Municipal Wastewater Efficiency Improvements

Potential Savings for the 6th Power Plan

September 30, 2008Regional Technical Forum

South Treatment Plant - Renton,Washington

Municipal Wastewater Industry in the PNW• Over 800 Plants use 175 aMW of Energy• 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– Lighting

DO Control from wateronline.com

Blower from spenserturbine.com

Fine Bubble Diffusters from sequencertech.com

5th Power Plan Summary• Technical Potential

Retrofit Measures = 50.5 aMW New Construction = 14.5 aMW

65.0 aMW

• Plan called for a total of 37 aMW of energy savings at 1.4 cents/kWh.

Achievements since 5th Plan• Energy Trust of Oregon:

– 23 Projects– Savings = 1.5 aMW– Measure Cost = $10 million

Update for 6th Plan: Data SourcesVariable Source(s) DataNumber of Plants in PNW, by type

5th Plan Assumptions2001 Quantum survey of facilities in PNW, and facility type

Growth Council Population ProjectionsNeeds met assuming 50% increased plant utilization and 50% increased capacity

Plant Utilization 2004 EPA Clean Watersheds Needs Survey Average Flow and Design Capacity for PNW Facilities

5th Plan AssumptionsAggregated results of BacGen/Quantum Survey of 194 Facilities in PNW and CA

Phone calls to 9 Large Plants in PNW (represent over 40% of the capacity in Large PNW plants)

Design and Average flow, energy consumption, and generation

PG&E Benchmarking Study Design and Average flow, and energy use of 9 plants

2008 "Importance of EE to W&WW Sector" paper by M. Yonkin

Energy Use per treated water by plant size

PNW BacGen Projects through 2003 (n=17) Energy Use (and flow)

5th Plan AssumptionsEnergy savings per flow, through conversations with Industry

2006 NYSERDA Sub Metering Study 11 submetered sites

PNW BacGen Projects through 2003 (n=17) Energy Savings (and flow)

Long Term Monitoring and Tracking Report on 2006 Activities: BacGen (Summit Blue, 2007)

Energy Savings (and design capacity) from 33 facilities

2006 NYSERDA Sub Metering Program Detailed measure cost for 11 sites

ETO - Ted Light Total measure cost for 23 facilities

O&M Costs & Savings 2006 NYSERDA Sub Metering Program Detailed O&M benefits (and costs) for 11 sites

Achieved Energy Savings ETO - Ted Light Total energy savings and number of sites

Measure Cost

Baseline Energy Consumption

Energy Savings Potential

Proposed Changes to Savings

5th Plan Assumptions (2005)Million

kWh/MGD (flow)

Plant Utilization

Number of Plants

Total Capacity

(MGD)Total Annual Flow (MGD)

Total Energy Consumption

(aMW)

Energy Savings

Potential

Savings (million kWh per MGD

flow)Energy Savings

Potential (aMW)< 1 MGD 1.347 75% 276 96 72 11 30% 0.40 31 to 10 MGD 1.347 75% 114 396 297 46 25% 0.34 11> 10 MGD 1.347 75% 49 1,612 1,209 186 9% 0.16 22

1.439 75% 121 319 239 39 30% 0.43 121.131 75% 281 153 115 15 25% 0.28 4

842 2,575 1,932 297 53Proposed 6th Plan Assumptions (2010)

Million kWh/MGD

(flow)Plant

UtilizationNumber of Plants

Total Capacity

(MGD)Total Annual Flow (MGD)

Total Energy Consumption

(aMW)

Energy Savings

Potential

Savings (million kWh per MGD

flow)Energy Savings

Potential (aMW)< 1 MGD 1.347 70% 289 100 70 11 30% 0.40 31 to 10 MGD 1.347 67% 119 414 275 42 12% 0.16 5> 10 MGD 0.493 74% 51 1,684 1,239 70 9% 0.04 6

1.439 67% 127 333 222 36 30% 0.43 111.131 70% 294 160 112 14 25% 0.28 4

880 2,691 1,918 174 29

Lagoon Extended AerationLagoon Aerated/Mixed

Activated Sludge

Lagoon Extended AerationLagoon Aerated/Mixed

Activated Sludge

Treatment Type

Treatment Type

More on Savings

Data Source NSavings (million kWh/MGD flow)

< 1 MGD 3 0.591 to 10 MGD 3 0.14> 10 MGD 3 0.05< 1 MGD 9 0.691 to 20 MGD 23 0.16> 20 MGD 1 0.04

NYSERDA Submetering (activated sludge)

BacGen Projects (all plant types) (assumes 67% plant utilization rate)

Change large activated sludge plant baseline consumption because:

Change % savings available to medium activated sludge plants because:

Proposed Changes to Cost & Benefits

5th Plan AssumptionsMeasure Cost per

kWh SavedO&M & NEB per

kWh Saved B/C Ratio< 1 MGD 0.19$ 0.30$ 4.91 to 10 MGD 0.06$ 0.07$ 8.4> 10 MGD 0.07$ 0.27$ 31.0

0.09$ 0.09$ 7.90.43$ 0.33$ 4.0

Proposed 6th Plan Assumptions (2010)Measure Cost per

kWh SavedO&M & NEB per

kWh Saved B/C Ratio< 1 MGD 1.10$ 0.10$ 1.41 to 10 MGD 0.49$ 0.10$ 3.2> 10 MGD 0.48$ 0.03$ 2.2

0.49$ 0.10$ 3.21.10$ 0.10$ 1.4

Activated Sludge

Lagoon Extended AerationLagoon Aerated/Mixed

Treatment Type

Activated Sludge

Lagoon Extended AerationLagoon Aerated/Mixed

Treatment Type

Data Source NMeasure Cost per

kWh SavedO&M & NEB

per kWh Saved< 1 MGD 3 $1.10 $0.101 to 10 MGD 3 $0.49 $0.10> 10 MGD 3 $0.48 $0.00

23 $0.73 ?

NYSERDA Submetering

ETO Projects5th Plan Assumptions:• Measure Cost:

– $20k to $200k depending on size (or about $0.10/kWh)

• O&M Costs:– $500/mo service agreement

• Non Energy Benefits:– $34k/year per facility for

reduced manual DO sampling– $5/day for reduced polymer

purchased in AS systems– $10k-25k/MGD for reduction

in solids

Summary – 6th Plan Proposal

• New Construction Savings– Projected Additional Capacity: 288 MGD– Projected Additional Load: 20 aMW– Technical Potential: 3.3 aMW

• Retrofit Savings– Technical Potential: 27.5 aMW