Introduction and process description of FAB/MBBR

ByKETAN WADODKAR124180004

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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 tank27/04/23

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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). 27/04/23

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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.

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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.27/04/23

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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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