United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-82-002
February 1982
Research and Development
Technology
Assessment of the Deep
Shaft Biological Reactor
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EPA-600/2-82-002
February 1982
TECHNOLOGY ASSESSMENT
OF THE
DEEP SHAFT BIOLOGICAL REACTOR
by
Roy F. Weston, Inc.
West Chester, Pennsylvania 19380
Contract No. 68-03-2775
Project Officer
Robert P. G. Bowker
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ClLNICINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental
Research Laboratory, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
11
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FOREWORD
The U.S. Environmental Protection Agency was created because
of increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony
to the deterioration of our natural environment. The complexity
of that environment and the interplay between its components re-
require a concentrated and integrated attack on the-problem.
Research and development is that necessary first step in
problem solution, and it involves defining the problem, measur-
ing its impact, and searching for solutions. The Municipal En-
vironmental Research Laboratory develops new and improved tech-
nology and systems for the prevention, treatment, and management
of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources for the preservation and
treatment of public drinking water supplies and to minimize the
adverse Economic, social, health, and aesthetic effects of pol-
lution. This publication is one of the products of that re-
search, ,a most vital communication link between the researcher
and the user community.
The innovative and alternative technology provisions of the
Clean Water Act of 1977 (PL 95-217) provide financial incentives
to communities which use wastewater treatment alternatives that
reduce costs or energy consumption over conventional systems.
Some of these technologies have been only recently developed and
are not in widespread use in this country. In an effort to in-
crease awareness of the potential benefits of such alternatives
and to encourage their implementation where applicable, the Mu-
nicipal Environmental Research Laboratory has initiated this se-
ries of Emerging Technology Assessment reports. This document
discusses the applicability and economic feasibility of utiliz-
ing the Deep Shaft Biological Reactor for municipal wastewater
treatment facilities.
Francis T. Mayo
Director
Municipal Environmental
Research Laboratory
111
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ABSTRACT
One of the recent changes in the Federal funding policy for
municipal wastewater treatment facilities requires the analysis
and evaluation of innovative and alternative technologies during
the development of wastewater management alternatives. The ob-
jectives of this requirement are: (I'2)
1. To incorporate more cost-effective and energy-
efficient systems in publicly-owned treatment
works (POTW's) than those utilizing traditional
or conventional design practice.
2. To encourage innovative and alternative processes
that provide for the reclamation and reuse of
wastewater.
3. To encourage the utilization of recycling tech-
niques, land treatment, and new and improved
hazards of joint municipal and industrial treat-
ment.
This requirement, administered through the Environmental
Protection Agency's (EPA) Construction Grants Program, has en-
couraged the development of several new processes having poten-
tial for application in municipal wastewater treatment practice.
In order to assess the status of development and the capabili-
ties of these "emerging" technologies, EPA has initiated a se-
ries of technology assessments for evaluating these processes.
This technology assessment report is prepared to evaluate the
"Deep Shaft" biological treatment process which is currently
under various stages of development and application.
The Deep Shaft biological treatment process is essentially a
high-rate activated sludge process capable of operating at
BOD5 loading ratios (F/M) between 0.5 and 2.0 kg BOD5/kg
MLVSS.(3) These extremely high loadings are achievable be-
cause of the capability of the system to carry and maintain
mixed liquor volatile suspended solids (MLVSS) concentration
values between 5,000 and 10,000 mg/L. As a result, a much lower
volume (aeration period) is required than in the conventional
activated sludge process.(4/5)
iv
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The hardware consists of a vertical subsurface reactor shaft
between 90 and 250 m (300 to 800 ft) deep, with hydraulic mean
residence times on the order of 60 minutes. Depending on the
operating mixed liquor volatile suspended solids (MLVSS) concen-
tration, the effluent from the reactor can be treated utilizing
either the flotation or sedimentation process.
Based on a cost and energy analysis, no definitive conclu-
sions could be drawn relative to cost or energy savings that can
be realized by use of the Deep Shaft process. For the plant ca-
pacities used in the cost analysis (1,892 to 37,850 m3/d; 0.5
to 10.0 mgd), the installed capital cost estimates for the Deep
Shaft process were equivalent (_+ 25%) to the conventional air
activated sludge process.
The Deep Shaft process showed some savings in installed cap-
ital costs over the pure oxygen activated sludge system for all
of the flow ranges for which the comparative analysis was pre-
pared, when the cost comparison is based on present worth val-
ue, all three technologies are found to be equivalent. Based on
this evaluation, no significant national impacts can be predict-
ed for the Deep Shaft process.
A similar analysis was conducted for the energy requirements
of the three technologies. Based on this analysis, it can be
concluded that the unit energy requirements (kwh/1,000 m3 of
wastewater treated) are the highest for the Deep Shaft process
when treating domestic wastewaters. The pure oxygen activated
sludge process required the least unit energy for the 1,892
m3/d (0.5 mgd) plant size because of the use of purchased
liquid oxygen. For larger plant capacities (18,925 and 37,850
m3/d), however, the pure oxygen process required the same unit
energy as the conventional air activated sludge process. This
was due to the requirement for additional energy for on-site ox-
ygen generation.
Based on this analysis, it is evident that the Deep Shaft
process benefits (cost and energy) can only be realized when the
raw wastewater strength is greater than normal domestic wastewa-
ter. This is because the energy requirements for the Deep Shaft
process treating domestic wastewaters are based on the require-
ment for maintaining liquid circulation velocities rather than
on the basis of 8005 removal. When the raw wastewater BODs
concentration is high ( ^500 mg/L), the cost and energy savings
are likely to be in favor of the Deep Shaft process.
This report was submitted in fulfillment of Contract No.
68-03-2775 by Roy F. Weston, Inc., under the sponsorship of the
U.S. Environmental Protection Agency. This report covers the
period 7 May 1980 to 31 December 1980, and the work was com-
pleted as of 31 December 1980.
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CONTENTS
Foreword . ill
Abstract iv
Figures ............ viii
Tables x
Acknowledgments . . xi
1. Technology Description .... ..1
Introduction 1
Technology Description. ............. 1
2. Technology Development. .... .... 7
Development History 7
Development Status 9
Eco-I Description 10
Eco-II Description 13
Eco-III Description 15
3. Technology Evaluation 26
Process Theory 26
Oxygen Transfer 27
Solids Separation ... 35
Biological Concepts 36
Design Considerations » . . 36
Process Capabilities and Limitations. ...,. 39
Process Capabilities ... 39
Process Limitations 41
Operation and Maintenance Considerations. .... 43
Cost Considerations ..... 44
Energy Considerations ... 44
4. Comparison with Equivalent Technology ...... 45
Equivalent Conventional Concept 45
Cost Comparison 46
Energy Requirements 47
Land Area Requirements . . 47
VI
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CONTENTS
(continued)
5. National Impact Assessment 55
Market Potential 55
Cost and Energy Impacts 58
Risk Assessment -.59
References 60
Appendices . . ..63
A. Cost and Energy AnalysisAssumptions ...... 63
B. Deep Shaft Applications ........ 66
Vll
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FIGURES
Number Page
1. Big hole drilling assembly 3
2. Reverse mud circulation with air assist 4
3. Deep Shaft biological treatment process flow schematic. 5
4. Mixed liquor flow pattern in Deep Shaft reactors. ... 6
5. ICI Deep Shaft reactor configuration along with gas
voidage and dissolved oxygen profile 8
6. Relationship between mixed liquor suspended solids
concentration and solids flux ..11
7. Generalized process flow diagram -- Eco-I design. ... 12
8. Deep Shaft process flow schematic -- Eco-II design. . . 14
9. Gas voidage and dissolved oxygen profile -- Eco-II
reactor 16
10. Shaft configuration and channel geometry detail for
Eco-III Deep Shaft reactor 18
11. Head tank arrangement -- Eco-III reactor . . 19
12. Head tank operating characteristics -- normal flow
(design) conditions (stage 1) 20
13. Head tank operating characteristics -- high flow
(design) conditions (stage 2) ..20
14. Hydraulic profile Eco-III reactor 21
15. Flotation tank modifications -- Eco-III reactor and
mixed liquor feed to Deep Shaft 22
16. Relationship between organic loading (F/M) and
oxygen requirement ...33
17. Illustration of oxygen transfer limiting envelopes
for conventional and pure oxygen processes 34
viii
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FIGURES
(Continued)
Number
Page
18. Dissolved oxygen and BOD profile for Eco-II and Eco-III
Deep Shaft reactors 40
19. Comparison of concentration profiles for conventional
,and Deep Shaft reactor systems 42
20. liand area requirements for the conventional air-
activated sludge and Deep Shaft aeration process .
54
IX
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TABLES
Number Page
1. Comparison Between Three Model Versions of the Deep
Shaft" Reactor System . * . 23
2. Deep Shaft Development and Experience Summary« ... . 24
3. Design and Performance Data for Deep Shaft Facilities . 25
4. Comparative Design and Operating Criteria of Selected
Activated Sludge Processes for Treating Domestic
Wastewater 28
5. Design and Operating Parameters for a Deep Shaft
Solids Separation Process .... 36
6. Comparison Between Deep Shaft and Conventional
Activated Sludge . . . . * . . 37
7. Cost Comparison 1,892 m3/d (0.5 mgd) Facility. ... 48
8. Cost Comparison -- 18,925 m3/d (5.0 mgd) Facility ... 49
9. Cost Comparison -- 37,850 m3/d (10 mgd) Facility. ... 50
10. Energy Analysis (kWh/y) -- 1,892 m3/d (0.5 mgd)
Facility ..... 51
11. Energy Analysis (kWh/y) -- 18,925 m3/d (5.0 mgd)
Facility 52
12. Energy Analysis (kWh/y) -- 37,850 m3/d (10 mgd)
Facility 53
13. Wastewater Treatment Process Profile -- Number of
Facilities 56
14. Wastewater Treatment Process Profile -- Flow to be
Treated 57
x
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ACKNOWLEDGMENTS
The cooperation of the U.S. EPA Municipal Environmental Re-
search Laboratory Staff, Mr. John Smith, Mr. Robert P.G. Bowker,
and Mr. Richard C. Brenner is greatfully acknowledged. We are
particularly indebted to Mr. Bowker, who served as Project Offi-
cer during this effort, for his cooperation in assimilating re-
view comments and in scheduling review meetings, as well as in
assisting the project personnel in completing this assignment.
The technical assistance provided by Eco Technology person-
nel, especially Mr. Keith Day and Mr. Sanford, was extremely
valuable in preparing the technology description of the various
Deep Shaft development version's. Similarly, the staff members
of the UNOX Corporation were helpful in providing project cost
information for different capacity UNOX (Pure Oxygen) systems so
that the technology comparison could be made on an equivalent
basis.
xi
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SECTION 1
TECHNOLOGY DESCRIPTION
INTRODUCTION
One of the recent changes in Federal funding policy for mu-
nicipal wastewater treatment facilities requires the analysis
and evaluation of innovative and alternative technologies during
the development of wastewater management alternatives. Section
201 (g) (5) of the Clean Water Act makes this requirement manda-
tory for planning studies initiated after September 30, 1978.
The objectives of this requirement are:^'2}
1. To incorporate more cost-effective and energy-
efficient systems in publicly-owned treatment works
(POTW's) than those utilizing traditional or con-
ventional design practice.
2. To encourage innovative and alternative processes
that provide for the reclamation and reuse of
wastewater.
3. To encourage the utilization of recycling tech-
niques, land treatment, and new and improved
methods of joint municipal and industrial treat-
ment.
This requirement, administered through the Environmental
Protection Agency's (EPA) Construction Grants Program has en-
couraged the development of several new processes having poten-
tial for application in municipal wastewater treatment practice.
In order to assess the status of development and the capabili-
ties of these "emerging" technologies, EPA has initiated a se-
ries of technology assessments for evaluating these processes.
This technology assessment report is prepared to evaluate the
"Deep Shaft" biological treatment process which is currently un-
der various stages of development and application.
TECHNOLOGY DESCRIPTION
The Deep Shaft biological treatment process is essentially
a high rate activated sludge process capable of operating at
BOD5 loading ratios (F/M) between 0.5 and 2.0 kg BOD5/kg
-------
MLVSS/day.(3) These extremely high loadings are achievable
because of the capability of the system to carry and maintain
mixed liquor volatile suspended solids (MLVSS) concentration
values between 5,000 and 10,000 mg/L. As a result, a much lower
volume (aeration period) is required than in the conventional
activated sludge process.(4"5)
The process consists of a vertical subsurface reactor shaft
between 90 and 250 m (300 to 800 ft) deep, with hydraulic mean
residence times in the order of 60 minutes. The reactor is typ-
ically installed utilizing conventional drilling equipment using
reverse mud circulation. The typical drilling equipment and the
reverse mud circulation technique are illustrated in Figures 1
and 2. In general, carbon steel shafts are utilized for the ex-
terior casing. The shafts are typically grouted with sulfate-
resistant cement to allow isolation from the surrounding geolog-
ical formation.
The reactor is divided basically into two sections, namely,
a downcome,r and a riser. In the initial reactor configuration,
the raw wastewater and return sludge are introduced into the
downcomer section of the reactor, and the mixed liquor is with-
drawn from the riser section. Compressed air is introduced into
both the downcomer and the riser sections to serve as a source
of oxygen, as well as the driving force for fluid transport
through the shaft. The air requirements and air injection depth
are determined by taking into consideration the minimum liquid
circulation velocity and BODs removal requirements. In gener-
al, liquid circulation velocities between 0.9 and 1.5 m/s (3 and
5 ft/sec) are maintained within the Deep Shaft reactor. Depend-
ing on the operating mixed liquor volatile suspended solids
(MLVSS) concentration, the effluent from the reactor can be
treated utilizing either the flotation or sedimentation process.
