Management of Produced Water from the Oil and Gas Industry: Characterization, Treatment, Disposal and Beneficial Reuse.

Produced water represents the largest waste effluent generated in the oil and gas industry. As a wastewater volume which can carry a wide variety of pollutants (such as oil, suspended solids, chemicals, and radioactive matter), a proper management and disposal strategy is required, in order for operators to comply with environmental regulations applicable. In recent years, most of the world has begun efforts to transition into greener energy generation, which has resulted in stricter regulation in terms of waste effluents. As a necessary response, research has arisen to propose, test and assess new treatment technologies that allow operations to comply with effluent limits, especially for volumes that cannot be treated by conventional methods only, due to high salinities, water hardness, or high percentage of dissolved organics. Additionally, in order to reduce the need of disposal (traditionally through disposal wells or discharge into the ocean), several water recycling methods have been proposed, such as crop irrigation, aquifer recharge, fluid for hydraulic fracturing, among others. A review of available research on novel technologies and case evaluations showed that it is not possible to identify one management method as the most efficient neither in terms of cost, energy consumption or efficiency, because technology effectiveness and the feasibility of their implementation depends on water composition, site location and logistics associated, among many other factors; additionally, most recent methods proposed have only been proven at laboratory scale with few samples and would require real-scale pilot tests in order to further prove their feasibility. Another issue is the need for new regulation concerning water recycling, as limits in terms of pollutants present only in produced water do not exist for matters like soil pollution, livestock watering, or even for discharges into surface water, leading to higher risks to the environment and human health than disposal, as well as requiring more expensive treatment. In most cases, recycle within the oil and gas industry results more significant to reduce water scarcity than its possible use in other sectors; however, for specific operations, a recycle option may turn more cost effective even than traditional disposal. This research and discussion helped conclude that future research must focus in evaluating proposed methods in real scale experiments, find their optimal configurations, create efficient methods to characterize water composition, support the updating of environmental regulation, and correctly assess the long-term effects of treated produced water disposition and use on different sectors to allow the development of these practices as a response to more strict limits and environmental damage.