Efficient Removal of Escherichia coli from Ballast Water Using a Combined High-Gradient Magnetic Separation-Ultraviolet Photocatalysis (HGMS-UV/TiO2) System
A new synergistic method was proposed to remove Escherichia coli by using high-gradient magnetic separation (HGMS)-ultraviolet titanium oxide photocatalysis (UV/TiO2). Compared with sole HGMS, UV radiation, UV/TiO2, and HGMS-UV, the combined HGMS-UV/TiO2 significantly increased the bacterial removal rate. After treatment of 6 min, bacterial removal rate for HGMS-UV/TiO2 was 5.25 log, and E. coli was unlikely to photoreactivate or dark repair. In addition, HGMS-UV/TiO2 treatment led to rapid increase of malondialdehyde (MDA) concentration, severe inhibition of superoxide dismutase (SOD) activity, and massive leakages of intracellular K+ and protein, proving the process caused more damage to E. coli cell structure. For HGMS-UV/TiO2 treatment, seawater turbidity did not significantly affect the bacterial removal rate, and 10 mg L−1 humic acid could largely reduce the bacterial removal rate. Totally, the HGMS-UV/TiO2 could be effectively employed to treat ballast water with less organic matter. Despite the limitation, this novel method has many potential applications in the treatment of ballast water.
KeywordsBallast water Escherichia coli HGMS-UV/TiO2 process Bactericidal mechanism
This research was financially supported by the National Key Research and Development Program of China (2017YFC1404605), the Natural Science Foundation of China (Grant No. 51579049 and 51509044), and the High Tech Ship Program.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
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