Potential of a static magnetic field to inhibit filamentous sludge bulking in activated sludge process

Abstract

Sludge bulking caused by filamentous microorganisms is one of the prevailing operational problems in activated sludge process. Its severity is determined by the relative abundance of filamentous microorganisms that prevents the close packing of sludge flocs. This occurrence interferes in the separation and settling activities leading to the failure of the overall treatment process. The severity of bulking has directed to numerous inhibition approaches. However, the approaches have various drawbacks such as high sludge wastage. Hence, operation of a biological reactor by a static magnetic field was attempted. Two sequencing batch reactors (SBR), Reactor A (SBRA) and Reactor B (SBRB), were operated in low dissolved oxygen level to encourage filamentous microorganisms' growth. SBRA was subjected to a magnetic field intensity of 88.0 mT, while SBRB served as the control system. The findings showed that sludge flocs in SBRA were positively developed, corresponding to a lower sludge volume index (SVI) of less than 10 mL/g. Magnetically exposed activated sludge also showed less possibility on the presence of filamentous microorganisms compared with unexposed sludge. These evidences confirmed that use of magnetic field is feasible to inhibit filamentous sludge bulking occurrence.