Kinetic Modeling And Functional Parameters Evaluation Of ... · International Journal of Basic &...

International Journal of Basic & Applied Sciences IJBAS-IJENS Vol:13 No:03 33

138903-4747- IJBAS-IJENS @ June 2013 IJENS I J E N S

Kinetic Modeling And Functional Parameters

Evaluation Of Mass Transfer Rate

On Bio Coagulant Interface In Pharmaceutical Industry Effluent.

*Ugonabo V.I1, Menkiti, M.C.

2. Osoka, E.C

3, Atuanya, C.U.

4 and Onukwuli, O.D

5.

1,2,5 Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria.

3 Department of Chemical Engineering, Federal University of Technology, Owerri , Nigeria.

4 Department of Metallurgical And Materials Engineering, Nnamdi Azikiwe University, Awka, Nigeria.

*E-mail:[email protected]: Telephone: +23408033481851

Abstract-- The kinetic modeling and functional parameters

evaluation of mass transfer rate on bio coagulant interface in pharmaceutical industry effluent has been investigated at room

temperature. To remove the mass particles (in form of total

dissolved and suspended solids, TDSS) from the effluent

sample. The experiments were carried out using standard Jar

test method at varying pH and coagulant doses respectively, while the bio coagulant processing was based on the work

reported by [13]. The functional parameters generated indicate

the optimum conditions to be 7, 0.6g/l and 40 minutes for pH,

dosage and time, respectively. At the optimal pH, TDSS

reduced from 1380 to 218.04 mg/l, equivalent to 84.20% removal efficiency at rate constant (k) of 6.332E – 05 l/g.min

and corresponding coagulation period (1/2) of 0.38mins. Thus

confirming the biocoagulant as effective bioflocculant . In

comparative terms, the biocoagulant was found to be more

effective for TDSS removal than Alum at the conditions of the experiment.

Index Term-- Bio coagulant, Effluent, Mass transfer, kinetics,

Coag- flocculation.

1.0 INTRODUCTION

Pharmaceutical Industry Effluent (PIE) is a major Waste

product from production of pharmaceutical products. It is an

objectionable pollutant deleterious to the water networks of

the pharmaceutical host communities in Nigeria.

Waste water disposal from pharmaceutical activities and

other sources are the major problem being faced by most

developing countries like Nigeria because of lack of

wherewithal; modern technologies, and to greater extent

stringent measures on the part of government.

The most common problem in disposal of wastewaters is

their color, and turbidity. Finely dispersed total dissolved

and suspended solid particles are responsible for color and

turbidity of the wastewaters [12],[25]. Coagulation and

flocculation has been found to be effective in the removal of

color, turbidity inherent in wastewaters [8],[9],[17],[20][25].

The total dissolved and suspended solid particles inherent in

wastewaters generally, carry a negative electrical charge.

These particles are surrounded by an electrical double layer

as a result of sorption of positively charged ions from the

sample medium, which now prevents the rate of

approaching each other [23]. Coagulation process is

employed by the addition of positively electrical charge

coagulant into the waste water rich in dissolved and

suspended solid particles, resulting in compression of the

double layer and neutralization of electrostatic surface

potential of the particles. This phenomenon enables the

destabilized particles to stick together when in contact with

each order to form microscopic coagulated particles. In the

other hand flocculation process is the aggregation of these

microscopic coagulated particles to form larger flocs for

easy removal from wastewater medium.

Readily, coagulation–flocculation has been

accomplished through aluminum and iron salts as synthetic

coagulants. Though, they are very effective, but the

production of large volume of insoluble sludge and other

negative attributes undermines their effectiveness. To avert

these inherent problems, focus is hereby given to the study

of coag-floculation performance of plant origin, corchorus

olitorus seed - biocoagulant. Corchorus olitorus, a

herbaceous plant of the family tiliaceae, are edible, non-

toxic, biogradable and biocompatible substances with some

medicinal values are found in large quantity in western

Nigeria. The seed kernels of corchorus olitorus contains

reasonable amount of positively charged soluble proteins

which bind with negatively charged dissolved and

suspended solid particles in wastewater to encourage floc

formation [18]. Previous results obtained from coag-

flocculation performance in pharmaceutical wastewater

using corchorus olitorus seed coagulant was impressive

[27].

Against this backdrop, this work intend to compare

the coag-flocculation performance of corchorus olitorus



seed coagulant with aluminum sulphate (Alum) under

varying pH of pharmaceutical effluent, dosage, settling time

at the same experimental conditions. The result obtained

from this work, will determine whether corchorus olitorus

seed coagulant can be applied in large scale water treatment

technology as a good substitute for aluminum sulphate

which has dominated the exercise in the past. Ultimately if

found effective and efficient, the post usage handling and

health challenges associated with aluminum sulphate

coagulant can be ameliorated. Hence determining the rate

of adsorption of total dissolved and suspended particles on

the coagulant interface.

