
4.9 Drift Sizing Using Aligned Nozzle and Disc Trains 4-8
4.10 Sensitive Paper Testing 4-10
4.11 Absorbent Paper Testing 4-10
5.0 QUALITY ASSURANCE 5'1
APPENDICES
A TEST RESULTS AND EXAMPLE CALCULATIONS A-l
Hexavalent and Total Chromium A~3
Particle Size for Hexavalent and Total Chromium A-19
ESC Water Flow and Sensitive Paper Data A-35
Hexavalent Chromium Emissions in Milligrams per Million Btu's
and Micrograms per Gallon of Water Flow A-47
Cooling Tower Drop Sizing Train Results A-48
Example Calculations A-50
B FIELD AND ANALYTICAL DATA B-l
Impinger Train Field Data B-3
Particle Size Distribution Field Data NZ-DI Runs B-13
Sample Inventory B-20
Hexavalent and GFAA Chromium Analysis B-23
NAA Chromium Analysis B-40
C SAMPLING AND ANALYTICAL PROCEDURES C-l
Draft Propeller Anemometer Method C-3
Draft Cooling Tower Method C-ll
ESC Measurements C-42
Particle Sizing ("Disc" and "Aligned Nozzle") C-51
D CALIBRATION AND QUALITY ASSURANCE DATA D-l
E MRI PROCESS DATA E-l
F TEST PARTICIPANTS AND OBSERVERS F-l
111
-------
LIST OF FIGURES
Figure No.
2.1 Cooling Tower at NBS Facility in Gaithersburg, Maryland 2-2
4.1 Sketch of NBS Cooling Tower Near Building No. 302,
Showing Riser Pipe, Distribution Manifold, Water
Troughs, and Sampling Locations 4-2
4.2 Cutaway View of Fan Cell Stack on Cooling Tower Adjacent
to Building No. 302 at NBS, Showing Equipment Locations
and Nozzle Traverse Plane 4-5
4.3 Flow Chart for Analysis of Cooling Water Samples 4-9
IV
-------
LIST OF TABLES
Table No. Page
2.1 Summary of Operating Parameters and Meteorological Data
During Tests 2-5
3.1 Testing Schedule for Steam and Chill Plant Cooling
Tower at National Bureau of Standards 3~2
3-2 Summary of Flue Gas Conditions 3~5
3-3 Summary of Hexavalent and Total Chromium Emissions
Based On Graphite Furnace Atomic Absorption (GFAA) 3-6
3.4 Summary of Sensitive Paper (SP) Drift Size Data 3~9
3.5 Summary of Particle Sizing Data Using Disc Train and
Absorbent Paper 3~H
3.6 Summary of Analytical Results for Cooling Water Samples 3-13
3-7 Mineral Content and pH of Selected Cooling Water Samples 3-12
3.8 Summary of Analytical Results for Chromium 3-15
3-9 Sample Train (Impinger) Collection Efficiency 3~l4
3.10 Comparison of Measurement Methods for Total Chromium
Emissions 3~19
3.11 Comparison of Measurement Methods for Drift Rates 3-21
4.1 Sampling Plan for Cooling Tower Adjacent to
Building 302, NBS, Gaithersburg, Maryland 4-3
5.1 Meter Box Calibration Audit 5-2
5-2 Audit Report Chromium Analysis 5~3
5-3 Audit Report Bromide Analysis 5-4
-------
1.0 INTRODUCTION
During the week of August 18, 1986, Entropy Environmentalists, Inc.
(Entropy), under contract to the U. S. Environmental Protection Agency,
Emission Measurement Branch, conducted an emission measurement program at the
National Bureau of Standard's (NBS) Steam and Water Chill Plant in
Gaithersburg, Maryland. The purpose of the measurement program was to provide
data on chromium emissions from cooling towers in support of a possible
chromium standard under the National Emission Standards for Hazardous Air
Pollutants (NESHAPS).
Comprehensive testing was conducted on the cooling tower located adjacent
to Building 302 of the NBS Steam and Water Chill Plant. This cooling tower was
selected for source testing for the following reasons:
• The cooling tower is equipped with a high-efficiency Munters D-15
drift eliminator.
« The facility allowed the addition of chromate-based water treatment
compounds to the cooling tower water. The target level for chromate in
the cooling water is 15 to 20 parts per million (mg/L); it is added as
sodium dichromate. The analysis of the cooling tower water samples
collected during the testing program indicated the target level was
being maintained.
« The facility also allowed the addition of sodium bromide (NaBr) to the
cooling tower water for further evaluation of bromide as a surrogate
compound for cooling tower drift emissions testing.
« The cooling tower construction allows good access to the four outlet
cell stacks and the stack design permits unobstructed sampling
traverses.
o The facility was operating the cooling tower at close to maximum
capacity heat loads during the testing program.
The cooling tower emissions were characterized using a Method 13-type
impinger train following the draft cooling tower test method (Appendix C) to
1-1
-------
collect the drift from the cooling tower exhaust. The impinger contents were
analyzed by Research Triangle Institute (RTI) for total chromium content by
solubilizing the chromium with nitric acid and using graphite furnace atomic
absorbtion (GFAA). The velocity of the airflow through each fan cell was
determined using a propeller anemometer following the draft method (Appendix
C). The gas temperature and percent moisture were also determined. The
corresponding cooling water samples collected during each sampling run were
analyzed by RTI for hexavalent chromium using the diphenylcarbazide wet
chemical method and by North Carolina State University (NCSU) for total
chromium in the filtered residue using Neutron Activation Analysis (NAA).
Sampling was also conducted using an "aligned nozzle train" and a "disc train"
(see Chapter 4), to determine the percentage of chromium emissions associated
with drift particles smaller than a certain particle size (approximately 15
urn).
An independent determination of the drift rate and drift size distribution
was conducted by personnel from Environmental Systems Corporation (ESC) using
their Sensitive Paper (SP) system and microscopic analysis. ESC personnel also
conducted the water flow measurements in the recirculating water pipe serving
the four riser cells. For this, ESC used calibrated pitot tubes and a
methodology similar to EPA Methods 1 and 2 for air velocity measurements.
A sampling protocol using absorbent paper (AP) in a sensitive paper holder
was evaluated as part of an effort to develop a potential screening technique
for cooling tower emission testing and to determine the percentage of chromium
emissions associated with particles greater than a certain particle size
(approximately 30 urn). These AP's were analyzed for total chromium content by
NCSU using NAA.
Mr. David Randall and Mr. Rodney Gibson of Midwest Research Institute (MRI)
monitored the operating conditions of the cooling tower and determined when
1-2
-------
conditions were suitable for sampling. Mr. Dan Bivins (EPA Task Manager) and
Mr. Ed McCarley of the Emission Measurement Branch (EMB) were present to
observe the testing program. Mr. Robert Moore of NBS served as the contact for
the facility.
This report is organized into several sections that address the various
aspects of the testing program. Immediately following this introduction is the
"Process Operation" section describing the process involving the cooling tower
tested, the cooling tower system, and the control equipment in the tower.
Following the "Process Operation" section is the "Summary of Results" section
presenting tables summarizing the test conditions, the calculated emission and
drift rates, the drift size distribution, and the analytical results. The next
section, "Sampling Locations and Test Methods" describes and illustrates the
various sampling locations for the emissions testing program and then explains
the sampling strategies used. The final section, "Quality Assurance",
describes the procedures used to ensure the integrity of the sampling and
analysis program. The Appendices present the Test Results and Example
Calculations (Appendix A); Field and Analytical Data (Appendix B); Sampling and
Analytical Procedures (Appendix C); Calibration and Quality Assurance (Appendix
D); MRI Process Data (Appendix E); and Test Participants and Observers
(Appendix F).
1-3
-------
2.0 PROCESS OPERATION
2.1 PROCESS DESCRIPTION
The NBS is a Federal government research facility near Gaithersburg,
Maryland. On the grounds are seven laboratory/office buildings with a total
2
floor area of 625,000 square feet (ft ). There are also a number of support
buildings that add another 675.000 feet. Comfort cooling and cooling for
laboratory processes (lasers, ovens, etc.) are both provided by a U-cell Marley
tower located near the western boundary of the facility. The tower was
installed in the early 1960's.
