Behavior of Trickle Bed Air Behavior of Trickle Bed Air Biofilter Biofilter for for VOCs VOCs Removal Removal : Effect of Non : Effect of Non - - Use Periods Use Periods Daekeun Daekeun Kim, Kim, Zhangli Zhangli Cai Cai , , George A George A Sorial Sorial Department of Civil and Environmental Engineering, Department of Civil and Environmental Engineering, University of Cincinnati University of Cincinnati AlChE 2004 Spring National Meeting, April 28, 2004
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Behavior of Trickle Bed Air Behavior of Trickle Bed Air BiofilterBiofilter for for VOCsVOCs RemovalRemoval: Effect of Non: Effect of Non--Use PeriodsUse Periods
DaekeunDaekeun Kim,Kim,ZhangliZhangli CaiCai,,
George A George A SorialSorial
Department of Civil and Environmental Engineering, Department of Civil and Environmental Engineering, University of CincinnatiUniversity of Cincinnati
AlChE 2004 Spring National Meeting, April 28, 2004
• Unfavorable performance due to shock load & load fluctuation
→ A purpose of the next study
Objective
• The main objective of this research is to investigate the performance of a TBAB under periodic stressed operating conditions (backwashing & non-use periods) as a function of toluene loading.
To evaluate the effect of non-use periods (starvation & stagnant) on the performance of a TBAB for long-term operation.
To compare TBAB operated under non-use periods against backwashing strategy.
Experimental Methods
• Target VOC: Toluene
• Reactor: independent lab-scale TBAB
• Media: pelletized biological support media
Schematic diagram
Effluent Water
AirN2 + O2
VOCsParticulatesWaterCO2
S
S
S
S
S
S
S Sampling Location
VOCs
Effluent Air
7
3
1
4
2
5
6
8
1. Electronic Air Cleaner2. Mass Flow Controller3. Syringe Pump4. Nutrient Feed Control System5. Nutrient Feed Tank6. Spray Nozzle7. Trickle Bed Biofilter8. Pelletized Media
• At 0.7 and 1.41 kg COD/m3⋅day, TBAB provided the + 99 % removal efficiency for all strategies.
• For non-use periods at 3.52 kg COD/m3⋅day, the removal efficiency dropped below 90 %.
→ demanding Backwashing as biomass control
• An increase in loading rate needs much longer acclimation period.
Result 1 (cont’d)
Result 2. Reacclimation
• Reacclimation periods to reach at 99 % removal efficiency
– After backwashing and – After restart-up following the shut down for non-use periods.
Result 2: Reacclimation
Stagnant
Time, min
0 100 200 300 400 500 600 700
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
Backwashing
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
0.70 kg COD/m3day
1.41 kg COD/m3day
3.52 kg COD/m3day
Starvation
Time, min
0 100 200 300 400 500 600 700
Result 2 (cont’d)
Stagnant
Time, min
0 100 200 300 400 500 600 700
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
Backwashing
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
0.70 kg COD/m3day
1.41 kg COD/m3day
3.52 kg COD/m3day
Starvation
Time, min
0 100 200 300 400 500 600 700
Summary 2Summary 2--1.1. An increase in loading rate delayed reacclimation.
