Introduction and process description of FAB/MBBR
By
KETAN WADODKAR
124180004
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Content
MBBR (Moving Bed Biofilm Reactor) Introduction Process Description Design Consideration Advantages
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MBBR (Moving bed biofilm reactor) Small cylindrical shaped polyethylene carrier
added in aerated or non aerated basin to support biofilm growth.
Biomass grows primarily on protected surface on the inside of the carriers.
Air agitation or mixers are used to continuously circulate carriers.
Perforated plates at the outlet of the tanks keeps biofilm carrier inside the tank.
MBBR can be a single reactor or configured as several reactors-in-series.
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Fig: Moving Bed Biofilm Reactor (MBBR)
FAB Reactor / MBBR
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FAB REACTOR
RAW SEWAGE
AIR DISTRIBUTION GRID
AIR INLET PIPING
SPECIALLY DEVELOPEDCARRIER ELEMENTS
EFFLUENT OUTLETSYSTEM
TREATED SEWAGE
V V V V V
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Retention of the carrier within the reactor encourages selection and enrichment for organisms that are best adapted to the nutrient conditions that prevail in that reactor at steady state.
Carriers occupy 25-70% of tank volume.
The specific surface area of carrier is about 500m2/m3.
The carriers are slightly buoyant and have a specific gravity between 0.94 and 0.96 g/cm3.
Media carrier life is around 15-20 years.
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Various types of bio carriers used
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treatment capacity is a function of the specific surface area (SSA) of the reactor.
The SSA for a reactor = the quotient of the total surface area on the carrier that is available for biofilm establishment and the reactor volume.
TABLE: SSA of attached growth media (Source: Metcalf &eddy, 2003)
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Design Consideration Adequate preliminary treatment:
to prevent plastic biofilm carrier retention screen blinding
To prevent the accumulation of inert material in MBBR tank
Well designed aeration system: Promote the rolling water circulation pattern that
uniformly distributes plastic biofilm carriers throughout the MBBR.
diffused aeration is used for aerobic MBBR tank (Course bubble diffusion)
Typical oxygen transfer rates are 2.5 – 3.5 % per meter of water submergence.
Typical air flow rate = 6 to 8 m3/m2.h.
Properly specified/designed mechanical mixers for denitrification tank
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Fig: Influence of organic load and reactor DO concentration on TAN removal in a Kaldnes MBBR, at 15 C and with TAN in excess (2.5 mg N/L). (Hem et al. 1994). 12/04/23
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Media carrier retention screens: Scum must be removed from the system
Typical screen design allows for a maximum 50 to 150mm head loss
Effective liquid–solid separation system: The general SS in MBBR effluent found out to be 150-
250 mg/L, when treating medium to high strength wastewaters.
MBBR are low HRT biofilm reactors
According to Ahl et al. (2006), the particle size distribution shifts towards larger particle size with increase in HRT.
As biomass accumulation is settling independent, MBBR is flexible in choice of settler used. (Coagulation & flocculation. Tube settler, MF/UF etc.)
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Length-to-width ratio (L:W) in the range 0.5:1 to 1.5:1.
Ratio more than above results in non uniform distribution of bio carriers.
Biofilm thickness is controlled by air flow or mechanical mixing energy.
Low-rate MBBRs promote nitrification.
Medium-rate MBBRs typically are designed for an OLR in the range 5 to 10 g BOD5/m2 .d (at 10uC).
Higher-rate systems require chemically enhanced liquid–solids separation and/or flotation. OLR = 45-60 g BOD5/m2d @25 oC. (Ødegaard, 2006).
MBBR support SNDN which is dependant on type of carrier selected.
It do no require any return activated sludge or backwashing. 12/04/23
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Advantages: High-efficiency cBOD removal and nitrification
(even in low temperature environments)
Retention of slow-growing and temperature-sensitive bacterial populations (i.e., autotrophic nitrifiers and methanol-degrading heterotrophs, respectively)
low HRT
high biomass concentration
low solids loading on liquid–solids separation unit processes
Reduced sludge production compared with activated sludge
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No problems with odours, snails or red-worms as in air phase fixed films.
Non clogging design. Is a continuous system and
biofilm thickness is maintained by the aeration-mixing process.
Smaller foot prints. MBBR Provides Five times
the Biofilm Surface Area in less than ¼ Reactor Volume as Trickling Filter
Can be operated at varying influent load
Can be easily retrofitted.12/04/23
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References McQuarrie J. P., Boltz J. P. (2011) Moving Bed Biofilm Reactor
Technology: Process Applications, Design, and Performance; Water Environment Research, London, United Kingdom, 83 (6), page no. 560-575.
Ødegaard, H. (2006) Innovations in Wastewater Treatment: The Moving Bed Biofilm Process. Water Sci. Technol., 53 (9), 7–33.
Hem, L.J., Rusten, B., Ødegaard, H., 1994. Nitrification in a moving bed biofilm reactor. Water Res. 28 (6), 1425–1433.
www.Wikipedia.org
www.anoxkaldnes.com
www.headworksusa.com
www.thermaxindia.com
Metcalf and Eddy (2003), Wastewater Engineering: Treatment and Reuse, 4th Edition, TATA McGraw-Hill, New Delhi.
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