VOC’s in My Drinking Water?
VOC’s in drinking water continue to pose a problem for residents in many areas. Lockheed Martin Corp. has offered $5 million to Burbank, CA, residents whose water has been contaminated with VOC’s. In Pennsylvania, VOC’s have been found in private water supplies in various areas such as Upper Salford Township, in Montgomery County, as well as Middletown Township, Bucks County. The PA Department of Environmental Protection (DEP) in some cases provides bottles water to the homes where contaminant levels represent a health threat, as the investigation of the problem continues.
What are VOC’s?
Volatile Organic Chemicals (VOC’s) include a wide variety of chemicals. The USEPA regulates a
list of 21 VOC’s. This list includes hydrocarbons such as styrene, benzene, toluene, ethylbenzene and xylene. These chemicals are found in crude oil, gasoline, paints, paint thinners and solvents. All are flammable and are lighter than water. Other VOC’s are chemicals that contain chlorine and do not occur naturally in the environment. Common abbreviations such as TCE (trichloroethylene), PCE (perchloroethylene or tetrachloroethylene) and TCA (1,1,1 trichloroethane) are often used to describe these chemicals. These chemicals are generally not very flammable and most are heavier than water. Trichloroethylene is commonly used for removal of oily and greasy residues from metal products, and perchloroethylene is commonly used in dry cleaning operations.
VOC’s usually cannot be detected in drinking water by taste or odor, unless many times over the acceptable limit.
Are they harmful?
Cancer risk, kidney damage liver damage and nervous system damage are some of the risks associated with VOC exposure.
How do they get in the water supply?
Prior to strict environmental regulations solvents were often simply dumped out back or were hauled to remote areas by truck and were dumped on the ground. When exposed to air these solvents quickly evaporate. However, once under the surface of the ground they move rapidly through soil and into the water table. Breakdown in the soil ranges from slow to virtually no breakdown. When VOC’s encounter the water table, a portion of the chemical becomes soluble in the water with the remainder either floating on top of the water or sinking down through the water to an impermeable zone.
VOC’s have been found in nearly every type of soil and area. Individuals have cut down one hundred year old woodland, drilled wells and found chlorinated solvents that were not invented one hundred years ago. Farmlands have been developed and wells have been found to be contaminated with VOC’s. At times, responsible parties can be found and held liable for the contamination. In other instances, one can only guess at the source.
How do you test for VOC’s?
Testing for VOC’s is done using gas chromatography. Samples are collected in airtight glass containers and are transported to the laboratory. In the laboratory the sample is transferred to a glass vessel in a purge and trap apparatus. Gas is bubbled through the water and the VOC’s are purged from the water and are collected on an adsorbent trap.
The trap is then heated and the VOC’s are transferred to the gas chromatograph where they are separated and are identified by either a combination of detectors or a mass selective detector.
Ideally, a water supply should have no detectible levels of VOC’s. Unfortunately, this is often not the case. Wells that show any detectible level of VOC’s should be monitored frequently. A well that shows detectible levels of VOC’s when first tested could be showing the “tip of the iceberg” or may simply be a minor passing problem. The only way to determine this is by subsequent testing.
It is usually best to perform at least two tests for VOC’s prior to installing a treatment system.
How do you treat for VOC’s?
Treatment for VOC’s is usually accomplished by one of two methods. The first is aeration. As the name volatile organic chemicals implies, VOC’s are volatile. This means that when water containing VOC’s is exposed to air, the VOC’s tend to go from the water into the air. Packed tower aeration columns are used to strip the VOC’s from a water supply and blow them into the atmosphere. Since such systems are relatively large, require blowers, sprayers and a repressurization pump they are seldom used in a household treatment system. Aeration systems can economically treat large volumes of water and since the VOC’s are transferred into the air, there are no waste materials to dispose of. These characteristics make them desirable for municipal systems more so than home use.
The second method of removing VOC’s is by using activated carbon. A variety of filters employing activated carbon are available for treating drinking water. Be sure that the filter is clearly labeled for VOC removal. An even better way to be sure that a filter will remove VOC’s is to look for a filter that has been certified by the NSF (National Sanitation Foundation) for VOC removal. Consuming water that contains VOC’s is not the only risk. Since VOC’s are easily transferred to the air, exposure from showering may represent more of a risk than consumption. For this reason it is advantageous to remove VOC’s from all of the water in a home. This can be accomplished using a point of entry carbon filter. Point of entry filters are usually filled with GAC (Granular Activated Carbon). The GAC filter is installed where the water enters the home and usually after any water softeners, neutralizers or other filters. GAC collects and retains the VOC’s that it adsorbs from the water. Eventually the GAC adsorbs all the VOC’s it can and has to be removed from the filter and be disposed of.
A regular testing program is a necessity when GAC is being used to remove VOC’s. Since the GAC is simply storing the VOC’s for later disposal, using the filter beyond its capacity may cause previously removed VOC’s to be released back into the water, actually increasing the level of VOC’s.