CuO nanoparticles as surface additives for membranes in anaerobic digestate treatment applications

Application of CuO nanoparticles (NPs) deposited via sonochemical synthesis onto polyethersulfone (PES) ultrafiltration membranes for fouling mitigation in anaerobic digestate treatment was investigated. Modified membranes were prepared at three sonication intensities (45%, 66% and 95%) and evaluated alongside with unmodified samples using anaerobic digestate from a pilot-scale AnMBR under continuous and intermittent operation with reverse flow cleaning. Surface characterization was performed through XPS, FTIR, HRSEM and ICP-OES. The CuO NPs coating on the PES membrane was 0.11%, 0.65% and 0.90% w/w at sonication intensities of 45%, 66% and 95%. Under constant input flux conditions, transmembrane pressure decreased with increasing coating intensity, indicating progressive reduction in hydraulic resistance. Coated membranes exhibited moderately lower average flux reduction (62.1–62.6%) compared to the unmodified membrane (67.5%), though differences were within experimental uncertainty. When membrane performance was evaluated based on pressure-normalized permeability, the 66% and 95% coated membranes demonstrated 18.5% and 20.8% increased permeability compared to the unmodified membrane. These findings support CuO surface modification at moderate sonication intensity as an efficient antifouling strategy for anaerobic membrane digestion systems.