This study investigated the influences of cetyltrimethyl trimethyl ammonium chloride (CTAC), an emerging pollutant quaternary ammonium compound (QAC) in municipal effluents, on the transfer and uptake of NH4+ by Chlorella vulgaris F1068 cells removed EPS artificially (EPS-R) and coated EPS naturally (EPS-C) under different scenarios (e.g., the presence or absence of CTAC, different photoperiod sequences (light 12 h: dark 12 h or dark 12 h: light 12 h)). The results showed that the removal of EPS increased the transfer and uptake of NH4+ but the presence of EPS caged NH4+ and effectively weakened the stress of CTAC (<0.5 mg/L) on NH4+ uptake. The main mechanism was considered that CTAC in the concentration range from 0.1 to 0.5 mg/L induced an increased amount of polysaccharide and protein in EPS and thus protected algal normal physiological functions (including cell membrane permeability and glutamine synthetase activity) from the damage of CTAC (0.1 to 0.5 mg/L) regardless of the photoperiod sequences. Thereby, the findings of this study provided an insight into the role of algal EPS in transfer and uptake of nutrients under the coexisted toxics for the future algae-based sewage treatment application. (C) 2018 Published by Elsevier B.V.