Global Water Program
Global Water Program
New Magazine Post: Microbial Desalination Cell for Simultaneous Water Desalination and Energy Production
This study shows that an air-cathode microbial desalination cell can desalinate water without the need for any external electrical power. Here, microbes desalinated water and produced excess electrical power.
In fifteen years, two out of every three persons on the globe may be living in water-scarce conditions (WHO, 2009). Desalination is one of the solutions to provide freshwater. It is estimated that in 2015, the worldwide desalination capacity will increase from 44.1 to 97.5 million cubic meters of water per day (Kristen, 2007; Lattemann et al., 2009). Concurrently, the demand for oil is expected to exceed production within the same time frame. This poses a major problem when we know that energy accounts 40 percent of the total cost of desalination (Figure 1). Worldwide efforts are being undertaken to tackle climate change and reduce the production of greenhouse gases. In their report on energy, Barack Obama and Joe Biden asserted: “We believe we have a moral, environmental, economic, and security imperative to address our dependence on foreign oil and tackle climate change in a serious, sustainable manner.” The U.S. government will invest $150 billion over 10 years in renewable energies.
Microbial fuel cell (MFC) technologies represent a new approach to directly generate electricity from biomass using bacteria. In an MFC, microorganisms oxidize organic matter on the anode producing electrons. The electrons flow through the external circuit to the cathode where the reduction of oxygen occurs (Figure 2) (Logan et al. 2009). In 2009, a group of researchers from Tshinghua University, China in collaboration with Pennsylvania State University, USA, built a novel device called a microbial desalination cell (MDC) that could simultaneously desalinate water and produce energy (Cao et al., 2009). The concept is similar to water electrodialysis (Shaposhnik et al., 1997) but instead of applying an external source of energy, the MDC uses the electrical energy produced by the bacteria.
The microbial desalination cell (MDC) consists of a MFC that was modified by adding a desalination compartment in a middle chamber. The saline water is placed between an anion (AEM) and a cation exchange membrane (CEM). The AEM is placed next to the anode and the CEM next to the cathode. Naturally occurring bacteria are used on the anode, and they grow using organic matter (acetate) and produce electrical current and release protons into the water. Protons cannot move to the cathode because they cannot diffuse through the AEM as only negatively charged ions can pass through this membrane. In order to maintain the charge balance, an anion (Cl–) flows from the middle desalination chamber to the anode. At the cathode, protons are removed from water and so sodium ions (Na+) in the desalination chamber move to the cathode chamber to balance charge. As a consequence sodium chloride salt (NaCl) in the middle chamber is removed; thus water is desalinated (Figures 3 and 4).
Read the full article :Global Water Program
New Magazine Post: Microbial Desalination Cell for Simultaneous Water Desalination and Energy Production
This study shows that an air-cathode microbial desalination cell can desalinate water without the need for any external electrical power. Here, microbes desalinated water and produced excess electrical power.
In fifteen years, two out of every three persons on the globe may be living in water-scarce conditions (WHO, 2009). Desalination is one of the solutions to provide freshwater. It is estimated that in 2015, the worldwide desalination capacity will increase from 44.1 to 97.5 million cubic meters of water per day (Kristen, 2007; Lattemann et al., 2009). Concurrently, the demand for oil is expected to exceed production within the same time frame. This poses a major problem when we know that energy accounts 40 percent of the total cost of desalination (Figure 1). Worldwide efforts are being undertaken to tackle climate change and reduce the production of greenhouse gases. In their report on energy, Barack Obama and Joe Biden asserted: “We believe we have a moral, environmental, economic, and security imperative to address our dependence on foreign oil and tackle climate change in a serious, sustainable manner.” The U.S. government will invest $150 billion over 10 years in renewable energies.
Microbial fuel cell (MFC) technologies represent a new approach to directly generate electricity from biomass using bacteria. In an MFC, microorganisms oxidize organic matter on the anode producing electrons. The electrons flow through the external circuit to the cathode where the reduction of oxygen occurs (Figure 2) (Logan et al. 2009). In 2009, a group of researchers from Tshinghua University, China in collaboration with Pennsylvania State University, USA, built a novel device called a microbial desalination cell (MDC) that could simultaneously desalinate water and produce energy (Cao et al., 2009). The concept is similar to water electrodialysis (Shaposhnik et al., 1997) but instead of applying an external source of energy, the MDC uses the electrical energy produced by the bacteria.
The microbial desalination cell (MDC) consists of a MFC that was modified by adding a desalination compartment in a middle chamber. The saline water is placed between an anion (AEM) and a cation exchange membrane (CEM). The AEM is placed next to the anode and the CEM next to the cathode. Naturally occurring bacteria are used on the anode, and they grow using organic matter (acetate) and produce electrical current and release protons into the water. Protons cannot move to the cathode because they cannot diffuse through the AEM as only negatively charged ions can pass through this membrane. In order to maintain the charge balance, an anion (Cl–) flows from the middle desalination chamber to the anode. At the cathode, protons are removed from water and so sodium ions (Na+) in the desalination chamber move to the cathode chamber to balance charge. As a consequence sodium chloride salt (NaCl) in the middle chamber is removed; thus water is desalinated (Figures 3 and 4).
Read the full article :Global Water Program
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