The promotion of the atrazine degradation mechanism by humic acid in a soil microbial electrochemical system.

The enhancing effects of anodes on the degradation of the organochlorine pesticide atrazine (ATR) in soil within microbial electrochemical systems (MES) have been extensively researched. However, the impact and underlying mechanisms of soil microbial electrochemical systems (MES) on ATR degradation, particularly under conditions involving the addition of humic acids (HAs), remain elusive. In this investigation, a soil MES supplemented with humic acids (HAs) was established to assess the promotional effects and mechanisms of HAs on ATR degradation, utilizing EEM-PARAFAC and SEM analyses. Results revealed that the maximum power density of the MES in soil increased by 150%, and the degradation efficiency of ATR improved by over 50% following the addition of HAs. Furthermore, HAs were found to facilitate efficient ATR degradation in the far-anode region by mediating extracellular electron transfer. The components identified as critical in promoting ATR degradation were Like-Protein and Like-Humic acid substances. Analysis of the microbial community structure indicated that the addition of HAs favored the evolution of the soil MES microbial community and the enrichment of electroactive microorganisms. In the ATR degradation process, the swift accumulation of Hydrocarbyl ATR (HYA) was identified as the primary cause for the rapid degradation of ATR in electron-rich conditions. Essentially, HA facilitates the reduction of ATR to HYA through mediated bonded electron transfer, thereby markedly enhancing the efficiency of ATR degradation.

Study on the mechanism of mitigating membrane fouling in MFC-AnMBR coupling system treating sodium and magnesium ion-containing wastewater.

Anaerobic Membrane Bioreactors (AnMBR) offer numerous advantages in wastewater treatment, yet they are prone to membrane fouling after extended operation, impeding their long-term efficiency and stability. In this study, a coupled system was developed using modified conductive membranes as the filtration membrane for the AnMBR and as the anodic conductive membrane in the microbial electrochemical system, with a total volume of approximately 2.57 L. The research focused on understanding the membrane fouling characteristics of the AnMBR when treating wastewater containing sodium ion (Na+) and magnesium ion (Mg2+). When the system was treating wastewater containing Na+, organic pollutants such as proteins and polysaccharides were identified as the primary causes of membrane fouling. Three experimental groups generating different electric currents exhibited extended operational times compared to the open-circuit control group, with extensions of 30, 24, and 15 days, respectively. Conversely, when treating wastewater with Mg2+, organic-inorganic composite fouling, primarily driven by Mg2+ bridging, emerged as the key challenge, with the experimental groups showing operational extensions of 5, 8, and 23 days, respectively, in comparison to the control group. Analysis of proteins and polysaccharides indicated that electric current played a crucial role in reducing organic fouling in the sludge cake layer. When treating wastewater containing Na+, the effectiveness of membrane fouling control was directly proportional to the electric current, while when treating wastewater containing Mg2+, it was directly proportional to the voltage.

Efficient use of electrons in a double-anode microbial fuel cell-biofilm electrode reactor self-powered coupled system for degradation of azo dyes.

A coupled system consisting of a double-anode microbial fuel cell (MFC) unit and a biofilm electrode reactor (BER) has been applied to degrade the azo dye reactive brilliant red X-3B. In this system, the MFC effluent was used as the input of the BER. The MFC preliminarily degraded X-3B while generating electricity, and the BER obtained electrons from the MFC through the external circuit to continue degrading pollutants without the need for an external power supply. The X-3B removal efficiency was 41.93% higher in the coupled system than the control when the X-3B concentration was 3000 mg/L. The analysis of intermediate products showed that the azo bond of X-3B broke in the MFC, generating a large number of complex intermediates such as anthraquinones, which were further degraded into simple organic compounds in the BER. Meanwhile, the abundance of microbial taxa related to the degradation of refractory organics in the MFC was high, as was that of microbial taxa related to the degradation of simple organics in the BER. Furthermore, the abundance of microorganisms related to power generation in the MFC increased. These results provided an efficient strategy for improving electron utilization efficiency in the coupling system of bioelectrochemical system.