SEWAGE TREATMENT SYSTEM AND SEWAGE TREATMENT METHOD

To determine an optimum circulation rate and realize power saving.SOLUTION: A sewage treatment system 1 includes: a treatment device 10 that treats organic substances contained in water to be treated by microorganisms and discharges them; a circulation device 20 that circulates the treated water discharged by the treatment device 10 to the treatment device 10; a measuring instrument 30 that measures at least one of a suspended solid, turbidity, and redox potential of the water to be treated; and a control device 40 that estimates an organic matter concentration of the water to be treated based on a value measured by the measuring instrument 30 and determines a circulation rate of the water to be treated circulated from the treatment device 10 to the circulation device 20 based on the estimated organic matter concentration.SELECTED DRAWING: Figure 1 【課題】最適な循環率を決定して動力の省エネ化を実現する。【解決手段】汚水処理システム１は、被処理水に含まれる有機物を微生物により処理して排出する処理装置１０と、処理装置１０が排出した処理水を処理装置１０に循環する循環装置２０と、被処理水の、懸濁物質、濁度、酸化還元電位の少なくとも何れか１の値を計測する計測器３０と、計測器３０が計測した値に基づき、被処理水の有機物濃度を推定し、推定した有機物濃度に基づき、処理装置１０から循環装置２０に循環する処理水の循環率を決定する制御装置４０とを備える。【選択図】図１