Oilfield Wastewater Treatment Research Articles

Supercritical water synthesized Ni/ZrO2 catalyst and its application in the harmless treatment of oilfield wastewater in supercritical water

Supercritical water (SCW) catalytic gasification is a clean and efficient technology with prominent advantages in treating oily wastewater generated in oilfields. SCW synthesis is a promising one-step preparation method for nano-catalytic materials, while the influence of organic matter on SCW synthesis materials remains to be studied. This study focuses on the synthesis of the Ni/ZrO2 catalysts by the supercritical water synthesis (SCWS) method, particularly examining how different types and concentrations of organic matter affect the catalysts’ pore information and structural characteristics. It found that glycerol acted as a more effective precursor for generating reducing gases compared to glucose. This is attributed to glycerol’s capacity in SCW to generate reducing gases for activating a greater number of Ni site within the catalyst, and the 5 wt% glycerol should be a proper concentration for SCWS of Ni/ZrO2. When employed in SCW treatment of oilfield wastewater, the Ni/ZrO2 catalyst demonstrated impressive results, achieving the carbon gasification efficiency of 99.1 % and a chemical oxygen demand (COD) removal efficiency of 100 % at 500°C. These findings indicate that the SCW technique can effectively and harmlessly treat oilfield wastewater using the Ni/ZrO2 catalyst under relatively mild conditions, showing its potential as an innovative solution for wastewater management in the oil industry.

A Promising Device Based on Step Stage Theory for Highly Effective Treatment of Oil Field Wastewater

A Promising Device Based on Step Stage Theory for Highly Effective Treatment of Oil Field Wastewater

Effect of Light and Dark Regimes on Cultivation of Microalgae-Bacteria Consortium for Oilfield Wastewater Treatment

Effect of Light and Dark Regimes on Cultivation of Microalgae-Bacteria Consortium for Oilfield Wastewater Treatment

AgIn5S8/g-C3N4 Composite Photocatalyst Coupled with Low-Temperature Plasma-Enhanced Degradation of Hydroxypropyl-Guar-Simulated Oilfield Wastewater.

The effective treatment and recovery of fracturing wastewater has always been one of the difficult problems to be solved in oilfield wastewater treatment. Accordingly, in this paper, photocatalytic-coupled low-temperature plasma technology was used to degrade the simulated wastewater containing hydroxypropyl guar, the main component of fracturing fluid. Results indicated that hydroxypropyl-guar wastewater could be degraded to a certain extent by either photocatalytic technology or plasma technology; the chemical oxygen demand and viscosity of the treated wastewater under two single-technique optimal conditions were 781 mg·L-1, 0.79 mPa·s-1 and 1296 mg·L-1, 1.01 mPa·s-1, respectively. Furthermore, the effective coupling of AgIn5S8/gC3N4 photocatalysis and dielectric-barrier discharge-low-temperature plasma not only enhanced the degradation degree of hydroxypropyl guar but also improved its degradation efficiency. Under the optimal conditions of coupling treatment, the hydroxypropyl-guar wastewater achieved the effect of a single treatment within 6 min, and the chemical oxygen demand and viscosity of the treated wastewater reduced to below 490 mg·L-1 and 0.65 mPa·s-1, respectively. In the process of coupled treatment, the AgIn5S8/gC3N4 could directly absorb the light and strong electric field generated by the system discharge and play an important role in the photocatalytic degradation, thus effectively improving the energy utilization rate of the discharge system and enhancing the degradation efficiency of hydroxypropyl guar.

