Response of methanogenic system to long-term polycyclic aromatic hydrocarbon exposure: Adsorption and biodegradation, performance variation, and microbial function assessment.

Phenanthrene (PHE) as a typical polycyclic aromatic hydrocarbon (PAH) is prevalent and harmful to organisms in petroleum-polluted sites. The effects of PHE concentration levels on performance, microbial community and functions in methanogenic system were comprehensively investigated by an operation of UASB reactor (198 days) and a series of batch tests. The results found that PHE was prone to accumulate in reactor by sludge adsorption (Final concentration = 12.53 mg/g TS Sludge), which posed significant influences on methanogenic system. The removal of chemical oxygen demand (COD), NH4+-N and volatile fatty acids (VFAs) in reactor were reduced with PHE accumulation. Meanwhile, microbes with higher ATPase secrete more EPS activity to self-protect against PHE toxicity. Sequencing analysis showed that PHE interfered significantly diversity and structure of microbial community. For bacteria, PHE was toxic to Bacteroidetes and Latescibacteria, while syntrophs (f_Syntrophaceae, Syntrophorhabdus, etc.) involved in VFAs oxidation and aromatic organics degradation were tolerant of PHE stress. For archaea, acetoclastic methanogens (Methanosaeta) abundance was continuously diminished by 45.1% under long-term PHE exposure. Further functions analysis suggested that microbial community accelerated amino acid metabolism, energy metabolism and xenobiotics biodegradation & metabolism to satisfy physiological demanding under PHE stress. Combining batch tests of methanogenic metabolism proved that acetoclastic methanogenesis was negatively affected by PHE due to inhibition of functional enzymes (acetate kinase, phosphate acetyltransferase, etc.) expression. These findings may provide the basis for enhancing bioremediation of PAH pollution in anaerobic environment.

Removal behaviors and mechanisms for series of azo dye wastewater by novel nano constructed macro-architectures material.

A novel macro-architectures material Fe3O4-N-GO@sodium alginate (SA) gel film was successfully produced, which was used to remove series azo dye wastewater. The optimal adsorption rates were attained, which achieved the maximum removal efficiency of 74.22%, 45.72%, 37.75% for Congo Red, Acid Orange 7 and Amino Black 10B respectively, under the condition that the mass ratio of Fe3O4-N-GO to sodium alginate was 0.11. The optimal adsorption temperature for three dyes was 30 ℃ and the adsorption equilibrium was reached at 150 min. The adsorption kinetic model of Fe3O4-N-GO@SA for the three azo dyes conformed to the quasi-second-order reaction model, and the adsorption isotherm was more in line with the Freundlich adsorption. The adsorption mechanism was multi-layer heterogeneous adsorption under the combined action of physical adsorption and chemisorption, and chemisorption was the main step of controlling the speed. The study would provide theoretical basis for the application of macro-architectures material in environment.