Study of Floc-Blanket Clarifier, Combined with Lamella Settlement under the Condition of Prolonged Coagulation

Abstract

Water clarification working on the principles of contact flocculation is well known from 60 — 70 years ago. Since then different kinds of clarifiers have been constructed and used, where the separation of pre-destabilised colloidal particles from water is effected by the floe-blanket of previously formed flocs. Setting up and the quality of the floc blanket in these facilities working on the principle of hydraulic fluidization, depend on different factors as well as on coagulant dose, quality of formed flocs, upwards stream velocity in the floc — blanket zone, etc. (Aзepвьep, 1952, Mиндц and Kacтaльcкий, 1962; Tesarik, 1967, Miller and West, 1968). Recently, lamellas are set up above the floc-blanket. It is considered that the floc-blanket is stabilised and high treatment effect is achieved at a considerable increased upward flow velocity, about 1.6 up to 1.8 mm/s, while in common conditions it is 0.5 up to 0.9 mm/s. According to the data in Marin Galvin (1992), fixing up lamellas gives the opportunity of decreasing the coagulant dose by 14% in comparison with facilities without them.