An In House – Phased
Approach for Final Clarifier
Rehabilitation
“Providing a high level of sanitary benefits to the communities we serve.”
Angel Rivera
Superintendent of Mechanical
Maintenance
“Providing a high level of sanitary benefits to the communities we serve.”
History of the Buffalo Sewer Authority
 When Buffalo was established as a village, all
waste was disposed in adjacent bodies of water.
 In the 1890’s, health officials agreed that the
pollution to the adjacent bodies of water was
responsible for many diseases, most notably,
typhoid.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 3
 Because of persistent pollution on the Niagara
River, Canada and the US entered into a treaty
in 1909 to protect boundary waters.
History of the Buffalo Sewer Authority
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 4
Bird Island prior to the construction of the WWTP
History of the Buffalo Sewer Authority
 In 1935, the New York State Department of Health
mandated the City of Buffalo to stop polluting the Niagara
River with waste. Because the city was in financial turmoil
at the time, a new authority was created – the Buffalo
Sewer Authority.
 By 1938, the Authority completed its system of
intercepting sewers, and built its primary treatment plant
on Bird Island where all city sewage was treated.
 This start of the art Primary Sewage Treatment Plant:
 Removed and incinerated all solid matter.
 Chlorinated all liquid matter prior to discharging into the
Niagara River
Slide 5
“Providing a high level of sanitary benefits to the communities we serve.”
History of the Buffalo Sewer Authority
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 6
Bird Island Primary Treatment Plant in 1938
History of the Buffalo Sewer Authority
 With the increasing national awareness of the need to
more fully protect our water resources, the State in 1966
directed further improvement of our facilities by providing
secondary treatment.
 With the help of federal and state grants, secondary
treatment facilities were constructed and placed in service
by 1981.
 Continual process improvements and upgrades
 Examples of Major Capital Improvements since 1981
 Fine Bubble Diffuser and Blower Re-rating Project
 WWTP SCADA System
 New Grit Removal & Disposal System
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 7
 Sludge Dewatering Centrifuge
History of the Buffalo Sewer Authority
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 8
Bird Island Primary Treatment Plant 1980’s & 90’s
Angel Rivera
Superintendent of Mechanical Maintenance
 Supervise and coordinate all activities of the Maintenance Department at the
Buffalo Sewer Authority’s Bird Island Wastewater Treatment Plant (WWTP).
 Responsible for the upkeep and repair of all equipment, utilities, buildings and
grounds at the WWTP and eleven (11) Remote Pumping & Metering Stations.
 Implemented capital projects totaling over $8 million in a 6 year period, including:
 Installation of sludge withdrawal equipment on 16 clarifiers, $2.2 million project.
 Cleaning of two large (1 million gallon) anaerobic digesters, $1.7 million project.
 Rehabilitation of South Buffalo Pumping Station, $1.5 million project.
 Annual Rehabilitation of 3 WWTP Incinerators, $1.2 million in total projects.
 Rehabilitation of motors and impellers on three 3000/5000 HP blowers,
$900,000 project.
 Rehabilitation of 2-550 HP RWWP and 2-1850 HP SWWP Pumps $300,000
 Rehabilitation of Substation and Switchgear, $150,000 in total projects.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 9
 Re-tubing of Natural and Digester Gas Fired Boilers, $150,000 project.
Final Clarifiers
 What’s Their Purpose
 Improve Effluent Quality
 Provide a means for solids and floatables to separate
from the forward flow and be collected
 Main Components
 Method of Settled Solids Removal
 Inlet Arrangements
 Method of Scum Removal
 Drive Units
Slide 10
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifiers at the Bird Island WWTP- 2001
 Quantity: 16
 Diameter: 130 feet
 Depth: 12’ @ Side-Wall, 12.5’ @ Tank Center
 Total Average Design Flow: 180 mgd
 Total Peak Design Flow: 360 mgd
 Type Design: Riser Pipe
 OEM: FMC (US Filter / Siemens Water Technology)
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 11
 Approximate Age: 25 Years (Installed in 1975).
Final Clarifiers at the Bird Island WWTP
Slide 12
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifiers at the Bird Island WWTP
Slide 13
“Providing a high level of sanitary benefits to the communities we serve.”
Rise Pipe Pier Supported Type Clarifier
 Diameters larger than 30 feet
Slide 14
“Providing a high level of sanitary benefits to the communities we serve.”
