Emerging Technologies for Louisiana Waste Processing: Serpentine Plug-flow Reactor (SPFR) Dr. J....
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Transcript of Emerging Technologies for Louisiana Waste Processing: Serpentine Plug-flow Reactor (SPFR) Dr. J....
Emerging Technologies for Louisiana Waste Processing:
Serpentine Plug-flow Reactor (SPFR)
Dr. J. Sansalone, P.E. Civil & Environmental Engineering
Dr. V. SrinivasanBiological Science
Louisiana State UniversityBaton Rouge, Louisiana USA
SPFR originally developed from $12,000 of LA Sea Grant funds
• Waste sludge generally has high concentrations of TSS, VSS and COD and pathogens
• Current designs for completely-mixed anaerobic digesters require large footprints and long hydraulic retention times varying from 30 – 60 days (Metcalf and Eddy 1991)
Problem Statement
Objectives
1. Develop a small-scale anaerobic serpentine plug-flow reactor (SPFR) utilizing a force-fed fast rate digestion process for waste residual treatment
2. Demonstrate the technical feasibility at different organic loading rates and temperatures.
3. Evaluate the potential for methane production of the anaerobic digestion process
Typical bacterial growth curve in terms of numbers
Time
Log
nu
mb
er o
f ce
lls L
ag
ph
ase
Log growth phase
Stationary phase
Death phase
Source: Metcalf & Eddy, 1991
Advantages of Anaerobic Digestion
- High efficiency of organic mass removal
- Effective sludge volume reduction (30-50%)
- Energy is produced as methane
- Pathogens are destroyed
Anaerobic Digestion
Microbiological pathway of anaerobic digestion
GlucoseAmino AcidsFatty Acids
PO
Carbohydrate ProteinsLipids
Phosphorylated Organics
-34
Cells
Stabilized OrganicsAcetic PropionicLactic+Cells
Complex organics
Hydrolysis
Soluble Organics
Organics Acids
Methane CO 2
Acidogenesis Methanogenesis
Low Rate Anaerobic Digester
Standard-rate digesters or conventional anaerobic digestersNo mixing and thus a stratified condition
High rate
With heating, auxiliary mixing, thickening and uniform feeding
Two Stage
Separation of Methanogenesis from the other two phases, Hydrolysis and Acidogensis
Advanced reactors
Up-flow anaerobic sludge blanket (UASB), Anaerobic Filter (AF)Fluidized bed (FB), Anaerobic baffled digester (ABR) Expanded granular sludge bed (EGSB), etc.
Development History of Anaerobic Digester
Low Rate High Rate Two Stage Advanced Reactors
Schematic of Serpentine Plug-flow Reactor (SPFR)
Gas Vent
Effluent to biological treatment
Primary Sludge Influent
Storage Tank
Advantages of Serpentine Plug-flow
o Plug-flow pattern to partially separate the various phases of anaerobic catabolism
o Longer biomass retention time, lower sludge yields
o Resilience to hydraulic and organic shock loading
o Increased resistance against toxic materials
A flow rate of 500 GPD with a corresponding HRT of 48 hours was applied to investigate the feasibility of
the reactor for sludge treatment
Parameters measured: TSS, VSS, Total COD, Dissolved COD, Alkalinity, pH, Temperature
Experimental Design
Results
Statistical Data for Digester Performance
Total COD TSS VSS
Influent [mg/L] 35,478 32,088 18,343
Effluent [mg/L] 9,808 4,482 3,532
Removal Efficiency 67% 84% 80%
pH Alkalinity
[mg/L]
Temperature(0C)
Dissolved COD
(% of Total)
VSS
(% of TSS)
Influent 6.0 986 28.9 10.5 54.6
Effluent 5.5 850 29.1 75.8 75.4
Probability Densities for Total COD
Reactor Influent Reactor Effluent
