A new US study casts doubts on the ability of wastewater treatment plants to deal effectively with the wastewater returned by hydraulic fracturing or fracking of shale to release natural gas or other hydrocarbons.
The study looked at wastewater from this process that had passed through three treatment plants in Pennsylvania and concluded that certain chemicals remained at concentrations above drinking water standards and other environmental health criteria (Environmental Science & Technology, doi: 10.1021/es301411q).
‘We determined that the chemicals of most public health concern included several classes,’ says Kyle Ferrar of the University of Pittsburgh, lead author of the research paper. ‘They included the volatile organic compounds benzene, toluene, ethylbenzene, xylene, and naphthalene, the elements barium and strontium, the anion bromide, and naturally occurring radioactive materials such as radium.’ He added that chloride also present in some of the wastewaters may be a concern for fish health. However, the chemical composition varied depending on the wastewater plant.
‘The levels reported exceed the MCL (maximum contaminant level) by up to 13-fold for barium, 500-fold for strontium, 500-fold for chloride and two-fold for sulphate, as well as 500-fold for total dissolved solids,’ comments Trevor Penning, toxicologist at the University of Pennsylvania. ‘However, these levels are in the effluent of the wastewater plants and would be diluted by the water supply into which they are discharged.’
Penning says the study measures contaminant levels in wastewater treatment plant effluents before and after a moratorium was placed on using these plants to purify wastewater from natural gas drilling in Pennsylvania in 2011. ‘The major source of drinking water in the Marcellus Shale is not from municipal water treatment plants but instead comes from privately owned wells. Since the water quality from these wells is not routinely monitored it would not be possible to determine whether water quality could be compromised by natural gas drilling,’ he explains.
Steve Everley of industry group Energy in Depth comments: ‘The industry places safety and environmental protection above all other considerations, which is why the best opponents can do is publish research with pre-determined conclusions and hope the public isn’t smart enough to read past the headlines.’ He says that those funding the research, including Heinz Endowments, have a track record of ‘smearing shale development’ or ‘making inflammatory statements about hydraulic fracturing.’
Ferrar notes that industry best practice is recycling; however, it is not clear how much of the wastewater is recycled. ‘Advanced treatment technologies include evaporation and crystallisation of salts. GE and some other companies are developing or, in some cases, have already employed mobile evaporator units. These technologies could provide the necessary treatment to meet new discharge standards,’ he says.
In May 2011, the Pennsylvania Department of Environmental Protection requested that 70 drillers cease discharging the wastewaters into surface waters through wastewater treatment plants, although compliance with the request was voluntary. In March 2012, updated permiting standards were introduced for WWTPs discharging the wastewater to surface water.