Research on Effect of Microplastics Removal through Combination of Coagulation and Sand Filtration

Microplastics (MPs) removal by coagulation and sand filter was investigated in a secondary wastewater treatment plant effluent matrix. The samples were collected and treated using three typical coagulants, i.e., ferric chloride (FeCl3), polyferric sulfate (PFS) and polyaluminum chloride (PAC). Results showed that all the three tested coagulants can effectively remove MPs with applicable dosages in tertiary treatment (10-50 mg/L). The highest removal rate obtained was 61% with 40 mg/L PFS, and PFS were slightly more efficient than PAC and FeCl3. After sand filtration, about 75.7% of MPs was removed. The combined PFS (40 mg/L) +sand filter process could remove 91% of MPs, 82% of suspended solids (SS) and 85% of total phosphorus (TP). The treatment cost of coagulant was about 0.0594 Yuan/t wastewater. Therefore, it is technologically and economically feasible to use coagulation and sand filter process to remove MPs from wastewater in tertiary treatment process in wastewater treatment plant.