PURIFICATION SYSTEM

The present invention provides a complete-circulation-type bio-toilet system in which adjustment tanks capable of storing water to be treated are arranged before and after a septic tank, thereby enabling stable provision of the system without stopping the system even when the system is in heavy use. In a bio-toilet system 1 that performs microbial treatment on water to be treated containing filth and circulates the water to be treated as washing water, it is provided with: a raw sewage tank 3 into which the water to be treated containing filth discharged from a toilet 2 is fed; a first adjustment tank 4 that stores water to be treated 31 discharged from the raw sewage tank 3 while performing aerobic treatment thereon by aeration and discharges the stored water to be treated 31 by a pump 43; a septic tank 5 that performs microbial treatment on the water to be treated 31 discharged from the first adjustment tank 4; a second adjustment tank 6 that stores the water to be treated 31 discharged from the septic tank 5 while performing anaerobic treatment thereon and discharges the stored water to be treated 31 by a pump 62; a reaction tank 7 that decomposes organic matter in the water to be treated 31 discharged from the second adjustment tank 6; and a washing tank 8 that stores the water to be treated 31 discharged from the reaction tank 7 for use as washing water for a toilet bowl.