Lab Report 7

1.0 ABSTRACT

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature. This experiment is conducted by using a bioreactor and the result is taken every 5 seconds until the value constant or close to 100 which indicates the concentration of oxygen in the bioreactor is saturated. The method used in this study in determining the k La value is dynamic gassing out method. Nitrogen gas is purged into the system until the value of oxygen becomes 0%. The calibration is done by making sure the t he bioreactor’s monitor stop blinking to indicate the calibration is done correctly even though the value becomes negative. If the value is negative, the value is adjusted manually until the value is 0. The nitrogen valve is closed when reaching 0 and the nitrogen wire is disconnected from the bioreactor. The bioreactor is aerated with air for 100%. The reading is taken for every 5 seconds until the increasing DO % reaching three stable values. The results are recorded and a graph of DO% versus time is i s plotted. It was shown that the increase of aeration rate, agitation speed and temperature will result in increase of the k La value.

2.0 INTRODUCTION

Most of the biochemical processes require oxygen as the source to yield the output. One of the examples is fermentation. Fermentation is defined as a process of producing chemicals from substrates by using organisms. The presence of organisms necessitates the oxygen supply to initiate the reaction and yield the desired product. Hence, dissolved oxygen concentration  becomes one one of the important important control variables in any aerobic fermentation. It is very important important to thoroughly understand the oxygen transfer to cells in a reactor. During an aerobic fermentation, oxygen has to be supplied continuously to the re action liquid in order to maintain the design concentration while oxygen is consumed by the organism. The oxygen is transferred from air bubbles and then sparged into the reaction solution and broken up and mixed by mechanical stirring. There are two factors that affect the capability of a reactor’s oxygen mass transfer namely air flow rate and the level of agitation. These two parameters give a significant effect on mass transfer coefficient, k La in aerobic bioreactors. Mass transfer coefficient, k La is a function of the mechanics of a particular reactor namely its constant dimension and its operating parameters.

DETERMINATION OF K La VALUE| 1

Among numerous methods of determining the mass transfer coefficient, k LA are: 1.

The static or gassing out method

2.

The dynamic method with growing culture

3.0 OBJECTIVES

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature.

4.0 THEORY

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature. This experiment is conducted by using a bioreactor and the result is taken every 5 seconds until the value constant or close to 100 which indicates the concentration of oxygen in the bioreactor is saturated There are several models which can be used to determine k La. All models used to evaluate k La assume ideal mixing of the two phases in the bioreactor and a negligible resistance of the gas  phase to oxygen transfer across the interface. This experiment uses the dynamic gassing out method, which gives the following oxygen mass transfer model:  

=  ( ∗   ) 

(1)

where CL  is the dissolved oxygen concentration and C* is the saturated dissolved oxygen concentration in the solution. Aeration to an active culture is briefly turned off and the unsteady-state mass balance of oxygen was tracked. The volumetric mass transfer coefficient, K La, indicates the rate of oxygen used for fermentation, taking into account all oxygen-consuming variables in the bioreactor. K La values are used in scaling up from laboratory scale to pilot scale or production scale bioreactors. The determination of the K La value for fermentation is important in order to maintain adequate transfer of oxygen in a bioreactor, for laboratory scale use or when scaling up to a larger  process. [1]

DETERMINATION OF K La VALUE| 2

Among numerous methods of determining the mass transfer coefficient, k LA are: 1.

The static or gassing out method

2.

The dynamic method with growing culture

3.0 OBJECTIVES

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature.

4.0 THEORY

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature. This experiment is conducted by using a bioreactor and the result is taken every 5 seconds until the value constant or close to 100 which indicates the concentration of oxygen in the bioreactor is saturated There are several models which can be used to determine k La. All models used to evaluate k La assume ideal mixing of the two phases in the bioreactor and a negligible resistance of the gas  phase to oxygen transfer across the interface. This experiment uses the dynamic gassing out method, which gives the following oxygen mass transfer model:  

=  ( ∗   ) 

(1)

where CL  is the dissolved oxygen concentration and C* is the saturated dissolved oxygen concentration in the solution. Aeration to an active culture is briefly turned off and the unsteady-state mass balance of oxygen was tracked. The volumetric mass transfer coefficient, K La, indicates the rate of oxygen used for fermentation, taking into account all oxygen-consuming variables in the bioreactor. K La values are used in scaling up from laboratory scale to pilot scale or production scale bioreactors. The determination of the K La value for fermentation is important in order to maintain adequate transfer of oxygen in a bioreactor, for laboratory scale use or when scaling up to a larger  process. [1]

DETERMINATION OF K La VALUE| 2

 Figure 4.1: Relationship between dissolved oxygen concentration and and time in dynamic gassing out method: Point A shows level of DO before it was consumed (air supply off); Point B represent air is pumped into the culture and the dissolved oxygen concentration increases as a function of time; Point C represent steady-state value. [2] Estimation of the K La of a fermentation system by using dynamic gassing-out techniques depends upon monitoring the increase in dissolved oxygen concentration of a solution during aeration and agitation. The oxygen concentration of the solution is lowered by gassing the liquid out with nitrogen gas. Aeration is then initiated at a constant air flow rate and the increase in dissolved oxygen tension (DOT) is monitored usi ng dissolved oxygen probe. The profile of DOT during deaeration and aeration is shown in Figure 1. Increased in DOT during aeration can be expressed by Eq. 1

dC  L dt 



 K  L a(C * C  L ) Qd    



(2)

where CL is dissolved oxygen conc., C E is saturated dissolve oxygen conc. and Q d is spesific respiration rate. Mass balance for the system:

Rate of change in O 2 conc. = Rate of O 2 in –   in –  Rate  Rate of O 2 out –   out –  Rate  Rate of usage Q d If microorganism is not present in the solution, Qd = 0, Eq 2 becomes eq 1 mentioned earlier.

DETERMINATION OF K La VALUE| 3

dC  L dt 



 K  L a(C * C  L )   

(1)

Can be written as, dC  L dt 

  K  L a.C  L   K  L a.C  *

dC  L

Plot of

dt   against

different value of CL will give a slope as  – KLa. However determining

dC  L dt   values

may be a problem. There are two methods in determination of KLa. First, the

difference method and second, integral method.

