UV-C gives biofouling protection
Biofouling, or the establishment of a biological layer on the surface of solid matter which is exposed to seawater, is a serious problem. It causes inaccuracies and technical difficulties in marine measuring, observing and monitoring programmes. TNO, the Dutch-based knowledge organization, conducted bioassay-based test programmes on turbidity sensors and SCUFA (Self-contained underwater fluorescent apparatus) sensors. The instrument trials were conducted in Den Helder and in a marina in the Netherlands using pulsed illumination with UV-C from a light source external to the instrument. The UV-C illumination regime was carried out at varying levels of illumination and using different on/off time periods. A UV-C illumination regime of one minute on followed by 59 minutes off was found to give full protection for the optical windows and almost complete protection of the surrounding housing. For future purposes, it is anticipated that this illumination regime can be reduced as a certain level of biofouling of instruments is acceptable. Further possible refinements include fitting a reflector around the bulb which will direct the radiation directly towards the target surface. This will reduce the power consumption and significantly reduce the potential risks to humans and non-target organisms. It is anticipated that the success of these trials need not be limited to the instruments tested. UV-C treatment of this nature can be extended to any other sensor surface that requires protection from biofouling; for example, in non-oceanographic applications in biomedical environments.