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Shock loading management with the sequencing batch biofilm reactor technology
8)
Pergamon
Wal. St:i. T~ch. Vol. H. No... pp. 3~-40. 1997. Copyrighl C 1996 IAWQ. Published by Elsevier ScIence LId Printed ,n areal Brilain. All right. reserved.
PH: S0273-1223(96)00876-1
0273-1223197 S\7'OO + 0-00
SHOCK LOADING MANAGEMENT WITH THE SEQUENCING BATCH BIOFILM
REACTOR TECHNOLOGY
Hans-Peter Kaballo ROEDIGER Anlagenbau GmbH, Kinzigheimer Weg 104·106, D-63450 Hanau. Germany
ABSTRACT This paper presents one performance of SBBRs to treat wastewater containing the priority organic' pollutant para-chlorophenol (p-CP). Batch kinetic studies showed that the bIOlOgical degradation ofp• CP can be described with the model of the substrate inhibition analogue Haldane. The following pa• rameters were found: K, = 4.4 mg L-I, Ki = 60 mg L-I, rll)8X = 3.24 h-l . With this information the opera• tion mode of a sequencmg batch biofilm reactor was optimized when shock loading appeared. During a short fill of 12 minutes approximately 30 % of the influent amount was eliminated of the bulk. It is as• sumed that other effects than biodegradation were responsible for this, i.e. biosorption. During the reac• tion phase the turbulence had an important influence to the elimination rate. At a bulk fluid concentra• tion of more than 60 mg L-1 the elimination process was controlled by microbial kinetics. But with de• creasing concentration the mass transfer became more important. The elimination rate could be in• creased from 7.3 mg L h- I to 26.3 mg L h- I with a S-fold higher air flow rate. Copyright © 19961AWQ. Published by Elsevier Science Ltd KEYWORDS sequencing batch biofilm reactor (SBBR), batch kinetic study, para-chlorophenol, biofilm kinetics, biological degradation, mass transfer, shock loading, process strategy optimization. INTRODUCTION Biofilm reactors become more and more important in the field of wastewater treatment. The ad• vantages ofbiofilm reactor systems in comparison to activated sludge systems include: higher volumet• ric load., increased process stability, and compactness ofthe reactors, caused by higher biomass concen• tration in the reactors and higher specific removal rates. Furthermore, slow growing organisms can be accumulated easier in biofilm reactors because sludge age is independent of the mean residence time of tile fluid. Restrictions ofbiofilm reactor systems are mass transfer limitations for oxygen and substrates and clogging of the packing caused by excessive growth of biomass in the inflow section ofthe reactor. One way to avoid these disadvantages is the operation ofbiofilm reactors in a fill and draw mode which is catted "Sequencing Batch Biofilm Reactor (SBBR)" technology. Para-chlorophenol was chosen as a model compound for xenobiotics because of its widespread use (Rippen, 1991). The few data about kinetic models and kinetic parameters of its biological degrada• tion found in literature (Saez and Rittmann, 1991; Tabak et aI., 1992) did not give an exact inform:ltion about the kinetics of the microbial degradation process. Therefore our own kinetic s.wdies were con• ducted first to commit the operation conditions in the SBBR. 35 oMTJ5-I.(
H.-P. KABALLO
36
DESCRIPTION OF THE REACTOR SYSTEMS USED Batch kinetic studies were conducted in a tubular reactor system. For the full. description see Kaballo and Wilderer (1995). Technical data ofthe system are listed in table I. Technical data of the SBBR pilot-plant are listed in table II. For the full description see KabaUo et al. (1995). TABLE I: TECHNICAL DATA OF THE TUBULAR BATCH REACTOR parameter fixed bed height inner diameter fixed bed volume gap grade total liquid volume in system packing
dimension [em] [em] [m L] [-] [L]
aeration
value 10
10.7 900 0.29 2 expanded clay balls bubble aeration with pure oxygen or nitrogen
TABLE II: TECHNICAL OATA OF THE PILOT-PLANT parameter fixed bed height inner diameter exchanging volume per cycle packing • specific area • total packing surface per reactor airflow fiU duration 1. recirculation react duration 2. recirculation draw duration
dimension [em] [em] [L] [m2m-3] [m 2] [L h-I]
[min] [min] [min] [min] [min]
value 600 21.3 80 expanded clay bans 212 45
1 - 250 (variable) 12 15 183 - 360 15 15
WASTE WATER CHARACTERISTICS Effluent ofthe municipal wastewater treatment plant of the town Garching, Germany was used for the solution of para-chlorophenol (p-CP). For further information see Kaballo and Wilderer (1995).
