Effects of Pressurized Aeration on the Biodegradation of Short-Chain Chlorinated Paraffins by Escherichia coli Strain 2

Yongxing Qian; Wanling Han; Fuhai Zhou; Bixiao Ji; Huining Zhang; Kefeng Zhang

doi:10.3390/membranes12060634

Effects of Pressurized Aeration on the Biodegradation of Short-Chain Chlorinated Paraffins by Escherichia coli Strain 2

Membranes (Basel). 2022 Jun 19;12(6):634. doi: 10.3390/membranes12060634.

Authors

Yongxing Qian^{1

2}, Wanling Han^{1

2}, Fuhai Zhou³, Bixiao Ji^{1

2}, Huining Zhang^{1

2}, Kefeng Zhang^{1

2}

Affiliations

¹ School of Civil Engineering and Architecture, NingboTech University, Ningbo 315000, China.
² Ningbo Research Institute, Zhejiang University, Ningbo 315100, China.
³ Zhejiang Haiyi Environmental Protection Equipment Engineering Co., Ltd., Quzhou 324000, China.

Abstract

Short-chain chlorinated paraffins (SCCPs) were defined as persistent organic pollutants in 2017, and they can migrate and transform in the environment, accumulate in organisms, and amplify through the food chain. Although they pose a serious threat to environmental safety and human health, there are few papers on their removal. The current SCCP removal methods are expensive, require severe operating conditions, involve time-consuming biological treatment, and have poor removal specificities. Therefore, it is important to seek efficient methods to remove SCCPs. In this paper, a pressurized reactor was introduced, and the removal performance of SCCPs by Escherichia coli strain 2 was investigated. The results indicated that moderate pure oxygen pressurization promoted bacterial growth, but when it exceeded 0.15 MPa, the bacterial growth was severely inhibited. When the concentration of SCCPs was 20 mg/L, the removal rate of SCCPs was 85.61% under 0.15 MPa pure oxygen pressurization for 7 days, which was 25% higher than at atmospheric pressure (68.83%). In contrast, the removal rate was only 69.28% under 0.15 MPa air pressure. As the pressure continued to increase, the removal rate of SCCPs decreased significantly. The total amount of extracellular polymeric substances (EPS) increased significantly upon increasing the pressure, and the amount of tightly bound EPS (TB-EPS) was higher than that of loosely bound EPS (LB-EPS). The pressure mainly promoted the secretion of proteins in LB-EPS. Furthermore, an appropriate pure oxygen pressure of 0.15 MPa improved the dehydrogenase activity. The gas chromatography-mass spectrometry (GC-MS) results indicated that the degradation pathway possibly involved the cleavage of the C-Cl bond in SCCPs, which produced Cl^-, followed by C-C bond breaking. This process degraded long-chain alkanes into short-chain alkanes. Moreover, the main degradation products detected were 2,4-dimethylheptane (C₉H₂₀), 2,5-dimethylheptane (C₉H₂₀), and 3,3-dimethylhexane (C₈H₁₈).

Keywords: Escherichia coli strain 2; pressurized aeration; removal mechanism; short-chain chlorinated paraffins.

Abstract

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