Bio-reduction of arsenate using a hydrogen-based membrane biofilm reactor

Area of Science:

• Environmental Science
• Environmental Engineering
• Microbiology

Background:

• Arsenate (As(V)) is a carcinogenic groundwater contaminant.
• Arsenite (As(III)) is more mobile and toxic than As(V), but can be removed via precipitation or adsorption.
• Hydrogen-based membrane biofilm reactors (MBfRs) show promise for contaminant reduction.

Purpose of the Study:

• To investigate the bio-reduction of As(V) to As(III) using a denitrifying MBfR.
• To evaluate the influence of operational parameters on As(V) reduction and removal.
• To explore As(III) removal mechanisms post-reduction.

Main Methods:

• Utilized a hydrogen-based membrane biofilm reactor (MBfR) with a denitrifying microbial community.
• Varied influent conditions including arsenate, nitrate, sulfate loading, and hydrogen pressure.
• Analyzed effluent for As(V) and As(III) concentrations.
• Employed scanning electron microscopy and energy dispersive X-ray analysis for solid phase characterization.

Main Results:

• Immediate reduction of As(V) to As(III) was observed in the MBfR.
• Decreased sulfate loading significantly increased As(V) reduction.
• Lower nitrate loading and higher As(V) loading enhanced the extent of As(V) reduction.
• Maximum As(V) removal occurred with no added sulfate.
• As(III) was effectively removed through sulfide precipitation or adsorption to Fe(II)-based solids.

Conclusions:

• The MBfR effectively facilitates As(V) bio-reduction to As(III).
• Sulfate and nitrate loading are critical parameters controlling As(V) reduction efficiency.
• This process offers a viable strategy for arsenate decontamination by converting it to a removable form.