Effective degradation of recalcitrant naphthenic acids by the Fe(III)/peroxymonosulfate oxidation enhanced by molybdenum disulfide: Degradation performance and mechanisms

In this study, molybdenum disulfide (MoS2) has been investigated as a catalyst to boost the redox cycle of Fe(III)/Fe(II) to activate peroxymonosulfate (PMS) to effectively break down cyclohexanecarboxylic acid (CHA), which is a model naphthenic acid (NA) pollutant. The optimum conditions of pH 3, MoS2 concentration of 0.4 g/L, Fe(III) concentration of 0.3 mmol/L, and PMS concentration of 2 mmol/L has been applied for complete degradation of 0.1 mmol/L CHA in 10 minutes reaction time. Based on results of electron paramagnetic resonance analysis, chemical probe and quenching experiment, it was found that all of •OH, SO4•−, 1O2, and Fe(IV) contributed to the MoS2/Fe(III)/PMS oxidation system. Eighteen CHA byproducts and three primary CHA degradation pathways were revealed according to the results of UHPLC-QTOF-MS analysis. By using XPS, SEM, and XRD to characterize the MoS2 powders before and after the reaction, MoS2 was found with high stability and the oxidation of Mo(IV) on the surface was negligible. The impacts of background anions on CHA degradation were found to be nonimportant, and commercial NAs mixture were verified to be efficiently degraded in current system. Overall results indicate the capacity and potential of MoS2/Fe(III)/PMS system to be utilized for future treatment of authentic oil and gas field wastewater.

Oil-water separation process based on microbubble air flotation membrane device and scale-up research

The treatment of oily wastewater is of great significance to oilfield production and ecological environment protection. A microbubble air flotation membrane device integrating air flotation separation and membrane separation is proposed, and a purely physical process of wastewater treatment is designed, which has significant advantages in the treatment of oily wastewater, especially in the treatment of polymer-driven oily wastewater. In this paper, we studied the oil-water separation mechanism and the removal effect of suspended solids of the microbubble air flotation membrane device, examined the handling capacity, reflux ratio, dissolved air water gas-liquid ratio on the oil removal rate, and determined the optimal parameters of the process for the handling volume of 7.8 m3/h, reflux ratio of 15.57%, dissolved air water gas-liquid ratio of 1:10. The oily wastewater is discharged from the device and filtered by special quartz sand can be achieved with the oil content and suspended solids content were below 20 mg/L, and the oil removal rate was over 95%, which reached the reinjection standard. This study can help the treatment and utilization of oilfield wastewater, and realize the water resources, energy, energy saving, and emission reduction.

Mechanism of enhanced oil recovery by nanoparticles extracted from flowback fluids of acidizing oil wells

The silicates in flowback fluids from acidizing oil wells can be used as raw materials for the synthesis of nanomaterials, that are beneficial for the treatment of produced water and enhanced oil recovery. In this paper, the nanomaterials were synthesized from acidizing flowback fluids by sol-gel method and the reaction conditions were optimized. The interfacial tension, wetting angle and surface tension of the solution were measured. The test of displacement efficiency and flooding experiments were conducted in two dimensional flat cores to reveal the mechanism of enhanced oil recovery by nanoparticles. The results indicated that the nanoparticles with a diameter of 351 nm could be extracted and synthesized from acidizing flowback solution at low pH. Compared with other nanomaterials, the synthesized nanoparticles could change the interfacial properties between oil and water due to the complex acidizing process. When the injection concentration of nanoparticles reached 300 mg/L, the decrease of water cut reached the maximum, up to 27.16%, and the recovery rate during subsequent water flooding was 32.25%. Appropriately increasing the injection concentration of nanoparticles extracted from acidizing flowback fluids was beneficial to improve the recovery rate, so that realizing the efficient development of oil and gas resources. The research results can provide a new method for the treatment of oilfield wastewater.

A mechanistic mathematical model for the treatment of synthetic oil-field wastewater (produced water) by electrocoagulation process using aluminium electrodes.

