2.6 Treatability of Municipal Wastewater
29
Hydraulic and Environmental Engineering at the Norwegian University of Science
and Technology in Trondheim. The experiment was performed in two phases. The
pilot plant was first operated with a constant hydraulic retention time (HRT) of 4.5 h,
while in the second phase the influent flow was increased so that HRT became 3.5 h.
The average temperature was maintained near 11.5 °C in the overall experimental
campaign. The average mixed liquor SRT was maintained 5.7 days. The results
revealed that this kind of reactor can efficiently be used for the upgrading of conventional activated sludge plant for achieving a good quality of effluent [88]. Sriwiriyarat
et al. [83] also made his research study treating a week municipal wastewater with
IFAS using sponge media at different aerobic mean cell residence times for evaluating
his model performance with the experimental data and found satisfactory results in
removal of carbonaceous organic matter and nitrification.
2.7 Present and Future Prospect of Aerobic Hybrid
Bioreactor System
Although there are a few mathematical models on fixed-bed hybrid bioreactor, no
attempt has been made till 2014 toward its process design. There is a future scope in
research work for exploring this issue and for proposing a mechanism for the process
design of fixed-bed hybrid bioreactor. The process design of hybrid bioreactor is
necessary to find out its volume, physical dimension and other operational requirements including oxygen for any targeted effluent substrate concentration. Besides
this, it may be aimed to calculate the solid retention time (θ c ), average substrate
flux into the biofilm (J avg ) and effective as well as total biofilm thickness. There
must have certain design criteria, which can be checked accordingly for any physical
configuration adopted for the reactor.
Determination of kinetic coefficients for the suspended and the attached biomass
is extremely required to predict the performance of a fixed-bed hybrid bioreactor.
Since these two types of microorganisms are reciprocal to each other, their nature may
be assumed almost same. However, there are additional parameters like coefficient
of shear loss and decay, which make the hybrid bioreactor model very complex
to analyze. The issue of determining the kinetic coefficients was pending over a
long time. There is a scope of future research work for exploring this problem and
for suggesting a rational mechanism for evaluating the kinetic coefficients in the
fixed-bed hybrid bioreactor.
In earlier research, it was observed that effective diffusivities in aerobic biofilm
have a significant role to determine whether a section of the biofilm becomes depleted
of substrate or dissolved oxygen, thereby rendering that section ineffective, anoxic
or anaerobic [89]. Therefore, extent of diffusion through the biofilm needs to be
estimated for ascertaining its actual status.
It has been further established earlier that three sets of indicators like biomass
partitions (i.e., the proportions of biomass each in suspended and attached growth),
29
Hydraulic and Environmental Engineering at the Norwegian University of Science
and Technology in Trondheim. The experiment was performed in two phases. The
pilot plant was first operated with a constant hydraulic retention time (HRT) of 4.5 h,
while in the second phase the influent flow was increased so that HRT became 3.5 h.
The average temperature was maintained near 11.5 °C in the overall experimental
campaign. The average mixed liquor SRT was maintained 5.7 days. The results
revealed that this kind of reactor can efficiently be used for the upgrading of conventional activated sludge plant for achieving a good quality of effluent [88]. Sriwiriyarat
et al. [83] also made his research study treating a week municipal wastewater with
IFAS using sponge media at different aerobic mean cell residence times for evaluating
his model performance with the experimental data and found satisfactory results in
removal of carbonaceous organic matter and nitrification.
2.7 Present and Future Prospect of Aerobic Hybrid
Bioreactor System
Although there are a few mathematical models on fixed-bed hybrid bioreactor, no
attempt has been made till 2014 toward its process design. There is a future scope in
research work for exploring this issue and for proposing a mechanism for the process
design of fixed-bed hybrid bioreactor. The process design of hybrid bioreactor is
necessary to find out its volume, physical dimension and other operational requirements including oxygen for any targeted effluent substrate concentration. Besides
this, it may be aimed to calculate the solid retention time (θ c ), average substrate
flux into the biofilm (J avg ) and effective as well as total biofilm thickness. There
must have certain design criteria, which can be checked accordingly for any physical
configuration adopted for the reactor.
Determination of kinetic coefficients for the suspended and the attached biomass
is extremely required to predict the performance of a fixed-bed hybrid bioreactor.
Since these two types of microorganisms are reciprocal to each other, their nature may
be assumed almost same. However, there are additional parameters like coefficient
of shear loss and decay, which make the hybrid bioreactor model very complex
to analyze. The issue of determining the kinetic coefficients was pending over a
long time. There is a scope of future research work for exploring this problem and
for suggesting a rational mechanism for evaluating the kinetic coefficients in the
fixed-bed hybrid bioreactor.
In earlier research, it was observed that effective diffusivities in aerobic biofilm
have a significant role to determine whether a section of the biofilm becomes depleted
of substrate or dissolved oxygen, thereby rendering that section ineffective, anoxic
or anaerobic [89]. Therefore, extent of diffusion through the biofilm needs to be
estimated for ascertaining its actual status.
It has been further established earlier that three sets of indicators like biomass
partitions (i.e., the proportions of biomass each in suspended and attached growth),