The deployment of photocatalysis for remediation of water has not yet been realized, although laboratory-scale studies have demonstrated promise. Accomplishing this requires the development of photocatalysis as a process, including studying its efficiencies in remedying water when high volumes of water are processed, and addressing the recovery, possible regeneration and reuse of the photocatalysts. To that end, this work is aimed at demonstrating the use of a custom-built mobile platform for disinfecting large quantities of water. The benchtop platform built is capable of processing 15.14 L (4 gallons) per minute of water, with possibility for further scale-up. Preliminary studies on the catalyst recovery, regeneration and reuse via gravity-assisted settling, centrifugation and air plasma treatment indicated that 77% of Aeroxide^® P25 titania (TiO₂) nanoparticle and 57% of porous TiO₂ nanowire photocatalysts could be recovered and regenerated for further use. Overall, this study indicated that process improvements, including increasing the kinetics of the photocatalysis, and optimization of the efficacies of the catalyst recovery and regeneration processes will make it useful for water remediation on any scale. More importantly, the portable and flexible nature of the benchtop photocatalysis system makes it amenable for use in conjunction with existing technologies for remedying large quantities of water.

Use of cell motility studiesand particle-tracking algorithmsfor evaluating photocatalysis-assisted water disinfection kineticsin real time is presented. Photocatalyst-microorganism interactions,phenomenological models of disinfection kinetics, and disinfectionmechanisms are also discussed. The current methods used to study photocatalysis-assistedwaterdisinfection at a laboratory scale may not lead to process scale-upfor large-scale implementation. These methods do not capture the processcomplexity and address all the factors underlying disinfection kinetics,including the physical characteristics (e.g., shape and size) of thephotocatalyst, the light intensity, the form of the catalyst (e.g.,free-floating and immobilized), and the photocatalyst-microorganisminteraction mode (e.g., collision mode and constant contact mode).This drawback can be overcome using in situ methods to track the interactionbetween the photocatalysts and the microorganisms (e.g., Escherichia coli) and thereby engineering the resultingdisinfection kinetics. Contextually, this study employed microscopyand particle-tracking algorithms to quantify in situ cell motilityof E. coli undergoing titanium dioxide(TiO2) nanowire-assisted photocatalysis, which was observedto correlate with cell viability closely. This experimentation alsoinformed that the E. coli bacteriuminteracted with the photocatalysts through collisions (without sustainedcontact), which allowed for phenomenological modeling of the observedfirst-order kinetics of E. coli inactivation.Addition of fluorescent-tagging assays to microscopy revealed thatcell membrane integrity loss is the primary mode of bacterial inactivation.This methodology is independent of the microorganism or the photocatalysttype and hence is expected to be beneficial for engineering disinfectionkinetics.