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.
2. Introduction Wordelman
Overview of Energy Use
Electric Lowery
Natural Gas/Digester Gas Teague
Alternatives for Generation
and Savings Wordelman
Conclusion Wordelman
2
3. Understand current usage
Electrical
Natural gas/digester gas
Initial screening ideas
3
4. Electrical
Total purchased
Operating scenarios
Natural gas
Total purchased
Digester gas
Digester gas used flowmeter
Digester gas produced flowmeter
4
8. 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
8
14. 14
0
500
1,000
1,500
2,000
2,500
3,000
3,500
0 20 40 60 80 100 120
TypicalEnergyConsumption(kWh/MillionGallon)
Capacity (mgd)
Basic Activated Sludge
Advanced Wastewater
Treatment
Advance Wastewater
Treatment 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
18. 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)
19. Minimum usage – minimum bill set on
60%
Power factor – less than 0.87
2011 – June 2012 average power factor =
85.8
19
20. Enernoc emergency load response
program – run generators
AEP energy efficiency/peak demand
reduction program – up to 50% rebate
20
22. 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
23. 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
23
27. 27
PST 5-7 Total COD
Primary Effluent Total COD
DATE
11/1011/3
CONC.(mg/L)
400
300
200
100
PST 5-7 Total COD Mass rate
Primary Effluent COD Mass Loading
DATE
11/1011/3
50,000
40,000
30,000
20,000
28. 28
PST 5-7 Total CBOD
Primary Effluent Carbonaceous BOD
DATE
11/1011/3
CONC.(mg/L)
200
150
100
PST 5-7 Total CBOD
Primary Effluent CBOD Mass Loading
DATE
11/1011/3
20,000
10,000
30. 30
PST 5-7 TKN
PST 5-7 Ammonia N
Primary Effluent Nitrogen
DATE
11/1011/3
40
30
20
10
0
PST 5-7 TKN
PST 5-7 Ammonia N
Primary Effluent Nitrogen Mass Loading
DATE
11/1011/3
4,000
3,000
2,000
1,000
0
31. 31
PST 5-7 Total P
Primary Effluent Total Phosphorus
DATE
11/1011/3
7
6
5
4
3
2
1
0
PST 5-7 Total P
Primary Effluent Total Phosphorus Mass Loading
DATE
11/1011/3
1,000
800
600
400
200
0
32. 32
AT Pass 1
AT Pass 2
AT Pass 3
Total
Aeration Tank 1-5 Variable Airflow
Maintain DO @ 2 mg/l
DATE
11/9/201211/7/201211/5/201211/3/201211/1/2012
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
33. 33
AT Pass 1 DO
AT Pass 2 DO
AT Pass 3 DO
Aeration Tank Dissolved Oxygen
Manually Adjusted Airflow
DATE
11/10/201211/8/201211/6/201211/4/201211/2/2012
10
9
8
7
6
5
4
3
2
1
0
34. 34
AT Pass 1 DO
AT Pass 1 Airflow
Aeration Tank Dissolved Oxygen
Potential Surfactant Effect
DATE
11/10/201211/8/201211/6/201211/4/201211/2/2012
10
9
8
7
6
5
4
3
2
1
0
Airflowscfm
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
0
35. 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.
35
36. 36
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
47. Septage and grease fed directly to the
digesters
Bring in supplemental feedstock
Digestion enhancement
47
48. 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
48
49. 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
49
50. 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
50
51. By process
General
Baxter Street pumping
Preliminary & primary treatment
Secondary treatment
Effluent pumps
Solids processing & digestion
Electrical upgrades
Alternate energy
51
52. By type
Process modifications
Energy generation
Reduces energy consumption
Additional ideas
52
58. 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.
58
60. 60
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)
61. 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
61