In considering treating large volumes of water, as in aquaculture systems, it is obvious that flow rate will be a crucial parameter. A pilot-scale CPC reactor using TiO2 in suspension with different flow rates has been used to study the inactivation of Fusurium sp. spores [18]; achieving the highest inactivation
rate of Fusurium spores at a flow rate of 30.0 L min-1 with added TiO2 at 100 mg L-1 concentration. However, such systems require separation of the suspended TiO2 after treatment, which adds to the complexity, in contrast to immobilised systems such as the TFFBR. Another recent solar disinfection study also showed the importance of evaluating different parameters including: flow rate; water volume within the reactor; temperature; and solar energy [32]. They used a CPC reactor with no added Selleckchem NVP-BSK805 TiO2 and suggested that increasing Torin 1 in vivo flow rate has a substantial negative effect on the inactivation of bacteria, which is in agreement with the flow rate investigations of the present study. Here, the lowest flow rate of 4.8 L h-1 was found to be the most effective for inactivation of A. hydrophila ATCC 35654 as the residence time of 2.5 minin the 4.8 L h-1 experiment is almost twice as high as the 8.4 L h-2 experiment.(86 s) Similarly, when the
total sunlight intensity is at average of 1000 W m-2, the cumulative energy, 150 KJ m-2 at 4.8 L h-1 is higher than that of 86 KJ m-2 at 8.4 L h-1 which will play a major role A. hydrophila inactivation. In this study, the water temperature in the reservoir was maintained at (22-23)°C throughout the experiments. Due to the open structure of the TFFBR, the temperature of the water on the reactor plate was not measured, though it is logical to expect that it would be positively related
to sunlight intensity. Conclusion The results clearly demonstrate that high sunlight intensities (> 600 W m-2) and low flow rates (4.8 L h-1) provide optimum conditions for the inactivation of the fish pathogen A. hydrophila ATCC 35653, with fewer injured (ROS-sensitive) cells under such conditions than at lower sunlight intensities. Using a TFFBR system Pyruvate dehydrogenase to disinfect these bacteria under natural sunlight is a novel and alternative approach to conventional chemical disinfectants and antibiotics for control of this pathogen. The present study is also the first to report sub-lethal injury for a solar photocatalytic system at low sunlight intensities (< 600 W m-2), which places a question mark over conventional aerobic counts under such conditions and demonstrates that ROS-neutralised conditions are required to enumerate survivors of solar photocatalysis at low sunlight levels. However, conventional aerobic counts should be effective in enumerating A. hydrophila ATCC 35653 surviving a TFFBR system operating under high sunlight conditions, making it easier to assess efficiency under such conditions.