Optimum conditions to treat high-concentration microparticle slime water with bioflocculants

We studied how bioflocculants, produced by white-rot fungi, affect flocculation in slime water. Based on a test in an orthogonal design, flocculation conditions were optimized. The results show that flocculation activity is at its highest when the following conditions are met: slime water concentration 27.42 g/L; coagulant aid (CaCl2) mass concentration 5.0 g/L; two-segment stirrings: the first at a stirring speed of 60 r/min for 180 s and the second 180 r/min for 60 s; a pH of 11 and a flocculant concentration of 15 mL/L. The flocculation activity can be up to 98.71% of bioflocculants at the time. Further experiments indicate that most of the flocculation active material is found outside the mycelium cells. This is the extracellular secretion produced by mycelium cells during the fermentation process. This flocculant has strong thermal stability. Many kinds of cations have a flocculation function to assist bioflocculants. This aid-flocculation effect of the divalent cation Ca2+ is obvious in the bioflocculant produced by the white-rot fungus. Therefore, this is of great value when applied to control engineering in the battle against water pollution.