One of the most important effective factors in the efficiency
of a reactor is the residence time of the reaction components.
Since biofilters are considered as biological reactors,
this parameter is also of great importance in biofilters. Residence
time alterations result from the changes in the flowrate
of the gas entering the column. Fig. 2 shows the outlet concentration
of toluene in the air stream and the removal efficiency
of the biofilter during the time of the experiments. In the first
three phases of experiment, the pollutant concentration was
adjusted to 173.1mgm−3. Besides, the gas flow rate was set to
0.096m3 h−1, 0.024m3 h−1 and also 0.06m3 h−1. Now that the
gas-biofilm contact time was low in the start-up phase, the
time of achieving steady-state condition was reached to 25
days. It is obvious that the increase in the gas residence time
in the biofilter would significantly cause greater decrease in
the amount of toluene in the outlet gas stream and greater
improvement in the RE during phase II, as many scientists
have observed (Maestre et al., 2007; Vergara-Fernandez et al.,
2007; Zand et al., 2007). It is also clear that at the flow rate of
0.024m3 h−1, the system would become stable in less than 10
days. When the air flowrate increased again up to 0.06m3 h−1,
the outlet concentrations increased consequently. However,
these concentrations are lower than what they are during the
phase I of Fig. 2. This happened because the residence time is
still more than what it was when the biofilter started to work.
Furthermore, microorganisms have completely adapted to the
contaminated air.
One of the most important effective factors in the efficiency
of a reactor is the residence time of the reaction components.
Since biofilters are considered as biological reactors,
this parameter is also of great importance in biofilters. Residence
time alterations result from the changes in the flowrate
of the gas entering the column. Fig. 2 shows the outlet concentration
of toluene in the air stream and the removal efficiency
of the biofilter during the time of the experiments. In the first
three phases of experiment, the pollutant concentration was
adjusted to 173.1mgm−3. Besides, the gas flow rate was set to
0.096m3 h−1, 0.024m3 h−1 and also 0.06m3 h−1. Now that the
gas-biofilm contact time was low in the start-up phase, the
time of achieving steady-state condition was reached to 25
days. It is obvious that the increase in the gas residence time
in the biofilter would significantly cause greater decrease in
the amount of toluene in the outlet gas stream and greater
improvement in the RE during phase II, as many scientists
have observed (Maestre et al., 2007; Vergara-Fernandez et al.,
2007; Zand et al., 2007). It is also clear that at the flow rate of
0.024m3 h−1, the system would become stable in less than 10
days. When the air flowrate increased again up to 0.06m3 h−1,
the outlet concentrations increased consequently. However,
these concentrations are lower than what they are during the
phase I of Fig. 2. This happened because the residence time is
still more than what it was when the biofilter started to work.
Furthermore, microorganisms have completely adapted to the
contaminated air.
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