In the case of domestic wastewater treatment, the raw influ-
ent wastewater generally undergoes preliminary treatment for the
removal of large particles (screenings) and grit. Experience
with the Deep Shaft process indicates that the process can oper-
ate successfully without primary clarification. Figure 3 shows
the generalized block flow diagram for the treatment of domestic
wastewaters using the Deep Shaft biological reactor. Figure 4
shows the general concept and flow pattern occurring within a
Deep Shaft reactor.
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Swivel Tee
Assembly
Kelly
Donut
Weights
Reamer
Stabilizer
Donut
Weights
Spool
Assembly
Drill Pipe
Hold Down
Clamp
Drill Bit
Figure 1. Big hole drilling assembly.
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Bit -
Mud, Air, and
Cuttings Up
Drill Pipe
Mud and
Cuttings
Up Drill Pipe
Figure 2. Reverse mud circulation with air assist,
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Float (Sludge) Recycle
t 1 T '
, » Y
Waste
Sludge, ^^
Scieeiiinys, "^ " ' 1
and Grit
Sedimentation Mode
L^^f
t f Deep ^
i V Shaft J
\
t .
Flotation
Separator
1
i
1 Sink Return
*
Degasser
1
1
i
Sludge Recycle
Treated ^ .
Effluent ""
Clarifier
1
_J
Chlorine
Contactor
\
Figure 3. Deep Shaft biological treatment
process flow schematic.
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Air
Compressor
Raw
Wastewater
Start-Up Air
Process Air
> >
'',-
t
1
A /\ A
I
I
t
Sludge Recycle
Mixed
Liquor
^ Downcomer
Riser
- Shaft
Lining
Figure 4.
Mixed liquor flow pattern
Deep Shaft reactors.
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SECTION 2
TECHNOLOGY DEVELOPMENT
DEVELOPMENT HISTORY
Deep Shaft biological treatment of wastewaters has its ori-
gin in the United Kingdom and was developed from research ef-
forts for the synthesis and production of single cell protein
using methanol as feedstock.^6) The process required the op-
eration of the system with high bacterial density. In order to
satisfy the extremely high requirements for dissolved oxygen,
Imperial Chemical Industries Limited (ICI) adopted a pressure
cycle aerobic fermentor (Deep Shaft reactor) in which the in-
creased hydrostatic pressure between 90 to 250 m (300 to 800 ft)
was utilized to increase oxygen transfer capabilities. The
pressure cycle fermentor utilized air-lift principles in which
the air for bio-chemical oxidation also provided the air for
liquid circulation. An extension of this basic research and de-
velopment work is the application of the process principles for
wastewater -treatment. Wastewater treatment application normally
involves the operation of the Deep Shaft reactor with lower bac-
terial density, less biodegradable substrate (3005), and a
slower growth rate of microorganisms than in the single cell
protein reactor. For these reasons, ICI, Ltd. modified the re-
actor configuration and increased the typical design depth of
the reactor to achieve equivalent oxygen transfer efficiency and
power economy.(7) in addition, ICI initiated several pilot
and demonstration projects involving municipal and industrial
wastewaters.
The ICI version of the Deep Shaft process consists of a deep
subsurface well, a head tank, and a solids separation clarifier.
The ICI Deep Shaft reactor configuration, along with the gas
voidage and dissolved oxygen profiles, are presented in Figure
5. Gas voidage refers to the volume fraction of entrapped gas
bubbles in the mixed liquor, and can be expressed as follows:
r n-ftar, - Volume of gas bubbles ,,,
fc,as voiaage (volume of gas bubbles + volume of liquid) IJJ
The gas voidage difference between the riser and the downcomer
sections of the Deep Shaft reactor is utilized to initiate and
maintain liquid circulation within the reactor.
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Raw
Waatewater
Head Tank -3»-
Compressed Air
>
t \
^
i
W.L.
~^ Effluent
f
\
V.
r
1
Ji
1
j
Dissolved Oxygen
Head Tank Water Uevel
Downoomer
Gas Voidage
Profile
Air Injection
V Dissolved Oxygen
- \ Profile (Estimated)
\
Gas Voidage
Dissolved
Oxygen
,S
Riser
Figure 5. ICI-Deep Shaft reactor configuration along with
gas voidage and dissolved oxygen profile.
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The ICI Deep Shaft reactor is divided into two concentric
sections; one is called the downcomer and the other the riser.
Raw wastewater and recycle sludge are introduced into an open
head tank from which the mixed liquor flows down the downcomer
and upward through the annular riser section to the head tank.
Mixed liquor is also withdrawn from the head tank for solids
separation and to provide for recycle sludge.
Based on these operating principles, a pilot plant was
started by ICI in Billingham, England during 1974. The pilot
plant had a design capacity of approximately 363 m3/day
(96,000 gpd). A 39 cm (15.25 in.) diameter shaft, 130 m (426
ft) deep provided the outside shell for the Deep Shaft process.
During the initial operation of the pilot plant/ the solids sep-
aration process consisted of a dissolved air flotation unit fol-
lowed by a mechanical degasser and clarification unit. The flo-
tation separator was included in the process to make use of the
potentially available dissolved gases present in the Deep Shaft
mixed liquor. Subsequent experience with the Deep Shaft system
indicated that the flotation unit and the mechanical degasser
can be replaced with a vacuum degasser prior to clarification.
Further testing using the clarification mode indicated that the
process is capable of producing better than secondary quality
effluent (6005 = 15 mg/L; SS = 18 mg/L) when operating at
mixed liquor suspended solids concentration (MLSS) values be-
tween 2,000 and 6,000 mg/L.(7/8'9)
In summary, the process development and successful demon-
stration at Billingham, England have created sufficient interest
in Europe, North America, and Japan to warrant extensive market-
ing efforts. Accordingly, ICI has extended process licenses to
Canadian Industries Limited (GIL) of Canada for carrying out
the marketing efforts in North America. Eco Technology (Eco), a
division of GIL, assumed this responsibility in mid-1975 and has
contributed significantly to the current exposure and develop-
ment of this technology. The following subsection describes the
status of development in North America.
DEVELOPMENT STATUS
Eco Technology, a subsidiary of GIL, recognized that the
Deep Shaft reactor volume can be significantly reduced if the
overall system can be designed to operate with high mixed liquor
suspended solids (^6,000 mg/L). Eco Technology also realized
that the limiting constraint for operating the system with high
mixed liquor suspended solids is the gravity separation of the
mixed liquor solids leaving the Deep Shaft reactor. The use of
a gravity separation process unit (e.g., clarifier) has general-
ly been limited to mixed liquor solids concentration values be-
low 6,000 mg/L.(10*11) This is due to the recommended design
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criteria for solids flux through the gravity separation unit.
Figure 6 shows the relationship between MLSS, hydraulic overflow
rate, and solids flux rate for conventional clarification. Based
on this consideration, Eco's development work was initially di-
rected toward incorporating the flotation separator with the
Deep Shaft process. This process system has become known as
Eco-I, the first generation system introduced in North America.
Eco-I Description
The Eco-I Deep Shaft treatment system essentially consisted
of a reactor and a flotation separator. The configuration re-
tained for Eco-I was similar to the ICI model, where the raw
wastewater and return sludge are both introduced to the head
tank and flow through the downcomer and riser sections prior to
leaving the reactor. The velocity in the shaft is maintained
between 0.9 and 1.5 m/s (3 to 5 ft/s) to prevent deposition of
solids within the shaft. The head tank for Eco-I was designed
large enough to disengage coarse air bubbles released during up-
ward flow in the reactor. The mixed liquor from the head tank
is then treated in a flotation cell. Figure 7 shows the process
flow diagram for the first pilot-scale plant installed at Paris,
Ontario utilizing the Eco-I design.(?) The Paris, Ontario pi-
lot plant was constructed with a 39-cm (15.25 in.) shaft which
is 155 m (508 ft) deep.
To initiate flow through the reactor, air from a 690-kPa
(100 psi) compressor is first introduced to the riser section.
Upon initiation of flow, the air flow to the riser section is
gradually reduced while increasing air supply to the downcomer.
Under normal operating conditions, the air distribution between
the downcomer and riser sections is maintained at 67 and 33 per-
cent, respectively. The incorporation of the dissolved air flo-
tation process in the Eco-I design is significant because:
1. Flotation solids are generally of higher concentra-
( > 4%) than underflow solids from gravity sedi-
mentation units (<1.5%).
2. Mixed liquor from the Deep Shaft reactor can be
introduced directly into the flotation cells
without the requirement for a separate air dis-
solution system.
3. Single source of air supply provides the required
dissolved oxygen and the driving force for both
mixed liquor circulation and solids separation in
the flotation cell.
4. Increased concentration of float solids signifi-
cantly reduces the size requirements for waste
sludge handling, treatment, and disposal equipment.
10
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980 (200) -
*:
CT
730 (150) -
O>
x~
O
CO
490 (100) -
£ 280 (200)
O
Daily Average Design Overflow Rate = 20.37 m3/m2.day (500 gpd/sq ft)
Operating Range For
Conventional Clarification
2,000 4.000 6,000
Mixed Liquor Suspended Solids mg/L
8,000)
Figure 6. Relationship between mixed liquor
suspended solids concentration and
solids flux.
11
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Recycle Sludge
^
>
/
Raw ^lT ^ ~ *"!
Wastewater ^ | v
I
Alt |
., _ ,,'^j
n
Compressor
1
A*
1
I
W
1
S
r
Deep
Shaft
>
Waste J
' *l
Sink
Solids
f
Sludge
Float Solids
-I I I I I I I
o -^
Treated
Effluent
Flotation Tank
Figure 7. Generalized process flow diagram --
Eco-I design.
Even though the Eco-1 Deep Shaft process was successful in
treating both municipal and industrial wastewater, the Eco-I op-
eration had the following deficiencies:
1. Potential exists for the development of an anaerobic
environment in the downcomer section between the
air injection point, approximately 50 m (160 ft)
below the water surface and the head tank where
the raw wastewater and return sludge flows are
introduced (Figure 7).
2. Since the raw wastewater injection and mixed liquor
withdrawal are located within the head tank, there
is always the possibility short-circuiting of the
influent flow.
3. Eco-I operation requires air injection to both the
downcomer and the riser. The air flow rates between
the two sections must be properly adjusted to main-
tain the proper gas voidage ratio, and, therefore,
the flow pattern. In the absence of proper air
flow distribution between the two sections, hydraulic
flow reversal can occur, thereby increasing the
possibility for short-circuiting of the influent flow.
12
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4. Eco-I Deep Shaft reactor biology is subject
to varying oxygen tension and waste strength.
5. Eco-I design does not capitalize on the full
potential of dissolved gases available inside the
reactor. As the mixed liquor flows through the
riser section, it undergoes depressurization;
therefore most of the dissolved gases are released
through the open head tank which is maintained at
atmospheric pressure.
Eco-II Description
The information developed during Eco-I design and pilot
plant experiences gained with the Paris, Ontario operation, plus
the full-scale experience with the Emlichheim, West Germany op-
eration have paved the way for improving the Eco-I design and
the resultant development of the second generation Eco-II de-
sign. t10'11)
The Eco-II design basically addressed the shortcomings of
the Eco-I design with respect to the location of influent and
effluent piping and the maintenance of a more stable hydraulic
flow regime. This was accomplished by incorporating a multi-
channel configuration in the shaft design. Figure 8 shows the
simplified process flow schematic utilizing the Eco-II reactor.
In the Eco-II design, influent raw wastewater, together with
the return sludge and overflow from a newly-provided foam oxida-
tion tank, is introduced to the Deep Shaft riser section at a
depth close to the air injection point (25 to 50 m deep). The
riser section of the Ecp-II reactor is compartmentalized into
four sections, as follows (see Figure 8):
1. Primary riser (R]J .
2. Secondary riser (R2)
3. Secondary downcomer (02).
4. U-tube riser (D2R3.)
The combined influent stream (raw wastewater plus return
sludge) is introduced into the secondary downcomer (D^) and
then driven through the U-tube riser (D2R;L) to the primary
riser (RjJ section of the Deep Shaft reactor. When the influ-
ent stream exits from the U-tube riser (D2Ri), it is com-
bined: with mixed liquor flowing through the primary riser
' The wastewater then flows through the primary downcomer
and then the flow is split between the primary (Ri) and
secondary (R2) risers. A portion of mixed liquor is withdrawn
through the secondary riser (R2) for solids separation and ef-
fluent discharge. The secondary riser (R2) is located at a
13
-------
o
tS
O
H
-P
o
to
o
en
w
a) c
o tn
O -H
M to
O< 0)
H
H
o
o
QJ
flJ I
Q I
cx>
Cn
H
14
-------
lower elevation than the U-tube riser section (D2Ri) to
eliminate short-circuiting of influent to the reactor. With this
change in influent injection and effluent withdrawal locations,
the air distribution between the downcomer and riser sections of
the shaft is also revised to inject 67% of the total air re-
quirement to the U-tube riser (D2Ri) and 33% to the primary
downcomer (D±) . As a result, the possibility for flow rever-
sal within the shaft is eliminated and the hydraulic integrity
of the shaft preserved.
The mixed liquor withdrawn from the Deep Shaft is then
passed through a swirl tank for the removal of coarse air bub-
bles prior to solids separation in a f lotation-clarif ier. The
head tank design for the Eco-II reactor is also modified and op-
erates as a closed pressure vessel. The head tank is designed to
operate under 20 to 55 kPa (3 to 8 psi) pressure, and the pres-
sure is controlled by a submerged outlet pipe for the off gases.
The off -gas submergence is provided in what is known as a "foam
tank" which is used to collapse and collect any foam carried with
the off-gas mixture. The foam tank is also used to oxidize sur-
factants and to minimize foaming within the Deep Shaft reac-
'
Improvements in the Eco-II design include the elimination of
the potential anaerobic zone along the downcomer section of the
ECO--I design. This was accomplished by relocating the influent
flow to the reactor near the air diffusers in the riser section.
