Wastewater ("produced water", or "brine") from the operation of natural gas wells is currently being applied to roads for dust and ice control. Use on roads turns the waste product into a resource, substituting for commercial salt or salt solutions.
Chris Guerrero's summer 2011 research, assisted by Chautauqua County's Department of Public Facilities, began to examine the environmental fate of natural gas brine constituents. Brine or "produced water" originates in the rock, as opposed to fracturing fluid which is introduced from the surface. Brine can be several times saltier than sea water. Its chemistry will reflect the rock, which will mean that if the rock is rich in certain elements or compounds the brine will also be enriched. Brine from rocks now tapped for natural gas in the Chautauqua area does not appear to be enriched in elements that are of great ecological or human health concern. Of course, its great saltiness (chloride, sodium, calcium) can harm freshwater organisms and terrestrial plants if there is a large spill. In other areas of the northern US, conventional road salt spreading enriches the nearby ground water with chloride and sodium which makes it less potable. There is a deliberate tradeoff - we consciously accept salt spreading because it reduces road accidents. Do we consciously accept spreading of natural gas brine for the same reason - road safety - and because it is cheaper to the road maintainer than conventional salt? Do we know enough about the side effects of brine to make an intelligent tradeoff?
The work determined that barium and other metals enrichment of the brine is reflected in metals enrichment of fine sediments in the roadside ditches. We would expect this to continue downhill as enrichment of sediment in nearby streams and ponds. When Marcellus shale brine is spread or spilled on roads we expect to see more serious metals impacts because of the different rock chemistry that brings higher concentrations of heavy metals, sometimes even radioactive isotopes of radium. We will be watching closely for opportunities to sample along roads where Marcellus shale brine has been spread or spilled.
This work also made us wonder how well brine is characterized in New York, particularly trace toxic metals like lead. It is difficult to detect a trace metal like lead at under ten parts per million in liquid that has tens of thousands of parts per million of other cations like sodium and calcium. The typical analytical response to the high sodium and calcium is to dilute by 100 times or more, which dilutes lead far below an economical threshold of detection. Thus it is reported as not-detected. Brine test results to regulators that we found did not include dilution factors, thus it is impossible to tell if the lead was present and diluted to below range, or simply very low in original concentration. Our follow-up will be to change our own analytical techniques from the standard ICP-AES to different methods, possibly extracting the lead and other trace metals from the brine before analysis, which leaves behind the lighter, high-concentration metals where they can no longer interfere.
Chris Guerrero or Steve Pacenka about this material.
Last updated 2011 05 24