DISINFECTION OF DRAIN WATER BY MEANS OF UVC RADIATION - EXPERIMENTAL PROTOTYPES FOR SMALL FLOWS

In the present study two prototypes were constructed to adapt the different physical variables involved in the disinfection of lixiviates to their characteristics, their nature and flow, considering as well the economy of the process. A closed channel contact system prototype was chosen to increase the effectiveness of disinfection. This prototype consisted of a 75 W low-pressure mercury vapour lamp, wrapped in a steel case. With this kind of prototype, a complete disinfection of fungi, bacteria, viruses and weeds can be obtained with doses up to 40 mW s cm^-2 for flows up to 0.5 l s^-1. It is also possible to decrease the dose depending on the infectious agent. An open channel UVC reactor prototype was chosen, instead of the closed channel system, in order to eliminate lamp maintenance and obstacles (quartz cover) in the transmission. This prototype consisted of an UV lamp installed longitudinally over a 120 cm long horizontal steel tray through which a 2 mm film of lixiviates circulated constantly. With both prototypes, changing the voltage was an effective method to increase or to decrease the dose to a constant flow, without exceeding the limits of the working lamp. Considering the temperature inside the greenhouse, the UV reactor operated at a temperature close to its optimal efficiency. A clear advantage of this prototype was its cost, far below the price of commercial devices.