A majority of the compounds that are a result of contaminated sites and leaking underground storage tanks are chemicals that are considered volatile organic chemicals (VOCs) . Chemicals are called volatile because they rapidly vaporize when they come into contact with air. Many of these items, although they are not highly soluble , still may be transported from a site by water with little effort if they are not stored properly and come into contact with the groundwater. These chemicals typically are generated from petroleum and gasoline products, plastics, paints, solvents, degreasers and other types of industrial chemicals .
Volatile chemicals also may come from the components of a home’s distribution system when conditions are aggressive. Sources may include leaching of the plastic piping used in plumbing or from adhesives used in the original construction of the system. In the disinfection process utilized by the municipalities, compounds called trihalomethanes are generated when chlorination agents come into contact with naturally occurring organic materials in the source water.
What do results mean? Are they regulated?
The EPA has established Maximum Contamination Levels (MCLs) or safety levels for approximately 25 VOCs and requires that municipalities on a regular basis also test for other unregulated VOCs. (The MCL is the maximum allowable level for a contaminant in drinking water.)
How do you test for VOC?
The EPA has established many different methods of analysis for volatilizes in drinking water and wastewater. The methods primarily used for analysis of drinking water and those that will be discussed are known as WPS Method 502.2 and EPA Method 524.2. Generally speaking, 502.2 is performed by the use of gas chromatography and 524.2 is performed using gas chromatography in combination with mass spectrometry. 524.2 is the more advanced and preferred method because of its ability to determine a greater scope of compounds that may be identified. 502.2 does not allow for the differentiation between the ions in the compound .
Until recently, many states allowed for the use of either method in the analysis of VO Cs. However, many now require that they may be run according to 524.2. All compounds that are required can be detected using the 524.2 method. Another advantage to this method is the ability to identify “unidentified compounds ” that are detected in the scan. In the process of the test, different “peaks” are generated based upon the unique mass spectra of each analyte. The location of where the peak is produced can help determine what the compound is with assuredness that is simply not available by other techniques.
Water Treatment Options
There are two main methods of removing VOCs from water: carbon filtration and aeration. The carbon absorbs many volatile organics the amount or ease of which can depend on the chemical structure. The carbon can eventually become filled with VOC and if the filter is not changed it will start adding the VOCs back into the water. Aeration is another way of removing VOC, by injecting air, which helps the VOCs volatilize into the air and can be vented .