TEACUP SOLIDS CLASSIFIER
A TECHNICAL NOTE
Prepared. For
U.S. Environmental Protection Aqency
Office of Municipal Pollution Control
Municipal Facilities Division
401 M Streetr S.w.
Washington, D.C. 20460
September 1986
Prepared By:
Environmental Resources Management, Inc.
999 West Chester Pike
West Chester, Pennsylvania 19382

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TABLE OP CONTENTS
Page
I. Description of Process and Systen Design	1
A.	Process and Process Options	1
B.	Existing and Proposed Installations	4
C.	Manufacturer's Claims	4
II. Evaluation of Design Procedure	6
A.	Design Procedure Recommended by Eutek
Systems	6
B.	Comments on the Design Procedure	6
III. Evaluation of System Performance	7
IV. Level of Confidence in the Teacup System	9
V. Summary of the Teacup Investigation	10

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DISCLAIMER
The information in this document was prepared for the Office of
Municipal Pollution Control under contract number 68-01-7108.
The information was compiled to assist those involved in the
innovative and alternative technology program. This document has
not been subjected to the agency's peer and administrative review
and therefore does not necessarily reflect the views of the
agency.

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I. Description of Process and System Deaiqn
A. Process and Process Options
The Teacup Solids Classifier (Teacup) is a proprietary product of
EUTEK Systems# Carmichael, California. Originally designed for
the removal of inorganic suspended solids from industrial process
waters/ Teacup systems are now being used and marketed for
municipal grit control. This technical note summarizes
information for use by those involved in the U.S. Environmental
Protection Agency's implementation of the innovative and
alternative funding provisions of the Clean Water Act.
1. Process Description
A schematic configuration of the Teacup is shown in Figure 1.
This unit is designed to achieve the separation/ collection/ and
washing of grit particles. Flow enters tangentially at the top
creating a free vortex within the unit. Centrifugal force and
gravity are employed to minimize the discharge of particles
having densities greater than water with the water stream leaving
the Teacup through the central discharge cylinder.
The separated particles settle towards the bottom of the Teacup.
The free vortex boundary layer at the base of the unit sweeps
settling particles and collects them at the central well in the
bottom. Acceleration within the boundary layer helps classify
particles according to different densities. The denser grit
particles are thus separated (to a degree) from lighter organic
particles. Grit is periodically discharged for dewatering
outside the Teacup; organic particles tend to remain with the
wastewater.
2. Process Options
Grit control systems using a Teacup as the central process unit
may be supplied with additional units for quiescent dewatering
and removal of larger grit solids. These units include those
offered by EUTEK, such as the Grit Snail or Decanter. Static
screens may also be provided upstream of Teacup units to insure
that the latter are used only for the removal of fine grit.
Parallel Teacups with sequencing headboxes may be employed to
maintain peak grit removal efficiency during average and peak
flow conditions.
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Figure 1
Mechanics of Teacup Operation
1000.0
FREE VORTEX
CENTRIFUGAL ACCELERATION
Discharge Cylinder
100.0
J
s
I
ffl