The riser air is more efficiently utilized in the Eco-II design
than in Eco-I design in which the riser air was primarily pro-
vided for maintaining the proper gas voidage ratio between the
downcomer and the riser. As a result, the total air require-
ments for the Eco-II design are only 80 percent of those re-
quired for the Eco-I design. Figure 9 shows the gas voidage and
dissolved oxygen profile within the Eco-II Deep Shaft reactor.
Eco-III Description
Based on the experience gained with the operation of both
Eco-I and Eco-II systems, a third generation equipment configur-
ation was developed by Eco Technology, hereinafter referred to
as Eco-III. The second generation Deep Shaft reactor configura-
tion (Eco-II) optimized the biological profile inside the reac-
tor and stabilized the hydraulic flow pattern. The air supply
requirements for the Eco-II reactor, however, were determined
predominantly to maintain liquid circulation at peak flow condi-
tions. One of the improvements in the Eco-II reactor design in-
volves the more efficient use of the aeration energy by control-
ling the air flow rate to match influent wastewater flow.
15
-------
Downcomer Section
Downcomer Air at
50 m (175 ft)Approx,
Head Tank Liquid
Level
Gas Voidage
Profile
Riser Air
Influent and
Return Sludge
Effluent
Withdrawal
Gas Voidage Profile
Dissolved Oxygen Profile
Figure 9. Gas voidage and D.O. profile
-- Eco-II reactor.
16
-------
The Eco-III model has the same multichannel configuration as
Eco-II; however, the reactor configuration (inside the shaft)
has been modified to attain approximately equal head loss (fric-
tion loss) in the primary downcomer and riser sections. The ma-
jor improvements in the Eco-III design involve: the integration
of the foam oxidation tank and head tank into a single unit, the
elimination of the swirl tank and extensive process control in-
strumentation, and design improvements in the flotation unit.
These design features are described briefly in the following
paragraphs. Figure 10 shows the shaft configuration and channel
geometry for the Eco-III reactor.
Figure 11 shows the isometric view of the head tank arrange-
ment for the Eco-III reactor. The head tank is submerged with-
in the foam tank, and is equipped with two vent passages for the
effluent gas mixture from the Deep Shaft reactor. The two vent
passages have different levels of submergence in the foam tank,
thereby providing for two operating pressure stages, PI and
?2, inside the head tank. Figures 12 and 13 show a simplified
schematic of the head tank and the vent gas control system. Re-
ferring to Figure 12, normal flow (design) conditions, the oper-
ating liquid level inside the head tank will be maintained at
level LI with a corresponding head tank pressure at PI. The
total hydraulic flow through the Deep Shaft reactor at "average"
design conditions is QTI« Tne flow components to the reactor
consist of the raw waste influent Qj., recycle float sludge
QF, settled sink sludge return from the flotation tank Qs,
and the foam tank overflow, and cumulatively represent the
design flow for the reactor. In general, any deviations in in-
fluent flow rate (Q^) will be balanced with variations in re-
turn sink flow rate (Qs) from the flotation unit. The gravity
return of settled sink sludge from the flotation unit to the
holding tank allows automatic control of the sink sludge flow in
proportion to the hydraulic head difference between the flota-
tion unit and the holding tank.
In summary, the sink flow rate Qs will vary inversely pro-
portional to the raw waste flow rate (Q^) so that the sum of
these two flows (Qi+Qs) will remain at approximately a steady
rate. Simi-larly, during this operating mode (stage pressure
PI), the float skimming mechanism will be operating at speed
NI, providing a steady return sludge flow rate (Qp). As a
result, the Deep Shaft reactor and the flotation separator unit
will be operating under constant hydraulic and solids loading,
respectively. The air supply requirements will also be main-
tained at a steady rate to achieve desired liquid circulation
velocities inside the reactor. Figure 14 shows the typical hy-
draulic profile and the flow routing for the Eco-III reactor
system.
17
-------
Di Primary Downcomer
Ri Primary Riser
Rz Secondary Riser
Dz Secondary Downcomer
DjRt U-Tube Riser
Sectional View
Foam Tank
Overflow ,
Primary
Downcomer
(Di)
Secondary
Downcomer
(D2)
Raw Wastewater
Influent -v \
v'
U-Section
Riser Air
(D2Ri)
^-tj Secondary Riser (R2)
Primary Riser (R,)
Compressed
Air
Primary
Downcomer Air
Primary Riser (Rr)
Effluent to DAF
Unit
Figure 10.
Isometric View
Shaft configuration and channel geometry
detail for Eco-III Deep Shaft reactor.
18
-------
Foam Tank
Low Flow
J-Weir
Head Tank
Opening in
Head Tank
Foam Tank
Overflow
Figure 11. Head tank arrangement - Eco III reactor.
19
-------
Low Flow Vent
Foam Tank Liquid Level (Li)
Foam Tank
Overflow
Head Tank Divider
(Li) Mixed Liquor Level
Head Tank
Foam Tank
Figure 12.
Head tank operating characteristics - normal
flow (design) conditions (stage 1).
Low Flow Vent
Head Tank
Mixed Liquor Level
Head Tank Divider -
Figure 13.
Foam Tank Liquid Level (L2)
Foam Tank
Overflow
High Flow Vent
Foam Tank
Head Tahk
Head tank operating characteristics - high
flov? (design) conditions (stage 2) .
20
-------
Foam Tank
Head Tank
W.S. EL.
n
Deep Shaft
Reactor ,
Foam Tank Overflow
(q)
Mixed Liquor
Flow
Air
WS. EL.
Flotation
Separator
Float Return (QF)
Sink Return (Qs)
W.S. EL.
Influent Waste
(Q')
Holding
Tank
Influent
Mixed Liquor (Or)
QT =-Qi + QF + Qs + q
QT
Treated Effluent
to Disinfection
(QO
Figure 14. Hydraulic profile - Eco-III reactor.
When the raw wastewater flow rate (Q^) exceeds the normal
design conditions (Q±>Qy]L) , the liquid level inside the
head tank rises to maintain flow through the reactor. (See Fig-
ures 12 and 13.) As the liquid level rises above L^, the low
pressure gas vent becomes closed and the head tank pressure will
reach the second operating stage (?2) As a result, the hy-
draulic throughput capacity for the reactor can be increased to
a new level (Q
-------
The other design modification in the Eco-III reactor system
involves the flotation separator unit. The flotation separator
for the Eco-III reactor system is equipped with a "J1 baffle and
a specially designed float sludge skimming ramp. The 'J1 shaped
baffle serves as an impinging barrier for the mixed liquor feed
and helps to separate and release the coarse air bubbles from
the feed stream. As a result, the swirl tank requirement has
been eliminated and the mixed liquor from the Deep Shaft reactor
can be directly fed to the flotation separator. Similarly, the
float sludge skimming ramp serves to circulate the mixed liquor
feed stream around the 'J' baffle and is believed to promote
flocculation of the mixed liquor suspended solids. Improve-
ments to the flotation tank design are shown schematically in
Figure 15.
Table 1 summarizes the various features and improvements in
the design of the three model versions of the Deep Shaft reactor
system. An Eco-III Deep Shaft treatment system is currently be-
ing installed for the City of Portage Le Prairie in Canada. The
status of development since the original ICI reactor was devel-
oped in 1974 and the performance of Deep Shaft reactors are sum-
marized in Tables 2 and 3.
Mixed Liquor Flow from Deep Shaft
Float Solids Return
Variable Speed
Skimmer
Holding Tank
Sink Solids Rake
Sink Solids
Return
- Feed Mixed Liquor to Deep Shaft
Figure 15. Flotation tank modifications -- Eco-III
reactor and mixed liquor feed to Deep
Shaft.
22
-------
TABLE 1. COMPARISON BETWEEN THREE MODEL VERSIONS
OF THE DEEP SHAFT REACTOR SYSTEM
Process/Equipment
Features
1. Head tank
pressure
2. Shaft config-
uration
3. Dissolved
air flotation
tank
4.; Foam oxidation
tank
Eco-I
Atmospheric.
Two channels con-
sisting of a down-
comer and a riser.
Includes swirl
tank for the re-
lease of coarse
air bubbles.
None
5. Influent and
return sludge
introduction
6. Effluent with-
drawal
7. Air injection
8. Air supply
distribution
To head tank.
From head tank.
To riser and
downcomer.
67% of total air
supply to the
downcomer; 33% to
the riser.
Eco-II
Single oper-
ing pressure
between 20.7-
55.2 kPa
(3-8 psi).
Multichannel
configuration
to include
secondary
riser and
secondary
downcomer.
Eco-III
Two (2) distinct
stages of operating
pressure; between
20.7-55.2
kPa (3-8 psi).
Improved multichan-
nel configuration
to approach equal
head loss (fric-
tion) between the
downcomer and the
riser sections.
Direct feed Improved DAF unit
from Deep design; includes
Shaft to DAF a 'J' baffle and
unit; incorpo- a float skimming
rates a bot- ramp.
torn scraper.
Separate foam
oxidation tank
to biologi-
cally stabi-
lize foaming
agents and to
reduce foam
in head tank.
To secondary
downcomer (02)
50 m (150 ft)
below liquid
level.
Foam oxidation
tank installed
within head tank;
serves dual func-
tion: to maintain
head tank pressure
stages and to
stabilize foaming
agents.
To secondary
downcomer (D2)
50 m (150 ft) be-
low liquid level.
From secondary From secondary
riser (R2) ; riser (R2) ; 50
50 m (150 ft) m (150 ft) below
below head tank head tank liquid
liquid level. level.
To primary
downcomer
and U-section
riser
33% of total
air supply to
the primary
downcomer (DjJ
67% to the
U-section ri-
ser (D2Ri) .
To primary down-
comer (DI) and
U-section riser
(D2Ri).
33% of total air
supply to the pri-
mary downcomer
(DX); 67% to
the U-section
riser
23
-------
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SECTION 3
TECHNOLOGY EVALUATION
PROCESS THEORY
Deep Shaft biological treatment is a high-rate activated
sludge process in which a very high mixed liquor microbial pop-
ulation can be maintained to achieve proportionally increased
organic removal rates. It is'well known that biochemical
oxidation of organic compounds is basically controlled by the
following process parameters (15,16):
1. Concentration of organics (BOD).
2. Concentration of active biological solids (MLVSS).
3. Relative biodegradability of the organic mixture.
Biological oxidation results in .the generation of excess
sludge and carbon dioxide as the primary end-products. In aero-
bic systems, such as those employed in the conventional activat-
ed sludge process, the respiratory or oxidative reactions pro-
vide the energy required for both synthesis and growth of bio-
logical population. Also, dissolved oxygen serves as the termi-
nal electron acceptor, and, therefore, is essential for producing
the desired end-products. In summary, the biological reactions
are controlled by two basic transport mechanisms, as follows:
1. Transport of organics (BOD).
2. Transport of oxygen.
The oxygen transport mechanism is controlled by the transfer
rate of oxygen from the gas to the liquid phase, and from the
liquid phase to the biological solids. When unlimited oxygen
supply is available in the liquid phase, the efficiency of the
biological process becomes primarily a function of the capacity
of the microorganisms to assimilate organic molecules.. The rate
of assimilation or the rate of organics removal can be increased
by increasing the MLVSS concentration and by intense mixing.
Effective mixing of biological solids and organic substrate is
accomplished by maintaining high liquid circulation velocities
within the Deep Shaft reactor. The liquid flow velocity inside
the shaft has been estimated on the order of 1 m/s (3 fps) with
a Reynolds number greater than 100,000 (17,18). As a result,
26
-------
high turbulence and intense mixing is achieved within the shaft.
The driving force for liquid circulation and mixing is provided
by a compressor which serves the dual function of supplying air
for both liquid circulation and biological oxidation. The air
supply requirements and air injection depth are generally a
function of the following:
1. Average and maximum design flow rate.
2. Strength of wastewater undergoing treatment.
3. Shaft diameter and associated friction losses due
to fluid dlow.
Since the Deep Shaft biological treatment process utilizes
the same process concepts as the activated sludge process, the
classical relationships between such process design parameters
as the BOD5 loading ratio (F/M), oxygen requirements per kg
BOD5^removed, waste sludge production (kg TSS per kg BOD5
removed) are also applicable for the process design of tne Deep
Shaft biological reactor.
The Deep Shaft process differs from conventional activated
sludge systems in terms of equipment design and operating fea-
tures. These features include the high mixed liquor suspended
solids, mode and efficiency of oxygen transfer, flow regime, and
type of solids separation process. These design and operating
features are summarized in Table 4.
Oxygen Transfer
Proper design of an oxygen transfer system is essential to
maintain desired minimum dissolved oxygen concentration values
under both average and peak loading conditions. Oh a conven-
tional activated sludge system using diffused air or mechanical
surface aeration, the oxygen transfer rate is limited by the
driving force (concentration differential) across the air/water
interface to approximately o.2 kg/m 'h. As a result, the
operating paramaters (mixed liquor volatile suspended solids,
organic loading ratio, etc.) should be carefully selected such
that the oxygen demand values will not exceed the oxygen trans-
fear capabilities. The basic expression involved in estimating
the oxygen transfer rate is:
dc/dt =
(2)
27
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The basic expression involved in estimating the oxygen
transfer rate is:
dc/dt =
where:
dc/dt
KLA
GSW
the rate of change in dissolved oxygen concen-
tration (kg/m3°h)
the oxygen transfer rate coefficient (h~l)
the oxygen saturation concentration in waste-
wastewater (mg/L)
the minimum dissolved oxygen concentration (mg/L)
According to this expression, the oxygen transfer rate in a
specific waste stream or in a mixed liquor can be increased only
by increasing -the attainable saturation value (Csw).
