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Transcript of Innovative Phosphorus Control to Turn Struvite … · Innovative Phosphorus Control to Turn...
Innovative Phosphorus Control to Innovative Phosphorus Control to Turn Struvite Headaches into Turn Struvite Headaches into
Increase RevenueIncrease Revenue
Peter Schauer, Rob Baur, Brett LaneyPNCWA 2010
2
Contents
Where does the phosphorus go in BPR?How can WASSTRIP improve recovery?Benchtop Testing…but can it be modeled?Pilot TestingWhat did we learn?
3
Phosphorus Removal in BPR Plants
Phosphorus accumulates in the cell mass and is removed with the daily waste activated sludge Anaerobic solids processing – release of P, Mg, and N in recycle streams
Some metal phosphate precipitation in sludge Struvite precipitation in sludgeRemaining released Mg, P and ammonia in return streams
20 – 30% of the phosphorus load on the activated sludge process is in the recycle streams
4
Thickener
SludgeSludge
ThickenerFermentorFermentor
Anaerobic DigestionAnaerobic Digestion
Dewatering CentrifugeSolids to Land Application
Primary Treatment(Sludge Settles to Bottom)
90% Phosphate Removed20% Ammonia Removed
Ostara Reactor
Crystal GreenR
Slow Release Struvite Fertilizer Pellets5-28-0 10%MG
Chemical Sludge
Secondary Treatment(Bacteria Break Down Organics)
Thickening
Struvite recovery in return streams
5
WAS and VFA-rich fermentate combined in release tankDiverted to recovery process in liquid after thickeningLess favorable conditions for struvite in digesters
US patent 7,604,740 that protect the WASSTRIP system and process technological advances, and world-wide patent rights are reserved to Clean Water Services, Oregon, USA.
Patent Pending
6
What do we need to know about WASSTRIP
Design information for stripping tankHow much VFA needed to strip phosphorus?The rate of P and Mg release in the tank?Production of ammonia?Impact on downstream processes?Can it be modeled with BioWin?
8
Truckee Meadows WWTPRelease during endogenous fermentation and when adding VFA Relatively fast initial release (<16 hours)Short SRT BPR plant
020406080
100120140160
0 20 40 60 80Time, hours
Pho
spho
rus
Con
c, m
g/L
EndogenousWith Acetic Acid
0.0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80Time, hours
Rel
ease
Rat
io, M
g/P
EndogenousWith Acetic Acid
0
10
20
30
40
50
0 20 40 60 80Time, hours
Mag
nesi
um C
onc,
mg/
LEndogenousWith Acetic Acid
9
Empire WWTP
Endogenous releaseAchieved >50% releaseSteady release for 70 hours
050
100150200250300350400
0 50 100 150Time, hours
Pho
spho
rus
Con
c, m
g/L
Test 1Test 2Test 3
0%10%20%30%40%50%60%70%
0 50 100 150
Time, hours
Rel
ease
as
% o
f TP
Test 1Test 2Test 3
10
Laboratory Test
Anoxic conditions maintained using closed containersTwo tests using VFA additionOne endogenous release test
11
Endogenous Release Tests
Mg : P release – consistentPhosphorus release from PAO up to 48 hours 0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 20 40 60 80 100 120Time, hours
Rel
ease
Rat
io, m
g M
g / m
g P
020406080
100120140160180200
0 24 48 72 96 120Time, hours
Con
cent
ratio
n, m
g/L NH3-N
VFA
0
50
100
150
200
250
0 24 48 72 96 120Time, hours
P R
elea
sed,
mg/
L o-PO4Mg
12
VFA-Enhanced Release – Round 1
Results from P were inconsistentResult from Mg showed little additional release with more VFA
05
10152025303540
0 50 100 150 200Time, min
Mg
per
L of
WA
S, m
g75 mg VFA / L RAS186 mg VFA / L RAS374 mg VFA / L RAS571 mg VFA / L RAS0
20
40
60
80
100
120
140
0 50 100 150 200Time, min
P pe
r L
of W
AS,
mg
75 mg VFA / L RAS186 mg VFA / L RAS374 mg VFA / L RAS571 mg VFA / L RAS
13
VFA-Enhanced Release – Round 2