Riser Pipe Clarifier Sludge Withdrawal Flow
Slide 15
“Providing a high level of sanitary benefits to the communities we serve.”
Riser Pipe Clarifier Sludge Control Box
Riser Pipe
Control
Slide 16
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifiers at the Bird Island WWTP
Slide 17
“Providing a high level of sanitary benefits to the communities we serve.”
Existing Peripheral Feed & Overflow
Influent
Flow
Sludge Box
Effluent
Wastewater
Flow
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 18
Sludge to Center Drain
Existing Peripheral Feed & Overflow
Influent
Flow
Effluent
Flow
Slide 19
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifiers at the Bird Island WWTP
 1998 Field Evaluation of Secondary Clarifiers By John Esler, P.E.
 Conclusion:
 Moderate short circuiting up to a flow of 11 mgd
 High sludge blankets and direct short circuiting at higher flows
 At all flow rates, high degree of rotational stirring, creating instability at
the tank periphery and retarding the inward current
 Recommendations:
 Reduce rotational rate.
 Reconfigure sludge pipes to lay horizontal on collector frame.
 Replace variable sized return sludge tubes.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 20
 Control individual sludge tube flow in center RAS box with new control
valves (“twist turn orifice terminals”).
Final Clarifiers at the Bird Island WWTP
Drive Unit
24 minutes
per revolution
Pipes Create
Wall Effect
Mass Rotation
Sludge
Box Flow
Control
One of
five pipes
plugged
At least
20% floor
not picked
up
Slide 21
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation December 2001
 December 2001
 Final Clarifiers 7B & 8B Out of Service Due to Drive
Failures and Structural Misalignment.
 The Structural Integrity of Truss Arms, Center Cage and
Center Pier on both units are in question.
 Treatment Plant Maintenance unable to repair units
utilizing available parts, supplies and equipment.
 US Filter (FMC) brought on site to inspect the condition of
the remaining 14 tanks.
 Drives on 7 of the remaining 14 tanks in determined to be
“marginal” condition (Replacement gap setting >0.375”).
Slide 22
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation December 2001
Slide 23
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation December 2001
Slide 24
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation December 2001
Slide 25
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation
 Repair of Final Clarifiers 7B & 8B – Choices?
 Replace existing drive unit.
 Inspect and repair all failed structural components.
 High Cost repair with no improvement in performance.
 No guarantee that remaining components will not fail in the near
future.
 Reliability of remaining Final Clarifiers unknown.
 Continual high maintenance cost for existing Final Clarifiers
 Constant withdrawal tube plugging
 Repairing damaged to collector piping, boots, wipers and
supports.
 Long draining and cleaning time.
Slide 26
“Providing a high level of sanitary benefits to the communities we serve.”
Proposed Repairs to Final Clarifiers 7B & 8B
Use crane to remove
bridge & Railing
Separate arms from center cage. Inspect
and repair structural damage.
Use crane to remove
and replace Center
Drive Unit
Inspect and
repair:
Center Pier,
Sludge Box
and Center
Cage.
Repair or replace all damaged piping,
boots, wiper blades, piping support.
Slide 27
“Providing a high level of sanitary benefits to the communities we serve.”
Proposed Repairs to Final Clarifiers 7B & 8B
Re-attach and rebalance arms.
Adjust and level rotating plane.
Slide 28
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation
 December 2001 - Meet with US Filter rep to discuss
purchase of new Sludge Withdrawal Equipment.
 Presented with a proposal for two new Tow-Bro Header
Sludge Withdrawal mechanisms, including:
 Unitube sludge removal headers and supports
 H40Ht Drive Unit w/ Reducer, Motor and Overload
 Drive Platform
 Center Pier
 Skimmer Assembly
 Associated Bolts and Anchors
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 29
 Structural Steel Hot Dip Galvanized
Tow-bro Clarifier Design
Slide 30
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-bro History and Development
 Tow-bro developed in 1920’s by Darwin Townsend and
James Brower.
 Envirex, as Rex Chain Belt, installed the first Tow-Bro in
1929.
 Refinements to design resulted in Unitube header
developed in 1955 by Envirex
 To date over 2500 Tow-Bro clarifiers installed.
Slide 31
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-Bro Header
Peripheral Feed & Overflow
Slide 32
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-Bro Header
Drive Unit
33.3 minutes
per revolution
Unitube Header with
23 Withdrawal Points
21” x 21” Manifold Inlet
Approximate 2’ Horizontal Profile
Slide 33
“Providing a high level of sanitary benefits to the communities we serve.”
