“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.”

An In House – Phased Approach for Final Clarifier Rehabilitation


Angel Rivera Superintendent of Mechanical Maintenance


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.


Slide 4


Bird Island prior to the construction of the WWTP


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



Slide 6


Bird Island Primary Treatment Plant in 1938


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



Slide 8


Bird Island Primary Treatment Plant 1980’s & 90’s


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


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


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).


Slide 12

Final Clarifiers at the Bird Island WWTP


Slide 13



Slide 14

Rise Pipe Pier Supported Type Clarifier

Diameters larger than 30 feet


Slide 15

Riser Pipe Clarifier Sludge Withdrawal Flow


Slide 16

Riser Pipe Control

Riser Pipe Clarifier Sludge Control Box


Slide 17



Slide 18

Existing Peripheral Feed & Overflow

Sludge Box

InfluentFlow

Sludge to Center Drain

Effluent Waste- water Flow


Slide 19


Influent

Flow Effluent

Flow


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”).


Slide 21


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


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”).


Slide 23

Final Clarifier Rehabilitation December 2001


Slide 24



Slide 25



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.


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.


Slide 28

Proposed Repairs to Final Clarifiers 7B & 8B

Re-attach and rebalance arms. Adjust and level rotating plane.


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


Slide 30

Tow-bro Clarifier Design


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.


Slide 32

Tow-Bro Header Peripheral Feed & Overflow


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


Slide 34

Exiting Riser Pipe Final Clarifiers

Sludge Box Largest Inlet

Pipe 8”


Only 5 Withdrawal Pipes,Horizontal Pipe Arrangement

Approximate 5’ Horizontal Profile

Drive Unit24 minutes

per revolution


Slide 35


Influent

Flow Effluent

Flow


Slide 36



Influent

Flow

Effluent

Flow

Sludge Box


Slide 37

Tow Bro H-drive


Slide 38

Tow-Bro Strip Liner Drive Unit


Slide 39

Riser-pipe Ball Race Bearing

4 pt. Ball Bearing

Oil Bath

Felt Bearing Race Cover


Slide 40

Circular Clarifier Drive UnitsBearing Arrangements

Strip Liner 4 Pt. Contact

Tow-Bro H-Drive Bearing

Riser-Pipe Ball Race Bearing (4-Point)


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


Slide 42

Tow-Bro H-Drive Replaceable Strip Liner

ReplaceableStrip Liner

Main Gear


Slide 43

Tow-Bro H-Drive Replaceable Strip Liner

• Main Gear Split for On Site Disassembly


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


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


Slide 46

Circular Clarifier Drive UnitsMain Bearing Arrangements

Oil Lubricated “Water Lubricated”


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.


Slide 48



Slide 49

Main Tank Skimmer Assembly

Scum Blade LengthFrom Center to Side of Tank


Slide 50

Main Tank Skimmer Assembly


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


Downside - Real World Performance at BSA Unknown?


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


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


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


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


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


Slide 57

Final Clarifier Rehabilitation – Construction Photos


Slide 58



Slide 59



Slide 60



Slide 61



Slide 62



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.


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.


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


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)


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

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


Slide 68


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 69

Phased Approach for Final Clarifier Rehabilitation – Photos

Upper Weir Wall Supports


Slide 70


Lower Weir Wall Supports (under skirt)


Slide 71


Rehabilitated Upper Weir Wall Supports


Slide 72


Rehabilitated Weir Wall


Slide 73


Rehabilitated Lower Weir Wall Supports (under skirt)


Slide 74


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


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:


Angel RiveraSuperintendent of Mechanical Maintenance

Buffalo Sewer Authority90 West Ferry St.Buffalo, NY 14213-1799Office: (716) 883-1820 ext 217Fax: (716) 883-4922E-Mail: [email protected]

Thank you very much for your attention.

Documents

“Providing a high level of sanitary benefits to the communities we serve.” An In House – Phased Approach for Final Clarifier Rehabilitation