Oilfield Produced Water Treatment Research Articles

Recent advances on the treatment of oilfield-produced water by advanced oxidation processes: A review

ABSTRACT Despite the advancements in alternative fuels and energy sources, there continues to be a significant global dependence on oil production and extraction. A substantial volume of oilfield-produced water (OPW) is generated during the production and extraction processes of oil fields. Recurrent OPW treatments encountered significant challenges in addressing this particular type of wastewater. Advanced oxidation processes (AOPs) are regarded as a promising alternative approach for the degradation of recalcitrant organic compounds in the OPW. This review focuses on the characterization of OPW. The treatment of organic pollutants in wastewater using AOPs, such as ozonation, Fenton oxidation-based processes, heterogeneous photocatalysis, and persulfate oxidation, is comprehensively reviewed in terms of their efficiency for pollutant degradation. The primary challenges in this field and the future directions for development are proposed, with the aim of providing a valuable reference for achieving highly effective treatment of OPW.

Visible light-driven TiO2-WO3@GO photocatalyst with catalytic memory for round-the-clock photocatalytic degradation of oilfield-produced water

The inability of most photocatalysts to continue the catalytic process after the removal of light irradiation is one of their major drawbacks. In this work, a ternary nanocomposite of titanium oxide (TiO2) supported with tungsten oxide (WO3) and hybridized with graphene oxide (GO) (TiO2-WO3@GO) photocatalyst with electron energy storage properties was synthesized for oilfield-produced water (OPW) treatment under visible light and in dark conditions. WO3 addition extended the light absorption range of TiO2 into the visible light while also serving as an electron storage material for dark catalysis (memory catalysis). The GO serves as an efficient electron acceptor and transporter to prevent charge carrier recombination, thereby enhancing interfacial electron transfer within the photocatalyst system. 2.5 wt%, 5 wt%, and 10 wt% of WO3 precursors were reacted with TiO2 precursor and GO was further added to synthesize the nanocomposites via a modified sol-gel and solution-based approach for the first time. The properties of the nanocomposite were assessed using a wide range of characterization. The nanocomposite containing 5 wt% WO3 showed the best photocatalytic activity with the total organic content (TOC) degradation of 27.7% within 4 h of photodegradation in visible light, which is better than 22 % in 5 h under UV light so far reported in the literature. The nanocomposite also exhibited electron energy storage properties for dark catalysis after pre-illumination, i.e., 16.6% TOC degradation in 3 h in dark conditions. This low % TOC degradation in the dark could be attributed to the complex nature of OPW. This work has further confirmed the possibility of the use of photocatalysts for dark catalysis.

Dual layer hollow fiber photocatalytic membrane based on TiO2-WO3@GO composite with catalytic memory and enhanced anti-fouling and self-cleaning properties for oilfield-produced water treatment

Oilfield-produced water (OPW) is a complex wastewater that is difficult to treat causing significant harm to the environment. Photocatalytic membranes are emerging for OPW treatment. However, they suffer significant fouling due to the inability to self-clean during prolonged treatment. They also require continuous photo assistance to sustain the catalytic process. This limits their applications in the absence of light referred to as memory catalysis. This work reported the fabrication of a unique ternary photocatalyst TiO2-WO3@GO/PVDF dual-layer hollow fiber (DLHF) photocatalytic membranes for photodegradation and memory catalysis of total organic carbon (TOC) in OPW. The photocatalytic membranes were fabricated via phase inversion and co-extrusion method varying (0,1,3,5) wt% of the TiO2-WO3@GO photocatalyst. The membranes were characterized and their performances for TOC removal under visible light and memory catalysis were evaluated. The membranes exhibited excellent TOC degradation, rejection, anti-fouling, self-cleaning, and catalytic memory. The WO3 was responsible for electron storage within the system and improved the absorptive capacity of TiO2 in the visible range while the GO promoted the electron-hole transfer creating abundant active sites for photocatalytic reaction. The 3 wt% loaded membrane showed the best TOC rejection of 98.62 % after 6 h of operation, water and permeate fluxes of 99.51 L/m2h, and 76.54 L/m2h respectively. The membrane showed good catalytic memory in the dark with a TOC rejection of 68.56 % after 6 h, OPW flux recovery ratio (FRR), and TOC rejection of 91.35 % and 89.76 % respectively after 5 cycles of operation under visible light. This work is expected to bring a paradigm shift toward the fabrication of memory catalytic membranes for wastewater treatment.

