Short-term and long-term effects of Zn (II) on the microbial activity and sludge property of partial nitrification process

•Zinc ion performed significant effect on partial nitrification.•The suppression threshold on AOB bioactivity of short-term Zn (II) was 10mgL−1.•The suppression threshold on AOB bioactivity of long-term Zn (II) was 50mgL−1.•AOB in PN sludge had self-adaption and tolerance to the Zn (II).•PN sludge presented profitable absorption ability for zinc ion. Autotrophic nitrogen removal was an innovative and economical nitrogen removal technology with less oxygen and no organics consumption, in which partial nitrification (PN) is the key component. It is necessary to clear the impact of metal ions on PN since the development of industry increased their opportunity for entering into wastewater. In this study, PN process was successfully started-up in an SBR, the short-term and long-term effects of Zn (II) on microbial bioactivity and the sludge adsorption ability for Zn (II) were investigated. Results suggested that low Zn (II) were favorable for AOB bioactivity, while the long-term effect also induced NOB bioactivity. The suppression threshold of Zn (II) on AOB in short-term effect was 10mgL−1, which rose to 50mgL−1 in the long-term effect due to the self-adaption. The PN sludge presented prominent absorbability for zinc and performed a quadratic relation with the Zn (II) concentration.