2.3 Advantage of Biofilm Process
15
substances also, without any trace of contamination into it. The physical and chemical stability of the biocatalyst can be improved by biofilm process with low power
input [30].
2.4 Aerobic Fixed-Bed Hybrid Bioreactor
Aerobic Hybrid bioreactor is the integrated biofilm activated sludge system, where
both suspended and attached-growth of biomass occur simultaneously. In fact, this
system adds the benefits of biofilm system into the suspended-growth activated sludge
process by inserting the biofilm surface into the aeration tank for cultivating the
biomass. Generally aerobic hybrid bioreactor is completely mixed system, where
proper mixing is provided for biomass suspension, substrate transfer and oxygen
diffusion. In the last few decades, hybrid bioreactor comprising of suspended- and
attached-growth biomass has been adopted widely for the treatment of wastewater
[24, 31, 32]. Integrated fixed-film activated sludge process was first developed in the
USA in 1980 where biofilm was inserted into the aeration tank [2, 3, 17].
2.4.1 Performance of Fixed-Bed Aerobic Hybrid Bioreactor
It was observed that the integrated-fixed film activated sludge (IFAS) system could
increase the effective MLSS in an aeration basin as much as 3000 mg/l. Rostron et al.
[33] conducted performance studies with different fixed film media under varying
input conditions. Combined activated sludge biofilm process was used for studying
the effect of solid retention time (SRT) and dissolved oxygen (DO) on chemical
oxygen demand (COD) [34]. It was observed that for efficient nitrogen removal,
SRT should be longer than 10 days. Later on, activated sludge biofilm system was
developed as a hybrid modification of existing ASP by inserting plastic nets vertically into the aeration tank [12–14], [35]. Hybrid bioreactor was also applied for
biological nutrient removal in industrial wastewater treatment [6, 36]. It was noticed
that attached biomass is superior to suspended-biomass for nitrifying wastewater
containing toxic organic compounds [37]. Rapid nitrification was performed by
employing macro-porous cellulose carrier for attachment of nitrifying bacteria [15].
Nitrification was also accomplished using chalk as a biomass carrier and for attaching
nitrifying biomass in a hybrid bioreactor [16]. Fibrous carriers were used in anoxic
zone in an aeration tank for enhancing the removal of nitrogen and phosphorus
[19]. Rutt et al. [5] reported one such case study on integrated fixed-film activated
sludge (IFAS) at Broomfield Coke oven Wastewater Treatment Plant (WWTP). A
laboratory-scale shaft-type aerobic hybrid bioreactor was investigated to check the
extent of removal of carbonaceous organic matter [38]. About 80% COD removal
was achieved at a HRT 8 h for an initial COD concentration between 1000 and
3500 mg/l. Hybrid bioreactor was used for studying the nutrients removal from
15
substances also, without any trace of contamination into it. The physical and chemical stability of the biocatalyst can be improved by biofilm process with low power
input [30].
2.4 Aerobic Fixed-Bed Hybrid Bioreactor
Aerobic Hybrid bioreactor is the integrated biofilm activated sludge system, where
both suspended and attached-growth of biomass occur simultaneously. In fact, this
system adds the benefits of biofilm system into the suspended-growth activated sludge
process by inserting the biofilm surface into the aeration tank for cultivating the
biomass. Generally aerobic hybrid bioreactor is completely mixed system, where
proper mixing is provided for biomass suspension, substrate transfer and oxygen
diffusion. In the last few decades, hybrid bioreactor comprising of suspended- and
attached-growth biomass has been adopted widely for the treatment of wastewater
[24, 31, 32]. Integrated fixed-film activated sludge process was first developed in the
USA in 1980 where biofilm was inserted into the aeration tank [2, 3, 17].
2.4.1 Performance of Fixed-Bed Aerobic Hybrid Bioreactor
It was observed that the integrated-fixed film activated sludge (IFAS) system could
increase the effective MLSS in an aeration basin as much as 3000 mg/l. Rostron et al.
[33] conducted performance studies with different fixed film media under varying
input conditions. Combined activated sludge biofilm process was used for studying
the effect of solid retention time (SRT) and dissolved oxygen (DO) on chemical
oxygen demand (COD) [34]. It was observed that for efficient nitrogen removal,
SRT should be longer than 10 days. Later on, activated sludge biofilm system was
developed as a hybrid modification of existing ASP by inserting plastic nets vertically into the aeration tank [12–14], [35]. Hybrid bioreactor was also applied for
biological nutrient removal in industrial wastewater treatment [6, 36]. It was noticed
that attached biomass is superior to suspended-biomass for nitrifying wastewater
containing toxic organic compounds [37]. Rapid nitrification was performed by
employing macro-porous cellulose carrier for attachment of nitrifying bacteria [15].
Nitrification was also accomplished using chalk as a biomass carrier and for attaching
nitrifying biomass in a hybrid bioreactor [16]. Fibrous carriers were used in anoxic
zone in an aeration tank for enhancing the removal of nitrogen and phosphorus
[19]. Rutt et al. [5] reported one such case study on integrated fixed-film activated
sludge (IFAS) at Broomfield Coke oven Wastewater Treatment Plant (WWTP). A
laboratory-scale shaft-type aerobic hybrid bioreactor was investigated to check the
extent of removal of carbonaceous organic matter [38]. About 80% COD removal
was achieved at a HRT 8 h for an initial COD concentration between 1000 and
3500 mg/l. Hybrid bioreactor was used for studying the nutrients removal from