Hybrid UV-C/microfiltration process in membrane photoreactor for wastewater disinfection

A novel hybrid UV-C/microfiltration process for water disinfection is presented, and its application in continuous mode operation to the removal of different pathogen germs ( Escherichia coli , Enterococcus faecalis , and Candida albicans ) present in urban wastewater. The membrane photoreactor is based on porous stainless steel membranes coated with a TiO 2 layer and illuminated by a UV-C lamp (254 nm). A valve actuator in the outlet of the UV-C stream allows operation of the system under conditions of constant transmembrane pressure (TMP) keeping the UV-C contact time in few seconds, significantly lower than the typical irradiation time employed in TiO 2 photocatalytic processes. An E . coli removal of up to 4-log in the permeate stream and up to 2-log in the UV-C outlet was achieved with a 0.2 μm membrane operating with a TMP of 0.5 bar and a UV-C contact time as low as 8 s. The microbial balance data from the cells recovered from the membrane confirmed that 96–98% of the removed microorganisms died due to the UV-C action over the membrane surface. Modification of the membrane with a TiO 2 layer has been also shown to be a suitable way to improve both the UV-C inactivation and the filtration efficiency. The results reported in this work constitute a proof of concept of the synergy between UV-C and filtration that can be achieved in a hybrid UV-C/microfiltration system, being a good example of process intensification where two products of different quality can be simultaneously obtained.