Waste not, want not: The sewage system is getting some necessary upgrades

The collection, treatment and disposal of wastewater are important functions of developed economies. These responsibilities are handled by Abu Dhabi Sewerage Services Company (ADSSC), a government entity, but the private sector has taken a greater role of late, building and operating four new wastewater treatment plants. The government remains the primary player, with ADSSC overseeing the expansion of sewer tunnels.

SYSTEM STRUCTURE: ADSSC is the institution primarily responsible for sewerage systems in the emirate, with a mandate to collect and treat wastewater and safely dispose of the waste produced. It is entirely owned by the government and reports directly to the Executive Council, the emirate’s primary decision-making body. The organisation owns and operates more than 20 wastewater treatment plants in Abu Dhabi, with over 60% of the treated water generated by these facilities given to the emirate’s municipalities for irrigation.

The demand for sewerage services has accordingly expanded in recent years. To address the need for facilities, the government turned to the private sector in 2008, granting two 25-year concessions to build, own and operate independent sewerage treatment plants (ISTPs). The ISTP model is similar the one used for independent water and power projects (IWPPs) in Abu Dhabi, with 60% of the ISTP owned indirectly by the government and the balance held by private sector investors. However, unlike the emirate’s IWPPs, the ISTPs have been established on a build-own-operate and transfer basis, rather than the build-own-operate system that has been used in production.

Two entities – Al Etihad Biwater Waste Water and Al Wathba Veolia Besix Waste Water – were established using this new model. Each firm was awarded a concession to build two plants, for a total of four ISTPs, of which three had opened as of mid-2012. Al Etihad Biwater announced in January 2012 that it had inaugurated the operation of the Al Saad wastewater treatment plant, which has been designed to treat a maximum capacity of 80,000 cu metres of wastewater per day. Al Saad will be joined by Al Etihad Biwater’s plant at Al Wathba, which is in its final commissioning stage and will handle a daily maximum of 300,000 cu metres. Meanwhile, Al Wathba Veolia Besix launched two plants – Al Wathba 2 (maximum capacity of 300,000 cu metres per day) and Allahamah (130,000 cu metres) – in 2011.

STEP-BY-STEP: Abu Dhabi is also investing heavily in expanding sewer tunnels to treatment plants. At the centre of these plans is the Strategic Tunnel Enhancement Programme (STEP), which involves the construction of a 41-km tunnel that will start on Abu Dhabi Island and pass beneath the Maqta Creek to the mainland, descending from an initial depth of 24 metres to 80 metres. Along with a system of 43 km of smaller feeder tunnels that will carry wastewater to the main shaft, there will also be a large pumping station located next to the Al Wathba ISTPs. When completed, the $1.6bn network will be able to carry 800,000 cu metres of wastewater per day, with its capacity to be increased to 1.7m cu metres per day by 2030. Progress has been rapid so far, with Alan Thomson, the managing director of ADSSC, announcing in May 2012 that more than one-third of the development work on the tunnelling had been completed and the project was on schedule to be completed by early 2015. “The new STEP system will address current strains on the system and cater to future forecast growth,” Thomson told OBG. “Additionally, new treatment plants and pumping stations will help support the ongoing investment programme for the emirate’s wastewater network.”

REUSE: At present, ADSSC treats all water to a standard suitable for reuse in unrestricted landscaping applications. Only 60% of this is actually reused due to the inadequate capacity of downstream distribution infrastructure. To meet the institution’s objective of 100% re-use, ADSSC has embarked on a Dh2bn ($544.4m) investment in infrastructure expansion. Projections of recycled water demand show that it exceeds supply and that when the new developments are fully established ADSSC will have full reuse of treated water.