Characterisation of floc size, effective density and sedimentation under various flocculation mechanisms

Abstract

Floc structure plays an important role in the separation of coal wastewater. In this study, a camera-based method is used to evaluate quantitatively the structural characteristics of flocs generated by different coagulants and flocculants. The correlations between particle size, settlement velocity and effective density of coal tailings flocs are analysed. The results show that the statistical settling velocity increases linearly with floc size, while the effective density decreases with increase in floc size. Different flocculation mechanisms lead to diverse growth abilities of flocs. When the flocculant is used alone, the quality of the flocs generated by the flocculants, cationic polyacrylamide (CPAM) and non-ionic polyacrylamide (NPAM), is better than that generated by anionic polyacrylamide (APAM). However, the combination of trivalent cations and APAM yields a much better effect than that obtained using CPAM and NPAM. Flocs become larger and more compact when treated with a coagulant combined with a flocculant.

Enhancement of Biomass Production in Colony-Forming Green Algae, Botryosphaerella sudetica, Under Mixotrophic Cultivation

“…Other conditions tended to be similar, with no noticeable difference. Based on the sedimentation rate and proportion of settled biomass, we confirmed that changes in the colony size induced by the mixotrophic conditions were related to changes in settleability (Park et al, 2011(Park et al, , 2015Su et al, 2012;Fan et al, 2020). Therefore, these results suggest that the mixotrophic condition supplemented with glucose enhances the colonyforming ability and settleability of B. sudetica KNUA107.…”

“…Colony size is one of the main factors that affect settleability (Park et al, 2011(Park et al, , 2015Su et al, 2012;Fan et al, 2020). Settleability changed with mixotrophic conditions, increasing with glucose and decreasing with other added carbon sources.…”

The Synergistic Effects of Al3+ and Chitosan on the Solid–Liquid Separation of Coal Wastewater and Their Mechanism of Action

“…Figure 3 shows the flow of the coal slurry floc morphology analysis. The effective density of flocs was calculated by taking a 500 mL measuring cylinder with a rubber-tipped burette and recording the settling process of single flocs according to the Stokes formula (Equation (4)) [ 37 ]: where is the effective density, kg/m 3 ; and are the densities of the floc and water, respectively, kg/m 3 ; is the dynamic viscosity coefficient of water, Pa·s; is the gravitational acceleration, m; is the settling velocity, m/s; and is the floc size, m. In this study, the Reynolds coefficient was ignored for the static settling behavior of the flocs.…”

Optimization of Quartz Sand Enhanced Coagulation for Sewage Treatment by Response Surface Methodology

“…Firstly, the settling of flocs generated by coagulation is too slow and the settling time is too long, resulting in a large volume and occupied area of the sedimentation tank, which increases construction investment [4,5]. Secondly, research has shown that the efficiency of sewage coagulation treatment(SCT)is significantly related to the dosage of coagulants, that is, increasing the dosage of coagulants within a certain range can effectively improve the efficiency of SCT, but also increase the cost of water treatment [6,7].…”