The effect of Hydrogen sulfide oxidation with ultraviolet light and aeration on sour water treatment via membrane contactors

Abstract

During natural gas extraction and production, hydrogen sulfide (H2S) is often brought to the surface. In some cases, H2S could be present in water streams, referred to as “sour water”, treatment of that sour water is required before disposal or reuse. Sour water can be treated in a variety of ways including conventional stripping and chemical scavenging. Hydrophobic membrane contactors are an alternative technology for the treatment of sour water. Due to the hydrophobic nature of the membrane, dissolved gases, including H2S, can pass through while water is retained on the feed side. The sodium hydroxide receiving solution acts as a trap that captures the H2S. Once the H2S is trapped, ultraviolet (UV) light and oxygen can be applied to oxidize the sulfide to non-hazardous forms of sulfur allowing more disposal options for the receiving solution. This research focused on evaluating the feasibility and performance of a hybrid process combining a membrane contactor and a sulfide oxidation step through UV light and aeration.Oxidation experiments showed that UV light alone can oxidize the sulfide to disulfide. On the other hand, UV combined with oxygen, via aeration, was capable of further oxidizing sulfide to sulfate and thiosulfate; the two main sulfur species present in the treated water based on mass balance calculations. Both oxidation methods (UV with and without aeration) were found to follow a first order reaction rate, that of UV alone was 0.015 min−1, and when combined with aeration the rate was more than two times higher (0.035 min−1). The proposed hybrid technology can be applied in both upstream and downstream operations as a standalone process for the treatment of sour produced and process water.