Long-term impact of heavy metals on the performance of biological wastewater treatment processes during shock-adaptation-restoration phases.

•Shock-adaptation and restoration phases were considered.•Ag+ led to significant increment of biopolymers and relative hydrophobicity.•Cu2+ and Hg2+ severely affected the key enzymes of microorganisms’ metabolism.•Cu2+ irreversibly damaged the cells’ integrity and diversity of microorganisms.