overview of energy use both electric and gas
DESCRIPTION
A look at the City of Lima, Ohio, and its WWTP Master Plan Update. Presented by Russell Bales during AEP Ohio's Water/Waste Water Customer Seminar held at Zane State in Zanesville, Ohio.TRANSCRIPT
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Energy Workshop
December 19, 2012
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Introduction Wordelman
Overview of Energy Use
Electric Lowery
Natural Gas/Digester Gas Teague
Alternatives for Generation
and Savings Wordelman
Conclusion Wordelman
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Understand current usage
Electrical
Natural gas/digester gas
Initial screening ideas
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Electrical
Total purchased
Operating scenarios
Natural gas
Total purchased
Digester gas
Digester gas used flowmeter
Digester gas produced flowmeter
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Mo
nth
ly E
lectr
ical
Co
st
$
kW
Ho
ur
Lima WWTP Monthly Electrical Purchase
kWhr per Month
Electrcial Cost
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kW
Ho
ur
Lima WWTP Electricity Purchased vs. Consumed Benefit of Microturbines
Purchased
Consumed
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Capstone C65 microturbines consume approximately 22 cfm of biogas
Each turbine produces 60 kw electricity and 250,000 BTU/hr heat
At current energy prices this is worth about $43,000 annually
Use of the same amount of biogas for boiler heating only would be worth approximately $27,000 annually
Each unit can deliver ~ 8% of the plant’s electrical demand
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Air
flo
w M
CU
F a
nd
Millio
n G
allo
ns T
reate
d
kW
Ho
ur
Lima WWTP Monthly Electrical Purchased
Monthly kWhr
Monthly Total Airflow MCUF
Million Gallons Treated
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Av
era
ge M
on
thly
Tem
pera
ture
F.
kW
Ho
ur
Lima WWTP Monthly Electrical Purchased
Monthly kWhr
Monthly Temperature
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Screening 0.1% Grit Removal
0.2% Baxter Street 8.1%
Primary Tanks 1.5%
Aeration 35.5%
Sludge Pumps 8.4%
Final Clarifiers 0.5%
Nitrification 14.6%
Disinfection 0.2%
Digestion 9.5%
Dewatering 1.6%
Stabilization 0.1%
Admin Building 0.5%
Miscellaneous 19.3%
Breakdown of Energy Consumption %
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Screening 587 Grit Removal
1,074 Baxter Street 45,388
Primary Tanks 8,212
Aeration 198,734
Sludge Pumps 46,805
Final Clarifiers 2,576
Nitrification 81,735
Disinfection 850
Digestion 52,866
Dewatering 8,765
Stabalization 572
Admin Building 2,928
Miscellaneous 108,121
Stabilization Energy Consumption (kWhr / Month)
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Screening, $39 Grit Removal, $72
Baxter Street, $3,041
Primary Tanks, $550
Aeration, $13,315
Sludge Pumps, $3,136 Final Clarifiers, $173
Nitrification, $5,476
Disinfection, $57
Digestion, $3,542
Dewatering, $587
Stabalization, $38
Admin Building, $196
Miscellaneous, $7,244
Breakdown of Energy Consumption ($ / Month)
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0
500
1,000
1,500
2,000
2,500
3,000
3,500
0 20 40 60 80 100 120
Typ
ical
En
erg
y C
on
su
mp
tio
n (
kW
h / M
illio
n G
allo
n)
Capacity (mgd)
Basic Activated Sludge
Advanced WastewaterTreatmentAdvance WastewaterTreatment With Nitrification
Chart Adapted from the Electric Power Research Institute Water & Sustainability (Volume 4): U.S.
Electricity Consumption for Water Supply
& Treatment - The Next Half Century (March 2002)
Lima Electrical Consumption
~1450 kwhr/MG
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Lima ~19,000 kwhr/day
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Typical Daily Electric
Consumption 10 mgd WWTP
per Process* kwhr/day Lima Consumption
Influent Pumping 1402 1513 (Baxter St.)
Screening 2 20
Aerated Grit 134 36 (Not Aerated)
Primary Settling 155 274
Diffused Air Aeration 5320 6624
Secondary Settling 155 86
Chlorination 27 28
Anaerobic Digestion 1400 1762
Belt Press Dewatering 384 292
* The Electric Power Research Institute Water & Sustainability (Volume 4)
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Current electrical rate including all
charges is approximately $0.065/kWhr
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AEO 2012
Reference Case EVA IHSGI Inforum
2010 6.7
2015 6.5 7.9 7.0 6.2
2025 6.7 8.0 7.4 6.2
2035 7.1 7.6 8.1 6.2
18
Average end user cost projection in 2010 cents per kWh from several sources.