2.0 THEORETICAL PRINCIPLES AND MODEL DEVELOPMENT

For a uniformly interacting coag-flocculation

system where Brownian stiochastic force dominates; the

heating/stirring of the system produces temperature gradient

which causes migration of the particles driven by thermally

excited gradients of surface tension[3],[10],[22].

S = -

ST

2.1

Where = -

linT r1

S is the surface gradient operator; is the surface tension

and T is the coefficient of interfacial thermal elasticity. The

effect is that particles moving randomly with different

velocity can coag-flocculate to form larger flocs.

Assuming monodisperse, perfect elasticity and bi-

particle collisions, the general mode for microkinetic coag-

flocculation is given as[29],[30].

k-i ∞

=

2.2

i=1 i=1

(k = 1,2,3)

is the rate of change of concentration of particle of size,

K

Where t is time, n1 denotes number of

monoparticles per unit volume;

nk is number of the flocs of K aggregates (k = 2,3,4…..) per

unit volume; acf (i,j =- 1,2,3….) is a function of coag

flocculation transport mechanism; denotes flux of flocs

of size k.

In case of irreversible coagulation qk = 0. The

total concentration of flocs, N and total concentration of the

constituent particles (including those in flocculated form)

, are given by the expressions

N = , = K

2.3

K=1

Also = 4 i,j ( + ) Ei, j

2.4

Similarly, for Brownian transport is given as [30].

( )BR =

εp

2.5

Where D(0)

i,j is the relative diffusion coefficients for two

flocs of radii Ri and Rj, and aggregation number i and j,

respectively; Ei,j is the collision efficiency[31],[33]; εp = Ei,j

collision efficiency. The aggregation rate of intending

potential particles during coag-flocculation can be obtained

by the combination of equations 2.2 and 2.5 yields

-

= K

2.6

where is the total concentration of constituent particles at

time t as expressed in equation 2.3 above

K is the coag-flocculation constant

is the order of coag-flocculation process.

Equally, ( )BR = εp

2.7

Where is rate constant of flocculation for rapid

flocculation. However, for second order ( ) reaction rate

constant ( )

= 8Ro

2.8

Where is particle radius

is diffusion coefficient for intending flocculating

particles i and j

= +

2.9

Where is relative particle radius for and

Putting = and =

Equation 2.9 transposes to = 2

2.10

From Einstein’s approach to the theory of diffusivity .

=

2.11

And from stokes equation B =

2.12

Where KB – is Boltzman’s constant (J/K)

T – is absolute temperature (K)

B – is the friction factor

V – is the velocity acquired by potential aggregating

particles under the influence of stiochastic force (as result of

heat and stirring of the system).



But for a solid sphere of radius Ro, the stokes equation gives

B = 6 Ro

2.13

where, - is the viscosity of the coag-flocculating fluid.

Substituting equation 2.11, 2.13 into 2.8 yields

Kf =

2.14

Combining equations 2.7 to 2.14 gives:

K =

(acf)BR

2.15

Substituting equations 2.5 and 2.15 into 2.6 yields

-

=

εp

Nt

2.16

For microkinetic aggregation, theoretically equals 2 as

given, [18].

From Ficks first law; number of particles entering sphere

with radius RP per unit time Jt.

= 4Rp2 D

1

2.17

where is flux (number of particles per unit surface and

unit time at position Rp) integrating equation 2.16 at initial

conditions = 0, = 2 .

∫

= ∫

2.18

Thus = 8D1

2.19

Generally, for particle of same size under the

influence of Brownian motion. The initial rate of coag-

flocculation is

-

= εp

2.20

Substituting equations 2.12, 2.13 and 2.19 into 2.20 yields

-

=

εp

2.21

Similarly

-

=

εp

at t > o

Hence, from 2.20 putting, = 2; equation 2.6 transposed to

-

= - K

2.22

Integrating

∫

= - K∫

2.23

Thus

= Kt +

2.24

Plot of

vs t gives a slope of K and intercept of

On evaluation of equation 2.24, 1/2 (Coagulation period) can

be determined.

=

2.25

1 +

Where =

2.26

Substituting equation 2.26 into 2.25 yields

= 2.27

1 +

As t = equation 2.26 transpose to;

=

2.28

Similarly

= 0.5

As 0.5 ;

,

Hence equation 2.25 becomes

= (0.5 )

-1

2.29



For a coagulation period, where total number of

concentration is halves, solving equation 2.2 results in

the general expression for particle of mth

order.

