2
1 Introduction
Although the integrated fixed-film activated sludge system was first developed
in the USA in 1980, a long time back, there is a very few research work done so
far in the development of mathematical model considering the concurrent growth
of both suspended biomass and attached biomass, which is required for the process
design of the hybrid bioreactor. This is because the biological reactions involving
the conversion of the substrates by both suspended- and attached-growth biomass in
a concurrent way are highly complex and especially the solution of biofilm model is
much more tedious and cumbersome compared to that of suspended-growth process.
Even where the competition for rate-limiting substrates between two growths (both
suspended and attached) was simultaneously considered, no unique accurate and
simplified solution was derived from the steady-state substrate mass balance and
biomass balance equations.
A simplified mathematical model (with computer programming and excel worksheet) for fixed-bed hybrid bioreactor thus finds its relevance for predicting the reliable outputs for the sake of process design of the reactor. Accordingly, a simplified
model of an aerobic hybrid bioreactor is developed considering simultaneous growth
of both the suspended and attached biomass in a competitive manner. The model is
based on steady-state carbonaceous substrate as well as biomass mass balance for
both suspended and attached growths along with substrate mass transport into the
biofilm. The analytical solution involved determination of the average flux along
with exiting substrate concentration and determination of effective biofilm thickness
by Runge–Kutta method. A computer program is developed in Fortran language
and the model has been validated with both the existing methods of standard literatures and the experimental results. Monod kinetic relationship is used in the present
model considering no inhibition in remaining carbonaceous organic matter from the
municipal wastewater.
1.2 Historical Findings
Integrated film activated sludge process was first developed in the USA in 1980,
where biofilm was inserted into the aeration tank [1, 2]. There are two types of
attached media entrapped in the aeration tank like “dispersed media,” i.e., movable
type and “fixed media,” i.e., sheet media or fabric media fixed in place in the aeration
tank. IFAS technology provides for additional biomass within a wastewater treatment
facility in order to meet more stringent effluent discharge standard or increased
organic loadings without the direct need for additional tank [3]. The hybrid bioreactor
process was applied as a retrofitting of the existing ASP system without expanding
the volume of the reactor. Hybrid bioreactor technology has been incorporated into
municipal and industrial wastewater facilities for upgrading or retrofitting plants in
many variations of suspended-growth systems. In case of upgraded plants, additional
treatment capacity can be obtained without increasing the volume of the existing tank.
The secondary treatment processes were upgraded to integrated fixed-film activated
1 Introduction
Although the integrated fixed-film activated sludge system was first developed
in the USA in 1980, a long time back, there is a very few research work done so
far in the development of mathematical model considering the concurrent growth
of both suspended biomass and attached biomass, which is required for the process
design of the hybrid bioreactor. This is because the biological reactions involving
the conversion of the substrates by both suspended- and attached-growth biomass in
a concurrent way are highly complex and especially the solution of biofilm model is
much more tedious and cumbersome compared to that of suspended-growth process.
Even where the competition for rate-limiting substrates between two growths (both
suspended and attached) was simultaneously considered, no unique accurate and
simplified solution was derived from the steady-state substrate mass balance and
biomass balance equations.
A simplified mathematical model (with computer programming and excel worksheet) for fixed-bed hybrid bioreactor thus finds its relevance for predicting the reliable outputs for the sake of process design of the reactor. Accordingly, a simplified
model of an aerobic hybrid bioreactor is developed considering simultaneous growth
of both the suspended and attached biomass in a competitive manner. The model is
based on steady-state carbonaceous substrate as well as biomass mass balance for
both suspended and attached growths along with substrate mass transport into the
biofilm. The analytical solution involved determination of the average flux along
with exiting substrate concentration and determination of effective biofilm thickness
by Runge–Kutta method. A computer program is developed in Fortran language
and the model has been validated with both the existing methods of standard literatures and the experimental results. Monod kinetic relationship is used in the present
model considering no inhibition in remaining carbonaceous organic matter from the
municipal wastewater.
1.2 Historical Findings
Integrated film activated sludge process was first developed in the USA in 1980,
where biofilm was inserted into the aeration tank [1, 2]. There are two types of
attached media entrapped in the aeration tank like “dispersed media,” i.e., movable
type and “fixed media,” i.e., sheet media or fabric media fixed in place in the aeration
tank. IFAS technology provides for additional biomass within a wastewater treatment
facility in order to meet more stringent effluent discharge standard or increased
organic loadings without the direct need for additional tank [3]. The hybrid bioreactor
process was applied as a retrofitting of the existing ASP system without expanding
the volume of the reactor. Hybrid bioreactor technology has been incorporated into
municipal and industrial wastewater facilities for upgrading or retrofitting plants in
many variations of suspended-growth systems. In case of upgraded plants, additional
treatment capacity can be obtained without increasing the volume of the existing tank.
The secondary treatment processes were upgraded to integrated fixed-film activated