28
2 Advantages of Hybrid Bioreactor
ammonia. It received influent into three compartments and effluent only from another
compartment, which followed the timing cycle sequence [86].
Activated sludge process including conventional, extended aeration and contact
stabilization was applied in pilot-scale study for six months in Isfahan South Municipal WWTP. COD removal efficiency was found between 83 and 92.5%, between
88 and 93.8%, and between 77 and 92% for conventional process, extended aeration
and contact stabilization, respectively [87].
2.6.3 Past experience on treatment of municipal wastewater
in aerobic hybrid bioreactor
The hybrid bioreactor process has significantly improved the efficiency of biological treatment of slowly biodegradable substance and has been widely applied to
municipal wastewater treatment in recent years. Hybrid bioreactor technology has
been incorporated into municipal wastewater facilities for both new plant installation and upgradation/retrofitting of the overloaded plants in many variations. In
case of new plant installation, the reactor volume gets reduced due to additional
attached biomass. For the plant upgradation, enhanced treatment capacity can be
obtained without increasing the volume of the existing tank. Hybrid bioreactor was
used for studying the nutrients removal from municipal wastewater [39]. It was found
that the hybrid bioreactor ensured a better removal than the purely attached biofilm
system. IFAS process was also installed at Maryland municipal wastewater reclamation facility, where rope-like ringlace IFAS media of 30000 m were installed in
a volume of 475 cum. Nitrification in the IFAS section was found more than three
times that in the control section without media [24]. A sponge type IFAS media
was used at Moundsville wastewater treatment plant, USA in three years of fullscale operation. This is a combined suspended- and attached-growth process where
polyurethane foam media was incorporated into ASP process increasing the equivalent MLSS concentration level. The attached and suspended MLSS were maintained
between 6500–12,000 mg/l and 900–1700 mg/l, respectively.
The efficiency in removal of BOD, nitrification and denitrification was found
95%, 70–90% and 40–60%, respectively, at a HRT 50–90 min [8].
A study was conducted to see the effect of attached biomass on the filamentous
growth of suspended biomass in the nitrification process and found that nitrification became independent of SRT of suspended biomass, since nitrifying bacteria
are predominantly attached to the support materials. In this case, dispersed plastic
foam particles and fully submersed plastic disks were used as a supporting media for
attached biomass [9]. In a cold region, treatment of domestic wastewater was done by
a hybrid activated sludge/biofilm process, which contained both suspended biomass
and biofilm, usually referred as integrated fixed-film activated sludge (IFAS) process,
created by introducing plastic elements as biofilm carrier media into a conventional
activated sludge reactor. Pilot-scale study was carried out at the Department of
2 Advantages of Hybrid Bioreactor
ammonia. It received influent into three compartments and effluent only from another
compartment, which followed the timing cycle sequence [86].
Activated sludge process including conventional, extended aeration and contact
stabilization was applied in pilot-scale study for six months in Isfahan South Municipal WWTP. COD removal efficiency was found between 83 and 92.5%, between
88 and 93.8%, and between 77 and 92% for conventional process, extended aeration
and contact stabilization, respectively [87].
2.6.3 Past experience on treatment of municipal wastewater
in aerobic hybrid bioreactor
The hybrid bioreactor process has significantly improved the efficiency of biological treatment of slowly biodegradable substance and has been widely applied to
municipal wastewater treatment in recent years. Hybrid bioreactor technology has
been incorporated into municipal wastewater facilities for both new plant installation and upgradation/retrofitting of the overloaded plants in many variations. In
case of new plant installation, the reactor volume gets reduced due to additional
attached biomass. For the plant upgradation, enhanced treatment capacity can be
obtained without increasing the volume of the existing tank. Hybrid bioreactor was
used for studying the nutrients removal from municipal wastewater [39]. It was found
that the hybrid bioreactor ensured a better removal than the purely attached biofilm
system. IFAS process was also installed at Maryland municipal wastewater reclamation facility, where rope-like ringlace IFAS media of 30000 m were installed in
a volume of 475 cum. Nitrification in the IFAS section was found more than three
times that in the control section without media [24]. A sponge type IFAS media
was used at Moundsville wastewater treatment plant, USA in three years of fullscale operation. This is a combined suspended- and attached-growth process where
polyurethane foam media was incorporated into ASP process increasing the equivalent MLSS concentration level. The attached and suspended MLSS were maintained
between 6500–12,000 mg/l and 900–1700 mg/l, respectively.
The efficiency in removal of BOD, nitrification and denitrification was found
95%, 70–90% and 40–60%, respectively, at a HRT 50–90 min [8].
A study was conducted to see the effect of attached biomass on the filamentous
growth of suspended biomass in the nitrification process and found that nitrification became independent of SRT of suspended biomass, since nitrifying bacteria
are predominantly attached to the support materials. In this case, dispersed plastic
foam particles and fully submersed plastic disks were used as a supporting media for
attached biomass [9]. In a cold region, treatment of domestic wastewater was done by
a hybrid activated sludge/biofilm process, which contained both suspended biomass
and biofilm, usually referred as integrated fixed-film activated sludge (IFAS) process,
created by introducing plastic elements as biofilm carrier media into a conventional
activated sludge reactor. Pilot-scale study was carried out at the Department of