Pyrrhotite promote aerobic granular sludge formation in dye wastewater: pH, interfacial free energy, and microbial community evolution

This study introduces a technique utilizing natural pyrrhotite powder as a nucleating agent in four sequencing batch reactors (SBRs) for the treatment of dye wastewater. Through analysis of various factors including pH, pyrrhotite surface free energy, sludge zeta potential, and shifts in microbial communities, the mechanism by which pyrrhotite facilitates the formation of aerobic granular sludge (AGS) is elucidated. Over 140 days of continuous operation under neutral conditions, natural pyrrhotite rapidly cultivated AGS under neutral conditions. The structure of the sludge was compact and the settling properties were satisfactory (SVI₃₀/SVI₅ close to 1). Reductions in both sludge zeta potential and interfacial free energy of pyrrhotite correlated with increased hydrophobicity of AGS, leading to enhanced sludge aggregation. Changes in pH, sludge interfacial free energy, and zeta potential were found to influence the microbial community composition and diversity within the sludge.This study provides a novel approach for dye wastewater treatment.