| 摘要 |
<p>PROBLEM TO BE SOLVED: To execute stirring and aerating/stirring without excess and shortage and to avert the degradation in the water quality of supernatant by measuring the liquid characteristics, such as dissolved oxygen, oxidation reduction potential and pH, of raw water, and changing over the stirring to aerating/stirring or from the aerating/ stirring to the stirring at the point of the time when the measured values attain prescribed values. SOLUTION: The screened raw water is transferred to a batch tank 1 and is alternately subjected to the stirring intended for denitrification and the aerating/stirring intended for nitrification in this batch tank 1; thereafter, the settling of the activated sludge, the discharging of the supernatant and the withdrawing of the sludge are executed batchwise. At this time, the liquid characteristics of the raw water subjected to the stirring of the first time are measured by liquid characteristic measuring instruments 14, such as dissolved oxygen meter, oxidation reduction potentiometer or pH meter. The raw water is confirmed to be denitrified at the point of the time when the measured values shift to minus. The stirring is then changed over to the aerating/stirring of the first time. Next, the liquid characteristics of the raw water subjected to the aerating/stirring of the first time are measured. The raw water is confirmed to be nitrified at the point of the time when the measured values shift to plus. The aerating/stirring are then changed over to the stirring of the second time.</p> |
