There are several types of secondary treatment processes that people used to treat the effluent. In the secondary treatment process, BOD and COD content present in the effluent is reduced. The processes used in this treatment scheme are,
- Activated Sludge Process (ASP)
- Extended Aeration System (EAS)
- Membrane Bio-Reactor (MBR)
- Moving Bed Biofilm Reactor (MBBR)
- Sequential Batch Reactor (SBR)
- Up-flow Anaerobic Sludge Bioreactor (UASB)
Moving Bed Biofilm Reactor (MBBR)
- MBBR process uses the principle of aerobic digestion to reduce the BOD and COD present in the effluent. In aerobic digestion, microorganisms are grown on the biofilm in the presence of oxygen. Oxygen is used as a catalyst in this process as it enhances the growth of microorganisms.
- The media used in the MBBR process has a surface on which biofilm can grow. Generally, this media is made from virgin HDPE material. However, there are media with different MOC’s as well, the most common is PU (Polyurethane).
- There is a protected surface on each biofilm carrier which increases the productivity and growth of heterotrophic and autotrophic bacteria within its cells.
- It is this high-density population of bacteria that achieves high-rate biodegradation within the system while alsooffering process reliability and ease of operation.
Advantages of MBBR
- MBBR system requires a lesser footprint compared to the activated sludge system because the biomass in MBBR is more concentrated and the efficiency of the system is less dependent on the final sludge.
- MBBR system doesn’t need the recycling of the sludge.
- An existing plant’s capacity can be increased using MBBR as a retrofit.
- In future, if the organic load or the flowrate increases, we can increase the capacity by adding more number of media in the tank.
- MBBR has a higher effective sludge retention time (SRT), which is favourable for nitrification.
- As there is no sludge return time process performance is independent of the secondary clarifier.
MBBR Process
- Inlet pump
- The inlet pump is used to pump the effluent from the primary treatment
- Aeration tank
- Effluent is stored in the aeration tank for a specific timeframe which is known as Hydraulic retention time (HRT). HRT is calculated basis the total BOD and COD load of the system.
- The tank size is calculated on the basis of the total media required and its filling ratio to get the stipulated results.
- Equipment for aeration
- For Aeration purpose, there are different products available in the market like Diffusers, Air Grid, Submerged Aerators, etc.
- In India, companies prefer to use diffusers because it has high Oxygen transfer efficiency (SOTE)
- Diffuser selection depends upon the media used.
- MBBR media
- Screens for media retention
- A screen is needed to retain the MBBR media present in the tank at its outlet.
- Removal of biomass
- Biomass floating on the surface of the tank has to be removed before it is sent for further treatment.
- Equipment that can be used are DAF, Tube settler, Lamella clarifier, etc.
- Final treated water collection tank
- After treatment, the effluent is stored in this tank from where it is taken for further treatment.
- Sludge collection sump
- The dead bacteria that dies after consuming BOD and COD are retained in the form of sludge from the bottom of the tank.
- Dewatering unit
- A dewatering unit is required to further dry the sludge.
- The centrate at the outlet of the dewatering unit is then recirculated to the system.
Type of MBBR media
There are several types of media available in the market the most common is HDPE media. One can differentiate the media basis below factors,
| Size and shape | Material of construction | Surface area(m2/m3) | Void ratio(%) | Filling ratio(%) |
|---|---|---|---|---|
| Round | HDPE | 400 | 80 | 10 |
| Square | PU | 500 | 90 | 20 |
| Coin | PVA | 700 | 25 | |
| Cube | 3000 | 40 | ||
| 5000 | 50 | |||
| 48000 |
For more details, visit DAF and Media
Industries where MBBR can be used
- Textile industry
- Municipal plants
- Coke and steel plant
- Petro and oil industry
- Food and beverage industry
- Pharmaceutical and chemical industry
- Aquaculture industry and fish farming