March 2013, Vol. 25, No.3
High-salinity aquifers provide pathway for fracking pollution
Duke University (Durham, N.C.) researchers have found that hydraulic fracturing, or “fracking,” may not create fissures but that gas leaking from well casings could exploit them, according to a university news release.
After studying well water in northeastern Pennsylvania, the researchers found that naturally occurring pathways could allow salts and gases from the 124,000-km2 Marcellus Shale formation, which extends between New York and West Virginia, to migrate into shallow drinking water aquifers. The Marcellus Shale formation contains water naturally enriched with salts, metals, and radioactive elements.
The research team evaluated 426 drinking water samples from three groundwater aquifers in the six counties overlying the Marcellus Shale formation. The samples from the of Lock Haven, Alluvium, and Catskill aquifers showed elevated levels of salinity and geochemistry similar to deep Marcellus brine but no direct links between this and shale-gas exploration in the region, the news release says.
However, while it is unlikely that fracking caused elevated salinity, the research showed that natural pathways exist in some locations that allow gases and Marcellus brine to migrate into groundwater aquifers from deeper underground shale-gas deposits. For example, valleys in the region are more at risk for elevated salinity, which also is associated with contamination from such metals as barium and strontium.
Since drinking water supplies with greater risk for contamination can be identified by testing for elevated salinity, the researchers recommended evaluating water quality baselines as risk assessment of water contamination in shale-gas exploration areas.
The research team included professor Avner Vengosh, doctoral student Adrian Down, postdoctoral researcher Kaiguang Zhao, research scientist Thomas H. Darrah, bachelor’s degree graduate Alissa Whitet, and former Duke postdoctoral researcher Stephen G. Osborn.
The research, published in the Proceedings of the National Academy of Sciences, was funded by Duke’s Nicholas School of the Environment.
Disposing of fracking wastewater poses risk of contamination
Disposing of contaminated wastewater from hydraulic fracturing, or “fracking,” wells in the Marcellus Shale region poses risk of contamination for waterways, according to a Stony Brook (N.Y.) University news release. The Marcellus Shale region spans approximately 124,000 km2 between New York and West Virginia.
University researchers studied several fracking pollution pathways. These include wastewater disposal, truck spills while transporting fluids used in the drilling process, failure of well casing that leaks fluids into groundwater, travel of fluids through underground fractures into drinking water, surface-area drilling-site spills from improper fluids handling, and leaks from storage tanks and retention ponds, the news release says.
Professor Sheldon Reaven and doctoral student Daniel Rozell determined that an individual fracking well releases at least 200 m3 of contaminated fluids. Disposing of fracking fluids through industrial water resource recovery facilities can lead to elevated pollution levels in rivers and streams, because these facilities are not designed to handle high concentrations of salts or radioactivity 2 to 3 orders of magnitude in excess of federal drinking water standards, the news release says.
The researchers used probability bounds analysis to determine best- and worst-case scenarios that risk managers can use to make decisions and to assess whether the amount of knowledge in hand is appropriate to make a decision. The researchers concluded that the salts and radioactive materials in the wastewater pose a greater risk than other pollution and identified regulations to reduce the potential for contamination of drinking water, the news release says.
The researchers suggested that regulators explore the option of mandating alternative fracturing methods to reduce wastewater use and contamination from shale-gas extraction. These methods include nitrogen-based or liquefied petroleum gas fracturing methods that would reduce the amount of wastewater generated. Researchers also recommended that future research focus on wastewater disposal and the efficacy of contaminant removal by water resource recovery facilities, the news release says.
The study, “Water Pollution Risk Associated with Natural Gas Extraction from the Marcellus Shale” was published in the August 2012 issue of Risk Analysis.
January WER analyzes evolution of the Metropolitan Syracuse (N.Y.) Wastewater Treatment Plant
An article in the January issue of Water Environment Research (WER) presents a case study of an ongoing rehabilitation program to reduce the effects of domestic wastewater discharged from a water resource recovery facility in Syracuse, N.Y.
The Metropolitan Syracuse Wastewater Treatment Plant (Metro) discharges to Onondaga Lake in New York state. The study reviews and analyzes the evolution of treatment, point of discharge considerations, and constituent loadings from the 1970s to 2010. Researchers analyzed the water quality effects on the lake, focusing on issues related to phosphorus, nitrogen, and dissolved oxygen, the article says.
Metro’s discharge accounts for approximately 25% of the lake’s total inflow — a greater amount of wastewater effluent than any other lake in the U.S., the article says.
During earlier years of monitoring, the facility’s discharges contained large loads of nitrogen and phosphorus, which impaired water quality, the article says. During this time, the water discharged violated standards protecting against toxic effects of ammonia and nitrite, violated water clarity standards for safe swimming, exceeded limits for the summer average concentration of total phosphorus in upper waters, and violated the oxygen standard during fall turnover, the article says.
But recent years have shown “dramatic” improvements in the lake’s water quality because of advanced treatment technologies implemented at the facility. These technologies have eliminated all of the exceedances in receiving-water limits in the lake except for the phosphorus limit, the article says.
“The lake has been highly responsive to recent rehabilitation efforts mediated through reductions in Metro effluent concentrations, guided by the TMDL [total maximum daily load] process, which has resulted in significant improvements in water quality,” the article says.
The article, “Retrospective Analyses of Inputs of Municipal Wastewater Effluent and Coupled Impacts on an Urban Lake,” is available as an open-access document and can be downloaded free at http://goo.gl/weHpv.
Water Environment Research allows open access to one article per issue on a range of important technical issues such as nutrient removal, stormwater, and biosolids recycling.