The TFFBR also contains a pump, by which the water flow rate can be controlled. The main advantages of this TFFBR are (i) its high optical efficiency, (ii) it’s simple construction

method and (iii) the low investment costs involved in development. Further advantages are that oxygen transfers effectively into the water film and there is no need for TiO2 separation from the treated water, in contrast to reactors based on TiO2 slurries. An understanding of the mechanism of microbial photoinactivation during solar photocatalysis comes mostly from studies of bacteria [5, 7, 21]. The most common photocatalytic inactivation mechanism described is based on inactivation due to hydroxyl radicals and other reactive oxygen species (ROS) when bacteria come in contact with a solar-excited photosensitiser. GSK690693 cost This photooxidation process Tozasertib mw causes cell membrane disruption and increase cellular permeability,

with significant cell damage that eventually results in complete inactivation of the bacteria [13]. The conventional approach to assessing the viability of bacteria during solar disinfection is to enumerate samples after exposure to sunlight, using conventional plate counts on a suitable agar-based growth medium with incubation of plates in standard aerobic conditions (e.g. 24 h incubation at a suitable temperature). However, recent studies have demonstrated that reactive oxygen species (ROS), derived mainly from aerobic respiration during the enumeration process, may inactivate sub-lethally Demeclocycline damaged bacteria and prevent their growth and enumeration under aerobic conditions [22]. Such injured cells can only be cultured and counted under conditions where reactive oxygen species are neutralised (ROS-neutralised conditions) e.g. by supplementing the growth medium with the peroxide scavenger sodium pyruvate and incubating under anaerobic conditions

to prevent cellular respiration, allowing the bacteria to grow by fermentation [22–24]. This approach was taken in the present study; uninjured bacteria were AZD1480 in vivo enumerated under aerobic conditions while uninjured plus injured (ROS-sensitive) bacteria were enumerated under ROS-neutralised conditions, with the difference between the counts under both sets of conditions representing the number of injured bacteria in the sample. Even though bacteria have received more attention than other groups of microbes in solar photocatalysis research, bacterial pathogens of fish have been largely ignored in these studies, prompting the study reported here. Aeromonas hydrophila is a Gram-negative bacterium, known to be a primary fish pathogen [25]. A. hydrophila tends to be virulent towards most cultured and wild freshwater fish, especially trout, salmon, carp, catfish and tilapia. Red fin diseases and haemorrhagic septicaemia are mainly associated with A. hydrophila [26]. Antibiotics and several vaccines have been used to treat these infections, but extensive use of antibacterial agents has caused A.