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Low nitrogen (N) removal efficiency limits the potential of microalgae technology for the treatment of high nitrogen and low carbon rare earth tailings (REEs) wastewater. In this study, waste corncob was utilized as a biocarrier immobilizing Chlamydopodium sp. microalgae to realize high-efficient treatment of the REEs wastewater. In only 2.5 d, corncob-immobilized microalgae allowed the residual concentrations of N lower than the emission standards, and ammonia nitrogen (NH 4 +-N) removal rate is 83.3 mg L−1·d−1, total inorganic nitrogen (TIN) removal rate is 86.7 mg L−1·d−1, which was 18.5 times that of the previously-reported microalgae (4.68 mg L−1·d−1). Compared with other microalgae immobilization carriers, corncob possesses the ability to release available carbon sources for microalgae. Composition analysis and sugar verification experiments showed that the main content of TOC released by corncob was monosaccharide, and in a certain range, the removal rate of N was positively correlated with the TOC concentration. The utilization of biomass wastes with dual functions as biological carriers has great potential to improve the performance of microalgae, and is conducive to the development of engineering applications. [Display omitted] • Rapid removal of NH 4 +-N and TIN by microalgae was achieved in REEs wastewater. • The removal efficiency of TIN can reach 100%, and rate can reach 86.7 mg L−1·d−1. • The removal rate of N by corncob-immobilized microalgae reached the highest. • Corncob possess dual functions of biocarrier and available carbon source. [ABSTRACT FROM AUTHOR]

Low C/N municipal wastewater is difficult to be treated effectively via traditional biological methods, leading to concentrations of pollutants in effluent far exceeding increasingly strict standards. In this work, we propose a novel microalgae-bacteria tandem-type process to simultaneously remove ammonia nitrogen (NH 4 +-N) and phosphorus (P) from municipal wastewater. A 4.5 L microalgae-bacteria tandem-type reactor was constructed and operated stably for 40 days. The removal efficiencies of NH 4 +-N and P reached 97.5% and 92.9%, respectively, effluent concentrations were 0.53 and 0.17 mg/L on average, which met the Environmental quality standards for surface water in China (GB 3838–2002). Remarkably, microalgae ponds accounted for 69.3% and 76.3% of the overall NH 4 +-N and P removal via microalgae assimilation. Furthermore, 16 S rRNA gene amplicon sequencing revealed the abundance of bacteria changed, suggesting that the presence of microalgae leads to some species extinction and low-abundance bacteria increase. This work demonstrated that the microalgae-bacteria tandem-type processes can be efficient and widely applied in the advanced treatment of municipal wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]