Enhanced ballasted flocculation process using magnetite-based ballast materials and a vortex flash mixer for drinking water treatment in response to both flood and dry seasons

초록

In this study, the coagulation–flocculation characteristics of a ballasted flocculation process with a capacity of 300 m3/d were evaluated using a vortex flash mixer as a mixing device. Unlike previous studies, this study did not utilize coagulation and flocculation tanks. Instead, a synthesized ballast material, suitable for drinking water and free from contaminants, was employed. The ballasted flocs were examined for particle size and settling velocity using a charge-coupled device camera. The performance of the ballasted coagulation process was found to be excellent within a dosage of polyaluminum chloride at 50 mg/L and a pH range of 8.25, with the optimal injection amount of ballast material determined to be 1,000 mg/L. The formation mechanism of ballasted flocs using a vortex flash mixer was derived from the primary operational parameters of the ballast flocculation process. Subsequently, the resulted ballasted flocs were separated from the lamella plate, and the efficacy of this mechanism in enhancing water treatment was discussed. The water treatment performance of the ballasted flocculation process was confirmed through scenarios involving high turbid water during the flood season and the inflow of green algae in the dry season. Finally, the sedimentation and uniformity of formed ballasted flocs were evaluated based on temperature changes during the initial stabilization period and long-term operation of 12 months. The obtained experimental and theoretical factors provide key insights for future process design. The utilization of a single vortex flash mixer in the ballasted flocculation process, replacing the conventional coagulation and flocculation tank setup, holds promise for significant cost reduction in operational processes and the reduction in land footprint, which contributes to making the process more sustainable.

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