Site remediation deals with the removal of contaminants from soil and/or groundwater for the general protection of human health or from a brownfield site intended for redevelopment. Contaminants at a remediation site can be classified into one of two categories: a light non-aqueous phase liquid or a dense non-aqueous phase liquid.
A light non-aqueous phase liquid (LNAPL) is less dense than water and has relatively low solubility in water. Examples of LNAPLs include gasoline, diesel, and many other petroleum hydrocarbons. Contamination from LNAPLs is present at many petroleum handling facilities, including gas stations, pipelines, refineries, military bases, and storage facilities.
Being lighter than water, released LNAPLs tend to settle on groundwater and spread out. Over time, some contaminants slowly dissolve in the groundwater as well. The contamination has three main forms: free-phase product, LNAPLs dissolved in groundwater, and LNAPLs intermingled with soil in the unsaturated zone above the water table. For the removal of these three main forms of LNAPL contamination, some of the LNAPL remediation technologies include: Soil vapour extraction systems, Multi-phase extraction systems, Pump and treat systems, Vacuum-enhanced pump & treat systems, Air sparge systems, Bio-remediation systems and Chemical oxidation systems.
The specific LNAPL remediation technology chosen is dependent on the application, the site geology and other site conditions, and the treatment time-frame. The links on the left direct you to some of the various applications involving LNAPL contamination; on the right are links to appropriate LNAPL remediation technologies.
A dense non-aqueous phase liquid (DNAPL) is heavier than water and has low solubility in water. Examples of DNAPLs include industrial solvents like TCE (trichloroethylene) and PCE (perchloroethylene), manufacturing compounds like PCBs (polychlorinated biphenyls), and complex wastes like coal tar and creosote. Commercial operations such as dry cleaners, manufactured gas plants, and electrical-components manufacturers were or are major sources of DNAPL contamination.
Being heavier than water, released DNAPLs typically move through soil and groundwater very easily; this can make DNAPL contamination difficult to locate and remediate. The contamination usually takes two different forms: mobile contamination, that easily flows from one location to another, and residual contamination, that does not flow as a mass. For the removal of mobile DNAPL, some of the DNAPL remediation technologiesemployed include: pump & treat remediation systems, and vacuum-enhanced pump and treat remediation systems. For the removal of residual DNAPL, remediation technologies such as soil-vapour extraction, air sparging, and chemical oxidation are commonly used.
The specific DNAPL remediation technology chosen is dependent on the application, the site geology and other site conditions, and the treatment time-frame. The links on the left direct you to some of the various applications involving DNAPL contamination; on the right are links to appropriate extraction and DNAPL remediation technologies.