According to Henry's law, the saturation value can be in-
creased by raising the partial pressure of the gas requiring
dissolution. This can be accomplished by either of the follow-
ing methods:
1. Increasing the mole concentration of oxygen in the
source (enriched oxygen systems) such as those used
in the pure oxygen activated sludge process.
2. Increasing the system operating pressure as in the
case of the Deep Shaft biological reactor.
In a pure oxygen activated sludge system, the oxygen trans-
fer rates are approximately five times greater than in systems
using air diffusion or mechanical surface aeration. In the case
of a Deep Shaft biological reactor, the operating pressures are
increased to 1,520 kPa (15 atm), and, therefore, the oxygen
transfer rate is similarly increased to 2,000-3,000 mg/L/h (150
to 200 lb/1,000 cu ft/hr). This increased oxygenation capacity
allows the system to operate with higher mixed liquor suspended
solids concentrations, and, therefore, with lower aeration peri-
ods than in the conventional activated sludge process. A rela-
tionship was developed between organic loading ratio (F/M) and
the oxygen transfer requirement for various MLVSS's. This rela-
tionship is illustrated graphically in Figure 16. An analysis of
this figure indicates that there is a limiting loading' ratio
(F/M) for each mixed liquor suspended solids concentration, above
which the oxygen demand requirements cannot be satisfied by con-
ventional methods. For illustrative purposes, the upper limit
32
-------
0.40
0-32
0.16
0.08
- (25)1 -
- (20) -
Pure Oxygen
Limiting Value
MLVSS:
A) 1,500 mg/L
<*^
B) 3,000 mg/L
© 6,000 mg/L
5 lu.ooo mg/L
Limitind Value - Conventional
0.4
0.8 1.2 1.6 2.0 2.4
Organic Loading (F/M)
Figure 16. Relationship between organic loading (F/M)
and oxygen requirement.
for oxygenation capacity has been assumed at 0.08 kg/m3-h
(5 lb/hr/1,000 cu ft) of aeration volume for conventional air
systems. For example, the organic loading ratio (F/M) must be
maintained below 0.55 when the operating MLVSS is 3,000 mg/L in
order that the aeration capabilities of the conventional equip-
ment will not be exceeded. By reiteration of this technique, a
limiting envelope was developed which relates the organic load-
ing ratio (F/M), MLVSS, and oxygenation capacity. Similarly,
another limiting envelope was developed for pure oxygen systems
with a maximum oxygenation capacity assumed at 0.40 kg/m^-h
(25 lb/hr/1,000 cu ft). Figure 17 shows these limiting enve-
lopes for the conventional and enriched oxygen systems. It is
to be recognized that these limiting curves are developed with
assumed or preselected values for oxygenation capacities and
therefore is for illustrative purposes only. Actual limiting
values may differ depending on the aeration device selected for
a particular application (e.g., fine bubble, coarse bubble,
aeration basin depth, mechanical surface aeration, etc.). In
addition, the limiting envelopes for the different technologies
may overlap.
33
-------
Conventional
Aeration
2,000 4,000 6,000 8,000 10,000
Mixed Liquor Volatile Suspended Solids mg/l
Figure 17.
Illustration of oxygen transfer limiting
envelopes for conventional and pure oxygen
processes based on a maximum capacity of
0.08 kg/m3 . h (5 lb/hr/1,000 cu ft)
for conventional air activated sludge and
a maximum oxygenation capacity of 0.40
kg/m3 . h (25 lb/hr/1,000 cu ft)
34
-------
It is evident from this process evaluation that one of the
major constraints imposed on the design of an aerobic biological
treatment process is the capability of the aeration equipment to
maintain an aerobic environment. The Deep Shaft process is cap-
able of exceeding these limits as the system can achieve up to
90 percent oxygen transfer efficiency. As a result, organic
loading ratios (F/M) as high as 2.0 can be-used with mixed liq-
uor volatile suspended solids concentration values of up to
10,000 mg/L, thereby reducing the aeration periods to 30 minutes
or less.
Solids Separation
One of the major considerations in the design of an aerobic
biological wastewater treatment system involves the incorpora-
tion of an effective solids separation process unit. Gravity
sedimentation units have served this purpose reasonably well
within the operating range for conventional systems (MLSS be-
tween 2,000 and 3,000 mg/L) and oxygen-enriched systems (MLSS
between 4,000 and 6,000 mg/L). These units serve the dual pur-
pose of producing a clarified effluent and a source of sludge
for recirculation. This latter function is critical in main-
taining the biological integrity of the aeration basin to pro-
duce a flocculant biomass which can readily settle. Extensive
studies on the gravity settling and thickening characteristics
of activated sludge have indicated that the process is effective
when the suspended solids concentration values are maintained
below 6,000 mg/L. I10'1;L> This will permit operating the grav-
ity sedimentation units with a reasonable sludge blanket depth
(0.25 to 1m) and within a recommended solids flux of 29 to 120
kg/m2-day (6 to 25 Ib/day/sq ft).
Earlier versions of the Deep Shaft process recognized these
limitations and the process was designed to operate with sus-
pended solids concentration values between 5,000 and 6,000 mg/L.
However, the North American versions of the Deep Shaft process
(Eco-I, Eco-II> and Eco-III) have adopted a dissolved air flota-
tion process as the terminal unit operation, and utilize the
available dissolved gases. The dissolved gases present in the
Deep Shaft reactor simulate the pressure vessel in the dissolved
air flotation process, and provide the driving force during sol-
ids separation. The process possesses additional advantages in
producing a significantly higher float solids concentration (4
to 7%) than the underflow solids concentration from a typical
gravity sedimentation unit (1 to 3%). Table 5 summarizes the
design and operating features of the two concepts.(19)
35
-------
TABLE 5. DESIGN AND OPERATING PARAMETERS FOR A DEEP SHAFT
SOLIDS SEPARATION PROCESS(19)
Parameter
Hydraulic overflow rate,
mVm2*d (gpd/sq ft)
Mass loading,
kg/m2-d (Ib/day/sg ft)
Float solids
concentration %
Sink solids
concentration %
Flotation Mode
20 (500)
320 ( 66)
7-10
3-4
Sedimentation Mode
10 (250)
103 ( 21)
ND1
1-2
No Data.
Biological Concepts
Principally, the Deep Shaft biological treatment process in-
volves the use of aerobic metabolic capabilities for converting
dissolved organics into gaseous (CO2) and solid (waste sludge)
end products. The Deep Shaft process differs from the conven-
tional activated sludge process with respect to its flow regime,
operating pressure, and oxygen tension inside the reactor. A
study initiated to compare the effects of these process features
on the biological properties of the sludge revealed that the
waste sludge from the Deep Shaft process does not differ signif-
icantly from those experienced in conventional activated sludge
systems.(16) Tne results of this study are summarized in Ta-
ble 6.
Design Considerations
The Deep Shaft biological reactor differs from the conven-
tional activated sludge process as oxygen transfer is not ac-
complished at atmospheric pressure.
36
-------
TABLE 6. COMPARISON BETWEEN DEEP SHAFT AND
CONVENTIONAL ACTIVATED SLUDGE
Sludge Properties1
(or) Components
ATP content (mg/L)
Specific oxygen uptake rate
(g/kg.h)
Michaelis-Menton^
growth constant - Ks
(mg/L)
Deep Shaft
Reactor
0.806
40
50
Conventional
Activated Sludge
0.537-0.991
14.5-57.7
20-50
Physical Characteristics
Specific resistance, 1.29
m/kg x 1014
Compressibility index 0.85
Waste sludge concentration, % 2.1
8.543
0.78
0.94
^Average values for sludge properties are reported; compar-
ison was made of sludges produced from the treatment of
primarily domestic wastewaters.
^Refers to the concentration of BOD5 (raw wastewater) at
which the specific oxygen uptake rate is one-half the maximum
value. The term "Michaelis-Mentoh Growth Constant" is used for
comparison of specific oxygen uptake rate values because of
the belief that the theory of enzyme reaction kinetics is
directly applicable in describing the growth or BOD5 removal
kinetics in the activated sludge process.
3Physical characteristics for waste activated sludge from con-
ventional air activated sludge was determined utilizing aerobi-
cally-digested sludge samples.
37
-------
The activated sludge process requires relatively large
amounts of energy to transfer adequate amounts of oxygen for
carrying out the biological reactions. When these demands exceed
the oxygen transfer capabilities of conventional equipment (dif-
fused air or mechanical surface aeration), the aeration basin
volume is generally increased to balance the oxygen demand-supply
characteristics. As a result, the design and operating charac-
teristics of conventional systems are often dictated by the lim-
itations imposed by oxygen transfer equipment. Deep Shaft bio-
logical reactors are designed to operate with 90 to 250 m (300
to 800 ft) of hydrostatic pressure with oxygenation capacities
between 2/000 and 3,000 mg/L*h. As a result, the design of
Deep Shaft biological reactors is basically dependent on the or-
ganic removal rate and the availability of a consistent source
of recycle biomass. In general, the design of a biological re-
actor involves consideration.of the following:
1. Providing adequate mixing to maintain mixed liquor
solids in suspension, and to improve the opportunity
for contact between biological solids and organics.
2. Providing adequate residence time in the reactor for
achieving the desired removal efficiency.
3. Providing adequate facilities for recycling sludge and
for maintaining the desired mixed liquor volatile
suspended solids concentration.
Mixing in Deep Shaft reactors is accomplished by maintaining
sufficient velocities and turbulence through the shaft (1 to 2
m/s). During startup, the flow inside the Deep Shaft is initi-
ated by injecting air into the riser section. The differential
hydrostatic head, developed due to the voidage difference be-
tween the downcomer and the riser sections, is adequate to ini-
tiate and maintain flow through the shaft. The driving force
(y) required to maintain flow through the reactor is estimated
from the voidage head difference and the friction loss, as fol-
lows:
(voidage head - friction loss)
(3)
In general, the voidage head difference is adjusted by con-
trolling the air injection depth to the downcomer. The air re-
quirements and the air injection depth are usually selected to
maintain forward flow under all conditions (average and peak
flow conditions). For domestic wastewaters (6005 =200 mg/L),
the air flow requirements are primarily dictated by the' required
driving force to maintain flow. In the case of high strength
wastewaters, the air flow requirements may be dictated by the
wastewater's organic strength and oxygen requirements. :
38
-------
The residence time and extremely high pressure (up to 1,520
kPa; 15 atm) available in the lower sections of the Deep Shaft
reactor are sufficient to achieve nearly complete dissolution
of oxygen. For design purposes, it is usually assumed that 90
percent of the oxygen supply goes into solution during passage
through the reactor. This is equivalent to 0.25-kg oxygen for
each cubic meter of"air Injected into the reactor. The total
air requirements for biological oxidation can thus be estimated
from the raw wastewater characteristics and treatment require-
ments.
Optimization studies conducted with air diffusion in Deep
Shaft reactors indicate that, at 90-percent oxygen absorption
efficiency, oxygen demand rates of up to 1 kg/m^.h can be
satisfied with a 135 m (450 ft) deep reactor. In general, an
operating depth of between 100 and 150 m (328 to 492 ft) is
usually selected for design of the Deep Shaft reactors, taking
into consideration the patent regulations on other similar
processes (e.g., U-tube aeration).(2°) Figure 18 shows the
dissolved oxygen and BOD profiles normally anticipated inside
Eco-II or Eco-III reactor systems.
PROCESS CAPABILITIES AND LIMITATIONS
Process Capabilities
Deep Shaft biological reactors have the same process con-
cepts and capabilities as conventional activated sludge systems.
Because of the high mixed liquor volatile solids maintained in
the Deep Shaft reactor, volumetric organic removal rates are
higher than in the equivalent conventional concept. As a.re-
sult, the aeration period is relatively low and is on the order
of 30 to 60 minutes. Based on an average flow-through velocity
of 1 m/s (3.05 ft/sec) inside the Deep Shaft reactor, the aver-
age turnover rate for the mixed liquor is approximately once
every 5 minutes when the reactor depth is 150 m (457 ft).(21)
This circulating turbulent mixed liquor serves as the dilution
medium for the influent waste stream to the reactor. The dilu-
tion factor is a function of the mean residence time (t) of the
influent waste stream in the reactor and the flow-through veloc-
ity inside (v). The dilution factor can be expressed as follows:
R
where:
(H/v)
t
(4)
Qi = Influent waste flow rate in m3/h
39
-------
Mixed Liquor Injection
Head Tank
Liquid Level
75
Percent Travel Through Reactor
100
Head Tank
Liquid Level
Figure 18.
Dissolved oxygen and BOD profile for
Eco-II and Eco-III Deep Shaft reactors
40
-------
QR = Mixed liquor flow rate through the Deep Shaft
in m-Vh
H
= Depth of Deep Shaft in ra
v = Flow-through velocity inside the reactor, m/h
t = Mean residence in the reactor, h
This design feature of the Deep Shaft reactor aids in mini-
mizing the effects of shock loads on system performance.
Even though the flow pattern inside the reactor resembles
plug flow for each passage, the mixed liquor turnover rate and
the external dilution aid the system to approach complete-mix
status, and therefore the system is relatively stable to varia-
tions in influent characteristics. Figure 19 shows the compari-
son in concentration profile within completely mixed, pluq flow
and Deep Shaft reactors. .
Because of the ability of the Deep Shaft reactor to achieve
oxygen transfer efficiencies of up to 90 percent, the system is
suitable for the joint treatment of high-strength industrial and
municipal wastewaters. Similarly, the system is also suitable
for pretreatment of industrial wastewaters.(22, 23,24)
Process Limitations
Because-of the relatively low residence time utilized -in the
design of the Deep Shaft reactors, the system is susceptible to
upsets due to sustained hydraulic peak flows. The Eco-III reac-
tor design recognizes this problem and is equipped with a two-
speed drive mechanism for the float skimmer for adjusting the
recycle sludge flow rate. For the same reason, it is essential
to adequately define the average and maximum flow conditions
during the design of a Deep Shaft reactor.