8

<
Trajectory of
Bottom Swept
Solids
Solids
Discharge
RADIAL/TANGENTIAL VELOCITIES
IN BOUNDARY LAYER
10.0
Solids Swept to
Central Well
Reference: "Principles of Teacup
System Grit Control",
George E Wilson, President,
EUTEK Systems Inc .
Sacramento California
Settling Solids
I I
Tangential
Velocity
3 fps
Baffle
850 microns
-Discharge
Cylinder
4000 microns
0 5 fps Radial
Velocity
Free Vortex
Boundary Layer
Solids Storage Well
Large Mat'l Excluded
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3. Process Specifications
Grit control systems using a Teacup are designed to achieve
greater than 95 percent removal of particles down to a minimum
size (the practical minimum being 20 micron sand). Separation of
smaller particles is also expected, though with lower efficiency.
The solids blowdown from a Teacup is also normally specified to
contain less than a certain fraction of organics (typically
fifteen percent). Head loss through the unit is designed to be
less than a maximum value (varying from a few inches to several
feet). The hydraulic flow range in which these specifications
are achievable is also given. Changes in flow rates would affect
the system's capability.
4. Design Parameters
To achieve the required performance in a Teacup/ both the
concentration and sand equivalent size (SES) distribution of
particles in the inflow should be considered. Based on these
parameters/ the centrifugal force in the discharge cylinder is
set at the design flow to separate the design particles within
the Teacup.
5. Design Assumptions
Design assumptions are related more to the definition of the grit
control problem than with the process or equipment. Very little
information is usually available about the grit loading and
particle size distribution at different flow rates at a given
municipal wastewater treatment plant. Peak flow rates# for
example/ are known to contain substantially greater quantities of
grit. However, details of grit characteristics and distribution
of organics with different sizes of grit are seldom available.
When these data become available, a more exact design of a Teacup
system could be easily accomplished.
6. Influence of Flow Variability
A single Teacup can operate under flow variations of 1:3 without
substantial changes in performance. Sudden increases of flow
will increase head loss through a Teacup/ but the separation and
collection of particles is known to improve at peak flow due to
increased centrifugal force. Decreases in flow/ on the other
hand4 would result in less efficient separation of particles. A
properly selected configuration of Teacups with sequencing
headbox is expected to reduce the influence of extreme flow
changes and grit loading variations, according to the
manufacturer.
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B. Existing and Propoaed Installations
There are several municipal wastewater treatment plants in the
United States where Teacup systems have been installed to achieve
grit control. Details of these municipal installations are given
in Table 1. In addition to these installations, Teacup systems
have also been installed for process water reclamation and reuse
in food processing industries.
The first use of Teacup systems for municipal grit control was
during a study in Sacramento during 1979* according to the
manufacturer. (Source: "Teacup Pre treatment of Wastewaters/"
George E. Wilson, National Conference on Environmental Engineer-
ing/ ASCE, 1980.) After a successful evaluation in this study/
the first unit was installed for operation at Florence/ Oregon
during 1982. (Source: "Economical All-hydraulic Preliminary
Treatment," Rick J. Mumpower and George E. Wilson, 57th Annual
Conference/ Exposition WPCF, 1984.) Some of the industrial
installations involving Teacups were in operation before 1979.
C. Manufacturer's Claims
Based on their observations at municipal installations, EUTEK
claims the following advantages of the Teacup system when
compared with other conventional grit removal systems:
- Greater (higher percentage) removal of abrasive
materials.
Improved performance at peak flows (which are
characterized by increased grit loading).
Low organic content of removed abrasives. This is
achieved by classification within the Teacup and
by fluidizing the "stored solids" before each
blowdown.
The low organic content of the grit makes it possible to dewater
the solids in a quiescent zone, resulting in lower solids loss.
More efficient solids removal results in reduced frequency for
costly digestor cleaning at municipal wastewater treatment
plants. Sludge handling equipment performance is also improved
by the absence of abrasives. EUTEK claims that cost
savings in other treatment steps at municipal plants quickly pay
for the investment in Teacup systems.
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TABLE 1
EXISTING AND PROPOSED INSTALLATIONS OP
TEACUP SYSTEMS - MUNICIPAL WASTEWATER TREATMENT
Location
Date
Consulting Engineer
Flow
MGD
Micron
Size*
Florence/ OR
Santee, CA
8/82
4/83
Rick Mumpower, Supt.
Florence, Oregon
Bert Elkins, Manager
Santee* California
2.0
100
0.1	50
(Demo Plant)
Cincinnati# OH
1/84
Jones & Henry
Toledo, Ohio
U1
Lake Wildwood/ GA 3/84
Jerseyville# IL 5/84
Tribble & Richardson
Macon, Georgia
Watwood & Heavener
Centralia, Illinois
0.4
2.0
150
150
Hebron, OH
6/84
Bird & Bull
Worthington, Ohio
1.7
300
Calera, AL
9/84
Lucas & Carr
Birmingham/ Alabama
1.13
200
* > 95% particle capture
** SST = Stacked Screen/Teacup System
Equipment
(2) 48" Teacups (SST*
(2) 48" Static Screen
(1) 24" Teacup (SST)
(1) 18" Static Screen
(1) 1 CY/HR 6" Grit Si
(1) 34" Teacup
(1)	66" Teacup
(1)	Discharge Box
(2)	40" Teacups
(1)	Influent Headbox
(1)	1.5 CY Decanter
(2)	42" Teacups (SST)
(1)	Influent Headbox
(1)	Common Discharge
Channel
(2)	48" Static Screen;
(2)	1.5 CY Decanters

