Investigation of the Agricultural Reuse Potential of Urban Wastewater and Other Resources Derived by Using Membrane Bioreactor Technology Within the Circular Economy Framework

The European Union, as delineated in Regulation (EU) 2020/741, sets forth minimum criteria for the reuse of wastewater and in Directive 86/278/CEE sets the reuse of sewage sludge in agriculture. This study aims to investigate the treated water derived from a pilot plant utilizing membrane bioreactor technology and processing real urban wastewater situated in Granada (Spain) with the quality standards necessary for agricultural reuse. Additionally, the study seeks to evaluate the utilization potential of other resources generated during wastewater treatment, including biogas and biostabilized sludge. The pilot plant operated during four cycles, each with distinct hydraulic retention times (6 and 12 h) and variable mixed liquor concentrations (ranging from 2688 to 7542 mgL−1). During these cycles, the plant was doped with increasing concentrations of emerging contamination compounds (diclofenac, ibuprofen and erythromycin) to test their effect on the resources derived from the treatment. The pilot plant incorporated a membrane bioreactor featuring four ultrafiltration membranes operating continuously, alongside a sludge treatment line operating in batch mode. The findings indicate that the effluent meets the requisite quality standards for agricultural use, aligning with the specifications outlined in European legislation. Additionally, the biostabilized sludge and biogas demonstrate potential for reuse.