title: The strengthening effect of a static magnetic field on activated sludge activity at low temperature.
abstract: The strengthening effects of static (homopolar and heteropolar) magnetic fields (MF) on microorganisms were compared in activated sludge degrading organic matter at low temperature. The TTC dehydrogenase activity improved substantially through external heteropolar MF intensification, and led to the highest COD removal rate of 94.9% at 5°C. Phospholipid fatty acid analysis showed that C16:1ω7c, C18:1ω7c and C18:1ω9c were the essential unsaturated fatty acids in cell membrane at low temperature (4-15°C), accounting for the majority of the whole unsaturated fatty acids. The MF effect increased the Gram-negative bacteria content to improve the cold adaptability. Shannon-Wiener diversity analysis demonstrated the samples with heteropolar MF had a higher PLFA diversity index (1.17-1.25) than that with homopolar MF (0.89-1.13). AFM observation showed MF smoothed part of the microbial cell surface, with some remaining distinct protuberances. Heteropolar MF enhancement performance is much more effective than that of the homopolar MF with identical plate distance.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, Jiangsu, PR China.
authors.forename: Chuan
authors.initials: C
authors.lastname: Niu
authors.forename: Jinju
authors.initials: J
authors.lastname: Geng
authors.forename: Hongqiang
authors.initials: H
authors.lastname: Ren
authors.forename: Lili
authors.initials: L
authors.lastname: Ding
authors.forename: Ke
authors.initials: K
authors.lastname: Xu
authors.forename: Weihao
authors.initials: W
authors.lastname: Liang
mesh_terms: D001419:Bacteria / Q000378:metabolism; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors / Q000382:microbiology; D002462:Cell Membrane / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000032:analysis; D060526:Magnetic Fields; D018625:Microscopy, Atomic Force; D010743:Phospholipids / Q000378:metabolism; D025341:Principal Component Analysis; D012722:Sewage / Q000382:microbiology*; D013696:Temperature
chemical_list: D005231:Fatty Acids, Unsaturated; D010743:Phospholipids; D012722:Sewage
keywords: Activated sludge; Low temperature; Magnetic field strengthening; Microbial diversity; Phospholipid fatty acid