166
R. Sundaram et al.
2.3 Optimization of Carbon Source, Temperature, pH
and Inoculum Concentration
Nitrate removal was evaluated under batch mode condition using 100 ml of synthetic
medium (MSM) (per litre containing 0.1 g of KH 2 PO 4 , 1 g of K 2 HPO 4 , 0.005 g
of CaCl 2 , 0.1 g of MgSO 4 , 0.05 g of Na 2 SiO 3 , pH 7 ± 0.2) supplemented with
100 mg/L of NO 3
− and 1% offive different carbon sources such as glucose, starch,
cellulose, sucrose and acetic acid. To this, 1 mL (10
4 CFU/mL) each of KW1 and of
YW4 (1:1 v/v) was aseptically addedand incubated for 48 h in a mechanical shaker
(120 rpm). The control was also maintained with the same concentration of NO 3
− but
without the bacterial inoculum. Every 6 h, the NO 3
− level was determined by phenol
disulphonic acid method (Rao 2000). Starchwas found to enhance theNO 3
− removal
and hence it was selected as a carbon source for further study. The above experiment
was repeatedsubsequently to find out the optimum conditions of temperature (among
25, 30, 35, 40 and 45 °C), pH (among 6, 7, 8 and 9), starch (among 0.2, 0.4, 0.6,
0.8, 1, 1.2 and 1.4%) and inoculum concentrations (among 1, 2, 3, 4 and 5%) for the
removal of NO 3
− in the synthetic medium.
2.4 Growth Kinetics of Nitrate Removal
To investigate the biodegradation kinetics of nitrate, several kinetic models have been
evaluated. The expression of substrate utilization in a batch reactor with respect to
time can be correlated by the first-order differential equation describes in Eq. (13.1).
−
d S
dt
= K sS
(13.1)
where, S is the substrate concentration (mg/l), Ks is the first order rate constant (h
−1 )
and t is the incubation time (h). Also, the Monod equation (Eq. 13.2) was applied for
nitrate biodegradation with different concentrations of starch, temperature, pH and
cell inoculum.
µ =
µmS
K s + S
(13.2)
where, µ m is the maximum specific degradation rate (h
−1 ), S is the substrate concentration (mg/l) and Ks is the Monod constant (mg/l). In some cases, the system disturbs
due to high concentration of inhibitory compounds. In this case, Haldane’s model
has a well-fitted model for determination of the kinetic parameters and it has the
similar form as described in Eq. (13.3).
µ =
µ max S
K s + S +
S 2
K i
(13.3)
R. Sundaram et al.
2.3 Optimization of Carbon Source, Temperature, pH
and Inoculum Concentration
Nitrate removal was evaluated under batch mode condition using 100 ml of synthetic
medium (MSM) (per litre containing 0.1 g of KH 2 PO 4 , 1 g of K 2 HPO 4 , 0.005 g
of CaCl 2 , 0.1 g of MgSO 4 , 0.05 g of Na 2 SiO 3 , pH 7 ± 0.2) supplemented with
100 mg/L of NO 3
− and 1% offive different carbon sources such as glucose, starch,
cellulose, sucrose and acetic acid. To this, 1 mL (10
4 CFU/mL) each of KW1 and of
YW4 (1:1 v/v) was aseptically addedand incubated for 48 h in a mechanical shaker
(120 rpm). The control was also maintained with the same concentration of NO 3
− but
without the bacterial inoculum. Every 6 h, the NO 3
− level was determined by phenol
disulphonic acid method (Rao 2000). Starchwas found to enhance theNO 3
− removal
and hence it was selected as a carbon source for further study. The above experiment
was repeatedsubsequently to find out the optimum conditions of temperature (among
25, 30, 35, 40 and 45 °C), pH (among 6, 7, 8 and 9), starch (among 0.2, 0.4, 0.6,
0.8, 1, 1.2 and 1.4%) and inoculum concentrations (among 1, 2, 3, 4 and 5%) for the
removal of NO 3
− in the synthetic medium.
2.4 Growth Kinetics of Nitrate Removal
To investigate the biodegradation kinetics of nitrate, several kinetic models have been
evaluated. The expression of substrate utilization in a batch reactor with respect to
time can be correlated by the first-order differential equation describes in Eq. (13.1).
−
d S
dt
= K sS
(13.1)
where, S is the substrate concentration (mg/l), Ks is the first order rate constant (h
−1 )
and t is the incubation time (h). Also, the Monod equation (Eq. 13.2) was applied for
nitrate biodegradation with different concentrations of starch, temperature, pH and
cell inoculum.
µ =
µmS
K s + S
(13.2)
where, µ m is the maximum specific degradation rate (h
−1 ), S is the substrate concentration (mg/l) and Ks is the Monod constant (mg/l). In some cases, the system disturbs
due to high concentration of inhibitory compounds. In this case, Haldane’s model
has a well-fitted model for determination of the kinetic parameters and it has the
similar form as described in Eq. (13.3).
µ =
µ max S
K s + S +
S 2
K i
(13.3)