Acute impacts of mixed heavy metals and diclofenac on sludge activity and enzyme activity involved with biological nitrogen removal

Abstract

The acute impacts of mixed heavy metals and diclofenac (DCF) on sludge activity and enzyme activity involved with nitrogen removal were investigated. Synergistic inhibition on sludge activity and enzyme activity of nitrification and denitrification was found between divalent copper and DCF, and the inhibition by mixed hexavalent chromium and DCF was antagonistic. Joint divalent zinc and DCF had synergistic effects on sludge activity and enzyme activity in the nitrification process, and they showed antagonistic inhibitions on denitrifying sludge activity and enzyme activity. Metals, DCF and mixed metals/DCF excited reactive oxygen species and lactate dehydrogenase production from activated sludge. Protein in extracellular polymeric substances (EPS) was the main feedback of bacteria to metals, DCF and mixed metals/DCF, and the protein role did not change according to the type of metal or mixture composition. Protein and polysaccharide groups played important roles in the interaction of EPS with metals and DCF.