Membrane bioreactor and ultrafiltration for water reuse: a pilot scale study on urban wastewater treatment

Water scarcity is an escalating global challenge, exacerbated by population growth, urbanization and climate change. In response, advanced wastewater treatment technologies ensure high-quality effluents suitable for reuse. This study compares two membrane-based approaches regarding a pilot-scale wastewater treatment system operating under intermittent (period I) and continuous aeration (period II) conditions: an Integrated Fixed-Film Activated Sludge (IFAS) system coupled with two parallel effluent streams: (i) a Membrane Bioreactor (line I) and (ii) a conventional activated sludge followed by ultrafiltration (line II). Both configurations were evaluated for carbon, nitrogen and phosphorus removal efficiencies, nitrous oxide (N 2 O) emissions, membrane fouling and overall carbon footprint. Results demonstrated an improvement in the biological carbon removal during period II for both lines, increasing to 74 %. The improved nitrogen removal performance during period II also revealed reduced N 2 O emission (around 0.7 % of influent total nitrogen). Period II was also characterized by a lower carbon footprint, 1.6 and 1.9 kgCO 2 eq day −1 for lines I and II, respectively. The main difference was related to the fouling mechanisms affecting the two membranes, which were caused by the particle distribution of the filtered flow. The membrane-based IFAS system proved efficient in producing water for reuse according to EU regulations (2020/741); however, it must be integrated with specific phosphorus removal strategies to comply with the EU Urban Wastewater Treatment Directive (2024/3019).