The Use of Reed-Bed Technology for Treating Oil-Production Waters in the Sultanate of Oman

Abstract

Abstract The safe and environmentally benign disposal of oil production water is of major concern in the Sultanate of Oman. Petroleum Development Oman (PDO) is currently producing 600,000 m3d-1, and the volume is predicted to rise to 900,000 m3d-1 by the year 2013. This water is contaminated with petroleum hydrocarbons (10-800 mg L-1), traces of phenols, emulsifiers and a wide range of metals at variable concentrations; it also shows a relatively high (12 dS m-1) electrical conductivity. The currently adopted methods of disposal into shallow and deep aquifers are no longer meeting the environmental legislation. In this study, the use of reed bed technology for the treatment of oil production water was evaluated and insights into its associated chemical and biological processes in contaminant removal are presented. This reed bed system is constructed in Nimr concesion site of PDO to treat 3000 m3 of production water per day. The results obtained demonstrated that inorganic and organic contaminant concentration was significantly reduced in the effluents. Metal concentration decreased by 78% for Al, Ba, Cr, Cu and Zn, up to 40% for Fe, Li, Mn, Pb, As, Cd, Co, Mo, Ni, Se, Tl and V. The total hydrocarbon concentration was reduced by an average of 96%. The removal mechanisms were attributed to the complex interactions between substrate, macrophytes and the associated microorganisms. Aerobic processes seem to dominate the system over the anaerobic ones in the removal of both groups of contaminants. In model pot experiments, a sandy loam soil matrix and a surface flow regime proved superior to a pure loam matrix with subsurface flow of Nimr. The latter modification may render existing reed bed decontamination sites even more effective.