Comparison of SBR and MBBR technology

Though there exists no direct comparison between MBBR and SBR due to different process mechanism, both technologies can be compared on the basis of following points.

SBR is a variant variant of Conventional Conventional Activated Activated Sludge Sludge system system based on suspended suspended growth principle. In conventional activated sludge system the treatment steps of  biological reaction and clarification are carried out in separate tanks on continuous basis while in SBR all the treatment steps are carried out in the same reactor in a timed sequence. Thus, SBR is an activated sludge system which operates on time rather than space sequence. While MBBR is a unique process in which combines suspended as well as attached growt growth h princi principle ples s of biolog biologica icall waste wastewat water er treatm treatment ent.. In the MBBR MBBR syste system m the biomass responsible for the removal of organic matter from the wastewater is held in suspension as well as on the bio carriers provided in the reactor as fixed film. Thus, MBBR provides an unique combination of advantages provided by both activated sludge system system as well as fixed film system and and at the same time trying to minimize the drawbacks of both the systems. The reactor conditions within the MBBR promotes a highly specialized biomass that is well well suit suited ed to cond condit ition ions s in the the reac reacto torr to meet meet the the desi desire red d treat treatme ment nt goal goals s resulting in higher volumetric efficiency and increase process stability providing a compact system. In case of SBR the settling and decanting phase is very much important for the separation of active biomass from the clarified liquid and thus biological performance is dependent upon the solids separation achieved during settling and decanting phase. phase. While in case of MBBR the active biomass biomass is continuous continuously ly retained retained in the reactor in suspension as well as on biofilm established on the carriers and thus biological performance is independent of solids separations. Moreover, in SBR there is a requirement to maintain a Sludge Retention Time (SRT) to allow the active biomass to remain in the reactor to achieve desired treatment goals while in case of MBBR no such SRT maintenance required and thus process operation is much simpler than SBR and can be operated and maintained with much ease than SBR systems. Moreover, the SRT is a temperature and other process parameters dependent variable which require time to time monitoring as well as adjustment while operating SBR at optimum conditions but in case of MBBR no such adjustment is required. The SBR is susceptible to shock loads and the process stability can be disturbed due to toxic pollutants as the reactor is completely mixed. However, in case of MBBR the bio carrier acts as a sink in the event of shock loading and absorb the toxic pollutant on it which would eventually will be degraded by the micro organisms on it. Considering the requirement for a BOD/COD removal plant, the MBBR system offers quite space saving compared to SBR system. Fo, BOD removal , an SBR system operated at 6 days nominal SRT requires approximately 620 m3 of reactor volume while in case of MBBR the total volumetric requirement would be 200m3 for reactor  volume and approximately 200 m3 for secondary clarifier (depending upon design).

Thus, in this particular case of 1 MLD STP for BOD/COD removal MBBR would offer  approximately 1/3 space saving compared to SBR unit. The operation of the MBBR is much more simpler as mentioned earlier while in case of SBR a robust automatic process control required and this should be flexible enough to adjust the variation in temperature and COD/BOD loading. The decanting system in the SBR system requires special attention and maintenance due to involvement of mechanical system while in MBBR no such mechanical system required. Due to specific operational advantages of fixed film technology,MBBR generates less sludge compared to SBR which is based on activated sludge system. Moreover, in case of SBR a portion of cycle is dedicated for settling and decanting. During this time the aeration is shut off and no biological reaction takes place during this period. Due to this inherent process requirement, the effective aeration time is less with SBR technology compared to MBBR which is a continuous process and aeration is taking place on continuous basis. Thus, the volumetric requirement of air  would be higher in case of SBR recurring higher power consumption for a particular  installation. The proposed 1 MLD STP based on MBBR technology has been designed considering a specialized bio carrier manufactured by Levapor Biofilm Technologies and Bio Consulting GmbH, Leverkusen, Germany. The bio carrier is first synthetically modified bio carrier based on Poly Urethane material compared to Poly Ethylene material used by other types of bio carrier. The highly porous, high performance LEVAPOR bio carrier is developed from high porosity poly urethane foam impregnated with surface activated pigments which increases the surface area of the bio carrier to many folds. The distinct properties of  LEVAPOR bio carrier and their benefits are summarised as below:

PROPERTIES

Higher adsorbing surface Highly porous with high internal porosity Fast wetting and water binding Higher surface area Higher fluidization ability Faster colonization of bacterial mass with higher surface

The above mentioned properties result in following benefits making LEVAPOR the most efficient bio carrier in the industry. • • • • • • • •

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Reversible adsorption of inhibitory, slowly degradable pollutants and Colonisation of carrier surface by more active, special, biofilm forming microorganisms than simple carriers resulting in faster process startup higher removal efficiency higher process stability lower sludge yields and better process economy. Lower degree of reactor filling (12 to 15%) required compared to plastic carrier  Fine bubble aeration system can be utilised in the system resulting in better  aeration transfer efficiency and thus lower power consumption compared to coarse bubble aeration system.