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FP5

BRIMOM Report Summary

Project ID: EVR1-CT-2002-40023
Funded under: FP5-EESD
Country: Netherlands

Protection of oceanographic instrumentation from biofouling using external UV-C

Pulsed illumination of the surface with UV-C from a light source external to the instrument is a very effective way to protect free-standing deployed oceanographic instruments from biofouling.

Based on bioassay based test programs TNO conducted a range of full-scale instrument trials with UC-C protected turbidity sensors and SCUFA fluorescence sensors. The trials with the turbidity sensor were conducted in flow-through systems with natural biofouling pressure and in the Harbor of Den Helder (NL). The SCUFA tests were conducted in Den Helder Harbor and in a marina on Helgoland (DE). Six runs with UV-C protected turbidity and fluorescence sensors were conducted with varying UV-C illumination regimes (ranging from 45 min on/15 min off to 1 min on/29 min off). In all cases the result was comparable: reference surfaces and non-protected instruments became heavily fouled within a few weeks, resulting in rapid instrument failure. The protected instruments were effectively protected by the UV-C illumination and continued to perform well.

A UV-C illumination regime of 1 min/59 min off gives 100% protection of the optical windows and a nearly 100% protection of the surrounding housing as shown in the trials. 100% effectiveness is not needed, as some degree of biofouling is acceptable. The illumination regime can therefore easily be reduced further, especially when combined with a periodic UV boost to kill any fouling that may have settled. The currently used Pen-rays provide good protection, but the radiation is not very effective as the radiant energy is spread in all directions. Fitting a reflector around the bulb will direct the radiation towards the target surface. This will reduce the power consumption. It will also significantly reduce the potential risks to humans and non-target organisms.

UV-C has been used successfully by TNO for protecting turbidity sensors and SCUFA fluorescence sensors, but the results can be fully extrapolated to any other sensor surface that needs protection. The lifetime of the system is in fact only limited by the durability of the UV bulbs and the available power source.

Related information

Contact

Peter WILLEMSEN, (Senior project manager)
Tel.: +31-223638856
Fax: +31-223638888
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