Concurrent boron removal from reverse osmosis concentrate and energy production using a microbial desalination cell-Donnan dialysis hybrid system†

Abstract

The removal of boron from aqueous solutions offers an important opportunity to improve the management of sustainable resources. In this regard, microbial desalination cells (MDCs) are a promising bioelectrochemical approach for effective water treatment, but the integrated MDC-Donnan Dialysis (DD) process for boron removal from reverse osmosis (RO) concentrated effluents has not been investigated before. Integration of the DD process with MDC is investigated in this paper for the first time to enhance the efficiency of the process by providing pre-treatment and natural pH manipulation. Therefore, the MDC process was evaluated for boron removal from boron-containing synthetic solution, geothermal water, and RO-concentrated effluent with the help of the DD system. The highest boron removal performance, with an efficiency of 72.1% in the desalination chamber and 74.8% in the DD-feed chamber, was obtained for boron-containing synthetic solution, while the COD removal efficiency was almost 90% in all water resources. However, the maximum power density was 4818 mW m⁻² with a closed circuit voltage of 1317 mV for RO concentrated water treatment due to its high ionic strength. Moreover, the most crucial output of this study is that the pH value of the system did not need to be adjusted continuously to convert the uncharged boric acid into the borate ion in the charged form owing to better manipulation of the pH by the DD system. Overall, the integrated MDC-DD system provided promising results, presenting effective boron-containing water desalination, yeast wastewater treatment, and enhanced energy production.