The invention belongs to the technical field of
biological filter beds, and particularly relates to a multi-stage aerobic-anaerobic compound
biological filter bed, comprising a water inlet
pipe and more than two stages of filter beds; the height of a liquid level of each stage of the filter
bed is gradually reduced and each filter
bed is divided into a water inlet groove, a filtering chamber and a water outlet groove by rectification walls; each filtering chamber is filled with filler
layers; the grain diameters of fillers of the filler
layers at the two sides are great and the grain diameters of the fillers of the middle filler layer are small; the grain diameters of the fillers of the middle filler layer are sequentially reduced according to the stages of the filter beds; a water outlet end of the water inlet
pipe is arranged at the bottom of the water inlet groove of the foremost stage of the filter bed and the bottoms of the water outlet grooves of the upper and lower stages of the filter beds are communicated through a
siphon; the bottom of the water outlet groove of the final stage of the filter bed is connected with a water discharging groove; the middle filler layer is internally provided with a ventilated vertical
pipe, a ventilated main pipe and a ventilated
branch pipe; the ventilated
branch pipe is provided with air vents at intervals and plants which can degrade pollutants are planted at the upper parts of the filler
layers. With the adoption of the structure, the multi-stage aerobic-anaerobic compound
biological filter bed provided by the invention has the advantages of small occupied area, convenience for construction, lower cost, wide application range and the like.