(t) = [

]m-1

[1 +

]

m + 1

2.30

Recall;

=

or (0.5 )

-1

For single particle (m = 1)

= 1

2.31

1 +

2

t = 1

2.32

1 +

2

For double particles (m = 2)

= [

]2

1 +

3

2.33

= [

]2

1 +

3

2.34

For triple particles (m = 3)

= [

]3

1 +

4

2.35

= [

]3

2.36

1 +

4

Finally, the evaluation of coag-flocculation efficiency or

coag-flocculant performance of the process was obtained by

applying the relation below.

E i, j (%) = - x 100

2.37

3.0 MATERIALS AND METHODS

3.1 Material sampling, preparation and characterization

3.1.1. Pharmaceutical Industry effluent:

The effluent was taken from pharmaceutical

industry located in Anambra State, Nigeria. The effluent

was characterized in accordance with standard procedure for

examination of water and wastewater analysis[2],[32], and

presented in table 1.

3.1.2 Corchorus Olitorus seed sample.

The seed sample was sourced from Dugbe Market, Ibadan,

Nigeria and processed to bio-coagulant, based on the work

reported by [27]. Subsequently, the sample was

characterized on the basis of [1] AOAC standard method

and presented in table 2.

3.1.3 Coag-Flocculation Experiments

Experiments were conducted using conventional

Jar test apparatus. Appropriate dose of bio-coagulant in the

range of (0.1 to 0.7) g/l was added to 250ml of

pharmaceutical effluent. The suspension tuned to pH range 1

– 13 by addition of 10MHCL/NaOH was subjected to 2

mins rapid mixing (120 rpm), 20mins of flow mixing

(20rpm) and followed by 40mins settling time. During

settling, sample were withdrawn from 2cm depth and

change in total dissolved and suspended solid particle (in

mg/l) measured for aggregation kinetics using lab-tech.

model 212R turbid meter at 2, 4, 6,10, 20, 30 and 40

minutes under room temperature. The same procedure was

repeated using aluminum sulphate as a coagulant for

comparative purposes. The data were subsequently fitted in

appropriate kinetic models for performance evaluations.



T ABLE I

CHARACTERISTIC OF PHARMACEUTICAL INDUSTRY EFFLUENT SAMPLE BEFORE TREATMENT

Parameter Values

Temperature (oC) 28

Electrical conductivity (µs/cm) 4.9 x 102

pH 3.87

Phenol (mg/l) Nil

Odor acidic

Total hardness (mg/l) 6,000

Calcium (mg/l) 594

Magnesium (mg/l) 250

Chlorides (mg/l) 100

Dissolved oxygen (mg/l) 20

Biochemical oxygen Demand (mg/l) 50

Turbidity (mg/l) 1256

Iron (mg/l) Nil

Nitrate (mg/l) Nil

Total acidity (mg/l) 250

Total dissolved solids (mg/l) 225

Total suspended solids (mg/l) 57.25

Total viable court (cfu/mil) 9 x 101

Total coliform MPN/ 100ml Nil

Total coliform count, cfu/nil 1 x 101

Faecal count MPN/mL Nil

Clostridium perfrigens MPN/ml Nil

T ABLE II CHARACTERISTICS OF BIO-CAOGULANT PRECURSOR (CORCHORUS OLITORUS SEED)

Parameter Value

Moisture content % 10

Ash content % 10

Fat content % 8.00

Crude fibre % 20

Crude protein % 29.5

Carbohydrate % 22.43



T ABLE III

COAG-FLOCCULATION KINETIC PARAMETERS AND LINEAR REGRESSION COEFFICIENT OF COSC AT VARYING DOSAGE AND PH1

Parameters 0.1g/l 0.2g/l 0.3g/l 0.4g/l 0.5g/l 0.6g/l 0.7g/l

2.000 2.000 2.000 2.000 2.000 2.000 2.000

R2 0.655 0.917 0.703 0.924 0.861 0.817 0.859

K(l/g.min) 1.0E-05 7.34E-06 8.837E-06 1.095E-05 2.03E-05 1.150E-05 8.08E-06

Kf(l3/min) 1.5468E-19 1.5468E-19 1.5468E-19 1.5479E-19 1.5479E-19 1.5484E-19 1.5484E-19

