In-line deoxygenation for organic carbon detections in seawater using a marine microbial fuel cell-biosensor

• An electrochemical cell was developed to reductively remove oxygen from seawater.
• A MFC-biosensor could monitor assimilable organic carbon (AOC) in anoxic seawater.
• The combination of the above enabled online AOC monitoring in aerobic seawater.
• The reductive oxygen removal was specific to oxygen and caused no interference.
• Online AOC monitoring was reproducible and seems feasible for desalination plants.

Assimilable organic carbon (AOC) is a key predictor for membrane biofouling in seawater desalination reverse osmosis (SWRO). Microbial fuel cells have been considered as biosensors for the detection of biodegradable organics. However, the presence of dissolved oxygen (DO) is known to completely suppress the signal production (i.e., current) of a typical MFC. This study describes AOC detection in normal oxygenated seawater by coupling an electrochemical cell for DO removal with a MFC-biosensor for AOC detection. The electrochemical deoxygenation for oxygen removal caused no interference in the AOC detection. A linear relationship (R2 = 0.991) between the AOC concentration and current production from the MFC biosensor was achieved. The coupling of an electrochemical cell with a MFC-biosensor can be effectively used as an online, rapid and inexpensive measure of AOC concentrations and hence as an indicator for biofouling potential of seawater.