Enhanced treatment of fracturing flowback fluids using bioflocculant-modified fly ash cenospheres: Process optimization and mechanism analysis

Hydraulic fracturing produces complex organic wastewater, known as fracturing flowback fluid (FFF), which contains refractory pollutants and poses risks of secondary contamination, thereby challenging conventional treatment methods. This study developed an environmentally sustainable strategy using a microbial flocculant (MBF) synthesized from Bacillus paramycoides YQ1—a strain isolated from FFF—in combination with candelilla wax- modified fly ash cenospheres (CWFACs). Through process optimization, the MBF yield was increased from 4.38 to 5.78 g·L⁻¹ , and its flocculation efficiency improved from 60.06 % to 87.84 %. Under optimal conditions, MBF alone achieved removal rates of 86.67 % for chroma, 81.98 % for suspended solids (SS) removal, and 65.13 % for oil, along with effective degradation of polycyclic aromatic hydrocarbons (PAHs). The integrated MBF-CWFACs system demonstrated enhanced performance, attaining 88.50 % chroma removal, 96.29 % SS removal, and 95.30 % oil removal. Mechanistic analysis revealed synergistic effects between bioflocculation and adsorption processes. This integrated approach offers a sustainable solution for FFF treatment, addressing both process efficiency and environmental safety concerns, providing insights for developing eco-friendly wastewater treatment technologies in the petroleum industry.