A systematic evaluation of alkaliphilic microbial consortia from a soda lake for the biodegradation of cyanide-rich wastewater

Alkaliphilic microorganisms are one option for the treatment of cyanide-polluted wastewater. This study reports the degradation of cyanide from simulated gold mine wastewater using alkaliphilic microbial consortia harvested from a soda lake, Lake Chitu, Ethiopia. A novel aerobic-anoxic integrated treatment setup was established for the treatment process. Colorimetry was used to measure residual cyanide concentration, and 16S rRNA amplicon gene sequencing was used to study microbial diversity. This treatment system was able to degrade 97.49 ± 0.12% of 200 mg/L sodium cyanide. However, changes were observed (p < 0.05) when the established consortia were stressed with heavy metals. About 28 % of the initial inoculum persisted until the end of the treatment days. Twenty-eight bacterial phyla were identified, with Firmicutes, Proteobacteria, and Bacteroidota being the most abundant. At the end of the treatment process, Alkalibacterium (74.43%), Exaguobacterium (6.6%), and Halomonas (3.89%) were dominant. These findings indicate that alkaliphilic microbial consortiums from Ethiopian Rift Valley soda lakes are effective for the treatment of cyanide-polluted wastewater. • An integrated aerobic-anoxic treatment setup is effective for cyanide waste treatment. • Ethiopian Rift Vally soda lakes provided important cyanide-degrading bacteria. • Amplicon sequence variance (402–435 bp) was used to assess microbial diversity. • Alkalibacterium and Halomonas were the most prevalent genera in the reactors. • The consortia achieved over 97% degradation of 400 mg/L cyanide.