A sketch of the cooling tower system is provided in Figure 2.1. The tower
is a crossflow design with redwood splash fill and one fan per cell. Propeller
fans measuring 22 feet (ft) in diameter are located in the stack of each cell.
Last year, the tower was retrofitted with high-efficiency Munters D-15 drift
eliminators.
The capacity of the water basin is about 500,000 gallons (gal). Four
pumps, each rated for 8,800 gal/min circulate the water to the chillers. The
water from the chillers is combined and returned to"the tower through a 42-
inch riser pump. Above the tower, the flow is split into four branches and
distributed to each of the cells. The water distribution decks are located
directly above the fill and are equipped with gravity flow nozzles. In winter,
heated water is sprayed up into the rear of the tower to prevent icing
conditions.
A solution of molybdate and polyacrylate is used to inhibit corrosion in
the heat exchangers. The target concentration of molybdate in the
2-1
-------
HOT WATER SPRAY TO BASE OF TOWER
I
ro
(WINTER USE)
BLOWDOHN
RECIRCULATING
UATER TO
DISTRIBUTION
DECK
!
_._.!
<- —
COOLED WATER
FROM TOWER
BASIN TO CHILLERS
PUHP
FAN STACK
DISTRIBUTION
DECK
MAKEUP TO TOWER
BASIN (CITY HATER)
Figure 2-1. Cooling tower at NBS Facility in Gaithersburg. Maryland.
-------
recirculating water is about 15 parts per million. Conductivity and pH are
monitored continuously, and blowdown occurs automatically when the conductivity
reaches 1,800 umhos. Blowdown averages about 60,000 gallons per day (gal/day)
in summer and about 2,000 gal/day in winter.
Makeup water is provided by the City of Gaithersburg. The conductivity is
generally about 300 umhos, but after heavy rains and after salt has been
applied to the roads in the winter, the conductivity increases. Makeup
requirements in summer average about 300,000 gal/day, and in winter average
about 55,000 gal/day. Most of the water has first been used for once-through
cooling of oil and air compressors.
Biological growth is controlled by manually adding 6.5 gal of a solution
containing disodium cyanodithiodocarbonate (7-35 percent) and potassium
methyldithiocarbonate (10.15 percent) once a week.
2.2 PROCESS CONDITIONS DURING TESTING
Eight test series were conducted Tuesday through Friday, August 19-22,
1986. The cooling tower operating parameters that were monitored during each
test'series to ensure that acceptable conditions existed included the
recirculating water temperatures into and out of the chiller, recirculating
water flow rate, daily blowdown and water makeup, wind speed, and wind
direction. Meteorological data were also obtained from the National Weather
Service (NWS) at Washington National Airport. This NWS Station is the one
closest to NBS.
The design water flow was achieved on each of the test days, but one
chiller was not operated; water simply circulated through it. The low ambient
temperature and low demand all day on August 21 and early in the morning on
August 22 necessitated turning off a second chiller and one fan. Table 2.1 is
2-3
-------
TABLE 2.1. SUMMARY OF OPERATING PARAMETERS AND METEOROLOGICAL DATA DURING TESTS
N)
-P-
Parameter
Date
Rec 1 rcu 1 at 1 ng
water flow In
riser, gal/mlna
Fans
Slowdown, gal /day
Makeup, gal /day
Chi 1 lers
Water temperature.
•F
Entering
condenser, avg.
Leaving
condenser, avg.
Water chemistry
pH
Conductivity,
umhos
Bloclde
addition, gal
Meteorological data
Wind speed, mph
Wind direction
(00-360)
Test series
No. 1
8-19-86
36,108
Al 1 4 high
93,400
336,600
3 on, 1 off
75-78
81-85
—
1,700
0
0-5
0-75
Test series
No. 2
8-19-86
36,108
All 4 high
93,400
336,600
3 on, 1 off
79-80
85-86
—
1,700
0
0-6
15-90
Test series
No. 3
8-20-86
36,428
Al 1 4 high
50,200
254,400
3 on, 1 off
77-78
83-84
—
1,700
6.5
0-14
45-90
Test series
No. 4
8-20-86
36,428
Al 1 4 high
50,200
254,400
3 on, 1 off
78-79
84-85
—
1,700
6.5
0-1 1
90-105
Test series
No. 5
8-21-86
36,383
3 high.
1 off
31,800
201.00
2 on, 2 off
75-77
80-82
—
1 ,700
0
0-5
0
Test series
No. 6
8-21-86
36,383
3 high.
1 off
31,800
201 ,000
2 on, 2 off
77-78
82-83
—
1,700
0
0-5
0-90
Test series
No. 7
8-22-86
35,761
Al 1 4 high
45,200
162,500
2 on, 2 off
for 1 h
3 on, 1 off
for 1 h
73-75
77-81
8.5
1,750
0
0-11
270-360
Test series
No. 8
8-22-86
35,761
All 4 high
45,200
162,500
3 on, 1 off
75-76
81-82
8.6
1,750
0
0-5
270-360
aAs measured by ESC personnel.
-------
a summary of the cooling tower operating parameters and meteorological data
recorded during the test period.
Crystalline sodium dichromate was added to the recirculating water -(200
pounds on Monday, August 18, and lesser amounts on the following days). The
concentration in the water was not determined during the testing and daily
variations may have resulted. Sodium bromide also was added to the
recirculating water for evaluation of bromide as a surrogate for chromium in
drift emissions testing.
A pretest walk-through of the tower was conducted on Tuesday, August 19.
Inspection of the drift eliminators revealed a number of water leaks into the
fan side of the eliminator sections. This was most significant in the first
cell, but in no case did the airflow appear to be shearing droplets away from
the water stream. Inspection of the water flow along the outside of the tower
revealed an unequal distribution that was most pronounced on the windiest
days. The strongest winds were evident on Wednesday, August 20 when the
anemometer mounted atop a nearby building indicated gusts of up to 14 miles per
hour (mph). On the tower itself, an anemometer indicated 14 mph and the NWS
reported winds of 10 to 15 mph for that day. In no instance, however, was
drift observed from the sides of the tower. All tests were completed under
acceptable conditions with respect to the test plan and Cooling Tower Institute
guidelines.
2-5
-------
3.0 SUMMARY OF RESULTS
Tests were conducted to determine the mass emission rates of hexavalent
chromium and total chromium from the Steam and Chill Plant cooling tower at the
National Bureau of Standards (NBS) in Gaithersburg, Maryland. The mass
emission rate tests involved using a Method 13-type impinger train to sample
four fan stacks on four riser cells equipped with high-efficiency drift
eliminators. The testing schedule that was followed for the NBS cooling tower
is presented in Table 3.1; The results of these tests are discussed briefly
below and in detail in Section 3.1.
The pollutant mass rate for hexavalent chromium, calculated by the ratio of
areas (PMRQ) method, for the four riser cells equipped with high-efficiency
drift eliminators averaged 1,342 milligrams per hour (mg/hr).
The drift size distribution (drift being defined here as cooling water
entrained in the exit air and emitted to the atmosphere in droplet form), along
with the drift rate, was determined by Environmental Systems Corporation (ESC)
using their sensitive paper (SP) "technique. The results of the SP testing
suggest that the drift emissions from the fan cells equipped with high-
efficiency drift eliminators had an average mass mean diameter of 377 urn.
