Irreversible inactivation of multidrug-resistant Gram-positive bacteria using S-functionalized graphene sponge anode

Area of Science:

• Environmental Science
• Materials Science
• Electrochemistry

Background:

• Multidrug-resistant bacteria in drinking water pose a significant public health risk.
• Conventional water disinfection methods like chlorination can produce harmful disinfection byproducts.
• Developing effective and sustainable methods for removing resistant bacteria from water is crucial.

Purpose of the Study:

• To investigate the electrochemical inactivation of Gram-positive multidrug-resistant Enterococcus gallinarum in drinking water.
• To evaluate the efficacy of sulfur-functionalized graphene sponges as anodes in this process.
• To assess the energy efficiency and potential for bacterial regrowth after treatment.

Main Methods:

• Graphene sponges functionalized with sulfur (S-doped) were used as anodes, coupled with N-doped graphene sponge cathodes.
• Electrochemical inactivation was performed in a flow-through system with continuous and intermittent current modes.
• Bacterial removal efficiency, energy consumption, and bacterial regrowth were monitored.
• Scanning electron microscopy (SEM) was used to analyze the damage to bacterial cells.

Main Results:

• A 2.3 log removal of E. gallinarum was achieved with S-functionalized graphene sponge anodes at 43.5 A m^-2, requiring 2.7 kWh m^-3.
• Non-functionalized electrodes showed lower removal (1.8 log) and higher energy demand (3.8 kWh m^-3).
• Intermittent current operation significantly reduced energy consumption to 1.8 kWh m^-3 while maintaining high removal rates (2.4 log).
• No bacterial regrowth was observed during 16-hour storage, with additional log removal noted for S-functionalized electrodes.
• SEM confirmed cell wall damage via low-voltage electroporation.

Conclusions:

• Sulfur-functionalized graphene sponge anodes are effective for the chlorine-free electrochemical inactivation of multidrug-resistant Gram-positive bacteria in drinking water.
• The system demonstrates high efficiency and reduced energy consumption, particularly with intermittent current.
• This technology presents a promising sustainable solution for water disinfection.