Electricity Generation, Salt and Nitrogen Removal and Microbial Community in Aircathode Microbial Desalination Cell for Saline-Alkaline Soil-Washing Water Treatment

An aircathode microbial desalination cell (AMDC) was successfully started by inoculating anaerobic sludge into the anode of a microbial desalination cell and then used to study the effects of salinity on performance of AMDC and effect of treatment of coastal saline-alkaline soil-washing water. The results showed that the desalination cycle and rate gradually shorten, but salt removal gradually increased when the salinity was decreased, and the highest salt removal was 98.00 ± 0.12% at a salinity of 5 g/L. COD removal efficiency was increased with the extension of operation cycle and largest removal efficiency difference was not significant, but the average coulomb efficiency had significant differences under the condition of each salinity. This indicates that salinity conditions have significant influence on salt removal and coulomb efficiency under the combined action of osmotic pressure, electric field action, running time and microbial activity, etc. On the contrary, COD removal effect has no significant differences under the condition of inoculation of the same substrate in the anode chamber. The salt removal reached 99.13 ± 2.1% when the AMDC experiment ended under the condition of washing water of coastal saline-alkaline soil was inserted in the desalination chamber. Under the action of osmotic pressure, ion migration, nitrification and denitrification, NH4+-N and NO3−-N in the washing water of the desalination chamber were removed, and this indicates that the microbial desalination cell can be used to treatment the washing water of coastal saline-alkaline soil. The microbial community and function of the anode electrode biofilm and desalination chamber were analyzed through high-throughput sequencing, and the power generation characteristics, organics degradation and migration and transformation pathways of nitrogen of the aircathode microbial desalination cell were further explained.

Application of ion exchange membranes in enhancing algal production alongside desalination of saline water in microbial fuel cell

In the present world scenario the demand for fresh water and clean energy is driving the need to convert a microbial fuel cell (MFC) into an algal-based microbial desalination cell (MDC) that can support algal growth along with desalination of saline water. In this study, the performance of a five-chambered MDC fed with saline water having two different salt concentrations, namely 2.5 g/L and 5.0 g/L in desalination chamber, as well as MDC operated without algae in catholyte was investigated. The algal-based MDC operated with 5 g/L of total dissolved solid (TDS) in desalination chamber exhibited the best performance results among all other combinations giving a maximum power density of 45.52 mW/m2 and a desalination efficiency of 71 ± 2 %. Also, a chemical oxygen demand (COD) removal efficiency of 78 % and coulombic efficiency of 12.24 % was achieved with 5 g/L NaCl concentration in desalination chamber. Based on this experimental performance evaluation, it can be inferred that algal-based MDC can provide a promising and sustainable approach for wastewater treatment with the capability of simultaneous desalination, algal production and electrical energy recovery.

Portable Desalination Chamber Utilizing Water Permeable Polyethersulfone (PES) Membrane

This paper presents design and fabrication of portable desalination chamber utilizing water permeable polyethersulfone (PES) membrane. The chamber has four stages of desalination process. Each stage has a membrane clamped by filter plate to desalinate sea water and an outlet to qualify the desalinated water from each stage. The chamber works without electrical power, hence desalination process can be carried out in remote areas where electricity source is difficult to find. The water stream is used to test the pumping system of the chamber to pump the water from the water container. The test shows that the pumping system of the chamber is working properly in delivering water to each stage of the chamber without any leakage. The membrane used in each chamber is a modified PES membrane which has high water permeability. Water permeability of the membrane will guarantee that the salt water will permeate easily through the membrane porous during desalination process, hence results in producing fresh water at the final outlet.

Bioremediation of Steel Plant Wastewater and Improved Electricity Generation in Bio-Electrochemical Desalination Cell

A new technology called microbial desalination cell (MDC) approaches a comprehensive way to design an innovative system for removal of organic matter and dissolved solids from wastewater. In this study, two laboratory scale MDCs having three chambered (3C-MDC) and five chambered (5C-MDC) configuration were developed for integrated biodegradation of steel plant wastewater. The 3C-MDC have anodic, middle desalination and cathodic chamber; while 5C-MDC have anodic, cathodic, middle desalination and two concentrate chambers separated by ion exchange membranes. Using synthetic saline water with 8 and 30 g/L of TDS and steel plant wastewater (3.74 g TDS/L) in desalination chamber, the TDS removal of 64 ± 2.3%, 75 ± 1.8%, and 58 ± 1.3% were observed in 3C-MDC, while in 5C-MDC, those were 58 ± 1.5%, 71 ± 2.1%, and 64 ± 2.4%, respectively in 96 h of fed batch operation. With 30 g/L of TDS concentration, the power generation observed in 3C-MDC and 5C-MDCs were (81 mW/m2 and 78 mW/m2) higher than the power observed with 8 g/L (56 mW/m2 and 45 mW/m2). However, with steel plant wastewater in desalination chamber the power density increased to 76 mW/m2 in 5C-MDC and significantly decreased to 39 mW/m2 in 3C-MDC.

Multi-chamber microbial desalination cell for improved organic matter and dissolved solids removal from wastewater

A five-chamber microbial desalination cell (MDC) with anode, cathode, one central desalination chamber and two concentrate chambers separated by ion exchange membranes was operated in batch mode for more than 60 days. The performance of the MDC was evaluated for chemical oxygen demand (COD) removal, total dissolved solids (TDS) removal and energy production. An average COD removal of 81 ± 2.1% was obtained using acetate-fed wastewater as substrate in the anodic chamber inoculated with mixed anaerobic sludge. TDS removals of 58, 70 and 78% were observed with salt concentration of 8, 20 and 30 g/L, respectively, in the middle desalination chamber. The MDC produced a maximum power output of 16.87 mW/m2 during polarization. The highest Coulombic efficiency of 12 ± 2.4% was observed in this system using mixed anaerobic sludge as inoculum. The system effectively demonstrated capability for simultaneous organic matter removal and desalination along with power generation.