The jar-test results show that conventional coagulation (alum dosage of 10-60?mg/L and final pH of 6.5-8.0) removed ¡Ü20 % of PFOS and PFOA. These chemicals tended to be removed better by enhanced coagulation at higher coagulant dosages (>60?mg/L) and (thus) lower final pH (4.5-6.5). A coagulation diagram was developed to define the coagulant dosage and solution pH for PFOS/PFOA removal. The results suggest that the primary PFOS/PFOA removal mechanism is adsorption to fine Al hydroxide flocs freshly formed during the initial stage of coagulation; increasing flocculation time from 2 to 90?min could not further improve PFOS and PFOA removals. Furthermore, the effect of NOM on PFOS/PFOA removal by coagulation was examined, and possible removal mechanisms were discussed.