The Deep Shaft process is more difficult and expensive to
expand than conventional activated sludge processes because of
the cost and time involved in drilling and mobilization of
drilling equipment. Most often, it may be necessary to expand
by doubling the capacity of the existing plant because of the
shaft placement economics.
Even though the process has been tested for use in aerobic
digestion studies, the results of these studies have not been
reported or published for evaluation during this investigation.
Preliminary discussions with Eco-Technology personnel indicate
that successful digestion has been achieved with a digestion
41
-------
200
Q
O
c
ro
s>
o
"o
E
"c
Plug Flow,
Conventional
Completely mixed,
Conventional
1238
Number of Mixed Liquor Turnovers (Deep Shaft)
J.
6 9 24
Mean Residence Time, minutes
27
30
Figure 19,
Comparison of concentration profiles for,
conventional and Deep Shaft reactor systems.
42
-------
*ff
period of 3 to 4 days. From process considerations, the Deep
Shaft system appears suitable for aerobic digestion. However,
the higher digestion rate coefficient (days'*) achieved in
preliminary testing has yet to be demonstrated in a long-term
dedicated facility. It is also necessary to demonstrate that
the Deep Shaft digester can handle solids concentrations in the
range of 7 percent which is the expected float solids concentra-
tion.
OPERATION AND MAINTENANCE CONSIDERATIONS
The Deep Shaft reactor, as shown in Figures 10 and 11, is
very simple in configuration and has no moving parts inside the
shaft. As a result, the requirement for maintenance of the
shaft components themselves is minimal and expected to be less
than those anticipated for conventional activated sludge proc-
esses equipped with air diffusers. The high pressure (790 kPa;
100 psi) compressors used in the Deep Shaft process, however,
will require increased maintenance as compared to the low pres-
sure blowers (<79 kPa) or mechanical surface aerators used in
conventional systems.<23) Similarly, the operation of the
dissolved air flotation process will require additional training
and increased operator monitoring as compared to a gravity sedi-
mentation process.
The Eco-III version of the Deep Shaft reactor has eliminated
most automatic instrumentation and controls, thereby making it
less complicated than conventional processes. This is especial-
ly true with respect to the sludge recirculation system which is
set at a constant rate during normal flow conditions.
Because the Deep Shaft reactors are installed subsurface,
the mixed liquor inside the reactor is not subject to wide sea-
sonal variations in temperature. Therefore, process operating
parameters can be maintained at a steady rate year-round and
less operator attention will be required. A disadvantage of the
Deep Shaft process, however, is the inability to visually ob-
serve mixed liquor contents so that process upsets can be de-
tected immediately.
In general, the Deep Shaft process is not appreciably dif-
ferent from conventional activated sludge systems, and it is not
expected to require any specialized skills. Therefore, the
staffing requirements will be similar to the conventional sys-
tems of equivalent size. Because of this similarity, the Deep
Shaft process may be suitable for expanding existing activated
sludge plants where space restrictions prevail.
43
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COST CONSIDERATIONS
The application of the Deep Shaft wastewater treatment proc-
ess has been demonstrated successfully for the treatment of do-
mestic and industrial wastewaters. This experience is mostly
limited to European and Canadian practice. One 0.46-m (18-in.)
diameter demonstration unit has been installed and has been in
operation in Ithaca, New York since 1979. This system is de-
signed to handle a mixture of industrial and domestic wastewater
and is equipped with facilities to operate either in the sedi-
mentation or the flotation mode.
Based on current experience with the Deep Shaft process, the
major cost element is associated with the installation of the
reactor itself. The fixed cost associated with well drilling
and shaft installation, including electrical, mechanical and in-
strumentation devices, has been estimated to be between 30 and
50 percent of the total project cost.(25'26'27> The cost of
drilling is subject to variation depending on geological condi-
tions, the availability of drilling rigs, and their demand for
other more competitive purposes (e.g., oil well drilling, etc.).
ENERGY CONSIDERATIONS
The major energy requirement in biological wastewater treat-
ment systems is the biological reactor in which the oxygen de-
mand requirements must be supplied from external sources. The
Deep Shaft process is no exception to this requirement, since
the oxygen is supplied using high pressure compressors with dis-
charge pressures of790 kPa (100 psi). The actual energy re-
quirements for a Deep Shaft reactor are governed by the follow-
ing:
1. Organic and hydraulic load for average and peak
conditions.
2. Mixed liquor volatile suspended solids (MLVSS).
3. Air requirements for liquid circulation.
4. Shaft diameter.
In general, shafts smaller than 1m (3 ft) in diameter may
require supplemental air to maintain mixed liquor circulating
velocities in treating normal strength domestic wastewater.(24)
When optimum organic loading conditions "prevail, oxygen transfer
efficiencies up to 6 kg O2/kwh (9.8 Ib O2/ hp)~ can be real-
ized. (7) On the other hand, small diameter shafts treating
weak wastewaters can realize power economies in the range be-
tween 2 and 3 kg 02/kwh (3.3 - 4.9 Ib O2/hp).
44
-------
SECTION 4
f>
COMPARISON WITH EQUIVALENT TECHNOLOGY
EQUIVALENT CONVENTIONAL CONCEPT
The Deep Shaft treatment system is a high rate activated
sludge process in which the shallow aeration basins of 3 to 10 m
(9 to 30 ft) are replaced with deep subsurface reactors of 90 to
250 m (270 to 760 ft). In addition, the North American version
of the Deep Shaft process utilizes dissolved air flotation for
final clarification of mixed liquor suspended solids. In an at-
tempt to select the most suitable equivalent technology, the
conventional activated sludge process and its modifications were
evaluated during initial screening. Upon closer examination of
the various operating parameters, however, the decision was
made to use the enriched oxygen process (pure oxygen) for the
purposes of comparing equivalent technology. Aside from other
similarities, the pure oxygen system is usually designed to
operate with high mixed liquor suspe'nded solids (4,000 to 6,000
mg/L) and with a high dissolved oxygen concentration (5 to 7
mg/L). These design features allow the biosystem to operate
under high organic loadings (F/M) and with reduced aeration
volume similar to those achievable in the Deep Shaft process.
Other similarities between the pure oxygen activated sludge
and the Deep Shaft alternatives include the high oxygen tension
within the bio-reactor and the claimed resultant low waste
sludge generation. A comparative analysis of these design fea-
tures and operating criteria are presented in Table 4 in the
technology evaluation section of this report (Section 3). This
comparison indicates that design criteria such as the nominal
detention time, mixed liquor suspended solids (MLSS), organic
loading, and sludge age are within the same range for the oxy-
gen-activated sludge and the Deep Shaft process. In general,
the comparative analysis of design and operating criteria indi-
cates that the two processes are similar except for the oxygen
utilization efficiency and the return sludge concentration
values. For these reasons, the pure oxygen system was selected
as the equivalent technology for comparison with the Deep Shaft
process. The air-activated sludge process was included in the
evaluation in order to establish a baseline technology in the
comparative analysis. For the 1,892 m3/d (0.5 mgd) facility,
45
-------
conventional activated sludge was used as the baseline technolo-
gy/ wheras high-rate activated sludge was used as the baseline
technology for the 18,925 m3/d (5.0 mgd) and 37,850 m3/d
(10.0 mgd) facilities.
Cost Comparison
The economic analysis of the three different technologies
considered the initial investment cost (capital cost), the annu-
al operation and maintenance cost, and the present worth cost of
the total treatment system. Cost estimates developed by the U. S.
EPA for evaluating innovative and alternative technologies(!'
were used as the primary source for estimating installed capital
and annual operation and maintenance costs for the pure oxygen
and conventional activated sludge processes. These cost esti-
mates were supplemented with cost figures from Appendix H of the
Areawide Assessment Procedures manual to include structural and
nonstructural cost components (e.g., influent pumping or lift
station, and miscellaneous structures such as control and opera-
tions buildings, outfall sewer, etc.).(33)
For the Deep Shaft alternative, the turn-key cost estimates
for the Deep Shaft portion of the facilities were obtained from
Eco Technology. The battery limits for the Deep Shaft portion
included the Deep Shaft reactor(s), flotation separator units,
and the control building for these components. These cost esti-
mates were supplemented with estimates for remaining process un-
its (e.g., sludge handling and treatment, preliminary treatment,
disinfection, influent and effluent structures, etc.) utilizing
the same cost curves as the equivalent and baseline technology
alternatives. All cost estimates were updated to reflect Decem-
ber 1980 construction costs (Engineering News Record Index
3376). The basic assumptions and procedures utilized in esti-
mating construction costs are summarized in Appendix A.
Taking into consideration the current status of development
and experience with the Deep Shaft system, three design flows
were selected for comparison. The three design flows are:
1. 1,892 m3/d ( 0.5 mgd)
2. 18,925 m3/d ( 5.0 mgd)
3. 37,850 m3/d (10.0 mgd)
For the Deep Shaft system, Eco Technology provided turnkey
cost estimates for 1,892, 18,925, and 189,250 m3/d (0.5-,
5.0-, and 50-mgd) capacities. These cost estimates, together
with updated bid estimates for three full-scale Canadian plants
(Virden, Molson Breweries, and Portage La Prairie)f were used as
46
-------
the basis for estimating Deep Shaft system costs for the 37,850
m-Vd (10.0 mgd) plant size. The design data and fact sheets
for these facilities are included in Appendix B. Tables 7, 8,
and 9 show the results of cost evaluations for the three sys-
tems. All capital cost estimates reflect December 1980 cost
figures (Engineering New Record Index 3376).
Energy Requirements
An approach similar to that utilized for the cost compari-
son was used for estimating the energy requirements for the
three different technologies. All information relative to oper-
ations within the battery limits of the Deep Shaft system was
obtained from the Eco Technology personnel. The energy require-
ments for operations outside the battery limits of vendor-sup-
plied components were estimated utilizing the EPA-developed in-
formation for evaluating innovative and alternative technolo-
gies. The analyses of energy requirement are summarized in Ta-
bles 10, 11, and 12.
Land Area Requirements
One of the significant advantages of the Deep Shaft system
is the reduced land area requirement as compared to the conven-
tional air or pure oxygen activated sludge systems. This fea-
ture makes the Deep Shaft system especially attractive for con-
sideration in land restricted areas, and in expanding existing
facilities where land availability is limited. Figure 20 shows
the relative land area requirements for the Deep Shaft and con-
ventional air-activated sludge systems. Based on the design
criteria presented in Table 4, it is likely that the land area
requirements for the pure oxygen-activated sludge system will
be similar to the conventional air-activated sludge process.
This is due to the fact that any space reductions realized in
aeration tank sizing will be compensated by the additional area
required for installing oxygen supply equipment.
47
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TABLE 7. COST COMPARISON -- 1,892 m3/d (0.5 mgd) FACILITY*-
Process Unit
Low-lift pumping
Preliminary treatment
Aeration/clarifi-
cation
Disinfection
(chlorination)
Gravity outfall
Aerobic digestion
Vacuum filtration
Sludge hauling and
landfilling
Miscellaneous
structures
Conventional
Activated
'Sludge
(Baseline)
$ 171,000
40,900
'464,000
54,600
Pure
Oxygen
(Equivalent)
$ 171,000
40,900
896,000
54,600
68,200
68,200
Deep Shaft
$ 171,000
40,900
900,OOO2
54,600
218,000
239,000
273,000
131,000
., 218,000
164,000
273,000 !
131,000
218,000
81,800
273,000
131,000
68,200
Subtotal
Noncomponent costs-^
Engineering, con-
struction supervision
Contingency
Total installed
capital cost
Annual operation
and maintenance
costs
Present worth
SI, 659, 700
465,000
319,000
319,000
$2,762,700
$ 175,000
$4,563,800
' $2,016,700
565,000
387,000
387,000
$3,355,700
$ 184,500
$5,254,600
$1,038,5004
291, OOO4
199, OOO4
199, OOO4
$2,627,500
$ 200,000
$4,685,000
cost^
Appendix A for details of assumptions used in the cost analy-
sis.
^Turnkey cost, including noncomponent costs, engineering, construc-
tion supervision, and contingency.
3Noncomponent costs include piping, electrical, instrumentation, and
site preparation.
4Exclusive of Deep Shaft costs which are turnkey costs.
^Present worth computed assuming 20-year life at 7-3/8% interest
rate (PWF = 10.29213).
48
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TABLE 8. COST COMPARISON --18/925 m3/d (5.0 itigd) FACIBITV1
Process Unit
Low-lift pumping
High-Rate
Activated
Sludge
(Baseline)
$. 614,000
Preliminary treatment 171,000 .
Primary clarifier
Aeration/clarifi-
cation
Disinfection
(chlorination)
Gravity outfall
DAP thickening
Anaerobic digestion
Vacuum filtration
Sludge hauling and
landf illing
Miscellaneous
structures
Subtotal
Noncomponent costs^
Engineering, con-
struction supervision
Contingency
Total installed
capital cost
Annual operation
and maintenance
costs
Present worth
382,000
lVl'32,000
140,000
709,000
171,000
546,000
464,000
185,000
232,000
$4,746,000
1, 330, 000
911,000
911,000
$7,898,000
$ 459,200
$12,624,000
Pure
Oxygen
(Equivalent)
$, 61,4,000
171,000
382,000
2,956,000
140,000
709,000
171,000
546,000
464,000
185,000
232,000
$6,570,000
1,840,000
1,260,000
1,260,000
$10,930,000
$ 498,900
$16,065,000
Deep Shaft
3 614,000
171,-000
'
3,300,000?
140,000
709,000-
423,000
464,000
185,000
232,000
32, 938, OOO4
823, OOO4
564, OOO4
'564, OOO4
$8,189,000
$ '513,400
$13,473,000
cost^
Appendix A for details of assumptions used in cost analysis.
