Uncovering the flocculating potential of extracellular polymeric substances produced by periphytic biofilms

The aim of this work was to study the characteristics and flocculating properties of extracellular polymeric substances (EPS) extracted from periphytic biofilms. The periphytic EPS, with an extracted yield of 491.8 mg/g, were mainly composed of hetero-polysaccharides and proteins, and the elements C1s, N1s, and O1s. Polysaccharides represented 53.28% of the periphytic EPS. Proteins constituted 20.26% of the EPS, and contributed to at least 34.65% of the total flocculating activity. The periphytic EPS showed high turbidity removal capacity (86.76 ± 1.52%, 10 min) and efficient aniline blue (AB) removal capacity (56.46 ± 1.41%, 30 min). The mechanism of AB removal by the periphytic EPS seemed to be a combined technique of “adsorption-flocculation”. This study reveals the flocculating capability of periphytic EPS, and suggests that periphytic biofilms are novel sources for bioflocculants preparation.