Case study: Reed bed effluent in Oman

Petroleum Development Oman produces nearly five barrels of water for every barrel of oil; a large part of its costs are water-associated. The produced water contains small amounts of salts and oil and is often pumped back into the well. Because re-injection can be very expensive, however, Shell is experimenting with reed bed technology to clean contaminated water for re-use as an alternative means of disposal.

The reed beds have proven capable of removing heavy metals from the water, while oil concentration has been reduced from 200-300ppm to 0-5ppm. As the water passes through the reed beds evaporation takes place, which increases the salinity of the water, so the effluent is being used for the cultivation of salt-resistant crops.

Given the large quantity of water that is handled in Oman, the use of reed beds has led to a process of treatment and reuse that is beneficial both to Petroleum Development Oman, through the reduction of cost and improvements in energy efficiency, and to the local community, who can now draw on this resource to develop new agriculture and generate wealth for themselves.

The Sultanate of Oman lies in one of the planet’s most arid regions. Annual precipitation is about 75-100mm (average annual rainfall over the UK is over 1,000mm), and there are no perennial streams. The balance between available water resources and water withdrawals is increasingly under threat from the growing demands of modern society and the economy.