Another method was evaluated for determining the percentage of the mass of
hexavalent chromium associated with particles smaller than a certain size
(approximately 15 urn under these sampling conditions). The sampling protocol
involved using a set of paired trains; one, referred to as the "disc train,"
was designed to capture only the smaller particles and the other, a Method
13-type train with the nozzle aligned directly into the flow of the fan exhaust
3-1
-------
TABLE 3.1. TESTING SCHEDULE FOR STEAM AND CHILL PLANT COOLING TOWER
AT NATIONAL BUREAU OF STANDARDS. GAITHERSBURG, MARYLAND
Date
(1986)
8/19
8/20
8/21
8/22
Sample Type
-
Chromium
Chromium
Particle size
Particle size
Chromium
Chromium
Particle size
Particle size
Chromium
Chromium
Particle size
Particle size
Chromium
Chromium
Particle size
Particle size
Riser Cell A
Run
No.*
A-l
A-2
DI-A-1
NZ-A-1
Test Time
24 h clock
09:59-12:15
12:47-14:49
10:10-14:23
10:10-14:23
Riser Cell B
Run
No.*
B-l
B-2
DI-B-2
NZ-B-2
Test Time
24 h clock
09:45-11:48
12:10-14:13
10:10-14:24
10:10-14:24
Riser Cell C
Run
No.*
C-l
C-2
DI-C-3
NA-C-3
Test Time
24 h clock
09:19-11:22
11:43-13:46
09:40-13:40
09:40-13:40
Riser Cell D
Run
No.*
D-l
D-2
DI-D-4
NZ-D-4
Test Time
24 h clock
09:23-11:48
12:05-14:08
09:25-13:30
09:25-13:30
*Run numbers for chromium runs indicate: Riser Cell - Run.
Run numbers for particule size runs indicate: Technique - Riser Cell - Run.
3-2
-------
(referred to as the "aligned nozzle train"), was designed to capture all sizes
of drift particles. Data from a screening technique being evaluated utilizing
absorbent paper (AP), was also used for particle sizing purposes. The data
were used based on collection by the AP in a sensitive paper holder of parti-
cles over 30 urn (under these sampling conditions).
The paired train particle sizing data suggest that most of the hexavalent
chromium emissions from the four fan cells equipped with high-efficiency drift
eliminators are associated with particles less than 15 urn. The AP data for the
four cells suggest that only 2.9 to 8.9 percent of the chromium emissions are
associated with particles greater than 30 urn. The particle sizing results and
the differences between the two methods are discussed in detail in Section 3.2.
The analytical results for hexavalent chromium and residue chromium for
cooling water samples and the total chromium in the impinger samples are
presented in Section 3-3 along with the analytical results of the blanks and
quality assurance samples. The results of the analysis of the absorbent
papers, which are being evaluated as a screening technique for cooling tower
emissions, are also presented in Section 3.3, and the technique is discussed in
Section 3.4.
Drift rate calculations based on the water flow to the riser cells, the
concentration of chromium in the cooling water, and the mass emission rates
calculated for the impinger train samples and the AP samples are presented in
Section 3-5- Drift rate calculations from the SP data are also presented and
the drift rates calclulated by the various methods are compared.
3.1 HEXAVALENT CHROMIUM AND TOTAL CHROMIUM EMISSIONS
The mass emission rates for hexavalent chromium and total chromium from the
four riser cells equipped with high-efficiency drift eliminators were determined.
3-3
-------
Sampling was conducted isokinetically with the isokinetic values for the eight
sampling runs, ranging from 99.2% to 101.9% (see Table 3-2). The sampling runs
were typically 2 hours in length, with a single traverse on each fan stack cell
comprising a single sample.
The hexavalent chromium emissions in the drift were calculated using the
values for the total chromium emissions and the ratio of hexavalent-to-total
chromium in the cooling water. The assumption was made that the chromium
emissions from the cooling tower fan stack maintained the same ratio of hexava-
lent- to- total chromium as measured in the cooling water.
The concentration of hexavalent and total chromium in milligrams per dry
standard cubic meter (mg/dscm), in micrograms per gallon of water flow to the fan
cell (ug/gal), and in milligrams per million Btu's of heat removed (mg/10 Btu),
and the mass emission rates of hexavalent and total chromium, in milligrams per
hour (mg/hr) are presented in Table 3-3 for each sampling run. These results are
based on the total chromium analysis conducted by RTI using GFAA with the
hexavalent chromium values being calculated using the ratio of
hexavalent-to-total chromium in the cooling water sample for that run. The
hexavalent and total chromium values are representative of the emissions from a
single fan stack on the corresponding fan cell. The mass emission rates were
calculated using the ratio of the fan stack area to the sampling nozzle area, the
catch weight of total chromium, the calculated catch weight of hexavalent
chromium, and the sampling time (see Appendix A for example calculations).
3-1.1 Flue Gas Conditions and Isokinetic Sampling Rate
A summary of the flue gas conditions for the fan cells tested is presented in
Table 3.2. The volumetric flow rates were fairly constant on all the fan cells
tested. For fan cell A, the volumetric flowrate averaged 1,121,000 actual cubic
3-4
-------
TABLE 3.2. SUMMARY OF FLUE GAS CONDITIONS
Run
No.
Date
(1986)
Test Time
24 h clock
Volumetric Flow Rate
Actual
acmh
6
x 10
acfh
xlO6
D
Standard
dscmh
xlO6
dscfh
xlO6
Stack
Temoe
0
C
rature
o
F
Moisture
%
Isokinetic
%
Riser Cell A
A-l
A-2
8/19
8/19
9:59-12:15
12:47-14:49
Average
1.121
1.121
1.121
39.58
39.58
39.58
1.062
1.054
1.058
37.50
37.23
37.37
27
28
27
80
82
81
3.4
3.7
3.5
101.0
101.9
101.5
Riser Cell B
B-l
B-2
8/20
8/20
9:45-11:48
12:10-14:13
Average
1.254
1.308
1.281
44.28
46.18
45.23
1.201
1.244
1.223
42.41
43.92
43.16
25
26
26
77
79
78
3.1
3.4
3.2
100.5
100.1
100.3
Riser Cell C
C-l
C-2
8/21
8/21
9:19-11:22
11:43-13:46
Average
1.163
1.161
1.162
41.06
40.98
41.02
1.117
1.116
1.117
39.46
39.42
39.44
24
24
24
76
76
76
3.0
3.0
3.0
99.4
99.2
99.3
Riser Cell D
D-l
D-2
8/22
8/22
9:23-11:48
12:05-14:08
Average
1.241
1.212
1.227
43.82
42.79
43.81
1.196
1.162
1.179
42.22
41.02
41.62
25
26
25
76
78
77
3.0
3.2
3.1
98.8
99.6
99.2
3-5
-------
TABLE 3.3. SUMMARY OF HEXAVALENT AND TOTAL CHROMIUM EMISSIONS BASED
ON GRAPHITE FURNACE ATOMIC ABSORPTION (GFAA)
Run
No.
Date
Hexavalent Chromium
concentration
_3
(mg/dscm) x 10 ^
ug/gal
mg/10 Btu
mass emissions
mg/hr
Total Chromium
concentration
_7
(mg/dscm) x 10
ug/gal
mg/10 Btu
mass emissions
mg/hr
Riser Cell A, High-Efficiency Drift Eliminators
A-l
A-2
8/19
8/19
Average
0.606
4.20?
2.406
1.20
8.35
1.78
4.88
34.61
19.75
650
4521
2586
0.606
4.208
2.407
1.20
8.35
4.78
4.88
34.61
19.75
650
4521
2586
Riser Cell B, High-Efficiency Drift Eliminators
B-l
B-2
8/20
8/20
Average
0.575
0.285
0.430
1.27
0.65
0.96
4.46
2.51
3-49
694
355
524
0.576
0.285
0.431
1.27
0.65
0.96
4.47
2.51
3-49
695
355
525
UJ
Riser Cell C, High-Efficiency Drift Eliminators
C-l
C-2
8/21
8/21
Average
0.568
2.647
1.608
1.16
5.37
3.26
5.21
25.17
15.19
631
2930
1780
0.569
2.649
1.609
1.16
5-38
3-27
5.22
25.19
15.21
632
2932
1782
Riser Cell D, High-Efficiency Drift Eliminators
D-l
D-2
8/22
8/22
Average
0.375
0.448
0.412
0.83
0.97
0.90
3.40
3.77
3-59
443
518
480
0.375
0.448
0.412
0.87
0.97
0.92
3.40
3-78
3-59
443
519
481
-------
meters per hour (39,580,000 actual cubic feet per hour), for fan cell B it
averaged 1,281,000 actual cubic meters per hour (45,230,000 actual cubic feet per
hour), for fan cell C, it averaged 1,162,000 actual cubic meters per hour
(41,020,000 actual cubic feet per hour), and for fan cell D, it averaged
1,227,000 actual cubic meters per hour (43,810,000 actual cubic feet per hour).
