Produced Water Filtration with Flat-Sheet Ultrafiltration Membrane

Produced Water Filtration Treatment with Flat-Sheet Ultrafiltration Membrane Akolade Okunola * 1 , Hongbo Du 1 , Raghava R. Kommalapati 1,2 1 Center for Energy & Environmental Sustainability (CEES) 2 Department of Civil and Environmental Engineering Prairie View A&M University, Prairie View, TX 77429

Abstract

Oil and gas extraction generates high volumes ofwastewater from fracturing and drilling. The Wastewater known as produced water (PW) contains bothorganicandinorganiccontaminants.Duetostrict environmental regulations, it is important to treat PW before discharge to the environment or reuse. The goal of this current research is to improve the treatment process for PW using ultrafiltration which isareliable processwithhighoilandsuspended solidsremovalrate.Suspended particles and residual oil presentin PWare removedwith caustic soda softening,CO 2 neutralization,and microfiltration.Then,PW is filtered usingaflat-sheetUltrafiltration membrane withafrequencydriveforflowcontrol.Themembranehas amolecular weight cutoff of100Da.TheUFsystemincludesaCF042 testcell,astainless-steel conical feed tank,afeedflowpump, acell platform containingsystemcontrols tubing, achiller, adigital balance ,andacomputertorecorddata.PW beforeandafterultrafiltration is characterizedbyChemical OxygenDemand(COD).

Objectives

Investigate the literature and identify ultrafiltration applications in PW treatment; Characterize the organic matter content of PW using chemical oxygen demand (COD); Determine the effectiveness of ultrafiltration to treat PW.

Methodology

Determine COD of produced using HACH digestion colorimetric determination method 8000,with HACH DRB 200 reactor, and DR 3900 Spectrophotometer Instrument; Add distilled water to 2mL of PW sample A and B, stir; Use pipette to draw 2mL of diluted PW into each COD reagent Vials(A,B,C,D) for digestion; Preheat the reactor to 150 o C, stir and clean the outside of the vials; Insert vials into the cell of the reactor and close the lid; After two hours , allow the vials to cool down for 20 minutes, stir and clean; Safely take the reading using DR 3900 Spectrophotometer.

Table 1. Chemical Oxygen Demand of PW samples

Readings

COD (PW after dilution) (mg/L) COD (PW) (mg/L)

Vial A Vial B Vial C Vial D Blanks

448 542 461 432 0

2240 2710 2305 2160 0

Introduction

Produced water, by-product of shale oil & gas industry, contains high concentrations of salts, oil residues, fracking fluids and other chemicals; PW has very high hardness (more than 5000 mg/L commonly); According to American petroleum institute 206 million tons of PW was associated with a total crude oil production of 115.9 million tons; 1 PW from oil and gas wells represents, by some estimates, the single largest source of waste generated in the United States; 2 Ultrafiltration is a separation process using membranes with pore sizes in the range of 0.1 to 0.001 micron; Ultrafiltration is used for removal of high molecular-weight substances, colloidal materials, and organic and inorganic polymeric molecules.

Figure 1. Ultrafiltration in produced water treatment. 3

Figure 2. Illusion of COD Test and Measurement Figure 4. Produced water COD test vials color change.

COD is one of very useful tools to measure PW characteristics;  The literature shows that ultrafiltration can serve as an excellent process to pretreat shale oil & gas produced water. 4

Figure 3. Color change after digestion Results and Discussion

The COD for PW sample was measured and it proved to be useful tool; The reagent chromate was reduced in proportion to the rate of organic water pollutant digestion; The sample color change from a light-yellowish brown to a darker rust brown; The chromate was reduced and the organic matter in the PW were oxidized.

1.

2.

3.

4.

References

United Kingdom Department of Trade and Industry, The Energy Report Oil and Gas Resources of the United Kingdom, 1997; 2. Allen, D. T., & Rosselot, K. S. (1994). Pollution prevention at the macro scale: flows of wastes, industrial ecology and life cycle analyses. Waste Management, 14(3-4), 317-328. Shang, W., Tiraferri, A., He, Q., Li, N., Chang, H., Liu, C., & Liu, B. (2019). Reuse of shale gas flowbackand produced water: Effects of coagulation and adsorption on ultrafiltration, reverse osmosis combined process. Science of The Total Environment, 689, 47-56. Chang, H., Li, T., Liu, B., Vidic, R. D., Elimelech, M., & Crittenden, J. C. (2019). Potential and implemented membrane-based technologies for the treatment and reuse of flowbackand produced water from shale gas and oil plays: A review. Desalination, 455, 34-57.

