Fit for Purpose H2S and Oil Removal System for a Sustainable Zero Liquid Discharge (ZLD) Produced Water Management Technology

Abstract The study focuses on Zero Liquid Discharge (ZLD) produced water desalination, an increasingly important process for recycling hypersaline wastewater and promoting a circular water economy in upstream operations. A key challenge in ZLD desalination is pre-treating produced water streams to remove hydrogen sulfide (H2S) and oil, as H2S is a harmful toxic gas and oil can cause operational issues in desalination units.1,2 The study aimed to develop and evaluate a fully automated pre-treatment system for removing H2S and de-oiling produced water streams. This system included a series of chemical dosing, integrated degassing, and de-oiling unit, and scrubbing units. The degassing unit, using a controlled nitrogen supply, efficiently removed H2S from the water. Chemical dosing was employed to aid in removing H2S, and oil, while the scrubbing unit targeted residual H2S in the vapor phase. Results indicated that the automated system was highly effective in both H2S removal and de-oiling, achieving up to 99% efficiency in both processes. Key factors contributing to this efficiency were the amount of chemical dosing, the residual time, and the controlled nitrogen supply in the degassing unit. The study demonstrates the feasibility of using a fully automated pre-treatment system for H2S and oil removal in ZLD produced water desalination projects. This system is particularly useful for treating sour produced water in both remote and populated locations. Additionally, the study highlighted the system's scalability to accommodate varying water volumes and its capability for in-line monitoring of treated water and scavenged H2S. This versatility allows real-time optimization of chemical loading, making the system a novel solution for H2S and oily produced water treatment. However, further research is necessary to optimize the system for different produced water streams and assess its long-term efficiency.