Produced water (PW) is the largest by-product that comes out of the oil wells during oil and gas (O&G) field exploration. PW contains high-salt concentration along with other organic and inorganic components; therefore, PW must be treated before disposal. Electrocoagulation (EC) is an effective treatment method to remove pollutants from PW which has been the focus of many experimental studies; however, a mathematical model specifically for PW treatment by EC has not been developed yet. In this work, a comprehensive mathematical model has been developed to elucidate the role of EC operating parameters on the PW treatment performance and determine the mechanism for COD (Chemical Oxygen Demand) removal. The present model considers and identifies the dominant Al-hydroxy complex species and their contribution to the COD removal from synthetic PW samples by estimating their rate constants and comparing their magnitudes and investigates multi-scale modelling of the EC reactor. The influence of working parameters such as current density, initial pH, interelectrode distance, mixing speed and solution volume of PW on Al coagulant production and COD removal was investigated and modelled. The study estimates the rate constants of the reactions taking place for COD removal by EC process and by comparing their magnitudes identifies the dominant reactions and coagulant species involved in the process. The mathematical model prediction of COD removal fits well with the experimental data at 10mAcm-2, 15mAcm-2 and 20mAcm-2 current density with R2 value of 0.96, 0.97 and 0.92, respectively and for dissolved Al concentration R2 value of 0.96, 0.99, and 0.97, respectively. The simulated results reproduced a good fit at initial pH of 6.1, 7.3 and 8.6 with R2 value of 0.92, 0.96 and 0.98, respectively for COD removal. The mathematical model and the experimental results showed the role of dominant Al-hydroxy complex species such as , , , and in controlling the COD removal process. Under different operating conditions considered in the study, the model also predicted the COD removal performance of the EC reactors at different reactor volumes with R2 value of 0.96 for higher solution volume and larger reactor. The model presented and rate constants determined in the study will provide a theoretical basis for designing, scaling up and operating the EC reactor for oil-field PW treatment.

Washing performance of microbubbles on porous media

The backwashing effect of filter materials in oilfield wastewater treatment processes is essential for the efficient long-cycle operation of equipment and the reduction of hazardous waste. Recently, there has been growing interest in microbubble cleaning technology due to its exceptional cleaning efficiency for porous particles. However, the mechanism of microbubble-pore interaction and its corresponding cleaning effects remain unclear. This study investigated the performance of microbubbles in removing petroleum hydrocarbon pollutants from walnut shells, comparing them with traditional water washing and state-of-the-art ultrasound methods. Microbubble cleaning proved most efficient in removing low-viscosity petroleum hydrocarbons, followed by ultrasonic waves, both of which showed significantly higher efficacy compared to traditional water washing. When treating petroleum hydrocarbon pollutants with high viscosity, microbubble cleaning was more effective than clear water but slightly less effective than the ultrasonic wave method. Based on the analysis of clogging phenomena observed via scanning electron microscopy (SEM), the mechanism of microbubble cleaning within porous media was unveiled. Microbubbles were found to be proficient at dislodging contaminants adsorbed within secondary pores through collision and the force generated by liquid jets, as well as penetrating the small pores to eliminate pollutants from these inner spaces. Finally, an economic cost analysis of the various cleaning methods revealed that the microbubble approach is a cost-effective choice for the removal of light oil or the situations where a relatively lower removal efficiency for heavier oils is acceptable.

Preparation of Cationic Polyacrylamide Suspension and Its Application in Oilfield Wastewater Treatment.

Cationic polyacrylamide (CPAM) solid particle is one of the most commonly used organic polymer flocculants in oilfield wastewater treatment, but it poses some problems, such as a slow dissolution rate and an easy formation into a "fish-eye" in the process of diluting into aqueous solution. However, the current liquid CPAM products also have some problems, such as low effective content, poor storage stability, degradation in a short time, and high preparation costs. In this paper, a CPAM suspension was successfully prepared with 50.00% CPAM fine powder, 46.87% oil phase solvent, 0.63% separating agent, 1.56% emulsifying and dispersing agent, and 0.94% rheology modifier. This suspension has an effective content of 50.00%. It also showed no separation in 7 days of storage at room temperature, no separation in 30 min of centrifugation at a speed of 2000 rpm, and diluted to a 0.40% solution in just 16.00 min. For 1000 NTU of diatomite-simulated wastewater, the optimal turbidity removal rate of the suspension was 99.50%, which was higher than the optimal turbidity removal rate of 98.40% for the inorganic flocculant polymeric aluminum chloride (PAC). For oilfield wastewater, the optimal turbidity removal rate of the CPAM suspension was 35.60%, which was higher than the optimal turbidity removal rate of 28.40% for solid particle CPAM. In a scale-up test, the CPAM suspension achieved a good application effect.

