Due to the limited nature of freshwater resources and growing demand for clean water it is a necessity to recover wastewater. Wastewater is any form of water that has been contaminated by a commercial or domestic process. Wastewater treatment is a process that converts wastewater from its unusable state into an effluent that can be either returned to the water cycle with minimal environmental issues or reused for another purpose. Thus it lead to use of waste water treatment methods like Moving Bed Bio Reactor Membrane Bioreactor, Sequencing Batch Reactor, Sequencing Batch Biofilm Reactor Treatment systems in removing BOD and COD from wastewater..Membrane Bioreactor (MBR)The term Membrane Bioreactor (MBR) is generally used to define wastewater treatment processes where a selective permeable membrane is integrated with a biological process. All commercial MBR processes use the membrane as a filter, rejecting the solid materials which are developed by the biological process, resulting in a clarified effluent.Types of MBRA. Side Stream Membrane Process (sMBR)B. Immersed Membrane Process (iMBR)Side-Stream Membrane Process (sMBR)Where membrane system is placed separately outside of aeration tank, it is called side-stream membrane process it relied on crossflow filtrations using mostly tubular modules and some plate and frame modules. High liquid velocity on membrane surface is required to prevent membrane fouling effectively. The sMBR typically provides reliable performance with relatively easy maintenance due to the accessibility to the externally installed membrane system However, the cost of this membrane system is high due to the necessity of housings to hold membranes in them at the relatively high pressure (3-6 bar). In addition, energy costs to circulate liquid to be filtered is prohibitively expensive for municipal wastewater treatment..Immersed Membrane Process (iMBR)Submerged membrane filtration was invented to save capital and operational costs by directly placing membranes in mixed liquor without housings. It is a filtration procedure with membranes that are submerged in the biomass, inside the bioreactor itself. The membranes are submerged directly in the bioreactor and filtration takes place by applying vacuum to the inside of the membrane. Membrane fouling is prevented by the flow of coarse air bubbles along the membrane surface or periodic back flushing. Advantages• Economically attractive• Compact• Trouble-free operation• Options for water reuse• Fast delivery timeSpecial Applications• Reuse for technical applications (deck wash etc.)• Reuse for toilet flushing• Use of “extended” system for operating in zero-emission areas• Tailor-made executions• Also for Retro-fit.Moving Bed Bio Reactor (MBBR)In the MBBR biofilm technology the biofilm grows protected within Fab Media, which are carefully designed with high internal surface area. The bio reaction is carried out in controlled environment in this process water Tank. The MBBR biofilm technology is based on specially designed plastic biofilm (Fab Media) carriers or bio carriers that are suspended and in continuous movement within a tank or reactor of specified volume. The Bio reactors comprises of a tank, fitted with aeration grid. The bacterial activity needs dissolved oxygen, to synthesize the organic matter. This is supplied by passing air in the form of small bubbles. The air is passed at the bottom of tank, so that complete volume of tank is utilized. Oxygen dissolved in liquid which can now be used by the bacteria. The bacterial population is present on the media, which forms an integral part of the reactor system. Fab Media are kept in the MBBR. The bacteria grow on these fab media, by using the organic content in the raw sewage and the dissolved oxygen available. Due to constant aeration the media is set in whirling motion, so that continuous mixing takes place. The bacterial layer growth on the media surface increases to a certain extent, and then gets sloughed off after a specific period. This phenomenon is called sloughing. This creates new surface for further bacterial growth. Sloughing takes place only after complete growth and subsequent dyeing – off the bacterial layer. The Sloughed bio mass is drained to sludge drying beds.Diffused aeration involves the introduction of Atmospheric air into the sewage through the submerged diffusers. Part of organic matter is synthesized into new cells and part is oxidized to carbon dioxide and water. The sloughed bio mass must be removed before the treated effluent is taken for downstream treatment..Advantages:• Higher effective sludge retention time SRT which is favorable for nitrification• Doesn’t need a recycling of the sludge, Provides higher surface area, so smaller place , Maintenance-friendly, High volume load, Simply to extend• It is efficient, compact and easy to operate.Disadvantages:• High operating cost due to large power requirements• Skilled operators needed• Continuous monitoring is required• We may get some dead mass in clear supernatant which increase the filter load.Sequencing Batch Reactor (SBR)SBR technology is one of the most advance system of Activated Sludge process.SBR Process treats the waste water in a batch mode. It consists of at least two identical tanks. Each tank is equipped with Fixed or floating Aerators, decanter and a waste sludge pump.There are five stages in this treatment process:I) Fill: Tank is being filled in with waste water and with floating plastic media (Fab Media)II) React or Aerate: Fixed or floating Aerators blow air bubbles in the tank which helps the bacteria to grow on fab media. These bacteria degrades organic matters which resulted in BOD removal.III) Settle: Now, aeration process get stop and settling of suspended solids starts.IV) Decant: Clear Effluent is removed from the tank through the decanter, without disturbing the settled sludge.V) Idle: Idle until it is time to commence (begin) a new cycle with the filling stage..Advantages:• SBR systems have been successfully used to treat both municipal and industrial wastewater.