Activated carbon fibers functionalized with superhydrophilic coated pDA/TiO2/SiO2 with photoluminescent self-cleaning properties for efficient oil-water separation

The adhesion of high-viscosity oil contamination poses limitations on three-dimensional (3D) materials' practical use in treating oilfield-produced water (OPW). In this study, we developed a hybrid pDA/TiO2/SiO2 coating (PTS) on the surface of hydrophilic activated carbon (ACF1) through a combination of dopamine (DA) polymerization, ethyl orthosilicate (TEOS) hydrolysis, and the condensation of TiO2 nanoparticles (NPs) with SiO2 NPs. This coating was designed for gravity-based oil-water separation. The inherent porosity and generous pore size of ACF1-PTS conferred it an ultra-high permeation flux (pure water flux of 3.72 × 105 L∙m−2∙h−1), allowing it to effectively separate simulated oil-water mixtures and oil-water emulsions while maintaining exceptional permeation flux and oil rejection efficiency. When compared to cleaning methods involving ethanol aqueous solutions and NaClO, ultraviolet (UV) illumination cleaning proved superior, enabling oil-contaminated ACF1-PTS to exhibit remarkable flux recovery efficiency and oil-removal capabilities during cyclic separation of actual OPW. Furthermore, the ACF1-PTS material demonstrated impressive stability and durability when exposed to acidic environments (acid, alkali, and salt), robust hydraulic washout conditions, and 25-cycle tests. This study offers valuable insights and research avenues for the development of highly efficient and environmentally friendly 3D oil-water separation materials for the actual treatment of OPW.

Preparation of super hydrophilic-underwater super oleophobic photoinduced self-cleaning Al2O3 @TiO2 ceramic membrane and separation performance of oil-in-water emulsion

Membrane hydrodynamic irreversible oil fouling is a pressing issue. Here, an antifouling Al2O3 @TiO2 membrane with excellent wettability was created using the sol-gel method to create an anatase nano-TiO2 coating on the surface of an Al2O3 ceramic membrane. Analyzing the separation performance of an Al2O3 @TiO2 membrane on simulated oily emulsions determined the amount of TiO2 covered on the membrane surface (0.8 mol·L−1). Under the synergy of hydrophilic nano-TiO2 and ultraviolet (UV) light, the Al2O3 @TiO2 membrane demonstrated improved wettability and self-cleaning ability and maintained favorable separation performance (769.23 L·m−2·h−1, 97.75%, 1.23 mg·L−1) after 6 h of continuous separation of the actual oilfield produced water. After 30 min of UV illumination, the membrane flux recovered completely. This is due to the fact that the active substances (eg.,·OH,·O2, and 1O2) generated in situ on TiO2 on the membrane surface after UV illumination weakened the interaction of membrane surface fouling, resulting in less oil fouling. In addition, the Al2O3 @TiO2 membrane maintained extremely outstanding oil resistance stability and recoverability during high-intensity hydraulic flushing and 25 cycles of testing. This study provides a theoretical basis for the engineering application of ceramic membranes in oilfield-produced water treatment.

Reviewing Advanced Treatment of Hydrocarbon-Contaminated Oilfield-Produced Water with Recovery of Lithium

The global demand for lithium, which is indispensable for electric cars and electrical devices, has increased. Lithium recovery from oilfield-produced water is necessary to meet the growing need for lithium-ion batteries, protect the environment, optimize resource utilization, and cut costs to ensure a successful energy transition. It is useful for keeping water supplies in good condition, adhering to legal requirements, and making the most of technological advances. Oil and gas companies might see an increase in revenue gained through the lithium extraction from generated water due to the recouping of energy costs. Therefore, this review focuses on contamination and treatment strategies for the oilfield-produced water. It includes a discussion of the global lithium trade, a financial analysis of lithium extraction, and a comparison of the various methods currently in use for lithium extraction. It was evaluated that economic considerations should be given priority when selecting environmentally friendly methods for lithium recovery from oilfield-produced water, and hybrid methods, such as adsorption–precipitation systems, may show promising results in this regard. Lastly, future prospects for the lithium industry were also discussed.

