RESUMEN
Methylene blue (MB) was regarded as a highly toxic and hazardous substance owing to its irreparable hazard and deplorable damage on the ecosystem and the human body. The treatment of this colorant wastewater appeared to be one of the towering challenges in wastewater treatment. In this study, a microbial fuel cell coupled with constructed wetland (CW-MFC) with effective MB elimination and its energy recuperation concurrently based on the incorporation of carbide lime as a substrate in a new copper oxide-loaded on carbon cloth (CuO/CC) cathode system was studied. The crucial influencing parameters were also delved, and the MB degradation and chemical oxygen demand (COD) removal efficiencies were correspondingly incremented by 97.3% and 89.1% with maximum power output up to 74.1 mW m-2 at optimal conditions (0.2 g L-1 carbide lime loading and 500 Ω external resistance). The carbide lime with high calcium ion content was greatly conducive for the enrichment of critical microorganism and metabolic activities. The relative abundances of functional bacteria including Proteobacteria and Actinobacteriota were vividly increased. Moreover, the impressive results obtained in printed ink wastewater treatment with a COD removal efficiency of 81.3% and a maximum power density of 58.2 mW m-2, which showcased the potential application of CW-MFC.
Asunto(s)
Fuentes de Energía Bioeléctrica , Compuestos de Calcio , Humanos , Electricidad , Humedales , Ecosistema , Cobre , Óxidos , Electrodos , BacteriasRESUMEN
Microplastics (MPs) in water pose a great threat to the ecological environment, but the impact of MPs on constructed wetland microbial fuel cells (CW-MFCs) has not been studied, so in order to fill the research gap and enrich the research in the field of microplastics, a 360-day experiment was designed to determine the operating status of CW-MFCs at different concentrations (0, 10, 100 and 1000 µg/L) polyethylene microplastics (PE-MPs) at different times, focusing on the changes of the CW-MFCs' ability to handle pollutants, power production performance and microbial composition. The results showed that with the accumulation of PE-MPs, the removal effect of COD and TP did not change significantly, and that the removal rate was maintained at around 90% and 77.9% respectively, within 120 d of operation. What's more, the denitrification efficiency increased (from 4.1% to 19.6%), but with the passage of time, it decreased significantly (from 7.16% to 31.9%) at the end of the experiment, while oxygen mass transfer rate was significantly increased. Further analysis showed that the accumulation of PE-MPs did not affect the current power density significantly with the changes of time and concentration, but the accumulation of PE-MPs would inhibit the exogenous electrical biofilm and increase the internal resistance, thereby affecting the electrochemical performance of the system. In addition, the results of microbial PCA showed that the composition and the activity of the microorganisms were changed under the action of PE-MPs, that the microbial community in CW-MFC showed a dose effect on the input of PE-MPs, and that the relative abundance of nitrifying bacteria with time was significantly affected by PE-MPs concentration. The relative abundance of denitrifying bacteria decreased over time, but PE-MPs promoted the reproduction of denitrifying bacteria, which was consistent with the changes in nitrification and denitrification rates. The removal modes of EP-MPs by CW-MFC include the adsorption and the electrochemical degradation, with two isothermal adsorption models of Langmuir and Freundlich being constructed in the experiment, and the electrochemical degradation process of EP-MPs being simulated. In summary, the results show that the accumulation of PE-MPs can induce a series of changes in substrate, microbial species and activity of CW-MFCs, which in turn affects the pollutant removal efficiency and power generation performance during its operation.
Asunto(s)
Fuentes de Energía Bioeléctrica , Microplásticos , Plásticos , Polietileno , Humedales , Aguas Residuales , BacteriasRESUMEN
Constructed wetland-microbial fuel cells (CW-MFCs) systems are a sustainable technology capable of producing bioelectricity and treating wastewater simultaneously. It is also possible to obtain bioelectricity from the photosynthetic substrates obtained by the rhizodeposition of macrophytes, where the electroactive microorganisms present in the rhizosphere use these compounds as biofuel. In the present study, the bioelectricity production capacity of Juncus effusus and Philodendron cordatum species was evaluated in a CW-MFC without an external carbon source. The Juncus effusus species showed a higher bioelectrochemical performance, as they recorded a maximum voltage of 399 mV, a power density of 63.7 mW/m2, a volumetric power density of 15.9â W/m3, an internal resistance of 200â Ω, an anodic potential of -368 mV, and a cathodic potential of 229 mV. In addition, different types of carbohydrates in the form of sugars (sucrose, fructose, galactose, and glucose) were quantified by liquid chromatography, with concentrations of 100-450â µg/L. Chromatographic analysis were performed from the root exudates released in the effluent of both species of macrophyte. Sucrose and glucose were the types of sugars that produced the largest amount with portions of up to 35% and 24%, respectively. Sugars are compounds that worked as electron donors for the production of bioelectricity by using endogenous substrates that fed the anodic biofilm. Consumption was 45-55% for sucrose and 40-65% for glucose. Of the different macrophytes evaluated in the CW-MFCs, it was observed that the production of bioelectricity differs mainly due to the quantity of the root exudates released in the rhizosphere.
RESUMEN
As an essential component in constructed wetland-microbial fuel cells (CW-MFC) system, the macrophytes play multiple roles in bioelectricity generation and decontaminants performance. However, the interrelation between macrophytes roots and cathode has not been fully investigated despite the fact that plant cultivation strategy is a critical issue in practice. For the first time, this study was designed to explore the interaction between macrophytes and cathode in CW-MFC by planting Cyperus altrnlifolius at relatively different positions from the cathode. The results showed that plants exhibited higher bioelectricity generation and dramatically improved pollution removal, as well as the improved richness and diversity of cathode microbes. More significantly, the relative locations between the plant roots and the cathode could lead to different cathode working patterns, while the optimal cathode pattern "plant root-assisted bio- & air-cathode" was formed when the plant roots are directly placed on the air-cathode layer in CW-MFC. The insight into the plant root and cathode relationship lies in whether the "multi-function cathode" can be established. This study contributes to increase the knowledge regarding the presence and behavior of plant roots and cathode throughout a CW-MFC system.