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“Providing a high level of sanitary benefits to the communities we serve.”
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.”
Slide 3
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.
Because of persistent pollution on the Niagara River, Canada and the US entered into a treaty in 1909 to protect boundary waters.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 4
History of the Buffalo Sewer Authority
Bird Island prior to the construction of the WWTP
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 5
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
History of the Buffalo Sewer Authority
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 6
History of the Buffalo Sewer Authority
Bird Island Primary Treatment Plant in 1938
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 7
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
Sludge Dewatering Centrifuge
History of the Buffalo Sewer Authority
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 8
History of the Buffalo Sewer Authority
Bird Island Primary Treatment Plant 1980’s & 90’s
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 9
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
Re-tubing of Natural and Digester Gas Fired Boilers, $150,000 project.
Rehabilitation of Substation and Switchgear, $150,000 in total projects.
Angel RiveraSuperintendent of Mechanical Maintenance
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 10
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
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 11
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)
Approximate Age: 25 Years (Installed in 1975).
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 12
Final Clarifiers at the Bird Island WWTP
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 13
Final Clarifiers at the Bird Island WWTP
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 14
Rise Pipe Pier Supported Type Clarifier
Diameters larger than 30 feet
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 15
Riser Pipe Clarifier Sludge Withdrawal Flow
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 16
Riser Pipe Control
Riser Pipe Clarifier Sludge Control Box
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 17
Final Clarifiers at the Bird Island WWTP
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 18
Existing Peripheral Feed & Overflow
Sludge Box
InfluentFlow
Sludge to Center Drain
Effluent Waste- water Flow
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 19
Existing Peripheral Feed & Overflow
Influent
Flow Effluent
Flow
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 20
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.
Control individual sludge tube flow in center RAS box with new control valves (“twist turn orifice terminals”).
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 21
Final Clarifiers at the Bird Island WWTP
Pipes Create Wall Effect
Mass Rotation
One of five pipes
pluggedAt least
20% floor not picked
up
Sludge Box Flow Control
Drive Unit24 minutes
per revolution
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 22
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”).
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 23
Final Clarifier Rehabilitation December 2001
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 24
Final Clarifier Rehabilitation December 2001
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 25
Final Clarifier Rehabilitation December 2001
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 26
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.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 27
Proposed Repairs to Final Clarifiers 7B & 8B
Use crane to remove bridge & Railing
Inspect and repair:
Center Pier, Sludge Box and Center
Cage.
Use crane to remove and replace Center
Drive Unit
Separate arms from center cage. Inspect and repair structural damage.
Repair or replace all damaged piping, boots, wiper blades, piping support.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 28
Proposed Repairs to Final Clarifiers 7B & 8B
Re-attach and rebalance arms. Adjust and level rotating plane.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 29
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
Structural Steel Hot Dip Galvanized
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 30
Tow-bro Clarifier Design
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 31
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.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 32
Tow-Bro Header Peripheral Feed & Overflow
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 33
Tow-Bro Header
Unitube Header with 23 Withdrawal Points
21” x 21” Manifold Inlet Approximate 2’ Horizontal Profile
Drive Unit33.3 minutes
per revolution
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 34
Exiting Riser Pipe Final Clarifiers
Sludge Box Largest Inlet
Pipe 8”
Sludge to Center Drain
Only 5 Withdrawal Pipes,Horizontal Pipe Arrangement
Approximate 5’ Horizontal Profile
Drive Unit24 minutes
per revolution
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 35
Existing Peripheral Feed & Overflow
Influent
Flow Effluent
Flow
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 36
Existing Peripheral Feed & Overflow
Sludge to Center Drain
Influent
Flow
Effluent
Flow
Sludge Box
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 37
Tow Bro H-drive
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 38
Tow-Bro Strip Liner Drive Unit
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 39
Riser-pipe Ball Race Bearing
4 pt. Ball Bearing
Oil Bath
Felt Bearing Race Cover
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 40
Circular Clarifier Drive UnitsBearing Arrangements
Strip Liner 4 Pt. Contact
Tow-Bro H-Drive Bearing
Riser-Pipe Ball Race Bearing (4-Point)
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 41
Tow-Bro H-DriveBearing 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
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 42
Tow-Bro H-Drive Replaceable Strip Liner
ReplaceableStrip Liner
Main Gear
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 43
Tow-Bro H-Drive Replaceable Strip Liner
• Main Gear Split for On Site Disassembly
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 44
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
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 45
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
Circular Clarifier Drive Units Main Bearing Failures
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 46
Circular Clarifier Drive UnitsMain Bearing Arrangements
Oil Lubricated “Water Lubricated”
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 47
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.
Note: Heat Trace required for operation during periods of below freezing temperature.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 48
Passive Automatic Condensate Drain System
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 49
Main Tank Skimmer Assembly
Scum Blade LengthFrom Center to Side of Tank
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 50
Main Tank Skimmer Assembly
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 51
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
Downside - Real World Performance at BSA Unknown?
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 52
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
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 53
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
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 54
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
Final Clarifier Rehabilitation – Jan 2001 to Feb 2001
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 55
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
March 18, 2002 – Q. Co mobilizes on-site and begin receiving major Tow-Bro components (Trusses, Headers, Drive Unit)
Final Clarifier Rehabilitation – Feb 2001 to March 2001
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 56
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.
Final Clarifier Rehabilitation – March 2001 to July 2001
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 57
Final Clarifier Rehabilitation – Construction Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 58
Final Clarifier Rehabilitation – Construction Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 59
Final Clarifier Rehabilitation – Construction Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 60
Final Clarifier Rehabilitation – Construction Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 61
Final Clarifier Rehabilitation – Construction Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 62
Final Clarifier Rehabilitation – Construction Photos
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 63
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.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 64
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.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 65
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
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 66
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)
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 67
Phased Approach for Final Clarifier Rehabilitation
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
StartYear
Final Clarifiers
PurchaseCost
Installation Cost
Total Project Cost
Per Unit Cost
2002 7B, 8B $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 68
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.
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 69
Phased Approach for Final Clarifier Rehabilitation – Photos
Upper Weir Wall Supports
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 70
Phased Approach for Final Clarifier Rehabilitation – Photos
Lower Weir Wall Supports (under skirt)
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 71
Phased Approach for Final Clarifier Rehabilitation – Photos
Rehabilitated Upper Weir Wall Supports
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 72
Phased Approach for Final Clarifier Rehabilitation – Photos
Rehabilitated Weir Wall
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 73
Phased Approach for Final Clarifier Rehabilitation – Photos
Rehabilitated Lower Weir Wall Supports (under skirt)
“Providing a high level of sanitary benefits to the communities we serve.”
Slide 74
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.
Completion of all final tanks project to be completed by 2010
“Providing a high level of sanitary benefits to the communities we serve.”
James Skrabacz – Maintenance DepartmentRoberta Gaiek P.E., Jane Ork – Process DepartmentSal LoTempio (Ret.), James Keller – WWTP SuperintendentFrank DiMascio P.E., Joe Baudo (Ret.), Jim Eagan – BSA EngineeringDavid Comerford – BSA General ManagerHerbert Bellamy - Buffalo Sewer Authority Board Chairman US Filter / Siemens Water Technology
Special Thanks to the following:
“Providing a high level of sanitary benefits to the communities we serve.”
Angel RiveraSuperintendent of Mechanical Maintenance
Buffalo Sewer Authority90 West Ferry St.Buffalo, NY 14213-1799Office: (716) 883-1820 ext 217Fax: (716) 883-4922E-Mail: arivera@sa.ci.buffalo.ny.us
Thank you very much for your attention.
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