Total COD [10 3 mg/L]020406080100120
0.0
0.1
0.2
0.3
0.4
Observed
Predicted
Normal Distribution = 35477.9 mg/L = 18328.8 mg/Ln = 632 r = 0.98
Total COD [10 3 mg/L]
05101520
Re
lati
ve
Fre
qu
enc
y
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Observed
Predicted
Normal Distribution= 9808.2 mg/L= 4363.1 mg/Ln = 63r2 = 0.94
Re
lati
ve
Fre
qu
enc
y
Selected Performance Data from other Studies
WastewaterRaw
molassesMolasses
alcohol stillageSwine waste
Whisky distillery
Influent COD (g/l) 990 115.8 58.5 51
HRT (hours) 850 138-636 360 360
Reactor volume 150 150 15 6.3
Temperature (0C) 37 37 35 30
OLR (kg/m3.d) 28 4.3-20 4 2.2-3.46
COD removal (%) 50 70-88 62-69 >90
Biogas production
(v/v/d)>5 >2.3 2.9-3.2 1.2-3.6
Ref.Boopathy and Tilche, 1991
Boopathy and Tilche, 1992
Boopathy and Sievers, 1991
Boopathy et al., 1988
Gas Production
Total Gas Production = C * Q * (VSSIN – VSSEFF)Methane Production = 0.7 Total Gas Production
Where, Q = 500 gal/dayC = 12 to 18 ft3/lb (0.75 to 1.12 m3/kg), Metcalf & Eddy, 1991 70% of the gas is Methane
Average Gas Production = 28.6 m3/d
Average CH4 production = 0.7 * 28.6 = 20 m3/d
Ga
s (
m3/d
ay)
Time (day)
0 50 100 150 200 250 300 350
0
20
40
60
80
100
120516 mg/L 258 mg/L 0 mg/L
Conclusions
1. The anaerobic digester performed well at a relatively low HRT of 48 h without temperature control.
2. The removal efficiency for Total COD, TSS and VSS is 68.9%, 88.5% and 84.7% respectively.
3. The reactor showed great economical prospective for the natural gas production and low construction and operation cost.
Reactor in operation currently near Mobile, AL
Thank you !
QUESTIONS ?
Total COD, TSS, and VSS Profile at Sugar Effect
Influent
Effluent
Removal (%)
Time (day)0 50 100150200250300350
To
tal C
OD
[10
3 m
g/L
]
020406080
100120140
Re
mo
val (%)
0
20
40
60
80
100
120516 mg/L 258 mg/L0 mg/L
Time (day)
Re
mo
val (%)
0 50 100 150 200 250 300 350
TS
S [1
03 m
g/L
]
0
20
40
60
80
100
020406080100120
516 mg/L 258 mg/L0 mg/L
Time (day)0 50 100 150 200250 300 350
VS
S [1
03 m
g/L
]
0102030405060
Re
mo
val (%)
020406080100120
516 mg/L 258 mg/L0 mg/L
Hydraulic Characteristics Study (by Grobicki and Stuckey)
Method - A series of residence time distribution studies by tracking the fate of an inert tracer (Li+) in the effluent
Models - “Dispersion” and “Tanks In Series”
Results
• intermediate between plug-flow and ideally mixed
• Simulated as a series of perfectly-mixed compartments
Comparisons with Other Reactors
ABRAnaerobic
filterCSTRWithout
BiomassWith
Biomass
Dead
Space (%)< 8%
18%
(at 8gVSS/l)50-93% >80%
Ref.Grobicki and Stuckey,
1992 Yong and
Young, 1988 Stuckey,
1983
pH and Alkalinity Profile at Sugar Effect
Influent Effluent
Time (day)
pH
0 50 100 150 200 250 300 3500
2
4
6
8
10516 mg/L 258 mg/L 0 mg/L
Time (day)
50 100 150 200 250 300 350
Alk
alin
ity
0
500
1000
1500
2000
2500516 mg/L 258 mg/L 0 mg/L
Anaerobic Baffled Reactor (ABR)
ABR -- A reactor design, with a series of baffles to force a wastewater to flow under and over (or through) the baffles as it passes from the inlet to the outlet
Two significance of the specific configuration
o Two-phase system with low cost -- Acidogensis and the methanogensis partially separated
o High solids retention capacity, high bacteria activities (increase by a factor of up to four)
WastewaterHRT
(h)
COD
(mg/l) COD
removal (%)
OLR (kg/m3/d)
Gas
Produced
(v/v/d)
Ref.