Treatment of oilfield wastewater and synthesis of Na2FeO3 in a chloride ion anode oxidation system

This study investigates the degradation of oil recovery wastewater and generation of Na2FeO3 in an anodic oxidation system.

Synthesis of Porous MgAl-LDH on a Micelle Template and Its Application for Efficient Treatment of Oilfield Wastewater.

In this paper, a series of porous hierarchical Mg/Al layered double hydroxides (named as LDH, TTAC-MgAl-LDH, CTAC-MgAl-LDH, and OTAC-MgAl-LDH) was synthesized by a simple green hydrothermal method using wormlike micelles formed by salicylic acid and surfactants with different carbon chain lengths (0, 14, 16, and 18) as soft templates. BET, XRD, FTIR, TG, and SEM characterizations were carried out in order to investigate the structure and properties of the prepared materials. The results showed that the porous hierarchical CTAC-MgAl-LDH had a large specific surface area and multiple pore size distributions which could effectively increase the reaction area and allow better absorption capability. Benefiting from the unique architecture, CTAC-MgAl-LDH exhibited a large adsorption capacity for sulfonated lignite (231.70 mg/g) at 25 °C and a pH of 7, which outperformed the traditional LDH (86.05 mg/g), TTAC-MgAl-LDH (108.15 mg/g), and OTAC-MgAl-LDH (110.51 mg/g). The adsorption process of sulfonated lignite followed the pseudo-second-order kinetics model and conformed the Freundlich isotherm model with spontaneous heat absorption, which revealed that electrostatic adsorption and ion exchange were the main mechanisms of action for the adsorption. In addition, CTAC-MgAl-LDH showed a satisfactory long-time stability and its adsorption capacities were still as high as 198.64 mg/g after two adsorption cycles.

Clean treatment and resource utilization of oilfield wastewater using supercritical water gasification

Unconventional oil and gas resources are expected to be recovered efficiently by multi-component supercritical thermal fluid (MCSCTF) which is generated based on supercritical water gasification (SCWG) of oilfield wastewater and hydrogen oxidation technology. In this paper, SCWG experiments of oilfield wastewater were performed under 550–750 °C, 2–15 min, 21–29 MPa, and feedstock concentration of 2–10 wt%. High temperatures, extended residence times, and low concentrations encouraged the production of gases. There was no significant change in SCWG as the pressure changed. The highest H2 yields and carbon gasification efficiency (CE) were 52.31 mol/kg and 97.59%, respectively. The SCWG mechanism was summarized to describe the conversion details. The SCWG of oilfield wastewater has the fastest initial rate to present a trend of deceleration and the activation energy of CE was calculated as 135.7 kJ/mol. The reason for gasification deceleration was explained by the proposed gaseous product kinetics. Small molecules and saturated hydrocarbons etc. (Int 1) can be quickly decomposed while the decomposition of phenols and aromatic hydrocarbons etc. (Int 2) is slower. Inhibition of Int 2 generation and enhanced Int 2 decomposition is the key to total gasification. This work is useful for reactor design and process intensification.

Quantitative analysis on the oil content of oilfield wastewater based on a convolutional neural network model and ultraviolet transmission spectroscopy.

