The Nitty Gritty Of Sediment Remediation

By Tammie Caldwell


Soils and sediments may become contaminated by diesel, petroleum, BTEX, polycyclic aromatic hydrocarbons (PAHs) and other volatile and semi volatile organic compounds. Sediment remediation is the process of neutralizing contaminants and restoring environments to their pre-contamination condition. There is a variety of treatment options available and the choice of which one to use depends on the nature of the contaminant and on the time and money that are available for the procedure.

Sedimentary contamination refers specifically to underwater soils. When the sediment underlying rivers and harbors becomes compromised, their navigational and recreational use is impaired. As of 2004, the Environmental Protection Agency estimated there were roughly 144 sites that required cleaning up. Sixty of these were considered major enough to require tracking at the national level, while others could be tackled by state or local authorities, by voluntary action or by other federal agencies.

Soil remediation is tackled by three basic approaches: monitored natural recovery, dredging and in situ capping. The sources of the contamination include mining and industrial accidents like oil leaks, chemical spills, etc. As well as the contaminants mentioned earlier, things like pesticides, metals and organometals, cyanide, pthalate esters and hydrocarbons in the form of PCBs and mononuclear aromatic hydrocarbons enter the soil environment.

Some of these substances are either completely insoluble or only partially soluble in aqueous solvents and end up becoming embedded in aquatic sedimentation. This means these poisons are indetectable in the water column. The organic content of these particles, their size and shape, and the ecology of benthic oranisms (bottom feeders) all promote the steady accumulation of contaminated sediments.

When a government agency such as a land remediation agency identifies an area to be decontaminated, or remediated, imminent action is arequired to protect the environment, not to mention human health. This process is subject to regulatory oversight. In the USA, this is the purview of the EPA, Region Nine.

The process of remediation goes down right to the level of nanotechnology. Specifically, nanoremediation refers to the use of nanoparticles. These are defined as particles between one and one hundred nanometers in size. One nanometer is equal to one billionth of a meter. Nanoparticles have a high surface area per unit mass, which makes them highly reactive. Their small size also allows them to infiltrate tiny pores in sediments, making target contaminants more accessible.

During the nanoremediation process, a decontaminant on the nanoparticle scale comes into contact with a target contaminant in a detoxification reaction. To date, the global nanoremediation project has identified up to 70 sites around the world that require this type of treatment. Currently, nanorem treatment has been used to clean up groundwater projects, although research is being conducted into using it for wastewater treatment.

What makes nanoremediation is the minute scale of the contaminants being removed. Any idiot can filter out junk the size of coffee grounds. Nanoparticles are too small to filter using available technology, and so that is why neutralizing chemical reactions are necessary. Once those are under control, maybe we can start tackling pico particles, which are one thousandth of a billionth of a meter.




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