| 摘要 |
PURPOSE:To provide a method capable of feeding flocculant effectively, by considering the flocculant feeding rate in one system out of at least three treating systems in which turbidity of waste water to be treated is lowest as a reference value, and controlling the flocculant feeding rates of the other two systems in the manner that the flocculant feeding rate of one system is higher than the reference value by a predetermined amound whereas that of the other system is lower than the reference value by a predetermined amount. CONSTITUTION:Waste water to be treated is carried to valve 5 via sand settling basin or others and introduced into mixing basins 6A-6C where flocculant is mixed to the waste water. Then, it is carried to flocculating basins 7A-7C and settling basins 8A-8C. On the other hand, by means of arithmetic unit 15, flocculant feeding rates DA-C in the future are determined from turbidity TA- C at the outlet of settling basins 8A-8C measured respectively by turbidity meters 13A- 13C and flocculant feeding rates at the present. Providing that TB is minimal, flocculant feeding rate DB' in the future is kept equal to that DB at the present. Here, if DA is smaller than DC, flocculant feeding rates DA', DC' of systems A, C in the future are controlled to be DA'=DB-beta, DC'=DB+alpha. On the contrary, if DA is larger than DC, DA'=DB+alpha, DC'=DB-beta. |
