Alternating multi-stage biological aerated filter device and method for treating domestic sewage

The invention discloses an alternate multi-stage biological aerated filter device for treating domestic sewage and a method thereof. The method comprises the following steps: selecting any filter to continuously feed water; in the first stage, the domestic sewage is primarily treated by the filter tank only feeding water but not discharging water, the other filter tank is backwashed, and backwashed water is deeply treated by the sedimentation tank and the third filter tank; in the second stage, after the backwashing of the backwashing filter tank is finished, the domestic sewage is primarily treated by the filter tank which keeps water inflow, the effluent of the filter tank which keeps water inflow is further treated by the backwashing filter tank, and the further treated effluent is deeply treated by a sedimentation tank and a third filter tank; and reselecting different filter tanks to alternately feed water, and repeating the steps. According to the invention, backwashing is carried out while continuous w