Integrated utilization of seawater using a five-chamber bioelectrochemical system

To reduce membrane scaling, effectively desalinate seawater, and recover magnesium, acid and alkali from the desalination process, a novel five-chamber bioelectrochemical system (BES) was developed in this study. This development was based on a four-chamber BES proposed recently, called microbial electrolysis desalination and chemical-production cell (MEDCC). Results showed that the desalination efficiency of seawater in the five-chamber BES was two times of that in the MEDCC. Removal efficiencies of Na+, Mg2+, and Ca2+ within 18 h using the system were 65±2%, 100±0%, and 80±2%, respectively, which were 20%, 66%, and 36% higher than those in the MEDCC. With the form of Mg(OH)2 precipitation, 73% of the total magnesium in solutions was recovered from the cathodic surface. Although the removal efficiencies of Mg2+ and Ca2+ in the five-chamber BES were higher, the Mg2+ and Ca2+ scaling found on the membrane surface was only 38.5% and 18.5% of that in MEDCC, respectively. With the different removal mechanism of Mg2+/Ca2+ ions, the membrane scaling problem was better resolved in the five-chamber BES than the other desalination BESs. With reduction of membrane scaling, the production of alkali, acid, and magnesium, the five-chamber BES should be a promising way to realize an integrated utilization of seawater.