Recovery of anammox process performance after substrate inhibition: Reactor performance, sludge morphology, and microbial community

•Increasing the substrate concentration helped to improve the reactor tolerance.•In the P2 phase, side reactions impeded the removal of NO2–-N.•Filamentous bacteria, Ca and P synergistically promoted sludge granulation.•Anammox bacteria were reciprocal symbiosis with some heterotrophic bacteria.