Anticorrosion packages consisting of a biocide and oxygen scavenger may be added to linefill waters during hydrostatic testing to prevent microbially enhanced and oxygen induced corrosion. For offshore applications there are clear advantages in using anticorrosion packages which are acceptable for discharge to sea without treatment. This paper outlines an approach used to assess the antimicrobial performance and toxicity to environmentally relevant marine organisms of 7 anticorrosion packages and their components.

Antimicrobial performance was assessed by long term inhibition tests with both marine general heterotrophic (GH) and sulphate reducing bacteria (SRB). These results have been compared with those obtained from 15 minute Microtox* tests with the marine luminescent bacterium (Photobacterium phosphoreum).

The toxicity of the candidate packages and their components were determined in acute tests with the brown shrimp (Crangon crangon), a calanoid copepod (Acartia tonsa) and embryos of the Pacific oyster (Crassostrea gigas).

When tested singly, the minimum inhibitory concentrations (MIC) for all but one biocide varied between 20 and 400 mg 1-1. However, only four biocides performed adequately (MIC < 500 mg l-1) for both GH and SRB when tested as mixtures with the oxygen scavenger. Similar trends were found when P. phosphoreum was used to assess antimicrobial performance.

The acute toxicity of the most toxic chemicals to the most sensitive species and the least toxic chemicals to the least sensitive species varied by a factor of 10 000. However, the rank order of toxicity of the chemicals was similar for each of the three species and there was no apparent correlation between the toxicity of the chemicals to the marine species and their antimicrobial performance.

These results enabled an effective anticorrosion package with low toxicity to relevant marine species to be identified from the candidate packages.

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