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?