Transcript Presentation

Improvements
to Reduce Energy Costs
at the
Downers Grove Sanitary District
FVOA 2010 Mini-Conference
August 19, 2010
Nick Menninga
General Manager
Downers Grove Sanitary District, Illinois
– 11/22 MGD average/peak
full treatment capacity
– Primary clarification
– Single-stage nitrification
– Tertiary sand filtration
– Anaerobic digestion
– Sludge dewatering and
aging
– Excess flow primary and
disinfection to 110 MGD
total
Areas of Opportunity
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Aeration
Pumping
Digester Gas
HVAC
Funding Sources
Aeration Project
• 50-60% of an activated sludge plant
electrical usage from aeration
• Traditional efficiency improvement: fine
bubble diffused air
• Many other opportunities exist for improved
efficiency in aeration system
Legacy Aeration System
• Various workhorse blowers
• Various aeration
tank/diffuser
arrangements
• Limited
instrumentation
and control
Improvements Identified
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New diffusers
New high-efficiency blower
Smarter use of tankage
I&C improvements
Potential electrical savings: 20%?
Blower Addition
ABS-HST Turbo-compressor
– 2400 – 6000 cfm turndown, matches existing
process demand
– low maintenance
– fits in the room
– reasonable sound levels
– adiabatic efficiency
improved from 50% to
80%
– old blowers used as backup
or for additional air if
needed
New Diffusers
Sanitaire membrane plate
diffusers
– Full-floor coverage – not
tapered
– 9” circular plates
– 10 drops per tank typical,
each with manual air-flow
control
– Oxygen transfer efficiency
(OTE) improved from 8% to
>12%
Better Use of Tankage
• Convert deep aerobic digester tank to
activated sludge service
• Remove shallow aeration tanks from
service, reserve for use during excess flow
or future process modifications
• Difficult channel interconnection required
• Part of diffuser OTE improved efficiency
Instrumentation and Control
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LDO probes (Fluoroprobes) in each tank
Blower variable speed control
Air flow meters (2 total)
Manual butterfly valves on the drops
Dissolved oxygen feedback control in plant
SCADA (Allen Bradley PLCs/Ifix)
Control Screens
Project Costs
• Total project cost
$1.4M
• Illinois Clean Energy
Community
Foundation grant of
$250,000
Electricity Savings
Downers Grove Sanitary District WWTC Historic Electric Use Per Volume
Treated
kwh used / mg treated
3000
2500
2000
1500
1000
500
0
Month-Yr
kwh/mg
avg before
avg after
• Average whole plant energy usage tracking:
– before: 1,833 kWh/MG
– after: 1,305 kWh/MG
– reduction: 1/3 of plant total electricity use/volume treated
• Payback at $0.08 per kwh: < 7 years
Pumping
Flo-Matchers
– Liquid rheostat
– 1970’s technology
– Lower flow = lower efficiency
– Similar efficiency characteristics to throttling
discharge valve
– 2 Lift stations
Recommended Improvements
• VFDs
• Level control through
SCADA (Allen Bradley
PLC/iFix)
• Expected Efficiency
Improvements: 50%?
Project Costs
• Wroble Lift Station: 2 pumps, each at
150 hp, Project Cost $44,500
• Hobson Lift Station: 4 pumps, each at
250 hp, Project Cost $78,500 (no need
to re-wind motors)
• Illinois Department of Commerce and
Economic Opportunity (IDCEO) Grant:
$36,127
Electricity Savings
1400
1200
1200
1000
800
KWH/MG
Monthly avg
Month-Yr
Avg Since
Avg VFDs
Before VFDs
Monthly
avg VFDsAvg Since
Avg Before VFDs
• Wroble: 40% reduction
• Hobson: 30% reduction
• Payback at $0.08 per kwh: 3 years
May-10
Apr-10
Mar-10
Feb-10
Jan-10
Dec-09
Nov-09
May-10
Oct-09
Apr-10
Sep-09
Mar-10
Feb-10
Aug-09
Jan-10
Jul-09
Dec-09
Jun-09
Oct-09
Apr-09
Nov-09
May-09
Month-Yr
Sep-09
Mar-09
Dec-08
Nov-08
0
Oct-08
0
Sep-08
200
Aug-08
200
Aug-09
Feb-09
400
Jul-09
Jan-09
400
600
May-09
Nov-08
Jun-09
Dec-08
600
Mar-09
Sep-08
Apr-09
Oct-08
800
Jan-09
Jul-08
Feb-09
Aug-08
1000
Jul-08
KWH/MG
Wroble Lift Station
Hobson
Electrical
Lift Performance
Station Electrical Performance
Digester Gas
• Used first for digester heat
• Previously had engine-driven blower
– No siloxane removal
– Lost cost-effectiveness after 20 years
of operation
• Desiccant dehumidification in sand
filter building
• Beginning to take restaurant grease
trap waste to bolster production
Desiccant Dehumidifier
• Displacing 30 tons (50 hp) of electricdriven dehumidification
• Displacing gas-fired heat (8,500 therms/yr)
• Indirect fired
• Solid-wheel desiccant media - Munters
X3
Project Costs
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Pilot project – equipment rental $15,000
Equipment purchase - $120,000
Installation (duct work) - $33,000
Total $168,000
Energy Savings
• Natural gas use reduction measured:
868,000 cf
• Electricity reduction estimated from audit:
350,000 kwh/yr
• Payback at $1/therm and $0.08/kwh: 4 years
HVAC
• As heat and AC package units are
replaced, upgrading to heat pumps that
use effluent water as heat sink/supply
– Grant from Illinois Clean Energy Community
Foundation for $38,400 approved this year
– Purchasing 3 units with total capacity of 30
tons, net cost around $36,000
– Expect $9,000 annual savings, 4 year
payback
• Evaluating potential for digester gas
fired unit heaters/absorption chillers
Funding Sources
• Illinois Clean Energy Community
Foundation (ICECF)
www.Illinoiscleanenergy.org
• Illinois Department of Commerce and
Economic Opportunity (DCEO)
www.commerce.state.il.us/dceo
• Illinois Environmental Protection Agency
Revolving Loan Fund (IEPA SRF)
www. epa.state.il.us/water/financialassistance/economic-stimulus/index.html
Conclusions
• Opportunities Exist for Any Budget
• Grant Funding is Abundant and Will
Improve Cost-effectiveness of Projects
• Projects Stand on Economic Merit Alone:
Green is Green
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Questions?
[email protected]