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Single Stage Compressors As Part of a Fine Bubble Diffused Aeration Retrofit. at the. Albany County Sewer District. A Look Back Nine Years. Daniel W. Clayton. RMWEA Operators Seminar 10/29/04. Authors and Affiliations. Daniel W. Clayton, P.E.

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A look back nine years

Single Stage Compressors As Part of a Fine Bubble Diffused Aeration Retrofit

at the

Albany County Sewer District

A Look Back Nine Years

Daniel W. Clayton

RMWEA Operators Seminar

10/29/04


Authors and affiliations
Authors and Affiliations

  • Daniel W. Clayton, P.E.

    Principal Engineer, Brown and Caldwell(formerly of Malcolm Pirnie, Inc.)

  • Richard J. Lyons

    Superintendent of Operations, Albany County Sewer District (ACSD)

  • Peter Kyriacopoulos – Atlas Copco Comptec (ACC)


Introduction outline 1
Introduction/Outline – 1

  • Background/project motivation

  • Design Assumptions

  • Single-stage compressor technology

  • Operating Data

  • Operating Cost


Introduction outline 2
Introduction/Outline – 2

  • Payback

  • Operator’s comments

  • Engineer’s perspective

  • Comments/questions


Background project motivation
Background/Project Motivation

  • ACSD – two activated sludge plants

  • Treat primarily for BOD w/ seasonal nitrification


Process schematic north and south
Process Schematic – North and South

Reprinted from: ACSD 2003 Annual Report


North plant performance 2003
North Plant Performance - 2003

Reprinted from: ACSD 2003 Annual Report


South plant performance 2003
South Plant Performance – 2003

Reprinted from: ACSD 2003 Annual Report


Mechanical aeration systems
Mechanical Aeration Systems

  • Three tanks in service

  • Single and dual-speed aerators


Why replace the surface aerators
Why Replace the Surface Aerators?

  • 20+ years old

  • Repair frequency increasing

  • NMPC contractor study showing projected savings (7/92)

  • NMPC grant eligible


Planning design assumptions 1
Planning: Design Assumptions – 1

  • Little growth in treatment requirements

  • BOD and nitrification

  • Capacity available in remaining mechanical basins

  • Additional air capacity at North Plant desirable

  • Blower efficiency – 70%


Planning design assumptions 2
Planning: Design Assumptions – 2

Source: MPI Design Memorandum


Planning cost considerations
Planning – Cost Considerations

  • Capital

    • Equipment

    • Support Facilities

  • O&M

    • Single stage electrical cost savings significant (vs. multi-stage)

    • Other costs not given large consideration


Single stage features 1
Single Stage Features – 1

  • Energy efficiency at design point

  • Energy efficiency at turn-down (IGV; 9% better than throttling valve)

  • Overall ≥ 70% efficiency projected


Single stage features 2
Single Stage Features – 2

  • Wide range of flow/custom tuning

  • PLC – available for control use

  • Meet demanding industry standards (e.g. API)


Single stage design considerations
Single Stage Design Considerations

  • For wide variations in air requirements

  • For higher pressure situations (24 ft. WC – 10+psig)

  • Bigger units (2 S/S vs. 3 M/S)

  • Noise

  • Cooling


Design major elements each plant
Design: Major Elements – Each Plant

  • Three tanks with ceramic disk diffusers

  • One single-stage compressor on, one standby


Design major elements each plant1
Design: Major Elements – Each Plant

  • Individual, 3-stage filters with 0.3 µm filtration

  • Mass flow control

    • Thermal-convective flow signal loop

    • Operator-entered set point

    • Blower PLC compares and adjusts

    • Auto start of standby compressor


Design major elements each plant2
Design: Major Elements – Each Plant

  • Manual control

    • Operator-entered IGV setting

    • Blower PLC maintains setting

  • Blower protection – automatic


Design cost saving features 1
Design: Cost Saving Features – 1

Blower Building

  • Pre–engineered metal building

  • Manual gantry; not bridge crane

  • Loading dock; not drive in






Design cost saving features 2
Design: Cost Saving Features – 2

  • Aeration Basins

    • Painted steel air piping

    • Manual air balancing to basins

    • Single set of DO monitoring

    • No gas cleaning features



Modus operandi north plant
Modus Operandi – North Plant

  • Process demand driven

  • Automatic mode (mass flow)

