energy conservation by optimizing aeration systems by tom jenkins, p.e. dresser roots, inc. vikram...

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Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael K. Stenstrom, Ph.D., P.E. C & EE Dept, UCLA

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Page 1: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation by Optimizing Aeration Systems

By

Tom Jenkins, P.E.Dresser Roots, Inc.

Vikram M. Pattarkine, Ph.D.Brinjac Engineering, Inc

Michael K. Stenstrom, Ph.D., P.E.C & EE Dept, UCLA

Page 2: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Outline• Overview

• Types of Aeration Systems, Terminology and Relative Efficiency

• Operational Issues – Cleaning and Avoiding Power Loss through Fouling and Scaling

• Blower Overview and Optimization

• Conclusion

Page 3: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Types of Aeration Systems• Mechanical or surface aerators

– High speed – 900 to 1200 RPM, no gear boxes, easy to install, high heat loss, spray issues, low efficiency

– Low speed – gear boxes to reduce RPM to 30 to 60, long lead time to install, high heat loss, spray issues, medium efficiency

Page 4: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Types of Aeration Systems• Diffused or subsurface aerators

– Coarse bubble – ¼ to ½ inch orifices, low efficiency, low maintenance, low to ultra-low efficiency

– Fine bubble or fine pore – millimeter to sub-millimeter orifices or porous media, highest efficiency, significant cleaning and maintenance issues

Page 5: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Types of Aeration Systems• Combined systems

– Jets, turbines, and aspirating devices – generally two prime movers such as a blower and a motor-gearbox, low efficiency, generally not used for new applications unless there are special concerns or needs

Page 6: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Terminology

• Efficiency– Standard oxygen transfer efficiency (SOTE) (percent

oxygen transferred)– Standard oxygen transfer rate (SOTR) (mass

transferred per unit time)– Standard aeration efficiency (SAE) (mass transferred

per unit time per unit power)

• All “standard” terminologies defined for clean water such as tap water (secondary process effluent is never suitable for clean water testing)

Page 7: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Terminology

• Process Conditions (OTE, OTR, AE)– Adjustment formulas based upon driving force,

temperature, barometric pressure, water quality, saturation concentration, etc.

– Driving force and water quality the most significant

– Driving force = (DOS – DO)/DOS

– Water quality – alpha factor, 0 to 1 !– Total correction can result in process water transfer of

only 30 to 80% of clean water transfer

Page 8: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

ASCE/EWRI Standards• Clean Water Oxygen Transfer Standard

– 1984, 1991 and 2006.

• Process Water Testing Guidelines– 1996

These two documents are quite useful in defining aeration performance, and create a “level playing” field to evaluate aeration systems and facilitate low bid or life-cycle purchase evaluations – use them!

Page 9: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Approximations (wire power)Aerator

Type SAE

lbO2/hp-h (kgO2/kW-h)

Low SRT AE

at 2 mg/L DO

High SRT AE

At 2 mg/L DO

High Speed

1.5–2.2 (0.9–1.3) 0.7–1.4 (0.4-0.8)

Low

Speed 2.5–3.5 (1.5–2.1) 1.2-2.5 (0.7–1.5)

Turbine 2-3 (1.2-1.8) 0.6-0.9

(0.4-0.6)

0.9-1.4

(0.6-0.8)

Coarse Bubble

1-2.5 (0.6 –1.5) 0.5 – 1.2

(0.3-0.7)

0.6–1.6

(0.4-0.9)

Fine

Pore 6–8 (3.6–4.8) 1.2-1.6

(0.7–1.0)

3.3-4.4

(2–2.6)

Approximations – use only as a guideline – transfer efficiency will depend on site specific conditions

Page 10: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Most Common Systems Today• Municipal Treatment Plants – fine pore

systems:– Discs, ceramic, plastic and membranes– Tubes, membranes– Panels and strips

• Municipal HPO-AS Systems – Low speed mechanical – Some new impeller designs to improve

efficiency

Page 11: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Most Common Systems Today• Lagoons, ditches, industrial systems

sometimes are best designed with alternative aeration systems due to extremely high oxygen uptake rates, odd geometries, heat loss considerations, requirements for wet installation or wet maintenance

