Monitoring the nitrous oxide emissions and biological nutrient removal from wastewater treatment: Impact of perfluorooctanoic acid.

The impacts of perfluorooctanoic acid (PFOA) on biological nutrient removal and nitrous oxide (NO) emissions have been specifically studied. The experimental results show that PFOA inhibited nitrification, but promoted denitrification and reduced NO emissions without significantly affecting phosphorus removal. The existence of 20 mg/L of PFOA increased total nitrogen removal efficiency from 78.7 ± 6.89 % to 86.8 ± 6.39 % and reduced NO emission factor from 6.02 ± 0.24 % to 4.43 ± 0.10 %. The mechanism studies reveal that microorganisms released extracellular polymeric substances (EPS) under PFOA exposure to protect sludge cells against PFOA toxicity. The generated PFOA-EPS conjugates reduced the nitrification rate, but increased the denitrification rate by regulating the activity of oxidoreductases. In addition, PFOA reduced the activity of polyphosphate accumulating organisms and glycogen accumulating organisms to save carbon source for denitrification, which reduced the electronic competition between reductases, thereby achieving complete denitrification and NO mitigation. The promotion of PFOA for denitrification and NO mitigation can gain a more comprehensive cognition of the role of PFOA in wastewater treatment. The release mechanism of EPS can afford new insights for the development of effective methods to enhance nitrogen removal and reduce NO emissions.

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