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The extraction of underground resources has accelerated globally, in response to the demands of advancing technology and the rapidly growing population. The increase in drilling activities has caused an increase in environmental pollution problems caused by waste generated during drilling activities, namely drilling sludge and drilling wastewater. In this study, the treatability of wastewater generated during drilling operations in a basin, where an underground gas storage area was created, was investigated using an electrocoagulation (EC) process, using different electrode pairs. The removal efficiencies of the pollution parameters were determined using the response surface method. The wastewater parameters included different organic and inorganic pollutants, such as sodium, chloride, magnesium, and chemical oxygen demand (COD). The concentrations of sodium, chloride, and COD in drilling industry wastewater were found to be very high, at 128,567, 185,292, and 7500 mg/L, respectively. The data obtained in this study yielded a removal efficiency of approximately 65% and above. Sodium achieved the highest pollutant removal efficiency of 85% and above. The statistical values were interpreted for all the pollutants and the suitability of second-degree regression was observed.

Large amount of drilling wastewater was generated during the exploitation of oil and gas field, which contains high concentration of suspended solids and organic matter. The reuse of drilling wastewater was an important way to solve the problem of water shortage during the development of oil and gas field. Therefore, hybrid ozonation-coagulation (HOC) as an integrated water treatment process was applied for the treatment of secondary effluent of drilling wastewater, which combines ozonation and coagulation in one reactor. During the HOC reaction, lots of ozone microbubble flocs were generated. Under the optimal conditions of pH 7, polyaluminum chloride (PAC) dosage 40 mg Al/L, ozone dosage 0.8 mg/L and reaction duration for 15 min, the removal efficiency of UV254, UV280 and DOC reached 20.07%, 37.97% and 14.51%, respectively. Benzene ring, proteins and humic acids were greatly reduced according to fluorescence analysis. The Fourier transform infrared spectrometer (FT-IR) analysis results showed that adsorption and interphase transfer to ozone microbubble flocs were the major mechanism for C-O functional groups removal. Enhanced decreased proportion of oxygen-containing groups can be observed in the effluent of drilling wastewater treated by ozone microbubble flocs compared with conventional microbubble flocs based on X-ray photoelectron spectroscopy (XPS) analysis. However, the ratio of oxygen-containing groups increased after the treatment of microbubble ozone, which implied that the synergistic effect during the treatment using ozone microbubble flocs, which involved oxidation, adsorption and flotation.

Due to water resource limitations and the environmental challenges associated with wastewater generated during oil and gas well drilling processes, the treatment and reuse of drilling wastewater have become essential. In Iran, most drilling wastewater treatment is conducted chemically using coagulant and flocculant agents, typically managed by on-site jar testing, which requires high technical expertise and can be time-consuming and prone to human error. Replacing this conventional approach with artificial intelligence techniques can significantly accelerate the process and reduce operational inaccuracies. In this study, data from 200 drilling waste management reports across various wells in the West Karun oilfields were collected, including input wastewater characteristics, dosages of polyaluminum chloride (coagulant) and polyacrylamide (flocculant), and the quality of the treated effluent. After conducting sensitivity analysis to select relevant input-output parameters, predictive models were developed using Recurrent Neural Networks (RNN), a hybrid PSO-RNN model, Extreme Learning Machines (ELMs), and Random Forest (RF). Each model was trained, tested, and validated, and their performance was evaluated using correlation coefficient (R) and root mean square error (RMSE). The validation results showed that for coagulant prediction, the RF model achieved the highest R value (0.89), while for flocculant prediction, the ELMs model outperformed others with an R value of 0.95. In terms of error, the ELMs model demonstrated the lowest RMSE values for both coagulant (0.13) and flocculant (0.10) predictions. ELM and Random Forest showed strong predictive performance ( R  ≈ 0.95, RMSE ≈ 0.10 g/m³), with high NSE (> 0.85) and low AIC (< 110), confirming model robustness and stability through cross-validation. Overall, Among the four models tested, the ELMs model demonstrated relatively strong predictive performance in both coagulant and flocculant estimation tasks, though limitations in capturing extreme values remain.

