Reducing Energy Costs in Water and Wastewater Treatment Systems

Cory Johnson, P.E. CH2M HILL

Eastern US Practice Lead for Water Treatment, Membranes, and Reuse

Cory.johnson@ch2m.com.550 W Cypress Creek Rd

Suite 400Fort Lauderdale, FL 33309

954.351.9256

Managing Energy Improves Sustainability while Reducing O&M Costs Energy costs are rising Annual energy cost of:

• A Florida utility was $5.2M (2005) operating one WWTP (>30mgd) and 4 WTPs (ranging is size from 14 to 30 mgd)

• A Georgia utility was ~$5.5M per year to operate two WTPs (170 mgd total capacity)

A 5% to 10% energy cost savings could result in of $250k to $500k annual savings

Energy Audit, Energy Management? Energy Management Studies are

not just ‘electrical’• Energy efficiency evaluation process is

a multi-disciplinary task– Evaluation team should include Process,

Electrical, I&C, and HVAC Engineers, Operational Specialists, and Economists

• Energy costs are a function of electrical, process, operations, and controls --- and economists!

Water Plant Energy Management

Pumping is typically ~90% of water system energy use

Ways to save energy cost:• Operational Optimization

– Chemical – Energy

• Operational and Capital Improvements

• Rate Structures

Backwash, 5%

High Zone Pumps, 21%

Main Zone Pumps, 37%

Raw Water Pumps, 31%

Other (HVAC, Light-ing); 6%

Example where Smarter Operations Resulted in Significant Savings

Distribution system hydraulic model used to refine the existing operating plan to meet more strict water quality regulations and minimize operating costs for a 10 mgd system

25% reduction in energy cost with Energy Market rate and revised pump controls and operations

How to Perform an Energy Management Study

Steps to Perform an Energy Management StudyTask 1: Project Kickoff and Chartering Task 2: Pre-Site Visit Review (Homework)

– Review plant specific data– Familiarize with current operational procedures and control strategies– Analyze electrical bills– Evaluate plant electrical one-line diagrams– Identify major energy intensive processes (pumping, generation technologies, UV

disinfection, blowers, HVAC, lighting)– Generate preliminary list of ideas for energy saving measures

Task 3: Facility Evaluations (Site Visits)– Interview plant operational staff– Verify motor name plate data and confirm ‘run time’ on motors– Review processes which can be shifted to ‘off peak’ hours– Discuss and review control strategies for energy intensive processes– Review rate structures with operational staff

Steps to Perform an Energy Management Study (cont’d)Task 4: Data Evaluation and Modeling

– Create a baseline energy usage model

– Simulate existing plant operation and energy usage to calibrate

– Run ‘what if’ scenarios by simulation of process and pumping various operating conditions

– Evaluate control modifications to assess potential energy savings

– For energy saving opportunities that require capital expenditures, compute:

• Capital Cost

• Annual Energy Savings

• Payback period

– Estimate energy savings from shifting operations to ‘off-peak’

– Recommend electrical modifications to take advantage of rate structure

Task 5: Report PreparationTask 6: Final Workshop and Presentation

Areas of Focus during Assessment Evaluate the energy rate structure

• Identify peak and off-peak periods and any power factor penalties

• Investigate feasibility of installing power factor improvement capacitors

Evaluate installation of energy monitoring equipment which can be interfaced into the SCADA system

Evaluate lighting to recommend ways to save energy by better control of lighting circuits

Recommend improvements in the electrical systems that would improve efficiency, reliability, and safety

Investigate major pumping systems Evaluate all plant treatment processes Evaluate HVAC systems

Categorization of Assessment Recommendations Summarize and categorize each recommendation

with “pros and cons” for each category Category #1: “Low Hanging Fruit”

– Can be almost immediately implemented– No capital cost– Reasonable energy savings

Category #2: Actions requiring minimum to moderate capital investment with payback of 1 to 5 years

Category #3: Actions that may require significant capital investment, but could pay back in 5 to 7 years

