Summary and Conclusions, Miljøstyrelsen

Afvaskning og afslibning af biocidholdig bundmaling i forbindelse med vedligeholdelse af lystbåde på land

Summary and Conclusions

Environment-friendly cleaning of bottom paint
Examination of the environmental impact in autumn cleaning
Possibilities of reducing the environmental impact from autumn washing

Before pleasure boats are painted in the spring, some boats need to have old bottom paint removed first. The typical cause of this is a build up of many layers of old bottom paint through the time. It is a problem, because the surface cracks and peels off and constitutes, therefore, a poor basis for a new layer of paint. In the project, cleaner technology has been tested and evaluated for a reduction of the pollution in connection with the removal of old bottom paint with biocide contents. The environmental gain from this has been examined.

When pleasure boats are taken ashore for the winter, the bottom is normally washed to remove slime and growth of algae, if any. During this washing, remaining bottom paint might be removed, which could have an environmental influence. Not many data are available showing the extent of this influence, nor if modern and less polluting bottom paints have a comparably smaller environmental impact. In the project, the environmental impact in connection with the autumn washing of pleasure boats, painted with bottom paint with biocide, has been examined through concrete tests. In continuation of that, the possibility of a reduction of the environmental impact from washing has been examined, among other things through a series of cleaning tests. The purpose of these tests has partly been to examine the environmental impact in connection with washing and cleaning of pleasure boats and partly to come up with some recommendations how to minimise or eliminate the environmental impact.

Environment-friendly cleaning of bottom paint

The most common methods and technologies that are used today to remove old bottom paint cause pollution at places where the boats are taken ashore for the winter, since scrapings, dust etc. are not normally collected. Therefore, new and cleaner methods are wanted for spring-cleaning of pleasure boats, which can minimise inappropriate environmental impact through a reduction of the amounts of waste as much as possible.

In the project, cleaner technology solutions for cleaning of bottom paint have been identified and tested. In practice they have turned out to be effective and usable seen from an environmental point of view as well as from the users point of view.

The project has shown that in fine sanding (only the top layer of bottom paint is removed), 3.5 kg are removed on average from a 30 feet boat. If all paint is removed down to the primer, 10 kg is removed on average. If both paint and gel-coat is removed (is typically done if the boat has fibre glass plague) about 24 kg are removed.

The copper content of the removed amounts is on average 22% (for fine sanding and removal of all bottom paint down to the primer).

Compared with the methods used today, the copper pollution ashore during the winter is reduced considerably if the tested methods are used. The amount that is dropped ashore can on average be reduced by 99%.

To the users, the new methods also present working environmental advantages as they avoid dust into their lungs. In general, the responses from the persons who tested the different equipment have been positive. There has been general agreement that the individual equipment is both effective and usable for the three types of cleaning.

A series of recommendations have been made for the choice of equipment, and based on the experience from the project, one piece of equipment will be bought per 100 boats as a rule of thumb. One piece of equipment is to be understood as a vacuum scraper, a random orbital sander and a vacuum cleaner complete with pipe and pipe sleeve. Such a piece of equipment can be acquired for between 7.000 – 13,500 dkr. VAT excluded, depending on the choice of vacuum cleaner and random orbital sander.

Examination of the environmental impact in autumn cleaning

The environmental impact when cleaning has been clarified through practical cleaning tests in the harbour of Kalvehave. A temporary place for washing down was established for this purpose to collect the slops. In the autumn of 2001, 22 boats were hoisted above the tarpaulin and washed down. After each wash, samples were taken of the slops and the deposits, which were later analysed for copper. The washing test has shown that there is no clear connection between the amount of copper washed off and the sailing activity, the applied amount of paint, the amount of water used for washing and the product respectively.

On the other hand, the condition of the bottom surface is of decisive importance in respect of the amount of copper that is washed off. From cracking and peeling bottoms, more copper is washed off. Therefore, to avoid an unnecessary environmental impact, it is important that the boat owners maintain the bottom regularly before applying new paint.
To ensure that, the following rules must be observed:

The surface must not be cracked, uneven or peel off. If it does, it is scraped or sanded till it is smooth. In doing so, a good adhesive power is obtained.

Avoid a build up of too many layers of paint through a regular removal of old layers.

Analyses of copper in aqueous phase and deposit show that the major part (99%) is found in the deposit. Therefore, to obtain a good cleaning of the slops it is important to try to separate the deposit in order to collect it.

On average, 6 g of copper are washed off per boat out of total applied amount of 0.9 - 3.7 kg. The total environmental gain from collecting the slops is modest from an overall point of view.

The potential for environmental improvements is 1 ½ - 7 per thousand compared to the total applied amount of copper (the major part is released during the sailing season). 60 g of copper can be collected per 100 boats.

Possibilities of reducing the environmental impact from autumn washing

The possibilities of cleaning the slops, with a view to discharging the cleaned water to recipient, have been examined in the project. Today a number of marinas in Denmark have established a place for washing and subsequent cleaning of pleasure boats. All the equipment has been adjusted in accordance with outdated requirements. It has been demonstrated that the used technologies most probably will not be able to meet the present requirements.

Through cleaning tests, the aim has been to obtain a result that in all probability meets the current requirements. In the test the aim has been to reach a concentration of 2.9 micrograms of copper/l even though the requirement not necessary demand such a low concentration.

The tests showed that a simple cleaning, where the slops are filtrated first and then pass through a charcoal filter, is not sufficient to obtain the wanted final concentration of 2.9 micrograms of copper/l. Neither does the method meet the requirement of 0.5 mg of copper/l for several of the existing types of equipment.

However, with a method, based on chemical precipitation, a degree of treatment of 99.5% has been obtained along with a final concentration of 10 micrograms of copper/l. We must conclude that the cleaning is very effective. This method is more complicated as it involves the addition of polymers and precipitant, stirring etc., but the final concentration is the same as or lower than the copper content in the tap water that was used for cleaning, (the concentration of tap water was 10-80 micrograms of copper/l). The requirement for drinking water is by way of comparison 2000 micrograms of copper/l after 12 hours in the water pipes. When water is conducted into the installation of a house/harbour the requirement is 100 micrograms of copper/l.

Theoretically, the method of chemical precipitation will be able to clean down to around one microgram of copper/l. Based on the test experience of this method, a concept has been made for the construction of an equipment for cleaning of slops. An estimated price for such a piece of equipment would be 50,000 – 70,000 dkr., depending on the capacity, with some running annual expenses of 4,000 – 5,000 dkr. To this should be added expenses of guidance for dimensioning and operation. Finally, costs of establishing the cleaning place itself should be added. Experience shows that the costs here would amount to 250,000 – 1,000,000 dkr., (included is the establishment of cleaning, which amounts to 80 – 600,000 dkr.).

For marinas, including new marinas, which are considering establishing collection and cleaning of slops from autumn washing, a number of recommendations have been made. Based on the experience from existing cleaning places and the washing/cleaning tests, they comprise a number of conditions that marinas should consider and evaluate.