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Location	Date
Wintersett IA	9/84
Fall Creek, IN	11/84
Butler/ GA	2/85
Matoaka, WV	4/85
Orange County# FL	7/85
Consulting Engineer
Vance & Hockstetier
Winterseti Iowa
Beam/ Longest & Neff
Indianapolis/ Indiana
Tribble & Richardson
Macon/ Georgia
Milam/BCM Engineering
Post Buckley Schuh Etc.
Orlandof Florida
Grimes/ IA	8/85
Indian River, FL 11/85
Princeton/ TX	12/85
Veenatra & Kimm
Des Moines, Iowa
Williams Hatfield Etc.
Ft. Lauderdale* Florida
Russell Bettes & Assoc.
Dallas/ Texas
Algona/ IA	4/86	Wallace/ Holland Et A1
Mason City/ Iowa
Data Source: EUTEK SYSTEMS/ Inc.
* > 95% particle capture
Flow
MGD
Micron
Size*
Equipment
2.0
1.96
1.0
0.22
4.5
200
100
150
100
100
2.36
75
(1
(1
(2
(1
(1
(1
(1
(1
(3
(1
(2
(3
(2
(1
(1
62" Teacup
Discharge Box
72" Teacups
CY/HR 6" Grit Snail
50" Teacup (SST)
48" Static Screen
28" Teacup
1.5 CY Decanter
64" Teacups (SST)
Influent Headbox
Common Discharge
Channel
72" Static Screens
Screenings Chute
1 CY/HR 6" Grit Snai
62" Teacup
1.5
0.59
4.1
100
300
100
(1) 64" Teacup (Pressure
(1) 1.5 CY Decanter
(1) 34" Teacup
(1) Screen Support
(1)	1.5 CY Decanter
(2)	70" Teacups (Pressuri
(1) Custom Discharge Pipi
(1) 1.5 CY Decanter
(1) Influent Headbox

