Abstract
Advanced oxidation technology is considered to be the most potential wastewater treatment technology. As one of the advanced oxidation technologies, the three-dimensional electrochemical system (3DES) is often used to treat industrial wastewater that is difficult to degrade. Sulphonated phenolic resin (SMP) was treated as a characteristic pollutant in sulfonated drilling wastewater. The separate effect of current, the dosage of particle electrodes, chloride ion concentration and initial pH on chlorinated by-products were analyzed by response surface methodology (RSM). Results showed that current is the most dominant factor, followed by the dosage of particle electrodes. The ultraviolet-electrolysis (UVEL) system was implemented by adding ultraviolet light under the optimal electrolysis (EL) system. The chemical oxygen demand (CODcr) and total organic carbon (TOC) removal rates of the UVEL system were respectively increased by 19% and 29.39% compared with the EL system, the concentration of chlorinated by-products was also reduced by 534.4 mg/L when the UV irradiance was 5.24 mW/cm2. These results indicated that the UVEL system degrades SMP more thoroughly. The enhanced reaction mechanism of the UVEL system and the possible degradation pathway for SMP were proposed by controlling free radical quenching experiments and the product of EL and UVEL processes. The results showed that the high degradation efficiency of the UVEL system could be attributed to the synergistic degradation mechanism present in the UVEL system, where the photolysis of active chlorine species (ACl) promotes the increase of hydroxyl radical (·OH).
Highlights
The prerequisite for successful drilling of deep or ultra-deep wells is a high-density sulphonated drilling mud
Hou studied the formation of chlorinated by-products by S2O82À oxidation based-advanced oxidation processes (AOPs) in the presence of natural organic matter (NOM), these results indicated that the chlorinated by-products existed in the form of SO4À· and active chlorine species (ACl) mediators, which were completely degraded with NOM (Hou et al 2018)
The results showed that the chlorinated by-products in the novel process were reduced by 21.4%, which can be attributed to the synergistic effect of ·OH and ACl (Yin et al 2021)
Summary
The prerequisite for successful drilling of deep or ultra-deep wells is a high-density sulphonated drilling mud. SMP is usually used as an additive to prevent the loss of filtrate from sulfonated drilling mud. Various chemical additives (such as chlorine-containing chemical additives, SMP, etc.) inevitably remain in the used sulfonated drilling mud system. All in all, sulfonated drilling wastewater is a complex mixture with high COD, high chloride ion concentration and containing various drilling fluid components (Yang et al 2002). Current technologies for the treatment of sulfonated drilling wastewater include air flotation, coagulation, activated carbon adsorption, bio/coagulation and secondary coagulation. The application of these methods is constrained by the high investment and poor treatment results (Wang et al 2001). Higher requirements are put forward for the treatment of sulfonated drilling wastewater processes
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