5.0 APPARATUS AND MATERIALS

1) Bioreactor 2) Distilled water 3) Stopwatch 4) Oxygen 5)  Nitrogen Gas 6) HI-BLOW (HP 80) linear air pump aerator

Figure 5.1: Bioreactor

DETERMINATION OF K La VALUE| 4

6.0 PROCEDURE Manipulated variable: Temperature

1. Set up the apparatus by making sure all the apparatus are present and in well condition. 2. PO2 probe is polarized for two hours before the main experiment is started. 3. The bioreactor’s parameter such as aeration and agitation are set fixed which are at 2L/m and 400 RPM respectively. 4. The pump is switched off. 5. Temperature is first set at 30˚C and prepared for 2 point calibration. The setting must  be done before purging the nitrogen. 6.  Nitrogen gas is purged into the system until the value of oxygen becomes 0% 7. Make sure that the bioreactor’s monitor stop blinking to indicate the calibration is done correctly even though the value becomes negative. 8. If the value is negative, the value is adjusted manually until the value is 0 9. The nitrogen valve is closed when reaching 0 and the nitrogen wire is disconnected from the bioreactor. 10. Pump is switched on. 11. The bioreactor is aerated with air for 100%. 12. Timer is set and reading is taken for every 5 seconds until the increasing DO % reaching three stable values. 13. The results are recorded and a graph of DO% versus time is plotted. 14. Step is repeated using different temperature which is 35˚C, 40˚C, 45˚C, and 50˚C. Manipulated variable: aeration

1. Set up the apparatus by making sure all the apparatus are present and in well condition. 2. PO2 probe is polarized for two hours before the main experiment is started. 3. The bioreactor’s parameter such as temperature and agitation are set fixed which are at 30˚C and 400 RPM respectively. 4. The pump is switched off. 5. Aeration is first set at 1L/m and prepared for 2 point calibration. The setting must be done before purging the nitrogen. 6.  Nitrogen gas is purged into the system until the value of oxygen becomes 0% 7. Make sure that the bioreactor’s monitor stop blinking to indicate the calibration is done correctly even though the value becomes negative. DETERMINATION OF K La VALUE| 5

8. If the value is negative, the value is adjusted manually until the value is 0 9. The nitrogen valve is closed when reaching 0 and the nitrogen wire is disconnected from the bioreactor. 10. Pump is switched on. 11. The bioreactor is aerated with air for 100%. 12. Timer is set and reading is taken for every 5 seconds until the increasing DO % reaching three stable values. 13. The results are recorded and a graph of DO% versus time is plotted. 14. Step is repeated using different aeration which is 1.5, 2.0, 2.5, and 3.0. Manipulated variable: agitation

1. Set up the apparatus by making sure all the apparatus are present and in well condition. 2. PO2 probe is polarized for two hours before the main experiment is started. 3. The bioreactor’s parameter such as aeration and temperature are set fixed which are at 2L/m and 30˚C respectively. 4. The pump is switched off. 5. Agitation is first set at 200rpm and prepared for 2 point calibration. The setting must  be done before purging the nitrogen. 6.  Nitrogen gas is purged into the system until the value of oxygen becomes 0% 7. Make sure that the bioreactor’s monitor stop blinking to indicate the calibration is done correctly even though the value becomes negative. 8. If the value is negative, the value is adjusted manually until the value is 0 9. The nitrogen valve is closed when reaching 0 and the nitrogen wire is disconnected from the bioreactor. 10. Pump is switched on. 11. The bioreactor is aerated with air for 100%. 12. Timer is set and reading is taken for every 5 seconds until the increasing DO % reaching three stable values. 13. The results are recorded and a graph of DO% versus time is plotted. 14. Step is repeated using different agitation which is 400, 600, 800, 1000 rpm.

DETERMINATION OF K La VALUE| 6

7.0 RESULTS AND CALCULATIONS 7.1 AERATION

Temperature: 30°C Agitation : 400 rpm Table 7.1: Table for aeration at 0.5 L/min at each 5 seconds

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175

DO 0 0 0.81 3.42 7.34 11.1 15.4 19.9 24.8 28.5 32.6 36.5 40.1 43.6 46.6 50.0 52.9 55.6 58.3 60.5 62.8 64.8 66.8 68.7 70.3 71.8 73.2 74.8 76.0 77.2 78.3 79.3 80.4 81.2 82.0

Aeration (0.5 L/min) C*- CL 100 100 99.19 96.58 92.66 88.9 84.6 80.1 75.2 71.5 67.4 63.5 59.9 56.4 53.4 50 47.1 44.4 41.7 39.5 37.2 35.2 33.2 31.3 29.7 28.2 26.8 25.2 24 22.8 21.7 20.7 19.6 18.8 18

Ln(C*-CL) 4.60517 4.60517 4.597037 4.570372 4.528937 4.487512 4.437934 4.383276 4.320151 4.269697 4.210645 4.15104 4.092677 4.032469 3.977811 3.912023 3.852273 3.793239 3.730501 3.676301 3.616309 3.561046 3.50255 3.443618 3.391147 3.339322 3.288402 3.226844 3.178054 3.126761 3.077312 3.030134 2.97553 2.933857 2.890372

DETERMINATION OF K La VALUE| 7

180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345 350 355 360 365 370 375 380

82.9 83.6 84.3 85.1 85.6 86.1 86.8 87.2 87.7 88.1 88.6 89.0 89.3 89.7 90.1 90.5 90.5 90.8 91.2 91.4 91.5 91.8 92.0 92.2 92.4 92.5 92.8 92.9 93.0 93.2 93.2 93.4 93.5 93.6 93.7 93.9 93.9 94.1 94.2 94.2 94.2

17.1 16.4 15.7 14.9 14.4 13.9 13.2 12.8 12.3 11.9 11.4 11 10.7 10.3 9.9 9.5 9.5 9.2 8.8 8.6 8.5 8.2 8 7.8 7.6 7.5 7.2 7.1 7 6.8 6.8 6.6 6.5 6.4 6.3 6.1 6.1 5.9 5.8 5.8 5.8

2.839078 2.797281 2.753661 2.701361 2.667228 2.631889 2.580217 2.549445 2.509599 2.476538 2.433613 2.397895 2.370244 2.332144 2.292535 2.251292 2.251292 2.219203 2.174752 2.151762 2.140066 2.104134 2.079442 2.054124 2.028148 2.014903 1.974081 1.960095 1.94591 1.916923 1.916923 1.88707 1.871802 1.856298 1.84055 1.808289 1.808289 1.774952 1.757858 1.757858 1.757858

DETERMINATION OF K La VALUE| 8

LN(C*-CL) vs Time 5 4.5 4 3.5     )

   L

y = -0.0082x + 4.5108 R² = 0.9687

3

   C       * 2.5    C     (    N 2    L

1.5 1 0.5 0 0

50

100

150

200

250

300

350

400

Time (s)

 Figure 7.1: Graph of Ln(C*-C  L ) vs time for aeration of 0.5L/min where the slope of the  graph is the k  La value

