Assessment of an anti-scale low-frequency electromagnetic field device on drinking water biofilms

Combination of magnetic field and ultraviolet for fouling control in saline wastewater distribution systems

Fouling is a significant challenge for recycling and reusing saline wastewaters for industrial, agricultural or municipal applications. In this study, we propose a novel approach of magnetic field (MaF) and ultraviolet (UV) combined application for fouling mitigation. Results showed, combination of MaF and UV (MaF-UV) significantly decreased the content of biofouling and reduced the complexity of microbial networks, compared to UV and MaF alone treatments. This was due to MaF as pretreatment effectively reduced the water turbidity, improve the influent water quality of UV disinfection and increases UV transmittance, eliminating the adverse impacts of UV scattering and shielding, hence increased the inactivation effectiveness of UV disinfection process. MaF assisted UV also reduced the abundance of UV-resistant bacteria and inhibited the risk of bacterial photoreactivation and dark repair. Meanwhile, MaF-UV drastically reduced the contents of precipitates and particulate fouling by accelerating the transformation rate of CaCO3 crystal from compact calcite to loosen hydrated amorphous CaCO3, and enhancing the flocculation process. These findings demonstrated that MaF-UV is an effective anti-fouling strategy, and provide insights for sustainable application of saline wastewaters.

Electromagnetic fields for biofouling mitigation in reclaimed water distribution systems

Biofouling is ubiquitous in reclaimed water distribution systems and causes various industrial, economic, and health issues. This paper investigated the anti-biofouling efficacy of electromagnetic fields (EMFs) for agricultural emitters used for two types of reclaimed water. 16S rRNA gene sequencing and X-ray diffraction were applied to determine the microbial communities and mineral compositions in biofilms. The obtained results revealed that EMF treatment significantly changed the bacterial communities and reduced their diversities in biofilm by affecting water quality parameters. Network analysis results indicated that EMFs were detrimental to the co-occurrence patterns of mutualistic relationships among bacterial species, destroyed the connectivity and complexity of the networks, and inhibited biofilm formation [decreased total biomass and extracellular polymeric substance (EPS) content]. EMF treatment could also decrease the deposition of mineral precipitates, reducing the carbonate and silicate content in biofilm. The decrease of EPS content appeared to reduce biofilm-induced mineral crystallization, while the ion precipitations accelerated by EMFs caused an erosive effect on biofilm. The results demonstrated that EMF treatment is an effective, chemical-free, and anti-biofouling treatment method with great potential for biofouling control in reclaimed water distribution systems.

Low-frequency electromagnetic fields as an alternative to sanitize water of drinking systems in poultry production?

Low-frequency electromagnetic fields (LF-EMF) may present an alternative to conventional sanitation methods of water supply lines in animal production. The objective of this study was to evaluate the effect of the application of LF-EMF on bacterial concentrations and biofilms at scale-models of different drinking systems (circulating and non-circulating) conventionally used in poultry holdings. Treated systems were equipped with commercial devices producing pulsed electromagnetic signals of low frequency up to 10,000 Hz; max. 21 mT. Exposure of water to LF-EMF resulted in changes of the culturable bacterial counts, although with high standard deviations. Differing between systems types, LF-EMF treatment seemed to be responsible either for a limitation or for an increase of colony forming unit counts, with partly statistically significant differences, especially in early stages of treatment. In contrast, neither biofilm formation nor counts of cells suspended in water differed between treated and control lines over 28 days of experiment, as determined by fluorescence microscopy. Although this study indicates that LF-EMF may influence culturability of water microorganisms, no clear inhibitory effects on bacterial biofilm formation or on planktonic microbes by LF-EMF treatment were confirmed in the experiments.