Upload
trinhkhue
View
228
Download
0
Embed Size (px)
Citation preview
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Optimizing a Pure Oxygen Wastewater Treatment Plant
Randal W. Samstag, PE, BCEE Principal Technologist
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
2
Outline
• HPO Basics • HPO Upgrade Case Studies
– West Point WWTP Pilot Plant – Bellingham Post Point WWTP
• Conclusions
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
3
The High Purity Oxygen (HPO) Process
• Invented by Union Carbide Corp. in early 1970s • “High Purity Oxygen”
– Cryogenic Plant (95 – 99%) – Pressure Swing Adsorption (88 – 93%) – Vacuum Swing Adsorption (88 – 93%)
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
4
HPO Upgrade Case Studies
• West Point WWTP HPO Pilot Plant • Bellingham Post Point WWTP
– HPO Modifications Project – Nitrogen Removal Upgrades
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
5
West Point WWTP
Pilot Plant
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Wef2003Samstag.ppt
West Point HPO Test Facility
• 4-stage HPO pilot facility (Lotepro) – 20-30 gpm – SRT: 1-2 days
• Mar - Dec 1988
• 3 modes evaluated: – Plug Flow – Contact/Reaeration – Anaerobic Selector w/ Plug Flow
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
7 Wef2003Samstag.ppt
HPO Test Facility Schematic
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
8
Settleability Data from HPO Test Facility
0 100 200 300 400 500 600 700 800 900
SVI,
mL/
g
Min Ave Max
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Wef2003Samstag.ppt
The Culprits
• Microscopic evaluation found filaments
– Thiothrix II
– Type 021N
• Sulfur oxidizing aerobes
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Influence of SRT and Temp on PAO
0
2
4
6
8
10
12
14
10 15 20 25 30
Temperature (Degrees C)
Was
hout
Aer
obic
SR
T (D
ays)
Nitrifier Washout Nocardia Washout PAO Washout
EBPR
EBPR and Nitrification
No EBPR
Mammais and Jenkins, 2001
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
PAO Have Higher Floc Density
• PAO form Neisser-positive cell clumps
• Compact flocs settle faster than highly filamentous sludges
• Bio P organisms have a higher density than typical zoogleal or filamentous organisms
Schuler and Jang, 2007
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
12
Bellingham Post
Point WWTP
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
The Bellingham Post Point WWTP
• 20 mgd capacity HPO activated sludge plant
• 10 ton/day pressure swing absorption HPO system
• Three HPO basin stages
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
14
Settleability History
• Average SVI of 170 mL/g from 1999 to 2004 • Filament caused settleability problems
– Type 1701 (Low DO) – Type 1863 (Low SRT)
• Periodically high VFA feed from influent sewer and from solids dewatering operation 3-4 days per week leading to slime bulking
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
15
Idea for Improvement – Anaerobic Selector
• Provide zone for uptake of VFA • Encourage growth of phosphorus accumulating
organisms (PAO) • Increasing population distribution of PAO increases floc
density • PAO have a compact morphology and higher density than
other typical activated sludge bacteria (Schuler and Jenkins)
• Experience at three other HPO plants (SE Essex SD, Hyperion, SE San Francisco)
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
16
The HPO Modifications Project
• Improve settleability by converting first stage to anaerobic selector
• Replace aerators to improve oxygen transfer • Add variable speed drives to mixers to improve
control and save power • Selectors added capacity for interim operation until
major capacity upgrade could be completed
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
SVI History Before and After Conversion to Anaerobic Selector
Comparison of SVI and MCRT
0
50
100
150
200
250
300
350
07/17/05 12/14/05 05/13/06 10/10/06 03/09/07 08/06/07 01/03/08 06/01/08
SVI (
mL/
g)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
MC
RT
(Day
s)
SVI 7/Avg ml/g MCRT 7/Avg Days
Aerobic
Anaerobic
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
The Original Aerators
• Conventional conically shaped low speed aerators with bottom impellors
• Estimated standard aerator efficiency (SAE) - 3.2 pounds of oxygen per hour per horsepower
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
New Aerators
• m2t Technologies • Flat-bladed surface
aerators without bottom impellers
• Initial estimate of SAE (second stage conditions) – 4.0 pph/hp
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Low Speed Testing for First Stage Aerators
• Tested to deliver 0.5 ft per second velocity at the bottom of the test tank at low speed in first stage (anaerobic / aerobic)
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
High Speed Testing
• Test-tank tested at approximately 3.9 pph/hp under high speed conditions simulated for second stage
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Simulation of Variable Speed Control
• Simulations by Michael Stenstrom of UCLA indicated up to 35% savings in power with VSD control
• Savings only occur when aerators are under-loaded 2
4
6
8
10
12
14
16
0 5 10 15 20 25
DO1DO2DO 3
Dis
solv
ed O
xyge
n C
once
ntr
atio
ns
(mg
/L)
Time (hours)
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Summary Comparison Performance
Description Aerobic (2006) Anaerobic (2007) Difference (%)
O2 (tpd) 7.2 6.7 -6.8%
O2 (lb/mgal) 1,291 1,212 -6.5%
O2 (lb/lb BOD) 1.21 1.15 -5.7%
SVI (mL/g) 155.71 126.77 -22.8%
Estimated Mixer Power (hp)
222.2 125 -77.9%
Estimated Oxygen Power (hp)
215.2 201.6 -6.8%
Estimated Total Power (hp)
437.5 326.6 -34.0%
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
24
Project Budget
• Total cost - $670,000 • Puget Sound Energy grant - $330,000 • City of Bellingham cost - $340,000
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
25
Comparison of Operating Modes Actual Bellingham Operation
HPO Operation - 2006 • 100% Aerobic • 2.2 Days Aerobic SRT • 157 mL/g SVI • 2,400 mg/L MLSS
Anaerobic Selector Operation - 2007
• 67% Aerobic • 1.6 Days Aerobic SRT • 126 mL/g SVI • 2,900 mg/L MLSS
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
26
Comparison of Operating Modes Actual Bellingham Capacity
HPO Operation - 2006 Anaerobic Selector
Operation - 2007
20 MGD Capacity 22 MGD Capacity
10 Percent Increase
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
27
What About BNR Conversions?
