Energy-efficient removal of trace antibiotics from low-conductivity water using a TiO reactive electrochemical ceramic membrane: Matrix effects and implications for byproduct formation.

The inevitably high energy consumption of traditional electrochemical processes to treat low-conductivity water has limited their wider application. Herein, we present an energy-efficient alternative, i.e., a TiO reactive electrochemical ceramic membrane (TiO-REM) system with a superior mass transfer ability. For the removal of 10-200 μM norfloxacin (NOR) from low-conductivity (178-832 μS cm) water, the TiO-REM system increased the kinetics rate constant by 4.3-34.0 times, thus decreasing the energy cost by 80.5-97.3% compared with a flow-by system. The rapid NOR removal was related to the enhanced direct electron transfer process in the TiO-REM system, which allowed for higher resistance to HCO scavenging and a favorable reaction between NOR and the active sites. Meanwhile, this mechanism likely contributed to the less formation of inorganic chlorinated product, ClO, in the presence of Cl. Although organic chlorinated byproducts were not detected during NOR degradation in the TiO-REM system, Cl influenced the speciation of the intermediates. A single-pass TiO-REM system demonstrated 94-97% removal of trace antibiotics from real water samples in 30 s. The additional energy consumption (<0.02 kWh m) using a TiO-REM system only contributed to 5.0-6.4% of the total in a typical tertiary wastewater treatment plant. Based on the above results, we can conclude that the convection-enhanced REM technique is viable for the purification of low-conductivity natural waters.