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Content MBBR (Moving Bed BiofilmReactor) Introduction Process Description Design Consideration Advantages16/06/132
MBBR (Moving bed biofilmreactor) Small cylindrical shaped polyethylene carrieradded in aerated or non aerated basin tosupport biofilm growth. Biomass grows primarily on protected surface onthe inside of the carriers. Air agitation or mixers are used to continuouslycirculate carriers. Perforated plates at the outlet of the tanks keepsbiofilm carrier inside the tank. MBBR can be a single reactor or configured asseveral reactors-in-series.16/06/133
16/06/134Fig: Moving Bed Biofilm Reactor (MBBR)
FAB Reactor / MBBR16/06/135FAB REACTORRAW SEWAGEAIR DISTRIBUTION GRIDAIR INLET PIPINGSPECIALLY DEVELOPEDCARRIER ELEMENTSEFFLUENT OUTLETSYSTEMTREATEDSEWAGEV V V V V
Retention of the carrier withinthe reactor encouragesselection and enrichment fororganisms that are bestadapted to the nutrientconditions that prevail in thatreactor at steady state. Carriers occupy 25-70% oftank volume. The specific surface area ofcarrier is about 500m2/m3. The carriers are slightlybuoyant and have a specificgravity between 0.94 and 0.96g/cm3. Media carrier life is around 15-20 years.16/06/138
treatment capacity is a function of the specific surfacearea (SSA) of the reactor. The SSA for a reactor = the quotient of the total surfacearea on the carrier that is available for biofilmestablishment and the reactor volume.TABLE: SSA of attached growth media (Source: Metcalf&eddy, 2003)16/06/1310
Design Consideration Adequate preliminary treatment: to prevent plastic biofilm carrier retention screen blinding To prevent the accumulation of inert material in MBBRtank Well designed aeration system: Promote the rolling water circulation pattern thatuniformly distributes plastic biofilm carriers throughout theMBBR. diffused aeration is used for aerobic MBBR tank (Coursebubble diffusion) Typical oxygen transfer rates are 2.5 – 3.5 % per meter ofwater submergence. Typical air flow rate = 6 to 8 m3/m2.h. Properly specified/designed mechanical mixers fordenitrification tank 16/06/1311
Fig: Influence of organic load and reactor DO concentration onTAN removal in a Kaldnes MBBR, at 15 C and with TAN in excess (2.5mg N/L). (Hem et al. 1994). 16/06/1312
Media carrier retention screens: Scum must be removed from the system Typical screen design allows for a maximum 50 to150mm head loss Effective liquid–solid separation system: The general SS in MBBR effluent found out to be 150-250mg/L, when treating medium to high strengthwastewaters. MBBR are low HRT biofilm reactors According to Ahl et al. (2006), the particle sizedistribution shifts towards larger particle size withincrease in HRT. As biomass accumulation is settling independent, MBBRis flexible in choice of settler used. (Coagulation &flocculation. Tube settler, MF/UF etc.)16/06/1313
Length-to-width ratio (L:W) in the range 0.5:1 to 1.5:1. Ratio more than above results in non uniformdistribution of bio carriers. Biofilm thickness is controlled by air flow ormechanical mixing energy. Low-rate MBBRs promote nitrification. Medium-rate MBBRs typically are designed for anOLR in the range 5 to 10 g BOD5/m2.d (at 10uC). Higher-rate systems require chemically enhancedliquid–solids separation and/or flotation. OLR = 45-60g BOD5/m2d @25 oC. (Ødegaard, 2006). MBBR support SNDN which is dependant on type ofcarrier selected. It do no require any return activated sludge orbackwashing.16/06/1314
Advantages: High-efficiency cBOD removal and nitrification(even in low temperature environments) Retention of slow-growing and temperature-sensitive bacterial populations (i.e., autotrophicnitrifiers and methanol-degrading heterotrophs,respectively) low HRT high biomass concentration low solids loading on liquid–solids separation unitprocesses Reduced sludge production compared withactivated sludge16/06/1315
No problems with odours,snails or red-worms as in airphase fixed films. Non clogging design. Is a continuous system andbiofilm thickness is maintainedby the aeration-mixingprocess. Smaller foot prints. MBBR Provides Five times theBiofilm Surface Area in lessthan ¼ Reactor Volume asTrickling Filter Can be operated at varyinginfluent load Can be easily retrofitted.16/06/1316
References McQuarrie J. P., Boltz J. P. (2011) Moving Bed Biofilm ReactorTechnology: Process Applications, Design, and Performance;Water Environment Research, London, United Kingdom, 83 (6),page no. 560-575. Ødegaard, H. (2006) Innovations in Wastewater Treatment: TheMoving Bed Biofilm Process. Water Sci. Technol., 53 (9), 7–33. Hem, L.J., Rusten, B., Ødegaard, H., 1994. Nitrification in amoving 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: Treatmentand Reuse, 4thEdition, TATA McGraw-Hill, New Delhi.16/06/1317