• Concerns about HPO – CO2 accumulation -> low pH -> suppresses
nitrification – As SRT increases HPO becomes less and less
economical compared to fine bubble – Examples:
• LOTT (Olympia, Washington) • Denver Metro • Indianapolis • Bellingham • All abandoned HPO for BNR
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
28
Oxygen Supply Cost as function of SRT
$0
$100
$200
$300
$400
$500
$600
$700
$800
1.5 2.5 8.0
Uni
t Cos
t of O
xyge
n ($
/ton)
SRT (Days)
HPO: New VPSA HPO Plant AAS: New Diffused Aeration System
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
29
HPO Conclusions
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
30 Wef2003Samstag.ppt
Conclusions from the HPO Test Facility
• Anaerobic selectors at the HPO test facility failed because low SRT, low temperature prevented formation of an environment supportive of EBPR. PAO were washed out.
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
31
Conclusions from the Post Point Project
• Anaerobic selector provided a way to control settleability by encouraging PAO and taking up excess VFA
• Improved oxygen transfer efficiency of new aerators saved power
• Variable speed control of DO provided power savings and improved process control
• The upgrade provided a 10 Percent capacity increase for interim operation
• For BNR upgrade, fine bubble was more economical
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Thank you!
Questions?
Randal Samstag
206-684-6532 (office)
206-851-0094 (mobile)
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
33
Generalized Conclusions about HPO The Initial Claims Experience
• Less O2 consumption • O2 consumption depends more on SRT than on DO
• Better settling sludge • Little evidence of better settleability at a given SRT
• Can operate at a higher MLSS • If settling is not better, no justification for higher MLSS
• Smaller tank volume required • If settling is not better, no justification for smaller tanks
• More power efficient than conventional aeration
• Power efficiency depends on SRT
• Can be used for nitrification • High CO2 decreases pH and inhibits nitrification
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
34
MLSS Showed Indications Phosphorus Accumulating Organisms
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
35
Recent SVI and SRT Data from West Point WWTP
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
0
50
100
150
200
250
300
350
400
450
12/4/05 12/4/06 12/4/07 12/3/08 12/3/09 12/3/10
SRT
(Day
s)
SVI (
mL/
g)
West Point SVI and SRT Data
SVI SRT (day) Linear (SVI) 30 per. Mov. Avg. (SVI) 30 per. Mov. Avg. (SRT (day)) Linear (SRT (day))
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
Summary Comparison Operation
Description Aerobic (2006)
Anaerobic (2007)
Difference (%)
Flow (mgd) 12.2 12.1 -0.8%
BOD (ppd) 12,852 12,994 1.1%
MLSS (mg/L) 1,763 2,057 14.3%
Total SRT(days) 2.2 2.4 6.5%
Aerobic SRT (days) 2.2 1.6 -40.3%
DO (mg/L) 13.3 7.4 -78.8%
Temp (Deg C) 17.57 17.24 -1.9%
O2 Purity (%) 88% 89% 1.4%
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
37
Comparison of Operating Modes Typical Operating Assumptions
Classical HPO Operation • 100% Aerobic • 1.5 Days Aerobic SRT • 200 mL/g SVI • 1,700 mg/L MLSS
Anaerobic Selector Operation
• 85% Aerobic • 2.5 Days Aerobic SRT • 120 mL/g SVI • 2,200 mg/L MLSS
Car
ollo
Tem
plat
eWat
erW
ave.
pptx
38
Comparison of Operating Modes Capacity Impact
Classical HPO Operation Anaerobic Selector
Operation
13 MGD Capacity 17 MGD Capacity
30 Percent Increase