Purification Of Produced Water Research Articles

The Effect of Adding Adsorbents on Main Indicators of Produced Water Purification

Formation water is a by-product of oil and gas processing. This formation water is very different from fresh water because formation water contains harmful chemicals and other elements contained in oil or gas. To prevent formation water from contaminating the environment, it is necessary to reduce the formation water content using an adsorbent. Some of the parameters that indicate reduced mineral and chemical content that must be considered for this research are pH, TDS (total dissolved solid), SG (specific gravity), and salinity values. In this study observed changes in these parameters with the administration of adsorbents. Two types of adsorbents used are bagasse and bentonite. The parameters of pH and TDS were measured using litmus paper and TDS paper respectively. While SG and salinity were measured using a salinity hydrometer. The process of giving the adsorbent causes a decrease in these four parameters. The addition of 3 grams of bagasse caused the pH, TDS, SG, and salinity of the formation water to decrease to 7.8, 3086 ppm, 1008 and 12 ppt, respectively. While the addition of 3 grams of bentonite caused these four parameters to decrease to 7.8, 2720 ppm, 1010 and 14 ppt respectively.

Zwitterionic Antifouling Coatings for the Purification of High-Salinity Shale Gas Produced Water

Fouling refers to the undesirable attachment of organic molecules and microorganisms to submerged surfaces. It is an obstacle to the purification of shale gas produced water and is currently without an effective solution due to the highly contaminated nature of produced water. Here, we demonstrate the direct vapor application of a robust zwitterionic coating to a variety of substrates. The coating remains unprecedentedly hydrophilic, smooth, and effectively antifouling in extremely high salinity solutions (with salt concentration of 200,000 ppm). The fouling resistance is assessed rapidly and quantitatively with a molecular force spectroscopy-based method and corroborated using quartz crystal microbalance system with dissipation monitoring. Grazing angle attenuated total reflectance Fourier transform infrared is used in combination with X-ray photoelectron spectroscopy, atomic force microscope, and in situ spectroscopic ellipsometry to lend insight into the underlying mechanism for the exceptional stability and effectiveness of the zwitterionic coating under high-salinity conditions. A unique coating architecture, where the surface is concentrated with mobile zwitterionic moieties while the bulk is cross-linked to enhance coating durability, was discovered to be the origin of its stable fouling resistance under high salinity. Combined with previously reported exceptional stability in highly oxidative environments and strong fouling resistance to oil and grease, the zwitterionic surface here has the potential to enable low-cost, membrane-based techniques for the purification of produced water and to eventually balance the favorable economics and the concerning environmental impacts of the hydraulic fracturing industry.

Membrane oscillation and oil drop rejection during produced water purification

Removal of crude oil droplets from produced water has been evaluated using a Nickel membrane with a slotted pore width of 4μm and length of 400μm. The membrane was oscillated at different frequencies that resulted in variable intensity shears at the membrane surface. The influence of membrane oscillations on oil droplet rejection was investigated and reported in this work. Membrane oscillations generated a lift for the surrounding particles which led the drops to move away from the membrane surface. Measurements have shown that the intensity of the droplet lift was linearly proportional to the intensity of the applied shear. Inertial lift velocity model reported in literature was used as a starting point which was coupled with the fluid’s convection velocity. The model predicted 100% cut-off points through the membrane at various oscillation frequencies. Without the applied shear rate, the static and drag forces balanced each other, which was assumed to be the 100% cut-off point. With the applied shear rate, the inertial lift and convection velocities become equal and this point was referred to as 100% cut-off point. Overall mass of crude oil droplets in permeate flow was calculated knowing the 100% cut-off point and interfacial tension between the dispersed and continuous phases.

