Thiocyanates, do you have a problem or not?

Peter O. de Vries and Koen R. Weytingh

Abstract

In the Netherlands, concentrations of thiocyanates in groundwater are most commonly determined by subtracting the results of two analytical methods: The first one determining ‘all’ cyanides, including the thiocyanates. The second one determining only the ‘real’ cyanides, i.e. the iron and free cya-nides. Of course such an analysis is not very accurate. In the past only little attention has been given to thiocyanates as a specific contaminant at gasworks sites. Often only one of the two analytical methods has been used giving three categories of gasworks sites: Those at which the contamination with (iron) cyanides and thiocyanates are known both, those at which only the total contamination with cyanides (including thiocyanates) is known and those at which only the contamination with (iron) cyanides is known. As far as reliable data are available, it seems that thiocyanates are more frequently found in the western parts of the Netherlands than in the eastern parts. In this paper an over-view is given of thiocyanate data of 47 gasworks sites in the Netherlands and three hypotheses are formulated to explain the observed facts. The technical side of the problem however is not most troublesome. In a lot of cases decisions about remediation strategy have already been taken without recognizing the thiocyanate problem. To handle both, the remaining technical questions and developing an acceptable policy, a SKB-funded project has recently been started.

Key words: ammonia sulphate processing sludge, ammonia water, bog iron, gaswater, groundwater plume development, remediation policy, thiocyanate

© 2007 EPP Publications Ltd

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Article code 721