The enhanced treatment of algae-laden water by combination of powdered activated carbon and chlorine

Abstract

Nowadays, many pre-treatment strategies including pre-chlorination as well as pre-addition of powdered activated carbon (PAC) have been attempted to enhance the removal of algae cells as well as algae by-products by traditional coagulation. This study investigated the effects of these two agents (PAC + Cl) as pre-treatment on the coagulation of two common cyanobacteria (M. aeruginosa (MA) and Pseudoanabaena sp. (PI)) laden water. The results indicated that when PAC and chlorine were combined, the PAC could effectively catalyze chlorine to generate Cl and HO2/O2− and thus significantly enhance the organic matter removal in both MA and PI water treatment. Furthermore, the effluent organics of MA water by PAC + Cl contained less tryptophan-like proteins with aromatic structure and more tyrosine-like proteins with chain structure than those by chlorine alone, which might be due to the free radical reaction catalyzed by PAC. However, though the PAC could catalyze chlorine, the algae cells attached to or embedded in PAC particles demonstrated to be more resistant to inactivation by chlorine than non-attached free algae cells. Moreover, when treating algae released micropollutants such as 2-methylisocentaitol (2-MIB), its removal efficiency was more relied on the chlorine dosage. When chlorine dosage was too low, the generated free radical preferred to reacted with background organics rather than 2-MIB, resulting a reduction in 2-MIB removal. This study could provide guidance in proper pre-treatment strategies selection and combination for algae-bloom water treatment.