operational strategies to control energy billsreturn activated sludge (ras) • turn down you ras...
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Operational Strategies to Control Energy Bills
OWEA Plant Operations Workshop
May 22, 2014
Kevin Krejny
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My Goals of Presentation • Give real numbers, problems, solutions from Ohio
WRF. In regards to energy costs
• Understand your energy costs and needs
• Operational Strategies to lower energy costs
• Touch on energy purchasing strategies
• Show how to track that you are getting better
• Show that with any style or size plant, there are
energy savings available
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Western Regional WRF Montgomery County Water Reclamation (since 2008)
• Flow- Avg. 14.94 MGD Median 13.81 MGD • 12.25 MGD Summer 15.59 MGD Winter 20.0 MG Design
• TSS Loadings – Avg. 22,559 lbs Median 19,939 lbs • 22,141 lbs summer 22,960 lbs winter 55,000 lbs Design
• Ammonia Loadings – 1800 lbs per day
• cBOD Loadings – Avg. 24,628 lbs Median 23,583 lbs • 24,651 summer 24,605 lbs winter 38,400 lbs Design
• We have lots of concrete, what technology is in the concrete is old, inefficient, and creates constant headaches. But we have started to fix that.
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Other Facilities • Fairborn WRF – 4.5 years
• Clark County SW Regional WRF – 2.5 years
• Greene County – 1 year o Beavercreek WRF
o Sugarcreek WRF
o Cedarville WRF
o Clifton WRF
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kWh
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WRF Energy usage
(keep in simple)
• Aeration o Activated Sludge
o Digestion
• Pumping o Influent
o Internal plant elevation
o RAS/WAS
• Other o Lighting
• Indoor
• Outdoor
o HVAC
o Dewatering
o Ultraviolet Disinfection
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Aeration • 40-60% of total usage depending on plant type
o Activated Sludge/Aerobic Digestion - up to 60%
o Trickling Filter (pumping needs)/Anaerobic - less than 20%
o Many combinations
• Activated Sludge o Ammonia and cBOD removal
o Lower MLSS could mean less aeration (tanks) needed
o Look at ammonia effluent
• If <0.25 mg/l, likely over aerating
• Know your permit limits, no or high winter ammonia, can turn back
• Aerobic Digestion o If going landfill – weigh aeration energy costs vs. VS destruction
o Once pass 503 reg parameter (i.e. SOUR test), turn back air
o DO >2/0 mg/l can turn back aeration
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Jet Aeration vs. Fine Bubble Diffusers
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Fine Bubble Diffusers Increased Efficiency
Jet Aeration Tanks Fine Bubble Tanks
MLSS lbs solids in
aeration Instanteous
Flow average
cfm 30 min Settle
ammonia (mg/l) SVI
Average cfm
30 min Settle
ammonia (mg/l)
Average 3206 89127 16.2 3048 281 2.65 88 2026 270 1.70
% less 33.5% 3.9% 36.0%
Last year side by side comparison
Western Regional WRF
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700 HP Huffman Multistage Centrifugal Blowers
Newer technologies 10-15% more efficient
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500,000
600,000
700,000
800,000
900,000
1,000,000
1,100,000
1,200,000
1,300,000
1,400,000
0.00
0.50
1.00
1.50
2.00
2.50
aeration kWh per lb cBOD
1/1/08 to present
aeration kWh per lb cBOD influent cBOD lbs Linear ( aeration kWh per lb cBOD) Linear (influent cBOD lbs)
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Pumping • Proper sized pumps
o Likely oversized to meet peak demand that might only occur 5% of year
o Great to have various sized pumps and use combinations
o Use wet well height to help keep pumps in the proper area of pump curve
• Variable Speed Frequency Drives (VFD) o Replace old VFD’s
o 10 years old, might not be doing what they were designed to do
o Help to keep pump running in sweet spot of curve
• High/premium efficiency motors o More hours on motor, more payback with switching over
• Clean/replace Air Relief Valves (Next slide)
• Track MG pumped/kWh used o Great if pumping station separate from rest of plant
o Only true way to measure if your changes are working
o Cannot use $$$, because this cost changes yearly
o A kWh is always a kWh + a MG pumped is always a MG pumped
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400
500
600
700
800
900
1,000
1,100
1,200
1,300
kwh/MGD (PTP) after ARV Linear (kwh/MGD (PTP)) Linear (after ARV)
Variable Frequency Drive and Air Relief Valve Improvements Made in Early 2013
kwh/MG Pumped at Pre-Treatment (2008-13)
Avg 802 kwh/MG
Avg 695 kwh/MG
AVR replaced 1/1/13 VFDs Installed 2/1/13
13.3% Reduction
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Return Activated Sludge (RAS) • Turn down you RAS rates
o It is the pounds of RAS returned, not the flow
o 7,500 mg/l @ 2 MGD = 10,000 mg/l @1.5 MGD = 15,000 mg/l @ 1.0 MGD
o Benefit of increase detention time in aeration basins
o Promotes Biological Nutrient Reduction (BNR)
o Less Nitrate coming back around
o Reduces RAS pump usage
o WAS is thicker going to digester
o Reduce supernate efforts
o Less volume needed for digestion – could prevent the need for more
concrete
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HVAC • Know your staffing and building needs
• DO NOT heat/cool building to 70 degrees that people enter only once a day
• Use windows/doors to self regulate air flow and temperature needs
• Never run a heater in a blower room
• Buildings below ground rarely need Heat/AC, maybe ventilation
• Moving water will not freeze in a building
• Natural gas cheaper than electric heat, right now
• Electronics like cold not heat
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Lighting • Use motion detection to turn on/off lighting
• Outside lighting o Should evaluate how much is needed (know where people work)
o Is plant staffed 24/7 or not
o Light sensors to turn on/off daily
o You do not need to play football at a WRF
• Replace old lights with LED o Make sure they get enough hours of use
o Do not need LED on a light that is used once a day for a plant check
o Replace aging/high use lights first with LED
o The more hours a light is on, the more savings you get and faster pay back
in a LED lighting upgrade
o Adding savings of longer life, less time replacing bulbs
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FACT
• It does not matter how you are
billed for electricity, moving
electrical usage off peak and
keeping a steady load profile
all day and year will save you
money.