(acf)BR(l3/g.min)2.0E-05 1.468E-05 1.7674E-05 2.19E-05 4.06E-05 2.3E-05 1.616E-05

p(g -1

) 1.2930E+13 9.4906E+13 1.1426E+14 1.4148E+14 2.6229E+14 1.4854E+14 1.0437E+14

1/2(min) 144.93 197.45 164.00 132.35 71.39 126.02 179.37

(-r) 1.0E-05Nt2

7.34E-06Nt2

8.837E-06Nt2

1.095E-05Nt2

2.03E-05Nt2

1.150E-05Nt2

8.08E-06Nt2

N0(g/l3) 873.0574 853.2423 818.0628 931.5324 105.3060 904.56807 1162.7907

T ABLE IV

COAG-FLOCCULATION KINETIC PARAMETERS AND LINEAR REGRESSION COEFFICIENT OF COSC AT VARYING DOSAGE ANDPH3


2.000 2.000 2.000 2.000 2.000 2.000 2.000

R2 0.932 0.722 0.976 0.839 0.847 0.931 0.800

K(l3/g.min) 1.2E-05 7.49E-06 2.145E-05 8.287E-06 9.86E-06 1.030E-05 8.29E-06

Kf(l3/min) 1.5443E-19 1.5443E-19 1.5443E-19 1.5448E-19 1.5448E-19 1.5448E-19 1.5448E-19


p(g -1

) 1.5541E+14 9.7002E+13 2.7780E+14 1.0729E+14 1.2765E+14 1.3335E+14 1.07337E+14

1/2(min) 90.58 145.12 50.67 131.16 110.24 105.53 131.12

(-r) 1.02E-05Nt2

7.49E-06Nt2

2.145-05Nt2

8.287-06Nt2

9.86E-065Nt2

1.030E-05Nt2

8.29E-06Nt2

N0(g/l3) 973.7098 1057.0825 1138.0448 1157.5414 1368.1762 1203.5143 1251.5645



T ABLE V

COAG-FLOCCULATION KINETIC PARAMETERS AND LINEARREGRESSION COEFFICIENT OF COSC AT VARYING DOSAGE AND PH 5


2.000 2.000 2.000 2.000 2.000 2.000 2.000

R2 0.851 0.844 0.689 0.919 0.871 0.806 0.850

K(l3/g.min) 6E-06 5.83E-06 7.437E-06 9.751E-06 1.26E-05 9.7E-06 1.4E-05

Kf(l3/min) 1.5750E-19 1.5750E-19 1.5775E-19 1.5775E-19 1.5775E-19 1.5775E-19 1.5801E-19


p(g -1

) 7.6190E+13 7.4032E+13 1.4288E+13 1.2363E+14 1.25975E+14 1.2298E+14 2.7720E+14

1/2(min) 241.55 248.59 194.87 148.63 115.02 149.41 103.52

(-r) 6E-06Nt2

5.83E-06Nt2

7.437E-06Nt2

9.751E-06Nt2

1.26E-05Nt2

9.7E-06Nt2

1.4E-05Nt2

N0(g/l3) 622.6650 914.9131 955.6575 929.0227 922.5943 1042.9704 1126.1261

T ABLE VI

COAG-FLOCCULATION KINETIC PARAMETERS AND LINEARREGRESSION COEFFICIENT OF COSC AT VARYING DOSAGE AND pH 7


2.000 2.000 2.000 2.000 2.000 2.000 2.000

R2 0.836 0.847 0.762 0.828 0.823 0.860 0.757

K(l3/g.min) 4.0E-05 4.43E-05 5.155E-05 3.305E-05 3.38E-05 6.322E-05 3.39E-05

Kf(l3/min) 1.5417E-19 1.5417E-19 1.5417E-19 1.5417E-19 1.5443E-19 1.5443E-19 1.5443E-19


p(g -1

) 7.1891E+14 5.746E+14 3.343E+14 4.2875E+14 4.3774E+14 8.1875E+14 4.309E+14

1/2(min) 36.23 32.72 28.11 43.85 42.88 22.92 42.75

(-r) 4.0-05Nt2

4.43E-05Nt2

5.155E-05Nt2

3.305E-05Nt2

3.38E-05Nt2

16.322E-05Nt2

3.39E-05Nt2

N0(g/l3) 317.6620 502.7652 444.1681 589.5531 815.8603 1097.3335 739.6450



T ABLE VII

COAG-FLOCCULATION KINETIC PARAMETERS AND LINEARREGRESSION COEFFICIENT OF COSC AT VARYING DOSAGE AND PH10


2.000 2.000 2.000 2.000 2.000 2.000 2.000

R2 0.743 0.827 0.848 0.866 0.84 0.922 0.967

K(l3/g.min) 4.4E-05 4.02E-05 5.741E-05 1.822E-05 1.60E-05 1.163E-05 2.90E-05

Kf(l3/min) 1.5622E-19 1.5647E-19 1.5647E-19 1.5647E-19 1.5673E-19 1.5673E-19 1.5673E-19

