SEWAGE TREATMENT METHOD, SEWAGE TREATMENT APPARATUS AND SEWAGE TREATMENT SYSTEM EQUIPPED WITH SEWAGE TREATMENT APPARATUS

摘要

PROBLEM TO BE SOLVED: To efficiently perform biological reaction treatment in a biological reaction tank even if necessity for always measuring a dissolved oxygen value or an oxidation-reduction potential value and restriction having to always keep the high accuracy of a measuring instrument for measuring the value are eliminated. SOLUTION: A scheduled time for performing an anaerobic process and a scheduled time for performing an aerobic process after the anaerobic process are respectively preset. The dissolved oxygen value in a biological treatment tank is measured at the completion scheduled time B of the anaerobic process and, when the measured value does not reach a target anaerobic DO, the anaerobic process is extended so as to exceed the scheduled time. At the point C of time when the dissolved oxygen value reaches a target anaerobic DO during this extended time, the anaerobic process is changed over to the aerobic process and the scheduled time of the aerobic process is shortened by the time extending the anaerobic process.