Extracellular organic matter (EOM) is ubiquitous in the algae-polluted water and has a significant impact on the human health and drinking water treatment. We investigate the different characteristics of dissolved extracellular organic matter (dEOM) and bound extracellular organic matter (bEOM) recovered from the various growth period of Microcystis aeruginosa and the interactions of them and polyaluminum chloride (PACT). The roles of the different EOM in the algae-polluted water treatment are also discussed. The functional groups of aromatic, O-H, N-H, C-N and N-O in bEOM possessing the stronger interaction with hydroxyl aluminum compared with dEOM is responsible for bEOM and algae removal. Some low molecular weight (MW) organic components and protein-like substances in bEOM are most easily removed. And dEOM weakly reacts with PACl or inhibits coagulation, especially dEOM with the high MW organic components. The main coagulation mechanisms of bEOM are the generation of insoluble Al-bEOM through complexation, the bridge of AlO4Al12(OH)(24)(H2O)(12)(7+) (Al-13), the adsorption of Al(OH)(3(am)) and the entrapment of flocs. The adsorption of Al-13 and Al(OH)(3(am)) mainly contribute to dEOM removal. It is also recommended to treat the algae with dEOM and bEOM at the initial stage. (C) 2017 Elsevier B.V. All rights reserved.