RESULTS The reactor for batch kinetic studies was inoculated with activated sludge from the municipal wastewater treatment plant of Garching, Germany. To avoid an influence of mass transfer the recircula• tion rate was performed maximum possible (3.6 L min-I) which corresponds with a particle Reynolds number ofRep=228. Batch kinetic studies were realized by increasing the initial concentration up to 160 mg L-I and measuring the amount of p-CP eliminated with time.
Shock loading management
37
deeradation rate (m&!(eSS,h)1 2,S
-r----------------., •
2
-
experiment calculated
1,5
0,5 O-l-~~-.....-~~~
0,00
SO,OO
.......
~-~.._.~
100,00
150,00
_ _..........l 200,00
cone. [mell]
Fig. l. Specific p-CP elimination rate as a function of the p-ep concentration (K. = 4,4 mg L'\; K. - 60 mg L·I; rmax = 3.24 h· I, T - 291K, ox. cone. = 10 mg L·I;S=O,8874) Elimination rates were plotted over the p-CP concentration (see figure I). Oxygen concentration was kept constant on a level of 10 mg L-I dunng the whole experiment. Using the Haldane-Kinetic for substrate inhibition the followin, values were used to calculate the compensation curve: Ks = 4,4 mg V' Kj = 60 mg L·I, rmax = 3.24 h- .It is important that the elimination process is inhibited by increasing substrate concentrations. High p-CP concentrations led to a reduced elimination rate, whereas concen• trations in a range of IS to 30 mg L-I led to the maximum elimination rate. The influence of mass transfer on the elimination rate was studied in the pilot plant (SBBR). The reactor was operated with the effluent of the municipal wastewater treatment plant ofthe town Garching, to which 40 mg L·I p-CP was added. The cycle duration was 4 h and the exchanging volume 80 L. The air flow was 50 L h- . The biomass concentration was 3 g kg'\ SS per P.j1cking, respectively 7,3 g m-2 SS. Thus, the reactor was operated with a p-CP load of 0.12 mg g··SS h' ,respectively 0.9 mg m·2 packing. The sharpest substrate elimination occurred in the fill phase (with a duration of 12 min• utes). During this time approximately 32 % of the input was eliminated from the bulk. The entire elimi• nated mass was 970 mgm 12 minutes which corresponds to an elimination rate of4850 mgh- I; whereas the elimination rate during the subsequent recirculation and reaction phases was only 1310 mg hoi. A similar effect was observed when the reactor was operated with a 3-fold higher influent con• centration. 3 experiments were performed each with different air flow rate (see figure 2); 50 Lh- I, 100 Lh-' 250 Lh- I. Figure 2 shows the concentration profiles over the fixed bed height in the SBBR after fill and recirculation phase. In each experiment approximately 25 % ofthe influent p-CP was eliminated during fill. The ehminated mass was 2250 mg m 12 minutes which corresponds to an elimination rate of 11250 mg h-I. During the recirculation the elimination continued; but its rate decreased. Another 1300 mg were eliminated during the IS minutes ofrecirculation. Elimination kinetics were not affected by different air flow rates. After fill and recirculation the influent concentration of approximately 110 mg L-I was reduced to 70 mg L-I. After recirculation was completed, the elimination was observed at different air flow rates. In par• allel, oxygen concentration was measured. There was no difference ofthe oxygen concentration be• tween the 3 experiments. It stayed constant during the reaction phase in each experiment on ap• proximately 9.S mg L-I. With increasing time there were significant differences in the p-CP elimination rate. In figure 3, the p-CP concentration during reaction is shown.
