Unconventional oil and gas exploration and development has transformed the U.S. energy industry but questions remain over the environmental impact of shale drilling. Among many people's concerns is the proper treatment and disposal of wastewater in the industry.

On Friday, the Center for Sustainable Shale Development (CSSD) expanded its wastewater treatment standard to address the treatment of shale wastewater at permitted facilities.

The organization, a collaboration of environmental groups and energy companies in the Appalachian region, said that the expanded standard represents the culmination of a year-long effort by a working group of stakeholders from industry and NGOs to address the conditions necessary for safe surface discharge of treated shale wastewater.

CSSD's original performance standard identified recycling and underground injection as acceptable methods of managing produced water. However, it also recognized that there was a need to evaluate methods of wastewater treatment and discharge.

According to the organization, in evaluating water management options, the working group took into account risks associated with long-distance trucking, as well as the fact that outlets for recycling become more limited as operations mature and begin to produce more water than can be recycled.

After examining current federal and state regulations, guidance issued by the U.S. Environmental Protection Agency and the technologies available for treating produced water, the working group determined that discharge through regulated centralized waste treatment (CWT) facilities would be the most appropriate expansion of wastewater disposal options.

CSSD pointed out that some wastewater treatment facilities are now capable of treating shale wastewater to levels at or better than receiving stream standards, making them an acceptable alternative to zero discharge.

Looking specifically at the water treatment technologies currently in use, CSSD determined that the best available treatment process involves a combination of distillation and biological treatment and, as necessary, reverse osmosis.

However, the expanded standard allows operators to use CWT facilities that utilize other technologies on the condition that they can achieve equivalent or superior treatment.

"This expansion is ambitious in that it marks the first CSSD performance standard that goes beyond producer-controlled operations," commented Susan LeGros, president of CSSD.

"Our standards to date have focused on activities at an operator's site; this expanded standard addresses what happens to an operator's wastewater when it leaves the site and goes to a treatment facility. By requiring operators to incorporate rigorous due diligence and ongoing monitoring in choosing the facilities they use, we are helping to raise the performance bar across the industry."