Aspergillus oryzae, a novel eco-friendly fungal bioflocculant for turbid drinking water treatment

The residuals of aluminum (Al), iron (Fe), and acrylamide are always present when traditional inorganic coagulants and organic polyacrylamide flocculants are used, causing environmental security problems. Nevertheless, most microbial flocculants are nontoxic, cause no secondary pollution, and easily biodegrade, and thus efficient and eco-friendly bioflocculants are valuable. Herein, Aspergillus oryzae, a food fermentation fungus, was cultured and developed as a bioflocculant for turbid drinking water treatment. The physical and chemical structures of A. oryzae was characterized, and flocculation performance was evaluated in turbid drinking water treatment. Flocculation efficiency of 91.09% was obtained in the fungal pellets at a culture time of 72 h, flocculant dosage of 3.2 g/L, and pH of 5.0. More than 85% flocculation efficiency was achieved in a wide pH range from 4.0 to 9.0. The removal mechanism was investigated through zeta potential, field emission scanning electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. Results showed that functional groups, such as hydroxyl, amide, and carboxyl, in the metabolites secreted by the fungal pellets contributed to the flocculation process through adsorption. Zeta potential analysis indicated that electrostatic force contributed a positive effect. Fungal hyphae can be directly used as bioflocculants rather than fungal metabolites. This feature is favorable and convenient to drinking water treatment.

Automated summary

This study found that using Aspergillus oryzae as a bioflocculant can effectively treat turbid drinking water, with high efficiency, environmental friendliness, and convenience. Aspergillus oryzae achieves flocculation by secreting metabolites, and it is adaptable to a wide range of pH levels.