38
H.-P. KABALLO
Two different parts of the reaction phase can be distinguished. The first is during the first 60 to 100 minutes; In this phase, there was no difference in the elimination rate in the three experiments. The concentrations run parallel. But with increasing time and decreasing concentration the curves differ. In the experiment with the highest volumetric flow rate of250 L h-I, the elimination rate was highest too; with the lowest flow rate of SO L h- I , the elimination rate was lowest. In table III a summary of the ob• served elimination rates is given. p-CP cone. [m gil) 120
-r---------------------, after fill:
100
- - - v=50 IIh
80
- - - v= I 00 I/h - - v=250 IIh
after recirc!.:
40 20
o +o
.-.-....-. 100
200
....-._ 400
300
....-. 500
~
v=501/h
-0--
v=IOO I/h
~
v=2501/h
~
600
fiud bed height [em)
Fig. 2. p-CP concentration profiles after fill (filled marks) and after recirculation (opened marks) in the
SBBR
p-CP cone. [mg/l)
80,00
r----------------,
70,00 60,00 50,00
r==-~50~-l
.•
30,00
20,00 10,00 0,00
1--I
40,00
••
l--
o
!
IL - v=250 Vb JI
-_--_---l
..Aoi.......
100
,
v=100Vb
200
300
400
elapsed time [min) Fig. 3. Decrease of the p-CP concentration at three different air flow rates
Shock loading management
Because there was no difference in oxygen concentration and because stripping losses were ne• glected, the only reason for the strong difference could be the increasing mass transfer of p-CP into the biofilm with increasing flow rate. TABLE III: OBSERVED ELIMINATION RATES AT DIFFERENT AIR FLOW RATES expo with 50 Lh- I expo with 100 Lb-I expo with 250 Lh- I 1st phase 2nd phase 1st phase 2nd phase 1st phase 2nd phase 2 I 2 I I 2 I 2 2 I [mgm- h- ] [mgm- h- ] [mg m- h- ] [mg m- h- ] [mg m- h- ] [mg m-2h-i] 12.7 13.0 15.2 43.6 14.4 46.8 DISCUSSION In a SBBR the elimination rate ofp-CP is strongly affected by the interaction of biological kinetics and external mass transport. This in mind, a successful strategy to improve the reactor capacity while shock loadings appear could be the following: •
Ist step: reducing the initial concentration to a level of about 60 mg Vi due to mixing highly polluted in• fluent with already treated waste water from the cycle before and
•
2nd step: increasmg the elimination rate by increasing the mass transfer enhancing parameters. Step 2 reduces the necessary retention time.
Because batch kinetic studies showed the great influence of oxygen concentration on the elimina• tion rate the increase of air flow rates was chosen to increase mass transfer. Because both, increasing turbulence and supplying sufficient oxygen can be done in the same way. It must be attended, that the initial concentration should be below the inhibition threshold level. In the experiments the initial concentration was influenced by elimination processes during fill, which seems to be no biological degradation. It is assumed that biosorption plays an important role. Further experiments have to be done to study this effect.
CONCLUSIONS Batch tests showed that high p-CP concentrations inhibit the degradation. This leads to a kineti• cally controlled elimination process in the beginning ofthe reaction phase when high concentrations of p-CP inflow. An increase in the turbulence in order to increase mass transfer of p-CP into the biofilm does not result in higher p-CP elimination rates and is not necessary. On account ofthe limited kinetics p-CP is eliminated from the bulk with slow rates only. When the concentration reaches about 60 mg L-I or less, the elimination process runs faster and reaches its maximum at approximately 15 to 30 mg L-I. In this phase the elimination process is strongly infl.uenced by m~ss transfer mechanisms. Increasing the mass transfer enhancing parameters, the elimi• nation rate also mcreases. The knowledge about this interaction leads to an optimized operation mode of SBBRs.
