Denitrification in an integrated bioelectro-photocatalytic system

Abstract

Since nitrate causes severe ecological and health risks, nitrate contamination of drinking water sources has become one of the most important water quality concerns all over the world. Photocatalytic reduction of nitrate to molecular nitrogen presents a promising approach to remove nitrate from drinking water sources. However, harmful intermediates like NO, NO, NO and NO are usually formed, and metal loading or hole scavengers are generally needed to reduce the recombination of photo-generated electrons and holes, which will cause secondary pollution to drinking water. In this work, an efficient, selective and sustainable bioelectro-photocatalytic nitrate-reducing system by utilizing commercial TiO nanoparticles P25 as the photocatalyst and bio-electrons from microbial metabolism as the hole scavenger is reported. In this system, bio-electrons extracted from organic substrates in bioanode are transferred to the photocathode through an external circuit for hole quenching. With the utilization of the residual photogenerated electrons, nitrate is completely reduced to nitrogen without accumulation of harmful nitrite or ammonium. The experimental results and the mechanistic analysis using the first-principles density functional theory calculations demonstrate that toxic by-products like nitrite or ammonium will not be accumulated in this system. Thus, this approach has a great potential for sustainable remediation of nitrate-contaminated drinking water sources.

The ins and outs of photo-assisted microbial electrochemical systems for synchronous wastewater treatment and bioenergy recovery

“…Several typical inorganic water pollutants, such as NO3 --N, phosphate, and salt ions also can be removed by photo-assisted MESs. Generally, NO3 --N is commonly removed through biological processes, which requires large amounts of organic matter (as electron donors) to overcome a low C/N ratio and achieve biological denitrification (Lin et al, 2017). Recently, Cheng et al first applied denitrification biocathode coupling of TiO2 photoanode to effectively reduce NO3 --N (Cheng et al, 2017).…”

Impacts of enhanced microbial-photoreductive and suppressed dark microbial reductive dissolution on the mobility of As and Fe in flooded tailing soils with zinc sulfide

“…However, an integrated bioelectro-photocatalytic system can be established when bioavailable electron donors are lacking. This involves the transfer of mineral photoelectrons to metal-reducing bacteria through the minerals, as some minerals have the capacity to serve as electrical conductors [7,51,52]. Photoelectron separation and transfer could alleviate the lack of bio-electrons supplied from microbial degradation of organic matter under extremely adverse conditions.…”

Analysis of Anodes of Microbial Fuel Cells When Carbon Brushes Are Preheated at Different Temperatures

“…The A5 sequence type was 99% similar to an uncultured Bacteroidetes Anode bands were sequenced and are listed in Figure 3. The A1 sequence type represented in the clone library showed 99% identity to Azoarcus sp., which can use nitrate as an electron acceptor to degrade organic compounds [35]. In some MET-related studies, Azoarcus sp.…”