FAQ Topic

Q: How to deal with fouling?

You can now order a mechanical cleaner that wipes the sensor to maintain transparency.

The mechanical cleaner is designed to operate for months on the internal batteries of the SediMeter, thus extending the stand-alone logging interval manyfold in fouling environments. The microprocessor controls the cleaner movement to prevent it from touching and disturbing the bottom.

The photos show what can happen in the perhaps worst possible case, a shallow nutrient-rich tropical sea just off Miami. Fortunately, even in this extreme case the lowest 10 cm or so remained clean. It is apparent that the leaves and sand grains that got swirled around by the waves prevented the organisms from getting a foothold. The effectiveness of this frequent but low-intensity cleaning is what gave us the idea to our wiper.

The microprocessor can determine both the position of the bottom, and of the wiper, by reading its SediMeter sensor. Thus it can move the wiper slowly to a short distance above the bottom and return it up, without disturbing the bottom. This was a design requirement in order for the cleaner to not disturb soft bottoms or mud layers.

After two years of studies and investigations to develop the optimal method for keeping the SediMeter sensor clean, we feel that this solution will fulfill all the reuirements for using the instrument in environmental monitoring, such as supervising siltation around areas of sediment spill when dredging.

Contact us for more information.

Day 0: At 6 m depth in 27 ºC with no anti-fouling treatment. Off Cape Florida outside Miami. Past beach replenishment projects, and nutrients from land, probably contribute to poor visibility.	Day 24: Algae and barnacles cover everything except the lower part of the sensor.
Day 24: Close-up of the sensor. Enough backscatter detectors are still visible for it to continue measuring the bottom level. No biofouling occurred on the sensor inside, only on the outer holder tube.	2 m depth, same area, day 9: This sensor also escaped biofouling in the lowest section. The photo was taken on a relatively calm day, and still sand grains swirl around the sensor with every wave. It appears this kept it from biofouling.

Bio-fouling is not a problem in all places or at all times. For instance, several months of deployment under the ice in a temperate lake, at 2 m depth, produced no bio-fouling whatsoever. The same for 2 summer weeks at 21 m depth in the southern Baltic Sea. For fouling of benthic fauna to occur, there must be an event of larvae settling. In some waters this only happens once per season, but in tropical waters it happens often. For fouling of algae and slime (which depend on photosynthesis) to occur, there must be sufficient light.