International contractors will be invited to submit bids for a project to raise capacity at the Choutrana plant to 150,000 cubic metres a day (cm/d) from 110,000 cm/d. A tender will also be issued for the addition of 40,000 cm/d of capacity to the 80,000-cm/d plant at Sud Meliane. The Jeddah-based Islamic Development Bank is to provide $42.7 million towards the expansion of the two plants.

ONAS had previously considered amalgamating the operations of the Sud Meliane plant with the proposed new facility at Tunis West, which was to be carried out on a build-operate-transfer (BOT) basis. 'The Tunis West project is on hold,' ONAS president Mehrez Becheikh told MEED. 'The government has yet to take a decision on the plant, but we are still studying the possibility of carrying out a BOT wastewater project'.

Wastewater capacity in Tunis is becoming increasingly stretched as the capital's population grows. Without the addition of new or expanded plants there will be a capacity shortfall by 2006. 'We will definitely have to construct more treatment stations in the west of the city,' said Becheikh. 'An additional 100,000 cm/d is needed. This will most probably take the form of either two 50,000-cm/d plants, or three plants - one with capacity of 10,000 cm/d and the two others with capacity of 40,000 cm/d each.'

Over the course of the government's 2006-10 five-year plan, ONAS is committed to building a total of 30 treatment plants to serve some of Tunisia's rural villages. The plants will be part-financed by the European Investment Bank.