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Energy billing options • Tariff pricing
o What energy supplier in your area has written in numerous tariffs
o Changes several times a year, hard to follow and confirm being billed
properly
• Fixed Pricing o One set cost per a period of time
o Usually 1-2-3 years
o All inclusive
• Index Pricing o Energy price changes hourly
o Based on regional demand and usage
o Can be very good at certain times
o Can keep you up at night at other times
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•What do they all
have in common?
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Answer • They all have a Historical Peak Demand component
specific to your facility in the bill
• This can be great it you control and predict your
peaks o Peaks are set at the five highest hours, on different days, from the previous
year
o Usually set during afternoon of 90 degree plus days in July or August
o 2013 were all from one week in July
DATE HOUR ENDING PEAK LOAD (MW)
PJM RTO
7/18/2013 17 (5pm) 157,509
7/19/2013 15 (3pm) 156,077
7/17/2013 17 (5pm) 154,044
7/16/2013 17 (5pm) 151,421
7/15/2013 18 (6pm) 150,315
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Delivery Year: 2009-10 2010-11 2011-12 2012-13 2013-14 2014-15 2015-16 2016-17
DPL/Duke/AEP $ 102.04 $ 182.85 $ 116.15 $ 16.74 $ 28.37 $ 128.17 $ 134.62 $59.37
First Energy $ 102.04 $ 182.85 $ 108.89 $ 20.46 $ 28.37 $ 128.17 $ 342.30 $114.23
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SO WHAT Can you do • Turn off or back as many treatment processes as
you can for a couple hours during these days o Minimal treatment for three hours will not effect your 24 hour composite
sample that much
o Fill wet wells and turn off digester aeration
o Stop dewatering
o Stop RAS/WAS, can get caught up later by increasing rates
o Turn your aeration back as much as possible
o Remember during these 5 hottest days, you are likely to have your lowest
flows of the entire year
o If you have newer emission friendly generators you can run them to
completely get off the grid
o RICE NESHAP started 5/3/2014 reduces options to control these charges
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Running Plant generator (12 times)
hit all 5 peak hours
Money spent/ results
• Fuel = (4800 gal * $3.50)
= $16,800
• Labor = (12 days*3
hr*$35/hr*1.145 OPERS)
= $1,442
• $18,242 Spent – no DPL
bill during time ($12,
560)
•Cost of $5,682
Money saved (7/147/15)
• Doing nothing
Capacity Charge
$89,404
• We spent $5,682 to go
off the grid
• Capacity Charge for (7/14 7/15) = $5,611
• Total Savings =
$78,111
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Great Online tool • Updated regional usage every 5 minutes
https://edatamobile.pjm.com/eDataWireless/SessionManager?a=instLoad
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Block and Index Pricing • Takes the certainty of Fixed Pricing (Block) and
allows a portion of your usage to be on hourly index
pricing
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Block and Index • Can combine several accounts for the block
• Mixture of drinking water pumping and wastewater treatment
help keep a flat profile of accounts
• Lowest Block amount is 1 MW a month or 720,000 kWh per
month
• Can block of 1 MW intervals
• Can do this at anytime or amount (pricing changes daily)
• Suggest, if large enough, hire a energy broker to make these
transaction and lead you through
• If you can control energy needs through facilities for short
periods of time, you can save a lot of money
• Get to a flat load profile – Energy suppliers love knowing they have clients with consistent loads = cheaper pricing