On-site treatment capacity of membrane distillation powered by waste heat or natural gas for unconventional oil and gas wastewater in the Denver-Julesburg Basin

A review of the development in shale oil and gas wastewater desalination

The development of the shale oil and gas extraction industry has heightened concerns about shale oil and gas wastewater (SOGW). This review comprehensively summarizes, analyzes, and evaluates multiple issues in SOGW desalination. The detailed analysis of SOGW water quality and various disposal strategies with different water quality standards reveals the water quality characteristics and disposal status of SOGW, clarifying the necessity of desalination for the rational management of SOGW. Subsequently, potential and implemented technologies for SOGW desalination are reviewed, mainly including membrane-based, thermal-based, and adsorption-based desalination technologies, as well as bioelectrochemical desalination systems, and the research progress of these technologies in desalinating SOGW are highlighted. In addition, various pretreatment methods for SOGW desalination are comprehensively reviewed, and the synergistic effects on SOGW desalination that can be achieved by combining different desalination technologies are summarized. Renewable energy sources and waste heat are also discussed, which can be used to replace traditional fossil energy to drive SOGW desalination and reduce the negative impact of shale oil and gas exploitation on the environment. Moreover, real project cases for SOGW desalination are presented, and the full-scale or pilot-scale on-site treatment devices for SOGW desalination are summarized. In order to compare different desalination processes clearly, operational parameters and performance data of varying desalination processes, including feed salinity, water flux, salt removal rate, water recovery, energy consumption, and cost, are collected and analyzed, and the applicability of different desalination technologies in desalinating SOGW is qualitatively evaluated. Finally, the recovery of valuable inorganic resources in SOGW is discussed, which is a meaningful research direction for SOGW desalination. At present, the development of SOGW desalination has not reached a satisfactory level, and investing enough energy in SOGW desalination in the future is still necessary to achieve the optimal management of SOGW.

Desalinating a real hyper-saline pre-treated produced water via direct-heat vacuum membrane distillation

Membrane distillation (MD) is an emerging thermal desalination technology capable of desalinating waters of any salinity. During typical MD processes, the saline feedwater is heated and acts as the thermal energy carrier; however, temperature polarization (as well as thermal energy loss) contributes to low distillate fluxes, low single-pass water recovery and poor thermal efficiency. An alternative approach is to integrate an extra thermal energy carrier as part of the membrane and/or module assembly, which can channel externally provided heat directly to the membrane-feedwater interface and/or along the feed channel length. This direct-heat delivery has been demonstrated to increase single-pass water recovery and enhance the overall thermal efficiency. We developed a bench-scale direct-heated vacuum MD (DHVMD) process to desalinate pre-treated oil and gas "produced water" with an initial total dissolved solids of 115,500 ppm at a feed temperature ranging between 24 and 32 °C. We evaluated both water flux and specific energy consumption (SEC) as a function of water recovery. The system achieved a 50% water recovery without significant scaling, with an average flux >6 kg m^-2 hr^-1 and a SEC as low as 2,530 kJ kg^-1. The major species of mineral scales (i.e., NaCl, CaSO₄, and SrSO₄) that limited the water recovery to 68% were modeled in terms of thermodynamics and identified by scanning electron microscopy and energy-dispersive X-ray spectroscopy. In addition, we further developed and employed a physics-based process model to estimate temperature, salinity, water transport and energy flows for full-scale vacuum MD and DHVMD modules. Model results show that a direct-heat input rate of 3,600 W can increase single-pass water recovery from 2.1% to 3.1% while lowering the thermal SEC from 7,800 kJ kg^-1 to 6,517 kJ kg^-1 in an unoptimized module. Finally, the scaling up potential of DHVMD process is briefly discussed.

Waste management in the mining industry of metals ores, coal, oil and natural gas - A review

Waste generated due to mining activity poses a serious issue due to the large amounts generated, even up to 65 billion tons per year, and is often associated with the risk posed by its storage and environmental management. This work aims to review waste management in the mining industry of metals ores, coal, oil and natural gas. It includes an analysis and discussion on the possibilities for reuse of certain types of wastes generated from mining activity, and discusses the benefits, disadvantages and the impact of waste management on the environment. The article presents current methods of waste management arising during the extraction and processing of raw materials and the threats resulting from its application. Furthermore, the potential methods of mining waste management are discussed through an in-depth characterization of the properties and composition of various types of rocks. The presented work addresses not only the issues of more sustainable management of waste from the mining industry, but also responds to the current efforts to implement the assumptions of a circular economy, which is aimed at closing the loop. The methods of recycling by-products and treating waste as a resource more and more often not only meet environmental expectations, but also become a legal requirement. In this respect, the presented work can serve as a valuable support in decision-making about waste management.

Negative Pressure Membrane Distillation for Excellent Gypsum Scaling Resistance and Flux Enhancement

Membrane distillation (MD) has potential to become a competitive technology for managing hypersaline brine but not until the critical challenge of mineral scaling is addressed. The state-of-the-art approach for mitigating mineral scaling in MD involves the use of superhydrophobic membranes that are difficult to fabricate and are commercially unavailable. This study explores a novel operational strategy, namely, negative pressure direct contact membrane distillation (NP-DCMD) that can minimize mineral scaling with commercially available hydrophobic membranes and at the same time enhance the water vapor flux substantially. By applying a negative gauge pressure on the feed stream, NP-DCMD achieved prolonged resistance to CaSO₄ scaling and a dramatic vapor flux enhancement up to 62%. The exceptional scaling resistance is attributable to the formation of a concave liquid-gas under a negative pressure that changes the position of the water-air interface to hinder interfacial nucleation and crystal growth. The substantial flux enhancement is caused by the reduced molecular diffusion resistance within the pores and the enhanced heat transfer kinetics across the boundary layer in NP-DCMD. Achieving substantial performance improvement in both the scaling resistance and vapor flux with commercial membranes, NP-DCMD is a significant innovation with vast potential for practical adoption due to its simplicity and effectiveness.

Contrasting Behaviors between Gypsum and Silica Scaling in the Presence of Antiscalants during Membrane Distillation

Mineral scaling is a major constraint that limits the performance of membrane distillation (MD) for hypersaline wastewater treatment. Although the use of antiscalants is a common industrial practice to mitigate mineral scaling, the effectiveness and underlying mechanisms of antiscalants in inhibiting different mineral scaling types have not been systematically investigated. Herein, we perform a comparative investigation to elucidate the efficiencies of antiscalant candidates with varied functional groups for mitigating gypsum scaling and silica scaling in MD desalination. We show that antiscalants with Ca(II)-complexing moieties (e.g., carboxyl group) are the most effective to inhibit gypsum scaling formed via crystallization, whereas amino-enriched antiscalants possess the best performance to mitigate silica scaling created by polymerization. A set of microscopic and spectroscopic analyses reveal distinct mechanisms of antiscalants required for those two common types of scaling. The mitigating effect of antiscalants on gypsum scaling is attributed to the stabilization of scale precursors and nascent CaSO₄ nuclei, which hinders phase transformation of amorphous CaSO₄ toward crystalline gypsum. In contrast, antiscalants facilitate the polymerization of silicic acid, immobilizing active silica precursors and retarding the gelation of silica scale layer on the membrane surface. Our study, for the first time, demonstrates that antiscalants with different functionalities are required for the mitigation of gypsum scaling and silica scaling, providing mechanistic insights on the molecular design of antiscalants tailored to MD applications for the treatment of wastewaters containing different scaling types.