Water and Wastewater Plant Assessment Examples

Example Water Treatment Plant Process Flow

Softening Aeration Media Filtration Transfer Pumping

Well Pumping

SandStrainers

Cartridge Filters

Membrane Softening

Aeration/ Degasification

To Storage & High Service Pumping

Energy Audit Results at WTPs Example: Lime Softening and Ozone

RecommendationEstimated Annual

SavingsCost of

ImprovementEstimated Pay Back Period

Category

Ozone Operation $ 5,600 $ 16,000 2.8 Category II

Converting to LOX $ 65,000 $ 165,000 3.1 Category III

High Service pump $ 28,000 $ 0 0 Category I

Motion sensors $ 800 $ 1,600 2 Category II

TOTALS $ 99,400 $ 182,600

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RecommendationEstimated Annual

SavingsCost of

ImprovementEstimated Pay Back period

Category

Membrane Operations $ 16,500 $ 0 0 Category I

Degasifier Operations $ 11,415 $ 0 0 Category I

Concentrate / IW #3 $ 21,300 $ 90,000 4.4 Category III

TOTALS $ 49,215 $ 90,000

Energy Audit Results at WTPs Example: Membrane Softening

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Examples of Energy Audit Results at WTPs

Pump sizing vs. valve throttling• 25 well pumps (75 to 100 hp)• Discharge valves throttled to maintain well

drawdown and reduce pressure to match RO facility requirements

• 2.7 million kW-hr of additional energy used ---- additional $150,000 in annual energy costs

• Program implemented to replace all the pumps with 40 to 50 hp motors with AFDs

OSHG Programming Logic Modifications• Modified programming logic to change

generation time from peak hours of 12pm to 9pm to off peak hours of 12am to 9am

• $18k annual cost savings

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Efficient Pump Combinations

BEP

• $$

BEP

• $$

Wastewater Pump Station Analysis – Operational Changes

15 MGD system Review pump curve efficiencies, power draw, runtimes, and energy bills Recommended alternate operating scenarios for pump station to

maximize existing efficiency Analysis of cost for running one

pump versus two pumps at 70% or 80% capacity.

Identified that to pump the same amount of water, it can cost 50% less using two pumps versus one, in 30% less time.

Results vary based on pump curves.

FOG and Codigestion

What is Codigestion?

Direct addition of high-strength organic wastes to municipal wastewater anaerobic digesters

Typical high-strength organic wastes• Fats, oils, and grease (FOG)• Restaurant food scraps• Food processing wastes • Off-spec cola syrups• Dairy wastes• Cheese Wastes• Brewery Wastes• Winery Wastes• Others

Advantages of Codigestion

Technical• Removes FOG from sewer collection systems• Removes FOG materials from headworks and primary

clarifiers• Removes organic loadings on liquid treatment train• Increases digester utilization

Economic• Produces more biogas for beneficial uses (CHP, dryer,

vehicles, etc.)• New revenue streams from tipping fees• Reduces O&M costs for headworks and liquid

treatment trains Environmental

• Reduces landfilling of high-strength wastes (HSW)• Reduces emission of greenhouse gases

Challenges of Codigestion

Possible need for digester upgrades

Additional capital and O&M costs for FOG/HSW receiving and processing

Additional paperwork for permitting, waste receipts, billings

Debris removal and disposal Potential negative anaerobic

digester performance impacts Potential anaerobic digester

toxicity from HSW Potential increase in nutrient

concentrations in sidestreams

Johnson County, Kansas Middle Basin WWTP – 12.5 mgd (14.5 mgd Capacity)

Process Flow Diagram

FOG/HSW are blended sequentially with primary sludge and thickened WAS

Project Financials

Capital cost of codigestion and cogeneration Improvements $10,000,000

Annual FOG/HSW tipping fee revenue $300,000

Annual electrical power from biogas $400,000

Alternative Financing through Performance Contracts

Performance Based Contracts with Energy Services Companies

Energy Service Company (ESCo or ESCO) based project (certification required)

