Mass propagation of algae in raw water has been known related to disturbing the flocculation in drinking watertreatmentsystems. Many researchers proposed that algal organic matters (AOMs) can interact with flocculants by coordinate bonds, and bring about several disorders due to increases in flocculant demand and in the residual flocculant in treated water. However, the inhibitory mechanism by AOMs have not been elucidated In this study, alminium-complexing substances in AOMs were successfully isolated with affinity chromatography. SDS-PAGE analysis revealed that these substances include proteins which have molecular weight between 40 and 70kDa. However, the results of the gel chromatography show that the amount of these proteins in AOMs were estimated to be very low compared to organic matters with high molecular weights around 2000kDa. These results imply that not only proteins but also other organic matters such as polysaccharides contribute to the inhibition of flocculation.
