THE ENVIRONMENTAL TECHNOLOGY VERIFICATION
PROGRAM
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ETV
SERA
U.S. Environmental Protection Agency NSF Into.natlona|
ETV Joint Verification Statement
TECHNOLOGY TYPE: Induction Mixer
APPLICATION: Disinfection of Wet Weather Flows
TECHNOLOGY NAME: GAS MASTRRR Series 32 Submersible Chemical Induction
Mixers
COMPANY: The Mastrrr Company
ADDRESS: 205 Laurel Friendswood, TX 77546
PHONE: (800) 299-6836 FAX: (800) 226-2659
WEB SITE: www.gasmastrrr.com EMAIL: mastrrr@c-com.net
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification (ETV) Program to facilitate the deployment of innovative or improved
environmental technologies through performance verification and dissemination of information.
The goal of the ETV program is to further environmental protection by substantially accelerating
the acceptance and use of improved and more cost-effective technologies. ETV seeks to achieve
this goal by providing high quality, peer reviewed data on technology performance to those
involved in the design, distribution, permitting, purchase, and use of environmental technologies.
ETV works in partnership with recognized standards and testing organizations; stakeholders
groups which consist of buyers, vendor organizations, and permitters; and with the full
participation of individual technology developers. The program evaluates the performance of
innovative technologies by developing test plans that are responsive to the needs of stakeholders,
conducting field or laboratory tests (as appropriate), collecting and analyzing data, and preparing
peer reviewed reports. All evaluations are conducted in accordance with rigorous quality
assurance protocols to ensure that data of known and adequate quality are generated and that the
results are defensible.
NSF International (NSF) in cooperation with the EPA operates the Wet-Weather Flow (WWF)
Technologies Program, a part of the Water Quality Protection Center, one of six Centers under
ETV. The WWF Program recently evaluated the performance of a chemical induction system
that can be used in the disinfection of wet weather flows such as combined sewer overflows and
sanitary sewer overflows. This verification statement provides a summary of the test results for
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the GAS MASTRRR Series 32 Submersible Chemical Induction Mixer manufactured by The
Mastrrr Company. Alden Research Laboratory, Inc, performed the verification testing as the
designated ETV Field Testing Organization, using the facilities of USGS's Conte Anadromous
Fish Research Center, Turners Falls, Massachusetts.
TECHNOLOGY DESCRIPTION
Induction mixers are mechanical mixers that can inject and disperse both gaseous and liquid
chemicals into potable water, process water or wastewater. Induction mixers can draw chemicals
from the point of chemical storage to the point of injection, and disperse the chemical into the
water. The dual functionality of the induction mixer essentially eliminates the need for a
separate injection system and diffuser system as commonly found in typical mixing installations.
The major components of an induction mixer are:
• A submersible motor with a propeller shaft,
• A uniquely shaped propeller, and
• A vacuum body surrounding the propeller shaft.
The submersible motor spins the propeller shaft and uniquely shaped propeller in excess of 3000
rpm. The rotation of the propeller causes a reduction in pressure in the vacuum body
surrounding the propeller shaft. This reduced pressure is used to draw chemical from the storage
location into the induction port. The chemical is then propelled outward by the rotating propeller
and mixed vigorously with the water.
Induction mixers have many applications, most of which include the transferring of a chemical
(either gaseous or liquid) into potable water, process water or wastewater. Induction mixers are
most commonly used for chemical disinfection of potable water or secondary treated wastewater.
Induction mixers are effective disinfection mixers because they provide a rapid and thorough
dispersion of disinfectant that greatly improves the reaction between the chemical disinfectant
and the water, which translates into chemical disinfectant and energy savings.
Recently, induction mixers have been used for the disinfection of wet-weather flows. However,
because wet-weather flows are typically characterized by fluctuating flow rates, the performance
of these mixers may vary as compared to their use for potable water or wastewater disinfection
applications where flows are relatively constant. The performance of an induction mixer can be
assessed by the following three parameters:
1. The size of the plume in which the chemical is transferred,
2. The uniformity of the chemical concentration within the plume, and
3. The rate at which the chemical reaches the extents of the plume.
These performance criteria are reported in this verification study in the following manner:
1. Isopleth diagrams showing the size of the plume into which the chemical can be
transferred,
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2. The uniformity of the chemical concentration within the plume as defined by the mix
factor, and
3. The rate at which the chemical reaches the extents of the plume as identified graphically
by the isopleth diagrams.
For this induction mixer verification study, different size induction mixers were operated and
these parameters measured at a hydraulic laboratory where clean water was used as a surrogate
to wet-weather flow and a tracer dye was used as a surrogate to the chemical disinfectant. Using
this controlled laboratory approach provided greater accuracy in measuring the size and
uniformity of the chemical plume created by the induction mixer. The objective of the study was
to verify the achievement of effective mixing within the designated parameters of the testing
program.
