Municipal Wastewater TreatmentPreliminary Seventh Power Plan
Energy Efficiency EstimatesOctober 14, 2014
West Point Wastewater Treatment Plant, Seattle Washington
Municipal Wastewater Industry in the PNW• Over 1100 Plants use 140 aMW of Energy
– Sixth Plan: 893 plants, 137 aMW
• Processes Include– Collection– Treatment
• Sludge Processing & Disposal
– Discharge
Picture from: Arkansas Watershed Advisory Group
The Many Factors that Affect Plant Energy Consumption
• Influent Biological Oxygen Demand (BOD)• Effluent BOD• Weather/Location• MGD design capacity • MGD flow• Primary Clarifier Effectiveness• Secondary Treatment Process Type
– Activated Sludge• Coarse or fine bubble aeration• Dissolved Oxygen control method
– Aerated Lagoon• Dispersed Aeration or Mechanical Aeration• Varying amounts of aeration
– Trickle Filter– Disinfection method (Chlorine or UV)
• Tertiary Treatment Process Type• Sludge Treatment Processes
– Dewatering method– Digestion
• Onsite Generation (IC Engine or Micro-Turbine Using Digester Gas, Micro-Hydro at discharge, etc.)
Lebanon, OR
Energy Savings Measures• Energy Savings Measures
– VFDs – Upgrade to premium efficiency motors– Aeration blower control via automated dissolved oxygen monitoring– Fine bubble diffusers– Optimize pumping and blower configurations and operation/controls– Upgrade to more efficient pumps and blowers– Use hydraulic digester mixing & optimize mixing time
DO Control from wateronline.com
Blower from spenserturbine.com
Fine Bubble Diffusters from sequencertech.com
Sixth Plan Summary• Technical Potential: 36.0 aMW (for reference, the Fifth Plan
technical potential was 65 aMW)• Achievable potential at a levelized cost of $16/MWh.
Achievements since Sixth Plan• From the BPA Six Going on Seven Project:
– Savings = 6.07 aMW (2010 – 2012, approximately 2 aMW per year)– Well aligned with 6P ramp rates– Assume 10 aMW for
2010 - 2014
2010 2011 20120.00
0.50
1.00
1.50
2.00
2.50
Wastewater Treatment EE Ramp Rate
Energy Variables
• Baseline– Number of WT facilities – EPA 2008 data (6P was 2004 data)– Treatment flow (Million Gallons per Day, MGD) – EPA 2008– Energy Consumption(Million kWh/MGD) – same as Sixth Plan
• Growth – Council population forecast• Assume a 0.5% annual increase in efficiency – from Sixth
Plan• EE potential (kWh/MGD) – same as Sixth Plan• Saturation – From BPA “Six Going on Seven” project (6
aMW 2010-2012, assume 10 aMW through 2014)
Proposed Changes To Savings
Sixth Plan Assumptions
Sub Category Count
Sum Capacity (MGD)
Sum Flow
(MGD)
Avg Flow
(MGD)
Annual energy
use/Volume (mmkWh/ MGD flow)
Total Wastewater
Consumption (MWa)
Estimated Savings (million
kWh/MGD flow)
Estimated Total
Savings Potential (aMW)
Estimated Average Savings Rate (%)
Average Facility use
(kWh)
Average Facility Savings (kWh)
<1 MGD 678 151 106 0.16 2.11 26 1.29
15.6 61%
330,143
201,836
1-10 MGD 176 578 385 2.2 0.87 38 0.29
12.7 33%
1,896,714
634,355
>10 MDG 40 1,479 1,088 27 0.59 73 0.06
8.0 11%
16,172,843
1,768,800
All 893 2,208 1,579 1.77 137 36
Proposed Seventh Plan Assumptions – Net of Accomplishments
<1 MGD 905 205 119 0.13 2.11 29
0.96
13.1 45%
278,336
126,520
1-10 MGD 210 701 430 2.05 0.87 42
0.21
10.6 25%
1,770,805
440,345
>10 MDG 35 1,310 1,015 29.27 0.59 68
0.05
5.6 8%
17,273,572
1,404,645
All 1,150 2,216 1,565 1.36 140 29
Savings values adjusted for achievements
Cost Variables
• Measure cost– Sixth Plan, adjusted for 2012$– Recent project experience and data for first-year cost
- $0.41/kWh (Cascade data), $0.71/kWh (Energy Trust)
– Not enough variation by size • O&M Cost/Benefit
– Used Sixth Plan values, adjusted to 2012$– Source was NYSERDA study 2006 (Detailed O&M
benefits and costs for 11 sites)
Proposed Changes To Costs
Sub Category
Measure Cost
($/kWh)
O&M and NEB's
($/kWh)
Average Facility
Measure Cost
Average Facility Annual O&M and
NEB'sMeasure Cost per MGD Flow
O&M and NEB per
MGD Flow
<1 MGD $ 0.49 $ 0.03 $ 99,558 $ 5,594 $ 637,762 $ 35,837 1-10 MGD $ 0.57 $ 0.03 $ 360,276 $ 17,583 $ 164,322 $ 8,019 >10 MDG $ 0.20 $ 0.03 $ 360,838 $ 49,027 $ 13,167 $ 1,789
Sub Category
Measure Cost
($/kWh)
O&M and NEB's
($/kWh)Average Facility Measure Cost
Average Facility Annual O&M
and NEB'sMeasure Cost per MGD Flow
O&M and NEB per MGD
Flow<1 MGD $ 0.55 $ 0.031 $ 69,107 $ 3,883 $ 525,094 $ 29,506
1-10 MGD $ 0.63 $ 0.031 $ 276,938 $ 13,515 $ 135,293 $ 6,603 >10 MDG $ 0.23 $ 0.031 $ 317,311 $ 43,113 $ 10,841 $ 1,473
First Year Cost Notes: - Cascade database: $0.41/kWh (N=105) - Energy Trust: $0.71/kWh (N=21) Adjusted measure and O&M
cost for 2012 dollars, from 6P 2006 dollars
Summary and Next Steps
• Summary– Achievable potential approximately 28 aMW– Preliminary levelized costs approximately
$12/MWh• RTF Input
– Finalize with existing data or is more research needed?
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