Effect of bioavailability on the fate of hydrophobic organic compounds and metal in treatment of young landfill leachate by membrane bioreactor

•COD rather than ammonium, is the main concern of landfill leachate treatment processes.•Dependence of DEHP removal efficiency on sludge adsorption and membrane retention.•DEHP biodegradation rate in sludge determine by its bioavailability.•Lower metal removal efficiency in presence of humic acid.

Complex dissolved organic matter (DOM) present in landfill leachate provides reliable media for adsorption of highly hydrophobic contaminants, such as Di 2-ethyl hexyl phthalate (DEHP). In this research, the feasibility of submerged membrane bioreactor (SMBR) for treatment of landfill leachate (LFL) was determined. Later, the operating conditions were optimized for removal of DEHP, COD, NH4+ and PO43−, and finally the effect of bioavailability was examined by introduction of different concentrations of humic acid into the influent. The result revealed that presence of complex agglomerated organic compounds increased the removal efficiency of DEHP and COD, even though DEHP biodegradation rate in sludge dramatically decreased (from 58.8% to 12.8%). MBR retention of different metals in the absence and in the presence of recalcitrant DOM was also studied. Like DEHP, ternary interaction between metals, DOM, and sludge play a pivotal role in their removal efficiency and their concentration in sludge.