Abstract

The Elf company has developed a preventive means of fighting oil spills, involving a film forming product which must be applied to areas to be protected before they are reached by hydrocarbons. The goal is to reduce the adhesiveness of hydrocarbons, thus minimizing their ecological and aesthetic impact on coastal zones. The effectiveness of the product has already been tested by means of various experiments carried out on miscellaneous substrata. Simply washing the area with cold water under low pressure is sufficient to detach the oil from soiled surfaces where, usually, it is necessary to resort to high pressure hoses (possibly using hot water or even detergents). It is then possible to envisage, using traditional methods, to recover the petrol from the surface of the water.

This paper discusses the results of impact studies which were carried out recently in various coastal ecosystems: sandy, rocky and salt-marsh sediments. Follow-up of sedimentary fauna and marsh flora have not revealed any impact, not even on the most sensitive ecosystems.

Procedures for applying the film forming product using tools available in stocks of prevention equipment are also discussed. An experiment timetable has made it possible to optimize the next use of a spreading system using helicopters (Simplex), commonly used to apply dispersants.

Introduction

Concerned to develop a procedure to protect coastlines against accidental hydrocarbon spills, the Elf company has perfected a product which constitutes a preventive means. This is a film forming product. This type of product is designed to be spread over the coast shortly before the petrol runs aground. Currently, only very few similar products exist. Some of these products are micro organisms which must be added to the surface of a sediment in a natural ecosystem. Others form a film which is not easily biodegradable and are therefore likely to damage the ecosystem. This product is of natural origin (polysaccharides). The characteristics of the polysaccharides used allow complexing with natural calcium and therefore better adhesiveness to the surface of the sediments to be protected. The other advantage of the product presented in our study is that it is rapidly biodegradable. This biodegradability is the reason why the product looses its effectiveness with time, although it nevertheless remains very efficient 6 days alter application to an inter-tidal area.

The protection ensured by the film-forming product and the preservation of its effectiveness have previously been demonstrated during numerous experiments in the laboratory and in situ (90% protection for calcareous surfaces). These results were presented during the previous symposium (OME 1995).

As the effectiveness of the product had been proven, it remained to assess any possible ecological impact, as well as methods of using it. This paper therefore presents the results of the impact study on a coastal shoreline and the process implementation protocol.

Impact study

As the purpose was to ensure that the film-forming product was not harmful to the natural surroundings, in situ tests were carried out under conditions which, as far as possible, were similar to a real utilization and the possible impact on the fauna and flora of the tested sites was monitored.

The CEDRE entrusted monitoring of the potential impact of the process to two university organizations which have specialized in this field since the accident of the Amoco Cadiz: the Marine Biology Laboratory of the University of West Brittany (Dr. C. Le Guellec) and the Botanical Laboratory of the University of Rennes I (Dr. J.E. Levasseur). P. 111

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