A Study of Tainted Drinking Water

A Study of Tainted Drinking Water A study of tainted drinking water looked at several cases in Pennsylvania and Texas. The study examined watering wells found contaminated by methane and other hydrocarbon gases. Researchers detected methane gas in excess of 130 Pennsylvania and Texas water wells. At first it was believed that the contamination was caused by fracking in near areas. Shale-gas producing companies use the process of fracking to extract natural gas from deep shale rock layers. The process of fracking is simply drilling deep vertical wells that then extend horizontally into different directions. Once the wells are extended, at high pressures water and other chemicals are pumped through creating fissures and releasing the natural gas trapped in the sediments, which is then collected. After further examination, researchers found no evidence that fracking itself was the cause of water contamination. Instead, it was established that water contamination was due to faulty wells. The steel tubing and cement seal used to line the wells was responsible for methane leaks. To further expand on methane water well contamination we must looks at what is methane gas and how it is introduced to water wells. Methane gas is odorless, colorless, tasteless, and highly combustible at levels low as five percent. There are different occurrences of methane entering water wells, through natural conditions and through human activities. Human activities may include gas well drilling, pipeline leaks, and other forms of mining. Independently Methane gas alone is not toxic and does not cause health problems when ingested through food and drinking water, and that is due to methane quickly evaporating. At higher concentrations methane emissions from water can cause an explosion in poorly ventilated or enclosed areas. There have been reports in Pennsylvania where homes and wells have exploded due to methane accumulation. According to research conducted in Pennsylvania of 60 wells, it was discovered that methane concentrations in 85% of drinking water wells (51/60 wells) across the region. It was found that regardless of industrial gas operations, concentrations of methane were significantly higher closer to natural gas wells. Concentrations were found to be seventeen times higher on average in shallow wells from operational drilling and extraction areas than in wells from nonoperational areas. The recommended average methane concentrations for action to be taken is (10-28 mg/L) by the US Office of the interior. In shallow groundwater in operational drilling areas, methane concentrations were found to be extremely high at a level of (64 mg/L). Continual research has determined that methane contamination is due to methane migration. Figure 2 and Figure 3 show different sources of methane migration. Methane migration is movement of methane from bedrocks and areas of high pressure to areas of lower pressure. Wells provide that opportunity and through leaks methane passes into the aquifers allowing passage to drinking wells. Common means for migration into shallow drinking water aquifers that can provide a possible explanation for increased methane concentrations. Firstly means of contamination is through physical displacement of gas rich liquids through underground water passages, which can aid in methane migration. Secondly, leaky gas well casing. Methane leaks can occur at very deep levels underground, with methane passing horizontally and vertically through fracture systems, any cracks in the casing can lead to contamination of near by cites, such as aquifers leading to drinking water contamination. Another means of contam ination is due to process of hydraulic fracturing, which can produce new fractures or expand existing fractures above shale formation. The resulting reduced pressure can release methane in liquids, allowing methane gas to possibly migrate upward through the fracture system. Figure 1, shows Methane concentrations as a function of distance to the nearest gas well from active and non-active drilling cites. Methods of methane water well remediation include well vents and aeration. Methane enters below and above water levels. Methane is lighter than air, consequently rising and accumulating at the top of the borehole underneath the well cap. The addition of a vent tube to the well caps can help discharge methane from water wells and decrease the concentration of dissolved methane entering homes. Methane gas entering the wells from below the water level, can remain dissolved in the water, however the concentration of the methane in water is dependent on both temperature and pressure of the water. As groundwater is pumped, temperature increase and pressure is reduced, allowing methane gas to be released through ventilation. Miniscule amounts of methane can possibly remain in the water once the water reaches surface pressure and temperatures increase above 58 degrees. Aeration, also known as air stripping, can remove methane from well water. Some aeration devices can also remove other volatile organic chemicals and gases such as radon and hydrogen sulfide. Aeration devices come in a variety of units, such as simple units with spray aerators enclosed in a tank, to stacked tower aerators, that are designed to collect and release the accumulated gasses. Once the source of methane as been determined steps towards alleviating the problem can be taken. Leaking pipelines can be fixed and improved; gas wells can be properly maintained and properly sealed. Water wells can be ventilated or other methods of engineering can be used to reduce the amount of methane in the water. Since in this case it’s the leaky wells that are causing methane leaks into its surroundings, proper cementing and casing with imperative use of centralizers to center the casing should be the action taken. Figure 4 shows the importance of centralizers. Perhaps thicker and stronger reinforced steel casing surrounded by cement should further action taken to reinsure a reduced risk of methane leaks. Figure 5 and 6 show the result of migration of methane due to cracks in steel and cement casings. 2) The control volume for the contamination presented would be the seven cases in Pennsylvania and one in Texas. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 References Boyer, E., B.R. Swistock, J. Clark, D. Rizzo, M. Madden. 2012. Impact of Marcellus Gas Drilling on Rural Drinking Water Supplies, Final report to the Center for Rural Pennsylvania, 26 pp. Fountain, H. (2014, September 15). Well Leaks, Not Fracking, Are Linked to Fouled Water. The New York Times, p. A17. Retrieved from http://www.nytimes.com/2014/09/16/science/study-points-to-well-leaks-not-fracking-for-water-contamination.html?_r=2 Oram, B. (2011, January 1). Methane and Other Gases in Drinking Water and Groundwater. Osborn SG, Vengosh A, Warner NR, Jackson RB (2011) Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. Proc Natl Acad Sci USA 108:8172–8176. Penn State, College of Agricultural Sciences, Cooperative Extension, School of Forest Resources, Water Facts #24, Methane Gas and Its Removal from Wells in Pennsylvania. University Park, PA. Prudhomme, A. (2013). Hydrofracking : What Everyone Needs to Know (p. 208). Oxford University Press. Thomas H. Darrah, Avner Vengosh, Robert B. Jackson, Nathaniel R. Warner, and Robert J. Poreda Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales PNAS 2014 111 (39) 14076-14081; published ahead of print September 15, 2014, doi:10.1073/pnas.1322107111 Article http://www.nytimes.com/2014/09/16/science/study-points-to-well-leaks-not-fracking-for-water-contamination.html?_r=1 Similar articles http://stateimpact.npr.org/pennsylvania/tag/methane-migration/ http://www.newscientist.com/article/dn26221-leaky-wells-not-fracking-polluted-us-drinking-water.html#.VC4iyuceWdx http://extension.psu.edu/natural-resources/water/drinking-water/water-testing/pollutants/methane-gas-and-its-removal-from-wells-in-pennsylvania http://www.pnas.org/content/108/43/E871.full http://www.pnas.org/content/108/20/8172.full