The stack temperature averaged 27°C (8l°F), 26°C (78°F). 24°C (76°F), and 25°C
(77 F) for fan cells A, B, C, and D, respectively. The moisture content averaged
3-5%, 3-2%, 3-0%, and 3-1% for fan cells A, B, C, and D, respectively. The
isokinetic sampling rates were well within the allowable limits for all eight
runs.
3.1.2 Hexavalent Chromium Emissions
The emission concentrations and the mass emission rates for hexavalent
chromium for the test runs on the four fan cells are presented in Table 3.3. The
hexavalent chromium concentrations for fan cells A, B, C, and D averaged 0.0024,
0.0004, 0.0016, and 0.0004 milligrams per dry standard cubic meter of exhaust
gas; 4.78, 0.96, 3-26, and 0.90 micrograms per gallon of water flow to the fan
cells; and 19.75, 3^9, 15-19, and 3-59 milligrams per million Btu's of heat
removed; respectively. The mass emission rates of hexavalent chromium for fan
cells A, B, C, and D averaged 2586, 524, 1780, and 480, respectively.
3.1.3 Total Chromium Emissions
The emission concentrations and the mass emission rates for total chromium
are also presented in Table 3-3. The total chromium concentrations averaged
0.0024, 0.0004, 0.0016, and 0.0004 milligrams per dry standard cubic meter of
exhaust gas; 4.78, 0.96, 3-27, and 0.92 micrograms per gallon of water flow to
the fan cells; and 19-8, 3-45. 15-2, and 3.6 milligrams per million Btu's of heat
removed for fan cells A, B, C, and D, respectively.
3-7
-------
3.2 SIZE DISTRIBUTION OF DRIFT AND CHROMIUM
3.2.1 Size Distribution of Drift
The drift size distribution, as well as the drift rate, was measured by ESC,
using their sensitive paper (SP) technique, for each fan cell tested by Entropy.
The total flux, the mean particle diameter for mass and particle count, the mass
emission rate, and a drift rate expressed as a percent of water flow to the fan
cell are presented in Table 3-^ for the four fan cells. " The drift rates calcu-
lated using the SP data as a percent of water flow ranged from O.OOOl/K to
0.0004Z.
The mass mean diameter of the drift is that particle diameter at which half
the drift mass is composed of particles with diameters larger than the mean
diameter and half the mass is composed of particles with diameters smaller than
the mean diameter. For the four riser cells, the mass mean diameter for the
drift particles ranged from 3^8 to 40? micrometers (urn) and averaged 377 urn.
3.2.2 Size Distribution of Chromium
Two methods were used for estimating the percent of hexavalent chromium in
two particle size ranges. The first method involved the use of paired trains
with an "aligned nozzle train" and a "disc train" (described in Section 4.9).
The aligned nozzle train, which was used as a reference measurement, was designed
to collect all particle sizes isokinetically. The disc train was operated at the
same sampling rate as the nozzle train and was designed to collect primarily the
smaller particles (less than about 15 urn). The purpose of the paired train
particle sizing was to determine the percent of the chromium emissions associated
with the smaller particles.
The second method used for particle sizing, the absorbent paper (AP)
technique, was, in addition, being evaluated as a screening method for cooling
tower testing. Southern Research Institute's (SoRI) Aerosol Science Division
3-8
-------
TABLE 3.4. SUMMARY OF SENSITIVE PAPER (SP) DRIFT SIZE DATA
Date
Total Flux
2 **** 6
(ug/m /sec) x 10
count
(#/m /sec) x 10
Mean Diameter
mass
urn
count
urn
Mass Emission
Rate
grams/sec
Water
Flow*
gpm
Drift
Rate
%
Riser Cell A
8/19
0.031
1.83
407
56
1.17
9027
0.0002
Riser Cell B
8/20
0.067
1.97
348
79
2.49
9095
0.0004
Riser Cell C
8/21
0.020
7.04
355
37
0.758
9094
0.0001
Riser Cell D
8/22
0.016
1.76
397
39
0.584
8939
0 . 0001
Average
0.034
3.15
377
53
1.251
9039
0.0002
*Water Clow to individual risers calculated by dividing total water Clow to tower by four.
3-9
-------
calculated the cut sizes for both particle sizing methods. Using the fan cell
gas velocity and the inside diameter of the disc train probe, SoRI calculated
the diameter of particles collected at 50 percent efficiency (D ) by the disc
train. The D Q for the disc train runs ranged from 13.1 to 14.9 urn (see
Appendices A and C) with particles less than this size range being collected.
The D 0 for the AP sampling device, which collected primarily larger particles
(i.e., 30 urn and up), ranged from 25.1 to 28.5 urn with particles larger than
this size range being collected.
The ratio of the emission rates of hexavalent chromium measured by the
paired trains for runs 1, 2, 3, and 4 for fan cells A, B, C, and D, respec-
tively, are shown in Table 3.5. With to the nozzle train collection value used
as the reference, the disc train collected over 100% of the hexavalent
chromium. This suggests that most or all of the chromium emissions from the
fan cells equipped with high-efficiency drift eliminators are associated with
particles less than 15 urn.
The second particle sizing method involved using the AP device attached to
the traversing impinger train. The percent of chromium associated with
particles greater than the 30 urn cut size was calculated using the ratio of the
PMR& values for the AP device and the corresponding impinger (IMP) train run
values (see Table 3-5). The ratio of the AP to impinger train values ranged
from 2.9% to 8.92 for the four fan cells. This suggests that only a small
portion of the chromium emissions are associated with particles larger than 30
urn.
3-3 SUMMARY OF ANALYTICAL RESULTS FOR HEXAVALENT CHROMIUM AND TOTAL CHROMIUM
3-3-1 Cooling Hater Samples
Two analytical techniques (see Figure 4.3) were used for the analysis of
hexavalent chromium and total chromium in the cooling water samples. A portion
3-10
-------
TABLE 3.5. SUMMARY OF PARTICLE SIZING DATA USING DISC TRAIN AND ABSORBENT PAPER
Run
Number
Hexavalent
Chromium
PMRc
(mg/hr)
Percent
Ratio
of Disc to
Nozzle
Run
Number
Hexavalent
Chromium PMRa
mg/hr
Avg.
Percent
Ratio
of AP to
IMP train
RISER CELL A, HIGH-EFFICIENCY DRIFT ELIMINATORS
DI-A-1
NZ-A-1
809
391
2072
A-l(AP)
A-2(AP)
A-l(IMP)
A-2(IMP)
86.7
62.4
650
A, 521
74.6
2,586
2 92
RISER CELL B, HIGH-EFFICIENCY DRIFT ELIMINATORS
DI-B-2
NZ-B-2
370
253
146*
B-l(AP)
B-2(AP)
B-l(IMP)
B-2(IMP)
18.6
40.7
694
355
29-7
525
5- 72
RISER CELL C, HIGH-EFFICIENCY DRIFT ELIMINATORS
DI-C-3
NZ-C-3
3058
226
13532
C-l(AP)
C-2(AP)
C-l(IMP)
C-2(IMP)
90.7
89.5
631
2,930
90.1
1,781
5-1%
RISER CELL D, HIGH-EFFICIENCY DRIFT ELIMINATORS
DI-D-4
NZ-D-4
742
355
2092
D-l(AP)
D-2(AP)
D-l(IMP)
D-2(IMP)
73-4
12.5
443
518
43.0
481
8.92
3-11
-------
of each cooling water sample was analyzed by RTI for hexavalent chomium using
the diphenylcarbazide colorimetric procedure. Another 10-ml aliquot of each
cooling water sample (approximately 350 ml) was filtered through a Teflon-
filter with a 1.0-um pore size. The filter, which was used to collect the
insoluble trivalent chromium (Cr*-*) residue, was then analyzed for total
chromium by NAA. The sum of the hexavalent chromium (Cr* ) and the residue on
the filter (Cr •*) represents the total chromium content of the cooling water.