VERIFICATION TESTING DESCRIPTION
Test Facility
Testing was performed at the S.O. Conte Anadromous Fish Research Center (CAFRC), Turners
Falls, Massachusetts. The CAFRC is a hydraulic laboratory, consisting of three indoor flumes
(10 ft wide, 10 ft deep, and 104 ft in length) with a total capacity of 150 ft3/s. For this
verification study one of the three flumes was modified in size so that the induction mixers could
be tested at specified channel dimensions and flow velocities. Water was directed to the test
flume in the building via an inlet structure on the bank of the large canal on which the CAFRC is
located.
Each induction mixer was tested in a rectangular flume, incorporating a channel section 7 ft wide
with a water depth of 7 ft. To provide for a relatively uniform velocity distribution at the mixer,
the length of the flume upstream of the mixer was 20 ft, and the test channel entrance was
rounded to avoid flow separation. Upstream of the test channel entrance, the flow was guided by
a straight flume 10 ft wide and 32 ft long, with an upstream flow distributor. Downstream of the
mixer, the test flume was 28 ft long before expanding to the wider 10 ft flume width. Provisions
were made to accommodate installation of the mixer at the designated location in the test flume,
in accordance with instructions and mounting hardware from the manufacturer.
Methods and Procedures
The Mastrrr Company provided a 5 FTP, 10 FTP and 20 FTP induction mixer for verification
testing. Each induction mixer was installed in the test flume, and tested separately under nominal
flow velocities of 0.5 ft/s, 1.25 ft/s, and 3.0 ft/s. For each test, the flow velocity was held steady
at a water depth of 7 ft and the mixer was operated with a tracer dye as a surrogate for the
chemical disinfectant. A sampling rig was positioned at locations 5 ft, 10 ft, and 15 ft
downstream of the mixer to collect samples over the entire cross section of the flume. The size
and nature of the "chemical" plume was characterized by measuring the dye concentration over
the entire cross section of the flume. Figure VS-1 describes the test conditions under which
samples were collected during the verification testing.
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5 HP mixer operated at
0.5 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
10 HP mixer operated
at 0.5 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
20 HP mixer operated
at 0.5 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
5 HP mixer operated at
1.25 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
10 HP mixer operated
at 1.25 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
20 HP mixer operated
at 1.25 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
5 HP mixer operated at
3.0 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
10 HP mixer operated
at 3.0 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
20 HP mixer operated
at 3.0 ft/s and samples
taken at 5, 10 and 15 ft
downstream of mixer.
Figure VS-1: Operating Conditions for Induction Mixer Verification
Rhodamine WT tracer was used as the injection tracer. A stock injection solution of the tracer
was prepared by serial dilution of 20% commercial solution with distilled water. The injected
tracer rate and concentration were selected such that a mixed concentration at the sampling rig
location of approximately 10 ppb to 20 ppb was achieved.
The sampling rig had 25 withdrawal ports located equally spaced across the 7 ft x 7 ft cross-
section. Only one downstream position was sampled at a time, and provisions were made for
locating and moving the sampling rig so that only one sampling rig would be in the flume
channel at one time. Samples from the 25 suction tubes were drawn at approximately equal flow
rates for about 10 to 12 minutes. This continuous sampling time was adequate to produce a time
average or typical concentration reading. Each of the 25 samples was then analyzed for
concentration of tracer using a laboratory-calibrated fluorometer.
The tracer dye concentration at each of the 25 sampling ports throughout the cross section of the
flume allowed for the development of isopleth diagrams that were used to demonstrate the extent
and uniformity of the chemical plume. Figure VS-2 shows an example of a concentration
isopleth diagram.
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6 -
5 -
J 4-
i
3 -
Ss 2^
1 -
TEST: 1
HP: 5
Flume Velocity (ft/s): 0.55
Sampling Location (ft): 5
Max. Normalized
Concentration: 2.14
Normalized Sample
Standard Deviation: 0.69
Mix Factor: 0.47
-3-2-10 1 23
DISTANCE FROM FLUME CENTERLINE, FT
Figure VS-2: Example of Normalized Concentration Distribution Isopleth Diagram
The isopleth diagrams were prepared for each test condition using normalized concentration
values. The measured tracer concentration at each cross-section was normalized by dividing the
measured concentration by the uniform concentration (Cu) (where Cu is the tracer concentration),
if the tracer was equally dispersed throughout the cross-section of the flume. Thus, a normalized
concentration of 1.0 means that the theoretical targeted concentration has been achieved. The
performance of the induction mixers was interpreted from these isopleth diagrams.