Novel strategy for treating high salinity oilfield produced water: Pyrite-activated peroxymonosulfate coupled with heterotrophic ammonia assimilation

Existing conventional biological treatment techniques face numerous limitations in effectively removing total petroleum hydrocarbons (TPHs) and ammonia (NH4+-N) from oilfield-produced water (OPW), highlighting the pressing need for innovative pre-oxidation and biological treatment processes. In this study, a pyrite-activated peroxymonosulfate (PMS)-coupled heterotrophic ammonia assimilation (HAA) system was established to achieve satisfactory system performance for OPW treatment. Pyrite sustained-release Fe2+-activated PMS was used to produce SO4•− and •OH, and 71.0 % of TPHs were effectively removed from the oil wastewater. The average TPHs and NH4+-N removal efficiencies in the test group with pre-oxidation were 96.9 and 98.3 %, compared to 46.5 and 77.1 % in the control group, respectively. The maximum fluorescence intensities of tryptophan protein and aromatic protein in the test group declined by 83.7 %. Fourier transform ion cyclotron resonance mass spectrometry revealed that pre-oxidation degraded more long-chain hydrocarbons and aromatic family compound, whereas the HAA process produced more proteins and carbohydrates. Pyrite-PMS promoted the enrichment of ammonia-assimilating bacteria, alleviating the explosive increase in extracellular polymeric substances and reducing sludge settleability. The low cost, efficiency, green chemistry principles, and synergies of this approach make it a powerful solution for practical OPW treatment to reduce environmental impacts and promote sustainable wastewater treatment.

Microfiltration, ultrafiltration and nanofiltration as a post-treatment of biological treatment process with references to oil field produced water of Moran oilfield of Assam

The selection of an apt technology for the treatment of Oilfield Produced Water (OFPW) depends mainly on the quality of OFPW and methods of pre-and post-treatment processes. The most challenging part of the OFPW treatment process is the removal of Suspended Solid (SS), Oil & Grease (O&G) and dissolved organics. SS and O&G pose an acute problem to the membrane filtration system by fouling the membrane surface which increases operation & maintenance costs and decreases the life of the membrane. Fouling of the membrane surface is mainly attributed to the presence of low molecular weight aromatic compounds and naphthenic acids in the suspended and dissolved organic compounds. Thus, the removal of these suspended and dissolved organic compounds before membrane filtration proffers a challenge to the researchers. In this research, bioremediation process has been applied to remove the organic compounds and the performance and fouling behaviour of hollow fibre Microfiltration (MF), Ultrafiltration (UF) and Nanofiltration (NF) membranes after the bioremediation process has been analyzed in detail. The level of toxicity was determined by comparing the pollutants with the safe discharge limit for disposal into the environment set by Central Pollution Control Board (CPCB), India. The research presents its novelty by using a hydrocarbon-degrading bacteria, Pseudomonas aeruginosa for the Reduction of Organic Loads (ROL) from OFPW of Moran oil field of Upper Assam as a pre-treatment to membrane filtration. The Total Sum Corrected Area (TSCA) method through chromatographic analyses was used for this. The organic loads removal from OFPW by the TSCA method was found to be 67–100%, 100% and 100% after 7, 14 and 21 days of bioremediation respectively. The major parameters in feed OFPW of Moran oil field were found to be pH (7.5–9.3), Total Dissolved Solid (TDS) (1.79–4.75) ppt, O&G (1.78–2.8) ppt, Salinity (2.94–6.98) ppt, Chloride (Cl−) (1.6–3.86) ppt, Bicarbonate (HCO3−) (2.89–4.03) ppt. It was observed that the ranges of pollutants removal by NF was highest such as TDS (26–86%), salinity (81–86%), turbidity (78–94%), hardness (67–75%), O&G (96–99%), Cl− (80–89%) and HCO3− (95–97%).

Total Dissolved Solids, Phenol, and Barium Removals from Oilfield Produced Water Using Kapok Fibers and Ultrafiltration Membrane

