Abstract: Micro-nano bubble coagulation and air flotation process was adopted to treat the fresh and stale algae-laden waters coming from the algae and water separation port of Tangxi River in Hefei. Effects of coagulant and air retention time on the separation of algae and water were investigated. Through comparing the method with pressurized dissolved-air flotation which is in operation at present in the separation port, experimental parameters of the best treatment effect were explored to achieve the optimal process conditions. Results showed that the optimal dosage of coagulant PAC for fresh and stale algae-laden waters was 24 g/m³ and 36 g/m³, respectively, and the optimum air retention time in floatation pool was 30 min and 40 min,respectively. The removal rates of total phosphorus(TP), total nitrogen (TN), chemical oxygen demand (COD) and suspended solids (SS) of fresh algae-laden water reached 96.50%, 53.10%, 85.70%, 99.00%, respectively. And the removal rates of TP, TN, COD and SS of stale algae-laden water reached 98.40%, 62.40%, 65.60%, 99.80%, respectively. The treatment effect of micro-nano bubble air flotation was better than that of pressurized dissolved-air flotation.

Key words: micro-nano bubble, separating algae from water, coagulant optimization and selection, coagulant dosage, air flotation time