MBR is a new water treatment technology which combines activated sludge process with membrane separation technology. Ultrafiltration membrane separation method is used to replace secondary clarifier and sand filtration system in traditional activated sludge treatment system. At present, MBR technology plays an important role in the treatment of pharmaceutical wastewater.

According to the location and pressure mode of the bioreactor and the membrane module, there are two types: the external type and the submerged type. The mixed liquid in the external MBR bioreactor is pressurized by a pump and then enters the membrane module. Under the pressure, the water in the mixed liquid passes through the membrane and becomes the treated effluent. The remaining substances are intercepted and returned to the reactor with the concentrated liquid. The direction of the filtered water in the system is from inside to outside.

The submerged MBR, also known as integrated MBR, is placed in the bioreactor. The filtrate is sucked out by the pump. The aeration device under the membrane module has the function of oxygenation, and the strong stirring effect reduces the absorption of suspended solids on the membrane surface.

In the pharmaceutical industry, MBR can maintain the biomass in the biological treatment unit at high concentration, reduce the area occupied by the bioreactor, make the residence time of some refractory macromolecule organisms longer, which is conducive to their decomposition. Backwashing and chemical cleaning can also be used to slow down the decline of membrane flux, so as to maintain the effective life of MBR system.

Experts say that MBR has many advantages in pharmaceutical wastewater treatment, such as high separation efficiency and guaranteed effluent quality. Pharmaceutical wastewater contains a large number of suspended substances. Through the separation of membrane, the suspended substances and turbidity in effluent are close to zero.

High sludge concentration and strong biochemical ability. Almost all activated sludge can stay in the reactor by using membrane module instead of secondary sedimentation tank, which can effectively increase sludge concentration.

It is known that the sludge concentration of MBR can reach 18 000-19 000 mg/L. Experts said: "Compared with the traditional process, it can improve the sludge concentration, and avoid the loss of activated sludge after the occurrence of sludge bulking."

It improves the purification efficiency of refractory organic matter and shortens the hydraulic retention time. The refractory organic substances in pharmaceutical wastewater are intercepted in the reactor, and more contact time with microorganisms is obtained than traditional biological methods, which is conducive to the cultivation of specific microorganisms and the improvement of the purification efficiency of refractory organic substances.

It is beneficial to the growth of nitrifying bacteria and the removal efficiency of NH3-N is good. The membrane of MBR could not intercept NH3-N. The main reason that MBR had higher NH3-N removal rate was that there were a large number of nitrifying bacteria in the reactor. Under the action of membrane separation, the slow-growing nitrifying bacteria were kept in the reactor, which created favorable conditions for their growth and reproduction.

With the development of pharmaceutical industry, pharmaceutical wastewater has become one of the important pollution sources. However, pharmaceutical wastewater is difficult to treat because of its complex composition, high organic content, high toxicity, deep color and poor biochemical properties. MBR process has the advantages of simple process, stable treatment effect and convenient management.

As a new type of wastewater treatment process, MBR process has not been widely used in pharmaceutical wastewater treatment, but it can avoid some residual drug substances in the traditional process of wastewater treatment, inhibit the growth and reproduction of microorganisms, cause sludge bulking, and ultimately make biochemical treatment ineffective.

In addition, MBR process also has membrane easily polluted. After a certain period of operation, the membrane should be backwashed. With the increase of operation time, the backwash cycle is constantly shortened; the manufacturing cost is high, and the energy consumption is high.