  • Periodic operator adjustments

  • Target DO 0.5 to 2.0 mg/L


Performance comparison north plant
Performance Comparison – North Plant

  • Flow and BOD loading changes

  • HP and unit power changes

  • ML Temperature – up

  • FESS – up



Fine bubble aeration system 1994 96 to 2003 comparison north plant
Fine Bubble Aeration System Plant1994/96 to 2003 Comparison –North Plant



Fine bubble aeration system design predictions to 1994 96 comparison north plant
Fine Bubble Aeration System PlantDesign Predictions to 1994/96 Comparison – North Plant

  • Data availability constrained assumptions


Cost analysis capital expense
Cost Analysis: Capital Expense Plant

  • Total capital cost: ~$2.7M (incl. Eng.)

  • NMPC grant: ~$0.9M (incl. Eng.)

  • ACSD Net cost: ~$1.8M (for 2 plants)


Cost analysis o m north plant
Cost Analysis:– O&M North Plant Plant

  • Power costs (1.36%/yr)

  • Labor (4.26%/yr) and material increases

  • DWP up – more power

  • Maintenance costs


Average cost kwh north plant 1996 2003
Average Cost kWH North Plant Plant1996 – 2003


Cost analysis est maintenance cost 1
Cost Analysis: Est. Maintenance Cost – 1 Plant

  • Compressors

    • Oil and filter changes

      • Every 2 years of operation; test oil annually

      • Using ACC Roto-H oil ($1,000/yr for all 4 units)

    • “Schedule C” Maintenance – @ 30,000 hrs ($5,000 /ea.)


Cost analysis est maintenance cost 2
Cost Analysis: Est. Maintenance Cost– 2 Plant

  • Inlet air filters (say $1,000/unit-yr)

    • Roll filter changes too frequent

    • Roll filters replaced with disposable sheets

  • Diffusers – gas cleaning

    • North Plant – cleaned 1x/year ($9,000)

    • South Plant – not cleaned


Payback analysis overall project electrical costs 9 years
Payback Analysis: Overall Project - Electrical Costs (9 years)

  • Estimated based upon power cost

  • Present value to before project (i=8%)

  • Compare to $1.8M



Payback analysis single vs multi stage north plant
Payback Analysis: – Single vs. Multi-stage – North Plant Plant (20 yrs.)

  • Capital Cost Assumptions

    • Blowers and installation – factored

    • Assume others equal

    • Cost of money (i=8%)

  • O&M Cost

    • Power cost inflation (1.36%)

    • Labor and material inflation (3%)

    • S/S maintenance/filter changes ($2500/yr)

    • M/S maintenance/filter changes ($1500/yr)



Operator comments 1
Operator Comments – 1 units)

  • Operation – satisfied with equipment performance

  • One of the best features – automatic compensation for air temperature


Operator comments 2
Operator Comments – 2 units)

  • ACC single stage compressors:

    • Operator friendly

    • Minimal maintenance

  • Schedule “C" maintenance (4 compressors):

    • Machines are still like new, bearings, guide vane, gears, etc.

    • Quality of inlet air cited.


Operator comments 3
Operator Comments – 3 units)

  • Power meters – a big help in trending operator costs

  • D.O. control:

    • 24/7 staffing

    • NYSERDA study –D.O. control conversion payback long (that clinches it !!! )


Operator comments 4
Operator Comments – 4 units)

  • Why project turned out so well:

    • ACSD Staff input

    • Sufficient # of trains converted

    • Time spent on loadings to get design parameters, etc.


Engineer s perspectives 1
Engineer’s Perspectives – 1 units)

  • General

    • Get involved

    • Provide best data (diurnal, seasonal, daily, etc.)

    • Turn-down often issue

    • Look at non-electrical O&M costs, too (carefully)

  • Match technology and operational philosophy/experience


Engineer s perspectives 2
Engineer’s Perspectives – 2 units)

  • Single-stage blowers

    • For wide variations in air requirements

    • For higher pressure situations

    • Bigger units (2 S/S vs. 3 M/S)

    • New approaches (match with multi-stage)

    • Control features


Engineer s perspectives 3
Engineer’s Perspectives – 3 units)

  • Maintain System Efficiency

    • Baseline/Monitor performance (auto.)

    • Perform regular maintenance (e.g. gas clean diffusers)

    • Automate operation (e.g. filter blinding; lag start)

    • Grid DO control?

    • Time of day/demand management


Wrap up
Wrap-up units)

  • Review Key Points

  • Questions/Comments


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