Hydrocarbon Removal from Oilfield Produced Water

Heglig, Sudan

In 2003, Oceans-EWS partner, UK based Oceans-ESU Ltd, was commissioned by GNPOC to undertake the construction, management and maintenance of reed beds in Heglig, Sudan. The reed beds function as a means to clean produced water by biological treatment removing oil contamination.

Beginning in 2004 with a pilot system receiving 16,000m3 (increased to 40,000m)3 water per day, treatment capabilities and toxicology were extensively studied for 18 months by the Sudanese Commission for The Environment and Safety. The system was approved as the best environmentally friendly technique for removal and treatment of oil contamination from produced waters.

During the study, and continuing to the present day, treatment consistently achieved the required Sudanese Standard for Discharge to the Environment, with combined free and dissolved hydrocarbon contamination levels below detectable levels for almost all outlet samples. Final commissioning of the systems was completed during 2010, after a twoyear construction programme with total costs of approximately $250M.

In 2007, GNPOC, with technical consultancy from our partner firm, began a roll out implementation of this technology across the 41,600 km2 concession areas, predominantly at nine locations, adjacent to the oil gathering and processing facilities.

The treatment systems have not only ensured that GNPOC achieve compliance for discharge of vast quantities of treated water to surface waters, but also allowed local agencies to use this treated water to establish over 40 km2 of sustainable forestry, providing value crops and employment to the local community. In addition, the treatment systems have consistently proved to have no toxicological effect on the local environment, rather providing areas where biodiversity increases by 400% over areas that are greater than 2 km from the treatment sites. As well as re-establishing wetland habitats in

Sub-Saharan Africa, the systems host resident and migratory populations of four species that are on the IUCN red list of threatened species.

In 2011, under the system management of Oceans-ESU Ltd, the system successfully treated 41 million tonnes of contaminated water to a world class discharge standard. The reed bed treatment systems is comprised of settling lagoons and a series of engineered wetlands with a combined area of 6,400 ha. Bioremediation of produced water with reed bed technology has now been adopted in some form by all the oil operating companies in both republics of the former Sudan.

The Engineered Wetlands (reed bed proprietary system) are enabling continued sustainable produced water treatment/management for GNPOC’s oil production.

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