SafeSed – Safe and non-destructive removal of contaminants from sediments
Funded by TUFFO, the Swedish Geological Institute research programme
In the TUFFO project SafeSed, an innovative technology is tested under Swedish conditions. The technology, SPEARS, removes the contaminants from sediments instead of digging up or covering contaminated sediments, with minimal impact on the ecosystem and the bottom fauna. The technology has been successfully tested in sandy sediments in the United States and Canada. The project will investigate how the method's efficiency is affected by the content of organic material in the sediment, for example in fiber banks with very high levels of organic content, and at low temperatures.
The initial development of the Sorbent Polymer Extraction and Remediation System, SPEARS, was done at NASA and removes the contaminants from the sediments with minimal impact on the ecosystem and the bottom fauna. The SPEARS are filled with ethanol and placed in the contaminated sediments where the organic pollutants pass into the SPEARS spikes and can then be removed from the sediments. The pollutants accumulate in the ethanol where they can be catalytically destroyed.
SPEARS has mainly been used in sandy sediments with low content of organic material in the USA and Canada and this project will investigate how the method's efficiency is affected by the content of organic material in the sediment, for example in fiber banks with very high levels of organic content, and the relatively cold Swedish temperature conditions. SPEARS sit together in flexible "mats" with holes that allow interaction between sediment and water. The mats help during the deployment and retrieval of the SPEARS, and prevent them from coming loose from the sediments and floating away.
Other pollution profile
Industrial activities differ between countries, and thus also the pollutant composition. SPEARS has primarily been used on PCBs and PAHs, while in Swedish sediments dioxins from pulp and paper industry are often the main contaminants. The project will investigate the efficiency that can be achieved for these pollutants and also to what extent SPEARS can be used for organometallic pollutants such as TBT and methylmercury.
Circularity and costs
Today, SPEARS are made of plastic, and has a limited service life, which is not optimal from a circularity perspective. The SafeSed project will investigate how to increase the circularity of SPEARS and reuse or recycle the plastic in the SPEARS. It is also an objective of the project to produce approximate costs for using SPEARS in Swedish conditions.
Field deployment and lab trials
During autumn 2021, the project also carried out successful field deployments of SPEARS in Swedish waters, outside Bureå, Skellefteå. The deployment was carried out as a collaboration between Umeå University, SWECO and ecoSPEARS, with infrastructure and staff from Umeå Marine Research Center. The SPEARS will remain in the sediments at least until autumn 2022 and possibly even longer. In parallel with the field study, several long-term experiments are underway on a lab scale, with different types of sediment and pollution profiles.