Based on the graph plotted above, the linear equation obtain is y = 0.0082x + 4.5108 Since -m = k L a and m = -0.0082 Therefore, k L a =

. s

x

 s 

= 29.52 h−

Table 7.2: Table of k La value for aeration at 0.5, 1.0, 1.5, 2.0 and 2.5 L/min Aeration (L/min) 0.5

k La (h-1) 29.52

1.0 1.5 2.0 2.5

34.92 82.08 100.80 123.48

DETERMINATION OF K La VALUE| 9

k La versus aeration 140 120 100    ) 80    h    (   a    L 60    k

   1   -

40 20 0 0

0.5

1

1.5

2

2.5

3

Aeration (L/min)

 Figure 7.2: Graph of k  La versus aeration 7.2 AGITATION

Temperature: 30°C Aeration : 2 L/min Table 7.3:Table for agitation at 200 rpm at each 5 seconds

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

DO 2.97 7.02 9.27 12.9 16.3 20.2 24.6 27.8 31.5 35.6 39.2 42.5 46.2 48.9 51.9 55.4 57.7 60.7 63.3 65.7

Agitation (200 rpm) C*- CL 97.03 92.98 90.73 87.1 83.7 79.8 75.4 72.2 68.5 64.4 60.8 57.5 53.8 51.1 48.1 44.6 42.3 39.3 36.7 34.3

Ln(C*-CL) 4.57502 4.53238 4.50789 4.46706 4.42724 4.37952 4.32281 4.27944 4.22683 4.16511 4.10759 4.05178 3.98527 3.93378 3.87328 3.79773 3.74479 3.67122 3.60278 3.53515

DETERMINATION OF K La VALUE| 10

105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340

67.9 69.9 71.7 73.7 75.6 77.0 78.6 80.0 81.6 82.8 84.0 85.0 85.9 87.1 88.0 88.7 89.7 90.3 91.1 91.7 92.3 92.9 93.5 93.9 94.4 94.9 95.4 95.7 96.1 96.4 96.6 97.0 97.3 97.6 97.9 98.1 98.3 98.5 98.8 98.9 99.1 99.3 99.4 99.5 99.6 99.6 99.8 100.0

32.1 30.1 28.3 26.3 24.4 23 21.4 20 18.4 17.2 16 15 14.1 12.9 12 11.3 10.3 9.7 8.9 8.3 7.7 7.1 6.5 6.1 5.6 5.1 4.6 4.3 3.9 3.6 3.4 3 2.7 2.4 2.1 1.9 1.7 1.5 1.2 1.1 0.9 0.7 0.6 0.5 0.4 0.4 0.2 0

3.46886 3.40453 3.34286 3.26957 3.19458 3.13549 3.06339 2.99573 2.91235 2.84491 2.77259 2.70805 2.64617 2.55723 2.48491 2.4248 2.33214 2.27213 2.18605 2.11626 2.04122 1.96009 1.8718 1.80829 1.72277 1.62924 1.52606 1.45862 1.36098 1.28093 1.22378 1.09861 0.99325 0.87547 0.74194 0.64185 0.53063 0.40547 0.18232 0.09531 -0.1054 -0.3567 -0.5108 -0.6931 -0.9163 -0.9163 -1.6094 -

DETERMINATION OF K La VALUE| 11

LN(C*-CL) vs Time 6 5 4    )    L 3    C      * 2    C    (    N1    L

y = -0.0163x + 5.1084 R² = 0.9659

0 -1

0

50

100

150

-2

200

250

300

350

400

Time (s)

 Figure 7.3: Graph of Ln(C*-C  L ) vs time for agitation of 200 rpm where the slope of the  graph is the k  La value

Based on the graph plotted above, the linear equation obtain is y = 0.0163x + 5.1084 Since -m= k L a and m=-0.0163 Therefore, k L a =

. s

x

 s 

= 58.68 h−

Table 7.4: Table of k La value for agitation at 200, 400, 600, 800 and 1000 rpm Agitation (rpm) 200 400

k La (h-1) 58.68 109.08

600

171.72

800 1000

232.20 263.52

DETERMINATION OF K La VALUE| 12

k La versus Agitation 300 250 200

   )    h    ( 150   a    L    k

   1   -

100 50 0 0

200

400

600

800

1000

1200

Agitation (rpm)

 Figure 7.4: Graph of k  La versus agitation

7.3 TEMPERATURE

Aeration : 2 L/min Agitation : 400 rpm Table 7.5: Table for temperature at 30oC at each 5 seconds

Time (s)

Temperature (30 0C)

5 10

DO 5.8

C*- CL 94.2

Ln(C*-CL) 4.54542

11.4

88.6

4.484132

15 20 25 30 35 40 45 50 55 60 65 70 75

18.6 26.6 32.8 46.8 51.4 55.6 59.9 64.2 67.1 70.3 73.2 75.8 77.7

81.4 73.4 67.2 53.2 48.6 44.4 40.1 35.8 32.9 29.7 26.8 24.2 22.3

4.399375 4.295924 4.207673 3.974058 3.883624 3.793239 3.691376 3.577948 3.493473 3.391147 3.288402 3.186353 3.104587

DETERMINATION OF K La VALUE| 13

80

79.7

20.3

3.010621

85 90 95

81.4 83 84.2

18.6 17 15.8

2.923162 2.833213 2.76001

100 105

84.6 85.4

15.4 14.6

2.734368 2.681022

110 115 120

85.7 86.2 86.7

14.3 13.8 13.3

2.66026 2.624669 2.587764

125 130

87.6 88.6

12.4 11.4

2.517696 2.433613

135 140 145

89.3 90.1 90.7

10.7 9.9 9.3

2.370244 2.292535 2.230014

150 155 160 165 170

91.2 91.9 92.4 92.8 93.1

8.8 8.1 7.6 7.2 6.9

2.174752 2.091864 2.028148

175 180 185 190 195 200 205 210 215 220 225 230 235 240

93.6 93.7 94.3 94.4 95.1 95.3 95.5 95.7 95.8 95.9 96 96.2 96.3 96.5

6.4 6.3 5.7 5.6 4.9 4.7 4.5 4.3 4.2 4.1 4 3.8 3.7 3.5

1.4350845 1.410987 1.386294 1.335001 1.308333 1.252763

245 250

96.5 96.5

3.5 3.5

1.252763 1.252763

1.9740810 1.931521 1.856298 1.84055 1.740466 1.722767 1.589235 1.547563 1.504077 1.458615

DETERMINATION OF K La VALUE| 14

LN(C*-CL) vs Time 5 4.5 4 3.5

   )    L 3    C      *2.5    C    (    N 2    L

y = -0.0134x + 4.2711 R² = 0.9732

1.5 1 0.5 0 0

50

100

150

200

250

300

Time (s)