Via the Annual Energy Outlook 2012 Report, U.S. Energy Information Administration (2012)
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Minimum usage – minimum bill set on
60%
Power factor – less than 0.87
2011 – June 2012 average power factor =
85.8
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Enernoc emergency load response
program – run generators
AEP energy efficiency/peak demand
reduction program – up to 50% rebate
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Uses of Aeration
Mixing
Biological Oxygen Needs
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Mixing Control Biological Control
Average Conditions
Five Aeration Tanks 8200 cfm 7872 cfm
Influent and Effluent Channels 2306 cfm 2306 cfm
Reaeration Tank 705 cfm 705 cfm
Total 11211 cfm 10883 cfm
Mixing Control Biological Control
Average Conditions
Four Aeration Tanks 6500 cfm 7872 cfm
Influent and Effluent Channels 2306 cfm 2306 cfm
Reaeration Tank 705 cfm 705 cfm
Total 9511 cfm 10883 cfm
22
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Blowers – multistage centrifugal
Two 400 HP 4160 volt - 10,000 cfm
Two 350 HP 460 volt - 7,000 cfm
Diffusers
Aeration tanks EDI fine bubble diffusers
Channels and reaeration tank coarse bubble
Controls
Blower inlet throttling
DO monitoring
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Types of diffusers
Tank depth
Surfactants
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Electric
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PST 5-7 Total CODPrimary Effluent Total COD
DATE
11/1011/3
CO
NC
. (m
g/L
)
400
300
200
100
PST 5-7 Total COD Mass ratePrimary Effluent COD Mass Loading
DATE
11/1011/3
MA
SS
RA
TE
(lb
/d
)
50,000
40,000
30,000
20,000
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PST 5-7 Total CBODPrimary Effluent Carbonaceous BOD
DATE
11/1011/3
CO
NC
. (m
g/L
)
200
150
100
PST 5-7 Total CBODPrimary Effluent CBOD Mass Loading
DATE
11/1011/3
MA
SS
RA
TE
(lb
/d
)
20,000
10,000
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PST 5-7 TSS
PST 5-7 VSS
Primary Effluent Solids
DATE
11/1011/3
CO
NC
. (m
gV
SS
/L) 200
150
100
50
0
PST 5-7 TSS
PST 5-7 VSS
Primary Effluent Solids Mass Loading
DATE
11/1011/3MA
SS
RA
TE
(lb
VS
S/d
)
30,000
20,000
10,000
0
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PST 5-7 TKN
PST 5-7 Ammonia N
Primary Effluent Nitrogen
DATE
11/1011/3
CO
NC
. (m
gN
/L)
40
30
20
10
0
PST 5-7 TKN
PST 5-7 Ammonia N
Primary Effluent Nitrogen Mass Loading
DATE
11/1011/3MA
SS
RA
TE
(lb
N/d
)
4,000
3,000
2,000
1,000
0
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PST 5-7 Total PPrimary Effluent Total Phosphorus
DATE
11/1011/3
CO
NC
. (m
gP
/L)
7
6
5
4
3
2
1
0
PST 5-7 Total PPrimary Effluent Total Phosphorus Mass Loading
DATE
11/1011/3
MA
SS
RA
TE
(lb
P/d
)
1,000
800
600
400
200
0
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AT Pass 1
AT Pass 2
AT Pass 3
Total
Aeration Tank 1-5 Variable AirflowMaintain DO @ 2 mg/l
DATE
11/9/201211/7/201211/5/201211/3/201211/1/2012
AIR
SU
PP
LY
RA
TE
(ft
3/m
in (
20
C, 1
atm
))
15,000
14,000
13,000
12,000
11,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
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AT Pass 1 DO
AT Pass 2 DO
AT Pass 3 DO
Aeration Tank Dissolved OxygenManually Adjusted Airf low
DATE
11/10/201211/8/201211/6/201211/4/201211/2/2012
DIS
SO
LV
ED
OX
YG
EN
(m
g/L
)
10
9
8
7
6
5
4
3
2
1
0
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AT Pass 1 DO
AT Pass 1 Airflow
Aeration Tank Dissolved OxygenPotential Surfactant Effect
DATE
11/10/201211/8/201211/6/201211/4/201211/2/2012
Dis
so
lve
d O
xy
ge
n (
mg
/l)
10
9
8
7
6
5
4
3
2
1
0
Air
flo
w s
cfm
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
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Current cost of aeration ~ $13,000/month
Denitrification
High efficiency blowers
Ultrafine bubble aeration
Decouple aeration and mixing (install
separate mixing systems)
Automated blower control
Combination of options above.
