The Physical-Chemical Treatment of Sour Gas Plant Process Waste Waters
Authors: Zaidi S.A. , Tollefson E.L. 
Published: March 2010

The feasibility of physical-chemical treatment of sour gas plant aqueous wastes was studied on a laboratory scale. Experimental data on (a) the adsorption of organic pollutants on Culligan 1627-00 activated carbon, (b) the removal of sulphides from sulphur plant aqueous waste and (c) the chemical clarification of two aqueous waste streams are presented.

Initially, the adsorption by the carbon of major organic chemicals used in treating sour gas was studied. The concentrations of the dilute aqueous solutions of those chemicals were measured by a Beckman Total Carbon Analyzer, A four-hour contact period was found to be sufficient for equilibrium adsorption of the organics. The adsorption data are well represented by Freundlich isotherms,

Experimental data on the treatment of sour gas plant waste waters by physical-chemical methods indicate the need for (a) segregation of various waste streams and (b) a combination of inclination, steam stripping, clarification and activated carbon adsorption for the treatment and disposal of different streams. The data indicate that the incorporation of a proposed aqueous waste handling and treatment scheme, for a typical sour gas plant, will produce an aqueous effluent containing less than 10 mg/L of total organic carbon and less than 100 mg/L of chemical oxygen demand.

Treatment of the sour gas plant waste water samples by chlorine-ultraviolet oxidation and by ozonation does not appear to be capable of meeting the current waste quality standards.

Introduction

Sour gas treatments plants in Alberta are able to meet the recently established waste water quality standards largely because they are allowed to inject the process waste waters into subsurface strata(1).

However, concern about the long-term risks of waste water injection is growing and various governmental agencies in North America are weighing these long-term risks with the short-term gains(2, 3). It may become necessary for sour gas plants to demonstrate that the subsurface injection of aqueous wastes is the best disposal method in terms of over-all environmental protection. The EPA in the United States already has regulations of this type for industrial aqueous waste injection(2). To determine that subsurface injection of aqueous wastes would be least damaging environmentally, alternate aqueous waste treatment processes should be evaluated and the costs compared. A recent study by Milne and Tollefson(4), in which various alternative methods for the disposal or treatment of aqueous wastes from sour gas plants were evaluated, indicated that the necessary experimental data were not available in the literature and that any comparison of treatment methods had to be based on "guesstimates".

Recently, research has been undertaken in these laboratories to investigate the feasibility of "physical-chemical treatment" of aqueous wastes from sour gas plants. Synthetic systems were employed in the early phases of this research to generate equilibrium and kinetic data for the adsorption by activated carbon of some of the major organic compounds used in sour gas treating service in Alberta, Subsequently, waste water samples obtained from three sour gas treatment plants were used to determine the extent of adsorption of the organic components by activated carbon.