• Equalization, primary clarification (in most cases), biological treatment, and secondary clarification can be achieved in a single reactor vessel.• Takes More area as treatment time increasesDisadvantages:• It is hard to adjust the cycle times for small communities.• Sludge must be disposed frequently.• Civil work cost is very high..Sequencing Batch Biofilm Reactor (SBBR)To optimize the operation of traditional SBR’s and reduce the aeration phase with less HRT, a new technology has been developed which is called as Sequencing Batch Biofilm Reactor (SBBR). The sequencing batch biofilm reactor (SBBR) system has attracted a great deal of attention due to its ability to take the advantages of both a biofilm reactor and an SBR. In pure biofilm reactors the biomass grows only on Fab Media, whereas in SBBRs, both biofilm and suspended activated sludge are in the same tank.In the SBBRs, the biomass grows as a biofilm on Fab Media that move freely into the wastewater and achieved better performance in removing the COD. In addition, the optimal carbon nitrogen (COD/N) ratio for the Simultaneous removal of nitrogen and COD in the SBBR was found to be 12.5, and no accumulation of NO3—Nor NO2−-N was detected at this ratio, indicating that efficient simultaneous nitrification and denitrification (SND) was occurring in the reactor. The SND efficiency reached 98%. The performance of SBBR was investigated by the removal efficiency of COD, BOD, TSS and Ammonical nitrogen..Advantages:• SBBR systems can remove nitrogen and phosphorus simultaneously.• Presence of an anoxic microzone in the biofilm could result in Simultaneous nitrification anddenitrification in the SBBR during the aeration phase.• In such cases, nitrification occurs on the surface of the biofilm, whereas denitrification occurs in the inner layers due to a dissolved oxygen (DO) gradient within the biofilm. Disadvantages:• Even though we will get good bio degradation of BOD, we will get some Suspended Solids which cannot able to remove by SBBR.• Capital cost is high.• Civil work cost is very high
Due to the limited nature of freshwater resources and growing demand for clean water it is a necessity to recover wastewater. Wastewater is any form of water that has been contaminated by a commercial or domestic process. Wastewater treatment is a process that converts wastewater from its unusable state into an effluent that can be either returned to the water cycle with minimal environmental issues or reused for another purpose. Thus it lead to use of waste water treatment methods like Moving Bed Bio Reactor Membrane Bioreactor, Sequencing Batch Reactor, Sequencing Batch Biofilm Reactor Treatment systems in removing BOD and COD from wastewater..Membrane Bioreactor (MBR)The term Membrane Bioreactor (MBR) is generally used to define wastewater treatment processes where a selective permeable membrane is integrated with a biological process. All commercial MBR processes use the membrane as a filter, rejecting the solid materials which are developed by the biological process, resulting in a clarified effluent.Types of MBRA. Side Stream Membrane Process (sMBR)B. Immersed Membrane Process (iMBR)Side-Stream Membrane Process (sMBR)Where membrane system is placed separately outside of aeration tank, it is called side-stream membrane process it relied on crossflow filtrations using mostly tubular modules and some plate and frame modules. High liquid velocity on membrane surface is required to prevent membrane fouling effectively. The sMBR typically provides reliable performance with relatively easy maintenance due to the accessibility to the externally installed membrane system However, the cost of this membrane system is high due to the necessity of housings to hold membranes in them at the relatively high pressure (3-6 bar). In addition, energy costs to circulate liquid to be filtered is prohibitively expensive for municipal wastewater treatment..Immersed Membrane Process (iMBR)Submerged membrane filtration was invented to save capital and operational costs by directly placing membranes in mixed liquor without housings. It is a filtration procedure with membranes that are submerged in the biomass, inside the bioreactor itself. The membranes are submerged directly in the bioreactor and filtration takes place by applying vacuum to the inside of the membrane. Membrane fouling is prevented by the flow of coarse air bubbles along the membrane surface or periodic back flushing. Advantages• Economically attractive• Compact• Trouble-free operation• Options for water reuse• Fast delivery timeSpecial Applications• Reuse for technical applications (deck wash etc.)