Method for preventing loss of filter material during back washing of biological aerated filter (BAF)

Abstract

The invention discloses a method for preventing loss of a filter material during back washing of a BAF (biological aerated filter), which comprises the following specific steps: back washing by adopting a precipitation level, air washing, air-water combined back washing, repeating of the sequential steps of precipitation level, air washing and air-water combined back washing for 2-4 times, and water rinsing; the method can replace a traditional backwashing method of combining gas washing water with backwashing water rinsing. Compared with the traditional backwashing method, the method is suitable for an aerobic carbon oxidation biofilter, an aerobic carbon oxidation / partial nitrification biofilter, an aerobic nitrification biofilter and a denitrification biofilter; therefore, the filter material layer can be fully backwashed, and meanwhile, the problems of a large amount of backwashed material spraying, material running, filter material loss and the like caused by hardening of the filter material layer can be effectively solved.

Description

technical field [0001] The invention belongs to the field of sewage treatment, and in particular relates to a method for preventing filter material loss during backwashing of a biological aerated filter (BAF). Background technique [0002] The most important feature of biological aerated filter is the combination of biological oxidation and interception adsorption, and then regenerate the filter material through backwashing, so as to realize periodic operation, and has the advantages of simple process flow and high treatment efficiency. During the operation of the biological aerated filter, as time goes by, the microbial film growing on the filter material will gradually thicken, the retained suspended solids will accumulate, the porosity of the filter material will decrease, the head loss will increase, and the treatment efficiency will decrease. The normal operation of the filter tank must be backwashed to remove the dirt in the filter layer and restore the filter tank to ...

AI Technical Summary

Problems solved by technology

[0003] At present, the aerated biological filter in the sewage plant will have a certain degree of filter material compaction, which may be due to the following reasons: ① During the process of a large number of microorganisms on the surface of the filter material, macromolecular substances are secreted outward, which has a certain Viscous, the filter materials will be bonded together to form a hardened layer; ② Due to the long backwash cycle and incomplete backwash, the trapped suspended matter and shed biofilm will continue to accumulate between the filter materials, which will cause Filter material compaction; ③ Improper control of suspended solids in the influent of the filter, or oily substances, biochemical sludge, flocculants and other substances in the influent water, resulting in blockage and compaction of the filter material layer; ④ Denitrifying bacteria reduce nitrate nitrogen to The nitrogen process requires a strict anoxic environment. In the presence of molecular oxygen, denitrifying bacteria will preferentially use molecular oxygen. In order to ensure the anoxic environment and denitrification efficiency of the denitrification filter, the carbon source may be cast Excessive addition will cause a large number of heterotrophic bacteria to multiply, the pressure of the filter will rise, and it will start to compact

[0004] When the filter material layer reaches a certain degree of hardening, during the backwashing process, especially when the air-water combined backwashing, the filter material layer will lift up, and the phenomenon of material spraying will occur in the weak part of the hardened filter material layer, and a large number of microbial films will fall off. And the intercepted suspended matter spews out, and part of the filter material will enter the waste water pool with the backwash wastewater, resulting in a large loss of filter material

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