Enhanced removal of microplastics from drinking water using ballasted flocculation: a comparative study with conventional methods using non-intrusive image analysis

Microplastics have become a worldwide subject of significant concern as an emerging pollutant and have been repeatedly found in water supplied by drinking water treatment plants. The aim of this study was to investigate the removal of polyvinyl chloride microplastics (PVC MPs), which are among the most hazardous polymers. Alum was used as the coagulant, and anionic polyacrylamide (PAM) served as the flocculant, in both conventional and ballasted flocculation processes for water treatment. A nonintrusive imaging technique was used for monitoring floc growth and terminal settling velocity (vs) assessment. Conventional flocculation achieved the best performance with 78.2% PVC MP removal, a mean floc size of 282 mu m and a mean vs of 0.7 cm/min in a settling time of 3.5 min. The addition of 0.8 mg/L of PAM over the former condition improved the removal to 84.2%, with a mean floc size of 384 mu m and a mean vs of 1.7 cm/min. Ballasted flocculation achieved 99.6% removal in a settling time of 6 s, with a mean floc size of 481 mu m and a mean vs of 120 cm/min, which is 70-fold greater than that of conventional flocculation. This investigation underscores the potential of ballasted flocculation as a highly effective method for removing PVC MPs from drinking water.