MBR Technology Approaches to Membrane Fouling Control
Membrane bioereactor (MBR) technology is one of the significant technology and plays an important role in wastewater treatment, it is a mixture of a conventional biological treatment system and physical liquid solid separation using membrane filtration in one system. The addition of membrane abolishes the need of secondary clarifiers and also reduced the plant area requirements, the land is a big issues especially in the big cities. With those years, almost all the government increase effluent discharge to land standards, this will need MBR to make sure high- quality effluent, higher volumetric loading rates, shorter hydraulic retention times( HRT), longer solid retention times (SRT ) and less sludge production. MBR overwhelms the shortcomings of the conventional activated sludge process.
However, the MBR also face a big challenge that the fouling issue, mainly biofouling which hampers the application and development of mbr. the new emerging of fouling control strategies including Quorum quenching, membrane cleaning, and also addition of aerobic granulations with MBRs.
Factors affecting membrane fouling can be categorised into three groups, these are membrane features, operational conditions and Biomass characteristics. the below figure shows the illustration of various factors that affect membrane fouling in MBRs.
Membrane Features:
The property of water affinity affects fouling in membrane bioreactor, Increasing hydrophilicity shows less membrane fouling tendency, whereas hydrophobicity correlates well with increase tendency for membrane fouling. It is because hydrophilic membrane materials absorb less macro solutes in wastewater, for example protein. Membrane fouling also depends on membrane surface roughness. If the surface roughness is high, then fouling is also faster, as the rough surface provides a valley for the colliodal particles in the wastewater to accumulate on. The colloidal particles that deposit on the membrane surface makes them negatively charged, therefore they can attract cations in the MLSS, such as Ca2+ and Al 3+ leading to inorganic fouling, Pore blocking tends to increase with increasing membrane pore size. Like Hinada Membrane’ s pore size is around 0.06 micron.
Operational Conditions:
Increasing aeration rates results in a decrease in membrane fouling, when the system is operated with high SRTs, it reduces the production of EPS and also it reduces membrane fouling. But if SRTs is extremely high, then it increase membrane fouling, because of the accumulation of MLSS and increased sludge viscosity. Decreasing HRTs results in increasing rate of membrane fouling and extremely high HRTs leads to an accumulation of foulants. The rate of membrane fouling in MBRs increases with increasing F/M ratio, it happens due to high food utilization by biomass which resulting in creased EPS prodution.
When the system is operated at higher COD / N ratio, it reduces the rate of membrane fouling and improve the membrane performance. In contrast, other studies found that low COD / N ratio results in lower MLSS concentration, lower SMPs production, lower carbohydrates, proteins, and humic acids in LB-EPS; therefore, low membrane fouling. In MBRs, temperature influences the rate of biodegradation and it impacts membrane fouling by changing the MLSS charateristics.
Feed and Biomass:
Membrane fouling also occurs when the concentration of EPS (Bound EPS and SMPs) increases. Decrease in floc size and pH results in increased rate of membrane fouling. Salinity also have an effect on membrane fouling. Increasing salinity relate with increased rate of membrane fouling. It happens because they alter the biomass charateristic like more release of bound EPS and SMPs, floc size and zeta potential.
The key factors affecting membrane fouling and advances in fouling mitigation strategies in MBRs, Besides two main foulants ( Biofoulants and organic foulants ), there are some other factors that influence membrane fouling.
Hinada is one of the leading MBR Manufacturer and has years of application in different type of wastewater, especially in MBR Technology Fouling Control, any questions can send to us, we will try our best offer good solution to you.
