Fulvic acid removal performance and control of disinfection by-product formation potential in coagulation–ultrafiltration process

The performance of coagulation–ultrafiltration and coagulation processes in fulvic acid removal was evaluated and the disinfection by-product (DBP) formation potential of filtered and coagulated water was studied. In addition, the relation between floc properties and the performance of coagulation–ultrafiltration process was investigated by the experiments of floc size, fractal dimension and surface charge. When polyferric chloride (PFC) dosage was 24 mg L− 1 and solution pH was 6, the DOC removal efficiency improved from 32% to 49% after being filtered by ultrafiltration membrane. According to the analysis of chlorine decay by AQUASIM software, although K-SRA in filtered water is lower than that in coagulated water, TOTAL of filtered water is higher than that of coagulated water. This indicates that coagulation–ultrafiltration process can only reduce the DBP precursor reactivity rather than the DBP formation potential in treated water. Comparing the floc properties and the performance of coagulation–ultrafiltration process, it can be found that higher removal efficiencies of DBP precursors can be obtained if formed flocs are more compact and smaller.

► Coagulation–ultrafiltration can efficiently remove low weight organic matter.
► DOC removal rate improved from 32% to 49% after being filtered by ultrafiltration.
► Ultrafiltration reduced the DBP precursor reactivity of coagulated water.
► Small and compact flocs were advantageous to the DBP precursor removal.