Therefore, the optimal dye concentration was 50 mg/L. Thisobservation can be due to the decrease in the flocculating capac-ity of the mucilage by increasing the dye concentration (Mishraand Bajpai, 2005). Based on a particle–polymer–particle complexformation, the polymeric coagulant serves as a bridge. When apolymer molecule comes into contact with a particle, the chem-ical groups on the polymer interact with the surface of the colloidalparticle. The free remaining part of the polymer will attach itselfto another particle and promote flocculation. Therefore, the actionof polymeric agents is very concentration-dependent. The obtainedresults are similar to those reported by Mishra and Bajpai (2005)and Beltran-Heredia et al. (2009). In short, higher dosage of nat-ural coagulant might be required to treat wastewater with higherinitial concentration by providing extra sites for physical adhesionand chelation through hydrogen bonding to the pollutant particles