Oilfield-produced water treatment using raw Kapok fiber (RKF) and a modified surface of Kapok fiber followed by an ultrafiltration membrane was conducted to reduce total dissolved solids (TDS), phenol, and barium. Variables considered in the experiment were contact times (30, 60, 90 min.), the flow rate of samples (5, 6, and 7 L/min), and trans-membrane pressure of ultrafiltration membrane (0.25, 0.35, and 0.50 bar). Raw Kapok fiber and modified surface Kapok fiber were used to investigate the effect of Kapok fiber on total dissolved solids, phenol, and barium removals from produced water. The results showed that raw KF decreased the TDS, phenol, and barium by 51.81%, 62.63%, and 54.20%, respectively. Treatment of raw Kapok fiber column filtrate using ultrafiltration membranes (UF) showed the removal of TDS, barium, and phenol achieved 73.15%, 42.44%, and 79.45%, respectively, at a flow rate of 5 L/min, TMP of 0.25 bar, and contact time of 90 min. Modifying the Kapok fiber surface using sodium hydroxide solution (5 wt%) and hot water (98.5 °C) reduced the TDS, phenol, and barium to 57.32%, 65.83%, and 79.08%, respectively. Further, at the same operating condition, the modified surface of Kapok fiber followed by UF decreased 94.31% TDS, 84.20% phenol, and 56.23% barium, respectively. The results show that modification of the Kapok fiber surface followed by UF can be used to remove the TDS, phenol, and barium from produced water.

Insights into the foulants characteristics in a walnut shell biofilm-membrane bioreactor during treatment of hypersaline oilfield produced water

The characteristics and behavior of membrane fouling in oilfield produced water treatment systems are highly affected by the complex nature of this stream. The present study is dedicated to the characterization of the membrane foulants in a hybrid moving bed and membrane bioreactor (MBBR-MBR) system using walnut shell as a bio-carrier, for treatment of real produced water at total dissolved solids (TDS) concentrations of 35,000, 90,000 and 200,000 mg/L. The impact of using walnut shell on fouling was also investigated. Various analytical methods including attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), gas chromatography- mass spectrometry (GC–MS) were used to identify the organic compounds and inductively coupled plasma- optical emission spectrometry (ICP- OES), X-ray fluorescence (XRF), energy-dispersive X-ray spectroscopy (EDS) and X-ray powder diffraction (XRD) were applied in order to investigate the inorganic constituents present in the foulants. Additionally, field emission scanning electron microscopes (FE-SEM), atomic force microscopy (AFM) and particle size distribution (PSD) analysis were used as auxiliary tools to investigate the morphology and particle size distribution of the cake layer. The results indicated that the most important organic compounds identified included microorganisms, microbial products, and hydrocarbons. Also, the most important inorganic elements included Na, Cl, K, Ca, S, and P which probably originated from NaCl, CaCO3, and Ca-P precipitates. Walnut shell was effective in reducing membrane fouling due to the scouring effect, as well as altering the properties of sludge, and adsorption of oil compounds.

New insights in the treatment of real oilfield produced water: Feasibility of adsorption process with coconut husk activated charcoal

Naphthenic acids are water-soluble organic compounds (WSO), present in oilfield produced water (OPW), whose removal aims to comply with environmental legislation and ensure the correct disposal of OPW. In this study, the performance of the adsorptive process for the removal of WSO in synthetic (single- and multi-component) and real OPW was evaluated. It was observed that the lower the pH of the sample, the greater the adsorption capacity of WSO. Moreover, the kinetic parameters of adsorption followed the pseudo-second order model while the equilibrium parameters were represented by the isothermal BET (Brunauer, Emmett and Teller) model. In the desorption process followed the second-order model, and the aqueous solution of sodium hydroxide (0.3 and 0.1 M) showed the highest desorption efficiency (~70 %) in the synthetic and real systems, respectively. With this protocol, the adsorbent proved to be effective for the treatment of OPW, without significant loss of efficiency, for up to three consecutive cycles of adsorption-desorption. In addition, after treatment, the real effluent was classified within the legal parameters for offshore disposal, which enhances its industrial application.

Synergistic effect of adsorption and photocatalytic degradation of oilfield-produced water by electrospun photocatalytic fibers of Polystyrene/Nanorod-Graphitic carbon nitride

