The exploitation of shale gas resources brings in abundant hazardous oil-based drilling cuttings (ODBCs). Herein, N, N-Dimethylcyclohexylamine (DMCHA) acted as the CO2 switchable hydrophilic solvents (SHSs), and the OBDCs treated with DMCHA were studied, especially priority pollutant migration and produced wastewater assessment during the extraction process. The petroleum hydrocarbon content of OBDCs decreased from 10.73 to 0.84 wt% after the DMCHA extraction was conducted at a DMCHA/OBDCs liquid–solid ratio of 20:1, 35 °C, and 200 rpm for 30 min. Using the CO2 switchability of SHSs, the petroleum hydrocarbon and DMCHA were recovered. There was wastewater, which was produced after recovering DMCHA, and the produced wastewater assessment showed that chemical oxygen demand, 5-day biochemical oxygen demand, total nitrogen, total organic carbon, and petroleum were 561.00, 238.00, 40.60, 309.00, and 0.27 mg/L, respectively. Meanwhile, phenols (0.0031 mg/L), naphthalene (0.0000129 mg/L), phenanthrene (0.000059 mg/L), anthracene (0.000058 mg/L), as well as heavy metal ions such as Cu (0.01 mg/L) could be detected in the produced wastewater. As a result, a priority pollutant migration mechanism from ODBCs to the produced wastewater was proposed. This would be helpful for the better management policy making of the ODBCs treated by using CO2 SHSs and the produced wastewater.

The oxidation-absorption technology of tail gas is perfect for natural gas purification plants to ensure the up-to-standard discharge of sulfur dioxide emissions, but it can produce a large amount of wastewater. In this paper, a facile and full-scale reuse treatment strategy based on the sequential combination of disc tube reverse osmosis and low-temperature and low-pressure evaporation desalination was proposed and studied. The produced light yellow wastewater was acid sulfate-rich organic wastewater, in which sulfate ions (SO42−) existed up to 6479 mg/L, and the chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), total organic carbon (TOC), ammonia nitrogen (ammonia-N), total nitrogen (TN) and suspended solid (SS) were 207, 71.9, 67.6, 1.28, 70.5 and 20.9 mg/L, respectively. After the reuse treatment, there was COD (6 mg/L), BOD5 (1.4 mg/L), TOC (0.9 mg/L), TN (2.07 mg/L), SS (6 mg/L) and SO42− (90 mg/L) in permeated water, and condensate water with COD (11 mg/L), BOD5 (2.3 mg/L), TOC (4.3 mg/L), SS (2 mg/L) and SO42− (1.2 mg/L) was obtained. Thereby, pollution indexes were reduced after the reuse treatment so as to meet the water quality standard (GB/T18920-2022) in China, and the total water recovery rate reached 98.2 vol%. Ultimately, the priority pollutant migration mechanism during the reuse treatment process was determined.