Advantages and disadvantages of split and integrated MBR membrane bioreactors

What is a split membrane bioreactor?

Separate membrane bioreactors use the membrane module as a separate unit from the bioreactor, the mixture is pressurised by the system into the membrane module, the permeate of the membrane module is the effluent of the system and the concentrate of the membrane module is returned to the reactor. Separate membrane bioreactors all use staggered flow membrane modules, where the mixed liquor flows parallel to the surface of the selected membrane and perpendicular to the flow direction of the filtrate. Staggered flow filtration creates a greater shear force, which limits the thickness of the cake layer and is extremely effective in mitigating membrane contamination. In order to maintain a stable water permeability, the staggered flow rate at the membrane surface is generally required to be greater than 2m/s, which requires a higher volume of circulating water, making the energy consumption per unit of produced water higher.

Separate membrane bioreactors have a high membrane flux, membrane modules are easy to clean and replace, and operation is stable and reliable Separate membrane bioreactors can be used for both aerobic and anaerobic treatment.

What is an integrated membrane bioreactor?

An integrated membrane bioreactor is one in which the membrane module is submerged in the reactor without the need for a solid-liquid separation circuit. The permeate from the membrane module is used as the effluent of the system through the head pressure difference or pumping, while the retained activated sludge remains in the reactor. Due to the aeration device installed directly below the membrane module, the aeration causes the mixture to flow upwards with the airflow, creating a shear force on the membrane surface and achieving a staggered flow on the membrane surface, where the sludge particles are forced to leave the membrane surface, delaying the generation of membrane contamination. The integral membrane bioreactor consumes less energy, but is less stable in operation, cleaning of the membrane and easier to replace than the split membrane bioreactor.

What are the advantages and disadvantages of split and integral membrane bioreactors?

Separate membrane bioreactors require operation at higher pressures, and the actual membrane flux is higher than that of all-in-one membrane bioreactors, requiring higher mis-flow rates and higher pressures to retard membrane contamination and ensure membrane flux, resulting in a 0.5M flow rate of approximately 1 to 3m/larger circulation rate and higher energy consumption. On the contrary, the working pressure of the integrated membrane bioreactor is smaller, generally 0.003~0.03 MPa. The integrated type does not need to circulate the mixed liquid, and the continuous aeration and intermittent water discharge operation method can achieve the staggered flow cleaning of the membrane surface, and its energy consumption is only 1/10~1/20 of the split type, but the membrane flux is lower.