Hydrogen-driven autotrophic degradation of halogenated organic pollutants in a membrane biofilm reactor: Advances and challenges

The widespread presence of halogenated organic pollutants (HOPs) in aquatic environments, presents significant risks to ecological security and human health due to their persistence, bioaccumulation, and toxicity. Therefore, there is a growing interest in the hydrogen-based autotrophic membrane biofilm reactor (H2-based MBfR) as a promising biological treatment technique for HOPs degradation. This method has gained considerable attention due to its high degradation efficiency and energy-saving benefits. Nevertheless, a thorough examination of the pivotal factors that influence and the mechanisms that underlie the hydrogen-driven autotrophic degradation of HOPs remains to be determined, primarily due to the intricate transformation of HOPs and the presence of diverse microbial species in H2-based MBfRs. This review aims to provide a comprehensive overview of the current research on H2-based MBfRs for HOPs degradation and elucidate the specific mechanisms involved in the biodegradation process. The advantages of H2-based MBfRs have been identified, including operational effectiveness, low energy consumption, simultaneous degradation of pollutants, and production of low-toxicity intermediates. Next, the effects of several influencing factors on critical microbial growth and their contributions to the degradation of HOPs were discussed. These factors include hydrogen supply, surface loading, inorganic anions, dissolved organic matter, and metal catalysts. Subsequently, the internal mechanisms involved in the biodegradation process of HOPs through H2-based MBfRs were determined, such as adsorption, microbial metabolism, and catalytic reduction. Furthermore, the challenges and prospects for utilizing H2-based MBfRs to enhance the degradation of HOPs were addressed. These findings not only advance the field of hydrogen-driven autotrophic degradation of HOPs but also expand its potential applications in the future.