Graphitic carbon nitride with nanorod structure (Nr-GCN) was synthesized using melamine as a precursor without any other reagents by hydrothermal pretreatment method. XRD, FTIR, SEM, N2 adsorption-desorption from BET, UV–Vis DRS spectroscopy, and photoluminescence were used to characterize the prepared samples. Also, the photoelectrochemical behavior of nanoparticles was studied by photocurrent transient response and cyclic voltammetry analysis. Polystyrene (PS) fibrous mat was fabricated by electrospinning technique and used as a support for the stabilization of the nanoparticles. The performance of the synthesized nanoparticles and photocatalytic fibers (PS/Nr-GCN) was evaluated in oilfield-produced water treatment under visible light irradiation. During this process, oil contaminants were adsorbed by hydrophobic polystyrene fibers and simultaneously degraded by Nr-GCN. The removal efficiency of chemical oxygen demand (COD) has been obtained 96.6% and 98.4% by Nr-GCN and PS/Nr-GCN, respectively, at the optimum conditions of pH 4, photocatalyst dosage 0.5 g/L, COD initial concentration 550 mg/L, and illumination time 150 min. The gas chromatography-mass spectroscopy analysis results showed 99.3% removal of total petroleum hydrocarbons using photocatalytic fibers of PS/Nr-GCN. The results demonstrated that the GCN has outstanding features like controllable morphology, visible-light-driven, and showing high potential in oily wastewater remediation. Moreover, the synergistic effect of adsorption and photocatalytic degradation is an effective technique in oilfield-produced water treatment.

The structure design and offshore oilfield experiment study of industrial compact flotation unit

The Compact Flotation Unit is widely used in the offshore oilfield produced water treatment based on the characteristics of relatively small footprint and high oil removal efficiency, but the structure details of the Compact Flotation Unit have been rarely described up to now. Few literature is talking about the Compact Flotation Unit design process and systematically analyzing the influence of operating parameters on the oil removal efficiency, especially on the large-capacity industrial-level Compact Flotation Unit products. In this paper, the working principle and structure design process of the Compact Flotation Unit from Beijing Institute of Petrochemical Technology cooperated with China National Offshore Oil Corporation Research Institute were systematically introduced. Furthermore, the single-stage Compact Flotation Unit from Beijing Institute of Petrochemical Technology of industrial scale with a treatment capacity of 120 m³/h was manufactured and tested on floating production storage and offloading unit located in the South China Sea. When the inlet average oil content was 280.3 mg/L, the outlet average oil content was 39.9 mg/L, and the corresponding average oil removal efficiency was 85.8%. The flow split ratio, back pressure, and inlet flow rate have a significant impact on the oil removal efficiency, while the effect of the gas-liquid ratio and outlet water recycle ratio are not sensitive. The main reason can be attributed to the dissolved gas components in the produced water. A large quantity of microbubbles is generated after depressurization which directly participates in the flotation process. Besides that, the single-stage Compact Flotation Unit prototype can tolerate the fluctuation of inlet flow rate and oil content.

Structure design and industrial experiment of compact flotation unit for refinery wastewater treatment

The compact flotation unit (CFU) has been widely used in offshore oilfield-produced water treatment with the characteristics of compact structure and high oil removal efficiency. However, there is no published literature talking about CFU’s application in refinery wastewater treatment. In this paper, an innovative designed two-stage series BIPTCFU process diagram for refinery wastewater treatment was proposed. The structural design of the core BIPTCFU with a capacity of 20 m3/h was also carried out. After that, the manufactured industrial prototype of BIPTCFU-III-20 was tested in a SINOPEC petrochemical wastewater treatment plant. The single-factor operation test results show that with the increase of gas-liquid volume ratio, the oil removal efficiency of the BIPTCFU-III-20 increases first and then stabilizes. The reason can be ascribed to the microbubble number density which contributes to the oil removal efficiency. With the increase of inlet water flow rate, the oil removal efficiency first increases and then decreases. The reason is that as the inlet flow rate increases and approaches the rated treatment capacity, a stable swirling flow field is gradually formed in the vessel which benefits to the oil removal performance. While when the inlet water flow rate exceeds the rated capacity, the calculated hydraulic retention time was too short to complete the air flotation process. Under the optimal operation parameters, the oil removal performance of the BIPTCFU-III-20 on refinery wastewater was remarkable, and the average oil removal efficiency was 81.65 % when the inlet oil content was higher (1307 mg/L ∼ 4486 mg/L). While, when the inlet oil content is lower (150 mg/L ∼ 393 mg/L), the average oil removal efficiency was 77.75 %. The effect of low inlet oil content on the oil removal rate is more significant than that of high oil content. Based on the above basic research results, an industrial BIPTCFU with a rated capacity of 100 m3/h was constructed. The remarkable oil removal performance of the refinery wastewater was further verified.