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II. Evaluation of Design Procedure
A. Design Procedure Recommended by EPTEK Systems
EUTEK Systems recommends that the grit loading under different
flow conditions in a municipal wastewater treatment plant should
first be defined before completing the final Teacup system
design. They also feel that the Teacup itself is the best
analytical device available to carry out this problem definition.
A pilot study should be carried out by using a small Teacup
(fifteen inches in diameter) to separate and collect particles
down to a size of 20 to 25 microns from sample influent flows at
different rates. Ideally, this study should be conducted with
samples of the influent collected under minimum, average, and
peak inflow conditions. Alternatively, pilot studies under
available flow conditions, past data on flow variations at the
plant, and information from earlier studies at similar municipal
wastewater treatment plants can be used to carry out the design.
The results of this study would then be scaled up to finalize
the performance specifications, size, and configuration of the
qrit control system.
Based on such pilot studies, grit removal systems were designed
and recently installed at existing municipal wastewater treatment
plants (see Table 1). The Teacup system installed at Florence,
Oregon was designed to remove abrasives larger than 100 microns
from a peak flow of 2 mqd. Two 48-inch Teacups with 48-inch
stacked screens were selected. The grit loading was characteri-
zed by uniformly sized sand from the beach community served by
the wastewater treatment plant. In contrast. Teacups installed
at Winterset, Iowa and Hebron, Ohio were designed to capture
particles with size greater than 200 and 300 microns, respec-
tively. Based on observations of grit loadinq variations, a dual
Teacup system was selected for the Hebron, Ohio facility while a
single Teacup system was chosen for the Winterset, Iowa plant.
B. Comments on the Design Procedure
According to telephone interviews, both the engineering consul-
tants (Whitman and Howard, Wellesley, Massachusetts) and the
operators (Florence, Oreqon and Winterset, Iowa) of existinq
municipal installations of Teacups appear to be satisfied with
this design procedure. Their opinion is based on observations of
increased grit removal and reduced organic content of captured
solids durinq both the pilot studies and actual operation of the
final system as designed. The paragraphss below discuss these
observations.
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The success of the design depends largely on the problem defini-
tion carried out during the pilot study. Both designers and
operators of wastewater treatment plants should place more
importance on this phase of the design process. Field tests
result in an improved definition of grit loading, while providing
designers and operators an opportunity to observe the possible
benefits of changing to the Teacup system. Additional informa-
tion on flow and grit control characterization changes should be
obtained. Once the grit loading is defined, the design of Teacups
to achieve the required forces for separation of particles within
the unit is based on fundamental principles of fluid mechanics.
To assist in the design procedure, EUTEK .now offers a unit for
trials at larger flow rates (up to 1 mgd) . Owners of several
large municipal wastewater treatment plants have requested that
pilot studies be conducted using this unit before making any
decision on a Teacup system. Such a field test was conducted at
the Park Way Wastewater Treatment Plant in Laurel, Maryland
during December 1985 by the owner's engineer and staff. The
results of this test are still being analyzed.
The pilot procedure for problem definition and design of a Teacup
system is more applicable to retrofits of existing municipal
wastewater treatment plants than to new plants. The design
procedure for new wastewater treatment plants would have to rely
only on data from other applications.
Ill. Evaluation of System Performance
Operators of municipal Teacups have reported satisfactory
performance of the system. Thouqh most of these facilities have
been in operation for relatively short periods of time, reports
indicate that a well-designed Teacup system results in improved
grit control as well as reduced operatinq problems related to
inadequate grit removal (which could result in grit accumulation
in downstream processes).
A summary performance comparison of Teacup versus conventional
grit removal at Sacramento City Main Wastewater Treatment Plant
is given in Table 2.
After nearly three years of operation at Florence, Oreqon, the
Teacup-Static Screen system has achieved elimination of several
major operation and maintenance problems by reducing the solids
load on the wastewater treatment plant. These problems included:
deposition of grit solids in the aeration basin, plugging of
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TABLE 2
TEACUP VERSOS CONVENTIONAL GRIT REMOVAL
Basis: Study at Sacramento Wastewater Treatment Plant
Parameter
Acceleration Field
Minimum Particle Size
Removed
Grit Volume
Grit-Volatile Material*
Grit Inorganic Solids*
Inorganic Solids Removed
Units
Gravities
Microns
Cubic feet/
million
galIons
% of solids
Pounds/
mill ion
gallons
% of total
incoming
Conventional
1
20 0
0.5
23
25
Teacup
41
65
5.0
13
306
73
* Solids Concentration:
70%
Specific Gravity of Inorganic Solids: 2.65
Specific Gravity of Organic Solids: 1.2
Data Source: "Teacup Pretreatment of Wastewaters", George E.
Wilson, National Conference on Environmental Engineering, ASCE,
1980.
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return sludae lines, and sand buildup in the sludqe diaestor.
Earlier, there was no grit control system at this plant.
(Reference: Mumpower and Wilson, op. cit.)
Before changinq over to the Teacup system for grit control at
Winterset, Iowa, the operators had to shut down the sludge
digestors twice a year for removal of solids. No shutdowns were
required during the most recent year with the Teacup system in
operation. Pump breakdown due to the plugqing by abrasive solids
was also reduced. According to the operators, the only attention
required on the Teacup system was conducting a sand blowdown
three or four times a day as specified in the design. Substan-
tial solids removal was observed during peak flows in the sprinq
of the year. (Reference: Telephone conversation with plant
superintendent, Winterset, Tk, December, 1985).
A pilot study of degritting dilute primary sludge was recently
completed at the Duck Island Pollution Control Facility, Lowell,
Masschusetts. The engineering consultant who conducted this
study reported that a direct comparison of the pilot Teacup plant
with the existing cyclone/screw conveyor degritting system was
performed. The averaqe qrit recovery in the pilot Teacup (14.85
cubic feet per million gallons of flow) was 27 times larger than
the average Quantity collected bv the existinq system.
(Reference: "Pilot Teacup Degritting of Primary Sludge, Duck
Island Pollution Control Facility, Lowell, MA" Case Study
published by EUTEK SYSTEMS, Inc., 1985). New information was
also obtained on grit characteristics. Based on these obser-
vations, a system using Teacup and "Grit Snail" (a related piece
of grit handlinq equipment, also produced by EUTEK) processes was
selected. The pilot study was essential both for the selection
and the design of the new svstem. Recent desiqns and install-
ations of Teacup units have included the Grit Snail process,
which is particularly important in larger plants where greater
quantities of grit are generated.
Thus, despite the small numbers of facilities which have
installed the Teacup system and the relatively short periods of
operation, the process unit is characterized as requiring a low
level of maintenance and effectively removing grit from the
wastewater.
IV. Level of Confidence in the Teacup System
The design procedure for the Teacup system depends largely on
problem definition, and the risk of this procedure can only be
reduced by compiling adequate information on grit loadinq
variations at the particular wastewater treatment plant in
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question. Due to this, the Teacup system requires on-site pilot
testing to characterize the waste stream.
Auxiliary process units may be supplied with the Teacups to
complete a grit control system. Fewer support units have been
installed to date, and there are alternate processes and
equipment which may be selected instead of a complete EUTEK
system.
V. Summary of the Teacup Investigation
Pilot tests using Teacup systems are required to improve upon the
design procedures. Such tests should be performed, especially
if the designers or operators of large municipal wastewater
treatment plants require that qrit loading be adequately defined
before finally selectinq or designing a Teacup system. To be
effective, this pilot test must last long enough to develop an
understanding of variations in both flow and grit
characteristics.
With a longer "track record" for the Teacup system, and with more
grit loading data available from both tests and operational
installations, the design procedure could be based on a set of
sound and reliable assumptions. Data from municipal wastewater
treatment plants serving different types of communities
(coastal, rural, interior, urban, metropolitan) would be adequate
to develop a data base for reference by designers of new
installations. Specific bench-scale pilot studies for individual
wastewater treatment plants will provide interim data for
reference by designers.
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