A humidification-dehumidification process for produced water purification

Deployment of humidification-dehumidification process for produced water purification was investigated in this study. The produced water from natural gas production has a total dissolved solid of 1.98×104 mg/L and total organic carbon of 470.2 mg/L. The water purification was carried out in a lab-constructed humidification-dehumidification unit with an effective surface area of 1.2 m2. The feed water temperature and flow rate were varied to investigate their influence on purified water quality, productivity, and water recovery. Both salt and dissolvable organics in the produced water were removed efficiently by the humidification-dehumidification process: the total dissolved solid was reduced from 1.98×104 to 76.75 mg/L while the total organic carbon declined from 470.2 to 17.83 mg/L. A built-in capillary bundle was deployed as dehumidifier for the enhancement of water productivity and heat efficiency. A water productivity of 0.31 kg/m2.h with water recovery of 20.7% was achieved at 80°C. The study suggested that both salt and dissolvable organics could be removed by a humidification-dehumidification process. The purified produced water is suitable for beneficial uses, such as agriculture irrigation and industry processing.

Purification of Produced Water by Ceramic Membranes: Material Screening, Process Design and Economics

Produced water, generated from underlying formations during the recovery of hydrocarbons, constitutes the largest waste stream associated with oil and gas production. Currently, over 90% of produced water is reinjected into the formation, either in support of enhanced oil recovery or for disposal. In arid areas, reclamation of produced water for beneficial uses such as irrigation or tower cooling may be an attractive alternative if the produced water can be purified to an adequate quality, specifically through the removal of dissolved components including inorganic compounds (salts, heavy metals, and radiochemicals) and organic compounds (fatty acid, aliphatic, and aromatics). Membranes technologies show advantages in both energy efficiency and high water quality. Due to the presence of dissolved organics, reverse osmosis with organic membranes is highly limited. Research efforts focus on developing new materials that are less prone to fouling and are easy to regenerate. Novel ceramic membranes are relatively new classes of material that show promising application in produced water purification due to their extreme stability in harsh environments and optional choices for regeneration. This paper details the results of investigations of produced water purification by microporous ceramic membranes, including metal oxide membranes, clay membranes, and zeolite membranes. Techniques for membrane fabrication, process design, and economic aspects are also discussed.

PEG-coated reverse osmosis membranes: Desalination properties and fouling resistance

This study focuses on the use of surface-coated reverse osmosis (RO) membranes to reduce membrane fouling in produced water purification. A series of crosslinked PEG-based hydrogels were synthesized using poly(ethylene glycol) diacrylate as the crosslinker and poly(ethylene glycol) acrylate, 2-hydroxyethyl acrylate, or acrylic acid as comonomers. The hydrogels were highly water permeable, with water permeabilities ranging from 10.0 to 17.8 (L μm)/(m 2 h bar). The hydrogels were applied to a commercial RO membrane (AG brackish water RO membrane from GE Water and Process Technologies). The water flux of coated membranes and a series-resistance model were used to estimate coating thickness; the coatings were approximately 2 μm thick. NaCl rejection for both uncoated and coated membranes was 99.0% or greater, and coating the membranes appeared to increase salt rejection, in contrast to predictions from the series-resistance model. Zeta potential measurements showed a small reduction in the negative charge of coated membranes relative to uncoated RO membranes. Model oil/water emulsions were used to probe membrane fouling. Emulsions were prepared with either a cationic or an anionic surfactant. Surfactant charge played a significant role in membrane fouling even in the absence of oil. A cationic surfactant, dodecyltrimethyl ammonium bromide (DTAB), caused a strong decline in water flux while an anionic surfactant, sodium dodecyl sulfate (SDS), resulted in little or no flux decline. In the presence of DTAB, the AG RO membrane water flux immediately dropped to 30% of its initial value, but in the presence of SDS, its water flux gradually decreased to 74% of its initial value after 24 h. DTAB-fouled membranes had lower salt rejection than membranes not exposed to DTAB. In contrast, SDS-fouled membranes had higher salt rejection than membranes not exposed to SDS, with rejection values increasing, in some cases, from 99.0 to 99.8% or higher. In both surfactant tests, coated membranes exhibited less flux decline than uncoated AG RO membranes. Additionally, coated membranes experienced little fouling in the presence of an oil/water emulsion prepared from DTAB and n-decane. For example, after 24 h the water flux of the AG RO membrane fell to 26% of its initial value, while the water flux of a PEGDA-coated AG RO membrane was 73% of its initial value.