Dose optimization of oil field produced water and advanced water treatment for heavy viscous oil

The treatment and disposal of oil field-produced water from pay zones presents a variety of issues for the hydrocarbon industry. Significant laboratory experimentation is carried out in this research program to design optimized dosages of oil field chemicals to design a water treatment plant for a thin stacked reservoir containing heavy viscous oil. When produced water is produced by pay zones containing heavy viscous oil, treatment can be difficult. For a better understanding of treatment procedures, chemical properties and physical properties of produced water are analysed. For re-injection of producing water to maintain reservoir pressure, the produced water must be compatible with the rheology of the reservoir under study. If the water leaving oil fields is untreated, it creates problems with injectivity loss and formation degradation, contaminating local groundwater resources and causing a significant environmental disaster. When significant amounts of oil field water is generated, the cost of water treatment chemicals rises dramatically. As a result, after examining the ionic concentration of generated water, this research effort recommends optimizingchemical dosing. Various filtration tests for effective rock fluid compatibility, include series, care, and coarse. The entire water treatment system was designed on prescribed treatment chemical dosages. The primary phase of generated water purification in this study relies heavily on the water treatment technologies of coagulation and flocculation. This processed oil field-producedwater is ideal for Enhanced Oil Recovery such as Alkali Surfactant-Polymer flooding.

Durable superhydrophobic engineered mesh with self-healing and anti-corrosive capabilities for efficient oil/water separation

The complex composition of oilfield-produced water is easy to scratch or corrode the separation membrane because of the existence of solid micro-particles, corrosive acid and alkali, proposing higher requirements on the durability of the membrane. Herein, a durable self-healing stainless-steel mesh was fabricated by hydrothermal growth of Ni and Fe double hydroxide nanosheet structure and dip-coating of polydimethylsiloxane (PDMS). The coating of ultrathin PDMS on the top of the nanosheets excellently maintained roughness of surface, while the PDMS stored at the valleys of the nanosheets array acted as a supplementary source for continuous self-healing process. Therefore, the engineered mesh could self-heal its superhydrophobicity despite suffering from different scales of damage. Moreover, the prepared mesh exhibited reliable superhydrophobicity, mechanochemical durability, corrosion resistance and self-cleaning properties. Eventually, the mesh showed ultrafast flux (21,000 L m−2 h−1) and rejection rate (> 99.99%) for separating phenixin/water mixtures during 50 continuous cycles. In addition to low-viscosity oils, the engineered mesh could separate high-viscosity crude oil/water mixtures. Aiming at the practical problem that dirty oil containing solid micro-particles is difficult to separate, the three-phase separation performance of the mesh on oil/water/sand mixtures was studied. These features make the engineered mesh have great practical application potential in oilfield-produced water treatment.

Onshore oilfield produced water treatment by hybrid microfiltration-biological process using kaolin based ceramic membrane and oleaginous Rhodococcus opacus

This study examined the treatment of onshore oilfield produced water by various strategies: microfiltration, biological treatment, microfiltration followed by biological treatment (MF-B), and biological treatment followed by microfiltration (B-MF). Microfiltration experiments were carried out at various applied pressures (69–345 kPa) using a tubular ceramic membrane prepared from inexpensive clays (kaolin and quartz). Maximum removal efficiency values of the parameters total suspended solids (TSS) (100 %), turbidity (100 %), total organic carbon (TOC) (84 %) and chemical oxygen demand (COD) (78 %) were obtained at a low pressure of 69 kPa. Complete removal of TSS and turbidity were observed at all the applied pressure values. However, the COD and TOC removal efficiency decreased with an increase in applied pressure from 69 to 345 kPa. In order to meet the discharge limits of the treated water parameters, other alternative techniques were investigated such as biological treatment, MF-B and B-MF. The oleaginous bacterium Rhodococcus opacus was used for the biological treatment of produced water. The results revealed that combined MF-B system was most effective, showing 99 % removal efficiency for TOC and COD compared to all other systems (microfiltration, biological treatment, and B-MF). Cleaning efficiency of membrane was investigated by using different chemical reagents and a mixture containing 0.10 wt% sodium dodecyl sulfate and 1 wt% NaOCl resulted in a maximum flux recovery of 92.60 %. Furthermore, toxicity assessment of the treated water obtained from MF-B system revealed maximum germination index of 74.30 % for Cicer arietinum and 71.10 % for Vigna mungo. Hence, it can be concluded that, hybrid MF-B system is highly efficient for complete removal of TOC, COD from produced water and reuse of the treated water.

