Membrane Bio Reactor/MBBR

Membrane bioreactor (MBR) is a new type of wastewater treatment technology combining membrane separation process with conventional activated sludge (CAS) treatment process. Due to the fact that the membrane pore size may be below 0.1μm, MBR can effectively produce a high-quality clarified effluent. The MBR process has received more and more attention because of its advantages such as high removal efficiency for pollutants, space saving, and less sludge production. Membrane filtration ensures that microorganisms are completely trapped into the bioreactor and this gives better control over the biological reactions and modifying the conditions of the microorganisms in the aerated tank. It enables long sludge retention time (SRT) and high mixed liquor suspended solid (MLSS) concentration.

Types of MBR:

1. Submerged/immersed membrane bioreactor (iMBR): In iMBR, membrane modules are immersed into the bioreactor directly. A suction pump is applied to draw the effluent through the membrane while the sludge is trapped into the bioreactor by the membrane. Air is usually utilized for providing oxygen to maintain aerobic conditions and scouring the membrane surface and clean the exterior of the membrane. The submerged membrane bioreactor (SMBR) is more commonly used than the cross-flow MBR due to less energy-intensive and lower fouling potential.
2. Cross flow membrane bioreactor (cMBR): cMBR is the combination of a traditional bioreactor with a membrane filtration device into a single unit process. The membrane module in the MBR is equivalent to the secondary settling tank of conventional biological treatment system, in which solid and liquid are separated, whilst the sludge is returned into the bioreactor and the permeate collected. This way, the membrane is easily cleaned in situ and operated with high sludge concentration in the MBR reactor.
3. Hybrid membrane bioreactor: This is similar to the iMBR system but is filled with some carriers in the reactor. This system is superior to the iMBR one as the carriers can stabilize the treatment process efficiently and reduce the membrane fouling.

The MBR process has obvious advantages over conventional wastewater treatment process:

1. MBR produces clarified water with high quality. The indicative output quality of MBR systems (microfiltration or ultrafiltration) includes suspended solids (SS) <1 mg l−1, turbidity <0.2 NTU (depending on the membrane nominal pore size). Removal of organic matters in MBR comes from two aspects: one is the biodegradation of organic pollutants in the bioreactor; and the other is the membrane filtration of organic matters with high molecular weight.
2. MBR has a smaller footprint. The secondary settling and tertiary sand filtration processes are eliminated, thereby reducing the plant footprint. In certain instances, the footprint can be further reduced because other process units such as ultraviolet disinfection can also be eliminated or minimized.
3. The MBR process, compared with CAS process, enables independent hydraulic retention time (referred to as HRT) and sludge retention time (referred to as SRT), which is difficult to control in CAS system. Solid particles could be held by membrane module in the bioreactor, which can give a better control of SRT and HRT in the system and also improve MBR biodegradation efficiency.
4. MBR can be designed with a long sludge age; hence, low excess sludge production can be achieved, which also promotes the enrichment of nitrifying bacteria, thereby enhancing nitrogen removal.
5. MBR provides a barrier to certain chlorine-resistant pathogens, because the membrane has an effective pore size of less than 0.1μm – smaller than the pathogenic bacteria and viruses in the sludge.

Moving Bed Biofilm Reactor (MBBR):

Unlike most traditional water wastage treatment systems, MBBR is a highly effective biological water treatment process that is based on a combination of biofilm media and conventional activated sludge processes. This way, water can be treated in both anaerobic and aerobic environments.

MBBR is currently the best water treatment solution for high-strength water systems. This is mainly because of the biological nitrogen removal (BNR), which uses MBBR systems thus improving waste matter quality and increasing treatment capacity with no extra footprint growth.

MBBR process utilizes floating plastic carriers (media) within the aeration tank to increase the amount of microorganisms available to treat the wastewater. The microorganisms consume organic material. The media provides increased surface area for the biological microorganisms to attach to and grow in the aeration tanks. The increased surface area reduces the footprint of the tanks required to treat the wastewater. The media is continuously agitated by bubbles from the aeration system that adds oxygen at the bottom of the first compartment of the aeration tank. The microorganisms consume organic material. When compared to conventional secondary treatment it provides superior efficiency and value.

MBBR process is known to improve reliability, simplify the operation and process not to mention the fact that it requires a smaller storage space compared to traditional sewage treatment plants. For this reason, there is a well-managed technology behind the MBBR process to help ensure this becomes possible.

The technology involved during the MBBR process uses thousands of polyethylene biofilm carriers. These carriers operate within an aerated mixed wastewater treatment basin in a combined motion.

Each carrier provides a protected carrier which helps in the help in the growth of autotrophic and heterotrophic bacteria within the cells. This technology helps increase productivity and effectiveness of the process.

The high population of bacteria helps achieve a high rate of biodegradation within the system and also provides ease of operation, not to mention the reliability of the process.

The MBBR process also has an optimum level of productive biofilm which makes the process and the technology cost-effective and easy to maintain. There is also the biofilm which is attached to the mobile carriers found within the system which automatically responds to load fluctuations.