Fishpond Water Treatment: Removal of Microalgae from Fishpond Wastewater through Embedding-Flocculation and Sedimentation

摘要

Microalgae is an alternative means to remove excessive nutrients from fishpond water. However, the over blooming of microalgae will leads to eutrophication problem. Therefore, the microalgae have to be removed from fishpond water so that the water can be treated and avoid water pollution. In this study, chitosan is used as flocculant for the flocculation and sedimentation of Chlorella vulgaris. A cell separation efficiency above 96 % is obtained with chitosan dosage at 5 mg/L. The sedimentation rate of cell flocs goes up to 456 cm/h when 1 g/L of silica is embedded into the cell flocs, which is about 6 times faster than that of without silica. Results proved that the embedding strategy improves the method of flocculation and sedimentation effectively in term of cell separation duration. This method is proven feasible for fishpond water treatment by removing up to 94 % of microalgae from fishpond water at sedimentation rate of 250 cm/h, which is 23 times faster. Moreover, it showed the abilities to remove 99 % of nitrate, 88 % of ortho-phosphate, 98 % of turbidity, 99 % of Biochemical Oxygen Demand and 85 % of Total Suspended Solid from the fishpond water. This strategy is proven to be a potential one pot solution to remove microalgae from fishpond water and treat the fishpond water simultaneously.