Application of basalt fibers in a biological contact oxidation reactor for the treatment of landfill leachate

Landfill leachate often has high nitrogen concentration that results in an imbalance of carbon to nitrogen ratio, ultimately affecting the bioremediation potential of the system. This problem may be solved by retrofitting a bio-carrier in a reactor that particularly helps microbial communities to drive the nitrogen cycle. In this study, basalt fiber (BF) was used as a bio-carrier in a conventional biological contact oxidation reactor for the remediation of landfill leachate. The physicochemical parameters namely chemical oxygen demand (COD), ammonium-nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were assessed and compared with a control reactor comprising combination fillers to evaluate the system's performance. The potential role of microorganisms in the remediation process was elucidated by microscopic morphology and microbial community structure analyses via 16S amplicon sequencing. The results showed that the surface of BF promotes the adhesion and proliferation of microorganisms. The abundant microbial genera were potentially involved in the nitrogen cycle such as dokdonella, saccharibacteria general incertae sedis, and Nitrospira. When the hydraulic retention time was 10 h and the dissolved oxygen was 1–2 mg/L, the nitrogen removal efficiency was the highest. Accordingly, the adsorption equilibrium of heavy metals was achieved in a short time which could be attributed to the sorption on biomass. This study concludes that BF application could help alleviate current problems of complex wastewater treatment having low denitrification abilities as a low cost solution.