(acf)BR(l3/g.min) 8.8E-05 8.04E-05 1.1482E-05 3.644E-05 3.2E-05 2.326E-05 5.8E-05

p(g -1

) 5.6331E+14 5.1384E+14 7.3381E+13 2.3289E+14 2.0417E+14 1.4841E+14 3.7006E+14

1/2(min) 32.94 36.05 252.44 79.54 90.58 124.62 49.98

(-r) 4.4E-05Nt2

4.02E-05Nt2

85.741E-06Nt2

1.822E-05Nt2

1.60E-05Nt2

1.163E-05Nt2

2.90E-05Nt2

N0(glL3) 280.1905 440.1408 970.6853 931.0987 1018.0189 1399.5801 1310.6160

T ABLE VIII

COAG-FLOCCULATION KINETIC PARAMETERS AND LINEARREGRESSION COEFFICIENT OF COC AT VARYING DOSAGE ANDPH13


2.000 2.000 2.000 2.000 2.000 2.000 2.000

R2 0.490 0.324 0.579 0.621 0.626 0.881 0.904

K(l3/g.min) 2.7E-05 1.35E-05 1.050E-05 9089E-06 1.71E-06 4.518E-06 1.10E-06

KR(l3/min) 1.5647E-19 1.5647E-19 1.5647E-19 1.5673E-19 1.5673E-19 1.5673E-19 1.5673E-19


p(g -1

) 3.4511E+14 1.7256E+14 1.3421E+14 1.1598E+14 2.1821E+14 5.7653E+13 1.4037E+13

1/2(min) 40.26 80.52 103.52 119.58 635.65 240.48 988.14

(-r) 2.7E-05Nt2

1.35E-05Nt2

1.050E-06Nt2

9.089E-06Nt2

1.71E-06Nt2

4.518E-06Nt2

1.10E-06Nt2

N0(g/l3) 695.8941 758.7253 935.1038 1072.5011 1186.9436 1325.2054 1317.5231



Fig. 1. Representative rate Linear Plot of 1/TDSS Vs T ime for pH=7

Fig. 2. Plot of Efficiency (E%) Vs T ime for pH 1 and varying COSC dosages

Fig. 3. Plot of Efficiency (E%) Vs T ime For pH 3 and varying COSC dosages

00.00050.001

0.00150.002

0.00250.003

0.00350.004

0.00450.005

0 10 20 30 40 50

1/T

DSP

(l

/g)

Time (mins)

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l

0

10

20

30

40

50

60

70

2 4 6 10 20 30 40

Effi

cie

ncy

(E%

)

Time (mins)

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l

0

10

20

30

40

50

60

70

80

2 4 6 10 20 30 40

Effi

cie

ncy

(E%

)

Time (mins)

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l



Fig. 4. Plot of Efficiency Vs T ime for pH 5 and varying COSC dosages

Fig. 5. Plot of Efficiency (E%) Vs T ime for pH 7 and varying COSC dosages.


0

10

20

30

40

50

60

70

2 4 6 10 20 30 40

Effi

cie

ncy

(E%

)

Time (mins)

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l

0

10

20

30

40

50

60

70

80

90

2 4 6 10 20 30 40

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l

0

10

20

30

40

50

60

70

80

90

2 4 6 10 20 30 40

Effi

cie

ncy

(E%

)

Time (mins)

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l




Fig. 8. Plot of Efficiency (E%) Vs Dosage at 40mins

Fig. 9. Plot of Efficiency (E%) Vs pH at 40mins

0

10

20

30

40

50

60

70

80

2 4 6 10 20 30 40

Effi

cie

ncy

(E%

)

Time (mins)

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l

0

10

20

30

40

50

60

70

80

90

0.1 0.2 0.3 0.4 0.5 0.6 0.7

Effi

cie

ncy

(E%

)

Dosage (g/l)

pH=1

pH=3

pH=5

pH=7

pH=10

pH=13

0

10

20

30

40

50

60

70

80

90

1 3 5 7 10 13

Effi

cie

ncy

(E%

)

pH

0.1g/l

0.2g/l

0.3g/l

0.4g/l

0.5g/l

0.6g/l

0.7g/l



Fig. 10. Particle distribution plot as a function of time for minimum half life =0.38mins

Fig. 11. Particle distribution plot as a function of time for maximum half life=16.47mins

