Muharraq Sewage Treatment Plant (STP), Bahrain


The Bahrain Ministry of Works' (MOW) Muharraq Sewage Treatment Plant (STP) project, located on reclaimed land in Bahrain, was completed in June 2014. The plant has a treatment capacity of 100,000m³/d. The project is overseen by the Muharraq STP Company as part of a 27-year build, own, operate and transfer (BOOT) scheme, the first scheme of its kind in the country.

The sewage treatment agreement (STA) for the privatisation of the project was awarded in February 2011. The groundbreaking ceremony for the project was held in July 2012.

The plant is designed to have a lifespan of 25 years and has a provision for future expansion to treat 160,000m3/d. The site covers an area of approximately 157,000m². The project won the Middle East Water / PPP Deal of the Year 2011 awarded by Project Finance Magazine.

Muharraq STP project details

"The plant is designed to have a lifespan of 25 years and has a provision for future expansion to treat 160,000m³ a day."

The project primarily involved the construction of the sewage treatment plant (STP), a deep gravity sewer (DGS) and network connections. The STP and DGS were completed in 2014, while the network connections were completed in 2014. The DGS is expected to have 80 years of service life.

The network connections intercept 24 existing pump stations and divert the flows to the deep gravity sewer pipeline. The deep gravity sewers further discharge the flows to the terminal lifting station built at the head of the new sewage treatment plant.

The deep gravity sewer is 16km-long and 1.8m in diameter. The sewer was tunnelled using the micro-tunnelling method.

The project also involved the construction of a lift station halfway through the route to lift the flow, further preventing the depth of the sewer from exceeding 15m below ground level.

A new sludge incinerator plant to treat the sludge from the sewage treatment plant was also installed. Treated sludge from the plant is used as fertilisers in agricultural fields. The STP also has an option to discharge the treated effluent and bypass flows to the sea through an outfall. By March 2013, the project achieved one million safe man-hours without lost-time incidents.

Sewage treatment plant technology

The treatment plant implements established technology, including pre-treatment, nutrient removal, filtration equipment implementing disc filter technology capable of capturing particles as small as ten microns, and disinfection using both UV and chlorine.

Contractors for the Muharraq STP's design and construction

The Muharraq STP Company comprises Samsung Engineering, Invest AD and United Utilities, which hold shares of 45%, 35% and 20% respectively. The joint venture between Samsung Engineering and United Utilities operates and maintains the facilities.

Hyder Consulting provided the detailed design services for the STP. The main construction contractor for the project was G P Zachariades. The company received the 2015 MEED Quality Awards and Best Subcontractor of the Month Award from Samsung Engineering in February 2013.

he installation of the piles for the shafts was carried out by Keller. The piles used for the shafts range in sizes from 12m to 18.5m. Implenia was sub-contracted to carry out the micro-tunnelling activities. The nutrient removal reactor for the plant was supplied by Siemens.

Financing Bahrain's Muharraq sewage treatment plant

The project financing for the treatment plant was completed in September 2011, with Macquarie Capital acting as the financial adviser and Ashurst acting as the legal adviser to the consortium.

"The network connections intercept 24 existing pump stations and divert the flows to the deep gravity sewer pipeline."

HSBC and Norton Rose, on the other hand, respectively acted as the financial advisor and legal advisor to the Bahrain Ministry of Works and Ministry of Finance.

The banks involved in the financing were Export-Import Bank of Korea (K-Exim), Credit Agricole, Natixis and Sumitomo Mitsui Banking Corporation (SMBC), while Shearman & Sterling acted as the advisor for these lenders.

The debt financing for the $325m project includes a $124m direct loan guarantee from K-Exim, an $83m guarantee covered by K-Exim and a $43m uncovered guarantee, with a 13.7% standby facility on each.

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