 Figure 7.5: Graph of Ln(C*-C  L ) vs time for temperature at 30oC where the slope of the  graph is the k  La value

Based on the graph plotted above, the linear equation obtain is y = 0.0134x + 4.2711 Since -m= k L a and m=-0.0134 Therefore, k L a =

. s

x

 s 

= 48.24 h−

Table 7.6: Table of k La value for temperature at 30, 35, 40, 45 and 50 oC Temperature ( oC) 30

k La (h-1) 48.24

35 40 45

43.92 36.72 64.44

50

47.88

DETERMINATION OF K La VALUE| 15

kLa versus Temperature 70 60 50     )    1 40       h     (    a    L 30     k

20 10 0 30

35

40

45

50

Temperature (oC)

 Figure 7.6: Graph of k  La versus temperature

8.0 DISCUSSION

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature. This experiment is conducted by using a bioreactor and the result is taken every 5 seconds until the value constant or close to 100 which indicates the concentration of oxygen in the bioreactor is saturated There are several models which can be used to determine k La. All models used to evaluate k La assume ideal mixing of the two phases in the bioreactor and a negligible resistance of the gas  phase to oxygen transfer across the interface. This experiment uses the dynamic gassing out method, which gives the following oxygen mass transfer model:

 

=  ( ∗   )

where CL  is the dissolved oxygen concentration and C* is the saturated dissolved oxygen concentration in the solution. Aeration to an active culture is briefly turned off and the unsteady-state mass balance of oxygen was tracked. The volumetric mass transfer coefficient, K La, indicates the rate of oxygen used for fermentation, taking into account all oxygen-consuming variables in the bioreactor. K La values DETERMINATION OF K La VALUE| 16

are used in scaling up from laboratory scale to pilot scale or production scale bioreactors. The determination of the K La value for fermentation is important in order to maintain adequate transfer of oxygen in a bioreactor, for laboratory scale use or when scaling up to a larger  process.

Relationship between different aeration rate to dissolved oxygen concentration and mass transfer coeffi cient value To study the effect of aeration on mass transfer coefficient, k La value, we have conducted this experiment at different values of aeration which are 0.5, 1.0, 1.5, 2.0 and 2.5 L/min and the value of dissolved oxygen is recorded every 5 seconds. A graph of ln(C*-C L) against time is  plotted and the straight line is achieved. The negative slope or gradients of the straight line indicates the k La value. For 0.5 L/min, the k La value that we obtained is 29.52 h -1. At 1.0 L/min, 1.5 L/min, 2.0 L/min and 2.5 L/min the k La value obtained from the negative slope of the straight-line graph is 34.92 h-1, 82.08 h -1, 100.8 h -1 and 123.48 h -1 respectively. For graph of ln(C*-C L) against time, some of this graph will deviate from negative value of k La to zero (refer Figure 13.2). This is because the concentration of oxygen has reached the saturated dissolved oxygen concentration which is 100. This shows that all the oxygen in the  bioreactor has fully dissolved. Graph of k La against aeration is plotted (refer to Figure 7.2). From the graph plotted, we can see an increase trend in the k La value with respect to aeration rate. On the other hand, from Figure 7.1, 13.1 until 13.4, it seems that the time taken to reach the saturated level of dissolved oxygen concentration is decreasing with the increasing of aeration rates. Thus, conclusion that can be made based on the graph is the increase of aeration volumetric flowrate will increase the mass transfer coefficient, k La value.

Relationship between different agi tation speed to dissolved oxygen concentration and mass transfer coefficient value. The second experiment is to study the effect of different agitation speed on mass transfer coefficient, k La. To achieved this, an experiment is conducted with different values of agitation which are 200, 400, 600, 800 and 1000 rpm. The value of dissolved oxygen is recorded every 5 seconds until the concentration of dissolved oxygen in the bioreact or is saturated. A graph of

DETERMINATION OF K La VALUE| 17

ln(C*-CL) against time is plotted and it should give a straight line. The negative slope or gradients of the straight line indicates the mass transfer coefficient, k La value. From the graphs (refer Figure 7.2, Figure 13,5-13.8), the value of k La obtained for 200, 400, 600, 800 and 1000 rpm is 58.68 h -1, 109.08h -1, 171.72h -1, 232.2h-1  and 263.52h -1 correspondingly. Graph of k La against agitation speed is plotted (refer to Figure 7.4). From Figure 7.4, it can be seen the increment trends of the k La value with respect to the agitation speed. The increment of k La value from 400rpm to 800 rm increase linearly. It seems that the most efficient mixing is obtained in agitation speeds more than 400 and lower than 800 rpm. On the other hand, from Figure 7.3, 13.5 until 13.8, it seems that the time taken to reach the saturated level of dissolved oxygen concentration is decreasing with the increasing of aeration rates Based on the graph that has been plotted, we can conclude that the increase in agitation speed will increase the mass transfer coefficient, k La. There is only a significant enhancement on k La values for the medium agitation rate (400 rpm to 800rpm) that could be resulted from the higher  breakage and residence time of the air bubbles in the bioreactor media. For low agitation rates (200 rpm) the turbulence is not enough to trap and hold up the air bubbles and consequently  performance of volumetric mass transfer may not increase noticeably [3]. Therefore, based on the results obtained, agitation speed of 400 to 800 rpm would be beneficial for all the future  bioprocess operations that may lead to a higher productive biomass system.

Relationship between different temperature to dissolved oxygen concentration and mass transfer coeffi cient value The last experiment is to study the effect of different temperatures to mass t ransfer coefficient, k La value. Different temperatures are used to conduct this experiment which are 30 oC, 35oC, 40oC, 45oC and 50 oC. the concentration of dissolved oxygen is recorded for each 5 second until the concentration of dissolved oxygen in the bioreactor is saturated. A graph of ln(C*-C L) against time is plotted and it should give a straight line where the negative of the straight line indicates the mass transfer coefficient, k La value. From Figure 7.3,13.9 until 13.12, the value of k La obtained is 48.24h -1, 43.92 -1, 36.72h-1, 64.44h-1 and 47.88h -1 respectively. From these values, a graph of k La against temperature is  plotted. From the graph plotted in Figure 7.6, it seems that the k La unsteady trends in different temperature ranging from 30 oC to 50 oC begins from a decrement in temperature of 30 oC to DETERMINATION OF K La VALUE| 18

40oC and continues with a noticeable enhancement that can be seen from 40 oC to 45oC; then this trend approaches a decreasing trend in 50oC. On the other hand, from Figure 7.5, 13.9 until 13.12 it seems that the time taken to reach the saturated level of dissolved oxygen concentration is decreasing with the increasing of aeration rates Therefore, from the results obtained, the most efficient temperature to conduct this experiment is from 40oC to 45oC. From literature, it is noted that the mass transfer coefficient will increase with the increase of temperature. So, there may be some error occurred during conducting this experiment which effect the mass transfer coefficient value.

