Biopolymer Flocculants and Oat Hull Biomass To Aid the Removal of Orthophosphate in Wastewater Treatment

This study reports on the removal of orthophosphate (P_i) by coagulation–flocculation with variable combinations of alum, biopolymers, and biomass. The combinatorial effects of these coagulant aids were evaluated for single, binary, and ternary systems. The role of pH, component dosages, and P_i concentration on the coagulation–flocculation efficacy was evaluated. There was an optimal dosage of alum (30 mg/L) while alginate and chitosan were 15 mg/L. P_i removal was 86% for alum and 98% for ternary systems containing chitosan and alginate where [P_i] = 10–11 mg P_i/L. P_i removal for the alum–alginate–chitosan ternary system was more efficient than that for the binary systems, especially at pH 6–7, where reduced efficiency occurred at pH > 7.5. P_i removal was independent of concentration except at lower levels, [P_i] < 10 mg/L. The alum–refined oat hull binary system was 99% effective for P_i removal, especially when [P_i] = 25 mg/L, with greater removal over the use of oat hulls alone