VERIFICATION OF PERFORMANCE
The mixers produced a roughly circular plume with higher concentrations in the center. Smaller
plume areas and higher peak concentrations were observed under the higher flow velocity
conditions. In other words, as the energy imparted by the mixer became smaller in relation to the
kinetic energy of the flow in the flume (related to flow velocity), the level of mixing observed
also lessened. At the lowest flume velocity (0.5 ft/s), the tracer concentrations were more evenly
distributed across the flume cross-section and approached a uniform mix, as the plume was able
to spread rapidly.
The normalized concentration values and the corresponding isopleth diagrams were used to
generate the numerical performance indicators for each of the induction mixers. These indicators
are described below and the results are presented in Table VS-1.
A mix factor, F, was calculated for each test using the isopleth diagram. The mix factor indicates
the percentage of the total cross-sectional flume channel area that experienced a theoretical
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complete mix (i.e. equal dye concentration throughout the entire cross-sectional area). By
definition, a mix factor of 1 (or 100%) indicates that complete theoretical mixing has occurred.
The mix factor provides insight into the area affected by a concentration of chemical greater than
the theoretical uniform concentration. In general, the channel area affected by the mixer
increased as horsepower increased and decreased as flow velocity increased. For example, as
presented in Table VS-1, at 10 ft downstream of the mixer and a flume velocity of 1.25 ft/s the 5
HP mixer affected 35% of the channel area whereas the 20 HP mixer affected 51%.
Additionally, when considering the 5 HP mixer at the 10-ft downstream sampling location, the
area affected at a flume velocity of 0.5 ft/s was 48% as compared to only 32% at 3.0 ft/s.
The maximum (peak) normalized concentration is the highest concentration of tracer dye
observed within the plume, which generally occurred in the center of the channel, closest to the
point of injection. The maximum normalized concentration is an indicator of the uniformity of
the plume concentrations produced by the mixer. This factor is important because it is possible to
have two sets of plume data with similar mix factors but with substantially different maximum
concentrations. For example, the 5 HP mixer at the 3.0 ft/s flume velocity at the 10-ft and 15-ft
downstream sampling location had approximately equal mix factors of 0.30. With no further
information, this could lead to an erroneous conclusion that the plume does not spread as it
moves downstream away from the mixer. The maximum normalized concentrations from the two
sets of data, however, reveal that the plume is in fact continuing to disperse as it moves
downstream, with the maximum value decreasing from 8.52 times to 6.66 times the theoretical
average as it moves from 10 ft downstream to 15 ft downstream.
The standard deviation of the normalized dye concentrations at each sampling location
characterizes the uniformity of plume concentrations produced by the mixer. The standard
deviation is the mathematical expression of the variation of chemical concentration around the
average concentration. More uniform mixing is represented by smaller standard deviations. A
standard deviation of 0.0 would represent complete uniformity of mixing. Similar to the mix
factor trend, uniformity of the chemical concentration within the plume increased as mixer HP
increased and decreased as the flow velocity increased.
Table VS-1 below provides a summary of the mix factor, maximum normalized concentration,
and standard deviation for the three induction mixers at each of the three flume velocity
conditions.
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Table VS-1 Summary of Numerical Performance Indicators
5 ft downstream of
Mixer
5 HP
10 HP
20 HP
10 ft downstream of
Mixer
5 HP
10 HP
20 HP
15 ft downstream of
Mixer
5 HP
10 HP
20 HP
Flume Velocity 0.5 ft/s
Mix Factor, F
Maximum Normalized
Concentration
Standard Deviation
0.47
2.13
0.69
0.57
1.49
0.30
0.46
1.79
0.28
0.48
1.68
0.47
0.56
1.28
0.17
0.49
1.41
0.20
0.54
1.47
0.33
0.43
1.16
0.11
0.52
1.25
0.20
Flume Velocity 1.25 ft/s
Mix Factor, F
Maximum Normalized
Concentration
Standard Deviation
0.32
6.55
1.84
0.44
3.02
1.04
0.52
2.82
0.76
0.35
4.47
1.51
0.43
2.39
0.74
0.51
2.16
0.53
0.39
3.66
1.22
0.46
2.13
0.61
0.52
1.96
0.42
Flume Velocity 3.0 ft/s
Mix Factor, F
Maximum Normalized
Concentration
Standard Deviation
0.17
13.34
2.61
0.23
12.00
2.41
0.32
7.73
2.11
0.28
8.52
2.08
0.33
7.11
2.02
0.36
5.01
1.51
0.32
6.66
2.00
0.33
4.88
1.56
0.38
3.73
1.20
Mean velocity gradient (G) is a measure of mixing intensity and has become an industry standard
for representing the fluid dynamics of mixing. The G number gives an indication of turbulence
as it relates to head loss, which in turn relates to mixing, and is a therefore a parameter of
disinfection efficiency. The mean velocity gradient for a typical well-designed diffuser grid
system is on the order of 200-500/sec. Research indicates that a G number between 700 and
1,000/sec may be appropriate for disinfection (White, 1992). For the purposes of the verification
testing, the mean velocity gradient is used to gauge whether a particular sized induction mixer at
a particular velocity is capable of providing mixing adequate for disinfection.