Although a three-dimensional electrode system (3DES) has made remarkable achievements in improving the property of electrodes and investigating pollutant degradation mechanism, the design of an electrochemical reactor for application in drilling wastewater has not been reported yet. In this study, a novel half-batch multi-cell 3DES reactor was constructed by us to degrade organic compounds from drilling wastewater. The separate effect of electrolysis time, current density, the configuration of granular activated carbon (GAC) electrodes, aeration rate and volumetric recirculation flow on chemical oxygen demand (COD) removal and energy consumption of the half-batch reactor were analyzed, and further optimization via response surface methodology (RSM). Results showed that the optimal operation conditions for the reactor included electrolysis time of 100 min, a current density of 9.2 mA/cm2, GAC electrode vertical configuration, an aeration rate of 2.67 L/min and a volumetric recirculation flow of 100 mL/min. Under these conditions, the maximum percentage COD removal was found to be 97.39% with an energy consumption of 77.89 kWh(kg COD)−1. The residence time distribution (RTD) method was carried out in continuous flow pattern to investigate the hydrodynamic characteristics of the reactor. Results showed that flow rate was the most dominant factor for the flow pattern of the reactor, followed by the aeration rate and current density. The low dispersion number and the percentage of dead volume are 0.214 and 3.87% when the flow rate of 100 mL/min, respectively, which indicates that there is an intermediate flow pattern existing in between plug-flow ideal and complete mixing flow, furthermore, it is close to the plug-flow ideal.

The 3-chloro-2 hydroxypropyltrimethyl ammonium chloride was successfully introduced into the β-cyclodextrin-modified chitosan to create the multicomponent adsorbent O-HTACC-g-CD. The structure of sorbent was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The adsorption capacity of O-HTACC-g-CD toward phenol was investigated as a function of pH, temperature, contact time as well as adsorbent dosage. The Box-Behnken response surface methodology was employed to optimize the effects of experimental parameters including adsorbent dose, pH, and time on the adsorption of phenol at 298.15 K. The obtained optimal values for adsorbent dose, pH, and time were 0.06 g, 6, and 200 min, respectively. The obtained experimental data follows the pseudo-second-order kinetic and Langmuir model. The thermodynamic parameters such as free energy change, enthalpy change, and entropy change were calculated, revealing that adsorption of phenol on O-HTACC-g-CD is a spontaneous and exothermic process. The prepared O-HTACC-g-CD displayed high adsorption capacity (39.98 mg g −1 ) and excellent removal rate (96%) for phenol from the aqueous solution at 288.15 K. The gained removal rates of chemical oxygen demand (COD Cr ) were in the range of 60.6–61.2%. Considerable results of sorption could be attributed to the multicomponent structure of the adsorbent with more active sites including the cavities, amino, and carboxyl functional groups which provided better sites for the phenolic pollutant to adsorb on the adsorbent via Van der Waals force, hydrogen bond, and the inclusion effect. Therefore, the results obtained strongly suggest that O-HTACC-g-CD could be an effective adsorbent for the removal of phenol and COD cr from drilling wastewater.

This paper aims to solve the problems of difficult breakage and low water yield of wastewater-based drilling fluids. The effects of breakage agent dosage, reaction temperature, stirring speed, and pumping time on the water yield of wastewater-based drilling fluids were analyzed through one-way experiments, and these parameters were optimized by Response Surface Methodology (RSM). A Radial Basis Function Neural Network (RBF) model was also introduced to compare its performance with that of RSM in predicting optimal process conditions. To further improve the accuracy of the model, a combination of Genetic Algorithm (GA) and RBF was used for optimization. The results show that both RSM and RBF models can predict the water yield of wastewater-based drilling fluids with high accuracy, in which the coefficient of determination of the RSM model is 0.9939, which is better than that of the RBF model (0.9778). The optimal operating conditions are determined through numerical optimization: the amount of glue breaker added is 3.97 kg/m3, the reaction temperature is 51 °C, the stirring speed is 419 rpm, and the maximum water yield is 62.37%, which is the best-predicted water yield. The GA-RBF coupled model performed better in terms of root mean square error (RMSE), coefficient of determination (R2 = 0.998), and mean absolute error (MAE), and the t-test verified that there was no significant difference between the predicted and actual values. The maximum value of the water yield of the waste mud could reach 61.97% when the gum breaker was added at 3.83 kg/m3, the reaction temperature was 53 °C, and the stirring speed was 424 rpm, which provided an accurate and reliable theoretical basis and technical support for the harmless treatment of deep and complex drilling fluids.

