Active Geosynthetic Composites for subaqueous capping
Subaqueous contamination in harbours and waterbodies close to former industrial sites pose an ongoing threat to the environment. The contaminants found at these sites have low solubility products and therefore stay in place causing a low but steady contamination of the water for a long time. The usual remediation technologies used in these cases are in-situ capping or dredging, dewatering and disposing of the sediments to a landfill. To run dredging operations, onshore support is required to dewater the sediments and if necessary also to treat the water prior to discharging it back.
In-situ capping can be an additional or an alternative operation to dredging. In this process sand is used to cap the contaminants in place isolating them from the water. To improve the cap performance active materials like bulk activated carbon can be added as first layer on top of the contamination. They do not only cap the contaminated sediments but also treat them. The type and amount of active material used depends on the type and concentration of contaminants. The problem with these two operations is that they include high installation expenses as the granular capping material sediments slowly to the ground and requires divers to ensure a constant thickness. Currents and underwater inclinations also complicate the installation. When using bulk active materials an especially high coefficient of safety needs to be applied to ensure a minimum active layer thickness throughout the entire cap. On the other hand where the cap ends up being thicker there is an impact on ship transport as the navigable depth is reduced.
This study outlines that the combination of active materials and geotextiles can be an additional solution for the treatment of subaqueous contaminated sites. A composite product of geotextiles and active materials can be used for in-situ active capping. The combination ensures easier installation and lower quantities of material as a constant layer thickness can be guaranteed independently from water currents and inclinations. This also reduces the impact on the navigability of the water body. The study also illustrates the performance of different active materials on different contaminants.
The combination of geotextiles and active materials provides an additional solution for many varied environmental engineering projects. The contaminant binding feature and the spectrum of active materials ranging from activated carbon and zeolites to different polymers combined with the mechanical and chemical stability of geotextiles ensures an even broader field of application.