39
40
H.-P. KABALLO
ACKNOWLEDGEMENT The present work was kindly supported by the Gennan national science foundation DFG- Deut• sche Forschungsgemeinschaft (Urant Wi 620/6-1 and Grant Wi 620/6-2). I thank Peter A. Wilderer and his institute for the possibility ofthis work. REFERENCES Haggblom, M. (1990) Mechanisms of bacterial degradation and transfonnation of chlorinated monoaromatic compounds. Journal of Basic Microbiology, No. 30,115-141 Kahallo, H.·P.; Zhao, Y.; Wilderer, PA (1995) Elimination ofp-chlorophenol in biofilm reactors· a comparative study ofcontinuous flow and sequenced batch operation. Water Science and Technology Vo1.31.No. 1,51-60 Kaballo, H-P. and Wilderer, PA (1995): The Sequencing Batch Biofilm Reactor Technology- A New and Advanced Method to Treat Industrial Wastewater, speech at the W.E.F. Conference "New and Emerging Technologies and Products, Toronto, June, 4-7. Knackrnuss, H.-J. and Hellweg, M. (1978) Utilization and cooxidation of chlorinated phenols by pseu• domonas sp. B13. Arch. Microbiol. No. 117, 1-7 Rippen, G. (1991) Handbuch Umweltchemikalien Saez, P.B. and Rittmann, B.E. (1991) Biodegradation kinetics of 4-chlorophenol, an inhibitory co• metabolite. Research Journal WPCF. Vol. 63. No.6, 838-847 Tabak, H. H.; Gao, c.; Desai, S. Govind, R. (1992) Development of predictive structure-biodegradation relationship models with the use of respirometrically generated biokinetic data. Water Science and Technology. Vol. 26. No. 3-4, 763-772 Wittich, R.M. (1991) MOglichkeiten des biologischen Abbaus halogenaromatischer Verbindungen. Schriftenreihe Biologische Abwasserreinigung No.1: Biologischer Abbau von Chlorkohlenwasserstof• fen, TU Berlin, Systemdruck GmbH, Berlin, 59-78
Pergamon
Wal. St:i. T~ch. Vol. H. No... pp. 3~-40. 1997. Copyrighl C 1996 IAWQ. Published by Elsevier ScIence LId Printed ,n areal Brilain. All right. reserved.
PH: S0273-1223(96)00876-1
0273-1223197 S\7'OO + 0-00
SHOCK LOADING MANAGEMENT WITH THE SEQUENCING BATCH BIOFILM
REACTOR TECHNOLOGY
Hans-Peter Kaballo ROEDIGER Anlagenbau GmbH, Kinzigheimer Weg 104·106, D-63450 Hanau. Germany
ABSTRACT This paper presents one performance of SBBRs to treat wastewater containing the priority organic' pollutant para-chlorophenol (p-CP). Batch kinetic studies showed that the bIOlOgical degradation ofp• CP can be described with the model of the substrate inhibition analogue Haldane. The following pa• rameters were found: K, = 4.4 mg L-I, Ki = 60 mg L-I, rll)8X = 3.24 h-l . With this information the opera• tion mode of a sequencmg batch biofilm reactor was optimized when shock loading appeared. During a short fill of 12 minutes approximately 30 % of the influent amount was eliminated of the bulk. It is as• sumed that other effects than biodegradation were responsible for this, i.e. biosorption. During the reac• tion phase the turbulence had an important influence to the elimination rate. At a bulk fluid concentra• tion of more than 60 mg L-1 the elimination process was controlled by microbial kinetics. But with de• creasing concentration the mass transfer became more important. The elimination rate could be in• creased from 7.3 mg L h- I to 26.3 mg L h- I with a S-fold higher air flow rate. Copyright © 19961AWQ. Published by Elsevier Science Ltd KEYWORDS sequencing batch biofilm reactor (SBBR), batch kinetic study, para-chlorophenol, biofilm