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Increasing Desalination by Mitigating Anolyte pH Imbalance Using Catholyte Effluent Addition in a Multi-Anode Bench Scale Microbial Desalination Cell
journal contribution
posted on 2013-09-03, 00:00 authored by Robert
J. Davis, Younggy Kim, Bruce E. LoganA microbial
desalination cell (MDC) uses exoelectrogenic bacteria
to oxidize organic matter while desalinating water. Protons produced
from the oxidation of organics at the anode result in anolyte acidification
and reduce performance. A new method was used here to mitigate anolyte
acidification based on adding non-buffered saline catholyte effluent
from a previous cycle to the anolyte at the beginning of the next
cycle. This method was tested using a larger-scale MDC (267 mL) containing
four anode brushes and a three cell pair membrane stack. With an anolyte
salt concentration increased by an equivalent of 75 mM NaCl using
the catholyte effluent, salinity was reduced by 26.0 ± 0.5% (35
g/L NaCl initial solution) in a 10 h cycle, compared to 18.1 ±
2.0% without catholyte addition. This improvement was primarily due
to the increase in buffering capacity of the anolyte, although increased
conductivity slightly improved performance as well. There was some
substrate loss from the anolyte by diffusion into the membrane stack,
but this was decreased from 11% to 2.6% by increasing the anolyte
conductivity (7.6 to 14 mS/cm). These results demonstrated that catholyte
effluent can be utilized as a useful product for mitigating anolyte
acidification and improving MDC performance.