Directional drilling and hydraulic-fracturing technologies are dramatically increasing natural-gas extraction across the United States. Hydraulic fracturing remains largely unregulated at the Federal level regardless of the growing concerns about contamination of drinking water. However, the potential contamination risks in shallow drinking-water systems are still not fully understood, and a topic of study for many scientists. There are four main reasons why scientists and public health officials are concerned about methane contamination in the ground water: that the chemicals use in fracturing fluid can leak into the ground water, that the water can become explosive if methane levels are high enough, that the methane could be released into the environment, and that the untested and unregulated shallow ground water in rural areas near drilling sites could be ingested during household or agricultural use. Scientists have continued to study whether water wells are being contaminated in any of these ways by hydraulic fracturing and drilling. Continue reading →
Shale gas development can affect surface water quality by means of runoff from well construction and discharge from wastewater treatment facilities. Olmstead et al. (2013) conducted a large-scale statistical study of the extent to which these two activities affect surface water quality downstream. This study is different than most current literature related to the regional water impacts of shale gas development in that it focuses on impacts to surface water bodies as opposed to groundwater bodies. Researchers consulted online databases to retrieve locations of shale gas wells and wastewater treatment facilities within Pennsylvania. These were spatially related to downstream water quality monitors using Geographic Information Systems (GIS). Concentrations of chloride (Cl–) and total suspended solids (TSS) were used as indicators of water quality because both are associated with shale gas development and are measured by water quality monitors. Shale gas wastewater typically has a high concentration of Cl–, which can directly damage aquatic ecosystems and is not easily removed once dissolved in water. TSS, which harm water quality by increasing temperature and reducing clarity, can potentially come from the construction of well pads, pipelines, and roads associated with well drilling, especially when precipitation creates sediment runoff. Results of the study suggest that wastewater treatment facilities are responsible for raised concentrations of Cl– downstream and that the presence of gas wells are correlated with raised concentrations of TSS downstream. Continue reading →
Since 2008, the Marcellus shale formation has become the most productive region for extracting shale gas in the US. Managing wastewater for these operations is a challenge not only due to their size and distribution, but also because of the different types of contaminants that are present in various types of wastewater. Rahm et al. (2013) retrieved data from the Pennsylvania Department of Environmental Protection (PADEP) Oil and Gas Reporting website from 2008 to 2011 to look for the trends and drivers of Marcellus shale wastewater management. After analysis using internet resources and Geographic Information Systems (GIS), the authors found that there was a statewide shift towards wastewater reuse and injection disposal treatment methods and away from publicly owned treatment works (POTW) use. These wastewater management trends are likely due to new regulations and policies, media and public scrutiny, and natural gas prices. Research also shows that Marcellus shale development has influenced conventional gas wastewater practices and led to more efficient wastewater transportation. Continue reading →
Seems like a good idea. Yael Rebecca Glazer just suggested it in a Masters Thesis in Engineering at the University of Texas at Austin. A major issue with fracking is that sometimes a lot of the fracking fluid that was pumped down the well to create the fractures comes back up, sometimes along with additional “produced” water, sometimes twice as much as was pumped down in the first place. On top of that, it is often so contaminated that it exceeds the capabilities of industrial treatment facilities, so it gets trucked to a nearby injection well and is reinserted. But injection wells are not always handy, and anyway, the water itself would be valuable if it weren’t so polluted. Meanwhile, although a fracked well might producing mainly oil, there is also often a fair amount of natural gas produced; but if there isn’t enough gas to make it economical to capture it and sell it, it is commonly flared—burned right there at the wellhead. This converts the natural gas to CO2 without using the energy released for anything at all. Maybe, thought Ms. Glazer, that free energy could be used onsite to power wastewater cleanup technologies that normally wouldn’t be considered because of their high energy costs. It also occurred to her that since lots of these wells are in the sunny, windy southwestern US, local photovoltaic panels or wind turbines might supply energy as well. This latter option is attractive when there are no convenient transmission lines to take the power offsite, even though solar or wind energy is abundant. Continue reading →
The paper by Xie et al. (discussed in my August 10 post) didn’t say much about the electrogenic bacteria needed to make their microbial battery work. Just a few days ago, however, researchers in Beijing and Singapore published a paper focussed on such bacteria (Klebsiella sp. in this case) isolated out of a microbial fuel cell, that can do the job in wastewater heavily contaminated with cyanide, almost completely degrading the cyanide in the process. Even without the electricity generation this is interesting, because these bacteria do a better job of removing cyanide than the much more expensive chemical oxidation methods more commonly used by industry. Microbial fuel cells get electricity out of microbes differently than the “microbial battery” of Xie et al.; they consist of two wastewater-filled chambers seperated by a proton exchange membrane. The bacteria in the anode chamber strip protons (hydrogen ions) off the feedstock—a cyanide/glucose mixture in this experiment—and the protons migrate through the membrane to the cathode. The electrons flow as an electrical current from the anode to the cathode in a wire, where they can be used as electricity. Interestingly, the bacteria continued to generate electricity from cyanide alone when they ran out of glucose.
Wang, W., Feng, Y., Tang, X., Li, H., Du, Z., Yang, Z., Du, Y., 2014. Isolation and Characterization of an Electrochemically Active and Cyanide-degrading Bacterium Isolated from a Microbial Fuel Cell. RSC Advances, DOI: 10.1039/C1034RA04090B. Abstract at: http://rsc.li/XbkskA
Bacteria are good at getting energy out of sewage; that’s what wastewater treatment plants are mostly about…converting the organic carbon that we didn’t extract from the food during it’s passage through our guts into something that won’t pollute the water bodies we dump the treated wastewater into. In the closed anaerobic digester tanks you can see at any wastewater treatment plant the microorganisms are busy converting it into methane. Sometimes this methane gets used onsite to generate power, or is further processed and piped off as “biogas” for some other use, maybe even to power city buses. More often than not it is just released into the atmosphere where, although it can no longer pollute any water, it is a powerful greenhouse gas. What if we could skip the methane production step and just generate electricity directly from the sewage by sticking electrodes in it? Sounds impossible, but there is new science that is making it happen, at least at laboratory scale. Xie et al. at Stanford University have constructed what they call a microbial battery that makes just as much electricity out of a given amount of wastewater as you can get from first using the microorganisms to produce methane, then burning it…without the intervening gas handling and power plant, not to mention the likely leaks of methane to the atmosphere in the process. The secret is a solid-state cathode which makes the system act like a rechargeable battery, with exoelectrogens—microorganisms that oxidize the electron-donating chemicals in the sewage and transfer the electrons to the anode. The electrons then pass through an external circuit as an electrical current, on their way to the cathode. Voila! Electricity that can be used for anything you like.
Xie, X., Ye, M., Hsu, P.-C., Liu, N., Criddle, C.S., Cui, Y., 2013. Microbial battery for efficient energy recovery. Proceedings of the National Academy of Sciences 110, 15925-15930. http://bit.ly/1siA7Ji