The hexavalent chromium results for the diphenylcarbazide analysis of the
cooling water samples presented in Table 3.6 show a range of 16.9 to 18.2
micrograms per milliliter (ug/ml) of hexavalent chromium. The levels of
trivalent chromium determined using NAA shown in Table 3.6 range from <0.0001
to 0.0222 ug/ml. The ratio of hexavalent chromium-to-total chromium (sum of
hexavalent and trivalent chromium) in the cooling water ranged from 0.999 to
1.00 (99-9% to 100.0% hexavalent chromium). The percent hexavalent chromium
value determined for each water sample collected was used to calculate the
hexavalent chromium emissions from the total 'chromium emissions measured by the
impinger train for that corresponding run.
The first and last cooling water samples collected during testing and a
third cooling water sample collected prior to the addition of sodium dichromate
and sodium bromide to the cooling water (NBS-Prespiked) were also analyzed for
calcium (Ca), magnesium (Mg), manganese (Mn), and sodium (Na) content, and pH.
The results of these analyses are presented in Table 3.7.
TABLE 3.7. MINERAL CONTENT AND pH OF SELECTED COOLING WATER SAMPLES
Sample
No.
A-l
D-2
NBS-Prespiked
Cr
ug/ml
17-5
18 >
<0.015
Ca
ug/ml
177
208
203
Mg
ug/ml
48.7
53-9
57.8
Mn
ug/ml
<0.02
<0.02
<0.02
Na
ug/ml
127.
140
130
Cr+6
ug/ml
16.9
17.0
NA
PH
8.15
8.49
8.36
3-12
-------
TABLE 3.6. SUMMARY OF ANALYTICAL RESULTS FOR COOLING WATER SAMPLES
Run
No.
Sample
Type
Sample
No.
Analyzed
Chromium
(ug/ml)
Riser Cell A
A-l -
A-l
A-l
A-2
A-2
A-2
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water. (Total Cr)
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
A-l
A-l-R
A-2
A-2-R
16.90
<0.0001
16.90 *
17-00
0.0004
17-00 *
Riser Cell B
B-l
B-l
B-l
B-2
B-2
B-2
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
B-l
B-l-R
B-2
B-2-R
17-20
0.0222
17-22 *
17.50
0.0130
17-51 *
Riser Cell C
C-l
C-l
C-l
C-2
C-2
C-2
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
C-l
C-l-R
C-2
C-2-R
17-20
0.0082
17-21 *
17.20
0.0091
17.21 *
Riser Cell D
D-l
D-l
D-l
D-2
D-2
D-2
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
Cooling Water (Cr+6)
Cooling Water (Cr+3)
Cooling Water (Total Cr)
D-l
D-l-R
D-2
D-2-R
18.20
0.0053
18.21 *
18.10
0.0153
18.12 *
* This value represents the total chromium content of the cooling water and
is the sum of the hexavalent chromium (Cr+6) measured by the diphenylcarbizide
wet chemical method and the trivalent chromium (Cr+3) which is the chromium
measured by NAA in the filtered residue of the cooling water sample.
3-13
-------
3.3-2 Impinger Train Samples
The analytical results for the samples from each impinger train run and each
paired train particle sizing run are presented in Table 3'8. The impinger-.
train and paired train samples, consisting of the impinger contents and rinses,
the probe rinses, and a filter, were analyzed principally by RTI using graphite
furnace atomic absorption (GFAA). Each result was blank corrected using the
results of a DI water or a DI water/filter blank. The chromium in each sample
was first solubilized using nitric acid so that the GFAA analysis, which measures
only soluble chromium, would yield results for total chromium. A small correc-
tion factor was added to the sample results to account for a prior NAA analysis
of a small aliquot of each sample (see example calculations in Appendix A).
Prior to analysis, each sample was concentrated down in a glass beaker and
then transferred to another container. Each beaker used was then treated with
aqua regia to solubilize any residual chromium remaining after sample transfer.
This aqua regia solution (beaker residue) was also analyzed by GFAA. Thus, the
analytical results presented for total chromium in each impinger sample is the
sum of the total chromium for the sample measured by GFAA (with the NAA
correction factor) and the residual chromium recovered from the sample concen-
tration beakers measured by GFAA (see example calculations in Appendix A).
The collection efficiencies for the sampling train (for runs A-2, C-2, and
PS-DI-4) are presented in Table 3-9. The collection efficiency for runs A-2,
C-2, and PS-DI-4 show 95.92, 92.9# and 85.6%, respectively, of the chromium being
collected in the first and second impingers.
TABLE 3.9. SAMPLE TRAIN (IMPINGER) COLLECTION EFFICIENCY
Date
(1986)
8/19
8/21
8/22
Run
No.
A-2
C-2
PS-DI-4
1st Imp.
Catch, ug
10.3645
5-8704
2.2331
Cumulative
% of Catch
87-1
76.1
41.7
2nd Imp.
Catch , ug
1.0438
1.2993
2.3517
Cumulative
% of Catch
95-9
92.9
85.6
3rd Imp.
Catch, ug
0.4884
0.5453
0.7718
Cumulative
% of Catch
100%
100%
100%
3-14
-------
TABLE 3.8. SUMMARY OF ANALYTICAL RESULTS FOR CHROMIUM
Run
Number
Sample
Number
Sample Type
Sample
Size
Total
Chromium
by NAA
(ug)
Total
Chromium
by GFAA
(ug)
Riser Cell A
A-l
A-l
A-2
A-2
A-2
A-2
A-l-abc
A-l-AP
A-2-a
A-2-b
A-2-c
A-2-AP
Impinger Contents & Filter
Traversing Absorbent Paper
1st Impinger & Probe Rinse
Second Impinger Contents
Third Impinger and Filter
Traversing Absorbent Paper
20. 5103 ml
13.2 sq.cm
22.7763 ml
23.3437 ml
22.6116 ml
13.2 sq.cm
6.103
4.394
1.772
10.365
1.044
0.488
Riser Cell B
B-l
B-l
B-2
B-2
B-l-abc
B-l-AP
B-2-abc
B-2-AP
Impinger Contents & Filter
Traversing Absorbent Paper
Impinger Contents & Filter
Traversing Absorbent Paper
23.1403 ml
1.32 sq.cm
24.3555 ml
1.32 sq.cm
1.309
2.867
1.842
0.934
Riser Cell C
C-l
C-l
C-2
C-2
C-2
C-2
C-l-abc
C-l-AP
C-2-a
C-2-b
C-2-c
C-2-AP
Impinger Contents & Filter
Traversing Absorbent Paper
1st Impinger & Probe Rinse
Second Impinger Contents
Third Impinger and Filter
Traversing Absorbent Paper
21.7093 ml
13.2 sq.cm
19.4799 ml
21.6142 ml
25.8687
13-2 sq.cm
6.386
6-309
1.673
5.870 *
1.299
0.545 *
Riser Cell D
D-l
D-l
D-2
D-2
D-l-abc
D-l-AP
D-2-abc
D-2-AP
Impinger Contents & Filter
Traversing Absorbent Paper
Impinger Contents & Filter
Traversing Absorbent Paper
18.6235 ml
13.2 sq.cm
24.4623 ml
13.2 sq.cm
5-167
0.883
1.173
1.365
Particle Sizing, Riser Cells A, B, C, and D
DI-A-1
DI-A-1
DI-B-2
DI-B-2
DI-C-3
DI-C-3
DI-D-4
DI-D-4
DI-D-4
DI-D-4
DI-D-4
NZ-A-1
NZ-B-2
NZ-C-3
NZ-D-4
PS-DI-1-p
PS-DI-1
PS-DI-2-p
PS-DI-2
PS-DI-3-P
PS-DI-3
PS-DI-4-p
PS-DI-4-a
PS-DI-4-b
PS-DI-4-c
PS-DI-4-f
PS-NZ-1
PS-NZ-2
PS-NZ-3
PS-NZ-4
Disc Train Probe Rinse
Disc Train Imp. & Filter
Disc Train Probe Rinse
Disc Train Imp. & Filter
Disc Train Probe Rinse
Disc Train Imp. & Filter
Disc Train Probe Rinse
Disc Train, First Imp.