2Turnkey cost, including noncomponent costs, engineering, construc-
tion supervision, and contingency. -,-.,
3Noncomponent costs include piping, electrical, instrumentation, and
site preparation.
4Exclusive of Deep Shaft costs which are turnkey costs. ' >; ;
5Present worth computed assuming 20-year life at 7-3/8% interest
rate (PWF = 10.29213).
49
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TABLE 9. COST COMPARISON -- 37,850 m3/d (10 mgd) FACILITY1
Process Unit
Low-lift pumping
Preliminary treatment
Primary clarifier
Aeration/clarifi-
cation
Disinfection
(chlorination)
Gravity outfall
DAF thickening
Anaerobic digestion
Vacuum filtration
Sludge hauling and
landfilling
Miscellaneous
structures
Subtotal
Noncomponent costs-^
Engineering, con-
High-Rate
Activated
Sludge
(Baseline)
$ 955,000
259,000
573,000
1,773,000
273,000
1,090/000
205,000
791,000
614,000
235,000
327,000
$7,095,000
1,990,000
1,360,000
Pure
Oxygen
(Equivalent)
$ 955,000
259,000
573,000
4,265,000
273,000
1,090,000
205,000
791,000
614,000
235,000
327,000
$9,587,000
2,684,000
1,840,000
Deep Shaft
$ 955,000
259,000
-.
5,600,0002
273,000
1,090,000
-
436,000
614,000
235,000
327,000
$4,189,0004
1,170,.0004
804,'0004
struction supervision
Contingency
1,360,000
1,840,000
Total installed
capital cost $11,805,000
Annual operation
and maintenance
costs $ 714,800
Present worth
cost^
$19,162,000
804,OOO4
$15,951,000 $12,567,000
$ 768,000 $ 699,200
$23,855,000 $19,763,000
Appendix A for details of assumptions used in cost analysis.
2Turnkey cost, including noncomponent costs, engineering, construc-
tion supervision, and contingency.
3Noncomponent costs include piping, electrical, instrumentation, and
site preparation.
^Exclusive of Deep Shaft costs which are turnkey costs.
50
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TABLE 10. ENERGY ANALYSIS (kWh/y)--
If892 m3/d (0.5 mgd) FACILITY1
Process Unit
Low-lift pumping
Preliminary treatment
Aeration/clarifi-
cation
Disinfection
(chlorination)
Gravity outfall
Aerobic digestion
Vacuum filtration
Sludge hauling and
landfilling
Total kWh/y
Energy utilization,
kWh/km3
kg BOD5 removed/kWh
Conventional
Activated
Sludge
(Baseline)
9,000
14,000
195,000
5,000
Pure
Oxygen
(Equivalent)
9,000
14,000
45,0002
5,000
Deep Shaft
9,000
14,000
268,000
5,000
90,000
62,500
53,100
428,600
621
90,000
62,500
53,100
278,600
403
90,000
62,500
53,100
501,600
726
0.274
0.422
0.234
-See Appendix A for details of assumptions used in cost analysis.
^Assumes purchase of liquid oxygen.
51
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TABLE 11. ENERGY ANALYSIS (kWh/y)--
18,925 m3/d (5.0 mgd) FACILITY1
Process Unit
Low-lift pumping
Preliminary treatment
Primary clarifier
Aeration/clarifi-
cation
Disinfection
(chlorination)
Gravity outfall
DAF thickening
Anaerobic digestion
Vacuum filtration
Sludge hauling and
landf illing
Total kWh/y
Energy utilization,
kWh/km3
High-Rate
Activated
Sludge
(Baseline)
90,000
17,500
45,000
565,000
11,000
Pure
Oxygen
(Equivalent)
90,000
17,500
45,000
765,000
11,000
Deep Shaft
90,000
17,500
2,450,000
: 11,000
130,000
20,000
62,500
350,000
1,291,000
187
130,000
20,000
62,500
350,000
1,491,000
216
13,500
62,500
350,000
2,994,500
434
kg
removed/kWh
0.911
0.789
0.393
3-See Appendix A for details of assumptions used in cost analysis.
52
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TABLE 12. ENERGY ANALYSIS (kWh/y)--
37,850 m3/d (10 mgd) FACILITY1
Process Unit
Low-lift pumping
Preliminary treatment
Primary clarifier
Aeration/clarifi-
cation
Disinfection
(chlorination)
Gravity outfall
DAF thickening
Anaerobic digestion
Vacuum filtration
Sludge hauling and
landfilling
Total kWh/y
Energy utilization,
kWh/km3
kg BOD5 removed/kWh
High-Rate
Activated
Sludge
(Baseline)
180,000
21,800
77,000
1,400,000
12,500
Pure
Oxygen
(Equivalent)
180,000
21,800
77,000
1,400,000
12,500
Deep Shaft
180,000
21,800
3,400,000
12,500
250,000
40,000
110,000
701,000
2,792,300
202
250,000
40,000
110,000
701,000
2,792,300
202
-
24,000
110,000
701,000
4,449,300
322
0.842
0.842
0.529
Appendix A for details of assumptions used in cost analysis.
53
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Conventional Air
Activated Sludge
15,000
30,000 45,000
Plant Size, m3/d
60,000
75,000
Source of Data: Reference No. 5
Figure 20. Land area requirements for conventional
air-activated sludge and Deep Shaft
aeration process.
54
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SECTION 5
NATZONAL IMPACT ASSESSMENT
MARKET POTENTIAL
A review of the "1978 Needs Survey for Conveyance and Treat-
ment of Municipal Wastewaters" indicates that the current sec-
ondary treatment technology can be classified into three major
categories, as follows:
1. Trickling filter and its modifications.
2. Activated sludge and its modifications.
3. Other processes, including rotating biological
contactors, oxidation ditches, etc.
The Needs Survey data on a number of wastewater treatment
plants indicate that there is an increasing trend toward the use
of the activated sludge process, or its modifications, for
plants under construction and those yet to be funded. A similar
trend was observed for the total wastewater flow requiring
treatment. These data are summarized in Tables 13 and 14. There
are approximately 10,861 wastewater treatment plants currently
in use or under construction in the United States. An additional
7,775 treatment facilities will be required between 1978 and
2000 to treat approximately 49 x 10^ m3/d (12,974 mgd) of
wastewater flow. This represents an average daily flow per fa-
cility of approximately 6,320 m3/d (1.66 mgd). In addition,
the Needs Survey data indicate that between 80 to 90 percent of
these facilities will be utilizing some form of the activated
sludge process. Based on this analysis, it is evident that ac-
tivated sludge is by far the most prevalent treatment technology,
both in. terms of the number of facilities and the volume of
wastewater flow.
The Deep Shaft biological treatment process utilizes the
same principles as the activated sludge process, and, therefore,
has the potential to capture a portion of the future treatment
needs. The market potential which can be realized by the Deep
Shaft technology will depend to a large extent on the develop-
ment and publication of reliable cost, performance, and energy
data.
55
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TABLE 13. WASTEWATER TREATMENT PROCESS PROFILE1--
NUMBER OF FACILITIES
Process Now
Category in Use
Trickling filter 2,863
and its modifica- (28. 8) 2
tions
Activated sludge and 6,670
its modifications (67.1)
Other(s)3
Total
408
(4.1)
9,941
Under
Construction
88
(9.6)
662
(71.9)
170
(18.5)
Required
Not Funded
200
(2.6)
6,673
(85.8)
902
(11.6)
920
. 7,775-
Source: 1978 Needs Survey
^Represents number of wastewater treatment facilities.
^Values in parentheses represent percent of total for each
category. .-...
^Includes rotating biological contactors (RBC), oxidation
ditches, etc.
56
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TABLE 14. WASTEWATER TREATMENT PROCESS, PROFILE1
FLOW TO BE TREATED
Process
Category
Trickling filter
and its Codifica-
tions
% Total
NOW
in Use
17,093 .
(4,484)
Under
Construction
1,107
(291)
Required
Not Funded
4,985
(1,315.)
(15.2)
Activated sludge and 94,313
its modifications (24,912)
% Total
Other(s)2
% Total
Total
84.1
779
(205)
0.7
112,185
(29,601)
(8.2)
11,175
(2,950)
82.9
1,197
(316)
8.9
13,479
(3,557)
(10.1)...
39,907
(10,541)
81.2
4,237
(1,118)
8.7
49,129
(12,974)
Source: 1978 Needs Survey
-^Represents wastewater flow data in.10^ m-^/d and mgd >(in
parentheses)... ,.
2Includes rotating biological contactors (RBC), oxidation
ditches,
etc.
-------
In general, because of its design and operating characteris-
tics, the greatest market potential for the Deep Shaft process
is for the treatment of high strength wastewaters (BODs > 500
rag/L) . Therefore, there is greater potential for the use of the
Deep Shaft process in POTW's treating joint industrial and do-
mestic wastewaters. In addition, the potential for the Deep
Shaft process is high at locations where space restrictions pre-
vail as the system requires less space than conventional or high
rate activated sludge systems.
COST AND ENERGY IMPACTS
Based on the cost and energy requirements analysis (Tables 7
through 12), no definitive conclusions could be drawn relative
to cost or energy savings that can be realized by use of the
Deep Shaft process. For the plant capacities used in the cost
analysis (1,892-37,850 m3/d; 0.5 to 10.0 mgd), the installed
capital cost estimates for the Deep Shaft process were equiva-
lent (+ 25%) to the conventional air-activated sludge process
as they are within the accuracy of the estimating procedure.
The Deep Shaft process showed some savings in installed capital
costs over the pure oxygen-activated sludge system for all of
the flow ranges for which the comparative analysis was prepared.
When the cost comparison is based on present worth value, all
three technologies are found to be equivalent. Based on this
evaluation, no significant national impacts can be predicted
for the Deep Shaft process.
A similar analysis was conducted for the energy requirements
of the three technologies (Tables 9 through 11) . Based on this
analysis, it can be concluded that the unit energy requirements
(kWh/1,000 m3 of wastewater treated) are the highest for the
Deep Shaft process when treating domestic wastewaters. The pure
oxygen-activated sludge process required the least unit energy
for the 1,892 m3/d (0.5 mgd) plant size because of the use of
purchased liquid oxygen. For larger plant capacities (.18,925
and 37,850 m3/d), however, the pure oxygen process required
the same unit energy as the conventional air-activated sludge
process. This was due to the requirement for additional energy
for on-site oxygen generation.
When the energy use comparison was made on the basis of
BODs removal (kg BODs/kWh), a similar conclusion is reached
indicating that the pure oxygen-activated sludge process is fa-
vored for the 1,892 m3/d (0.5 mgd) plant size over the other
two technologies. However, when the on-site oxygen generation
equipment is incorporated, the energy benefits for the pure oxy-
gen process are nullified.
58
-------
Based on this analysis, it is evident that the Deep Shaft
process benefits (cost and energy) can only be realized when the
raw wastewater strength is greater than normal domestic wastewa-
ter. This is because the energy requirements for the Deep Shaft
process treating domestic wastewaters. _are based on the require-
ment for maintaining liquid circulation velocities rather than
on the basis of BOD5 removal. When the raw wastewater 8005
concentration is high (>500 mg/L), the cost and energy savings
are likely to be in favor of the Deep Shaft process.
RISK ASSESSMENT
The Deep Shaft biological treatment process is conceptually
identical to the conventional air-activated sludge and the pure
oxygen-activated sludge processes. A review of the more recent
design practices, however, indicates that the Deep Shaft process
for domestic wastewater treatment has a nominal detention time
between 30 and 60 minutes. This detention time approximates the
mean generation time of organisms typically present in the acti-
vated sludge. As a result, variations in influent flow rate are
likely to shift the population dynamics of the activated sludge
culture. In the design of conventional air- and pure oxygen-ac-
tivated sludge systems utilizing primary gravity sedimentation, a
minimum detention time of two hours is utilized to prevent shifts
in population dynamics, and to preserve the settling character-
istics of the mixed liquor suspended solids. In other words, a
minimum detention time of two hours is necessary to maintain the
biological integrity of the conventional system. The impact of
the lower detention time (30 to 60 min) for the Deep Shaft proc-
ess and the downstream flotation separator cannot be assessed at
this time, and therefore, constitutes a potential risk with re-
spect to the performance of the Deep Shaft process.
59
-------
REFERENCES
1. Innovative and Alternative Technology Assessment Manual.
EPA-430/9-78-009, U.S. Environmental Protection Agency, Cin-
cinnati, Ohio, 1980.
2. Smith, J.M., McCarthy, J.J., and H.L. Longest. Impact of Innovative
and Alternative Technology in the United States in the 1980's.
Municipal Environmental Research Laboratory, U.S. Environ-
mental Protection Agency, Cincinnati, Ohio, 1980.
3. Shere, S.M., and P.G. Daly. Deep Shaft Treatment of Thermo-
mechanical Pulping Effluents. Presented at: Canadian Pulp
and Paper Association, Environment Improvement Conference,
Quebec City, Quebec, Canada, 21-23 October 1980.
4. Sanford, D.S., and J.J. Faria. Application of Deep Shaft
Technology to Food Processing Wastes. Eco-Research Ltd.,
Toronto, Ontario, Canada.
5. Sanford, D.S., and D.A. Chisholm. The Treatment of Munici-
pal Wastewaters Using the ICI Deep Shaft Process. In: Pro-
ceedings of the 29th Annual Western Canada Water and Sewage
Treatment Conference, Edmonton, Alberta, Canada, 1977.
6. Dunlop, E.H. Characteristics of Sludge Produced by the Deep
Shaft Process. Reprint from the Society of Chemical Indus-
try, New Processes of Wastewater Treatment and Recovery Con-
ference, Belgrave Square, London, 1977.
