Integrated drip hydroponics-microbial fuel cell system for wastewater treatment and resource recovery

Key issues to consider toward an efficient constructed wetland-microbial fuel cell: the idea and the reality

The research on constructed wetland (CW) and microbial fuel cell (MFC) has been separate studies worldwide with crucial achievements being made in both fields. Due to environmentally friendly feature (of CW) and rich microbial population and excellent electrode catalytic activity (of MFC), CW and MFC have their own anticipated application prospect in wastewater purification and biological electricity generation. More significantly, the idea of embedding MFC into CW to form CW-MFC expands the scope for both of them and this has received much interest in recent years due to its striking features of sewage treatment efficiency, electricity generation, sustainability, and environmental friendliness. The increasing interest and the lack of soul of CW-MFC emerging to the new researchers reflect the need to recall the idea and summarize its development with regard to achieving its reality via some key issues This forms the basis of the paper. The paper also includes how to enhance the efficiency of electricity generation and supplement energy consumption, the degradation of emerging pollutants, and the degradation mechanism as well as the potential joint application of CW-MFC with other treatment technique. A mass of CW-MFC design parameters has been synthesized from the literature. Challenges and potential directions of CW-MFC in the future are prospected. It is expected that the paper can serve as a linkage for bridging knowledge gaps for further studies of CW-MFC.

Energy harvesting from plants using hybrid microbial fuel cells; potential applications and future exploitation

Microbial Fuel Cells (MFC) can be fuelled using biomass derived from dead plant material and can operate on plant produced chemicals such as sugars, carbohydrates, polysaccharides and cellulose, as well as being "fed" on a regular diet of primary biomass from plants or algae. An even closer relationship can exist if algae (e.g., prokaryotic microalgae or eukaryotic and unicellular algae) can colonise the open to air cathode chambers of MFCs driving photosynthesis, producing a high redox gradient due to the oxygenic phase of collective algal cells. The hybrid system is symbiotic; the conditions within the cathodic chamber favour the growth of microalgae whilst the increased redox and production of oxygen by the algae, favour a more powerful cathode giving a higher maximum voltage and power to the photo-microbial fuel cell, which can ultimately be harvested for a range of end-user applications. MFCs can utilise a wide range of plant derived materials including detritus, plant composts, rhizodeposits, root exudates, dead or dying macro- or microalgae, via Soil-based Microbial Fuel Cells, Sediment Microbial Fuel Cells, Plant-based microbial fuel cells, floating artificial islands and constructed artificial wetlands. This review provides a perspective on this aspect of the technology as yet another attribute of the benevolent Bioelectrochemical Systems.

Integrating Microbial Fuel Cell and Hydroponic Technologies Using a Ceramic Membrane Separator to Develop an Energy-Water-Food Supply System

In this study, a microbial fuel cell was integrated into a hydroponic system (MFC-Hyp) using a ceramic membrane as a separator. The MFC-Hyp is a passive system that allows the transport of nutrients from wastewater in the microbial fuel cell (MFC) to water in the hydroponic vessel (Hyp) through a ceramic membrane separator, with no external energy input. The performance of this system was examined using potato-process wastewater as a source of energy and nutrients (K, P, N) and garlic chives (Allium tuberosum) as a hydroponic plant. The results showed that based on dry weight, the leaves of Allium tuberosum grew 142% more in the MFC-Hyp than those of the plant in the Hyp without the MFC, in a 49-day run. The mass fluxes of K, P, and NO3--N from the MFC to the Hyp through the ceramic membrane were 4.18 ± 0.70, 3.78 ± 1.90, and 2.04 ± 0.98 µg s-1m-2, respectively. It was apparent that the diffusion of nutrients from wastewater in the MFC enhanced the plant growth in the Hyp. The MFC-Hyp in the presence of A. tuberosum produced the maximum power density of 130.2 ± 45.4 mW m-2. The findings of this study suggest that the MFC-Hyp system has great potential to be a "carbon-neutral" technology that could be transformed into an important part of a diversified worldwide energy-water-food supply system.

Effectiveness of constructed wetland integrated with microbial fuel cell for domestic wastewater treatment and to facilitate power generation

Constructed wetlands (CWs) have gained a lot of attention for wastewater treatment due to robustness and natural pollutant mitigation characteristics. This widely acknowledged technology possesses enough merits to derive direct electricity in collaboration with microbial fuel cell (MFC), thus taking advantage of microbial metabolic activities in the anoxic zone of CWs. In the present study, two identical lab-scale CWs were selected, each having 56 L capacity. One of the CW integrated with MFC (CW-MFC) contains two pairs of electrodes, i.e., carbon felt and graphite plate. The first pair of CW-MFC consists of a carbon felt cathode with a graphite plate anode, and the second pair contains a graphite plate cathode with a carbon felt anode. The other CW was not integrated with MFC and operated as a traditional CW for evaluating the performance. CW-MFC and CW were operated in continuous up-flow mode with a hydraulic retention time of 3 days and at different organic loading rates (OLRs) per unit surface area, such as 1.45 g m-2 day-1 (OLR-1), 2.43 g m-2 day-1 (OLR-2), and 7.25 g m-2 day-1 (OLR-3). The CW-MFC was able to reduce the organic matter, phosphate, and total nitrogen by 92%, 93%, and 70%, respectively, at OLR of 1.45 g m-2 day-1, which was found to be higher than that obtained in conventional CW. With increase in electrochemical redox activities, the second pair of electrodes made way for 3 times higher power density of 16.33 mW m-2 as compared to the first pair of electrodes in CW-MFC (5.35 mW m-2), asserting carbon felt as a good anode material to be used in CW-MFC. The CW-MFC with carbon felt as an anode material is proposed to improve the electro-kinetic activities for scalable applications to achieve efficient domestic wastewater treatment and electricity production.