Possible cause of error i n determination of K L a by using dynamic gassing out technique There are two possible cause of error in this method. First, when the air supply is turned off, the dissolved oxygen concentration at point B has to be above the critical dissolved oxygen concentration (Ccritical). If the dissolved oxygen concentration is below C critical, anaerobic metabolism will occur rather than the aerobic metabolism. Second, this method requires an oxygen probe with fast response time; neglecting these facts will result in less accurate outcome. Transfer of oxygen from a gas phase to a liquid phase is complicated by presence of cells,  product formation, ionic species, and antifoaming agents. These can alter bubble size and liquid film resistance, which affect oxygen solubility. Resulting K La values are different from those  predicted from correlations for oxygen absorption into water. Therefore, it is important to have a reliable method for measuring K La in fermentation systems.

9.0 CONCLUSION

The objective for this experiment is to measure the volumetric mass transfer coefficient (k La) of a stirred tank reactor with bubble aeration at different aeration, agitation and temperature. This experiment is conducted by using a bioreactor and the result is t aken every 5 seconds until the value constant or close to 100 which indicates the concentration of oxygen in the bioreactor is saturated. Evaluation of the experimental data shows that k La values are affected by process variables such as aeration rate, agitation speed and temperature. From the above discussions, it was observed that with an increase of aeration rate, agitation speed and temperature, the mass transfer coefficient values increased. Also, it was found that agitation speeds of 400 to 800 DETERMINATION OF K La VALUE| 19

rpm would be beneficial for all the future bioprocess operations that may lead to a higher  productive biomass system. Also, it was observed that the increase in aeration rates, agitation speed and temperature will shorten the time to reach the saturated level of dissolved oxygen concentration.

10.0

RECOMMENDATION

There are some recommendations in order to improve this experiment to obtained more accurate results. Some of the recommendations are: 1. Make sure before conducting this experiment, consultation and discussion with lecturer and lab assistant has been made to ensure the right procedure and technique is used. 2. Make sure the bioreactor’s probe has been calibrated to prevent error when taking the data. 3. Make sure the data collected at every 5 second to ensure the correct data is taken as the value of dissolved oxygen is changing fast.

11.0

REFERENCES

1. Parakulsuksatid, P. 2000. Utilization of Microbubble Dispersion to Increase Oxygen Transfer in Pilot-Scale Baker’s Yeast Fermentation Unit. Master Thesis. Virginia Polytechnic Institute and State University, USA. 2. http://prizedwriting.ucdavis.edu/past/1997-1998/determination-of-volumetricmasstransfer-coefficient-in-a-stirred-sparged-bioreactor (240309) 3. Ali Karimi, Farideh Golbabaei, Momammad Reza Mehrnia, Masoud Neghab, Kazem Mohammad, Ahmad Nikpey, Mohammad Reza Pourmand, Iranian J Environ Health Sci Eng. 2013; 10(1): 6. Published online 2013 Jan 7. doi: 10.1186/1735-2746-10-6

DETERMINATION OF K La VALUE| 20

12.0

APPENDIX

AERATION Aeration : 1.0 L/min

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200

DO 0.05 2.58 6.65 11.5 17.1 22.6 27.6 33.0 37.1 42.3 46.4 50.7 57.8 61.0 63.7 66.4 68.6 71.0 73.0 74.8 76.6 78.3 79.8 81.0 82.2 83.3 84.3 85.3 86.1 87.0 87.7 88.3 88.9 89.5 90.0 90.5 90.9 91.1 91.7 92.0

Aeration (1.0 L/min) C*- CL 99.95 97.42 93.35 88.5 82.9 77.4 72.4 67 62.9 57.7 53.6 49.3 42.2 39 36.3 33.6 31.4 29 27 25.2 23.4 21.7 20.2 19 17.8 16.7 15.7 14.7 13.9 13 12.3 11.7 11.1 10.5 10 9.5 9.1 8.9 8.3 8

Ln(C*-CL) 4.60467 4.579032 4.536356 4.483003 4.417635 4.348987 4.282206 4.204693 4.141546 4.055257 3.981549 3.897924 3.74242 3.663562 3.591818 3.514526 3.446808 3.367296 3.295837 3.226844 3.152736 3.077312 3.005683 2.944439 2.879198 2.815409 2.753661 2.687847 2.631889 2.564949 2.509599 2.459589 2.406945 2.351375 2.302585 2.251292 2.208274 2.186051 2.116256 2.079442

DETERMINATION OF K La VALUE| 21

205 210 215 220 225 230 235 240 245 250 255 260 265 270 275 280 285 290 295 300 305 310 315 320 325 330 335 340 345

92.3 92.6 92.9 93.1 93.4 93.6 93.7 93.9 94.1 94.2 94.2 94.4 94.5 94.6 94.8 94.9 95.0 95.1 95.1 95.2 95.3 95.3 95.4 95.4 95.5 95.5 95.6 95.6 95.6

7.7 7.4 7.1 6.9 6.6 6.4 6.3 6.1 5.9 5.8 5.8 5.6 5.5 5.4 5.2 5.1 5 4.9 4.9 4.8 4.7 4.7 4.6 4.6 4.5 4.5 4.4 4.4 4.4

2.04122 2.00148 1.960095 1.931521 1.88707 1.856298 1.84055 1.808289 1.774952 1.757858 1.757858 1.722767 1.704748 1.686399 1.648659 1.629241 1.609438 1.589235 1.589235 1.568616 1.547563 1.547563 1.526056 1.526056 1.504077 1.504077 1.481605 1.481605 1.481605

Ln (C*-CL) VS Time 5 4.5 4

   ) 3.5    L    C   - 3    *2.5    C    (   n 2    L1.5

y = -0.0097x + 4.3 R² = 0.9363

1 0.5 0 0

50

100

150

200

250

300

350

400

Time (s)

 Figure 13.1: Graph of Ln(C*-C  L ) vs time for aeration of 1.0 L/min where the slope of the graph is the k  La value

DETERMINATION OF K La VALUE| 22

Based on the graph plotted above, the linear equation obtain is y = 0.0097x + 4.3 Since -m= k L a and m=-0.0097 Therefore, k L a =

