Colorado desalination system produces hydrogen as well

A bioelectrochemical systems (BES) to concurrently desalinate salt water, produce hydrogen gas and potentially treat wastewater is being developed at the University of Colorado Denver, USA.

The work by Haiping Luo, Peter E Jenkins, and Zhiyong Ren from the departments of Civil Engineering and Mechanical Engineering, was reported in the 1 December 2010 edition of Environmental Science & Technology.

An integrated BES called a microbial electrolysis and desalination cell (MEDC) was divided into three chambers by inserting a pair of ion-exchange membranes. Each chamber serving one of the three functions.

With an added voltage of 0.8 V, lab-scale batch study showed the MEDC achieved the highest H2 production rate of 1.5 m³/m³ d (1.6 mL/h) from the cathode chamber, while also removing 98.8% of the 10 g/L NaCl from the middle chamber. The anode recirculation alleviated pH and high salinity inhibition on bacterial activity and further increased system current density from 87.2 to 140 A/m³, leading to an improved desalination rate by 80% and H2 production by 30%.

Compared with slight changes in desalination, H2 production was more significantly affected by the applied voltage and cathode buffer capacity, say the researchers, suggesting cathode reactions were likely affected by the external power supply in addition to the anode microbial activity.