Characteristics of a bioflocculant produced by a consortium of Cobetia and Bacillus species and its application in the treatment of wastewaters

Abstract

The characteristics of a bioflocculant produced by a consortium of 2 bacteria belonging to the genera Cobetia and Bacillus was investigated. The extracellular bioflocculant was composed of 66% uronic acid and 31% protein and showed an optimum flocculation (90% flocculating activity) of kaolin suspension at a dosage of 0.8 mg/mℓ, pH of 8, and with Ca2+ as a coagulant aid. The bioflocculant is thermally stable, with a high residual flocculating activity of 86.7%, 89.3% and 87% after heating at 50°C, 80°C and 100°C, respectively, for 25 min. FTIR analysis of the bioflocculant indicated the presence of hydroxyl, amino, carbonyl and carboxyl functional groups. Scanning electron microscopy (SEM) revealed a crystal-linear sponge-like bioflocculant structure and EDX analysis of purified bioflocculant indicated an elemental composition in mass proportions of C:N:O:S:P of 6.67:6.23:37.55:0.38:4.42 (% w/w). The produced bioflocculant was highly efficient in removing turbidity and reducing chemical oxygen demand (COD) in brewery wastewater, dairy wastewater and river water. The bioflocculant could flocculate kaolin clay more efficiently than traditional flocculants; alum and polyethylenimine.