Influence of Methylation and Polymerization on Flocculant Properties of Bovine Blood

Flocculants are used in the primary step of wastewater treatment to precipitate solids. Bovine blood is a slaughterhouse byproduct, and there is limited evidence in the literature demonstrating that it can be used as a flocculant. In this study, native bovine blood (NBB) and three types of chemically modified blood (methylated bovine blood (MeBB), polymerized bovine blood (PolyBB), and polymerized & methylated bovine blood (PMBB)) were tested against suspensions of negatively charged kaolin or positively charged hematite. The methylation reaction had the expected effect of increasing the apparent isoelectric point of MeBB and PMBB relative to that of the NBB starting material, and the polymerization reaction had the intended effect of increasing the average molar mass. NBB and PolyBB performed well with kaolin suspensions at pH ≤5.5, and MeBB showed high and consistent performance, across the pH range of 4.5-8.5. Relative to NBB, MeBB had improved potency and pH independence but also the disadvantage of increased sensitivity to overdosing. The performance of PolyBB was very similar to that of NBB. PMBB had performance enhancements similar to those of MeBB, with a modest improvement in its overdose sensitivity. The performances of MeBB and PMBB with hematite suspensions were poor at all tested doses (2-100 mg/g hematite), whereas a 30 mg/g dose of PolyBB showed 81% precipitation in an hour. The results show that simple chemical treatments can improve the utility of blood as a flocculant for negatively charged solids.