The race between classical microbial fuel cells, sediment-microbial fuel cells, plant-microbial fuel cells, and constructed wetlands-microbial fuel cells: Applications and technology readiness level.

Microbial fuel cell (MFC) is an interesting technology capable of converting the chemical energy stored in organics to electricity. It has raised high hopes among researchers and end users as the world continues to face climate change, water, energy, and land crisis. This review aims to discuss the journey of continuously progressing MFC technology from the lab to the field so far. It evaluates the historical development of MFC, and the emergence of different variants of MFC or MFC-associated other technologies such as sediment-microbial fuel cell (S-MFC), plant-microbial fuel cell (P-MFC), and integrated constructed wetlands-microbial fuel cell (CW-MFC). This review has assessed primary applications and challenges to overcome existing limitations for commercialization of these technologies. In addition, it further illustrates the design and potential applications of S-MFC, P-MFC, and CW-MFC. Lastly, the maturity and readiness of MFC, S-MFC, P-MFC, and CW-MFC for real-world implementation were assessed by multicriteria-based assessment. Wastewater treatment efficiency, bioelectricity generation efficiency, energy demand, cost investment, and scale-up potential were mainly considered as key criteria. Other sustainability criteria, such as life cycle and environmental impact assessments were also evaluated.

Microalgae and bio-polymeric adsorbents: an integrative approach giving new directions to wastewater treatment.

This review analyses the account of biological (microalgae) and synthetic (bio-polymeric adsorbents) elements to compass the treatment efficiencies of various water pollutants and mechanisms behind them. While considering pollutant removal, both techniques have their own merits and demerits. Microalgal-based methods have been dominantly used as a biological method for pollutant removal. The main limitations of microalgal methods are capacity, scale, dependence on variables of environment and duration of the process. Biopolymers on the other hand are naturally produced, abundant in nature, environmentally safe and biocompatible with cells and many times biodegradable. Algal immobilization in biopolymers has promoted the reuse of cells for further treatment and protected cells from toxic environment monitoring and controlling the external factors like pH, temperature and salinity can promote the removal process while working with the mentioned technologies. In this review, a mechanistic view of both these techniques along with integrated approaches emphasizing on their loopholes and possibilities of improvement in these techniques is represented. In addition to these, the review also discusses the post-treatment effect on algal cells which are specifically dependent on pollutant type and their concentration. All these insights will aid in developing integrated solutions to improve removal efficiencies in an environmentally safe and cost-effective manner.Novelty statement The main objective of this review is to thoroughly understand the role of micro-algal cells and synthetic adsorbents individually as well as their integrative effect in the removal of pollutants from wastewater. Many reviews have been published containing information related to either removal mechanism by algae or synthetic adsorbents. While in this review we have discussed the agents, algae and synthetic adsorbents along with their limitations and explained how these limitations can be overcome with the integration of both the moieties together in process of immobilization. We have covered both the analytical and mechanistic parts of these technologies. Along with this, the post-treatment effects on algae have been discussed which can give us a critical understanding of algal response to pollutants and by-products obtained after treatment. This review contains three different sections, their importance and also explained how these technologies can be improved in the future aspects.

Innovative constructed wetland coupled with microbial fuel cell for enhancing diazo dye degradation with simultaneous electricity generation.

A novel earthen separator-based dual-chambered unplanted core of constructed wetland coupled with microbial fuel cell was developed for studying the microbe-material interaction and their effect on treatment performance and electricity generation. The constructed wetland integrated microbial fuel cell was evaluated for the degradation of high molecular weight diazo Congo red dye as a model pollutant. The system exhibited 89.99 ± 0.04% of dye decolorization and 95.80 ± 0.71% of chemical oxygen demand removal efficiency from an initial concentration of 50 ± 10 mg/L and 750 ± 50 mg/L, respectively. Ultraviolet-Visible spectrophotometric and gas chromatography-mass spectrometric analysis revealed naphthalene and phenol as mineralized products. The developed system achieved high power density and current density generation of 235.94 mW/m3 and 1176.4 mA/m3, respectively. Results manifested that dual-chambered constructed wetland coupled with microbial fuel cell has a high capability of dye decolorization and toxicity abatement with appreciable simultaneous bioelectricity generation owing to the significantly low internal resistance of 100 Ω.