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.