Improving water desalination by hydraulically coupling osmotic microbial fuel cell with microbial desalination cell

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An osmotic microbial fuel cell (OsMFC) containing a forward-osmosis membrane, hydraulically coupled with a microbial desalination cell (MDC) with ion-exchange membranes, greatly improves desalination efficiency.
An osmotic microbial fuel cell (OsMFC) containing a forward-osmosis membrane, hydraulically coupled with a microbial desalination cell (MDC) with ion-exchange membranes, greatly improves desalination efficiency.

Researchers at the University of Wisconsin–Milwaukee in the US have developed a system to treat artificial wastewater and desalinate saline water, comprising two membrane-based bioelectrochemical reactors.

In this system, an osmotic microbial fuel cell (OsMFC) containing a forward-osmosis (FO) membrane is hydraulically coupled with a microbial desalination cell (MDC) that contains ion-exchange membranes.

The coupled system offers significantly improved desalination efficiency through both dilution (in the OsMFC) and salt removal (in the MDC), and achieves more organic removal than an individual MDC.

The high-power operation mode is more suitable for the OsMFC than the open-circuit mode and the high-current mode, because of good desalination performance (95.9% conductivity reduction in the coupled system) and energy production (0.160 kWh/m3 treated saline water).

When the active layer of the FO membrane is facing the feed solution, a higher water flux is obtained than the reverse membrane orientation.

The coupled system achieves a high reduction in conductivity (>85%) from the salt solution containing 10–50 g NaCl/L. The acidified water is more advantageous as a catholyte for the MDC because of the superior desalination performance.

These results collectively demonstrate the feasibility of a membrane-based bioelectrochemical system for simultaneous wastewater treatment and saline water desalination.

Journal of Membrane Science, Volume 441, 15 August 2013, Pages 18–24.