7. Bailey, H.M., J.C. Ousby, and F.C. Roesler. ICI Deep Shaft
Aeration Process for Effluent Treatment. In: Proceedings
of the Institution of Chemical Engineers symposium, Series
No. 41, 1975.
8. Bradley, B.J. ICI Deep Shaft Effluent Treatment Process.
In: Proceedings of the 29th Annual Atlantic Canada Section,
AWWA Meeting, hosting the 6th Annual FACE Meeting, Halifax,
Nova Scotia, Canada, 1976.
9. Brenner, R.C., and J.J. Convery. Status of Deep Shaft
Wastewater Treatment Technology in North America. In: Pro-
ceedings, 7th United States/Japan Conference on Sewage
Treatment Technology, Tokyo, Japan, 1980.
60
-------
10. Bolton, D.H., D.A. Hines, and J.P. Bouchard. The Applica-
tion of the ICI Deep Shaft Process to Industrial Effluents.
In: Proceedings of the 31st Annual Purdue Industrial Waste
Conference, Lafayette, Indiana, 1976.
11. Dick, R.I. Folklore in the Design of Final Settling Tanks.
Journal of the Water Pollution Control Federation, 48, 4
April 1976.
12. Gallo, T., and D.S. Sanford. The Application of Deep Shaft
Technology to the Treatment:' of High Strength Industrial
Wastewaters. In: Proceedings of the American Institute of
Chemical Engineers' 86th Annual Meeting, Houston, Texas,
1979.
13. Knudsen, F.B., B.P. Kuslikis, D.C. Pollock, and M.A. Wilson.
The Application of the ICI Deep Shaft Process to the Treat-
ment of Brewery Effluents. In: Proceedings of the 6th An-
nual W.W. E.M.A. Conference, St. Louis, Missouri, April 1978,
14. Knudsen, F.B. Brewery Effluent Treatment by a Deep Shaft
Process. Brewers Digest, May 1978.
15. Metcalf and Eddy, Inc. Wastewater Engineering: Treatment,
Disposal, Reuse. McGraw Hill Book Co., New York, 1979.
16. Eckenfelder, W.W. Principles of Water Quality Management.
CBI Publishing Company, Inc., Boston, Massachusetts, 1980.
17. New Units Groomed for Sewage, Garbage.
Processing, 5 February 1979.
Canadian Chemical
18. Appleton, B. Id's Deep Shaft "Halves Sludge Volume." New
Civil Engineer, 17 April 1975..
19. Eco-Research, Ltd. Ithaca Deep Shaft, Visitor's Program.
Eco-Research, Ltd., P.O. Box 200, Station A, Willowdale,
Ontario, Canada, 1980.
20. Speece, R.E. Energy Efficiency of Deep U-Tube Aeration.
Proceedings of the Department of Energy, Energy Optimization
of Water and Wastewater Management for Municipal and Indus-
trial Applications Conference, Argonne National Laboratory,
Argonne, Illinois, 1979.
21. Appleton, B. Thurrock, Test-bed for ICI Deep Shaft.
Civil Engineer, 14 April 1977.
New
22. The ICI Deep-Shaft Effluent Treatment Process.
Digest, 36, 5, May 1975.
Engineers'
61
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23. The Deep-shaft Process: Bright Future for Treating High-
Strength Wastewaters. Civil Engineer.ing-ASCE, 51, 5 May
1981.
24. Bouchard, J.P., F.B. Knudsen, S. Lessard, and L.W. Keith.
North American Application of the Deep Shaft Effluent Treat-
ment Process. Proceedings of the 50th Annual Conference,
WPCF, Philadelphia, Pennsylvania, 2-7 October 1977.
25. City of Portage La Prairie. Comparison of Extended Aeration
and Deep Shaft Sewage Treatment Plants. Prepared by: W.L.
Wardrop & Associates Ltd., Engineering Consultants, Canada, ,
June 1977.
26. City of Portage La Prairie Sewage .Treatment. Submission to:
The Clean Environment Commission, Canada, 19 June 1978.
27. Thompson, G.E. Selection of Deep Shaft Technology for the
City of Portage La Prairie, Manitoba. In: Proceedings of
the Workshop 79, New Developments in Wastewater Treatment,
University of Toronto, Toronto, Canada, 7-8 March 1979.
28. Deep Shaft System Uses GRP,
uary 1978. 25 pp.
Water and Waste Treatment, Jan-
29. Commissioning and Operation of Deep Shaft Demonstration
Plant. Ithaca, New York-Abstract. Prepared by: Eco-Re-
search Limited, Willowdale, Ontario, Canada, 1980.
30. Molson's Deep Shaft Effluent Treatment System. Prepared by:
Eco-Research Limited, Willowdale, Ontario, Canada, 1980.
31. Deep Shaft Effluent Tretament Plant-Design Brief, Town of
Paris, Ontario, Canada. Prepared by: Eco-Research Ltd;
Willowdale, Ontario, Canada, September 1980.
32. Brenner, R.C. Status of Novel Biological Process Develop-
ment in the United States. In: Proceedings of the Interim
Technical Seminar Between Seventh and Eighth U.S./Japan Con-
ferences on Sewage Treatment Technology, Tokyo, Japan, 15
May 1981.
33. Areawide Assessment Procedures ManualAppend is? H, Point
Source Control Alternatives: Performance and Cost. U.S.
Environmental Protection Agency, MERL, Cincinnati, Ohio,
July 1976.
62
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APPENDIX A
COST AND ENERGY ANALYSIS ASSUMPTIONS
In order to compare the various alternatives, a basis for
the cost comparison was required. The major sources of cost
(capital, and operations and maintenance) and energy require-
ment data were the Innovative and Alternative Technology Assess-
ment Manual (I&A)(!)with additional input from the Areawide
Assessment Procedures Manual, Appendix H(33), and Eco Technolo-
gy.
In order to accommodate the specific design conditions, num-
erous assumptions were required to adjust and extrapolate cost
data which will reflect the specific design case. The assump-
tions utilized for technology evaluation are as follows:
1. Construction costs were updated to fourth quarter
1980 utilizing the Engineering News Record Index,
ENR = 3376.
2. Operation and maintenance costs were updated to
fourth quarter 1980 utilizing EPA's Average O&M -
Index = 3.04.
3. Construction costs were upgraded to capital costs
by inclusion of noncomponent costs. The noncom-
ponent costs and the percentage of construction
costs used are as follows:
Piping - 10%
Electrical - 8%
Instrumentation - 5%
Site Preparation - 5%
4. Engineering services and contingency costs were
each assumed to be 15% of the capital cost. The
sum of the construction costs, noncomponent
costs, engineering services, and contingency
yielded the total installed capital cost.
63
-------
5. For the 1872 m3/d (0.5 mgd) plant size uti-
lizing conventional air (baseline) or pure
oxygen (equivalent) activated sludge process
to account for differences in the design be-
tween the I&A Manual and the work reported
herein, the I&A Manual curves were appropriately
modified to reflect the following:
a. The exclusion of the primary clarifier
resulted in a higher BOD5 loading to
the activated sludge process (200 mg/L ver-
sus 130 mg/L).
b. Differences in influent feed sludge con-
centration to the aerobic digester (1 per-
cent vs. 4 percent solids).
6. For all three plant sizes utilizing the Deep
Shaft process, the costs obtained from Eco
Technology were assumed turnkey, and zero non-
component, engineering services, and contingency
costs were assumed to be associated with the
Deep Shaft portion of the total cost.
7. For all three Deep Shaft process designs, modifi-
cations to the I&A Manual costs for digestion were
required to reflect the concentration of solids
obtained from the flotation cell. For the 1,892
m3/d (0.5 mgd) case, these modifications were
made to the aerobic digester curves, whereas for
the 18,925 m3/d (5.0 mgd) and the 37,850 m3/d
(10 mgd) designs, modifications were made to the
anaerobic digester curves. These corrections were
required to correct for the 7-percent solids pro-
duced by the flotation unit.
8. For 18,925 m3/d (5.0 mgd) and 37,850 m3/d (10.0
mgd) anaerobic digesters, digester gas was assumed
to be combusted in order to heat the primary di-
gester. No cost or energy credit was given for any
excess gas.
9. For all nine process and size alternatives,
sludge transport by truck, to ultimate disposal,
of 6.2 km (10 miles) one way was assumed. Ap-
propriate assumptions as to sludge generation
rates and dewatered sludge concentrations were
made to allow for sludge volume calculations.
Energy requirements were modified from data pre-
sented in the I&A Manual.
64
-------
10. For present worth analysis, all equipment was
assumed to have a 20-year service life (zero
salvage or replacement cost over cost-effective-
; ness time period), and present worth was equal
to sum of capital cost plus present worth of
annual O&M. costs.
65
-------
APPENDIX B
DESIGN DATA AND FACT SHEETS
(Source: Eco Technology)
66
-------
I Technical
Profile
Virden
Plant
UJ
UJ
Plant enclosure is economical.
practical and aesthetically pleasing.
The Town of Virden. Manitoba, Can-
ada, is the site of the first full-scale
Deep Shaft plant in North America. The
Town of Virden is a petroleum service
centre and agricultural community with
a population of 5,000 people. The town
is located approximately 288 km (180
miles) west of Winnipeg on the Trans-
Canada Highway. The plant is de-
signed to treat approximately 2271 m3
per day (0.6 USMGDJ.of municipal
strength effluent to secondary treat-
ment discharge requirements.
Conventional funding for the proj-
ect was provided by three levels of gov-
ernment. The Canadian government
provided funding through the Canada
Mortgage and Housing Corporation
(CMHC) and the Prairie Farm Rehabili-
tation Administration (PfRA). Provincial
and Civic funds were obtained from
the Manitoba Water Services Board
and the Town of Virden.
Reid Crowther & Partners Limited
in Winnipeg, Manitoba are principal
consulting engineers on the project.
Eco-Research Limited provided the
Deep Shaft secondary treatment plant
on an installed basis at a firm price to
the Town of Virden.
The Deep Shaft process was se-
lected because:
the plant could be built at a
lower capital cost than other
alternatives.
the entire facility could be en-
closed, an important factor due
to 40° C winter ambient temper-
atures and.
» the Town of Virden received in-
centives in the form of a firm price
for an installed plant coupled with
performance and operating cost
warrantees.
The plant is totally enclosed in
a building requiring approximately
465 m2 (5,000 ft2). The process in-
cludes coarse screening, a small surge
tank, grit removal, Deep Shaft aeration.
Prefabricated components allowed
rapid installation.
solids separation by flotation and ef-
fluent chlorination. Waste biological so-
lids are thickened in an existing Imhoff
tank prior to disposal at an approved
sanitary landfill site. The building also
includes a control room, laboratory,
chlorine room, plus compressor and
chemical storage areas. The plant is
also equipped with chemical mixing
and feed systems to allow the addition
of chemical flotation aids if required.
Biological aeration is achieved in
a single shaft 762 mm in diameter and
153 m deep (30" I.D.xSOO'). The
shaft is cased with steel and grouted
to the geological formation with con-
crete. Shaft placement was completed
in one month using a conventional
truck mounted drilling rig.
Three flotation tanks operating in
parallel, result in a high quality effluent
containing less than 30 mg/l 800s and
30 mg/l TSS. The flotation process con-
centrates waste activated sludge to 5%
which greatly reduces the volume of
sludge for disposal.
The Town of Virden Deep Shaft
plant was commissioned in early 1980
at a total project cost of approximately
$1.3 million (1979 Canadian).
67.
-------
I Technical
Profile
Vlrd.n Plant
Design criteria and
operating parameters
Deop Shaft
bioraictor
Flotation
clarification
Parameter
Average daily flow (AOF)'
Instantaneous peak flow"
BODs loading at ADF
MLSS
MLVSS
F/M ratio at ADFC
Volumetric loading"
Detention time*
Nominal
Actual
Sludge retention time1
Aeration Energy
Surface overflow rate"
(Hydraulic loading)
Mass loadings
Return sludge flow rate
Float recycle
Sink recycle
Return sludge
concentration
Float solids
Sink solids
Waste activated sludge"
US Units
0.6 USMGO
1.8USMGD
1000ib/day
0.8%
0.6%
1 .06 day-1
396.5lbBOOs/day/1000ft3
41 min
35 min
1.9 days
40 hp
476USGPD/ft2
31.8lb/day/ft2
16%
Variable
5%
Variable
425 IbVSS/day
0.69 IbTSS/lbBODs
0.5 IbVSS/lbBOO?
SI Units
2271 m3/day
6813 m3/day
453.5 kg/day
8000 mg/l
6000 mg/l
1 ,06 day-1
6.4 kg BOD5/ day /rin3
41 min
35 min
1.9 days
30 kW
19.4 m3/day/m2
155.3 kg/day/m2
16%
Variable
50, 000 mg/l
Variable
193kgVSS/day
0.69 kg TSS/kg BODs removed
0.5 kg VSS/kg BODs removed
Design flow based on a population of 5000 with 120 USGPCO
Based on a Harmon formula - peak flow-3 times average flow.
P/M ratio assumes an influent BODs concentration of 200 ppm,
and a MLVSS content of 75% within the deep shaft and head
tank.
Loading based on head tank and deep shaft volume.
Aciual detention time based on float and sink recycle rates of
16% and 0% respectively,
SRT defined as kg MLVSS m deep shaft bioraactor and head tank
per kg VSS wasted as activated sludge, plus VSS lost in effluent
per day.
Flotation tank loadings based on Internal tank dimensions and
average daily (low influent rata
Activated sludge wasted based on average 600s concentra-
tions of 200 ppm and 30 pom in the influent and effluent.
respectively.
68
-------
I Technical
Profile
CO
Ithaca
Plant
llhaca Deep Shaft plant :s totally
enclosed.