ESCO has become a generic term for Energy Performance Contracts

Started in 1970s with lighting, developed in 1980s with hospitals and matured in 1990s with buildings (HVAC, lighting, building energy management)

Today moving from buildings to all aspects of energy efficiency (street lighting, traffic control, water and wastewater operations)

International Performance Measurement and Verification Protocol (IPMVP) used to measure before and after energy use

Typically use “Performance Contracting” to finance and implement projects as part of a Guaranteed Energy Performance Contract (GEPC)

Finance is normally from the private sector

Guaranteed Energy Performance Contracting (GEPC)

GEPC evaluates a project or a program and develops an agreement with a fixed (guaranteed) capital cost and operational savings for the program• Much like a Design Build agreement• Added in is the energy performance guarantee

Methods of capital investment• Utility floats bond based on program value (not common)• Outside financing• Inside financing

The contractor capital or the bond is paid back with savings from program (e.g., shared savings concept)

Government regulated terms and conditions usually 10 to 20 year term for payback (formal ESCO)

GEPC Contractor financed projects normally self limited to investment in projects with 3 to 10 year payback

Services Covered by Energy Performance Contracting

Anything related to energy or green related savings including:• Standard Energy Conservation Measures – Lights, traffic lights, HVAC controls,

etc.• Non-revenue water reduction• Bio-solids reduction• Digester gas to energy production• Water metering – reduction of non-revenue water • Pumping savings (water distribution, wastewater collection)• Distribution system optimization• Wastewater treatment mechanical upgrades (e.g., blowers) and process

upgrades• Adding renewable energy to the utility’s portfolio (normally blended approach)• Energy procurement strategies to reduce overall energy costs

Driving Factors for a Energy Performance Contract

Driving Factors for a Energy Performance Contract Utility does not have

financial capacity (e.g., lacks bonding capacity)

Utility wants to holistically look at their energy consumption and carbon footprint

Utility knows that there is a project but not sure of the details or how to finance

Risk Transfer

Driving Factors for Convention Project Approach Utility has financial capacity Utility knows exactly what

project they want – no variables

Limited Project Risk

Case Study - Wilmington, DE – Operational and Capital Improvements with ESCO Funding

Wilmington serves 100,000 people MGD

Cash strapped city with big “Green” expectations

Period of performance is 20 years as per Delaware state ESCO law

Program designed to:• Reduce energy and operational costs• Reduce GHG emissions• Insulate the City from future electricity

and biosolids cost escalation through renewable energy generation and sludge volume reduction

Phase 1 of the program includes city‐wide energy conservation measures, peak demand reduction and solar  generation Over $400,000 in annual net savings

through renewable generation, energy use reduction and energy price reduction

Approximately $180,000 of construction period savings have already been realized

The City has received national recognition for its successful deployment of ARRA stimulus funds for renewable energy and infrastructure improvement

Phase 2 intended to provide a long term biosolids management solution

Cogeneration of inexpensive renewable fuel (methane) will supply plant electric demand and heat for thermal drying of biosolids

Thermal drying will reduce biosolids volume by over 80% and eliminate cost and regulatory uncertainties associated with off-site trucking/land application

Combined, both phases result in 50% of City’s energy demand supplied by renewable generation and achievement of 20% greenhouse gas reduction goal under the Climate Protection

Closing Thoughts

Summary

Water and Wastewater Treatment Continue to Increase in Energy Intensity• As water quality regulations become tighter, kW-hr/MG increases

Significant Opportunities to find Energy Savings in Plants and Piping Systems

Energy management studies are a multi-disciplinary effort and focused on more than just ‘electrical’

Level of effort can be tailored to specific studies

SummaryHolistic plant optimization studies can incorporate

chemical feed optimization FOG programs represent a potential revenue source

and additional fuel source when considering codigestion

ESCOs and GEPCs can bring funding for projects using energy savings

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