Tube-in-tube membrane microreactor for photochemical UVC/H2O2 processes: A proof of concept

This work proposes a disruptive tube-in-tube membrane microreactor for the intensification of photochemical UVC/H2O2 processes, towards contaminants of emerging concern (CECs) removal from urban wastewaters. The main novelty of this system relies on the radial addition of H2O2 through the porous membrane into the annular reaction zone, providing a more homogeneous distribution of the injected chemical across the whole reactor length. The proposed novel reactor consists of a ceramic ultrafiltration membrane inner tubing and a concentric quartz outer tubing that compose the annulus of the reactor (path length of 3.85 mm). The ultrafiltration membrane is used as a dosing system to deliver small amounts of H2O2 into the annulus of the reactor. In the annulus, where a 2 mg/L of oxytetracycline (OTC) solution flows, UVC light is provided via four mercury lamps located externally to the outer tube. The helical motion of OTC solution around the membrane shell-side enhances H2O2 radial mixing. The efficiency of the photochemical UVC/H2O2 process was evaluated as a function of the OTC flowrate, H2O2 dose, H2O2 dosage method and water matrix. OTC removal efficiencies of ~36% and ~7% were obtained for a synthetic OTC solution and an urban wastewater fortified with the same OTC concentration, using a H2O2 dose of 15.8 mg/L. Besides providing a good performance using low UVC fluence (34 mJ/cm2) and reactor residence time (4.6 s), the reactor has the advantage of an easy upscaling into a real plant by integrating multiple parallel membranes into a single shell.