COD removal from gasfield produced water using photoelectrocatalysis process on coil type microreactor

Coupling iron-carbon micro-electrolysis with persulfate advanced oxidation for hydraulic fracturing return fluid treatment

Improving the sustainability of the hydraulic fracturing water cycle of unconventional oil and gas development needs an advanced water treatment that can efferently treat flowback and produced water (FPW). In this study, we developed a robust two-stage process that combines flocculation, and iron-carbon micro-electrolysis plus sodium persulfate (ICEPS) advanced oxidation to treat field-based FPW from the Sulige tight gas field, China. Influencing factors and optimal conditions of the flocculation-ICEPS process were investigated. The flocculation-ICEPS system at optimal conditions sufficiently removed the total organic contents (95.71%), suspended solids (92.4%), and chroma (97.5%), but the reaction stoichiometric efficiency (RSE) value was generally less than 5%. The particles and chroma were effectively removed by flocculation, and the organic contents was mainly removed by the ICEPS system. Fourier-transform infrared spectroscopy (FTIR) analysis was performed to track the changes in FPW chemical compositions through the oxidation of the ICEPS process. Multiple analyses demonstrated that PS was involved in the activation of Fe oxides and hydroxides accreted on the surface of the ICE system for FPW treatment, which led to increasing organics removal rate of the ICEPS system compared to the conventional ICE system. Our study suggests that the flocculation-ICEPS system is a promising FPW treatment process, which provides technical and mechanistic foundations for further field application.

Sheep Dung Ash as a Low-Cost Adsorbent for the Reduction of COD of Highly Polluted Oilfield-Produced Water

Herein, we introduce a low-cost, available, renewable, and effective solid adsorbent used for oilfield-produced-water treatment using a straightforward treatment process. In the present study, sheep dung ash was prepared using the same way this waste is produced in rural areas when sheep dung is used as a source of energy for cooking and heating: by burning sheep dung with a direct flame. The prepared ash was characterized using FTIR, EDX, and SEM analysis techniques. The feasibility of the ash as a low-cost, available, renewable, and effective adsorbent for reducing the COD of oilfield-produced water with the initial COD of 21,600 mg/L was investigated. The effect of adsorbent dose, contact time (in hours and days), initial pH value, and initial COD value on the efficiency of sheep dung ash in COD adsorption was examined at room temperature. With shaking, the maximum capacity of sheep dung ash for COD reduction was found to be 71.8% at an adsorbent dosage of 30 g/L, an initial pH of 7, and a contact time of 1 h. Without shaking, a maximum capacity of 75% for COD reduction was obtained at an adsorbent dosage of 30 g/L, an initial pH of 7, and a contact time of 4 days. By applying the experimental results on Langmuir and Freundlich models of adsorption, it was found that the adsorption process of COD causing molecules follows both Langmuir and Freundlich models.