Marcelo De Julio

FLOCULAÇÃO: CONSIDERAÇÕES A PARTIR DA ANÁLISE CLÁSSICA E DA AVALIAÇÃO DIRETA DA DISTRIBUIÇÃO DE TAMANHO DE PARTÍCULAS

This article presents some considerations on the flocculation from the classical analysis and direct evaluation of the particle size distribution. For this purpose, essays in bench scale were performed. The results were evaluated in the light of classical approach, given by the dimensionless number Camp (GT) and the kinetics of aggregation and breakage, as well as particle size distribution. It has been found that the use of GT isolated product is not suitable to represent the variations in flocculation performance and the classical model of aggregation and break-up can be biased by an indirect measurement of turbidity and sedimentation as an intermediate step. On the other hand, the direct evaluation of performance by particle size distribution, represented by linear continuous function, can be a promising tool for the evaluation of flocculation.

ESTUDO DA QUEBRA E RECRESCIMENTO DE FLOCOS EMPREGANDO UM EQUIPAMENTO DE MONITORAMENTO CONTÍNUO DA FLOCULAÇÃO

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.

Influence of the apparent molecular size of humic substances on the efficiency of coagulation using Fenton's reagent

This work used Fenton’s reagent as a coagulating agent in the treatment of water samples with high true colour caused by humic substances (HS) extracted from peat. In addition, the effects of the apparent molecular size of HS on coagulation, fl occulation and fl otation were studied. To that end, four distinct water samples having the same true colour were prepared using HS with different molecular sizes, which were obtained by ultrafi ltration fractioning. Through optimisation of coagulant dosage and coagulation pH, as well as posterior construction of coagulation diagrams for each water sample, it was verifi ed that the sample prepared with the smallest apparent molecular size of HS was the most diffi cult to treat, requiring higher coagulant (Fenton’s reagent) dosages than samples prepared with larger HS molecular sizes. Furthermore, fi ltration experiments after dissolved air fl otation (DAF) were carried out in an attempt to simulate conventional treatment. The most representative results in fi ltered water were: apparent colour ≤ 3 HU; turbidity < 0.5 NTU; and residual iron concentration < 0.005 mg/L. The absorbance and total organic carbon values of fi ltered water samples were also very low, suggesting that the formation of disinfection by-products with chlorine would likely be insignifi cant.