Flocculation and removal of algae in algae-bloom water by chitosan-modified clays

Key words: 
• chitosan /
• clay /
• algae-bloom water

Abstract: The removal of algae in algae-bloom raw water by chitosanmodified clay flocculation was studied. The algal removal efficiency was greatly improved after the modification of the clays. Among the clays studied, high viscosity attapulgite was most efficient toward algae removal. The optimum total loading of high viscosity attapulgite was 66 mg/L (containing 6 mg/L chitosan) and the corresponding chlorophyll-α removal rate was 95.45%. Compared with chitosan, the chitosanmodified clays increased flocs density, reduced flocs volume, and improved flocs distribution. The chitosan-modified clays with particle size ranging from 25 μm to 74 μm had almost the same algal removal efficiency, indicating particle size of clays had little influence on the removal of algae. The algal removal efficiency was higher under acidic conditions, while declined rapidly with the increase of pH under alkaline conditions.