“…According to the analysis method of ferron colorimetric and 27 Al nuclear magnetic resonance, Al species are usually divided into monomeric species (e.g., Al(OH) 2 + , Al 2 (OH) 2 4+ , Al 3 (OH) 4 5+ ), medium polymer species (i.e., AlO 4 Al 12 (OH) 24 (H 2 O) 12 7+ , Al 13 ), and colloidal or solid species [28][29][30]. Previous studies indicated that with high positive charge and strong binding ability [31][32][33], both pre-formed and in-situ formed Al 13 polymer are the most active species in Al based coagulants responsible for coagulation [21,34,35]. Thus, researchers paid more attention to the regulatory method of Al 13 formation and subsequent efficiency enhancement during CC process.…”