Exiting Riser Pipe Final Clarifiers
Drive Unit
24 minutes
per revolution
Sludge Box
Largest Inlet
Pipe 8”
Only 5 Withdrawal Pipes,
Horizontal Pipe Arrangement
Approximate 5’
Horizontal Profile
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 34
Sludge to Center Drain
Existing Peripheral Feed & Overflow
Influent
Flow
Effluent
Flow
Slide 35
“Providing a high level of sanitary benefits to the communities we serve.”
Existing Peripheral Feed & Overflow
Influent
Effluent
Flow
Flow
Sludge
Box
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 36
Sludge to Center Drain
Tow Bro H-drive
Slide 37
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-Bro Strip Liner Drive Unit
Slide 38
“Providing a high level of sanitary benefits to the communities we serve.”
Riser-pipe Ball Race Bearing
Felt Bearing
Race Cover
4 pt. Ball
Bearing
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 39
Oil Bath
Circular Clarifier Drive Units
Bearing Arrangements
Strip Liner
Riser-Pipe Ball Race
Bearing (4-Point)
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 40
Tow-Bro H-Drive
Bearing
4 Pt. Contact
Tow-Bro H-Drive
Bearing Arrangements
 Strip Liner
 Split Gear
 Field Inspection of bearing
 38 to 42 Rc
 Can be rebuilt, in-place, in the
field
 Low Cost, quick delivery
 Keeps working after failure
Slide 41
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-Bro H-Drive Replaceable Strip Liner
Replaceable
Strip Liner
Main Gear
Slide 42
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-Bro H-Drive Replaceable Strip Liner
• Main Gear Split for On Site Disassembly
Slide 43
“Providing a high level of sanitary benefits to the communities we serve.”
Riser-Pipe Ball Race Bearing
 4 Point Contact
 Higher Hardness
 Higher Loads
 Factory Repair Only
 Requires Crane and Lifting of
Bridge
 Locks up with Failure
Slide 44
“Providing a high level of sanitary benefits to the communities we serve.”
Circular Clarifier Drive Units Main Bearing Failures
 Condensate, water, produces oxidation, rust
 High carbon content of the balls, races oxidize very
quickly
 Oxidation leads to surface pits
 Surface pits lead to stress risers
 Stress risers lead to critical shearing stress
 Broken balls
Slide 45
“Providing a high level of sanitary benefits to the communities we serve.”
Circular Clarifier Drive Units
Main Bearing Arrangements
Oil Lubricated
“Water Lubricated”
Slide 46
“Providing a high level of sanitary benefits to the communities we serve.”
Passive Automatic Condensate Drain System
 The Drive is Equipped with piping that allows any
Condensate that would otherwise accumulate in the
main Drive Housing to drain out.
 The difference in Specify Gravity between water and
lubricating oil used in drive is the principle upon the
system functions.
 Note: Successful operation of the system depends
upon the sequence of filling the drive housing
initially and every time periodic maintenance is
performed.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 47
 Note: Heat Trace required for operation during
periods of below freezing temperature.
Passive Automatic Condensate Drain System
Slide 48
“Providing a high level of sanitary benefits to the communities we serve.”
Main Tank Skimmer Assembly
Scum Blade Length
From Center to Side of Tank
Slide 49
“Providing a high level of sanitary benefits to the communities we serve.”
Main Tank Skimmer Assembly
Slide 50
“Providing a high level of sanitary benefits to the communities we serve.”
Tow-Bro Benefits for Final Clarifiers 7B & 8 B
New drive, collector, and structural components.
Reduced rotational rate, less stirring of the FC
tank.
Lower header profile.
Increased number of withdrawal points, reducing
the effect of plugging.
Removal of Sludge Box
Passive Automatic Condensate Drain System
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 51
Downside - Real World Performance at BSA
Unknown?
Final Clarifier Rehabilitation – December 2001
 Final Clarifiers 7B and 8B Out of Service and Cleaned by
Maintenance for Repairs by 12/4/01.
 Maintenance begins initial repairs to both tanks. Discovers
structural damage to drive unit, truss arms, center cage and
sludge box.
 Contact US Filter for preliminary budgeting information regarding
the replacement Drive Units. Request on-site inspection and
evaluation of remaining 14 FC tanks.
