Feasibility of tubing two-phase bioreactors for biological treatment of high toxicity landfill leachate

This study describes the performance of a two-phase tubing bioreactor operated with an extractive polymeric membrane able to selectively transfer and biologically remove the toxic fraction of an industrial/hazardous waste landfill leachate. An additional feature of this bioreactor is the separation of the biomass from the polluted stream with consequent marked reduction of the inhibitory/toxic effect exerted by leachate constituents. Process performance has been optimized for decreasing HRTs, from 5.5 to 1.9 h, and step-increased OLRs, from 300 to 900 gCOD/L d with excellent removal efficiencies (88-99%). Removal rates of toxic chemicals, represented by phenolic compounds, as well as mass transfer and biomass activity, were not negatively affected by severe loading conditions. On the contrary, the trend of oxygen consumption rate suggested increased activity of the microorganisms with raised loads. Furthermore, biodegradation efficiency of 90% has been observed by eval-uating the final mass balance after washing the polymer, which retained only 1.5% of totally fed phenolics. This work provided reliable results to conclude that the tested tubing bioreactor is an effective and stable treatment technology ready for commercial application, with evident operating advantages and the possibility to recover concurrently other valuable leachate constituents as VFAs and ammonia.