Are all membrane reactors equal from an environmental point of view?

Membrane bioreactors are one of the most outstanding and updating technologies applied for the wastewater treatment. Different configurations and combinations of technologies are possible for this purpose. However, not only the treatment capacity has to be proved, but also the environmental performance of the different alternatives has to be evaluated under a holistic approach. Only by doing so, the selected technology will be feasible from technological and environmental perspectives.In this study, the Life Cycle Assessment was applied for the evaluation of four membrane bioreactor configurations of increasing complexity. The main contributors to the environmental impacts evaluated were identical for all the alternatives; that is, electricity use plays an important role in all the impact categories and agricultural application of sewage sludge has also a relevant contribution on toxicity-related categories and acidification potential. The comparison among the different configurations reveals an inverse relationship between the environmental costs associated to the treatment and the complexity of the treatment process.

► LCA was used to compare different configurations of MBR with increasing complexity.
► Energy use and sludge disposal were identified as major environmental hot spots.
► Technological complexity and environmental impact presented an inverse relationship.
► Two additional impact assessment methods validated the robustness of the results.