Disc Train, Second Imp.
Disc Train, Third Imp.
Disc Train Filter
Nozzle Train Imp. & Filter
Nozzle Train Imp. & Filter
Nozzle Train Imp. & Filter
Nozzle Train Imp. & Filter
18.984 ml
27.637 ml
17.227 ml
26.063 ml
17.467 ml
12.707 ml
17.502 ml
16.508 ml
15.907 ml
17.963 ml
Total
25.888 ml
21.144 ml
16.860 ml
17.090 ml
2.186
2.653
1.301
1.326
21.566
0.602
1.3144
0.9187
2.3517
0.7718
0.000
2.4894
1.9333
1-7775
2.8096
(continued)
3-15
-------
TABLE 3-8 (continued)
Run
Number
Sample
Number
Sample Type
Sample
Size
Total
Chromium
by NAA
(ug)
Total
Chromium
by GFAA
(ug)
Blanks and Quality Assurance Samples
**
**
*«
**
Blank-AP
QA-1
QA-2
QA-3
QA-4
QA-5
Imp. & Filter - Blank Value
Imp. 1 & Rinse - Blank Value
Imp. 2 - Blank Value
Imp. 3 & Filter - Blank Value
Adsorbent Paper Blank
QA Sample 1
QA Sample 2
QA Sample 3
QA Sample 4
QA Sample 5
1.32 sq.cm
1.0 ug Cr
1.0 ug Cr
1.0 ug Cr
0.1 ug/ml Cr
0.1 ug Cr
0.164
0.221
0.551
0.225
0.1
0.1
0.04
0.02
1.0
0.096 ug/ml
0.085
* Values were exchanged to correct for sample mislabelling.
** Blank values calculated from GFAA results for samples: P-42, P-43, Blank-f,
Blank, Blank 1, and Blank 2.
3-16
-------
3-3-3 Absorbent Papers
The analytical results for the absorbent paper measurements are also
presented in Table 3-8. For these samples, the entire 47 mm paper was sub-
mitted directly to NCSU for NAA. The results in Table 3-8 are also blank
corrected using the analytical results for a blank paper (Sample Blank-AP).
3-3-^ Blanks and Quality Assurance Samples
The results of the analyses for the blanks and the quality assurance sam-
ples are also presented in Table 3-8. Blanks for the cooling water analysis
consisted of a DI water blank filtered through a Teflon filter having a 1.0-um
pore size, with the filtrate being collected for analysis. The filter and a
1.0-ml aliquot of the DI water filtrate were submitted separately for analy-
sis. The blanks for the Method 13-type impinger trains and paired particle
sizing trains consisted of a blank Teflon filter identical to the ones used in
the sampling trains and 500 ml of DI water concentrated to approximately
25 milliliters or just 500 ml of DI water concentrated (for collection
efficiency samples). Each analytical result was blank corrected using the
appropriate blank value.
The results of the analyses of the quality assurance samples are also
presented in Table 3-8 and discussed in Section 5.0.
3.4 ABSORBENT PAPER SAMPLING
A sampling protocol using absorbent paper {filter paper) was evaluated as
part of an effort to develop a screening method for cooling tower emission
testing. The absorbent paper, held in a device similar to the SP holder, was
exposed to the rising drift emissions by being attached to the traversing
impinger train. The traversing AP allowed the use of the impinger train
results as a reference to determine the sample collection efficiency of the
3-17
-------
AP's. The AP catch of total chromium was determined by placing the AP directly
into a 2-ml vial and submitting the sample for NAA.
A pollutant emission rate using the ratio of areas calculation (PMR ) for
a
each of the AP tests was calculated using the exposed area of the paper
(exposed diameter of 4l mm). These results are presented in Table 3.10 for
comparison with the PMR 's calculated for the impinger train samples. The PMR
a a
values for the AP's are significantly lower than the PMR 's calculated for the
a
impinger trains. This low bias may be explained by the 30 urn cut size
calculated for the AP device, with only particles greater than 30 urn being
collected, and the association of the majority of the chromium emissions with
particles less than 15 urn (see Section 3.2.2).
The evaluation of this screening method will continue on future cooling
tower tests and a separate report will be produced summarizing the results of
the screening tests. The evaluation of the use of sodium bromide as a
surrogate for cooling tower emission tests will also be discussed in the
screening test summary report.
3-5 DRIFT RATE DETERMINATION
Drift rates for each sampling run were calculated as a percent of water
flow to the individual fan cells being tested (see Appendix A). The water flow
measurements, made by ESC, are presented in Table 3-**- The water flow values
used to calculate the drift rate were determined by dividing the total water
flow to the tower by the number of individual fan cells (four), because the
PMR values used to calculate the drift rates were for individual fan cells.
EL
The drift rates from the impinger train results and the AP results were
calculated using the PMR for total chromium and the total chromium in the
8.
cooling water at the time of the sampling run. It was assumed that the
concentration of chromium in the drift was the same as the concentration of
3-18
-------
TABLE 3.10. COMPARISON OF MEASUREMENT METHODS FOR TOTAL CHROMIUM EMISSIONS
Run
Number
Pollutant Mass Rate by Ratio of Areas (mg/hr)
Total Chromium
by Impinger Train (GFAA)
Total Chromium
by Absorbent Papers (NAA)
Riser Cell A
A-l
. A-2
Average
650
4,521
2,586
86.7
62.4
74.6
Riser Cell B
B-l
B-2
Average
695
355
525
18.6
40.7
29-7
Riser Cell C
C-l
C-2
Average
632
2,932
1,782
90.7
89.6
90.2
Riser Cell D
D-l
D-2
Average
443
519
481
73-4
12.5
43.0
Tower Average
1,343
59-3
3-19
-------
chromium in the cooling water. The drift rates for the impinger train samples
and the AP samples were calculated using the following formula:
% Drift Rate = Cr PMRa (mg/hr) x 1 hour/6° minutes x 100?
Cr in water (mg/1) x water flow (gpm) x 3.785 L/gal
The calculated drift rates for each run are presented in Table 3.11.
Drift rate as a percent of water flow was also calculated using the mass
emission rate of drift (not chromium) determined by the ESC SP method. The ESC
method is used here for comparison purposes only, as it is not being considered
for use as an EPA reference method. The drift was assumed to have a specific
gravity of 1 gram per milliliter (g/ml). The drift rate was calculated from
the ESC data using the following formula:
% Drift Rate mass emission rate (g/sec) x 60 sec/min x iQQ%
1 g/ml x water flow (gpm) x 3785-3 ml/gal
The calculated drift rates from the SP results are presented in Table 3.11 as
the average fan cell drift rates for each riser cell tested.
The drift rates calculated using the AP data and the SP results show a low
bias compared to the impinger results and good agreement between the two
methods themselves. The differences between the AP and SP results and the
impinger results may be explained based on the observations made by SoRI (see
Section 3.2.2). The SP and AP technique may significantly underestimate the
small droplet flux downstream of high-efficiency drift eliminators.
