Floating treatment wetlands integrated with microbial fuel cell for the treatment of urban wastewaters and bioenergy generation

Abstract

The objective of the present study was to develop a combined system composed of anaerobic biofilter (AF) and floating treatment wetlands (FTW) coupled with microbial fuel cells (MFC) in the buoyant support for treating wastewater from a university campus and generate bioelectricity. The raw wastewater was pumped to a 1,450 L tank, operated in batch flow and filled with plastic conduits. The second treatment stage was composed of a 1000 L FTW box with a 200 L plastic drum inside (acting as settler in the entrance) and vegetated with mixed ornamental plants species floating in a polyurethane support fed once a week with 700 L of wastewater. In the plant roots, graphite rods were placed to act as cathodes, while on the bottom of the box 40 graphite sticks inside a plastic hose with a stainless-steel cable acting as the anode chamber. Open circuit voltages were daily measured for 6 weeks, and later as closed circuit with the connection of 1000 Ω resistors. Plant harvestings were conducted, in which biomass production and plant uptake from each of the species were measured. On average, system was efficient in reducing BOD 5 (55.1%), COD (71.4%), turbidity (90.9%) and total coliforms (99.9%), but presented low efficiencies regarding total N (8.4%) and total P (11.4%). Concerning bioenergy generation, voltage peaks and maximum power density were observed on the feeding day, reaching 225 mV and 0.93 mW/m 2 , respectively, and in general decaying over the 7 days. In addition, plant species with larger root development presented higher voltage values than plants with the smaller root systems, possible because of oxygen release. Therefore, the combined system presented potential of treating wastewater and generating energy by integrating FTW and MFC, but further studies should investigate the FTW-MFC combination in order to improve its treatment performance and maximize energy generation.

Coupling Microbial Fuel Cell and Hydroponic System for Electricity Generation, Organic Removal, and Nutrient Recovery via Plant Production from Wastewater

“…In their study, the removals of COD, TP, and TN were 71.4%, 11.4%, and 8.4%, respectively, with a retention time of seven days for three weeks (seven days/cycle, a total of three cycles). The COD removal efficiencies (71.4%) reported by Colares et al (2021) [51] are lower than the removal (80.4%) produced in the present study, while the phosphate removal efficiencies in their study and the present study are at the same level (11.4%). It should be noted that the run time of the present study was 28 days as compared to 21 days in the work by Colares et al (2021) [51].…”

“…The maximum power density and the maximum current density produced in the present study are considerably larger than those reported by Yadav et al (2020) [47]. Colares et al (2021) [51] treated urban wastewater using a floating treatment wetlands-MFC with Canna generalis, Chrysopogon zizanioides, Cyperus papyrus Nanus, Hymenachne grumosa, and Equisetum hyemale. These plants were placed in floating supports and connected in parallel.…”

“…Their system produced a maximum COD removal efficiency of 53.9% in the anodic zone and 86.2 ± 8.1% overall in the run time of ~27 days. Using a closed floating treatment wetland-MFC without any separators, Colares et al (2021) [51] treated urban wastewater in the presence of five different plant species (Canna generalis, chrysopogon zizanioides, Cyperus papyrus Nanus, Hymenachne grumosa, and Equisetum hyemale). In their study, the removals of COD, TP, and TN were 71.4%, 11.4%, and 8.4%, respectively, with a retention time of seven days for three weeks (seven days/cycle, a total of three cycles).…”

MnO2@MXene/Carbon Cloth as an Anode for Microbial Fuel Cells

“…[1] Microbial fuel cells (MFCs) are multifunctional devices used for electricity generation and wastewater degradation through the metabolism of electrogenic bacteria. [2] The key electrode is the cathode, while oxygen acts as an electron acceptor in air cathode MFCs. [3] When potassium ferricyanide was used as the electron acceptor in the cathode compartment, the key electrode was the anode.…”

Removal of Phosphorus from Domestic Sewage by a Constructed Wetland Coupled Microbial Fuel Cell System

“…They are transferred outward from the anode through the medium and the anode is connected to the cathode by an external circuit (Ahmadpour et al 2020). In recent years, studies have shown that the MFC system has a good removal effect for refractory organic matter and can use the easily degradable organic matter as a matrix to generate electricity (Lim et al 2021;González et al 2020;Colares et al 2020).…”