Method and installation for treating an untreated flow by simple sedimentation after ballasting with fine sand

A process for removing solids from an influent liquid, comprising:

• a) combining a flow of influent liquid, flocculent and insoluble granular particles in a first mixing chamber;
• b) mechanically agitating the influent liquid, flocculent and granular particles to produce a flocculated mixture in the first mixing chamber;
• c) passing the flocculated mixture from the first mixing chamber into a second mixing chamber;
• d) mechanically agitating the flocculated mixture in the second mixing chamber to produce a further flocculated mixture;
• e) passing the further flocculated mixture from the second mixing chamber into an upper portion of a down-flow zone;
• f) passing the further flocculated mixture from the upper portion of the down-flow zone, through the down-flow zone, to a lower portion of the down-flow zone, without further mechanical agitation, into a settling zone;
• and
• g) removing clarified liquid from a free flowing, unchanneled upper region of the settling zone that is open, unobstructed and includes no separator plates, and removing settled flocs and other settle materials from a lower region of the settling zone.