IN EFF
Greywater 84 438 109 75 0.13 0.025Witthauer and Stuckey,
1982
Greywater 48 492 143 71 0.25 0.05Witthauer and Stuckey,
1982
Greywater 84 445 72 84 0.13 0.025Witthauer and Stuckey,
1982
Sucrose 6.8 473 74 74 1.67 0.49 Orozco, 1988
Sucrose 8 473 66 86 1.42 0.43 Orozco, 1988
Sucrose 11 441 33 93 0.96 0.31 Orozco, 1988
Slaugherhouse 26.4 730 80 89 0.67 0.72 Polprasert et al., 1992
Slaugherhouse 7.2 550 110 80 1.82 0.33 Polprasert et al., 1992
Slaugherhouse 2.5 510 130 75 4.73 0.43 Polprasert et al., 1992
Selected Low Strength Performance Data
Co-substrateInitiationWhen fed two different substrates with high strength, one readily biodegradable and the other refractory, the microbes would utilize the readily biodegradable substrate rapidly, followed by the refractory compound
Related Research ReviewAppropriate dose addition of a readily-degradable co-substrate improved the process performance
1. Pepton (Kobayashi et al., 1989) 2. Glucose (Satsangee and Ghosh, 1996)), 3. Glucose (Joo-Hwa Tay et al., 2001)
Sugar Effect at Digestion Performance
Sugar Concentration (mg/L)
516 (10%) 258 (5%) 0 (0%)
Influent Total COD [mg/L] 36192.2 35927.8 36423.6
Effluent Total COD [mg/L] 8904.4 14783.8 9492.0
Removal of Total COD (%) 68.9 56.6 73.6
Influent TSS [mg/L] 32638.0 33598.5 32020.0
Effluent TSS [mg/L] 2919.8 10207.3 4272.1
Removal of TSS (%) 88.5 68.1 86.5
Influent VSS [mg/L] 19088.3 18946.6 15934.6
Effluent VSS [mg/L] 2276.9 7406.2 2965.6
Removal of VSS (%) 84.7 60.2 81.0
New ChallengeChanges in quantity and quality
Due to - Increase of domestic and industrial activities
- Evolution of more efficient wastewater treatment plants
Public tolerance towards environmental pollutions
Land available for sludge disposal
Inherent limitation of current digesters (10-30 days
HRT)
High cost of advanced anaerobic reactors (i.e. FB)
More cost-efficient technologies are required
Historical Profile of Natural Gas Prices
Source: www.energyonline.com
Date (month)
Pri
ce (
do
llar
s/10
3ft
3)
0
2
4
6
8
10
12
Residential Prices
Commercial Prices Industrial Prices
1998 1999 2000 2001
4 84 8 12 12 4 8 12
Probability Densities for VSS
VSS [103 mg/L]
0510152025303540455055
Re
lati
ve
Fre
qu
enc
y
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Observed
Predicted
Reactor Influent
Normal Distribution
= 18343.2 mg/L= 10104.5 mg/Ln = 56
r2 = 0.97
VSS [103 mg/L]
024681012141618
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Observed
Predicted
Reactor Effluent
Lognormal Distribution
= 3319.1 mg/L = 3532.3 mg/Ln = 56
r 2 = 0.97
Re
lati
ve
Fre
qu
enc
y
Reactor Influent Reactor Effluent
TSS [10 3 mg/L]
0102030405060708090
Re
lati
ve
Fre
qu
enc
y
0.0
0.1
0.2
0.3
0.4
Observed
Predicted
Normal Distribution= 32088.5 mg/L = 18145.1 mg/Ln = 56r2
= 0.93
TSS [10 3 mg/L]
0510152025
Re
lati
ve
Fre
qu
enc
y
0.0
0.1
0.2
0.3
0.4
0.5
0.6
Observed
Predicted
Lognormal Distribution
= 4482.4 mg/L = 5091.4 mg/Ln = 562
r = 0.96
Probability Densities for TSS
Resilience to Organic Loading and Temperature Shocks
Time (d)0 50 100 150 200 250 300T
otal
CO
D [
103 m
g/L
]
020406080
100120140 R
emoval E
fficiency %
0
20
40
6080
100
TS
S [
103 m
g/L
]
Rem
oval Efficiency %
Time (d)0 50 100 150 200 250 300
0
20
40
60
80
100
0
20
40
60
80
100
Influent Effluent % Removal Efficiency
Time (d)0 50 100 150 200 250 300
0102030405060
0
20
4060
80
100
VS
S [
103 m
g/L
]
Rem
oval Efficiency %
Time (d)0 50 100 150 200 250 300
0
10
20
30
40
Influent
Effluent
Air Temperature
Tem
pera
ture
(0 C
)