kinetics, biological degradation, mass transfer, shock loading, process strategy optimization. INTRODUCTION Biofilm reactors become more and more important in the field of wastewater treatment. The ad• vantages ofbiofilm reactor systems in comparison to activated sludge systems include: higher volumet• ric load., increased process stability, and compactness ofthe reactors, caused by higher biomass concen• tration in the reactors and higher specific removal rates. Furthermore, slow growing organisms can be accumulated easier in biofilm reactors because sludge age is independent of the mean residence time of tile fluid. Restrictions ofbiofilm reactor systems are mass transfer limitations for oxygen and substrates and clogging of the packing caused by excessive growth of biomass in the inflow section ofthe reactor. One way to avoid these disadvantages is the operation ofbiofilm reactors in a fill and draw mode which is catted "Sequencing Batch Biofilm Reactor (SBBR)" technology. Para-chlorophenol was chosen as a model compound for xenobiotics because of its widespread use (Rippen, 1991). The few data about kinetic models and kinetic parameters of its biological degrada• tion found in literature (Saez and Rittmann, 1991; Tabak et aI., 1992) did not give an exact inform:ltion about the kinetics of the microbial degradation process. Therefore our own kinetic s.wdies were con• ducted first to commit the operation conditions in the SBBR. 35 oMTJ5-I.(
H.-P. KABALLO
36
DESCRIPTION OF THE REACTOR SYSTEMS USED Batch kinetic studies were conducted in a tubular reactor system. For the full. description see Kaballo and Wilderer (1995). Technical data ofthe system are listed in table I. Technical data of the SBBR pilot-plant are listed in table II. For the full description see KabaUo et al. (1995). TABLE I: TECHNICAL DATA OF THE TUBULAR BATCH REACTOR parameter fixed bed height inner diameter fixed bed volume gap grade total liquid volume in system packing
dimension [em] [em] [m L] [-] [L]
aeration
value 10
10.7 900 0.29 2 expanded clay balls bubble aeration with pure oxygen or nitrogen
TABLE II: TECHNICAL OATA OF THE PILOT-PLANT parameter fixed bed height inner diameter exchanging volume per cycle packing • specific area • total packing surface per reactor airflow fiU duration 1. recirculation react duration 2. recirculation draw duration
dimension [em] [em] [L] [m2m-3] [m 2] [L h-I]
[min] [min] [min] [min] [min]
value 600 21.3 80 expanded clay bans 212 45
1 - 250 (variable) 12 15 183 - 360 15 15
WASTE WATER CHARACTERISTICS Effluent ofthe municipal wastewater treatment plant of the town Garching, Germany was used for the solution of para-chlorophenol (p-CP). For further information see Kaballo and Wilderer (1995).
RESULTS The reactor for batch kinetic studies was inoculated with activated sludge from the municipal wastewater treatment plant of Garching, Germany. To avoid an influence of mass transfer the recircula• tion rate was performed maximum possible (3.6 L min-I) which corresponds with a particle Reynolds number ofRep=228. Batch kinetic studies were realized by increasing the initial concentration up to 160 mg L-I and measuring the amount of p-CP eliminated with time.
Shock loading management
37
deeradation rate (m&!(eSS,h)1 2,S
-r----------------., •
2
-
experiment calculated
1,5
0,5 O-l-~~-.....-~~~
0,00
SO,OO
.......
