  A three-dimensional (3D) electrochemical flow-through reactor equipped with
GAC packed bed, polarized by the electric field, was evaluated for the removal
of persistent organic contaminants from real sewage effluent. The performance
of the reactor was investigated for 27 consecutive runs at two anodic current
densities, i.e., low current density (LCD) of 15 A m-2, and high current
density (HCD) of 100 A m-2. In the HCD experiments, the adsorption ability of
saturated GAC was increased, mainly due to the increase in the mesoporosity of
GAC. A synergy between electrosorption/adsorption on GAC and electrooxidation
was observed in terms of the removal of all target pollutants. DEET presented
the highest synergy, ranging from 40-57%, followed by iopromide (22-46%),
carbamazepine (15-34%) and diatrizoate (4-30%). The addition of GAC decreased
the concentrations of toxic chlorate and perchlorate by 2-fold and 10-fold,
respectively, due to their electrosorption on GAC. Also, 3D electrochemical
system yielded lower concentrations of adsorbable organic iodide (AOI) and
adsorbable organic chlorine (AOCl). Thus, addition of low amounts of GAC in
electrochemical systems may be a low-cost and simple way of minimizing the
formation and final effluent concentrations of toxic halogenated byproducts.