Advancements on sustainable microbial fuel cells and their future prospects: A review

A microbial fuel cell (MFC) is a sustainable device that produces electricity. The main components of MFC are electrodes (anode & cathode) and separators. The MFC's performance is ascertained by measuring its power density. Its components and other parameters, such as cell design and configuration, operation parameters (pH, salinity, and temperature), substrate characteristics, and microbes present in the substrate, all influence its performance. MFC can be scaled up and commercialized using low-cost materials without affecting its performance. Hence the choice of materials plays a significant role. In the past, precious and non-precious metals were mostly used. These were replaced by a variety of low-cost carbonaceous and non-carbonaceous materials. Nano materials, activated compounds, composite materials, have also found their way as components of MFC materials. This review describes the recently reported modified electrodes (anode and cathode), their improvisation, their merits, pollutant removal efficiency, and associated power density.

Performance evaluation of the integrated hydroponics-microbial electrochemical technology (iHydroMET) for decentralized domestic wastewater treatment

Here we report on the performance of the integrated drip hydroponics-microbial electrochemical technology (iHydroMET) for decentralized management of domestic wastewater at the household level. The study focused on optimizing the iHydroMET reactor components, followed by its performance evaluation for domestic wastewater treatment at different feed volumes. Based on the reactor components optimization work, granular activated charcoal:cocopeat (20:80) combination for bed matrix, 75% immersed cathode in effluent configuration, and Catharanthus roseus plant were selected for further experiments. The iHydroMET system with the optimized reactor components achieved efficient removal of organic matter (up to 93%) and turbidity (up to 98%) but minimal total nitrogen (<24%) and total phosphorous (<8%) removal after 24 h with 10 L of feed volume. It also removed the contaminants of emerging concern, such as sterols, at >95% efficiency. The UV-treated effluent (<2 MPN/100 mL) with considerable concentrations of N (∼34 mg/L) and P (∼5 mg/L) nutrients qualifies the standards for agricultural use and landscape irrigation purposes and contribute to lowering the burden on freshwater usage. The system also produced a power density of 30.3 mW/m². Cultivation of evergreen C. roseus, a high aesthetic value ornamental and medicinal plant, further adds to ecological and environmental benefits of the iHydroMET technology. Further modifications in system operation like creating a saturation zone in the reactor units might improve the electric output and result in sufficient removal of nutrients, making the use of effluent for flushing and other purposes possible in households.

Advancement in Benthic Microbial Fuel Cells toward Sustainable Bioremediation and Renewable Energy Production

Anthropogenic activities are largely responsible for the vast amounts of pollutants such as polycyclic aromatic hydrocarbons, cyanides, phenols, metal derivatives, sulphides, and other chemicals in wastewater. The excess benzene, toluene and xylene (BTX) can cause severe toxicity to living organisms in wastewater. A novel approach to mitigate this problem is the benthic microbial fuel cell (BMFC) setup to produce renewable energy and bio-remediate wastewater aromatic hydrocarbons. Several mechanisms of electrogens have been utilized for the bioremediation of BTX through BMFCs. In the future, BMFCs may be significant for chemical and petrochemical industry wastewater treatment. The distinct factors are considered to evaluate the performance of BMFCs, such as pollutant removal efficiency, power density, and current density, which are discussed by using operating parameters such as, pH, temperature and internal resistance. To further upgrade the BMFC technology, this review summarizes prototype electrode materials, the bioremediation of BTX, and their applications.

Advanced microbial fuel cell for waste water treatment-a review

Petroleum, coal, and natural gas reservoir were depleting continuously due to an increase in industrialization, which enforced study to identify alternative sources. The next option is the renewable resources which are most important for energy purpose coupled with environmental problem reduction. Microbial fuel cells (MFCs) have become a promising approach to generate cleaner and more sustainable electrical energy. The involvement of various disciplines had been contributing to enhancing the performance of the MFCs. This review covers the performance of MFC along with different wastewater as a substrate in terms of treatment efficiencies as well as for energy generation. Apart from this, effect of various parameters and use of different nanomaterials for performance of MFC were also studied. From the current study, it proves that the use of microbial fuel cell along with the use of nanomaterials could be the waste and energy-related problem-solving approach. MFC could be better in performances based on optimized process parameters for handling any wastewater from industrial process.