Biodegradation of anaerobic effluent containing 1,4-dioxane and heavy metals via auto-aerated down flow hanging luffa (ADHL) system was extensively investigated. The oxygen was naturally supplied to the consortium bacterium through windows located along the reactor height creating favorable aerobic conditions. The bioreactor efficiently removed 1,4-dioxane and total chemical oxygen demand (CODt) from anaerobic effluent without significant inhibitory effects. Removal efficiencies of CODt and 1,4-dioxane were significantly increased from 31.3 +/- 10 to 59.5 +/- 5.9% and from 43.7 +/- 11.9 to 90 +/- 4.9% at increasing the hydraulic retention time (HRT) from 5.7 to 17.3 h, respectively. Moreover, ADHL system was very effective for removal of heavy metals (Cr6+, Cu2+, Fe3+, Mn2+, Ni2+) where the extracellular polymeric substances (EPS) concentrations were quite high and amounted to 12.3 +/- 1.3 g/g biomass at an HRT of 17.3 h. The nitrification efficiency was 3.0, 46.8 and 56.3% at HRTs of 5.7, 11.5 and 17.3 h, respectively. Batch experimental results showed that the key removal mechanism of 1,4-dioxane was adsorption followed by biodegradation process. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.