The treatment of high concentration wastewater in the natural gas processing industry

Abstract

The operation of the Cansolv tail gas treatment device in natural gas plants generates acidic and alkaline wastewater from the venturi unit and amine purification unit (APU), respectively. The APU wastewater is complex in composition and contains hard-to-degrade organic matter, which can adversely impact the normal functioning of the water treatment system. This study assesses the efficacy of three ozone-based advanced oxidation processes (ozone (O₃), ozone/hydrogen peroxide (O₃/H₂O₂), and ozone/Fenton (O₃/Fenton)) for treating Cansolv wastewater, with chemical oxygen demand (COD) and total organic carbon (TOC) serving as indicators of organic degradation. The findings demonstrate that all three processes effectively eliminate coloration and reducible sulfur, with O₃/Fenton exhibiting superior performance in removing organic substances. The treated wastewater has a clarified light-yellow appearance with residual COD levels at 43 mg L⁻¹. Under the optimum Fenton oxidation conditions (initial pH 5, H₂O₂ dosage 97.8 mmol L⁻¹, FeSO₄·7H₂O dosage 550 mg L⁻¹), average TOC and COD removal rates reached 50% and 97%, respectively. After a treatment duration of 60 minutes, the wastewater demonstrated an enhanced membrane-specific flux, confirming the effectiveness of the O₃/Fenton oxidation process in mitigating membrane fouling while ensuring the stable operation of the wastewater treatment system.