. s

x

 s 

= 34.92 h−

Aeration : 1.5 L/min

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180

DO 3.57 7.57 11.9 16.7 21.4 26.0 31.5 36.3 40.8 45.0 50.0 54.4 58.6 62.2 65.4 68.6 71.4 73.8 76.3 78.5 80.8 82.3 84.4 85.7 87.1 88.4 89.6 90.6 91.5 92.5 93.2 93.8 94.5 95.1 95.7 96.1

Aeration (1.5 L/min) C*- CL 96.43 92.43 88.1 83.3 78.6 74 68.5 63.7 59.2 55 50 45.6 41.4 37.8 34.6 31.4 28.6 26.2 23.7 21.5 19.2 17.7 15.6 14.3 12.9 11.6 10.4 9.4 8.5 7.5 6.8 6.2 5.5 4.9 4.3 3.9

Ln(C*-CL) 4.56882 4.52645 4.47847 4.42245 4.36437 4.30407 4.22683 4.15418 4.08092 4.00733 3.91202 3.81991 3.72328 3.63231 3.54385 3.44681 3.35341 3.26576 3.16548 3.06805 2.95491 2.87356 2.74727 2.66026 2.55723 2.45101 2.34181 2.24071 2.14007 2.0149 1.91692 1.82455 1.70475 1.58924 1.45862 1.36098

DETERMINATION OF K La VALUE| 23

185 190 195 200 205 210 215 220 225 230 235 240 245 250 255

96.6 97.0 97.4 97.7 97.9 98.3 98.6 98.8 99.1 99.3 99.5 99.6 99.7 99.9 100.0

3.4 3 2.6 2.3 2.1 1.7 1.4 1.2 0.9 0.7 0.5 0.4 0.3 0.1 0

1.22378 1.09861 0.95551 0.83291 0.74194 0.53063 0.33647 0.18232 -0.1054 -0.3567 -0.6931 -0.9163 -1.204 -2.3026 -

Ln (C*-CL) VS Time 6 5 4 3

   )    L    C   - 2    *    C    ( 1   n    L

y = -0.0228x + 5.1861 R² = 0.9525

0

-1

0

50

100

150

200

250

300

-2 -3

Time (s)

 Figure 13.2: Graph of Ln(C*-C  L ) vs time for aeration of 1.5 L/min where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0228x + 5.1861 Since -m= k L a and m=-0.0228 Therefore, k L a =

. s

x

 s 

= 82.08 h−

Aeration : 2.0 L/min

Time (s)

5

DO 3.58

Aeration (2.0 L/min) C*- CL 96.42

Ln(C*-CL) 4.56871

DETERMINATION OF K La VALUE| 24

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200

3.78 12.8 18.9 25.4 31.6 37.3 43.0 48.8 54.0 59.2 63.2 67.2 70.7 74.0 77.1 79.6 81.9 84.0 86.0 87.8 89.1 90.6 91.8 93.2 93.9 94.8 95.3 96.1 96.6 97.2 97.7 98.0 98.4 98.8 99.1 99.4 99.5 99.8 100.0

96.22 87.2 81.1 74.6 68.4 62.7 57 51.2 46 40.8 36.8 32.8 29.3 26 22.9 20.4 18.1 16 14 12.2 10.9 9.4 8.2 6.8 6.1 5.2 4.7 3.9 3.4 2.8 2.3 2 1.6 1.2 0.9 0.6 0.5 0.2 0

4.56664 4.4682 4.39568 4.31214 4.22537 4.13836 4.04305 3.93574 3.82864 3.70868 3.6055 3.49043 3.37759 3.2581 3.13114 3.01553 2.89591 2.77259 2.63906 2.50144 2.38876 2.24071 2.10413 1.91692 1.80829 1.64866 1.54756 1.36098 1.22378 1.02962 0.83291 0.69315 0.47 0.18232 -0.1054 -0.5108 -0.6931 -1.6094 -

DETERMINATION OF K La VALUE| 25

Ln (C*-CL) VS Time 6 5 4    ) 3    L    C      * 2    C    (   n    L 1

y = -0.028x + 5.2029 R² = 0.9612

0 -1

0

50

100

-2

150

200

250

Time (s)

 Figure 13.3: Graph of Ln(C*-C  L ) vs time for aeration of 2.0 L/min where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.028x + 5.2029 Since -m= k L a and m=-0.028 Therefore, k L a =

. s

x

 s 

= 100.8 h−

Aeration : 2.5 L/min

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

DO 2.5 4.78 27.9 33.4 39.8 47.0 52.8 58.0 63.4 67.8 71.8 75.2 78.6 81.4 83.7 85.9

Aeration (2.5 L/min) C*- CL 97.5 95.22 72.1 66.6 60.2 53 47.2 42 36.6 32.2 28.2 24.8 21.4 18.6 16.3 14.1

Ln(C*-CL) 4.57985 4.55619 4.27805 4.1987 4.09767 3.97029 3.85439 3.73767 3.60005 3.47197 3.33932 3.21084 3.06339 2.92316 2.79117 2.64617

DETERMINATION OF K La VALUE| 26

85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170

88.0 89.6 91.1 92.5 93.6 94.6 95.5 96.3 96.9 97.5 98.0 98.5 98.8 99.2 99.5 99.6 99.9 100.0

12 10.4 8.9 7.5 6.4 5.4 4.5 3.7 3.1 2.5 2 1.5 1.2 0.8 0.5 0.4 0.1 0

2.48491 2.34181 2.18605 2.0149 1.8563 1.6864 1.50408 1.30833 1.1314 0.91629 0.69315 0.40547 0.18232 -0.2231 -0.6931 -0.9163 -2.3026 -

Ln (C*-CL) VS Time 6 5 4 3

y = -0.0343x + 5.1468 R² = 0.9429

   )    L    C   - 2    *    C    ( 1   n    L

0

-1

0

20

40

60

80

100

120

140

160

180

-2 -3

Time (s)

 Figure 13.4: Graph of Ln(C*-C  L ) vs time for aeration of 2.5 L/min where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0343x + 5.1468 Since -m= k L a and m=-0.0343 Therefore, k L a =

. s

x

 s 

= 123.48 h−

DETERMINATION OF K La VALUE| 27

AGITATION

Agitation : 400rpm

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190

DO 4.50 7.25 15.3 21.8 27.6 33.4 39.5 45.5 51.1 55.4 60.8 64.6 68.5 71.1 74.9 78.0 80.7 83.8 85.1 86.8 88.5 90.0 91.1 92.3 94.5 95.4 96.0 96.6 97.2 97.7 98.0 98.5 98.9 99.3 99.5 99.6 99.8 100.0

Agitation (400 rpm) C*- CL 95.5 92.75 84.7 78.2 72.4 66.6 60.5 54.5 48.9 44.6 39.2 35.4 31.5 28.9 25.1 22 19.3 16.2 14.9 13.2 11.5 10 8.9 7.7 5.5 4.6 4 3.4 2.8 2.3 2 1.5 1.1 0.7 0.5 0.4 0.2 0

