“…18 Among the synthetic coagulants, polyaluminum chloride (PACl) is known as the most active type of aluminum coagulant owing to the presence of Al 13 7+ complex in its structure and its high positive charge and strong binding ability. 19 In addition, some researchers have indicated that some metal ions resulting from the chemical coagulants in the CEPT process or the addition of PACl lead to the intensication of the process of the anaerobic digestion of sludge, consequently increasing the production of biogas by 10% and 21%. 3,20,21 In addition, CEPT improves volatile organic solids by more than 40%.…”