The Ithaca Deep Shaft Demonstration
Plant was assisted by a $500,000 re-
search and develooment grant from the
USEPA Municipal and Environmental
Research Laboratory in Cincinnati,
Ohio. Stearns & Wheler, Investigating
Officers for the USEPA are responsible
for supervising plant operations, eva-
luating the Deep Shaft process for per-
formance and preparing a final report
for submission to the USEPA. The City
of Ithaca provides qualified operating
and analytical personnel to operate the
plant during a 64 week evaluation pro-
gram. Eco-Research assumed responsi-
bility for construction and commis-
sioning of the Deep Shaft Demon-
stration Plant.
The plant is unique in that two
Deep Shaft process flowsheets are in-
tegrated into the same plant. The pro-
cess can be operated in both flotation
and sedimentation clarification modes.
Emphasis is placed upon operating the
plant in the flotation clarification mode
at an average daily flow of 757 m3 per
day (200,000 USGPO). The process is
designed to produce an effluent con-
taining'not greater than 30 mg/l total
BODs and 30 mg/ITSS, The plant was
commissioned in October, 1979 and
operating results confirm that the pro-
cess produces specification effluent.
Consideration is being given to a full
scale Deep Shaft plant at the existing
site.
Biological treatment is performed
in a single shaft 136 m (446') deep
which is cased its full length with a
438 mm (17.25")l.D. casing grouted
to the geological formation with con-
crete. Solids separation is achieved in a
flotation clarifier 3.43 m widex 10.7 m
long and 3.96 m deep (11.25x36x
13 ft). Treated effluent and waste solids
Ithaca flotation cell clartfierdnven
by dissolved gases of Oaep Shaft
are returned to the City of Ithaca's ex-
isting secondary effluent treatment
plant.
Initial results from Ithaca have
confirmed the Deep Shaft as an innova-
tive technology with the potential to
significantly reduce life cycle costs
and/or energy requirements for publi-
cally or industrially owned wastewater
treatment plants.
69
-------
I Technical
Profile
Ithaca Plant
Design criteria and
operating parameters
Deep Shaft
bioreactor
Solids
separation unit
Parameter
Nominal design flow
MISS
SKT*
F/M"
Volumetric loading0
Detention time":
Nominal
Actual
Surface overflow rate
Mass loading'
Return sludge flow rate:
Floa! recycle
Sink recycle
Return sludge
concentration:
Float solids
Sink solids
Waste activated sludge':
Units
mVday
USGPO
mg/l
days
days-1
kg BODs/day/m3
IbsBODs/day/IOOOft3
minutes
rrvVday/m2
USGPO/ft2
kgTSS/day/m2
lbsTSS/day/-ft2
% of nominal
Design flow
%TSS
IbTSS/day
kgTSS/day
kg TSS/kg BODs removed
kg VSS/kg BODs removed
Flotation
Clarification
mode
757
200.000
10,000
2.1
.74
S.54
346
39
24
20.1
494
321
66
20
40
7-10
3-4
170
77
.75
.45
Sedimentation
Clarification
mode
379
100,000
5,000
2.1
,74
2.77
173
78
39
10.1
247
103
21
N/A
100
N/A
1-2
85
38.5
.75
.45
SRT defined as kg MUSS in bioreactor par kg TSS wasted as acti-
vated sludga plus loss in the effluent per day
r/M loading assumes an influent BOOs concentration of 150
mg/l and a MWSS content of 75 per cant.
Volumetric organic loading estimated assuming an influent
800s o* 150mg/Ua MWSS contontof 75 percent, a nominal
shah diameter of .44 m (7.25 mj, and a shaft depth of 136 m
(446 ft).
Actual detention time based on sludge recycle rates of 100 per
cent in the gravity clarification mode and 20 per cent and 40
per cant, respectively, for float solids and bottom solids in the
Flotation clarification mode.
Mass loadings ara based on total sludge return rates of 60 and
100 per cent and MLSS concentrations of 10.000 and 5.000
mg/t, respectively, in the flotation and gravity clarification
modes.
Activated sludge wasted per unit of BOOs removed based on
an influent BOOs of 150 mg/t and an effluent BOOs of 1 5
mg/L.
70
-------
M olson's
Brewery
Plant
External view of Deep Shaft plant
requiring 625 m2 (6700 ft1).
Deep Shaft pilot studies conducted at
Molson's Brewery (Ontario) Limited at
Barrie, Ontario. Canada from 1976 to
1978, resulted in the construction of
a full scale Deep Shaft facility at the
same site. The full-scale plant is de-
signed to treat 2.091 m3 per day (.552
USMGD) of high strength brewery ef-
fluent to direct discharge standards of
50 mg/l BODs and 50 mg/l TSS. The
average daily organic load to this Deep
Shaft plant is 5.000 kg total BODs per
day (11.000 Ibs BOOsperday).
The Deep Shaft plant at Barrie
has two 1.37 m O.D. (54") cased
bioreactors, each placed to a depth of
153m (500'). The Deep Shaft is
grouted with concrete to the surround-
ing geological formation. Shaft inter-
nals are of multi-channel design which
allows influent injection and mixed li-
quor removal from the shaft at depth.
Brewery effluent is split between
an existing extended aeration plant and
the new Deep Shaft system. The brew-
ery effluent entering the Deep Shaft
plant is screened prior to approximately
8 hours of equalization. Equalized was-
tewater is neutralized to maintain the
pH between 6.5 and 8.5 through the
addition of either liquid caustic soda or
sulphuric acid. Urea and diammonium
phosphata are added prior to neutral-
ization to maintain a BOD, nitrogen.
phosphorous ratio of 100:10:2. At a
total average flow of 2,091 m3 per day
(.552 USMGD) hydraulic retention time
of influent per shaft is approximately
300 minutes. This corresponds to 50
cycles within the shaft before discharge
to the flotation tank.
Air is supplied to the two Deep
Shafts from three rotary screw com-
pressors located in the brewery power
house. Initial operating experience in-
dicates that each train requires approxi-
mately 93 kW (125 hp). Air is added
to the shafts through injection lines in
the downcomer and riser sections.
Deep Shaft headworks showing
Holding tank. Swirl tank, and
*.37m diameter Deep Shaft.
Foam generated in the process
is treated in a separate foam tank and
then recycled back to the shaft.
Solids separation is achieved uti-
lizing flotation clarification which fea-
tures air drive created by the air lift in
the Deep Shaft.
Waste activated sludge gen-
erated in the process, is dewatered by
a Tail Andritz belt press located in the
Deep Shaft building.
Results confirm that the Deep
Shaft produces an effluent containing
less than 50 mg/l BODs and 50 mg/l
TSS. Initial seeding of the Deep Shaft
plant was accomplished utilizing sludge
from the existing extended aeration
plant. Filamentous organisms have
never been observed in the Deep Shaft.
The entire wastewater treatment
plant was built at a cost of approxi-
mately S3.2 million (1979 Canadian).
Partial funding for the project was
made possible by a Government of
Canada Development and Demon-
stration of Pollution Abatement Tech-
nology (DPAT) grant awarded in 1978.
71
-------
[Technical
Profits
Molion'i Bra wary
Plant
Design criteria and
operating parameters
Parameter
US Units
SI Units
Doep Shaft
bloreactor
Flotation
clarification
Average daily flow (ADF)
BODs loading at ADF1
SS loading at ADF
MLSS
MLVSS
F/M ratio at ADF o
Volumetric loading1
Detention time"
Nominal
Actual
Sludge retention time'
Aeration Energy
Surface overflow rate'
(Hydraulic loading)
Mass loading'
Return sludge flow rate
Float recycle
Sink recycle
Return sludge
concentration
Float solids
Sink solids
Waste activated sludge"
0.552 USMGD
11000lb/day
5685lb/day
1.1%
0.825%
1.3 day-1
652.7 Ib BODs/day/ 1000 ft3
300 min
256 min
1.6 days
250 hp
431,3USGPD/ft2
39.5lb/day/ft2
17%
Variable
4%
Variable
5397lbVSS/day
0,69lbTSS/lbBODs
0.5lbVSS/lbBOD5
2091 m3/day
5000 kg /day
2584 kg/day
11000 mg/l
8250 mg/l
1.3 day-'
10.5 kg BOOs/day/m3
300 min
256 min
1.6 days
186 kw
17.5 nvVday/m2
192.S kg/day/m*
17%
Variable
40,000 mg/l :
Variable
2448 kg VSS/day
0.69 kg TSS/kg BOOs removed
0.5 kg VSS/kg BOD5 removed
days. Total BOO; is never to exceed 1 6.500 Ibs (7500 kg) per
F/M loading assumes an influent 800s concentration of 2400
ppm, and a MLVSS content of 75% within the Deep Shaft and
head tank.
Loading based on head tank and Deep Shaft volume.
Actual detection lima based on float and sink recycle rates if
17% and 0% respectively,
SRT defined as kg MWSS in deep snah bioreactor and head tank
per kg VSS wasted as activated sludge, plus VSS lost m effluent
per day,
Rotation tank loadings based on internal tank dimensions and
average influent flow rate.
Activated sludge wasted based on average BOOs concentra-
tions of 2400 ppm and SO ppm in the influent and effluent,
respectively.
72
-------
Technical
Profile
Portage
la Prairie
Plant
The City of Portage la Prairie is a com-
munity of 14,000 people located 80 km
(50 miles) west of Winnipeg, Manitoba,
Canada on the Trans-Canada Highway.
The City of Portage !a Prairie Deep
Shaft effluent treatment plant will be
commissioned in 1981. This advanced
Deep Shaft wastewater treatment plant
is designed to treat combined food
processing effluent and municipal
sewage. The population equivalent of
the combined waste streams is equal
to a municipality of 65,000 people.
W.L. Wardrop & Associates of
Winnipeg, Manitoba are the principal
consulting engineers on the project.
Eco-Research Limited is responsible for
the design and installation of the Deep
Shaft secondary treatment plant. '
Northward Project Control Limited, a
subsidiary of W. L. Wardrop & Asso-
ciates is responsible for construction
management on the project.
The Deep Shaft plant features
dual shafts, each 1.37 m l.D. (54" I.D.)
and 137m (450') deep. Solids separa-
tion is achieved utilizing eight flotation
clarifiers.
The entire facility is enclosed in-
doors in approximately 1.115m2
(12.000ft2).
The plant is capable of treating
5,443 kg BOOs per day (12.000 Ibs
BODs per day) at an average daily flow
of 13,625 m3 per day (3.6 USMGD).
Sustained wet weather flow conditions
for six weeks in the spring of each year
require that the Deep Shaft plant pro-
duce an effluent with less than 30 mg /1
BODsand 30 mg/ITSS at a flow of
36,333 m3 per day (9.66 USMGD).
The Deep Shaft process was se-
lected for the City of Portage la Prairie
because:
the process demonstrated large
energy savings when compared
to other alternatives,
« the Deep Shaft plant is a totally
new facility while other alterna-
Portaga big hole drilling tool.
lives required retrofitting of the
existing facility,
the Deep Shaft plant is totally en-
closed which provides an excellent
working and treatment environ-
ment in view of the harsh Cana-
dian winters and
the major portion of the project
was available at a firm price ac-
companied by performance and
operating cost warranties
Funding for the project was made
possible by Canada Mortgage and
Housing Corporation (CMHC), Manitoba
Water Services Board, and the City of
Portage la Prairie.
The total project cost is estimated
at $4 million (1980 Canadian)
73
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4
Technical
profite
Portaga U Prairi*
Plant
Design criteria and
operating parameters
Deep Shaft
bioroactor
Flotation
clarification
Parameter
Average daily flow (ADF)
Peak diurnal flow
Sustained wet weather flow
Instantaneous peak flow
BODs loading at ADP
SS loading at ADF
MISS
MLVSS
F/M ratio at ADF"
Volumetric loading0
Detention time
Nominal
Actual"
Sludge retention time'
Aeration Energy
Surface overflow rate'
(Hydraulic loading)
Mass loading'
Return sludge flow rate
Float recycle
Sink recycle
Return sludge
concentration
Float solids
Sink solids
Waste activated sludge'
US Units
3.6 USMGD
7.2 USMGD
9.6 USMGD
14.4 USMGD
12000 Ib/day
12000 Ib/day
1.0%
0.8%
1.53 day-1
762 lbBODs/day/1000 ft3
40 min
36 min
1 .3 days
150hp
560 USGPD/ft2
49.4 Ib/day/ft2
10%
0%ADF
5%
Variable
5563 IbVSS/day
0.69 IbTSS/lbBOOs
0.5 IbVSS/lbBODs
SI Units
13625 nvVday
27250 m'/day
36333 mVday
54450 m3/day
5440 kg /day
5440 kg /day
10000 mg/l
8000 mg/l
1 .53 day-'
12.2 kg80Ds/day/m3
40 min
36 min
1 .3 days
112kW
23 m3/day/m2
241 kg/day/ms
10% i
0%ADF
50, 000 mg/l
Variable
2523 IcgVSS/day
0.69 kg TSS/kg 8QD5 removed
0.5 kg VSS/kg BODs removed
For AOF, during sustained wot weather flow BOOs concentra-
tion cannot excsd 20,000 Ib/day.
F/ M loading assumes ah influent BOOs concentration of dOO ppm
and a MLVSS content of 75% within the deep shaft and head
tank.
Loading based on head tank and bioreactor volume.
Actual detection time based on float and smk recycle rates of
10% and 0% respectively
SRT defined as kg MIVSS m deep shaft bioreactor and head tank
per kg VSS wasted as activated sludge, plus VSS lost m effluent
par day.
Flotation tank loadings based on internal tank dimensions and
ADF influent rate
Activated sludge wasted based on average 800s concentra-
tions of 400 ppm and 30 ppm m the influent and effluent res-
pectively,
74
U.S. GOVERNMENT PRINTING OFFICE: 1982-559-092/3374
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