Publication Abstract

Remediation techniques applied to reduce paint-derived TBT in dredged material.

Remediation techniques applied to reduce paint-derived TBT in dredged material.

J.Reed, M.J. Waldock, B.J. Jones, S.J.Blake, P.Roberts, G.Jones, C.Elverson, S. Hall, & L.A.Murray

Since the TBT ban on small vessels (<25m) in the UK, there has been a general decrease in TBT concentrations at most impacted sites. However, a historic legacy of TBT contamination remains at a number of locations around the UK. Today paint-derived TBT in harbour sediments provides an ongoing source of contamination. MAFF as the regulatory authority for sea disposal of dredged material in England and Wales has funded CEFAS to investigate the distribution of TBT as sediment-entrained paint particles and initiated research to develop remediation methods to mitigate environmental harm. The aim of this study is to remediate sediments to increase the amount of the sediment that is available for conventional disposal whilst the isolated contaminated material can either be subjected to further remediation (i.e., biological or chemical methods), sent to landfill or placed in a contained site. The study has focussed on rapid methods for remediation and a number of different physical and chemical separation techniques have been evaluated. Experiments have been conducted on sediments spiked at two different concentrations (1 and 10 mg kg^-1) of TBT and samples taken from contaminated environments (4 mg kg^-1 TBT) from the River Tyne. Preliminary results are encouraging and it has proven possible to isolate a heavily contaminated component of the sediment leading to a significant reduction in the volume of grossly contaminated material. Samples were fractionated by size and density using froth flotation and density separation techniques and it was possible to visually identify paint particles in the large/light samples (250 - 500 µm). The results generally show that the highest concentrations of TBT (i.e., paint particles) are associated with the light fractions. This is particularly evident from the field sediment sample. Here, elevated TBT levels within the light fraction were confined to the > 63 µm size fraction. The results suggests that Tyne sediments contain larger paint particles than previously suspected. Initial results suggest that it may be possible to enhance isolation of contaminated material by these two techniques. Further method development is ongoing to increase the proportion of TBT-enhanced material removed from the bulk sediment.

Reference:

J.Reed, M.J. Waldock, B.J. Jones, S.J.Blake, P.Roberts, G.Jones, C.Elverson, S. Hall, & L.A.Murray. 2002. Remediation techniques applied to reduce paint-derived TBT in dredged material. pp 331-338 In: Proceedings of the Conference, Remediation and Beneficial Reuse of Contaminated Sediments, Venice 10-12 October 2001

J.Reed*, M.J. Waldock,* B.J. Jones*, S.J. Blake*, P.H. Roberts, G. Jones*, C.Elverson, S. Hall and L.A.Murray*

pp 331-338 In: Proceedings of the Conference, Remediation and Beneficial Reuse of Contaminated Sediments, Venice 10-12 October 2001