Chapter 9 - How Far Are We From Large-Scale PMR Applications?

Abstract

Despite extensive research on several aspects of photocatalytic membrane reactors (PMRs) and their well-recognized attributes, no significant large-scale applications have been reported in the area of water treatment. A comprehensive assessment of the three components of this potential technology (i.e., photocatalysts, light source, and membranes) and their interaction suggests that the respective technology readiness level (TRL) is relatively low (at ∼4 to 5) at present; therefore, substantial development work is required to render PMR systems attractive and ready for commercialization (with TRL=9). These efforts should be guided by the need to develop a modern sustainable technology, satisfying economic, environmental, and social criteria. In pursuing PMR process development toward commercialization, significant research and development (R&D) is required (with emphasis on pilot plant testing and demonstration in real environments) to optimize key design and operating parameters, including apparent quantum efficiency, photocatalyst concentration, and hydraulic residence time. Priorities of R&D on technical issues are recommended. After PMR pilot-scale testing/demonstration, it will be possible to determine process economic and environmental indicators (i.e., total processed water unit cost, CO2/environmental footprint) with good accuracy. In general, because of the modular-type PMR components, no significant scale-up issues are foreseen and the steps toward PMR full-scale development appear to be straightforward. However, the pilot PMR data have to be fairly accurate and the respective performance indicators have to be attractive because such a novel hybrid process would compete for a place in a market characterized by conservatism and well-entrenched conventional processes, operating with fair reliability for a long time. Nevertheless, some distinct advantages of the novel PMR systems, over conventional techniques, particularly in respect of overall environmental performance emphasized in recent year (e.g., elimination or minimization of sidestreams, no addition of oxidants), may prove decisive in favor of large-scale PMR applications.