~-~.._.~
100,00
150,00
_ _..........l 200,00
cone. [mell]
Fig. l. Specific p-CP elimination rate as a function of the p-ep concentration (K. = 4,4 mg L'\; K. - 60 mg L·I; rmax = 3.24 h· I, T - 291K, ox. cone. = 10 mg L·I;S=O,8874) Elimination rates were plotted over the p-CP concentration (see figure I). Oxygen concentration was kept constant on a level of 10 mg L-I dunng the whole experiment. Using the Haldane-Kinetic for substrate inhibition the followin, values were used to calculate the compensation curve: Ks = 4,4 mg V' Kj = 60 mg L·I, rmax = 3.24 h- .It is important that the elimination process is inhibited by increasing substrate concentrations. High p-CP concentrations led to a reduced elimination rate, whereas concen• trations in a range of IS to 30 mg L-I led to the maximum elimination rate. The influence of mass transfer on the elimination rate was studied in the pilot plant (SBBR). The reactor was operated with the effluent of the municipal wastewater treatment plant ofthe town Garching, to which 40 mg L·I p-CP was added. The cycle duration was 4 h and the exchanging volume 80 L. The air flow was 50 L h- . The biomass concentration was 3 g kg'\ SS per P.j1cking, respectively 7,3 g m-2 SS. Thus, the reactor was operated with a p-CP load of 0.12 mg g··SS h' ,respectively 0.9 mg m·2 packing. The sharpest substrate elimination occurred in the fill phase (with a duration of 12 min• utes). During this time approximately 32 % of the input was eliminated from the bulk. The entire elimi• nated mass was 970 mgm 12 minutes which corresponds to an elimination rate of4850 mgh- I; whereas the elimination rate during the subsequent recirculation and reaction phases was only 1310 mg hoi. A similar effect was observed when the reactor was operated with a 3-fold higher influent con• centration. 3 experiments were performed each with different air flow rate (see figure 2); 50 Lh- I, 100 Lh-' 250 Lh- I. Figure 2 shows the concentration profiles over the fixed bed height in the SBBR after fill and recirculation phase. In each experiment approximately 25 % ofthe influent p-CP was eliminated during fill. The ehminated mass was 2250 mg m 12 minutes which corresponds to an elimination rate of 11250 mg h-I. During the recirculation the elimination continued; but its rate decreased. Another 1300 mg were eliminated during the IS minutes ofrecirculation. Elimination kinetics were not affected by different air flow rates. After fill and recirculation the influent concentration of approximately 110 mg L-I was reduced to 70 mg L-I. After recirculation was completed, the elimination was observed at different air flow rates. In par• allel, oxygen concentration was measured. There was no difference ofthe oxygen concentration be• tween the 3 experiments. It stayed constant during the reaction phase in each experiment on ap• proximately 9.S mg L-I. With increasing time there were significant differences in the p-CP elimination rate. In figure 3, the p-CP concentration during reaction is shown.
38
H.-P. KABALLO
Two different parts of the reaction phase can be distinguished. The first is during the first 60 to 100 minutes; In this phase, there was no difference in the elimination rate in the three experiments. The concentrations run parallel. But with increasing time and decreasing concentration the curves differ. In the experiment with the highest volumetric flow rate of250 L h-I, the elimination rate was highest too; with the lowest flow rate of SO L h- I , the elimination rate was lowest. In table III a summary of the ob• served elimination rates is given. p-CP cone. [m gil) 120
-r---------------------, after fill:
100
- - - v=50 IIh
80
- - - v= I 00 I/h - - v=250 IIh
after recirc!.:
40 20
o +o
.-.-....-. 100
200
....-._ 400
300
....-. 500
~
v=501/h
-0--
v=IOO I/h
~
v=2501/h
~
600
fiud bed height [em)
Fig. 2. p-CP concentration profiles after fill (filled marks) and after recirculation (opened marks) in the
SBBR
p-CP cone. [mg/l)
80,00
r----------------,
70,00 60,00 50,00
r==-~50~-l
.•
30,00
20,00 10,00 0,00
1--I
40,00
••
l--
o
!
IL - v=250 Vb JI
-_--_---l
..Aoi.......
