STUDY OF FLOCS BREAKING AND REGROWTH EMPLOYING A CONTINUOS MONITORING OF FLOCCULATION EQUIPMENT

Abstract

The knowledge of the physical characteristics of the solids present in the processes and operations of the water and wastewater treatment is presented as a promising tool in designing projects and improvement operational of solid/liquid separation units. Within this context, in this work was evaluated, with the help of an equipment of continuous flocculation monitoring (EMCF), the behavior of flocs (formation, breakage and regrowth) produced during the stages of coagulation and flocculation of water-supply treatment. The flocs passed through speed gradient and breakage time of 543 s-1 and 5, 60 and 300 s, respectively. The water used in this test was prepared in a laboratory with the addition of kaolinite suspension in a well water and it presented a turbity of 25 ± 2 uT. It was used liquid aluminium sulphate iron-free as a coagulant agent (30 mg/L of the commercial product containing Al203 of 8.42%) together with or without an anionic polymer (0.05 mg/L); for the pH coagulation adjustment it was used NaOH (6mg/L). It was possible to determine that the flocs once broken over the influence of different breakage time, showed different potential of regrowth. This procedure indicates that the smaller the breakage time, the bigger was the capacity of flocs reach a size similar to the one observed before the breakage event. The application of the polymer and the aluminium sulphate as a coagulant agent increased markedly the potential of the broken flocs return to its own original size. Keywords: water treatment, flocculation, breaking, turbidity fluctuations, continuous monitoring.