Abstract
A rectangular double chamber with trivalent arsenic as the electron donor of the biological anode was constructed by microbial fuel cells (MFC), and the feasibility of the MFC simultaneous degradation of trivalent arsenic and nitrate was studied. Experimental results show that the co-matrix-coupled MFC reactor oxidizes trivalent arsenic in an anode chamber and degrades nitrate in the cathode chamber. The removal rate of trivalent arsenic is about 63.35%, and the degradation rate of nitrate is about 55.95% during the complete and stable operation period. MFC can continuously output electric energy, and the maximum output voltage is 388 mV. We compared and analyzed the main functional microflora of biofilm microorganisms in an anode chamber. In the long-term arsenic-polluted environment, the activity of Acinetobacter, Pseudomonas bacteria with arsenic resistance, was improved. It is inferred that a fraction of trivalent arsenic was oxidized to pentavalent arsenic by electrode-attached microorganisms. While remaining trivalent, arsenic was taken up by the suspended bacterial biomass and converted into stable arsenide. The results of this study have theoretical reference value for the expansion of the MFC application scope.
Highlights
With the rapid development of the social economy, arsenic pollution in water has become a global environmental problem, mainly from the use of semiconductors and herbicides, as well as arsenic-containing wastewater discharged from petroleum processing, electroplating, mining, and smelting industries
Studies have found that Bacillus subtilis, Thiobacillus ferrooxidans, and Bacillus cereus [8,9,10] can adsorb arsenic in different valence states, and some iron bacteria can act on arsenic in sewage
The stable operation of the microbial fuel cells (MFC) lasted for two months, and there was no significant difference in the trend of three consecutive output voltages to determine the successful acclimation of microorganisms
Summary
With the rapid development of the social economy, arsenic pollution in water has become a global environmental problem, mainly from the use of semiconductors and herbicides, as well as arsenic-containing wastewater discharged from petroleum processing, electroplating, mining, and smelting industries. The treatment of arsenic pollution in water is mainly divided into an ion-exchange method, adsorption method, extraction method precipitation method, and microbial method. Based on the previous research, this study combined the trivalent arsenic oxidation reaction and nitrate reduction reaction in an MFC to construct a comatrix biogenic cathode MFC. This research is focused mainly on whether the feasibility of using MFC to simultaneously degrade trivalent arsenic and nitrate and simultaneously generate electricity and could provide a theoretical basis for the practical application of the coupled treatment of pollutants by MFC. MFC Testing and Chemical Analysis Current density (J, mA/m3) was calculated as J = U/(RV), where U is the cell voltage (mV), R is the external resistance (Ω), and V is the effective volume of the cathode chamber (m3). The Shannon calculator returns the Shannon diversity index for an OTU definition with a higher value, indicating higher diversity [22]
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