A collaborative coagulation strategy for algae-laden and dye-containing water treatment

Abstract

A collaborative coagulation strategy was proposed in this paper for algae-laden and dye-containing water treatment to realize the efficient, low-carbon, low-cost, fast, and synchronous removal of algal organic matters (AOMS) and dyes. Chemical conditions were optimized to achieve a higher collaborative coagulation efficiency, and the contributions of AOMS with different components and molecular weights (MW) were systematically analyzed to elucidate the mechanism of collaborative coagulation. Results showed that dye removal was enhanced with an increase in the proportion of AOMS (<50%). Collaborative coagulation efficiency showed a considerable dependence on the components of AOMS with high MW. 37.50% polysaccharides, 11.89% proteins, and 41.16% humic acid (HA) with WM higher than 100 kDa contributed 47.83–64.44% of the dye removal. The cross-linking reactions between the alum coagulant, AOMS, and dye active groups generated flocs with larger sizes and better settling abilities. Under alkaline conditions, alum hydrolysates produce efficient Lewis binding sites and lower steric hindrance, whereas AOMS deprotonation auxiliaries the formation of conjugated coordination and hydrogen bonds. These synergistic adsorption bridging effects were generated and the coagulation efficiency increased. Overall, the collaborative coagulation strategy realized the reutilization of algae-laden water from a new perspective, and achieved higher dye removal with a shorter hydraulic retention time, which are of great significance for the development of water treatment technology, energy savings, and emission reduction.