Transcript 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 [email protected]. 550 W.

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
[email protected].
550 W Cypress Creek Rd
Suite 400
Fort 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
Other
(HVAC,
Lighting), Backwash,
5%
6%
Raw
Water
Pumps,
31%
Main
Zone
Pumps,
37%
High Zone
Pumps,
21%
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 Study
Task 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 Preparation
Task 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
To Storage &
High Service
Pumping
Sand
Strainers
Cartridge
Filters
Membrane
Softening
Aeration/
Degasification
Energy Audit Results at WTPs
Example: Lime Softening and Ozone
Cost of
Improvement
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
$ 800
$ 1,600
2
Category II
$ 99,400
$ 182,600
Recommendation
Motion sensors
TOTALS
Estimated Pay
Back Period
Category
Estimated Annual
Savings
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Energy Audit Results at WTPs Example:
Membrane Softening
Recommendation
Estimated Annual
Savings
Cost of
Improvement
Estimated 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
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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
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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
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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
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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
Summary
 Holistic 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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