Fig. 12. Particles aggregation performance profile at 40mins and pH 7 for varying COSC and ALUM Dosages

0

200

400

600

800

1000

1200

1400

1600

1800

0 10 20 30 40 50

Par

ticl

e C

on

cen

trat

ion

(g/

l)

Time (mins)

Singlet

Doublet

Triplet

Sum

0

500

1000

1500

2000

2500

0 10 20 30 40 50

Par

ticl

e C

on

cen

trat

ion

(g/

l)

Time (mins)

Singlets

Doublets

Triplets

Sum

0

10

20

30

40

50

60

70

80

90

0.1g/l 0.2g/l 0.3g/l 0.4g/l 0.5g/l 0.6g/l 0.7g/l

COSC 81.59 70.87 81.59 74.06 69.57 84.2 79.13

ALUM 26.18 34 57.1 61.06 46.18 77.49 80

COSC

ALUM



4.0 RESULTS AND DISCUSSION

4.1 Characterization Results

These are presented in tables 1 and 2. From the

results in table 1, the pH value (3.87) obtained indicated that

the PIE is acidic which apparently resulted to the acidic odor

. This attributes suggest the presence of high level of

biological organisms (total viable count, total coliform count

etc) . In addition, the relatively high values of turbidity

(1256mg/l), biochemical oxygen demand (50mg/l) total

dissolved solids (225mg/l) total suspended solids

(57.25mg/l), respectively, show that the PIE has high

pollution potentials, providing a condition for this study.

The relatively high electrical conductivity value (490

µs/cm), indicates that the PIE sample contains charged ions,

suggesting that coagulation and flocculation treatment

method can be applied to this end. Also, levels of nutrients

(Ca, mg) and absence of heavy metal, implies that the PIE

can be recycled for agricultural purposes (as a soil

conditioner). In table 2, the presence of crude protein extract

from COSC, a water-soluble cationic peptide with

isoelectric point has been shown to be responsible for the

coagulating property inherent in it and other natural

coagulants of this type [11]. It can also be deduced from the

characterization results after treatment, though not shown,

that the acidic odor of PIE sample drastically reduced after

40mins of treatment. This is indication that COSC, has

antimicrobial effect too, in line with previous works

[4],[24].

4.2 Coag-flocculation functional parameters.

The values of coag-flocculation parameters generated from

the representative rate plot of 1/Nt (1/TDSS) vs time for

varying dosages and 40 mins settling time are presented in

tables 3 – 8. The squared linear regression coefficient R2

generated from figure 1, was employed to determine the

accuracy of fit of experimental results on the generalized

model equation 2.24. the values of R2 presented in tables 3 –

8 show that the experimental results obtained at PH 7 (table

6) were adequately described by the linearised form of

equation 2.22 (with R2 > 75), which was subsequently

expressed as equation 2.24 (putting = 2). Hence pH 7 is

the optimum, at the condition of this experiment . From the

graphical representation of equation 2.24 1/TDSS vs time

(figure 1), k is determined from the slope. However, K can

also be evaluated from the mathematical relation (K = 0.5

(acf)BR) expressed as equation 2.7 and posted in tables 3 – 8.

Also, tables 3 – 8, show that the maximum and minimum K

values are 6.322E-05l/g.min, 1.10 E-06 l/g .min obtained at

pH 7 (0.6g/l dose) and pH 13 (0.7 g/l dose) respectively.

This is in support of the fact that pH 7 is the optimum at the

condition of this experiment. This phenomenon indicates

that at high dosage more adsorption sites were made

available on the COSC interface for TDSS attachments and

subsequently leading to formation of inter particle bridges,

hence increasing the chances of COSC to initiate particle

sweep, though more effective at lower pH.

The value of 1/2 obtained from equation 2.29 and solved for

0.6g/l dosage (1/2 = 0.38 mins), confirms the authenticity of

the optimal value of K recorded at 0.6g/l dosage. The period

of 1/2 = 0.38min can be deduced from tables 3 – 8, as the

lowest, which is an indication of best coag-flocculation

performance at the corresponding dosage and pH .

Particularly, the results posted in table 6, show that high K

corresponds to the, least 1/2 obtained in this experiment, a

phenomenon that amplified a strong relationship among, K,

1/2 and rate of aggregation, which is in line with previous

work[19]. The optimal 1/2 (0.38mins) is relatively

satisfactory, though milliseconds had been reported.

Invariably, the optimum k value obtained at 0.6g/l dosage

from figure 1, is in agreement with the results presented in

table 6. The K, value is a very big determinant on the

efficacy of applying coag-flocculation process in water and

wastewater purifications.

