Study Results

Water reuse for irrigation, especially for food production, is central to the Emirate of Abu Dhabi’s strategy to increase food security and food self-sufficiency. It is also central to its integrated water resource management plans, which include an ambitious target to reach zero discharge of recycled water into the environment by 2020. To this end, in 2016, the Abu Dhabi government approved two mega projects to reuse 55% of treated water, which was being discharged into the environment. These projects, which include the completion of the required transmission and distribution networks and pumping stations for the recycled water to reach end-users, started in 2020 with an expected completion date of August 2022 and an investment cost of almost USD 0.3 billion. The works had originally been scheduled to be completed by 2020 but were delayed due to the COVID-19 pandemic. In addition to the 105,000 m3 /day of recycled water from Al Wathbah-2 WWTP currently used for irrigating landscaped areas and green spaces around local amenities, there is significant potential for its use in agricultural irrigation that could contribute to both food and environmental strategies. In 2014, 185 farms were supplied with 27,000 m3 /day of recycled water from the plant. By August 2022, it was anticipated that an additional 390,000 m3 /day of recycled water from Al Wathbah-1 and -2 WWTPs will be used to irrigate 4,200 farms, with half of this recycled water coming from Al Wathbah-2 WWTP (Dawoud 2017) (Figure 8.4). In environmental terms, a preliminary assessment by the Department of Energy (DOE) found that aquifer recharge using recycled water from the plant could also be used as a means to enhance the quality of brackish groundwater and that excess irrigation wastewater during non-peak seasons could be recharged to the aquifer system to be used later. A big advantage of aquifer recharge using recycled water from wastewater treatment plants is that it breaks the pipe-to-pipe connection of direct reuse. This reuse project will make a significant contribution toward replacing the use of desalinated water by 125,000 m3 /day and the costs of maintaining and operating more than 1,000 groundwater wells. The Emirate of Abu Dhabi is witnessing one of the fastest-growing populations and economies in the world, with a projected population of almost 7 million by 2030. The government needed to take action to ensure its wastewater infrastructure needs are met now and in the future. Although the old Al Mafraq WWTP had been continuously upgraded over its history, including an upgrade in capacity to 260,625 m3 /day in 1997 and new systems for odor control and biosolids management, it became overloaded, leading to raw wastewater discharge into the environment and inefficient treatment of the collected volumes of wastewater. The construction of Al Wathbah-2 WWTP was part of planned activities carried out in the Emirate of Abu Dhabi between 2010 and 2013 to serve the wastewater needs of 3 million inhabitants. Al Wathbah-2 WWTP is already providing socio-economic, health and environmental benefits including reduced discharge of raw sewage water to the environment, fewer odors and improved biosolids management. Raw sewage discharge has negative health and environmental impacts. The quality of the treated wastewater has improved increasing its reuse potential as irrigation water for both green and landscaped areas and for agricultural areas to replace the present use of desalinated water. This is saving USD 2.77 (AED 10.2)/m3 of desalinated water and reduces energy consumption, which is also minimizing carbon emissions from the desalination plants. It is also more costefficient. Recycled water costs USD 0.051 (AED 1.9)/m3 compared with expensive desalinated water. Using recycled water from Al Wathbah-2 WWTP is also helping to improve and enhance deteriorated groundwater quality and increase reserves for future uses. By April 2022, it is expected that 4,200 farms will be irrigated with reused water, which will replace about 250,000 m3 /day of brackish groundwater farms. In addition, the total dry mass of biosolids produced at the plant will be recycled for producing compost. In 2020 this amounted to 13,859 t.