Effect of asparagine, corncob biochar and Fe(II) on anaerobic biological treatment under low temperature: Enhanced performance and microbial community dynamic

To ensure the efficiency of anaerobic biological treatment technology at lower temperature will expand the application of anaerobic reactor in practical industrial wastewater treatment. Through a batch experiment, asparagine, corncob biochar and Fe2+ were selected as strengthening measures to analyze the effects on the anaerobic sludge characteristics, microbial community and functional genes in the low temperature (15 °C). Results showed that after 21 days, asparagine began to promote chemical oxygen demand (COD) removal by the anaerobic treatment, with highest COD removal rate (81.65%) observed when the asparagine concentration was 1 mmol/L. When adding 3 g biochar, 25 mg/L Fe2+, and the combination of biochar and Fe2+, the COD removal rates reached to 82%, 92% and 97%, respectively. In the presence of asparagine, both biochar and Fe2+ alone or in combination increased the activity of protease (16.35%–120.71%) and coenzyme F420 (5.63%–130.2%). The relative abundance of Proteobacteria and Methanobacterium increased in the presence of biochar and Fe2+. In addition, the KEGG results showed that the combined addition of biochar and Fe2+ enhanced bacterial replication and repair and promoted amino acid metabolism of archaea. [Display omitted] •Strengthening of a low-temperature anaerobic treatment process was evaluated.•Asparagine began to promote COD removal at asparagine 1 mmol/L.•Biochar and Fe(II) increased the activity of protease and coenzyme F420.•Biochar and Fe(II) enhanced bacterial amino acid metabolism.