2.1 Limitations of Activated Sludge Process
11
conventional activated sludge process and are designated as refractory or recalcitrant.
Presence of recalcitrant compounds and high concentration of total dissolved inorganic solids associated with low BOD/COD ratio (<0.35) of wastewater is generally
considered as complex or slowly biodegradable. There is always inhibitory effect of
those substances in biological treatment of wastewater.
2.1.6 High Energy Requirement During Operation
In traditional ASP, biomass is maintained through extended aeration system with
necessary recirculation ratio, which increases the pumping cost. As the biomass are
susceptible to wash out, concentrated return activated sludge needs to be recirculated
to the aeration tank, resulting in high power input toward pumping.
2.2 Efforts Made on Upgradation of Activated Sludge
Process
Integrated film activated sludge process was first developed in the USA in 1980,
where biofilm was inserted into the aeration tank [2, 3]. Hybrid bioreactor is mainly
of two types: “dispersed media,” i.e., movable type biofilm entrapped in the aeration
tank and “fixed media,” i.e., sheet media or fabric media fixed in place in the aeration
tank. The later one is said to be IFAS technology, which provides for additional
biomass within a wastewater treatment facility in order to meet more stringent effluent
discharge standard or increased organic loading without the direct need for additional
tank [4].
Dispersed biofilm media in case of hybrid bioreactor with movable biofilm are
suspended by the flow induced by the aeration system. Fine bubble diffusers are used
for aeration in case of fixed film hybrid bioreactor and coarse ones are used in case
of movable film hybrid bioreactor.
The technology of hybrid bioreactor system can be 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 process
was upgraded to integrated fixed-film activated sludge process by adding the media
into its existing basin in Broomfield wastewater treatment plant for improving the
biological nutrient removal process [5]. A municipal ASP treating domestic wastewater was upgraded by the incorporation of synthetic looped cord media supporting
fixed biofilm growth at Harbor road WWTP, Florida. The plant was upgraded to IFAS
system to meet the effluent quality in terms of unionized ammonia of 0.02 mg/l for
11
conventional activated sludge process and are designated as refractory or recalcitrant.
Presence of recalcitrant compounds and high concentration of total dissolved inorganic solids associated with low BOD/COD ratio (<0.35) of wastewater is generally
considered as complex or slowly biodegradable. There is always inhibitory effect of
those substances in biological treatment of wastewater.
2.1.6 High Energy Requirement During Operation
In traditional ASP, biomass is maintained through extended aeration system with
necessary recirculation ratio, which increases the pumping cost. As the biomass are
susceptible to wash out, concentrated return activated sludge needs to be recirculated
to the aeration tank, resulting in high power input toward pumping.
2.2 Efforts Made on Upgradation of Activated Sludge
Process
Integrated film activated sludge process was first developed in the USA in 1980,
where biofilm was inserted into the aeration tank [2, 3]. Hybrid bioreactor is mainly
of two types: “dispersed media,” i.e., movable type biofilm entrapped in the aeration
tank and “fixed media,” i.e., sheet media or fabric media fixed in place in the aeration
tank. The later one is said to be IFAS technology, which provides for additional
biomass within a wastewater treatment facility in order to meet more stringent effluent
discharge standard or increased organic loading without the direct need for additional
tank [4].
Dispersed biofilm media in case of hybrid bioreactor with movable biofilm are
suspended by the flow induced by the aeration system. Fine bubble diffusers are used
for aeration in case of fixed film hybrid bioreactor and coarse ones are used in case
of movable film hybrid bioreactor.
The technology of hybrid bioreactor system can be 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 process
was upgraded to integrated fixed-film activated sludge process by adding the media
into its existing basin in Broomfield wastewater treatment plant for improving the
biological nutrient removal process [5]. A municipal ASP treating domestic wastewater was upgraded by the incorporation of synthetic looped cord media supporting
fixed biofilm growth at Harbor road WWTP, Florida. The plant was upgraded to IFAS
system to meet the effluent quality in terms of unionized ammonia of 0.02 mg/l for