Transcript Adding Whey for Denitrification

Adding Whey for Denitrification
Dale Adams, P.E
Managing Engineer, Colorado Springs Utilities
September 8, 2015
Electricity | Natural Gas | Water | Wastewater
Adding Whey for Denitrification
Agenda
Background
Nitrogen Removal
Phosphorous Removal
Benchtop fermentation of whey
Full scale design
Problems with start-up
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 2
Adding Whey for Denitrification
Background
• Whey is a by-product of cottage cheese production
• A Dairy approached Colorado Springs Utilities to say they
would find a way to dispose of whey to avoid BOD
surcharge
• Utilities analyzed the whey – thought to be a good source of
carbon
• JDPWRRF was limited on carbon for its biological treatment
processes
• Plant effluent pH was too low – had to add sodium
hydroxide to raise effluent pH - $100K per year
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 3
Adding Whey for Denitrification
Background
• Temporary tanks were installed in 2009 and the dairy trucked
cottage cheese whey to fill the tanks
• During the pilot project whey was dosed to the inlet of the
primary sedimentation tanks
• As winter approached, the decision was made to move the
whey operation into a spare grit tank to keep the whey from
freezing and use the grit tank pump to dose the whey
• This allowed a larger inventory to be maintained and some
fermentation occurred
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 4
Adding Whey for Denitrification
Nitrogen Removal
• Ammonia conversion to nitrogen gas is a multi-step
biologically driven process
• One set of bacteria (nitrifiers) takes ammonia to nitrite then
to nitrate under aerobic conditions (lots of air is blown into
the basins to give the bacteria oxygen)
• Another set of bacteria (denitrifiers) take nitrate to nitrite
under anoxic conditions (very low oxygen) and then to
nitrogen gas which goes to the atmosphere; requires
CARBON for this step
• The conversion of nitrate to nitrogen gas adds alkalinity
back into the wastewater – raising the plant’s effluent pH
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 5
Adding Whey for Denitrification
JDPWRF - Activated Sludge Effleunt (ASE) Nitrate Concentrations (mg/L)
16
Whey Addition
14
AS Effluent Nitrate (mg/L)
ASE Nitrate (mg/L)
12
Aged Whey Ef f ect
10
8
6
4
2
0
07/20/2009
08/09/2009
08/29/2009
09/18/2009
10/08/2009
10/28/2009
11/17/2009
12/07/2009
12/27/2009
01/16/2010
Date
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 6
Adding Whey for Denitrification
JDPWRF - Final Effluent Alkalinity (mg/L)
120
Final Effluent Alkalinity (mg/L)
110
Final Effluent Alkalinity (mg/L)
100
90
80
70
60
50
Whey Addition
40
30
20
07/20/2009
08/09/2009
08/29/2009
09/18/2009
10/08/2009
10/28/2009
11/17/2009
12/07/2009
12/27/2009
01/16/2010
Date
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 7
Adding Whey for Denitrification
Phosphorus Removal
• Was not occurring at JDPWRRF very much prior to
whey addition
• Biological P removal requires several things:
• First an anaerobic zone is needed (no oxygen)
• Second, volatile fatty acids need to be present
• Under these conditions bacteria dump phosphorous and store
the VFA as energy
• Under subsequent aerobic conditions, bacteria take up twice as
much phosphorous
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 8
Adding Whey for Denitrification
JDPWRF - Final Effluent Ortho-phosphate Concentrations (mg/L)
Final Effluent Ortho-phosphate (mg/L)
14.00
12.00
Whey Addition
Final Effluent Ortho-phosphate (mg/L)
10.00
Aged Whey Ef f ect
8.00
6.00
4.00
2.00
0.00
07/20/2009 08/09/2009 08/29/2009 09/18/2009 10/08/2009 10/28/2009 11/17/2009 12/07/2009 12/27/2009 01/16/2010
Date
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 9
Adding Whey for Denitrification
Benchtop Fermentation Experiments
• Set up a reactor
• Fed it fresh whey at a rate that controlled the hydraulic
residence time
• Temperature was maintained at 94 F – the temp that we
receive cottage cheese whey from the dairy
• pH was maintained at 5.7-6.0
• VFAs were analyzed to see what was happening with
fermentation
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 10
Adding Whey for Denitrification
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 11
• Adding Whey for Denitrification
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 12
Adding Whey for Denitrification
Design of Full-scale Carbon Facilities
• Whey is very a very dilute source of carbon
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 13
Adding Whey for Denitrification
Design of Full-scale Carbon Facilities
• Dairy may not stay in the cottage cheese business
• Need to design for flexibility
• Tanks were designed to handle whey, primary sludge,
and acetic acid (could not make them compatible for
methanol)
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 14
Design for Handling Whey
• Two tanks, each 35,000
gallons
• Telescoping valves for scum
removal
• Mixer in main chamber
under fermentation mode
• Connection from tank
headspace to odor control
ductwork in existing PSTs
• Special coatings systems to
withstand a variety of
chemical action
• Waterproofing membrane
on outside
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 15
Process Schematic
Future PS
Screens
pH Control Pumps
Telescoping
Valves
Future Mixers
Control Valves and
Flow Meters
Mixers
Tank Drain/Future PS
Recirc. Pumps Pumps
1/16/2015
Feed Pumps
Slide 16
Primary sludge fermentation
• Up to two more
tanks, each
35,000 gallons
• Combination
submersible tank
drain/future PS
recirculation
pumps to be used
• Additional mixers
will be installed
• FRP baffles will be
installed
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 17
Start-up Problems
• Started up the whey tanks with pH control set at 5
• Shortly after start-up ground settlement broke the
feed piping – 20 foot deep excavation and repair
was completed
• After the repair bio-P and nitrogen removal have
not responded like we saw during the pilot project
• The dose location is different than during the pilot
project
• We have not had time yet to do a deep dive into
why the system is not performing as expected
1/16/2015
Electricity | Natural Gas | Water | Wastewater
Slide 18