Page 12: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Fine Pore Aeration Systems

• Why fine “pore” and not fine “bubble” ???– Fine bubbles can be created by turbines and

other mechanical devices. – Fine pore systems create bubbles by passing

air through pores or orifices

• Generally the best design choice for energy conservation, but there are issues and problems to avoid

Page 13: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Some Example Systems• Ceramic domes – legacy system

• Ceramic discs – popular today

• Membrane discs – maybe most popular at present

• Membrane tubes – popular today

• Membrane panels and strips – popular today, and among the most energy efficient

Page 14: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Ceramic Domes

Page 15: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Ceramic Discs

Page 16: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Membrane and Plastic Discs

Page 17: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

EPDM

PVC

Ceramic

EPDM

Plastic

Tubes

Page 18: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Panels and Strips

Page 19: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Efficiency Varies

• Key to overall transfer efficiency is the air flow per unit area of diffuser surface and the number of diffusers used

• More diffusers and more area creates efficiencies that are at the upper part of the fine pore range

• Few diffusers and high flow per diffusers will provide only low efficiency, at the low end of the range or even approximating lower efficiency devices

Page 20: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Fouling and Scaling

• Fine pore diffusers invariably undergo fouling, scaling and material changes that reduce efficiency

• Some type of routine maintenance program is always required: otherwise, efficiency declines to values that may be so low that they don’t justify the capital investment

• Also, back pressure may built which may prevent plant operation

Page 21: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Our Database of Full-Scale Results

• More than 20 years of observations of ~ 35 plants

• Ceramic discs, ceramic domes, membrane discs, membrane and plastic tubes, panels and strips

• New (< 1 month), Used (< 24 months) and Old (> 24 months) and cleaned

• Cleaning – tank top hosing, brushing, acid washing

Page 22: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Our Database of Full-Scale Results

• Process operation matters • Conventional, low MCRT or sludge age –

lowest efficiency• Long MCRT, nitrifying, good efficiency• Long MCRT, nitrifying, denitrifying, best

efficiency• Flow per unit area of diffuser and tank

surface is more important to defining performance that the generic diffuser type or material

Page 23: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Efficiency per process type

0.4

0.8

1.2

1.6

S

OT

E /

(

%/f

t)

3.0

3.8

4.6

5.4

S

OT

E /

(%/m

)

U SED

U SED

U SED

U SED

N EWN EW

N EW

N EW

O LD

O LD

U SED U SED

N EW

N EW

C LEAN ED

O LD

O LD

O LD

N EW

N EW

U SED

U SED

U SED

C LEAN ED

C LEAN ED

U SED

U SEDU SED

C onventiona lC onventiona lC onventiona lC onventiona lC onventiona lC onventiona lC onventiona lC onventiona l N itrify ing on lyN itrify ing on lyN itrify ing on lyN itrify ing on lyN itrify ing on lyN itrify ing on lyN itrify ing on lyN itrify ing on ly N itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tionN itrifica tion/D enitrifica tion

2 4 6M C R T (d) 13 15 17 19 21M C R T (d) 10 14 18 22M C R T (d)

CONVENTIONAL N-ONLY NDN

3.75%/m

4.30%/m

4.60%/m

S

OT

E/Z

(%

/ft)

S

OT

E/Z

(%/m

)

NEW & CLEANED

<24 mo.

>24 mo.

Page 24: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Transfer Efficiency• Here-to-fore, transfer efficiency measurements

required an expert using an off-gas analyzer, a few days of time, and thousands of dollars in fees

• A real-time off-gas oxygen transfer efficiency analyzer has been developed by the UCLA-Southern California Edison Team, with California Energy Commission Funding, and the design is in the public domain

• It is described in detail during the technical sessions

Page 25: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

0 4 8 1 2 1 6 2 0 2 4 2 8

m o n t h s i n o p e r a t i o n

0

0 . 4

0 . 8

1 . 2

1 . 6

2

2 . 4

po

we

r w

as

te /

cle

an

ing

co

st

po

we

r /

init

ial

po

we

r

1 0

1 0

1 0

1 0

1 0

2 0

2 0

2 0

2 0

2 0

2 0

2 0

2 0

3 0

3 0

3 0

3 0

3 0

3 0

3 0

3 0

3 0

4 0

4 0

4 0

4 0

4 0

4 0

Economics of Fouling

Page 26: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Summary• Fine pore systems generally, but not always

offer the best energy conservation• Fine pore systems require a dedication to

maintenance; otherwise, select different alternatives

• Reputable manufactures have valuable experience with piping and assembly – Listen to them!

