Evaluation of polymeric adsorbents via fixed-bed columns for emulsified oil removal from industrial wastewater

Polymeric adsorbents (PAs) have been gaining increased attention for application in industrial wastewater (WW) treatment. However, most studies on evaluating PAs specifically for emulsified oil removal are currently limited to performance screening through batch mode testing. Hence, this paper presents a thorough fixed-bed assessment of advanced PAs for the removal of emulsified oil from industrial WWs. A unique custom-built column setup was developed with a continuous test protocol that involves both adsorption and regeneration of media. A robust procedure was also established to automatically prepare a representative synthetic produced water (PW) containing the oil-water emulsions. Four cutting-edge PAs were evaluated, out of which two being tested for the first time targeting emulsified oil removal. Experimental tests were conducted to address resin capacity, regeneration efficiency, and performance reproducibility in repeat cycles. PA2 treated 168 ± 58 bed volumes (BVs) achieving the lowest capacity of 44 ± 14 mg/g. Higher comparable capacities were observed for PA1 and PA3 at ~100 mg/g, yet PA1 was found capable of treating 807 ± 3 BVs against 548 ± 115 BVs measured for PA3. PA4 treated 1219 ± 86 BVs with a capacity of 301 ± 27 mg/g which indicate its strong potential for industrial WW treatment application. This performance data can provide a reference for comparison when testing other novel resins for emulsified oil removal. Future studies will focus on testing PAs using real PW and evaluating their long-term performance via pilot testing

Pilot-scale evaluation of forward osmosis membranes for volume reduction of industrial wastewater

Water treatment is a key aspect for the sustainable management of oil & gas operations. Osmotic concentration (OC) is an advanced water treatment process, adapted from forward osmosis (FO), that does not require water recovery from the draw solution. In this study, two commercial hollow fiber FO membranes [Module 1, cellulose triacetate (CTA) and Module 2, thin film composite (TFC)] were evaluated at pilot scale using actual process water obtained from a gas production facility. The evaluation focused on assessing the membrane productivity, fouling potential and chemical cleaning efficiency while normalizing the performance using a theoretical model that account for the variability of the operating conditions. Performance tests showed that Module 2 has a higher flux compared to Module 1, 9.9 L/m2·h vs 1.7 L/m2·h; and lower specific reverse solute flux (RSF) for most of the ions. Additionally, Module 1 benchmark experiment showed a 13% flux loss attributed to inorganic fouling (calcium phosphate precipitation) while the flux loss in Module 2 was <5% possibly due to enhanced module hydrodynamics and variation in membrane chemistry. Chemical cleaning (citric acid) proved to be successful in restoring the flux for Module 1. From the 8.1 mg/L organic carbon present in the feed, advanced organic characterization revealed that certain group of hydrophilic organics are able to pass through Module 1, but not Module 2, translating to a specific forward organic solute flux of 0.9 mg/L and 0.1 mg/L for Module 1 and 2, respectively. Finally, key sustainable and environmental considerations were presented in support of further development of process implementation. The OC process has strong potential for full-scale installation; however, demonstrating its performance in the field would be the next step necessary for successful implementation of the technology

Industrial wastewater volume reduction through osmotic concentration: Membrane module selection and process modeling

Osmotic concentration (OC), a form of forward osmosis (FO) but without draw solution recovery, can be applied for reducing wastewater disposal volumes in the oil & gas industry. Within this industry, wastewater is often disposed of by injection through disposal wells into deep underground reservoirs. By reducing wastewater disposal volumes, the sustainability of the disposal reservoir is improved. In this application of OC, seawater or brine from a desalination plant serves as the draw solution and the diluted seawater is discharged to the sea. This study compared 3 commercial hollow-fiber FO membranes (CTA, TFC, aquaporin proteins) for reducing the volume of low salinity wastewater generated during liquified natural gas (LNG) production. Additionally, a model was developed to predict the performance of commercial full-scale membranes by identifying optimum operating conditions, taking into consideration the trade-off between feed concentration factor and water flux. Bench-scale tests were conducted using synthetic and actual wastewater from an LNG facility to evaluate OC technology performance and validate model predictions.Based on model results with a feed mimicking the salinity of actual wastewater, a 4x concentration factor produced a reasonable compromise between feed recovery and draw solution dilution and was considered the optimum for future tests. At higher concentration factors, the increased dilution of the draw solution negatively impacted flux. In bench tests with real wastewater, the TFC chemistry had a ≈5x higher water flux (9.7 vs. 1.9 L/m2-h) and a ≈3x lower specific reverse solute flux (192 vs. 551 mg/L) compared to the CTA chemistry. However, both membranes showed less than 5% fouling and a specific forward organic solute flux of less than 0.5 mg/L of total organic carbon (TOC). Pilot testing for >50 h showed stable performance, comparable to bench scale data and model predictions

Evaluation of pretreatment and membrane configuration for pressure-retarded osmosis application to produced water from the petroleum industry

Pressure-retarded osmosis (PRO) is a promising membrane technology for harnessing the osmotic energy of saline solutions. PRO is typically considered with seawater/river water pairings however greater energy can be recovered from hypersaline solutions including produced water (PW) from the petroleum industry. One of the major challenges facing the utilization of hypersaline PW is its high fouling propensity on membranes. In this unique experimental evaluation, real PW from different sites was pretreated to varying degrees: i) minimal, ii) intermediate, and iii) extensive. The treated effluent was subsequently used for PRO testing and fouling rates were assessed for different membrane configurations over multiple cycles. Commercial grade flat sheet (FLS) coupons and novel hollow fiber (HF) modules were compared to validate the lower fouling propensity of HF membranes in PRO application. When minimally pretreated PW (10-micron cartridge filtration (CF)) was tested in FLS mode, severe membrane fouling occurred and the PRO flux decreased by 60%. In contrast, HF modules showed <1% flux decrease under both minimal and intermediate pretreatment schemes. Extensive pretreatment (1-micron CF, dissolved air flotation (DAF), powdered activated carbon, and microfiltration) reduced FLS PRO flux decline to <1%. These results confirm that PW can be treated to suitable levels for PRO application to avoid membrane fouling. Further validation of these pretreatment methods requires long term pilot testing and techno-economic assessment

Mesoporous silica filled smart super oleophilic fibers of triblock copolymer nanocomposites for oil absorption applications

Super oleophilic fibers of styrene-isoprene-styrene (SIS) block copolymer/mesoporous silica (MS) nanocomposites are fabricated by electrospinning, and their oil absorption efficiency is monitored by following two different approaches. The first way is by using the fibers as tubular packing materials for oil absorption, whereas the second approach uses the fibers as filtration membrane after deposition on the commercial polyethersulfone (PES) support. All composites are made by adding inorganic MS in different concentrations (2, 4, and 7 wt.%) to SIS block copolymer. The addition of MS increases the fiber diameters and leads to enlarged and bead-like appearances, especially at higher filler concentrations. The oil absorption efficiency is explored based on the oil absorption capacity of the samples as well as with the gravity-driven oil filtration experiments. The best oil absorption efficiency is achieved by the 4 wt.% SIS-MS composite (150% higher oil absorption capacity compared to the neat SIS), and it is used to spin on the PES mechanical support of different pore sizes (0.2 μ and 8 μ). Ultrafiltration tests conducted on those coated membranes observe improved oil rejection performance as the fibrous SIS-MS are layered on the commercial mechanical support.Other Information Published in: Emergent Materials License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s42247-020-00111-3</p