Circulating water tertiary treatment device

The utility model discloses a circulating water tertiary treatment device, which comprises a sewage tank, a mixed reaction tank, a first aeration biofilter, a second aeration biofilter, an activated carbon filter and a sand filter which are sequentially communicated through pipelines, wherein the mixed reaction tank is communicated with a doser through a pipeline, and the first aeration biofilter, the second aeration biofilter, the activated carbon filter and the sand filter are respectively communicated with a backwashing device through pipelines. The circulating water tertiary treatment device disclosed by the utility model has a simple structure, low operation cost and a good water outlet effect.