Result 2 (cont’d)
Stagnant
Time, min
0 100 200 300 400 500 600 700
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
Backwashing
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
0.70 kg COD/m3day
1.41 kg COD/m3day
3.52 kg COD/m3day
Starvation
Time, min
0 100 200 300 400 500 600 700
Summary 2-2. For backwashing strategy, much longer reacclimationperiod was required.→ due to the loss of active biomass by conducting backwashing
Result 2 (cont’d)
Stagnant
Time, min
0 100 200 300 400 500 600 700
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
Backwashing
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
0.70 kg COD/m3day
1.41 kg COD/m3day
3.52 kg COD/m3day
Starvation
Time, min
0 100 200 300 400 500 600 700
Summary 2-3. For non-use period strategies, the biofilter response is different from that after backwashing.→ the biomass played an important role in the reacclimation
Result 2 (cont’d)
Stagnant
Time, min
0 100 200 300 400 500 600 700
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
Backwashing
Rem
ova
l Eff
icie
ncy
, %
0
20
40
60
80
100
0.70 kg COD/m3day
1.41 kg COD/m3day
3.52 kg COD/m3day
Starvation
Time, min
0 100 200 300 400 500 600 700
Summary 2- 4. At high loading rate for non-use periods, → initially, a likely breakthrough was observed→ due to VOC adsorption on the biomass
Result 2 (cont’d)
Result 3. Kinetic analysis
• Kinetic analysis for VOC removal
Based on a pseudo first order reaction rate as a function of depth in the biofilter
Result 3. Kinetic analysis
COD loading, kg COD/m3day
0 1 2 3 4 5 6 7
Rea
ctio
n ra
te, s
ec-1
0.00
0.02
0.04
0.06
0.08
0.10
0.12
BackwashingStarvationStagnant
II (0.7)
III (1.41)
IV (3.52)
V (7.03)
* Loading rate(Kg COD/m3day)
Result 3 (cont’d)
Summary 3-1. An increase in loading rate decreased reaction rates.
COD loading, kg COD/m3day
0 1 2 3 4 5 6 7
Rea
ctio
n ra
te, s
ec-1
0.00
0.02
0.04
0.06
0.08
0.10
0.12
BackwashingStarvationStagnant
II (0.7)
III (1.41)
IV (3.52)
V (7.03)
* Loading rate(Kg COD/m3day)
Result 3 (cont’d)
Summary 3-2. For low loading rate (0.7 and 1.41 kg COD/m3day), non-use period strategies showed high reaction rates→ might be due to availability of active biomass
COD loading, kg COD/m3day
0 1 2 3 4 5 6 7
Rea
ctio
n ra
te, s
ec-1
0.00
0.02
0.04
0.06
0.08
0.10
0.12
BackwashingStarvationStagnant
II (0.7)
III (1.41)
IV (3.52)
V (7.03)
* Loading rate(Kg COD/m3day)
Result 3 (cont’d)
COD loading, kg COD/m3day
0 1 2 3 4 5 6 7
Rea
ctio
n ra
te, s
ec-1
0.00
0.02
0.04
0.06
0.08
0.10
0.12
BackwashingStarvationStagnant
Summary 3-3. For 3.52 kg COD/m3day, non-use period strategies showed low reaction rates→ might be due to high accumulation of the biomass
II (0.7)
III (1.41)
IV (3.52)
V (7.03)
* Loading rate(Kg COD/m3day)
Result 3 (cont’d)
ConclusionConclusion
• High performance of TBAB was observed for all experimental strategies up to 3.52 kg COD/m3day (250 ppmv).
• However, during the reacclimation periods following backwashing and non-use period, the TBAB unit can not comply with emission regulations.
→ the limitation of current TBAB system demands
novel novel VOCsVOCs control technologycontrol technology
Future WorksFuture Works
• IssueNeed to decrease reacclimation periodsNeed to mitigate shock load & load fluctuations
• GoalYield consistently high VOC removal efficiency
• ProposalEmploy a preliminary unit as a buffer
Future Works (contFuture Works (cont’’d)d)
Preliminary unit: Pressure swing adsorption (PSA) unitOperated under long term adsorption/desorption cycles
VOC
Consist loadVOC
Future Works (contFuture Works (cont’’d)d)
Combined Treatment : PSA + TBAB
→ Long term, high performance for VOC removal
Clean Air
Nutrient
VOC
Consist loadVOC
Functions
During backwashingfor biofilter unit
→ PSA: a sole unit of purification
During reacclimation period for biofilter unit
→ PSA: a buffer unit
Acknowledgements
• National Science Foundation (BES-0229135)
• Dr. George A. Sorial
• Colleagues at Environmental Chemistry Laboratory at University of Cincinnati.
Behavior of Trickle Bed Air Behavior of Trickle Bed Air BiofilterBiofilter for for VOCsVOCs Removal: Removal: Effect of NonEffect of Non--Use PeriodsUse Periods
DaekeunDaekeun KimKim
Department of Civil and Environmental EngineeringDepartment of Civil and Environmental EngineeringUniversity of CincinnatiUniversity of Cincinnati