Harvesting colonial Microcystis flos-aquae using two-stage filtration: Influence of pre-filtration on harvesting performance

[Display omitted] •Pre-filtration with a 20 μm screen improved harvesting rate by 25%.•Pre-filtration changed size distribution and concentration of colonial Microcystis.•Larger colony size or narrower size distribution resulted higher harvesting rate.•Harvesting rate increased with cellular concentration initially and then decreased.•Influences of size distribution and concentration were predicted by a MLR model. The harvesting of bloom-forming colonial Microcystis flos-aquae using filtration helps with bloom control, the acquisition of a biomass resource and nutrient removal from eutrophic lakes. In this study, two-stage filtration of three combinations for M. flos-aquae harvesting was investigated, and the main factors affecting two-stage filtration performance were analysed. The results showed that compared with filtration with a 5 μm membrane alone, pre-filtration with a 20 μm screen improved biomass harvesting rate by 25.03% while 200 μm and 550 μm screens pre-filtrations resulted in decreases of 26.90% and 42.20%, respectively. The influences of colony size distribution and cellular concentration on filtration performance were predicted well using a multiple linear regression model (MLR). According to the model analysis, filtrate with larger colony size and narrower size distribution resulted higher harvesting performance. As the cellular concentration increased, the averaged flux decreased, while biomass harvesting rate increased initially, reached the highest value and then decreased. These results could be applied for the development of efficient filtration harvesting strategies for Microcystis bloom control.