<p>The treatment of municipal wastewater has become a significant challenge due to its intricate composition and low carbon-to-nitrogen ratio. In order to meet the discharge standards, a large amount of energy is consumed. In this context, the incorporation of microalgae into the conventional activated sludge process has become a promising strategy for low-carbon denitrification. This study aims to integrate research on algal–bacterial symbiotic systems with biofilm technology to enhance energy-efficient nitrogen removal in municipal wastewater treatment. Through comprehensive analysis, this paper elucidates (1) the developmental dynamics of algal–bacterial symbioses, (2) the process of combining algal–bacterial symbiotic systems with biofilm systems, (3) the fundamentals and operational determinants of algal–bacterial symbiotic membrane systems, and (4) the potential applications in sustainable water treatment. The proposed hybrid system demonstrates significant potential for carbon–neutral wastewater treatment through synergistic pollutant degradation, offering an innovative approach to address critical challenges in environmental sustainability and water resource management.</p> Graphical abstract <p></p>