• The consultant or process engineer must define the efficiency – Require this information from them!

Page 27: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Blowers

• All fine pore diffuser systems, coarse bubble systems and most combined aeration systems require blowers – they are an indispensable part of the system

• The next section describes blower types and guides for selection

Page 28: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Positive Displacement (PD)

Constant flow at constant speed

Pressure varies with load

Most common <200 hp

Energy Conservation:Most Common Blower Types

Page 29: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Most Common Blower Types

Multistage Centrifugal

Variable flow

Approx. Constant Pressure

Most common 100 < hp > 750

Page 30: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Single Stage Centrifugal

Variable flow

Pressure varies with load

High efficiency

Most common > 500 hp

Energy Conservation:Most Common Blower Types

Page 31: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Uncommon Blower Types

Regenerative

Very High Speed Centrifugal

New proprietary technology

High efficiency

Limited size range

Characteristics similar to PD

Limited to small flows and low pressures

Page 32: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower System Design Considerations

Provide lots of turndown capability

Use multiple smaller blowers

Select blowers for current requirements

Evaluate energy over range of actual near term operating condition

Page 33: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower System Design Considerations

Minimize system pressure

Most Open Valve Control for automatic

controls

Keep diffuser drop leg valves open for manual

control

Minimize diffuser pressure drop – orifice size,

diffuser configuration, clean diffusers

Page 34: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower System Design Considerations

Use automatic DO control

20% to 50% energy reduction

Newer technology IS reliable

Page 35: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower System Design Considerations

Use efficient blower control

Use technology appropriate to blower system

Integrate with basin controls

Page 36: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower Upgrades / Revamps

Collect Actual Operating Data on Process:Dissolved Oxygen (DO) Concentration

Air Flow Rates

Dissolved Oxygen (DO) Concentration

System Pressure

Minimum, Maximum, and Average for Typical Operation

Compare to Design Conditions

Page 37: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower Upgrades / Revamps

Collect Actual Operating Data on Blowers:

Number of Units Operating

Blower Power (kW) or Amps

Minimum, Maximum, and Average for Typical

Operation

Frequency of Manual Adjustments

Compare to Design Conditions

Page 38: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower Upgrades / Revamps

All Blower TypesProvide proper maintenance – filters, seals, diffuser

cleaning

Change to energy efficient motors

Add smaller blowers to achieve turndown

Combine air use for other functions (Post-Aeration,

Channel Aeration, etc.)

Update Controls

Page 39: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Blower Upgrades / Revamps

PD BlowersChange sheaves to optimize capacity

Multistage Centrifugal BlowersChange impellers to match actual

conditions

Single Stage Centrifugal BlowersChange impellers to match actual conditions

Add Inlet Guide Vanes and/or Variable Discharge Diffuser Vanes

Page 40: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Control System Techniques

All Blower Types

Automatic DO Control to match air rates to process demand

Use MOV Control to minimize pressure

Automatic starting and stopping of blowers

Parallel control instead of cascade control

Design Control System for Reasonable Payback – 2 to 5

years

Include Process Improvement in Evaluation

Page 41: Energy Conservation by Optimizing Aeration Systems By Tom Jenkins, P.E. Dresser Roots, Inc. Vikram M. Pattarkine, Ph.D. Brinjac Engineering, Inc Michael

Energy Conservation:Control System Techniques

PD BlowersUse VFDs (Variable Frequency Drives) to modulate air flow

Multistage Centrifugal BlowersVFDs to modulate air flow (with appropriate curves)

Automatically controlled inlet throttling to modulate flow and improve turndown

Single Stage Centrifugal BlowersInlet Guide Vanes and Variable Discharge Diffusers to

modulate flow and improve turndown