Illinois Section AWWA/WEA Amrou Atassi, P.E.

, BCEE –
Principal Engineer
Springfield, IL
March 20, 2012

Tale of Three Cities – Case Studies of

Aeration System Energy Efficiency
Improvements
 Acknowledgements

• Steve Poulos; Valparaiso, IN

• David McCollum; Marion, IN
• John Calise; Benton
• Randy Rogers, David Tucker, and Ben Finnegan; CDM Smith
 Outline

• Background
• Aeration Efficiency Opportunities
• Case Studies
– Marion, IN
– Valparaiso, IN
– Jacksonville, IL
 City of Chicago Total Electricity Use with
MWRDGC
Approximate City Use:
1,800,000,000 kWh/year

255 Mil. kWh

838 Mil. kWh
Street Lighting
Water/Wastewater Utilities
275 Mil. kWh
O’Hare Airport

52 Mil. kWh
Midway Airport

33 Mil. kWh
Traffic Controls

126 Mil. kWh

Park District

227 Mil. kWh

General Services
 Representing 40 to 60% of a Typical Wastewater Treatment
Plant’s Electrical Energy Use, Diffused Aeration Air Blowers
(and Turndown Thereof) Provide a Primary Focus for Energy
Savings

Misc. Electricity
Misc. Electricity Uses
Uses
Solids
Handling/
Solids Handling/
Processing
Processing
Diffused
RAS/WAS Aeration
RAS/WAS Pumping Pumping
Diffused Aeration
Channel Aeration Channel
and/or Mixing Aeration and/or
Mixing

Raw Sewage/
Effluent Pumping
Plants with Raw Sewage/ Plants without Raw Sewage/
Effluent Pumping Effluent Pumping
The Diurnal Dry Weather Flow Pattern of Most
WWTPs Presents the Opportunity for Turndown

Historical Dry Weather Diurnal Flow Pattern

 Turndown of Multi-Stage Centrifugal Blowers

Inlet (Suction) Valve

Throttling

Speed Control
Via Variable
Frequency Drive
Images Courtesy of HSI
Diffused Aeration System Energy Use is Highly
Influenced by Blower Type
M

Silencer
PIT
To Other
Aeration
Basins
Running FIT M AIT

Starting Aeration Basin

Stopped
Start
Stop
Single-Stage
Centrifugal Start/Stop
M M Blower Station

Multi-Stage Positive High-Speed

Centrifugal Blower Displacement Blower Turbo Blower
CASE STUDIES
 Marion, IN

• 16 MGD WWTP
• Three 300-HP PD Roots
blowers (installed in the
1960’s)
• Relatively inefficient (and
noisy) operation
• Suction and discharge
silencers
 Energy Efficiency Grant to Replace Blower

OED Grant
• Replace 300-HP PD blower
with 300-HP high speed turbo
blower
• 6-Month project schedule
from Award/NTP
• ARRA
• Davis Bacon
• Grant from Indiana OED for
$250,000
 Project Payback
• Old condition:
–Three 300-HP PD blowers operating with VFDs (blowers are 30
to 40 years old)
–One blower is typically operated at 60% speed of 3000
SCFM
• New condition:
– One blower can meet most flow conditions at higher efficiency

Average
Energy
Daily % Daily Energy Estimated Installation
Cost
Condition Electricity Energy Savings per Cost / Calculated Simple
Savings per
Use Savings Year (kWh) Payback Period
Year
(kWh)
Existing Blowers 3,200 - - - -
Replaced one 300-HP
PD blower with 300- 2,100 34 % 400,000 $32,000 $250,000/7.8
HP high-speed blower
Blower Capacity

• Old Blower rated

for 5000 CFM
• New Blower can
provide over 7000
CFM of air when
needed
 Valparaiso, IN

• Two 400-HP and two 200-HP

centrifugal blowers (~ 10 years
old)
• Efficient, but not optimized
operation
• Made significant
improvements to the primary
treatment system
TSS Reduction
BOD Reduction
Reduction in Required Aeration CFM
 Comparison of Blower Turndown Techniques: Inlet
Valve Throttling versus VFD Throttling

Design Condition
3560 (RPM) 8000 ICFM @ 8.5psig

3480 (RPM)

3190 (RPM)

3030 (RPM) (63% Open)

(42% Open)
(32% Open)

10HP

Legend
73HP
Full Speed/
Un-throttled
Characteristics 75HP
Inlet Valve
Throttled
Characteristics
VFD Throttled
Characteristics
 Energy Efficiency Grant for VFD Addition

OED Grant
• Add two 200-HP VFDs on
existing 200-HP blowers
• Trim/modify impeller to allow
for high turndown
• Replace existing motors with
premium efficiency motors
• 6-Month project schedule
from Award/NTP
• ARRA
• Davis Bacon
• Grant from Indiana OED for
$250,000
Blower Modification & Surge Control
 Project Payback
• Old condition: Continuous operation of 200-HP out
of two 200-HP and two 400-HP multistage centrifugal
blowers
– No VFDs, Inlet valve throttled at 60%, approx. 40% of total
WWTP electricity use of the aeration blowers
• New condition:
– Higher turndown of aeration blowers
– Reduced energy use from VFDs and premium efficiency motors
Average
Energy
Daily % Daily Energy Estimated Installation
Cost
Condition Electricity Energy Savings per Cost / Calculated Simple
Savings per
Use Savings Year (kWh) Payback Period
Year
(kWh)
Existing Blowers 3,600 - - - -
Existing Blowers
modified w/new
impellers and installed 2,500 30 % 400,000 $32,000 $200,000/6.25
VFDs on two 200 HP
blowers
 Jacksonville, IL

• Four 300-HP centrifugal

blowers
• Inlet valve control (throttled
up to 50%)
• Efficient, but not optimized
operation
 Options and Payback
•Current condition: Continuous operation of 1 out of 4
multistage centrifugal blowers
– No VFDs, Inlet valve throttled at 50%, 44% of total WWTP
electricity use
• Energy use evaluation provided two recommendations to
improve efficiency:
–Automated control of inlet valve throttling by either a
dissolved oxygen or raw sewage flow control loop
–Installation of a high speed turbo-type centrifugal blower
Average
% Daily Energy Energy Cost Estimated Installation Cost /
Daily
Condition Energy Savings per Savings per Calculated Simple Payback
Electricity
Savings Year (kWh) Year Period
Use (kWh)
Existing Blowers 4,300 - - - -
Existing Blowers with
Increased Levels of Inlet 3,400 20 % 329,000 $26,000 $40,000 / 1.6
Valve Throttling

New High Speed Turbo-type

2,200 49 % 767,000 $61,000 $250,000 / 4.1
Blower with Onboard VFD
 Thank You.

Questions?

AtassiA@cdmsmith.com