Acknowledgements

R&I’s Office of Undergraduate Research (OUR) and Center for Energy and Environmental Sustainability (CEES), Prairie View A&M University.

This work is supported by the National Science Foundation (NSF) through the Center for Energy and Environmental Sustainability (CEES), an NSF CREST Center, Award #1036593.

Introduction

Produced water is the most significant volume byproduct stream associated with oil and gas exploration and production. PW contains organic and inorganic materials, including salts and oil hydrocarbons. Recently, the EPA stipulates that any reuse of produced water outside of an oil field is subject to federal environmental laws and regulations, which means oil and gas industries are not permitted to discharge PW without treatment. Chemical oxygen digestion (COD) test is conducted to determine the concentration of a pollutant in the PW sample.

Part I: Lab Experiments Materials and Methods

Two types of PW was obtained from a Permian shale oil producer. The COD concentration was determined after the pollutant digestion process. In this study, the COD measurement used the HACH digestion colorimetric determination method 8000, a HACH DRB 20 reactor, and a HACH DR3900 Spectrophotometer with the COD measurement range of (200-1500mL). One of the tests COD concentration reading was higher (1753mg/L) than allowable range, 8mL of distilled water was added to the PW sample, and 2 mL of diluted PW was added to each COD vials. The PW was diluted five times; first, the test vials were kept in the digester at 150 ºC for 2 h, and the COD values were read out using the spectrophotometer.

Results and Discussion

As described in Table 1, the data collected shows that the COD reading shows that the sample solutions had to be diluted five times to mitigate error due to the much higher concentration of COD in PW. Samples’ color changed to yellow, indicating the chromate reagent reduction in proportion to the oxygen digestion rate of organic pollutants in the PW.

Table 1

PW1 Sample after dilution PW2 Sample after dilution PW1*5 PW2*5

COD Vials 1 2 COD 800 (mg/L) COD Vials COD 800(mg/L) COD mg/L COD mg/L

448

542 1

2 461

432 2240

2710 2305

2160

Summary

The PW samples were collected from Permian Shale oil. The chemical compositions of the wastewater were investigated, and the measurement results showed that the COD levels of the PW are high.

Part II: A Literature Review

A broad-based literature review was conducted on produced water treatment by membrane technology concerning membrane selection, the effectiveness of the method, and membrane performance optimization. The abstracts of more than 15 published papers were reviewed with approximately six selected for review. The experimental and modeling paper investigated the effect of transmembrane pressure on permeation flux of UF membranes for the treatment of produced water, using several polymeric membranes (PAN, PES, PS, PES, PVDF, PPand PA). The results of their experiment show that the oil retentions of all the membranes were over 99% [1]. The Desalination paper investigated a phase inversion method of preparing PVDF by dispersing lithium chloride monohydrate (LiCl-H2O) and titanium dioxide (TiO2) nanoparticles in the spinning dope, to investigate the effect of pore-forming hydrophilic additives on the porous (PVDF) ultrafiltration (UF) membrane and transport properties for PW treatment. The results of the experiment indicated that the PVDF/LiCl/TiO2 membranes with lower TiO2 nanoparticle loading possessed a smaller mean pore size. The maximum flux and rejection PW using the PVDF ultrafiltration membrane achieved was 82.50 L/m2 h and 98.83%, respectively, at 1.95 wt.% TiO2 concentration means TiO2 in PVDF UF promotes higher hydrophilicity, small pore size and high porosity [2]. PW has distinctive characteristics due to its organic and inorganic compounds. However, these characteristics change from well to well. The treatment process investigated in all the published papers evaluated, considered separation capability, pre-treatment processes, permeate flux rate, oil removal rate, and membrane material performance. In one of the papers, different ceramic membranes were employed to improve the efficiency of oil-field PW treatment. The result shows that the average permeate flux, the total oil removal rate, and the total organic carbon removal rate varied among the different membranes used.

References

1. Badrnezhad, R., & Beni, A. H. (2013). Ultrafiltration membrane process for produced water treatment: experimental and modeling. Journal of Water Reuse and Desalination, 3(3), 249-259. 2. Yuliwati, E., & Ismail, A. F. (2011). Effect of additives concentration on the surface properties and performance of PVDF ultrafiltration membranes for refinery produced wastewater treatment. Desalination, 273(1), 226-234.

Akolade Okunlola is a senior, majoring in Chemical Engineering with a minor in Military Science. Dr. Raghava Kommalapati is a Professor of Civil and Environmental Engineering with research interests in air quality measurement and modeling, energy sustainability, life cycle assessment, and shale oil & gas produced water treatment.