Observation from equation 2.29, show that 1/2 is a function

of initial TDSS and K. The implication is that the higher the

No and K, the lesser the period. This explains the high

purification rate obtained in water and wastewater with high

initial TDSS load and high coagulation rate constant.(acf)BR

and Kf were obtained from equations 2.5 and 2.14

respectively. Kf is obtained on substitution of equations

2.11, 2.13 into 2.8.

Moreover, Kf = fn (T, ), and in this experiment there is

negligible change in the values of temperature and viscosity

of the effluent medium, consequently resulted to minimal

variations of Kf values as presented in tables 3 – 8. In the

vicinity near constant value of Kf, (acf)BR relates to k

proportionally, i.e 2K = (acf)BR expressed as equation 2.15).

Apparently, high (acf)BR result in high kinetic energy to

overcome the electrostatic barrier translating to fast

coagulation, generally, obtainable in practical terms in coag-

flocculation processes. From theoretical considerations, the

following parameters, (acf)BR, 1/2, and kf are understood to

be the prerequisite factors for coagulation efficiency prior to

flocculation.

Furthermore, the No determined from the model equation

expressed as equation 2.24 as the exponential value of the

intercept obtained from figure 1, though it did not follow

any observable trend. Finally, the mass transfer rate of

TDSS (dNt/dt or(-r) is evaluated from equation 2.22. This

accounts for the mass transfer of TDSS on the bio-coagulant

interface in PIE at varying dosages and pH. It is

understandable that more TDSS will be removed at the

maximum K value and lowest 1/2. Hence, high TDSS

depletion rate is a necessary condition for high K value and

low 1/2. In generally, the discrepancies observed in the

results of the kinetic parameters as presented in tables 3 – 8

may be attributed to the following:-

i. Unattainable assumptions; that there is perfect

homogeneity of PIE particles and COSC throughout

dispersion before particle aggregation [19],[26].

ii.The interplay between vander wall’s and hydrodynamic

instabilities which is capable of altering theoretical predicted

values.

iii.Coagulant dosage, low or high could have effect on the

results, because high coagulant dosage may results to

particle redispersion, leading to generation of outrageous



value. On the hand low dosage may result in the provision

of insufficient adsorption sites for TDSS attachments.

4.3 Effect of TDSS removal efficiency with settling

time.

This is a time dependent removal efficiency profile for

evaluating the effectiveness of given dosage of COSC at a

particular pH and settling time in removing TDSS from PIE.

The data obtained from efficiency relation expressed as

equation 2.37 are demonstrated in figures 2 – 9 (for 0.1 – 0.7

g/l doses, pH 1, 3, 5, 7, 10, 13 and settling time

2,4,6,10,20,30 and 40). The best performance is achieved at

0.1g/l, at the optimal pH 7 with initial TDSS of 1380 mg/l

reduced by 74.20% and 84.20% at the end of 2 and 40mins

settling time respectively. The least recorded E% > 69% for

all the dosage considered at pH 7, at the end of coag-

flocculation period of 40mins. This phenomenon indicate

the effectiveness of COSC to remove TDSS (in form of

turbidity) from the PIE neutral effluent condition after

maximum treatment period. It is also worthy to mention that

TDSS removal efficiency results shown in figures 6 and 7

are satisfactory for 0.1g/l COSC dose, pH 10 and 13

respectively at the end of 2 and 40mins coag-flocculation.

This establishes the fact that at the condition of the

experiment, COSC has also high potency in removing

turbidity from alkaline rich PIE medium.

4.4 Effect of TDSS removal efficiency with dosage.

This is presented in figure 8. It actually displayed how

dosage affected the TDSS removal efficiency from PIE

varying pH medium. Thus confirming the observations

made from figures 2 – 9. The significant feature of figure 8

show that increase in COSC dosage (0.1 – 0.7 g/l) has

negligible effect on the TDSS removal efficiency after

40mins for all the pH studied at the condition of the

experiment. The optimum performance is recorded at pH 7

for all dosages after maximum coag-flocculation interval.

Also, the level of performance achieved at pH of 10 and 13

are demonstrated. The results obtained indicate that the

turbidity removal efficiency values recorded after 40mins,

for all the dosages considered are impressive. The best

performance recorded at the optimal pH 7, suggest that the

effect of pH on TDSS removal efficiency is related to the

solubility of COSC in PIE sample, which apparently has

high degree of solubility (a measure of high degree of

protonation at the neutral region). Also, the satisfactory

performance recorded in the alkaline region might be

adduced to the greater affinity of cationic ions from the

COSC chain to react with hydroxyl ion from sodium

hydroxide to form stable hydroxide flocs which can also

serve as sorption site for TDSS in PIE. This can

subsequently be removed from the system via gravitational

principles. However, the performance exhibited by COSC at

0.1g/l can be adopted for effective treatment especially

when complete charge destabilization is not

required[5],[17].

