biological aerated filter (baf) integrates biological oxidation and suspended solids interception to save the subsequent secondary sedimentation tank and sludge reflux, and simplifies the treatment process on the premise of ensuring the treatment effect.
biological aerated filter (baf) has the characteristics of high volume load, high hydraulic load, short hydraulic residence time, less capital investment, small area and good quality of treated effluent. because there is no sludge bulking problem in baf, microorganisms will not be lost and high biological concentration can be maintained, so daily management is simple.
for carbon removal and nitrification, two-stage biological aerated filter can be used to remove ammonia nitrogen. two-stage method can domesticate dominant bacteria with different functions in two filters, each of which is responsible for improving biochemical treatment efficiency.
first paragraph
biofilter mainly removes carbonized organic matter from sewage. in this filter, the dominant growth microorganism is isoaerobic bacteria. along the height direction of the filter, the gradient of organic matter concentration from the inlet end to the outlet end is decreasing, and the degradation rate is also decreasing. because the degradation rate of organic matter is faster, the autoxidation microorganism is in the inhibition state at this time.
the second paragraph
biofilter mainly nitrifies ammonia nitrogen in sewage. in this section of biofilter, due to the lower concentration of organic matter in the influent and the fewer heterotrophic microorganisms, the dominant growth microorganisms are autotrophic nitrifying bacteria, which nitrate ammonia into nitrate or nitrite. the removal of ammonia nitrogen depends to a certain extent on the organic load in the filter nitrification. when the organic load of bod5 is higher than 3.0 kg m3_d, the ammonia nitrogen is obviously inhibited. when using biological aerated filter to simultaneously remove carbon and nitrate, the organic load must be reduced. therefore, when using biological aerated filter process to remove organic matter, first of all, we must select appropriate volume load according to the data of similar sewage treatment effluent, and leave a certain amount of surplus in design. at the same time, when carbon and nitrification, we must reduce the organic load, preferably under 2 kg m3_d.
denitrification. for wastewater requiring denitrification, there are usually two kinds of denitrification: pre-denitrification and post-denitrification. the precondition of pre-denitrification is to meet the requirement of carbon source for denitrification. wastewater first passes through dn filter or dn section of filter (denitrification and nitrification are combined in one filter, and the purpose of nitrification and denitrification is achieved through the combination of different filters). then, through the aerobic section of the aerobic filter or filter, the effluent of the aerobic filter is returned to the denitrification filter, and the effluent of the nitrification filter is returned to the denitrification filter. denitrifying bacteria use the organic matter in the influent as the electron donor, and no-3-n as the electron acceptor to transfer the electron, and finally convert the effluent into n2 and transfer it to the air to achieve the purpose of wastewater denitrification.
post-denitrification is the aerobic stage in which wastewater first passes through the nitrification filter or filter, and the effluent enters the dn stage of the dn filter or filter. the disadvantage of post-denitrification technology is that it needs additional carbon source and its operation cost is relatively high. at the same time, how to add appropriate amount of carbon requires reliable control and stable inflow concentration. at the same time, the effluent needs aeration to remove excessive carbon.
for municipal wastewater treatment plants, both nitrogen and phosphorus removal processes are generally needed. chemical and biological phosphorus removal methods are commonly used for phosphorus removal.
source: polaris water treatment network
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