100
,
v=100Vb
200
300
400
elapsed time [min) Fig. 3. Decrease of the p-CP concentration at three different air flow rates
Shock loading management
Because there was no difference in oxygen concentration and because stripping losses were ne• glected, the only reason for the strong difference could be the increasing mass transfer of p-CP into the biofilm with increasing flow rate. TABLE III: OBSERVED ELIMINATION RATES AT DIFFERENT AIR FLOW RATES expo with 50 Lh- I expo with 100 Lb-I expo with 250 Lh- I 1st phase 2nd phase 1st phase 2nd phase 1st phase 2nd phase 2 I 2 I I 2 I 2 2 I [mgm- h- ] [mgm- h- ] [mg m- h- ] [mg m- h- ] [mg m- h- ] [mg m-2h-i] 12.7 13.0 15.2 43.6 14.4 46.8 DISCUSSION In a SBBR the elimination rate ofp-CP is strongly affected by the interaction of biological kinetics and external mass transport. This in mind, a successful strategy to improve the reactor capacity while shock loadings appear could be the following: •
Ist step: reducing the initial concentration to a level of about 60 mg Vi due to mixing highly polluted in• fluent with already treated waste water from the cycle before and
•
2nd step: increasmg the elimination rate by increasing the mass transfer enhancing parameters. Step 2 reduces the necessary retention time.
Because batch kinetic studies showed the great influence of oxygen concentration on the elimina• tion rate the increase of air flow rates was chosen to increase mass transfer. Because both, increasing turbulence and supplying sufficient oxygen can be done in the same way. It must be attended, that the initial concentration should be below the inhibition threshold level. In the experiments the initial concentration was influenced by elimination processes during fill, which seems to be no biological degradation. It is assumed that biosorption plays an important role. Further experiments have to be done to study this effect.
CONCLUSIONS Batch tests showed that high p-CP concentrations inhibit the degradation. This leads to a kineti• cally controlled elimination process in the beginning ofthe reaction phase when high concentrations of p-CP inflow. An increase in the turbulence in order to increase mass transfer of p-CP into the biofilm does not result in higher p-CP elimination rates and is not necessary. On account ofthe limited kinetics p-CP is eliminated from the bulk with slow rates only. When the concentration reaches about 60 mg L-I or less, the elimination process runs faster and reaches its maximum at approximately 15 to 30 mg L-I. In this phase the elimination process is strongly infl.uenced by m~ss transfer mechanisms. Increasing the mass transfer enhancing parameters, the elimi• nation rate also mcreases. The knowledge about this interaction leads to an optimized operation mode of SBBRs.
39
40
H.-P. KABALLO
ACKNOWLEDGEMENT The present work was kindly supported by the Gennan national science foundation DFG- Deut• sche Forschungsgemeinschaft (Urant Wi 620/6-1 and Grant Wi 620/6-2). I thank Peter A. Wilderer and his institute for the possibility ofthis work. REFERENCES Haggblom, M. (1990) Mechanisms of bacterial degradation and transfonnation of chlorinated monoaromatic compounds. Journal of Basic Microbiology, No. 30,115-141 Kahallo, H.·P.; Zhao, Y.; Wilderer, PA (1995) Elimination ofp-chlorophenol in biofilm reactors· a comparative study ofcontinuous flow and sequenced batch operation. Water Science and Technology Vo1.31.No. 1,51-60 Kaballo, H-P. and Wilderer, PA (1995): The Sequencing Batch Biofilm Reactor Technology- A New and Advanced Method to Treat Industrial Wastewater, speech at the W.E.F. Conference "New and Emerging Technologies and Products, Toronto, June, 4-7. Knackrnuss, H.-J. and Hellweg, M. (1978) Utilization and cooxidation of chlorinated phenols by pseu• domonas sp. B13. Arch. Microbiol. No. 117, 1-7 Rippen, G. (1991) Handbuch Umweltchemikalien Saez, P.B. and Rittmann, B.E. (1991) Biodegradation kinetics of 4-chlorophenol, an inhibitory co• metabolite. Research Journal WPCF. Vol. 63. No.6, 838-847 Tabak, H. H.; Gao, c.; Desai, S. Govind, R. (1992) Development of predictive structure-biodegradation relationship models with the use of respirometrically generated biokinetic data. Water Science and Technology. Vol. 26. No. 3-4, 763-772 Wittich, R.M. (1991) MOglichkeiten des biologischen Abbaus halogenaromatischer Verbindungen. Schriftenreihe Biologische Abwasserreinigung No.1: Biologischer Abbau von Chlorkohlenwasserstof• fen, TU Berlin, Systemdruck GmbH, Berlin, 59-78