Very little difference in release rates based on VFA addition
020406080
100120140160
0 100 200 300Time, min
Con
c, m
g O
P/L
of W
AS
119 mg VFA/L RAS185 mg VFA/L RAS278 mg VFA/L RAS417 mg VFA/L RAS
0
5
10
15
20
25
30
35
0 100 200 300Time, min
Con
c, m
g M
g/L
of W
AS119 mg VFA/L RAS185 mg VFA/L RAS278 mg VFA/L RAS417 mg VFA/L RAS
14
VFA-Enhanced Release
Summary of VFA to VSS ratios
Round 1mg VFA / mg VSS
Round 2 mg VFA / mg VSS
Test 1 0.010 0.015
Test 2 0.025 0.023
Test 3 0.051 0.035
Test 4 0.077 0.051
15
Modeling Results – Endogenous
Anaerobic hydrolysis from 0.5 – 0.025
0
50
100
150
200
250
300
0 50 100 150Time, hours
P C
once
ntra
tion,
mg/
L
Lab DataModeling Data
0
50
100
150
200
250
300
0 50 100 150Time, hours
VFA
Con
cent
ratio
n, m
g/L
Lab DataModeling Data
16
Modeling Results – VFA-EnhancedPAO Sequestration rate from 6 day-1 to 0.45 day-1
VFA sequestration half-saturation rate was changed from 5 mg/COD/L to 0.03 mg COD/L
0
20
40
60
80
100
120
0 100 200 300Time, min
Con
cent
ratio
n, m
g/L
Test #1 Model #1Test #2 Model #2Test #3 Model #3Test #4 Model #4
Phosphorus
Magnesium
17
Implications of Modeling
0.000
0.001
0.002
0.003
0.004
0.005
0.006
0.00 0.02 0.04 0.06 0.08 0.10VFA / VSS
P re
leas
e R
ate
per
VSS,
hr-1
0.0000
0.0002
0.0004
0.0006
0.0008
0.0010
0.0012
Mg
rele
ase
Rat
e pe
r VS
S, h
r-1
Phosphorus ReleaseMagnesium Release
19
Pilot Test – Operation
Started in April 2010Plant shifted into Nutrient Removal seasonAlum additionFermenter start-up
Adjusted FTO and WAS flow Detention TimeRatio of VFA to PAOs
20
Pilot Test – Results
Shift between bio-P and chem-PFermenter OperationGenerally release 20-30% of the TP
Reasonable detention timeAbove 0.15 mg VFA/mgVSS
21
Pilot Test – ResultsPercent Phosphorus Release versus VFA/VSS Ratio
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14VFA/VSS Ratio, mg/mg
% P
hosp
horu
s R
elea
se
Residence Time < 8 hr Residence Time > 8 hr
22
Pilot Test – ResultsPercent Phosphorus Release verus Residence Time
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
0 2 4 6 8 10 12 14 16Residence Time, hr
% P
hosp
horu
s R
elea
se
VFA/VSS < 0.013
0.020 > VFA/VSS > 0.013
VFA/VSS > 0.02
23
Implications for Durham AWWTF
Dry Weather
Wet WeatherScenario 1 Scenario 2 Scenario 3
WAS Flow, mgd 0.34 0.42 0.42 0.42
FTO Flow, mgd 0.58 0.58 0.58 0.58
FTO VFA Concentration, mg/L 437 203 100 100
FTO used for WASSTRIP, % 25 50 100 50
HRT, hours 10.2 7.0 5.0 7.0
mg VFA / mg VSS 0.026 0.021 0.021 0.010
24
Implications for Durham AWWTF
Dry Weather Wet WeatherScenario 1 Scenario 2 Scenario 3
FTO VFA, mg/L 437 203 100 100FTO for WASSTRIP, % 25 50 100 50
Phosphorus Release, lb/d 314 334 334 147Magnesium Released,
lb/d 103 103 103 21
Potential Struvite, lb/d 1,120 1,120 1,120 224
25
Phosphorus Mass Balance – Typical Operation
Liquid Treatment Process
Solids Treatment Process
Sludge
Influent Effluent1,400 lbs/d 30 lbs/d
1,370 lbs/d
500 lbs/d
26
Phosphorus Mass Balance – Phosphorus Recovery
Liquid Treatment Process
Solids Treatment Process
SludgeStruvite (as P)
Effluent30 lbs/d
385 lbs/d 985 lbs/d
200 lbs/d
27
Phosphorus Mass Balance – WASSTRIP
Liquid Treatment Process
Solids Treatment Process
SludgeStruvite (as P)
Influent Effluent1,400 lbs/d 30 lbs/d
385 lbs/d 985 lbs/d
200 lbs/d
25% reduction in Mg Addition
28
Conclusions
Appears to be an upper limit on impact that VFAs can have on phosphorus release rates. Release rates anticipated using existing tankage will be adequate for Phosphorus and Magnesium release using WASSTRIPChem P versus Bio P has a large influence
29
Next Steps
Determine the overall impact to the treatment plant
Overall economics
Impacts from pH
Impact on Dewaterability