Oil content (OC) is one of the important evaluation indicators in oilfield wastewater (OW) treatment. The purpose of this study is to realize online real-time detection of OC in OW by combining ultraviolet spectrophotometry with the convolutional neural network (CNN). In this paper, 80 groups of OW transmission data were measured for model establishment. Three CNN models with different structures are established to generalize the super parametric optimization process of the model. Furthermore, as a common method used in spectroscopy, the synergy interval partial least squares (siPLS) model is built in order to compare its accuracy with the CNN model. The results indicated the CNN model has a better performance than siPLS, in which the CNN model numbered Model 3 has the lowest root mean square error (MSE) of prediction (RMSEP) of 1.606 mg/L. As a consequence, the CNN model can be used in the monitoring of OW. This article will guide a rapid analysis of the OC of OW.

Pilot-scale trail of a novel integrated process towards promoting polymer-flooding sewage treatment by reducing back-mixed feedstocks

The effective treatment of polymer-flooding sewage has attracted great concerns during the oilfield wastewater treatment. The low pollutant removal efficiency due to the high viscosity of polymer is addressed in the actual production process. In this work, a novel integrated process of “air flotation-(anaerobic-anoxic-aerobic)-ozone catalytic oxidation-dual media filtration-multimedia filtration” is presented. The viscosity of the treated effluent was reduced from 1.424 mPa·s to 0.942 mPa·s; Suspended solids and oil removal were 99.5%, biochemical oxygen demand, total nitrogen, total phosphate, and other biochemical indexes in polymer-flooding sewage were also removed efficiently. At the same time, more than 70% of the polymer retained in the effluent. The goal of improving the treating efficiency of polymer-flooding sewage while retaining polymer was achieved. This work provides an efficient approach for polymer-flooding sewage reuse.

Optimization of a combined electrocoagulation-electro-oxidation process for the treatment of Al-Basra Majnoon Oil field wastewater: Adopting a new strategy

The performance of a synergistic combination of electrocoagulation (EC) and electro-oxidation (EO) for oilfield wastewater treatment has been studied. The effect of operative variables such as current density, pH, and electrolyte concentration on the reduction of chemical oxygen demand (COD) was studied and optimized based on Response Surface Methodology (RSM). The results showed that the current density had the highest impact on the COD removal with a contribution of 64.07% while pH, NaCl addition and other interactions affects account for only 34.67%. The optimized operating parameters were a current density of 26.77 mA/cm2 and a pH of 7.6 with no addition of NaCl which results in a COD removal efficiency of 93.43% and a specific energy consumption of 128.6 kWh/kg COD. The most new findings of this research was that currents provided for the two anodes (Al and Graphite having the same surface area) were not equal between them and the current ratio (IAl/IGr) depends on the intensity of current, pH, and addition of NaCl. Besides, higher removal of COD occurs at a lower value of (IAl/IGr). The COD removal reaction was found to be pursued a second-order kinetic with a reaction rate constant (k) of 7.5847 × 10−5 (mg/L)−1/min.

Application of in-situ microbubble method on SEP@MnO2/RGO composite membrane for efficient and long-acting treatment of oil field wastewater

The treatment of oilfield wastewater has been a problem for oil workers for a long time. Indeed, it is economical, efficient and environmental friendly to treat oilfield wastewater with membrane. However, the contamination and stability of membrane limit the application of membranes. This study focuses on improving the long-term integrated treatment of oilfield wastewater by commercial PVDF membranes in different environments. Sepiolite(Sep)@MnO 2 composites were synthesized by hydrothermal method. SEP@MnO 2 and graphene oxide(GO) were left on the commercial PVDF membrane after vacuum filtration. Then the membrane was subjected to 120 vacuum thermal reduction. The prepared Sep@MnO 2 /RGO composite membrane showed good separation result and flux for different proportion of oilfield wastewater. Moreover, it can remove some common salt (NaCl,MgSO 4 , CaCl 2 , MgCl 2 ) and heavy metal ions (Ni 2+ , Fe 3+ , Cr 6+ ) in oilfield wastewater. Even more valuable, a few addition of H 2 O 2 to oilfield wastewater caused an oxidation reaction and the produced in situ microbubbles greatly enhance the antifouling property of the membrane. After 15 cleaning tests and 12 h of cycling, the membrane still showed strong separation ability. Compared with other oil-water separation membranes reported, this membrane demonstrated a longer and better separation effectively. All the work promotes the application of membrane separation technology in oilfield wastewater treatment. Hopefully, the application of in-situ microbubble method on membrane will solve the problem of membrane pollution in oilfield wastewater treatment. • The membrane can effectively treat the oil field wastewater with heavy metals and salts. • The application of in-situ bubble method on the membrane enhances the anti-fouling property of the membrane. • The membrane is qualified in a table and long-active treatment of oilfield wastewater.

