Synergistic remediation of phenanthrene-cadmium co-contaminants by an immobilized acclimated bacterial-fungal consortium and its community response.

Bioremediation has tremendous potential to mitigate the serious threats posed by polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs). In the present study, nine bacterial-fungal consortia were progressively acclimated under different culture conditions. Among them, a microbial consortium 1, originating from activated sludge and copper mine sludge microorganisms, was developed through the acclimation of a multi-substrate intermediate (catechol)-target contaminant (Cd2+, phenanthrene (PHE)). Consortium 1 exhibited the best PHE degradation, with an efficiency of 95.6% after 7 d of inoculation, and its tolerance concentration for Cd2+ was up to 1800 mg/L within 48 h. Bacteria Pandoraea and Burkholderia-Caballeronia-Paraburkholderia, as well as fungi Ascomycota and Basidiomycota predominated in the consortium 1. Furthermore, a biochar-loaded consortium was constructed to better cope with the co-contamination behavior, which exhibited excellent adaptation to Cd2+ ranging of 50-200 mg/L. Immobilized consortium efficiently degraded 92.02-97.77% of 50 mg/L PHE within 7 d while removing 93.67-99.04% of Cd2+. In remediation of co-pollution, immobilization technology improved the bioavailability of PHE and dehydrogenase activity of the consortium to enhance PHE degradation, and the phthalic acid pathway was the main metabolic pathway. As for Cd2+ removal, oxygen-containing functional groups (-OH, C=O, and C-O) of biochar or microbial cell walls and EPS components, fulvic acid and aromatic proteins, participated through chemical complexation and precipitation. Furthermore, immobilization led to more active consortium metabolic activity during the reaction, and the community structure developed in a more favorable direction. The dominant species were Proteobacteria, Bacteroidota, and Fusarium, and the predictive expression of functional genes corresponding to key enzymes was elevated. This study provides a basis for combining biochar and acclimated bacterial-fungal consortia for co-contaminated site remediation.

Synergistic PAH biodegradation by a mixed bacterial consortium: based on a multi-substrate enrichment approach.

Polycyclic aromatic hydrocarbon (PAH) contamination in the environment involves multiple PAHs and various intermediates produced during the microbial metabolic process. A multi-substrate enrichment approach was proposed to develop a mixed bacterial community (MBC) from the activated sludge of a coking wastewater plant. The degradation performance of MBC was evaluated under different initial concentrations of PAHs (25-200 mg/L), temperature (20-35 °C), pH (5.0-9.0), salinity (0-10 g/L NaCl), and coexisting substrates (catechol, salicylic acid, and phthalic acid). The results showed that the degradation rates of phenanthrene and pyrene in all treatments were up to (99 ± 0.71)% and (99 ± 0.90)% after incubation of 5 days, respectively, indicating excellent biodegradation ability of PAHs by MBC. Furthermore, 16S rRNA gene amplicon sequencing analysis revealed that Pseudomonas was dominant, while Burkholderia had the largest proportion in acidic (pH = 5.0) and saline (10 g/L NaCl) environments. However, the proportion of dominant bacteria in MBC was markedly affected by intermediate metabolites. It was shown that MBC had a higher degradation rate of PAHs in the coexisting matrix due to the timely clearance of intermediates reducing the metabolic burden. Overall, our study provided valuable information to help design an effective strategy for the bioremediation of PAHs in complex environments.

Adsorption of direct yellow brown D3G from aqueous solution using loaded modified low-cost lignite: Performance and mechanism.

Low-cost lignite-based, copper-containing adsorbents (Cu-raw) were developed through a simple ultrasonic impregnation protocol for enhanced adsorption of direct yellow brown D3G (DYB) from aqueous solutions while treating copper-containing wastewater. The adsorbent was characterized by X-ray diffraction (XRD), scanning electron microscopy-energy dispersion spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption isotherms and kinetics were studied, and the factors that affect the adsorption, such as adsorbent dosage and solution pH, were investigated. The results showed that DYB adsorption was highly pH dependent and the isotherm of adsorption could be well described by the Langmuir-Freundlich model and the maximum DYB adsorption capacity was estimated to be 369 mg/g at 25°C. The electrostatic and chelating interactions were the main interfacial interaction mechanism, and the synergetic removal performance of lignite toward cationic metal ions and anionic dye was shown. The kinetic data were well fitted to the pseudo-second-order equation, indicating that chemical sorption was the rate-limiting step. The findings reported in this work highlight the potential of using lignite as an effective low-cost adsorbent for the removal of organic pollutants from wastewater.