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1 A Look Back Nine Years RMWEA Operators Seminar 10/29/04 Single Stage Compressors As Part of a Fine Bubble Diffused Aeration Retrofit at the Albany County.

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Presentation on theme: "1 A Look Back Nine Years RMWEA Operators Seminar 10/29/04 Single Stage Compressors As Part of a Fine Bubble Diffused Aeration Retrofit at the Albany County."— Presentation transcript:

1 1 A Look Back Nine Years RMWEA Operators Seminar 10/29/04 Single Stage Compressors As Part of a Fine Bubble Diffused Aeration Retrofit at the Albany County Sewer District Daniel W. Clayton

2 2 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)

3 3 Contact Information Daniel W. Clayton, P.E. Principal Engineer, Brown and Caldwell 1697 Cole Blvd., Suite 200, Golden CO – Phone: Richard J. Lyons Superintendent of Operations, Albany County Sewer District (ACSD) PO Box 4187 Albany, NY Phone: (518) Peter Kyriacopoulos – District Sales Manager Atlas Copco Comptec (ACC) 20 School Rd. Voorheesville, NY Phone:(518) Glenn Shultz (Alternate Contact)– Product Manager Atlas Copco Comptec (ACC) 20 School Rd. Voorheesville, NY Phone: (518)

4 4 Introduction/Outline – 1 Background/project motivation Design Assumptions Single-stage compressor technology Operating Data Operating Cost

5 5 Introduction/Outline – 2 Payback Operators comments Engineers perspective Comments/questions

6 6 Background/Project Motivation ACSD – two activated sludge plants Treat primarily for BOD & TSS w/ seasonal nitrification

7 7 Process Schematic – North and South Reprinted from: ACSD 2003 Annual Report

8 8 North Plant Performance Reprinted from: ACSD 2003 Annual Report

9 9 South Plant Performance – 2003 Reprinted from: ACSD 2003 Annual Report

10 10 Mechanical Aeration Systems Three tanks in service Single and dual-speed aerators PLANT No. OF TANKS IN SERVICE TANK L x W (ft) No. of Aerators Average running HP North3 of 6260 x South3 of 4195 x

11 11 Why Replace the Surface Aerators? 20+ years old Repair frequency increasing NMPC contractor study showing projected savings (7/92) NMPC grant eligible

12 12 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%

13 13 Planning: Design Assumptions – 2 Average Daily Conditions Plant BOD 5 (1) Removed (lb/d) NH 3 (2) Removed (lb/d) Total (3) AOR (lb/d) Air Requirements (scfm) Process (4) C = 2 mg/l Process (5) C = 1 mg/lMixing (6) North12,9501,64021,7207,6706,7806,500 South7,9501,15013,9904,9504,3704,850 Max. Month Conditions Plant BOD 5 (1) Removed (lb/d) NH 3 (2) Removed (lb/d) Total (3) AOR (lb/d) Air Requirements (scfm) Process (4) C = 2 mg/l Process (5) C = 1 mg/lMixing (6) North14,4001,96024,8008,7607,7406,500 South12,6001,52020,8007,3506,5004,850 Source: MPI Design Memorandum

14 14 Planning – Cost Considerations Capital Equipment Support Facilities O&M Single stage electrical cost savings significant (vs. multi-stage) Other costs not given large consideration

15 15 Single Stage Features – 1 Energy efficiency at design point Energy efficiency at turn-down (IGV; 9% better than throttling valve) Overall 70% efficiency projected

16 16 Single Stage Features – 2 Wide range of flow/custom tuning PLC – available for control use Meet demanding industry standards (e.g. API)

17 17 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

18 18 Design: Major Elements – Each Plant Three tanks with ceramic disk diffusers One single-stage compressor on, one standby PLANT No. OF TANKS IN SERVICE NO. OF DIFFUSERS PEAK AIR FLOW (per diffuser) North3 of 67,000 8,760 (1.3) South3 of 46,000 7,350 (1.2)

19 19 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

20 20 Design: Major Elements – Each Plant Manual control Operator-entered IGV setting Blower PLC maintains setting Blower protection – automatic No D.O. control (monitor)

21 21 Design: Cost Saving Features – 1 Blower Building Pre–engineered metal building Manual gantry; not bridge crane Loading dock; not drive in

22 22 North BB Exterior 1

23 23 North BB Exterior 2

24 24 North BB Interior 1

25 25 North BB Interior 2

26 26 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 (bid option)