 US Filter on site on 12/10/01 for tank inspection.
 US Filter submits proposal for Tow-Bro equipment
Slide 52
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Dec 2001 to Jan 2001
 Maintenance Department reviews and evaluates proposed
equipment. Contacts references and validates past
performance claims.
 Maintenance Department works with Process Department to
determine design flows.
 Maintenance Department presents findings to BSA management
(General Manager, Financial Officer, Plant Manager).
 BSA management agrees with finding and BSA Board is polled
for approval.
 January 9, 2002 - BSA Board Approvals purchase of Tow-Bro
Headers for a not to exceed price of $195,000.00
Slide 53
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Jan 2001 to Feb 2001
 Maintenance Department develops final purchase specifications.
 January 4, 2002 – Maintenance submits purchase specs for
design of new Tow-Bro system.
 January 25, 2002 – Maintenance Department reviews and
approves arrangement plan and elevations for 2 new Tow-Bro
Sludge Collectors
 January 29, 2002 – US Filter releases the design for fabrication.
 February 5, 2002 – Meet with Mechanical Maintenance
Contractor Quackenbush (Q Co.) to review installation
requirements for 2 new Tow-Bro Sludge Collectors
Slide 54
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Feb 2001 to March 2001
 February 18 2002 – Q. Co. submits proposal for Tow-Bro
installation under the terms of the existing Maintenance Contract.
 Proposal reviewed by maintenance and submitted to BSA
Management for approval.
 Approximate cost for installation of Tow-Bro equipment on both
tanks $70,000.
 February 27, 2002 – BSA Board approves Q. Co, proposal for a
not to exceed cost of $70,000.
 March 4, 2002 – US Filter begins shipping Tow-Bro components
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 55
 March 18, 2002 – Q. Co mobilizes on-site and begin receiving
major Tow-Bro components (Trusses, Headers, Drive Unit)
Final Clarifier Rehabilitation – March 2001 to July 2001
 March 22, 2002 – Last major Tow-Bro components ships from US
Filter fabrication shop.
 March 22, 2002 to May 24, 2002 – Q. Co proceeds with
installation of Tow-Bro equipment in Tanks 7B & 8B. Maintenance
Department supervises and inspects all work by contractor.
 May 27, 2002 – US Filter and Maintenance Department complete
the start-up and testing of completed units. Both units on-line by
first week in June.
 June 2002 to July 2002 – Both units in service with Plant
Operations.
 July 24, 2002 – Performance Testing by CPE Services begins.
Slide 56
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Construction Photos
Slide 57
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Construction Photos
Slide 58
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Construction Photos
Slide 59
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Construction Photos
Slide 60
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Construction Photos
Slide 61
“Providing a high level of sanitary benefits to the communities we serve.”
Final Clarifier Rehabilitation – Construction Photos
Slide 62
“Providing a high level of sanitary benefits to the communities we serve.”
Field Verification Study - Goals
 July 2002, CPE Service Inc. (John Elser, P.E.) hired to Study
performance of new Tow-Bro verse existing Riser-Pipe
 Field investigation designed to a accomplish the following:
 Develop flow curves and determine detention times
 Determine location and intensity of major currents using velocity
profile test and full-depth solids profiles.
 Determine Theoretical solids loading capacity of each clarifier
using solids flux / state point analysis
 Characterize the relative performance of the two clarifiers.
Slide 63
“Providing a high level of sanitary benefits to the communities we serve.”
Field Verification Study – Conclusions
 Tow-Bro clarifier develop the inward flow pattern that is
desirable for peripheral feed / peripheral overflow clarifier.
 Tow-Bro clarifier maintained a lower blanket further assisting
the inward flow pattern.
 Tow Bro better controlled sludge blanket as flow rates varied.
 Tow-Bro was able to operate at significantly higher flow rate
that the existing Rise-Pipe.
 Two-Bro able to maintain a more concentrated return
activated sludge flow that existing Rise-Pipe.
Slide 64
“Providing a high level of sanitary benefits to the communities we serve.”
Phased Approach for Final Clarifier Rehabilitation
 Based on documented performance of the new Tow-Bro system the
BSA’s management developed a phased approach to rehabilitating the
remaining 14 final clarifiers.
 A preliminary plan calling for the rehabilitation of the remaining clarifiers
at a rate of four clarifiers per year was submitted as part of the BSA’s
Annual Capital Improvement Plan.
