C.M. Werner, C. Hoppe-Jones, P.E. Saikaly, B.E. Logan, G.L. Amy
Water Research, volume 73, 56-67, (2015)
Bioelectrochemical systems, Trace organic compounds, Biotransformation, Sorption
Microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are
two types of microbial bioelectrochemical systems (BESs) that use
microorganisms to convert chemical energy in wastewaters into useful
energy products such as (bio)electricity (MFC) or hydrogen gas (MEC).
These two systems were evaluated for their capacity to attenuate trace
organic compounds (TOrCs), commonly found in municipal wastewater, under
closed circuit (current generation) and open circuit (no current
generation) conditions, using acetate as the carbon source. A biocide
was used to evaluate attenuation in terms of biotransformation versus
sorption. The difference in attenuation observed before and after
addition of the biocide represented biotransformation, while attenuation
after addition of a biocide primarily indicated sorption. Attenuation
of TOrCs was similar in MFCs and MECs for eight different TOrCs, except
for caffeine and trimethoprim where slightly higher attenuation was
observed in MECs. Electric current generation did not enhance
attenuation of the TOrCs except for caffeine, which showed slightly
higher attenuation under closed circuit conditions in both MFCs and
MECs. Substantial sorption of the TOrCs occurred to the biofilm-covered
electrodes, but no consistent trend could be identified regarding the
physico-chemical properties of the TOrCs tested and the extent of
sorption. The octanol–water distribution coefficient at pH 7.4 (log DpH 7.4) appeared to be a reasonable predictor for sorption of some of the compounds (carbamazepine, atrazine, tris(2-chloroethyl) phosphate and diphenhydramine) but not for others (N,N-Diethyl-meta-toluamide).
Atenolol also showed high levels of sorption despite being the most
hydrophilic in the suite of compounds studied (log DpH 7.4 = −1.99).
Though BESs do not show any inherent advantages over conventional
wastewater treatment, with respect to TOrC removal, overall removals in
BESs are similar to that reported for conventional wastewater systems,
implying the possibility of using BESs for energy production in
wastewater treatment without adversely impacting TOrC attenuations.