Trainees practicing operation of a Nomad water purification system capable of disinfecting about 100 litres of contaminated water per minute, GlobalMedic Training Day, Toronto, June 2011. The last pair of blue cylinders in the Nomad unit contain powerful ultraviolet light sources to render any remaining microorganisms in the processed water flow inert. Staff are taught to constantly monitor the water flow in order to change the filtration media when the cylinder filters clog up.