In December 2016, the United States Environmental Protection Agency (U.S. EPA) published the findings of their multiyear study entitled, "Hydraulic Fracturing for Oil and Gas: Impacts from the Hydraulic Fracturing Water Cycle on Drinking Water Resources in the United States." EPA's final report (with contributing studies) totals over a thousand pages, and sparked controversy during the assessment, after the release of their draft 2015 report and the final document. This paper provides a summary of the EPA study effort and processes, and highlights key finding and limitations of the work. In 2010 Congress authorized the U.S. EPA to study the potential impact of hydraulic fracturing (HF) on water quality. EPA's office of Research and Development (ORD) drafted a study approach that included (1) defining research questions and identifying data gaps, (2) conducting a process for stakeholder input and research prioritization, (3) developing a detailed study design that would lead to external peer-review, and (4) implementation of the planned research. This study approach was reviewed by a committee formulated under the EPA's Scientific Advisory Board (SAB), and one author of this paper served on the first SAB review panel. A separate SAB committee was empaneled later to review the results of the research and draft conclusions. All three authors of this paper were appointed to the second SAB panel. Initially, industry considered the Congressional request to be a focused assessment related to the actual process of HF on drinking water. It later became clear that the interpretation by the EPA of the Congressional request was a broader evaluation on the "life cycle" of water during the drilling and completion activities for oil and gas development. The final focused study approach was based on a HF hydraulic fracturing water cycle beginning with water acquisition, chemical mixing, and injection of the treatment. After HF (the actual hydraulic fracturing treatment, also known as "completion"), the fracture water cycle includes produced water handling, HF water disposal and reuse, and identification and hazard evaluation of chemicals across the hydraulic fracturing water cycle. Each of the stages in the HF process are treated separately in the study, and includes fundamental explanations, scientific research, academic (literature) review, and stakeholder input. This paper provides a succinct summary of the EPA HF study. The summary is important for industry, government and academia as the final Assessment report is currently being cited as a basis for policy and regulatory development worldwide.

The recycling and reuse of produced water (defined as hydraulic fracturing flowback water and formation water) is an increasing practice driven by competing demands for water sources and limited options for produced water disposal. The final disposition of reused/recycled produced water dictates the level of treatment with typically minimal treatment required when produce water is reused for fracturing subsequent wells and higher levels of treatment required when produced water is recycled for other purposes or potentially discharged to surface water bodies. The latter scenario, discharge of treated produced water is specifically addressed. Clean Water Act National Pollutant Discharge Elimination System (NPDES) permits for direct discharge of oil and gas generated discharge are currently prohibited east of the 98 th meridian. West of the 98 th meridian, direct discharge of treated oil and gas wastewater is allowed under specific conditions. Regardless of location (east or west of the 98 th meridian), centralized wastewater treatment facilities (CWTs) can be permitted to treat and discharge oil and gas wastewater or CWT discharge may be accepted for further treatment and ultimate discharge at publically owned wastewater treatment facilities (POTWs). The EPA is currently developing effluent limitation guidelines (ELGs) for pretreatment of oil and gas wastewater sent to POTWs for treatment and discharge and recently submitted for comment Final 2012 and Preliminary 2014 Effluent Guidelines Program Plans; both addressed in this paper. Discussed are the various treatment technologies currently deployed and permitting issues associated with the treatment facilities. When treating produced water for discharge, constituent levels in the effluent stream and the waste side streams (consisting of a concentration of constituents removed as part of the water treatment processes) must be monitored to ensure proper management.