Valorizing Biowaste for Wastewater Treatment: Dewatering Sludges Using Specified Risk Material-Based Flocculants for Industrial Sustainability

Abstract

Sludges, particularly clay-enriched fluid tailings, are major waste streams disposed from mining and mineral processing industries. To improve the separation of sludges into water and stackable solids, a novel flocculant was developed in this study using peptides from specified risk materials (SRMs), a proteinaceous waste from animal rendering industries; the synthesis was accomplished with polyamidoamine epichlorohydrin (PAE) in a one-pot aqueous reaction. Settling tests using standard kaolinite suspensions showed that compared to a petrochemical-based flocculant (hydrolyzed polyacrylamide, HPAM) widely used in the current mining industry, the SRM-based flocculant achieved a similar settling rate but a more complete ultimate dewatering (sediment volume reduced by 47.5%). Unlike HPAM, the performance of the novel flocculant did not require gypsum, a common industrial processing aid that could be detrimental to downstream processing. Interfacial and particle size analyses revealed that the peptide–PAE materials adsorbed at kaolinite surfaces through electrostatic interactions, reduced the fine solids’ net surface charge (ζ from −40 to −15 mV), and facilitated rapid aggregations of these highly suspended solids. Overall, this proof-of-concept study demonstrates the great potential of using a waste protein-based flocculant to address intractable waste sludge challenges for industrial sustainability as well as reduced environmental footprints.