27 27 North BB Exterior 3

28 28 Modus Operandi – North Plant Process demand driven Automatic mode (mass flow) Periodic operator adjustments Target DO 0.5 to 2.0 mg/L

29 29 Performance Comparison – North Plant Flow and BOD loading changes HP and unit power changes ML Temperature – up FESS – up

30 30 Fine Bubble to Mechanical Aeration Comparison – North Plant AERATION SYSTEM AVE. FLOW (mgd) SECOND. BOD TREATED (lb/day) ML TEMP. ( °C ) FESS (mg/L) kWH/lb BOD TREATED AVE. HP COST kWH (CENTS)$/Day Mechanical (Sep 93 – Aug 94) , Fine Bubble (Sep 94 – Mar 96) , Delta % –4.0– –38–40–3.6–42

31 31 Fine Bubble Aeration System 1994/96 to 2003 Comparison – North Plant AERATION SYSTEM AVE. FLOW (mgd) SECOND. BOD TREATED (lb/day) ML TEMP. (°C) FESS (mg/L) kWH/lb BOD TREATED AVE. HP COST kWH (CENTS)$/Day Fine Bubble (Sep 94 – Mar 96) , Fine Bubble (2003) , Delta % 28–6.5–

32 32 Unit Power Consumption – North Plant

33 33 Fine Bubble Aeration System Design Predictions to 1994/96 Comparison – North Plant AERATION SYSTEM Ave. Air (scfm) AVE. BHP Max. Month Air (scfm) Max. Month BHP Fine Bubble (Design) 7, , Fine Bubble (Sep 94 – Mar 96) 10, , Delta % Data availability constrained assumptions

34 34 Cost Analysis: Capital Expense Total capital cost:~$2.7M (incl. Eng.) NMPC grant:~$0.9M (incl. Eng.) ACSD Net cost:~$1.8M (for 2 plants)

35 35 Cost Analysis:– O&M North Plant Power costs (1.36%/yr) Labor (4.26%/yr) and material increases DWP up – more power Maintenance costs

36 36 Average Cost kWH North Plant 1996 – 2003

37 37 Cost Analysis: Est. Maintenance Cost – 1 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.)

38 38 Cost Analysis: Est. Maintenance Cost– 2 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

39 39 Payback Analysis: Overall Project - Electrical Costs (9 years) Estimated based upon power cost Present value to before project (i=8%) Compare to $1.8M PLANT (conv. date)Gross SavingsPresent Value North (8/94)$864,000$601,000 South (9/94)$1,330,000$919,000 Totals$2,190,00$1,520,000

40 40 Payback Analysis: – Single vs. Multi- stage Power – North Plant (20 yrs.) Parameter Mechanical Mixers North Plant Single Stage Theoretical Multi-stage (+12%) Average HP Average KW Initial Unit cost ($/KWH; 1994)0.076 Base value of power ($/yr)287,000188,000210,000 Savings average annual ($) 111,00085,700 Savings 20 present value ($) 1,030,000800,000 Savings in Present Value ($) 230,000 Capital Cost ( Est. $) 1.2M0.90M

41 41 Payback Analysis: – Single vs. Multi- stage 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)

42 42 Payback Analysis: – Single vs. Multi- stage – 400+HP (2 units) Parameter Scenario 1Scenario 2Scenario 3 Average HP ,000 Average KW Unit cost ($/KWH; 1994)0.076 Base value of power ($/yr)198,400347,500496,700 Inefficiency (%)12 Initial value of power ($/yr)222,200389,200556,300 Initial value of O&M ($/yr) 2,5003,5004,300 Initial value of Overhaul ($/yr) 10,00014,00017,300 12% Ineff. 20 present value ($) 2,530,0004,310,0006,160,000 Base 20 year Present Value ($) 2,220,0003,870,0005,520,000 Difference in Present Value ($) 310,000440,000640,000

43 43 Operator Comments – 1 Operation – pleased with equipment performance One of the best features – automatic compensation for air temperature

44 44 Operator Comments – 2 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.

45 45 Operator Comments – 3 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 !!! )

46 46 Operator Comments – 4 Why project turned out so well: ACSD Staff input Sufficient # of trains converted Time spent on loadings to get design parameters, etc.

47 47 Engineers Perspectives – 1 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

48 48 Engineers Perspectives – 2 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

49 49 Engineers Perspectives – 3 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

50 50 Wrap-up Review Key Points Get involved Provide best data Perform meaningful comparisons Automation/instrumentation Electrical billing, future and incentives Questions/Comments

51 51


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