Simulation and Optimization of the Combined High-Gradient Magnetic Separation-Ultraviolet Photocatalysis (HGMS-UV/TiO2) System for Ballast Water Treatment

Abstract

Ballast water has a negative impact on marine environment; the existing combined ultraviolet (UV) filtration system that for treating ballast water has relatively low effective rate and instability in inactivating microorganisms. In this study, the established high gradient magnetic separation-ultraviolet photocatalysis (HGMS-UV/TiO2) system was taken, the back propagation (BP) neural network and TracePro was used to simulate and analyse the UV field intensity in the system for optimizing. Further experimental verification was carried out with seawater sample to measure its inactivation effects on microorganisms including zooplankton, phytoplankton and bacteria. The results showed that HGMS-UVC/TiO2 system had good inactivation effect on zooplankton and bacteria, but relatively poor inactivation effect on phytoplankton. The optimal strategy for optimizing the UV intensity was further obtained, it is concluded that after adding ultraviolet A (UVA), the UV intensity distribution of the system is more uniform, and the average illumination intensity is also improved, but the optical path of UV in ballast water should not be too long. The optimized system could increase the intracellular K+ leakage of phytoplankton cells by more than 25%, indicating that the damage to cell membrane permeability was stronger. In conclusion, the optimized HGMS-UVA/UVC/TiO2 system can improve the inactivation capacity of microorganisms and provide basic theoretical support for improving the capacity and level of treatment in ballast water.