Water treatment
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Shale Environmental Technology Review A weblog reviewing environmental technologies used in shale gas and oil exploration and production with special emphasis on applications in the northeastern U.S. « Back to posts
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April 25, 2012 Water treatment options near shale drilling
Those concerned about long range public health impacts from shale gas drilling have turned their attention lately to toxic byproducts caused whenever the disinfectant, chlorine, comes in contact with organic substances in drinking water, such as methane, bromides, and hydrocarbons. Brine_tanks
Brine water tanks collect residual frac water as it returns to the surface over time. EQT Corp. drilling site located near the Borough of Waynesburg in Greene Co., PA, about 60 miles southwest of Pittsburgh. Photo credit Josephine Sabillon.
For example, they worry that methane migrating from gas well leaks, and the ultra-salty bromides that are sometimes released downstream from waste water disposal plants, could produce carcinogenic trihalomethanes (THMs) in the water as they come in contact with chlorine. These disinfection byproducts, such as chloroform, may later turn up in drinking water. This issue relates both to private drinking water wells, where dissolved methane can interact with chlorine, to municipal drinking water supplies that often draw from rivers and streams with high levels of ultra-salty bromides from the upstream disposing of drilling waste water.
Alternatives to Chlorination
The chemical element, chlorine, still remains the disinfectant of choice for most drinking water in the U.S. It is especially effective in killing E. coli bacteria, and far superior to alternative disinfectants, such as bromine or iodine. Ozonation is used by several European countries, and also by a few communities in the U.S., to treat water. Disinfection with chloramine, a derivative of ammonia with chlorine in it, has also been gaining ground, particularly in areas where there is heavy contamination with organic matter, such as hydrocarbons. It has the advantage of being less potent than chlorine at forming byproducts such as THMs that can have damaging long range health effects, yet it still retains its effectiveness against pathogens. Filtration is still another very effective method of removing pathogens, although the finished water must be used immediately, and never stored, since the the residual pathogens left after filtration can regrow and proliferate in the water. Both chlorine and chloramine persist in treated water for an extended period of time. Finally, there is UV disinfection, which can kill bacteria, yet does not remove toxins, heavy metals, or pesticides from the water.
Holding Down THMs
It's important to recognize that most companies actively drilling in the Marcellus shale started recycling most, if not all, of their waste water in the 2010-2011 timeframe, and disposing of drilling fluids and residual waste in deep disposal wells located in Ohio. This fact alone has greatly reduced the pollutants coming from shale gas drilling in Pennsylvania. Bromides can also come from conventional gas drilling wastewater, although the amount of that wastewater is believed to be significantly less than that from shale drilling. Every drinking water system in the U.S. has some level of THMs. They naturally occur and are not merely from drilling waste water. Nevertheless, the concentration of THMs in drinking water needs to be minimized due to their carcinogenic nature.
Chloramine Is a Bandaid
It should be noted that chloromine produces roughly two thirds of the THMs that chlorine does, so it is no miricle fix for the problem--only a bandaid. Chlorine is still a superior water disinfectant because it is the most effective one. Perhaps the best all-around solution is filtration followed by chlorination. Filtration removes most, if not all, organic substances from drinking water that could react with chlorine. This prevents THMs from forming, yet achieves the benefits of disinfecting with chlorine. A combination of disinfectant methods like this, combined with an active recycing program by drillers, should eventually resolve any long-term health concerns about THMs and other drinking water contaminants.
Resources
"Expert says all Pa. oil, gas waste needs treatment", The Wall Street Journal: NY AP Top News, New York, NY, April 15, 2012, Accessed 04-26-2012.
Sharpe, Shirlie, "What is the Difference Between Chlorine and Chloramine?", About.com Freshwater Aquariums, Accessed 04-26-2012.
States, Stanley, et. al., "Bromide In the Allegheny River and THMs In Pittsburgh Drinking Water: A Link With Marcellus Shal Drilling" (PDF), American Water Works Association -- Water Quality Technology Conference, Phoenix, AZ, November 13-17, 2011, Accessed 04-26-2012.
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