Vortex coagulation treatment of oilfield wastewater.

In this study, the traditional coagulation process was optimized and a method of vortex coagulation for wastewater treatment was proposed for the first time. The process discards the sedimentation method used in traditional coagulation and uses agitation to bring flocs up. These flocs can then be stuck by the filter cotton fixed in wastewater, and the filter cotton and flocs can act as net capturing several times under the action of agitation. It is worth noting that the filter cotton and flocs can synergistically adsorb the suspended and organic pollutants from wastewater. The results showed that the chemical oxygen demand (COD) removal of vortex coagulation could reach 82%, which was 10% higher than that of the traditional coagulation under the same coagulant dosing. In addition, the flocs in conventional coagulation and vortex coagulation were analyzed by IR spectroscopy and XRD, which showed that the mixing process did not destroy the chemical structure of the flocs. Compared with the conventional method, this process does not require a sedimentation tank, which can avoid the investment of equipment construction in this area. The effects of coagulant dosage, pH, stirring speed, and stirring time on the wastewater treatment effects were explored in the experiment.

Enhanced Crude Oil Sorption by Modified Plant Materials in Oilfield Wastewater Treatment.

The treatment of oilfield wastewater with high crude oil content and complex composition is a problem requiring considerable attention. In order to effectively remove crude oil contained in wastewater, in this work, rice straw, as an oil-absorbing material, was modified and used as a sorbent for crude oil. Rice straw was modified with alkali and cetyltrimethylammonium chloride (CTAC) by simple substitution reaction. The adsorption capacity of modified rice straw for oil was evaluated. The results illustrate that the adsorption rate of rice straw for crude oil was increased from 0.83 to 8.49 g/g, with the optimal conditions of 18% NaOH reacted for 90 min at 50 °C and 2% CTAC reacted for 60 min at 20 °C. The proposed modification method could be used for different materials to enhance the adsorption rate. The results of the contact angle test show that the modified straw changed from hydrophilic to hydrophobic, which may be the main reason for the improvement in the oil absorption rate. Finally, the surface structure of rice straw was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption-desorption isotherms, which further confirmed the hydrophobicity of the modified rice straw.

Performance evaluation of an industrial ceramic nanofiltration unit for wastewater treatment in oil production

An industrial ceramic nanofiltration membrane (pore size 0.9 nm) was tested in a Canadian oil field for more than 12,500 h to treat wastewater directly from daily operations, without any type of pre-treatment. This wastewater contained a high content of total suspended solids (13 to 510 mg/kg), and total organic carbon (31 to 134 mg/kg). The membrane unit was operated at different transmembrane pressure (TMP) set points (4–16 bar) and recovery set points (40–80%). The data show that ion and compound rejection depend strongly on a combination of both TMP and recovery, with the largest rejection occurring at low recovery values and high TMP values. Two mechanisms were responsible for rejection: sieving, which mostly impacted compound rejection, and electrostatic phenomena that impacted ion rejection. It is shown that ion rejection depends linearly on charge density of the ion. Ion rejection was measured as high as 85% and compounds (such as TSS) were rejected as high as 100%. The specific flux varied between 1–10 L/(m2.h.bar). Results from this field testing indicate the possibility of using these types of ceramic membranes for oil field wastewater treatment.