3-20
-------
TABLE 3.11. COMPARISON OF MEASUREMENT METHODS FOR DRIFT RATES
Run
Number
Drift Rate as a Percent of Water Flow
Impinger Train
(GFAA)
Absorbent Paper
(NAA)
Sensitive
Paper
Riser Cell A
A-l
A-2
Average
0.0019*
0.0130*
0.0074*
0.0003*
0.0002*
0.0003*
0.0002*
Riser Cell B
B-l
B-2
Average
0.0020*
0.0010*
0.0015*
0.0001*
0.0001*
0.0001*
0.0004*
Riser Cell C
C-l
C-2
Average
0.0018*
0.0082*
0.0050*
0.0003*
0.0002*
0.0003*
0.0001*
Riser Cell D
D-l
D-2
Average
0.0012*
0.0014*
0.0013*
0.0002*
0.00003*
0.0001*
0.0001*
Tower Average
0.0038*
0.0002*
0.0002*
3-21
-------
4.0 SAMPLING LOCATIONS AND TEST METHODS
This section describes the sampling locations and test methods used to
characterize emissions from the mechanical draft crossflow cooling tower at the
National Bureau of Standard's (NBS) Steam and Water Chill Plant in Gaithers-
burg, Maryland. Four fan cell stacks of the cooling tower adjacent to Building
302 were sampled to measure chromium emission and drift rates, drift size
distribution, and exhaust gas velocity. In addition, the water flow was
measured in the single riser pipe serving the four fan cells tested, and
cooling water samples were taken from the water trough for analysis of
hexavalent and trivalent chromium. Meteorological conditions were monitored
and data collected using instruments on site that are owned and operated by
NBS. The relative positions and the type of testing conducted at each location
are shown in the simplified process flow diagram (see Figure 4.1) and
accompanying Table 4.1. The subsections which follow further describe each
sampling location and the applicable test methods.
4.1 COOLING TOWER CELL STACK OUTLETS (SAMPLING LOCATIONS A, B, C AND D)
Emissions testing for chromium and drift emissions, and drift size
distribution determinations by several methods were conducted at each of four
fan cells on the crossflow cooling tower adjacent to Building 302. All
sampling on the first day was performed on the first fan cell (Sampling
Location A), the second day at Sampling Location B, the third day at Sampling
Location C, and the fourth day at Sampling Location D.
4-1
-------
N
RISER PIPE
ACCESS
PORT
*>
LOCATION E
;STAIRS:
GRAVITY FED WATER TROUGH
[ LOCATION A 1
n
1 1
0.
f LOCATION B j f LOCATION C )
Dn
II
WATER DISTRIBUTION MANIFOLD
GRAVITY FED WATER TROUGH
f LOCATION D )
D__._ ,.,_
LOCATION F
MAINTENANCE BUILDING
NO. 302
PARKING LOT
FIGURE 4.1. SKETCH OF NBS COOLING TOWER NEAR BUILDING NO. 302, SHOWING RISER PIPE,
DISTRIBUTION MANIFOLD, WATER TROUGHS, AND SAMPLING LOCATIONS.
4-2
-------
TABLE l|.l. SAMPLING PLAN FOR COOLING TOWER ADJACENT TO BUILDING 302
NBS. GAITHERSBURG, MARYLAND
Sample Type
Sampling
Location
Number
of Runs
Methods
Total Chromium
& Drift Emissions
A, B, C. D
Drift Size
Distribution and
Drift Rate Determi-
nation
Recirculating
Water Flow Rate
A.B.C.D
Cooling Water
Samples
Meteorological Data
NBS
Weather
Instruments
2 at each
location
1 at each
Single point
check before
each run; must
be within 10%
of initial
determination
by complete
traverse
3 grab sam-
ples per run
combined into
one composite
sample
Hourly
EPA Method 13-type impinger
train with GFAA analysis;
filters and impingers re-
covered separately for
collection efficiency check
on two runs
Aligned nozzle train .and disc
train with GFAA analysis;
absorbent paper with NAA
analysis; sensitive paper
with microscopic analysis
Calibrated pitot tube
Cr and NAA (Cr*^) analysis
Dry, wet bulb temperatures,
humidity, wind speed, and wind
direction
-------
The four fan cell stacks were identical in construction and were all approx-
imately 22.7 feet (272 inches) in diameter at the plane of the nozzle and train
(see Figure 4.2). Sampling probes connected to sampling train boxes containing
the impingers were introduced into the flow 2.33 feet into the fan cell stack
and were suspended from a monorail to facilitate traversing the stack. The
propeller anemometer used to measure the axial component of the exhaust flow was
located 3 to 5 inches above the tip of the nozzle or the sampling point.
A Method 13-type impinger train was used for chromium and drift emissions
sample collection. The fan stack was traversed along one axis at 12 points
following the draft method (Appendix C). Each of the 12 points was sampled for
10 minutes for a total of 120 minutes of sampling per run. Propeller anemometer
data were taken at each traverse point during sampling to be used in calculating
the mass emission rate. Two runs were performed at each sampling location. The
impinger contents and filter from one run at Sampling Locations A and C were
recovered separately for a collection efficiency check.
Paired train test runs using the "disc" and "aligned nozzle" particle sizing
trains (see Section 4.9) were all conducted at a single point at each sampling
location. All of the paired train runs were 240 minutes in length.
Absorbent paper (AP) (see Section A.11) samples were collected during each
impinger train run.
Sensitive paper (SP) (see Section 4.10) size distribution testing was
conducted once at each sampling location. Sensitive papers of 47 mm diameter
were exposed at each of 12 equal area test points along one axis of a fan cell.
Exposure times were selected in order to produce samples with a sufficient
number of stains to allow confidence in the resultant droplet size distribution,
but also to prevent overlapping stains. Local updraft air velocity values were
taken at each sampling point using a Gill propeller anemometer and a Fluke
digital multimeter.
4-4
-------
y — 272" DIA.
X"" ""Njr
TRAVERSE POINTS /^ \
/ \
1 AXIS I _ 1
12 POINTS/AXIS V f
12 TOTAL POINTS \ /
v^^^ ^f
^^~
POINT
1
2
3
4
5
6
7
8
9
10
1 1
12
-------
4.2 RECIRCULATING WATER PIPE (SAMPLING LOCATION E)
Circulating water flow rate was determined by traversing the cooling tower
riser pipe using the calibrated pitot tube. A complete traverse was made
initially on the single riser pipe that supplies all four fan cells. A single
point check was then made prior to each testing run. The single point check
was considered sufficient if the measured value was within 10% of the value
determined by the initial complete traverse. To obtain the flow rate to each
individual cell, the measured water flow rate for the one riser water pipe was
divided by four, assuming equal distribution of water to each cell.
4.3 WATER TROUGH (SAMPLING LOCATION F)
During each emissions test run, a recirculating water sample was taken from
the water trough at a point adjacent to the fan cell being sampled. These
samples were taken by hand and stored in 500 ml glass jars. Each sample was
analyzed for hexavalent chromium by RTI (wet chemical method). An aliquot of
each water sample was also filtered through a 1.0-um pore size Teflon filter to
collect the insoluble residue (Cr+^); the filter and residue were then analyzed
by NCSU for total chromium (NAA).
4.4 AMBIENT METEOROLOGICAL STATION
Ambient conditions during sampling were monitored and data collected using
meterological instruments on site that are owned and operated by NBS.
Sufficient data were collected at regular intervals for use in calculations and
are summarized in Chapter 2.
4.5 VELOCITY AND GAS TEMPERATURE
A propeller anemometer was used to determine the total flow velocity in the
axial direction at each sampling point as described in the draft test method
4-6
-------
(see Appendix C). The temperature at each sampling point was measured using a
thermocouple and digital readout.
4.6 MOLECULAR WEIGHT
Flue gas composition was essentially that of the ambient air drawn into the
cooling tower via the fan. Therefore, the dry molecular weight and composition
of air was used.
4.7 CHROMIUM COLLECTED BY IMPINGER TRAINS
Method 5-type sampling procedures, as described in the Federal Register.*
were used with the Method 13-type trains to measure chromium and drift
emissions at Sampling Locations A, B, C, and D (see the draft test method in
Appendix C). Sampling trains consisted of a heated, glass-lined probe and a
series of Greenburg-Smith impingers (two containing 100 ml of deionized-
distilled water, one empty, and one with silica gel) with a 3-inch nominal
Teflon filter located between the third and fourth impinger. A deionized
distilled water rinse of the nozzle, probe, appropriate filter holder portions,
and impingers of the sampling train was made at the end of each test. This
rinse, the impinger contents, and the filter were combined and stored in a
500 ml glass jar, except for the two sampling runs on which collection
efficiency checks were made. For these two runs, the rinse, impinger contents,
and filter were stored and analyzed separately.
