The long-aged sludge biofilm attached to the suspension carrier in the MBBR process provides a favorable living environment for the slow-growing nitrifying bacteria and can achieve effective nitrification effect, while the suspended activated sludge sludge age is relatively short, which mainly plays the role of removing organic matter, so it avoids the sludge expansion problem that is easy to occur when the traditional process maintains a long sludge age to achieve nitrification. Its sludge load is lower than that of the activated sludge process alone, while the treatment efficiency is higher and the operation is more stable.
The MBBR process not only has the high efficiency and operational flexibility of the activated sludge method, but also has the characteristics of the traditional biofilm method, such as impact resistance, long sludge age and less residual sludge. The process has the following characteristics:
(1) Low sludge load. The long-aged sludge biofilm attached to the suspension carrier provides a very favorable living environment for the slow-growing nitrifying bacteria and can achieve efficient nitrification, while the suspended activated sludge has a relatively short sludge age and can effectively remove organic matter. Therefore, the sludge load of this suspended and attached microbial co-pond growth process is much lower than that of the simple activated sludge process, and the treatment efficiency is higher and the operation is more stable.
(2) High removal rate of organic matter. Due to the large specific surface area of the suspended carrier, the large number and variety of microorganisms attached to its surface and inside, the sludge concentration in the reactor is generally 5~10 times that of the ordinary activated sludge method, and the total concentration is as high as 30~40g/L, which can greatly improve the removal efficiency of organic matter.
(3) Good denitrification effect. The microorganisms suspended and attached to the surface of the carrier in the MBBR reactor are in an aerobic state, oxidizing ammonia nitrogen to nitrate nitrogen, and the facultative and anaerobic zones inside the carrier are conducive to the growth of denitrifying bacteria and play the role of denitrification and denitrification, which has a good effect on the removal of ammonia nitrogen.
(4) Easy to maintain and manage. There is no need to set up a packing bracket in the aeration tank, which is convenient for the maintenance of the packing and the aeration device at the bottom of the tank, saving investment and floor space.
(5) It is not easy to produce sludge expansion. The suspension packing is washed by the water flow and air flow, which ensures the activity of the biofilm and promotes metabolism, and a large number of filamentous bacteria may grow on the filler that fluidizes with the water in the reaction tank, thus reducing the possibility of sludge bulging.