Microbial Ecology of Granular Biofilm Technologies for Wastewater Treatment: A Review

Strength under pressure: Aerobic granular sludge (AGS) dynamics in sequencing batch reactors exposed to per- and polyfluoroalkyl substances (PFAS)

This study investigated the capacity of aerobic granular sludge (AGS) to remove per- and polyfluoroalkyl substances (PFAS). Over 247 days, AGS in two sequencing batch reactors (R1-CTRL and R2-PFAS) was tested with synthetic wastewater containing four representative PFAS compounds (PFPeA, PFOA, PFBS, PFDS) chosen for their diverse properties, including chain length and hydrophobicity. The PFAS-acclimated reactor (R2-PFAS) exhibited greater resilience and improved performance compared to the control (R1-CTRL). Both reactors achieved > 95 % removal of chemical oxygen demand (COD), ammonia, and phosphate, despite PFAS concentrations reaching 500 µg L-1. However, R1-CTRL experienced declines in biomass and settleability, while R2-PFAS maintained stability and a more consistent extracellular polymeric substances (EPS) profile, suggesting tolerance to PFAS. PFAS removal varied by compound. Nearly 100 % removal efficiency was achieved for PFDS, while PFPeA, PFBS, and PFOA showed variable results (- 71 % to 93 % in R1-CTRL; - 17 % to 100 % in R2-PFAS). The findings demonstrate AGS as a promising tool for PFAS removal, particularly when biomass is acclimatized during granulation. This approach could enhance wastewater treatment efficiency and effluent quality.

Unveiling the capacity of bioaugmentation application, in comparison with biochar and rhamnolipid for TPHs degradation in aged hydrocarbons polluted soil

Persistent, aged hydrocarbons in soil hinder remediation, posing a significant environmental threat. While bioremediation offers an environmentally friendly and cost-effective approach, its efficacy for complex contaminants relies on enhancing pollutant bioavailability. This study explores the potential of immobilized bacterial consortia combined with biochar and rhamnolipids to accelerate bioremediation of aged total petroleum hydrocarbon (TPH)-contaminated soil. Previous research indicates that biochar and biosurfactants can increase bioremediation rates, while mixed consortia offer sequential degradation and higher hydrocarbon mineralization. The present investigation aimed to assess whether combining these strategies could further enhance degradation in aged, complex soil matrices. The bioaugmentation (BA) with bacterial consortium increased the TPHs degradation in aged soil (over 20% compared to natural attenuation - NA). However, co-application of BA with biochar and rhamnolipid higher did not show a statistically prominent synergistic effect. While biochar application facilitated the maintenance of hydrocarbon degrading bacterial consortium in soil, the present study did not identify a direct influence in TPHs degradation. The biochar application in contaminated soil contributed to TPHs adsorption. Rhamnolipid alone slightly increased the TPHs biodegradation with NA, while the combined bioaugmentation treatment with rhamnolipid and biochar increased the degradation between 27.5 and 29.8%. These findings encourage further exploration of combining bioaugmentation with amendment, like biochar and rhamnolipid, for remediating diverse environmental matrices contaminated with complex and aged hydrocarbons.