In order to calculate the mean velocity gradient, a minimum affected volume of process water
must be calculated. The method used to define the affected volume in the open channel during
verification testing was to define the downstream boundary of the channel length beyond which
the mix factor ceased to improve by more than five percent. This criterion was made on the
assumption that the energy imparted by the mixer had a less significant role in mixing than the
energy imparted by the kinetic energy of the flowing process water.
By determining the smallest size mixer that results in sufficient mixing, an appropriate ratio of
horsepower to flow (MGD) can be established. The following criteria were used to assess if
sufficient mixing was provided for disinfection of wet-weather flow process water for the
purposes of verification testing:
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• The standard deviation for the mixing zone was less than 0.5, and consequently the
maximum normalized concentration of the tracer was not significantly more than twice
the normalized mixer concentration, which suggested the energy imparted by the mixer
dispersed disinfectant effectively across the cross-sectional area;
• The mix factor ceased to improve by more than five percent, which suggested the energy
imparted by the mixer dispersed disinfectant more aggressively than the kinetic energy of
the flow of process water, which defines an affected volume of disinfected water from
which to calculate the mean velocity gradient; and,
• The mean velocity gradient (G) is close to, if not greater than, 700/sec within the
minimum established volume of water, which can assist in determining an appropriately
sized motor for a particular application.
The following is a summary of the verification tests in which a sufficient mixing criteria was
achieved, and the correlating power to process water volume ratio:
• The 5 HP mixer marginally failed to provide sufficient mixing at a flume velocity of 0.5
ft/s within the 7 ft x 7 ft open channel. The actual diameter of the plume where superior
mixing was observed was 6 ft. The 5 HP unit failed to provide sufficient mixing at flume
velocities greater than 0.5 ft/s. This equates to a horsepower to MOD ratio of 0.50.
• The 10 HP mixer provided sufficient mixing at flume velocities of 0.5 ft/s within the 7 ft
x 7 ft open channel, and marginally failed to provide sufficient mixing at 1.25 ft/s. The
10 HP unit did not provide sufficient mixing at flume velocities greater than 1.25 ft/s.
This equates to a horsepower to MGD ratio of 0.46.
• The 20 HP mixer provided sufficient mixing at flume velocities of 0.5 and 1.2 ft/s within
the 7 ft x 7ft open channel. This equates to a horsepower to MGD ratio of 0.53.
In summary, the data suggest that a mixer sizing criteria of between 0.46 and 0.53 HP/MGD
resulted in mixing sufficient for disinfection for mixing applications in the 7 ft x 7 ft open
channel with flow velocities between 0.5 and 3.0 ft/s. The data also indicated a break point at a
flow velocity 1.25 ft/s, where at higher velocities the influence of higher horsepower on the size
of the mixing zone volume has diminishing returns. It is clear that flow velocity significantly
influences the ability of the mixers to effectively disperse tracer. Therefore, expected range of
flow velocities must be considered when selecting an appropriately sized mixer during the design
of open channel mixing facilities.
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Original Signed by
E. Timothy Oppelt
9/27/02
Original Signed by
Gordon Bellen
9/27/02
Gordon Bellen
Vice President, Federal Programs
NSF International
E. Timothy Oppelt
Director
National Risk Management Research
Laboratory
Office of Research and Development
United States Environmental Protection
Agency
NOTICE: Verifications are based on an evaluation of technology performance under specific,
predetermined criteria and the appropriate quality assurance procedures. EPA and NSF make no
expressed or implied warranties as to the performance of the technology and do not certify that a
technology will always operate as verified. The end user is solely responsible for complying
with any and all applicable federal, state, and local requirements. Mention of corporate names,
trade names, or commercial products does not constitute endorsement or recommendation for use
of specific products. This report is not a NSF Certification of the specific product mentioned
herein.
Availability of Supporting Documents
Copies of the ETV Protocol for Equipment Verification Testing Induction Mixers
Used for High Rate Disnfection of Wet Weather Flows dated July, 2002, the
Verification Statement, and the Verification Report (NSF Report
#02/02/EPAWW399) are available from the following sources:
(NOTE: Appendices are not included in the Verification Report. Appendices are
available from NSF upon request.)
1. Water Quality Protection Center ETV Program Manager (order hard copy)
NSF International
P.O. Box 130140
Ann Arbor, Michigan 48113-0140
2. NSF web site: http://www.nsf.org/etv (electronic copy)
3. EPA web site: http://www.epa.gov/etv (electronic copy)
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