The samples were typically concentrated to approximately 25 ml in a 500 ml
glass beaker and then were transferred to another container. The 500 ml
beakers used to concentrate the samples were treated with aqua regia to
solubilize residual chromium and these solutions were treated as separate
*40 CFR 60, Appendix A, Reference Methods 2, 3, and 5, July 1, 1980.
4-7
-------
samples. The total chromium content of the impinger samples (after
solubilization of the chromium with nitric acid) and the total chromium content
of.the solution containing the residual chromium from the beakers was
determined by RTI using graphite furnace atomic absorption (GFAA). The total
chromium catch for each impinger run is the sum of the total chromium content
in the corresponding impinger sample and the total chromium content solublized
from the appropriate beaker using aqua regia.
4.8 CHROMIUM IN COOLING WATER
Cooling water samples collected were analyzed for hexavalent chromium by
RTI using the diphenylcarbazide wet chemical method. Also, a 10-ml aliquot of
the cooling water was filtered through a Teflon filter with a 1.0-um pore size
and the residue on the filter (insoluble trivalent chromium) was analyzed for
total chromium by NAA. A flow chart for the analysis of the cooling water
samples is presented in Figure 4.3.
4.9 DRIFT SIZING USING ALIGNED NOZZLE AND DISC TRAINS
Paired aligned nozzle and disc trains were used to estimate the percent
chromium in drift particles smaller than a certain size. The disc train
consisted of the impinger train set-up described in Section 4.7 with the
exception that no nozzle was attached to the probe and a plexiglass disc was
attached in the plane of the flow around the opening of the probe. This
configuration was designed to collect the majority of drift particles less than
a certain diameter.
The aligned nozzle train was run at the same time as the disc train at the
same single sampling point to serve as a reference measurement for collection
of all sizes of drift particles. It was identical to the impinger train used.
The nozzle was aligned directly with the flow at the point sampled; the exact
4-8
-------
100 ml Aliquot
COOLING WATER
SAMPLE
CHROMIUM
ANALYSIS
(Hexavalent)
10 ml Aliquot
TEFLON FILTER
1.0 urn Pore Size
Filter
NAAfor
CHROMIUM
(Trivalent)
FIGURE 4.3. FLOW CHART FOR ANALYSIS OF COOLING WATER SAMPLES.
-------
flow direction and delta P at that point was determined using a three-dimen-
sional pitot tube.
The catches from each train were analyzed as previously described for the
chromium emissions and drift testing.
4.10 SENSITIVE PAPER TESTING
Sensitive paper (SP) testing was used to measure drift rate and size
distribution. The SP testing relies on droplet collection by inertial
impaction on water-sensitive paper held perpendicular to the flow. This paper
is chemically treated so the impinging droplet generates a well-defined blue
stain on the pale yellow background of the paper. The size and shape of the
stain and the droplet size were correlated by calibrating the SP system with a
mono-disperse water droplet generator over a range of droplet sizes and
impaction velocities.
Processing of exposed SP's consisted of measuring the stain diameters using
a microscrope and a semi-automated GRAF PEN digitizer linked to a microcomputer
which groups stain counts by size range. A computer program employing
calibration curves for specific droplet sizes and impaction velocities was used
to correlate stains with their original droplet sizes. In addition, a
correction factor was applied which incorporated the collection efficiency of
each droplet size range.
4.11 ABSORBENT PAPER TESTING
Absorbent paper (Whatman™ 5^1 filter paper) held in a sensitive paper
sampling device was attached to each traversing impinger train to collect drift
emissions. This was part of an effort to evaluate screening techniques for
cooling tower testing. The sensitive paper device and absorbent paper were
positioned on the probe of the impinger train and were exposed so as to collect
4-10
-------
drift emissions during the 120 minutes of impinger train sampling. Absorbent
paper samples were analyzed for total chromium by NAA.
-------
5.0 QUALITY ASSURANCE
Because the end product of testing is to produce representative emission
results, quality assurance is one of the main facets of stack sampling.
Quality assurance guidelines provide the detailed procedures and actions
necessary for defining and producing acceptable data. Two such documents were
used in this test program to ensure the collection of acceptable data and to
provide a definition of unacceptable data. These documents are the EPA Quality
Assurance Handbook Volume III. EPA-600/4-77-027 and Entropy's "Quality
Assurance Program Plan," which has been approved by the U. S. EPA, EMB.
Relative to this test program, the following steps were taken to ensure
that the testing and analytical procedures produce quality data.
• Calibration of field sampling equipment. (Appendix D describes
calibration guidelines in more detail.)
• Checks of train configuration and calculations.
• On-site quality assurance checks of sampling train components.
• Use of designated analytical equipment and sampling reagents.
Pre- and post-test calibrations were performed for each of the meter boxes
used for sampling. Calibrations were also performed for the temperature
sensing equipment, nozzles, water flow pitot tubes, anemometer sensor, and the
entire propeller anemometer apparatus. Appendix D includes the calibration
data sheets for each dry gas meter used for testing and data sheets for the
calibrations of the other sampling equipment mentioned.
5-1
-------
An on-site audit was performed on the meter boxes used for sampling and
the data are summarized in Table 5-1• Entropy used the procedures described
in the December 14, 1983 Federal Register (48F255670).
TABLE 5.1. METER BOX CALIBRATION AUDIT
Meter Box No.
N-2
N-3
N-7
N-9
Pre- Audit
Y Value
1.0059
1.010
1.010
1.003
Allowable
0.9?Y/
tX
Audit solutions were used to check the analytical procedures of the labor-
atories conducting the chromium analyses. Table 5.2 presents the results of
these analytical audits.
The sampling equipment, reagents, and analytical procedures for this test
series were in compliance with all necessary guidelines set forth for accurate
test results as described in Volume III of the Quality Assurance Handbook.
5-2
-------
TABLE 5.2. AUDIT REPORT CHROMIUM ANALYSIS
Plant:
Task No.:
Date Samples Received:
Date Analyzed
-. ^-27-^6
Samples Analyzed By: RTJ , MCSU
Reviewed By
Sample
Number
QA-i ft?
&A-2
Q(\-3
&A-4
Qfl-5"
&A-S-
• ?.GxoMt. "J. vJ(**m
ug/mi,
Cr+6 or Cr
.221 *)Cr
I.O/ y/mlCt,
0.551 MjCr
Otfto *tl* Cr
0.22S /*}&
O.Ott**Cr
Source of
S ancle
ati>/£et
$M> leen
(W>{ee£
***>{€&£
G?/VD/^r
§ft>t&EZ
Date of Review:
Analytical
Techniaue
MA*
Cr^
A/rtfl
CtM
A/AA
LfAA
1
Auciit
Value
I.OtyCr
I.OvHtr
1.6*6
o.U»*jUCr
0. 1 Mj-Cr
O.I+iC,
neiazive
Error. •;
-3f 5"
1.0
-45.0
'1.4
+ I-2S.O
'15.0
5-3
-------
TABLE 5.3. AUDIT REPORT BROMIDE ANALYSIS
Plant:
Task No.:
Date Samples Received:
Date Analyzed:
Samples Analyzed By: /J fl A -
Reviewed By: "Jt
Date of Review:
Sample
Number
Qfi-l A?
fi^-3
QA-5
ug/mL
_ tf Br
er- or-e--
0.155 M,i Br
^).235^Sr
/D.^S' 45 2r
Source of
Samole
QA6 J&-T
&A-b/£*r
Qfo/GG-L
Analytical
Techniaue
MAA
A/AA
AJAA
AUQII.
Value
0.5 /u2r
^9.5 ^3 2r
£.05*.}
negative
^**^»o*^ *'
*^. * U» , «
-34.5'
-53.0
- %4.o
------- |