• Reuse for toilet flushing• Use of “extended” system for operating in zero-emission areas• Tailor-made executions• Also for Retro-fit.Moving Bed Bio Reactor (MBBR)In the MBBR biofilm technology the biofilm grows protected within Fab Media, which are carefully designed with high internal surface area. The bio reaction is carried out in controlled environment in this process water Tank. The MBBR biofilm technology is based on specially designed plastic biofilm (Fab Media) carriers or bio carriers that are suspended and in continuous movement within a tank or reactor of specified volume. The Bio reactors comprises of a tank, fitted with aeration grid. The bacterial activity needs dissolved oxygen, to synthesize the organic matter. This is supplied by passing air in the form of small bubbles. The air is passed at the bottom of tank, so that complete volume of tank is utilized. Oxygen dissolved in liquid which can now be used by the bacteria. The bacterial population is present on the media, which forms an integral part of the reactor system. Fab Media are kept in the MBBR. The bacteria grow on these fab media, by using the organic content in the raw sewage and the dissolved oxygen available. Due to constant aeration the media is set in whirling motion, so that continuous mixing takes place. The bacterial layer growth on the media surface increases to a certain extent, and then gets sloughed off after a specific period. This phenomenon is called sloughing. This creates new surface for further bacterial growth. Sloughing takes place only after complete growth and subsequent dyeing – off the bacterial layer. The Sloughed bio mass is drained to sludge drying beds.Diffused aeration involves the introduction of Atmospheric air into the sewage through the submerged diffusers. Part of organic matter is synthesized into new cells and part is oxidized to carbon dioxide and water. The sloughed bio mass must be removed before the treated effluent is taken for downstream treatment..Advantages:• Higher effective sludge retention time SRT which is favorable for nitrification• Doesn’t need a recycling of the sludge, Provides higher surface area, so smaller place , Maintenance-friendly, High volume load, Simply to extend• It is efficient, compact and easy to operate.Disadvantages:• High operating cost due to large power requirements• Skilled operators needed• Continuous monitoring is required• We may get some dead mass in clear supernatant which increase the filter load.Sequencing Batch Reactor (SBR)SBR technology is one of the most advance system of Activated Sludge process.SBR Process treats the waste water in a batch mode. It consists of at least two identical tanks. Each tank is equipped with Fixed or floating Aerators, decanter and a waste sludge pump.There are five stages in this treatment process:I) Fill: Tank is being filled in with waste water and with floating plastic media (Fab Media)II) React or Aerate: Fixed or floating Aerators blow air bubbles in the tank which helps the bacteria to grow on fab media. These bacteria degrades organic matters which resulted in BOD removal.III) Settle: Now, aeration process get stop and settling of suspended solids starts.IV) Decant: Clear Effluent is removed from the tank through the decanter, without disturbing the settled sludge.V) Idle: Idle until it is time to commence (begin) a new cycle with the filling stage..Advantages:• SBR systems have been successfully used to treat both municipal and industrial wastewater.• Equalization, primary clarification (in most cases), biological treatment, and secondary clarification can be achieved in a single reactor vessel.• Takes More area as treatment time increasesDisadvantages:• It is hard to adjust the cycle times for small communities.• Sludge must be disposed frequently.• Civil work cost is very high..Sequencing Batch Biofilm Reactor (SBBR)To optimize the operation of traditional SBR’s and reduce the aeration phase with less HRT, a new technology has been developed which is called as Sequencing Batch Biofilm Reactor (SBBR). The sequencing batch biofilm reactor (SBBR) system has attracted a great deal of attention due to its ability to take the advantages of both a biofilm reactor and an SBR. In pure biofilm reactors the biomass grows only on Fab Media, whereas in SBBRs, both biofilm and suspended activated sludge are in the same tank.In the SBBRs, the biomass grows as a biofilm on Fab Media that move freely into the wastewater and achieved better performance in removing the COD. In addition, the optimal carbon nitrogen (COD/N) ratio for the Simultaneous removal of nitrogen and COD in the SBBR was found to be 12.5, and no accumulation of NO3—Nor NO2−-N was detected at this ratio, indicating that efficient simultaneous nitrification and denitrification (SND) was occurring in the reactor. The SND efficiency reached 98%. The performance of SBBR was investigated by the removal efficiency of COD, BOD, TSS and Ammonical nitrogen..Advantages:• SBBR systems can remove nitrogen and phosphorus simultaneously.• Presence of an anoxic microzone in the biofilm could result in Simultaneous nitrification anddenitrification in the SBBR during the aeration phase.• In such cases, nitrification occurs on the surface of the biofilm, whereas denitrification occurs in the inner layers due to a dissolved oxygen (DO) gradient within the biofilm. Disadvantages:• Even though we will get good bio degradation of BOD, we will get some Suspended Solids which cannot able to remove by SBBR.• Capital cost is high.• Civil work cost is very high