Ln(C*-CL) 4.55913 4.52991 4.43912 4.35927 4.28221 4.1987 4.10264 3.9982 3.88978 3.79773 3.66868 3.56671 3.44999 3.36384 3.22287 3.09104 2.96011 2.78501 2.70136 2.58022 2.44235 2.30259 2.18605 2.04122 1.70475 1.52606 1.38629 1.22378 1.02962 0.83291 0.69315 0.40547 0.09531 -0.3567 -0.6931 -0.9163 -1.6094 -

DETERMINATION OF K La VALUE| 28

Ln (C*-CL) VS Time 6 5 4    ) 3    L    C      * 2    C    (   n    L 1

y = -0.0303x + 5.2698 R² = 0.9523

0 -1

0

50

100

-2

150

200

Time (s)

 Figure 13.5: Graph of Ln(C*-C  L ) vs time for agitation of 400 rpm where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0303x + 5.2698 Since -m= k L a and m=-0.0303 Therefore, k L a =

. s

x

 s 

= 109.08 h−

Agitation: 600rpm

Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

DO 5.8 14.4 24.4 33.7 42.3 50.8 58.3 65.5 71.4 76.4 80.7 84.2 87.0 89.6 91.8 93.5

Agitation (600 rpm) C*- CL 94.2 85.6 75.6 66.3 57.7 49.2 41.7 34.5 28.6 23.6 19.3 15.8 13 10.4 8.2 6.5

Ln(C*-CL) 4.54542 4.44969 4.32546 4.19419 4.05526 3.89589 3.7305 3.54096 3.35341 3.16125 2.96011 2.76001 2.56495 2.34181 2.10413 1.8718

DETERMINATION OF K La VALUE| 29

85 90 95 100 105 110 115 120 125

94.9 95.9 97.0 98.0 98.6 99.2 99.5 99.9 100.0

5.1 4.1 3 2 1.4 0.8 0.5 0.1 0

1.62924 1.41099 1.09861 0.69315 0.33647 -0.2231 -0.6931 -2.3026 #NUM!

Ln (C*-CL) VS Time 6 5 4 3

   )    L    C   - 2    *    C    ( 1   n    L

y = -0.0477x + 5.3349 R² = 0.9237

0

-1

0

20

40

60

80

100

120

140

-2 -3

Time (s)

 Figure 13.6: Graph of Ln(C*-C  L ) vs time for agitation of 600 rpm where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0477x + 5.3349 Since -m= k L a and m=-0.0477 Therefore, k L a =

. s

x

 s 

= 171.72 h−

Agitaton: 800rpm

Time (s)

5 10 15 20 25

DO 18.7 22.5 32.8 45.7 57.3

Agitation (800 rpm) C*- CL 81.3 77.5 67.2 54.3 42.7

Ln(C*-CL) 4.39815 4.35028 4.20767 3.99452 3.7542

DETERMINATION OF K La VALUE| 30

30 35 40 45 50 55 60 65 70 75 80 85 90 95

66.7 74.8 80.2 84.9 88.7 91.8 94.1 95.8 97.0 98.0 98.9 99.5 99.9 100.0

33.3 25.2 19.8 15.1 11.3 8.2 5.9 4.2 3 2 1.1 0.5 0.1 0

3.50556 3.22684 2.98568 2.71469 2.4248 2.10413 1.77495 1.43508 1.09861 0.69315 0.09531 -0.6931 -2.3026 -

Ln (C*-CL) VS Time 6 5 4 3

   )    L    C   - 2    *    C    ( 1   n    L

y = -0.0645x + 5.3184 R² = 0.9155

0

-1

0

20

40

60

80

100

-2 -3

Time (s)

 Figure 13.7: Graph of Ln(C*-C  L ) vs time for agitation of 800 rpm where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0645x + 5.3184 Since -m= k L a and m=-0.0645 Therefore, k L a =

. s

x

 s 

= 232.2 h−

DETERMINATION OF K La VALUE| 31

Agitation: 1000rpm

Time (s)

Agitation (1000 rpm) C*- CL 88.6 75.1 57.5 41.1 30.8 22.1 15.9 11.2 8.1 5.5 3.5 2.2 1.2 0.5 0

DO 11.4 24.9 42.5 58.9 69.2 77.9 84.1 88.8 91.9 94.5 96.5 97.8 98.8 99.5 100.0

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Ln(C*-CL) 4.48413 4.31882 4.05178 3.71601 3.42751 3.09558 2.76632 2.41591 2.09186 1.70475 1.25276 0.78846 0.18232 -0.6931 -

Ln (C*-CL) VS Time 6 5 4    )    L    C   - 3    *    C    (   n 2    L

y = -0.0732x + 5.1687 R² = 0.9742

1 0 0

10

20

30

-1

40

50

60

70

80

Time (s)

 Figure 13.8: Graph of Ln(C*-C  L ) vs time for agitation of 1000 rpm where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0732x + 5.1687 Since -m= k L a and m=-0.0732 Therefore, k L a =

. s

x

 s 

= 263.52 h−

DETERMINATION OF K La VALUE| 32

TEMPERATURE Temperature: 35oC Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210

DO 1.98 6.71 14.00 22.20 30.10 38.10 44.10 49.40 55.80 59.50 64.80 68.30 71.50 74.10 76.40 78.50 80.30 81.90 83.70 85.20 86.20 87.10 87.90 88.60 89.30 89.90 90.40 90.70 91.00 91.30 91.80 92.10 92.30 92.50 92.90 93.00 93.20 93.30 93.50 93.70 93.80 93.90

Temperature (35 0C) C*- CL 98.02 93.29 86 77.8 69.9 61.9 55.9 50.6 44.2 40.5 35.2 31.7 28.5 25.9 23.6 21.5 19.7 18.1 16.3 14.8 13.8 12.9 12.1 11.4 10.7 10.1 9.6 9.3 9 8.7 8.2 7.9 7.7 7.5 7.1 7 6.8 6.7 6.5 6.3 6.2 6.1

Ln(C*-CL) 4.585172 4.535713 4.454347 4.354141 4.247066 4.12552 4.023564 3.923952 3.788725 3.701302 3.561046 3.456317 3.349904 3.254243 3.161247 3.068053 2.980619 2.895912 2.791165 2.694627 2.624669 2.557227 2.493205 2.433613 2.370244 2.312535 2.261763 2.230014 2.197225 2.163323 2.104134 2.066863 2.04122 2.014903 1.960095 1.94591 1.916923 1.902108 1.871802 1.84055 1.824549 1.808289

