Insights into the azo dye decolourisation and denitrogenation in micro-electrolysis enhanced counter-diffusion...

In this study, electron transport pathways were activated and diversified by coupling counter-diffusion biofilms with micro-electrolysis for Alizarin yellow R (AYR) denitrogenation. Due to the binding of AYR to two residues of EC 4.1.3.36 with higher binding energy, the expression of EC 4.1.3.36 was down-regulated, causing the EC 3.1.2.28 and EC 2.5.1.74 for menaquinone synthesis (redox mediator) undetectable in Membrane aerated biofilm reactors (MABR). Spontaneous electron generation in the micro electrolysis-coupled MABR (ME-MABR) significantly activated two enzymes. Activated menaquinone up-regulated decolourisation related genes expression in ME-MABR, including azoR (2.12 log₂), NQO1 (2.97 log₂), wrbA (0.45 log₂), and ndh (0.47 log₂). The diversified electron flow pathways also promoted the nitrogen metabolism coding genes up-regulation, accelerating further inorganic nitrogen denitrogenation after AYR mineralisation. Compared to MABR, the decolourisation, mineralisation, and denitrogenation in ME-MABR increased by 25.80 %, 16.53 %, and 13.32 %, respectively. This study provides new insights into micro-electrolysis enhanced removal of AYR.