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Interaction between microplastic and nitrifying bacteria, and their impacts on nitrification 2022 > Representative Research Publications > Research Results Home

Interaction between microplastic and nitrifying bacteria, and their impacts on nitrification

  • Journal Of Hazardous Materials / February 2022
  • Seulki Jeong, Jongkeun Lee(First author), Seulki Jeong, Kartik Chandran(Corresponding author)

Research Summary

Microplastics (MPs), which are smaller than 5 mm, have become an emerging concern, and great attention is being paid to their impacts on environmental facilities. Various MPs have been detected in the municipal wastewater treatment plants (WWTPs), they can affect biological processes in WWTPs.

Nitrification, the oxidative conversion of ammonia to nitrite or nitrate, is the first and limiting step in biological nitrogen removal in wastewater treatment. If MPs would potentially inhibit the nitrifying activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), the inorganic nitrogen conversion efficiency could be reduced.

This study explored the impact of different sizes of polystyrene (PS) on nitrification. The smaller PS (50 nm) had a higher impact than the larger PS (500 nm). The lowest conversion efficiency of ammonia was observed in the 50 nm PS exposure.

The transcriptional response of ammonia monooxygenase subunit A (amoA) exposed to PS was also evaluated to examine the sub-cellular responses of ammonia-oxidizing bacteria to PS exposure. Our results showed amoA expression did not directly correlate with the changes of DIN concentrations in the present study.

Fluorescence images were obtained to investigate the interactions between PS and nitrifying bacteria. The results revealed that the impact of PS on nitrifying bacteria might be unrelated to biological phenomena corresponding to uptake or penetration of PS. Fluorescence images showed that most of the PS existed outside of the bacterial cells.

Although an accurate mechanism needs to be identified in further studies, this study demonstrated that PS could interrupt nitrification. The findings of this study can contribute to the understanding of the potential influence of PS on nitrogen cycling in wastewater treatment.

Related Figures

[Fig. 1] Impacts of PS on the dissolved inorganic nitrogen (DIN) concentrations [Fig. 1] Impacts of PS on the dissolved inorganic nitrogen (DIN) concentrations

[Fig. 2] Comparison of the presence of two different sizes of fluorescent PS around the nitrifying bacteria: (a) 50 nm PS treatment and (b) 500 nm PS treatment[Fig. 2] Comparison of the presence of two different sizes of fluorescent PS around the nitrifying bacteria: (a) 50 nm PS treatment and (b) 500 nm PS treatment

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