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Total
26,027 MMBtu / year
$117,121 @
$4.50/MMBtu
Natural Gas
7,370 MMBtu / year
$33,165 / year
Digester Gas
16,457 MMBtu / year
$74,057 / year
Microturbine Heat Recovery
(Assume one running 24/7)
2,200 MMBtu /year
$9,900 / year
Microturbines
(Assume one running 24/7)
7,200 MMBtu / year
$32,400 / year used
Flare
2,246 MMBtu / year
$10,107 / year
Digester Heat
11,642 MMBtu / year
$52,389 / year
Building Heat
4,939 MMBtu /year
$26,670 / year
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0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
1/1/2009 1/1/2010 1/1/2011 1/1/2012
Hea
t (M
MB
tu)
Natural Gas Purchased
$33,904 $24,560 $27,230
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= $11.38/MMBtu assuming 3% inflation
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0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
1/1/2009 1/1/2010 1/1/2011 1/1/2012
Heat
(D
em
an
ded
/Req
uir
ed
) (
MM
Btu
)
Gas Lower HeatingValue
Heat Required byDigesters
Note: Assumes 80% boiler efficiency.
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0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
100,000
110,000
120,000
130,000
140,000
150,000
160,000
170,000
1/1/2009 1/1/2010 1/1/2011 1/1/2012
Gas P
rod
uc
ed
(F
t3 / d
ay)
Gas demand from one turbine
Gas demand from two turbines
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0
20000
40000
60000
80000
100000
120000
140000
160000
180000
0
10
20
30
40
50
60
70
1/1/2009 1/1/2010 1/1/2011 1/1/2012
Dig
este
r G
as (
ft3 /d
ay)
% V
ola
tile
of
feed
slu
dg
e
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40000
60000
80000
100000
120000
140000
160000
180000
0
100
200
300
400
500
600
700
800
1/1/2009 1/1/2010 1/1/2011 1/1/2012
Dig
este
r G
as
Vo
lati
le A
cid
s (
mg
/L)
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20000
40000
60000
80000
100000
120000
140000
160000
180000
0
500
1,000
1,500
2,000
2,500
1/1/2009 1/1/2010 1/1/2011 1/1/2012
Dig
este
r G
as
Alk
alin
ity
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% D
ige
ste
r L
oa
d (
ba
se
d o
n lb
s v
s /
ft3
- d
ay
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Septage and grease fed directly to the
digesters
Bring in supplemental feedstock
Digestion enhancement
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Benefits Increased gas production
Reduce grease accumulation in primaries and other tanks
Reduce biological load to aeration Challenges
Requires plant modification to accept, store, and feed grease to digester
Digester upset, grease handling, and odor control are a concern
Requires cooperation of public Drawbacks
Greater public access to the plant is likely
More supervision may be required
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Benefits Increased gas production
Reduced load to municipal landfills
Possibly some income from disposal fees (doubtful)
Community involvement in “green” project Challenges
Requires community or business support
Requires modifications to plant to bring in additional solids
Could require upgrades to handle and use additional gas if done on a large scale.
Possible digester upset without careful control Drawbacks
Increased solids management at plant
Increased complexity and labor at plant
Reduced gas production at landfill
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Benefits
Increased gas production
Increased solids destruction
Achievement of class A biosolids possible with some systems
Challenges
Limited change for improvement in gas production if done alone
Drawbacks
Capital and operational cost must be weighed against benefit
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By process
General
Baxter Street pumping
Preliminary & primary treatment
Secondary treatment
Effluent pumps
Solids processing & digestion
Electrical upgrades
Alternate energy
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By type
Process modifications
Energy generation
Reduces energy consumption
Additional ideas
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Today
Review alternatives
Brainstorming
Initial screening
Next
J&H develop alternatives
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Rules: No bad ideas
No criticism of ideas
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Brainstorming
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City selection 5 dots
J&H selection
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Channel Mixing
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Aerated channels require mixing to keep solids suspended rather than a supply of dissolved oxygen.
Aeration tanks are deeper than channels. Currently all air is pressurized to the same pressure based on aeration tank depth, which wastes energy.
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Baxter Street $36,728 Screening
$475
Grit Removal $869
Aeration Tank Air $113,598
Channel Air $47,219 / year
29% of total aeration Sludge Pumps
$37,875
Final Clarifiers $2,085
Nitrification $66,140
Disinfection $688
Digestion, 42,779
Dewatering $7,093
Stabilization $463
Admin Building $2,369
Miscellaneous $87,492
Cost of Channel Aeration ($ / year)
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Separate blower and piping to operate channel aeration at lower pressure.
Mechanical channel mixing or “pulsed bubble mixing” Benefits
Reduced energy bills (estimated $20,000 / year at current energy prices)
Nitrogen removal possible
Simpler DO control and balancing (maybe?) Problems
Capital expense ($220,000 -$300,000)
Odor control
Depleted DO in first portion of aeration tanks
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