 Equipment purchase and installation funded annually based on savings
and rollover of operating funds from previous budget years.
 Tow-Bro equipment purchased by Maintenance directly from the
manufacture US Filter as funding became available.
 All purchase specification developed by Maintenance Department without
the use of outside consultants
Slide 65
“Providing a high level of sanitary benefits to the communities we serve.”
Phased Approach for Final Clarifier Rehabilitation
 Installation contract developed by and bid annually by the BSA
Maintenance and Engineering Departments.
 Contract installation requirements developed by Maintenance
Department without use of outside consultants.
 All contract equipment, supplies and labor inspected directly
by Maintenance Department.
 Rehabilitation of tanks based on severity of existing tank
conditions (i.e. Worst Tanks First).
 Installation contract revised annually, prior to bidding, to
address problems encountered in previous years contract (i.e.
Change Orders, Contract Clarifications, Etc)
Slide 66
“Providing a high level of sanitary benefits to the communities we serve.”
Phased Approach for Final Clarifier Rehabilitation
Start
Year
Final
Clarifiers
Purchase
Cost
2002 7B, 8B
Installation
Cost
Total Project
Cost
Per Unit
Cost
$195,000
$74,463
$269,463
$134,731
2003 3A,4A,4B,6B
1
$334,688
$142,320
$477,008
$119,252
2004 2A,7A,8A,1B
1
$334,688
3 $151,200
$485,888
$121,472
2005 1A,5A,2B,5B
2
$387,834
3
$151,800
$539,634
$134,909
2006 6A,1B
2
$194,000
4
$261,790
$455,790
$227,895
Cost to Date
$1,446,210
$781,572
$2,227,782
$139,236
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 67
Footnotes:
1. Equipment price held for 2 years at $83,667 per FC.
2. Price increase to $97,000 per FC due to escalating Steel Price.
3. Installation Completed without Change Orders.
4. First project to include Weir Wall Rehabilitation
Phased Approach for Final Clarifier Rehabilitation
 Installation Contract revision include the following activities:
 Material Disposal
 Electrical Connections
 Floor leveling and concrete breakouts
 Scum trough piping.
 Weir Plate Adjustment
 Weir Plate Pipe Support Replacement
 Sandblasting and Painting of all Metal Surfaces in Final Effluent Tank.
Slide 68
“Providing a high level of sanitary benefits to the communities we serve.”
Phased Approach for Final Clarifier
Rehabilitation – Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 69
Upper Weir Wall Supports
Phased Approach for Final Clarifier
Rehabilitation – Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 70
Lower Weir Wall Supports (under skirt)
Phased Approach for Final Clarifier
Rehabilitation – Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 71
Rehabilitated Upper Weir Wall Supports
Phased Approach for Final Clarifier
Rehabilitation – Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 72
Rehabilitated Weir Wall
Phased Approach for Final Clarifier
Rehabilitation – Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 73
Rehabilitated Lower Weir Wall Supports (under skirt)
Phased Approach for Final Clarifier
Rehabilitation
 Next Phase – Weir and Tank Rehabilitation. Activities that may
be included are the following:
 Weir Plate Adjustment
 Weir Plate Pipe Supports – both above and bellow Weir Skirt
 Sandblasting and painting of all metal surfaces.
 Final Clarifier Floor Coating (re-lining).
 Repositioning of Inlet Channel flow holes
 Raising of inlet channel wall to increase peak influent flow
 Continue rehabilitation rate of 4 tanks per year.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 74
 Completion of all final tanks project to be completed by 2010
Special Thanks to the following:
James Skrabacz – Maintenance Department
Roberta Gaiek P.E., Jane Ork – Process Department
Sal LoTempio (Ret.), James Keller – WWTP Superintendent
Frank DiMascio P.E., Joe Baudo (Ret.), Jim Eagan – BSA Engineering
David Comerford – BSA General Manager
Herbert Bellamy - Buffalo Sewer Authority Board Chairman
US Filter / Siemens Water Technology
“Providing a high level of sanitary benefits to the communities we serve.”
Angel Rivera
Superintendent of Mechanical Maintenance
Thank you very much for your attention.
Buffalo Sewer Authority
90 West Ferry St.
Buffalo, NY 14213-1799
Office:
(716) 883-1820 ext 217
Fax:
(716) 883-4922
E-Mail:
arivera@sa.ci.buffalo.ny.us
“Providing a high level of sanitary benefits to the communities we serve.”