Oil and gas exploration and development provide important energy sources for the world, and drilling fluid is an essential engineering material for oil and gas exploration and development. During the drilling of oil wells, drilling fluids are eventually discarded as waste products after many cycles. Abandoned drilling fluid constitutes one of the largest wastes generated during oil and gas exploration and development. Drilling fluid contains many chemicals, which turn into pollutants during use. Furthermore, when drilling is carried out to reach reservoir, the drilling fluid becomes contaminated with crude oil. It may also mix with groundwater containing salts and heavy metals. The resulting pollutants and harmful substances threaten the environment, humans, animals, and plants. The variety and complexity of drilling fluid waste have increased in recent years. Various countries and regions are paying more attention to the ecological environment, and effective methods are urgently needed to solve problems associated with of environmental pollution caused by drilling fluid wastes. At present, various physical, chemical, and biological methods have been proposed for the treatment of drilling fluid wastes: safe landfilling, stabilization/solidification treatment, physicochemical treatment, thermal treatment, supercritical fluid treatment, bioremediation, etc. All of these methods show promising characteristics, and they each have advantages and limitations; thus, treatment methods need to be selected according to the actual application scenarios. This critical overview is based on an extensive literature review, and it summarizes and expounds on the current drilling fluid waste treatment technologies and proposes views future potential and outlook.

Macroporous weak basic anion exchanger （D301R） was used to remove organic substances from drilling wastewater. The effect of pH, temperature and contact time on adsorption behavior was investigated in batch experiments, which indicated that the COD （Chemical Oxygen Demand） removal ratio of drilling wastewater was approximately 90%, and the COD of treated wastewater was below 70 mg/L under appropriate operating conditions. A mixed liquor of NaOH and NaCI was selected as desorbent because of its better elution performance. The results of column dynamic adsorption and regeneration showed that the COD of wastewater could be efficiently removed by D301R resin, and the resin was easily regenerated by the selected desorbent.

The coagulation/iron chipping micro-electrolysis process was used to treat drilling wastewater .A new method of the depth removal of CODCr in wastewater from petroleum drilling was put forward. The effects on the reaction were investigated by single factor tests. The optimal conditions of the treatment are given as follows: weight ratio of iron chipping to reactive carbon 0.5, pH1.0, reaction time 2 hours, normal atmospheric temperature, after reacting the pH in solution being adjusted to be 11 by lime milk. The experimental results showed that following chemical coagulation/micro-electrolysis process, the removal rate of chromaticity is 100%, CODCr could be reduced to less than 150mg/L and the treated wastewater can come to the first and the second discharge standard of state comprehensive discharge criteria GB8978-1996. The analytic result shows that lixivium from solidified sludge cake of per unit operation comply with the second kind of general industrial sold of state standard for pollution control on the storage and disposal site for general industrial sold,GB18599-2001.

Adsorbent is an important waste water-based drilling fluid treatment agent, which can adsorb and settle heavy metal ions, high polymer organics, and other soluble harmful substances in the waste drilling fluid. Traditional adsorbents such as polyaluminum chloride and polyacrylamide will produce other metal ions or toxic monomers after hydrolysis, which cannot fully meet the requirements of safety and environmental protection. Therefore, a new environmentally friendly waste water-based drilling fluid adsorbent, named RH-β-CD, was prepared by the Wilson etherification reaction, which was initiated by epichlorohydrin and ceric ammonium nitrate, and successfully grafted rhamnolipid and amine strong adsorption groups onto β-cyclodextrin. The adsorption effect and environmental protection performance of RH-β-CD on the organic matter and chromium ion in waste sulfonated water-based drilling fluid were evaluated and compared with commonly used adsorbents such as activated carbon, PAM, and polyaluminum chloride. The results show that RH-β-CD can effectively adsorb the organic matter in the filtrate of waste water-based drilling fluids, reduce its chemical oxygen consumption, and reduce the concentration of heavy metal ions in the filtrate. The effect is better than PAM, activated carbon, and polyaluminum chloride, with the BOD /COD >20% and EC >1,000,000 mg·L , which is environmentally friendly.