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

Abstract

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 (N2O) 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 N2O emission (around 0.7 % of influent total nitrogen). Period II was also characterized by a lower carbon footprint, 1.6 and 1.9 kgCO2eq 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).