Preparation of acrylate-modified cationic flocculant by polymer reaction and its performance in treating oilfield-produced water

Introducing a lipophilic group into a cationic polymer flocculant can effectively improve the flocculation performance for treating oilfield-produced water. Copolymerization of acrylate and cationic monomers is the most commonly used method; however, the acrylate content in the copolymer is limited by its solubility in water. In this study, a polymer reaction method was proposed to introduce a suitable acrylate into a cationic polymer to improve flocculation performance. Acrylate was introduced into the copolymer (PDD) of methacryloyloxyethyltrimethylammonium chloride (DMC) and diallylamine (DAA) via the reaction between acrylate and the secondary amine in PDD. The effects of the acrylate type, amount of acrylate introduced, and reaction conditions on the flocculation performance of the product were investigated. The experimental results showed that the hydroxy-terminated acrylate-modified PDD exhibited considerably better performance than PDD, especially the hydroxyethyl acrylate (HEA)-modified PDD (PDD-HEA). When the dosage was 20 mg/L, the oil removal of PDD-HEA was 95.8 %, which was 1.5 times higher than that of PDD. The introduction of HEA can improve the ability of PDD to aggregate oil droplets, but it causes curling of the PDD molecular chain and weakens its bridging and flocculation ability. Therefore, a higher amount of HEA introduced does not necessarily lead to a better performance of the PDD-HEA. The most suitable modification degree of the structural units in PDD was 3.3 %. This study provides new insights into the synthesis and properties of hydrophobically modified cationic polymer flocculants and is helpful for the development of flocculants for oilfield-produced water treatment.

Biokinetic Study of Microbial Decontamination of Oilfield Produced Water

This work was aimed at identifying microbials and determining the biokinetic parameters for bio-decontamination of oilfield produced water. An extant physical treatment unit for produced water was re-engineered and retrofit with a discontinuous aerobic bioreactor (Bio-Unit) system. The Bio-Unit was operated in a fill-and-draw sequence and the rates of total organic carbon (TOC) removal and biomass growth were monitored. The isolated microbial strains were identified as Bacillus, Pseudomonas and Chryseobacterium spp. The biokinetic parameters of the bio-detoxification process were determined by fitting experimental data into the Monod Equation. The maximum specific substrate utilization rate (k_m), maximum specific growth rate (μ(m,h )), substrate half saturation coefficient (K(STOC )), yield (Y), and endogenous decay rate (b_h), were found to be 0.20 day-1, 0.31 day-1, 2.7 mg TOC/l, 1.6 mg MLSS/mg TOC, and 0.23 day-1, respectively. These values are within the range published in literatures for oilfield produced water, thus will suffice for designing, modeling and control of biological treatment systems, since biokinetic parameters for real oilfield produced water treatment using discontinuous biological configuration is scanty.

Oilfield-produced water treatment using bare maghemite nanoparticles

Oilfield-produced water (PW) can be cleaned using a variety of techniques. However, traditional methods are often expensive and can generate secondary waste that pollutes the environment. In addition, PWs contain highly stable micronized dispersed oil, which makes conventional treatment ineffective in meeting regulatory requirements. As a result of their unique properties, magnetized nanoparticles can effectively remove emulsified and dissolved oil from PW. This study aims to evaluate the residual oil removal efficiency of bare maghemite (γ-Fe2O3) nanoparticles in treating oilfield-produced water (produced water).Several techniques for manufacturing maghemite nanoparticles were evaluated to select one that is both cost-effective and produces high-quality nanoparticles. After manufacturing nanoparticles with the selected method, the mineral composition and properties of the nanoparticles were determined. Subsequent experiments used synthetic and commercial nanoparticles to treat samples of PWs derived from oil and gas wells. By measuring the oil content of PW before and after treatment, the removal efficiencies of the nanoparticles were determined. Nanoparticles were recovered from treated PW samples, washed, and reused. Over ten times, they were recycled. The recycling potential of nanoparticles is evaluated by assessing the reduction in oil removal efficiency after recycling. Using fresh nanoparticles, over 98% of residual oil can be removed. Even after recycling more than 11 times, the oil content of treated PW samples was below the disposal limit. However, a slight reduction in the efficiency of the nanoparticles was observed. The reduction could be attributed to their dissolution in water and carryover during the treatment/demulsification operation.