DETERMINATION OF K La VALUE| 33

215 220 225 230 235 240 245

94.00 94.10 94.20 94.40 94.50 94.50 94.50

6 5.9 5.8 5.6 5.5 5.5 5.5

1.791759 1.774952 1.757858 1.722767 1.704748 1.704748 1.704748

Ln (C*-CL) VS Time 5 4.5 4 3.5

   )    L 3    C      *2.5    C    (   n 2    L

y = -0.0122x + 4.2262 R² = 0.9196

1.5 1 0.5 0 0

50

100

150

200

250

300

Time (s)

 Figure 13.9: Graph of Ln(C*-C  L ) vs time for temperature at 350C where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0122x + 4.2262 Since -m= k L a and m=-0.0122 Therefore, k L a =

. s

x

 s 

= 43.92 h−

Temperature: 40oC Time (s)

5 10 15 20 25 30 35

DO 2.80 2.91 3.09 3.36 6.18 11.70 19.90

Temperature (400C) C*- CL 97.2 97.09 96.91 96.64 93.82 88.3 80.1

Ln(C*-CL) 4.576771 4.575638 4.573783 4.570993 4.541378 4.48074 4.383276

DETERMINATION OF K La VALUE| 34

40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240 245 250 255 260 265 270 275

28.20 36.70 43.40 49.00 54.70 59.50 63.50 67.60 70.80 73.30 75.60 77.70 79.60 81.30 82.70 83.90 84.80 85.50 86.20 86.90 87.50 88.00 88.50 89.00 89.30 89.60 89.80 90.10 90.40 90.50 90.60 90.80 91.00 91.20 91.20 91.60 91.70 91.80 91.80 91.90 92.00 92.10 92.10 92.20 92.30 92.40 93.00 93.00

71.8 63.3 56.6 51 45.3 40.5 36.5 32.4 29.2 26.7 24.4 22.3 20.4 18.7 17.3 16.1 15.2 14.5 13.8 13.1 12.5 12 11.5 11 10.7 10.4 10.2 9.9 9.6 9.5 9.4 9.2 9 8.8 8.8 8.4 8.3 8.2 8.2 8.1 8 7.9 7.9 7.8 7.7 7.6 7 7

4.273884 4.147885 4.036009 3.931826 3.813307 3.701302 3.597312 3.478158 3.374169 3.284664 3.194583 3.104587 3.015535 2.928524 2.850707 2.778819 2.721295 2.674149 2.624669 2.572612 2.525729 2.484907 2.442347 2.397895 2.370244 2.341806 2.322388 2.292535 2.261763 2.251292 2.24071 2.219203 2.197225 2.174752 2.174752 2.128232 2.116256 2.104134 2.104134 2.091864 2.079442 2.066863 2.066863 2.054124 2.04122 2.028148 1.94591 1.94591

DETERMINATION OF K La VALUE| 35

280

93.00

7

1.94591

Ln (C*-CL) VS Time 5 4.5 4 3.5

   )    L 3    C      *2.5    C    (   n 2    L

y = -0.0102x + 4.3339 R² = 0.8876

1.5 1 0.5 0 0

50

100

150

200

250

300

Time (s)

 Figure 13.10: Graph of Ln(C*-C  L ) vs time for temperature at 400C where the slope of the  graph is the k  La value Based on the graph plotted above, the linear equation obtain is y = 0.0102x + 4.3339 Since -m= k L a and m=-0.0102 Therefore, k L a =

. s

x

 s 

= 36.72 h−

Temperature: 45oC Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65

DO 1.37 2.30 3.90 4.87 5.10 5.67 7.30 10.50 12.80 15.20 21.00 23.10 27.50

Temperature (45 OC) C*- CL 98.63 97.7 96.1 95.13 94.9 94.33 92.7 89.5 87.2 84.8 79 76.9 72.5

Ln(C*-CL) 4.591375 4.581902 4.565389 4.555244 4.552824 4.546799 4.529368 4.494239 4.468204 4.440296 4.369448 4.342506 4.283587

DETERMINATION OF K La VALUE| 36

70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185

30.60 35.70 39.70 42.70 48.20 56.20 63.40 70.40 75.70 81.00 83.50 85.90 85.90 86.70 87.30 88.50 89.00 89.50 92.40 92.40 92.50 92.70 92.70 92.70

69.4 64.3 60.3 57.3 51.8 43.8 36.6 29.6 24.3 19 16.5 14.1 14.1 13.3 12.7 11.5 11 10.5 7.6 7.6 7.5 7.3 7.3 7.3

4.239887 4.16356 4.099332 4.048301 3.94739 3.779634 3.600048 3.387774 3.190476 2.944439 2.80336 2.646175 2.646175 2.587764 2.541602 2.442347 2.397895 2.351375 2.028148 2.028148 2.014903 1.987874 1.987874 1.987874

Ln (C*-CL) VS Time 6 5    ) 4    L    C      *3    C    (   n    L2

y = -0.0179x + 5.1639 R² = 0.9426

1 0 0

50

100

150

200

Time (s)

 Figure 13.11: Graph of Ln(C*-C  L ) vs time for temperature at 450C where the slope of the  graph is the k  La value

DETERMINATION OF K La VALUE| 37

Based on the graph plotted above, the linear equation obtain is y = 0.0179x + 5.1639 Since -m= k L a and m=-0.0179 Therefore, k L a =

. s

x

 s 

= 64.44 h−

Temperature: 50oC Time (s)

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170

DO 22.20 28.40 32.10 38.50 45.20 51.80 57.00 62.40 67.20 70.20 73.40 75.90 80.20 81.50 82.90 84.00 85.00 86.00 86.70 87.20 88.00 88.40 89.00 89.40 89.80 90.20 90.50 90.60 90.70 90.90 91.10 91.20 91.50 91.80

Temperature (50 OC) C*- CL 77.8 71.6 67.9 61.5 54.8 48.2 43 37.6 32.8 29.8 26.6 24.1 19.8 18.5 17.1 16 15 14 13.3 12.8 12 11.6 11 10.6 10.2 9.8 9.5 9.4 9.3 9.1 8.9 8.8 8.5 8.2

Ln(C*-CL) 4.354141 4.271095 4.218036 4.119037 4.00369 3.875359 3.7612 3.627004 3.490429 3.394508 3.280911 3.182212 2.985682 2.917771 2.839078 2.772589 2.70805 2.639057 2.587764 2.549445 2.484907 2.451005 2.397895 2.360854 2.322388 2.282382 2.251292 2.24071 2.230014 2.208274 2.186051 2.174752 2.140066 2.104134

DETERMINATION OF K La VALUE| 38