Reed-Bed Technology for Treating Oil- Production Water in the Sultanate of Oman

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 98548, "The Use of Reed-Bed Technology for Treating Oil-Production Waters in the Sultanate of Oman," by A. Al Mahruki, Sultan Qaboos U.; B. Alloway, U. of Reading; and H. Patzelt, Sultan Qaboos U., prepared for the 2006 SPE International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Abu Dhabi, UAE, 2–4 April. Safe and environmentally benign disposal of produced water is a major concern in the Sultanate of Oman. Petroleum Development Oman (PDO) produces 600 000 m3/d of water, which is contaminated with petroleum hydrocarbons (10 to 800 mg/L), traces of phenols, emulsifiers, and a wide range of metals at varying concentrations. It also shows a relatively high electrical conductivity. The current methods of disposal into shallow and deep aquifers are no longer meeting environmental regulations. The use of reed-bed technology for the treatment of produced water significantly reduced organic- and inorganic-contaminant concentration in the effluents. Introduction Oil production in Oman is associated with large volumes of water, termed oil-production water (OPW), and the water/oil ratio can be as high as 1:6 after preliminary separation. The volume of water produced by PDO is predicted to rise to 900 000 m3/d by 2013. Only 40% of the OPW is used to maintain reservoir pressure by injection, while the remainder is disposed of into shallow and deep aquifers. Over the last 3 decades, these methods of disposal became progressively unacceptable for various environmental reasons. A major concern was the possibility of contaminating the groundwater resources with toxic organic and inorganic contaminants. PDO's environmental policy is to invest in research projects aimed at better use of the OPW. Water-treatment and reuse plans were developed, driven by the concept of "greening the desert" by use of reed beds to treat the OPW. Reed-Bed Biotechnology There has been increasing interest in environmental biotechnologies because of their potential in removing organic and inorganic contaminants from soil, water, and waste water. For instance, reed beds are used to treat water, waste water, and effluent from different sources including household, agricultural, industrial, and mining effluents contaminated with toxic organic contaminants and heavy metals. Recent literature on phytoremediation discussed the interaction between the soil matrix, plants, and microbial population that brings about many processes responsible for cleanup of contaminants including phytoextraction, phytostabilization, rhizofiltration, and phytovolatilization. Materials and Methods A large-scale reed-bed system was set up in Nimr, in south Oman. It comprised eight beds, with each reed bed being 75×48 m (3600 m2). Each line of four reed beds is called a train and is expected to treat 1500 m3/d after the reed beds have matured. Initially, two trains were constructed (Train A and B) to treat 3000 m3/d with gradual expansion to 170 000 m3/d.