MBR-based biological treatment systems are used in mixed or industrial wastewater treatment plants. It provides an opportunity to modernize existing treatment facilities with the organization of an efficient treatment process without additional capital investments in construction (installation of membrane modules directly in the aeration tank).
Membrane bioreactors (MBR) are modern high-performance biological treatment facilities. Unlike the classical biological treatment scheme with the separation of the sludge mixture in the secondary sedimentation tanks, the membrane bioreactors separate the biological sludge flakes from the treated sewage by filtering the sludge mixture through an ultrafiltration or microfiltration membrane with a pore size of 0.04 to 0.4 micron. The main component of the MBR are cartridges consisting of membrane modules. The membranes may be in the form of a hollow fiber or two flat sheets with a polymeric substrate. The cartridges are immersed directly in the sludge mixture. Using a self-priming permeate pump, a negative pressure is created on the inner surface of the membranes. Due to the difference in pressure on the outer and inner surfaces of the membrane, the wastewater is filtered through the membrane layer. Treated water (permeate) is drained by a filtrate pump. The individual microorganisms (bacteria) of the biological sludge have a size larger than the pore size of the membrane. Therefore, in the filtration process, the biological sludge flakes, free-floating microorganisms and inert suspended substances are retained by the membrane and removed from the surface of the membrane by means of the aeration system.
The MBRs are factory-assembled. The system’s equipment, instrumentation, piping, control and shut-off valves are mounted on a metal frame.