Extractive polymeric membrane bioreactors for industrial wastewater treatment: Theory and practice

Treatment of industrial wastewaters with current technologies can be very challenging, due to the presence of toxic and persistent compounds and to unfavorable pH conditions, which exert toxic/inhibitory effects on the biomass. Extractive membrane bioreactor (EMB) is a promising technology capable to overcome these diffi culties. The system ensures separation between “hostile” wastewater and the biomass, allowing the gradual release of contaminants in the bioreactor under a concentration gradient, through an absorptive/diffusive membrane. Depending on thermodynamic affinity, the membrane is permeable only to target compounds, thus ensuring a “selective” extraction. In this review, earlier PDMS and newest polymeric membrane reactors have been analyzed, highlighting their potentialities and the still open research issues. The effects of biofilm mation, reactor configuration and operative parameters, such as Hydraulic Retention Time and geometric configuration, have been discussed. Despite good results in terms of contaminants removal, these parameters strongly affect reactor performance and further investigations are necessary. Furthermore, data analysis showed that this technology is ready for upscaling and this step is crucial for a full evaluation of the feasibility of a technology that could bring a remarkable improvement for industrial wastewater treatment.