JPS571410A - Water treatment - Google Patents

Abstract

PURPOSE:To contrive to increase the treating capacity of an existing settling basin and enhance the quality of treated water, by a method wherein a flock circulation type flocculating and settling basin is provided on the upstream side of the existing settling basin so as to conduct flocculation and partial settling for raw water therein. CONSTITUTION:At the flocculating and settling basin, the raw water is introduced via an inflow pipe 3 and flows downward from a raw water distributing chamber 4 into the first mixing chamber 5. In the chamber 5, a flocculant is fed into the raw water through a flocculant feeding pipe 6 and the mixture is stirred by stirring blades 8, whereby minute flocks are newly formed. The new flocks grow while being adsorbed by th existing flocks which flow down from a recirculation part 9 of a separating chamber 11. The raw water then moves upward while contacting with the flocks and is fed into the second mxing chamber 10, while a part of it flows into the separating chamber 12. On the other hand, the major part of the raw water in the flocked condition is transferred through a transferred pipe 13 into the existing settling basin 2, where the flocks are separated by settling and the clarified water is separated by an overflow.