4.5 Effect of TDSS removal Efficiency with PH.

This is presented in figure 9. It shows the performance of

various doses of COSC at varying effluent pH. Observation

from figure 9, indicate that maximum TDSS are recorded at

the optimal pH 7 for all doses, followed by pH of 10 and 13.

In general terms, it can be deduced that high doses of COSC

has insignificant affect on TDSS removal efficiency at the

condition of the experiment.

4.6 Time evolution of the cluster size distribution

On the substitution of K, values obtained from equation 2.24

into 2.30, the time evolution of particle aggregates (singlets,

doublets, triplets for m = 1,2,3, respectively) is predicted.

The graphical representation of the results obtained from

equation 2.30 in response to period of 1/2 = 0.38mins and

1/2 = 16.47 mins are shown in figures 10 and 11. In figure

10, the sum of particles (singlet, doublets, triplets) reached

the peak at 2 mins. The implication is that at 2 mins of coag

– flocculation process, there is maximum aggregation of

TDSS (made up of various class of particles). This

phenomenon could be attributed to the absence of zeta

potential between the particles, prevailing in a system where

attractive force dominates. However, at 2mins, the primary

particles (singlets) and sum of particles are seen to decrees

linearly downwards with respect to time. With the absence

of zeta potential among the particles (sum of particles and

singlets) at 2 mins, the COSC instantly sweeps away the

TDSS from the system[18],[21].Though there is little space

in between them indicating existence of minimal shear

force. On the other hand, the pair of doublets and triplets is

seen to aggregate at zero particle concentration at t = 0 (i.e

prior to coag-flocculation). However, at 30mins, the triplets

tends to infinity at zero particle concentration. This is an

evidence of high rate of coag-flocculation demonstrated at

low 1/2 of 0.38mins.

Figure 11, depicts a case where the values of the sum of

particles and singlets are close such that their variation with

time is near same. Also, a similar trend is exhibited by the

pair of doublets and triplets. The curves in figure 11,

indicate existence of wide space between the pairs of

particles, attributable to the wide margin difference in

concentration of particles between the pairs of (singlets and

sum) and (doublets and triplets). This phenomenon could be

linked to the existence of high shear force causing high

resistance to particle collision. It is worthy to mention that

this phenomenon applies to pair of the curves in figure 10

but not as pronounced as we have in figure 11.

4.7 Comparative TDSS Removal Efficiency (E%) of

COSC and Alum.

The coag-flocculation activities of COSC and alum

was compared at the same experimental conditions as

presented in figure 12, at the optimal pH of 7 and varying

doses 0.1 – 0.7 g/l. The results indicate that COSC

performed better than alum at the prevailing pH and all

dosages considered except dosage of 0.7g/l were alum

recorded a slightly higher performance value than COSC,

though comparable. It could be argued that the operating pH

is outside the optimal region of alum since alum is known to

perform best at alkaline range [6]. In addition, even at the

optimal pH domain of alum, though not shown, COSC

performed better than alum at all dosages except (0.1, 02

and 0.3) g/l. however, in the general analysis, it can be

deduced that the performance of COSC at pH 7 is better for



all doses, but comparable to that of alum for 0.6 – 0.7g/l

doses.

The major advantages of COSC over alum are the

production of low volume biodegradable sludge,

environmentally friendly, capable of achieving efficient

operation over a wide range of dosages, relatively cheap,

with simple preparation procedure.

5. CONCLUSION

Within the ambits of this experiment, the

generalized model equation 2.24 developed, significantly

predicts the coag-flocculation behavior of COSC at the

optimal pH. From the results, maximum settling time, high

dosage and pH(neutral region) had the most significant

effects on the process operation at the conditions of the

experiment. The computed experimental results agrees with

previous similar works [7],[14],[15][16],[28].

NOMENCLATURE

K: th order coag-flocculation constant

(acf)BR: Collision factor for Brownian Transport

εp: Collision Efficiency

1/2: Coagulation period/half life

Eij: Coag-flocculation Efficiency for i and j particles.

R2: Coefficient of Determination

: Coag-flocculation reaction order

-r: Coag-flocculation mass transfer rate

Biocoagulant: Corchorus Olitorus seed coagulant (COSC)

TDSS: Total dissolved and suspended solids.

Kf : Rate Constant for rapid Flocculation

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