These case studies show how treated sewage effluent can be used to replace costly desalinated water in non-potable applications in the Middle East
Abu Dhabi is a regional pioneer in recycling wastewater and is now expanding its infrastructure to maximise use of its treated effluent
When Abu Dhabi opted to use treated wastewater for irrigation in the early 1980s, it was at the forefront of the sustainability movement. Its 104,000 cubic-metre-a-day (cm/d) treatment facility at Mafraq used tertiary processes, such as sand filters and chlorination, to create a high-quality effluent that could be used to irrigate the emirate’s green spaces. But even back in the 1980s, not all of the water was utilised and this situation remains a challenge for stakeholders responsible for Abu Dhabi’s water and wastewater management.
AED1bn ($272m) is being invested in the pipe network to improve transmission of Abu Dhabi’s treated effluent
Today, the emirate’s wastewater works have grown in line with its expanding population. The Mafraq facility now has a capacity of 390,000 cm/d. Abu Dhabi treats more than 500,000 cm/d of wastewater to a standard that makes it appropriate for reuse in irrigation. About 60 per cent of this is used to irrigate the green spaces of Abu Dhabi island and mainland, with the remainder being discharged into the Musaffah Channel. But given the scarcity of water and reliance on desalination for drinking water, the government wants to use it all.
Treating the water to the required standard, however, is just the first step for the various authorities involved in water reuse. Abu Dhabi Sewerage Services Company (ADSSC) is responsible for the collection and treatment of wastewater, before delivering the treated effluent to a series of reservoirs managed by the Abu Dhabi municipality. The municipality then distributes the water around the city.
Constraints in both transmission and distribution networks are preventing the emirate from meeting demand for treated effluent. To address this, AED1bn ($272m) is currently being invested in the pipe network to improve transmission. A series of major pipelines up to 1.6 metres in diameter will be completed by the second quarter of 2013, ADSSC tells MEED.
This is good news for developers queuing up to receive the water. ADSSC estimates that up to 100 groups are interested in acquiring Abu Dhabi’s high quality effluent, prompted by a legislative change several years ago. Until 2008, Law 17 of 2005, which established ADSSC, stated that all recycled water had to go directly to the municipality.
Law 12 of 2008 amended the existing legislation to allow ADSSC to sell the treated effluent openly. Planners in ADSSC estimate that demand for treated effluent now exceeds the volume produced, and in the future, demand will outstrip availability, with 800,000 cm/d produced in 2016 against demand for more than 1 million cm/d.
Although ADSSC is now legally permitted to sell water directly to customers, the municipality remains responsible for the distribution network. To address this institutional mismatch, the Regulation and Supervision Bureau is working on establishing new arrangements. This could see a single firm take control of all recycled water distribution and transmission assets, and supply it to developers and the city.
Alternatively, an existing entity, such as Abu Dhabi Water & Electricity Authority (Adwea) or ADSSC, could be given the additional distribution responsibilities.
Another aspect to be considered is the potential to charge for the recycled wastewater, currently supplied free of cost. In some areas of the city, potable water is used for irrigation at a considerable cost to private users. Paying much less for treated effluent would be an attractive alternative, but suitable infrastructure has to be in place before this becomes possible.
Some developers are keen to use recycled wastewater to service district cooling networks, but this sounds easier than it is. Groundwater infiltration into networks is prevalent and the incoming flows tend to be highly saline. As the current treatment system does not include reverse osmosis or any other saline removal process, developers undertaking district cooling would have to complete these processes before the water would be useable.
In 2009, ADSSC investigated the possibility of putting all wastewater through a four-stage cleaning regime that would involve extensive filtration and reverse osmosis. An official decision has yet to be made on the future strategy, but MEED understands that the findings do not lean towards implementing the technology.
Decision-makers are concerned that reverse osmosis would eliminate nutrients, such as phosphates and nitrates, which make the water suitable for irrigation. At the same time, the capital and operations expenditure would be considerable. Another unwelcome side-effect is the creation of a brine stream that would have to be deposited into the sea.
Abu Dhabi’s wastewater could be used to irrigate crops, but there are complications that make this strategy unlikely. The distance the water would need to be pumped, additional treatment that might be required to irrigate certain products and the fact that the potential contribution of recycled water would cover a small fraction of total agricultural water demand are all deterrents.
A 2010 study by the Dubai-based International Centre for Bio-Saline Agriculture recommends that Abu Dhabi use its treated effluent locally to meet the city’s demand, rather than sending it out to agricultural areas.
Looking ahead, Abu Dhabi has many challenges to overcome in order to maximise water recycling, but the good news is that all of these are being addressed. The emirate has the will and the financial ability to implement the necessary changes to maximise the potential of reuse, which in the water-scarce Middle East is a welcome scenario.
Industrial reuse at Al-Ain dairy
Reducing its water footprint is a priority for Al-Ain Dairy, which recently invested $1.6m in wastewater recycling technology
A dairy farm in the desert seems an unlikely candidate to win accolades for its water recycling efforts, but that is what is happening at Al-Ain Dairy.
This month, the partly government-owned business, which was established in 1981, will inaugurate its latest water recycling facility, which will use advanced techniques such as ultra-filtration and reverse osmosis. The clean water will then be used to spray down the cattle and keep them cool, as well as for cleaning, irrigation and maintenance. It will not be used in food production, however.
“The business of cow farming and dairy production is a capital-intensive one and since water is a vital component of food production, high water usage is a concern,” says Shashi Menon, chief operating officer of the dairy. “In addition, the dairy industry is generally regarded as a polluter of groundwater resources. With the existing plant it created in 2005, Al-Ain Dairy believed that it could and should be doing much more to lower environmental impact and not just focus on conserving water.”
The investment at the dairy will see the new wastewater treatment plant process 700 cm/d of water from farming activities using ultra-filtration and reverse osmosis. Commissioning of the plant is currently under way. The existing plant will continue to treat up to 1,200 cm/d of water from the factory, offices and accommodation.
France’s Veolia Water Solutions and Technologies was the design and build contractor for the project, with processing systems provided by the US’ Dow Water & Process Solutions. The client’s designer was the UK’s Hyder Consulting.
Municipal and Industrial reuse under public-private partnership
Sourcing water from wastewater treatment works instead of desalination plants could be a future strategy for the region
Terneuzen in the Netherlands is home to US-based Dow Chemical Company’s second-largest facility globally. Here, Dow’s crackers break down naphtha and liquid petroleum gas into ethylene, propylene, butadiene and benzene for use in the creation of plastics and chemicals. These plants require a lot of water to operate, and since 2007 Dow has been sourcing this from the local municipal wastewater plant under a public-private partnership (PPP) arrangement. This is a strategy that it wants to implement in the Middle East.
“By 2007, we started receiving 10,000 cm/d of treated wastewater; 70 per cent of this is further treated onsite to generate the steam needed in the production process,” says Ilham Kadri, commercial manager for Europe, the Middle East and Africa at Dow Water & Process Solutions. “It is subsequently used as feedwater for the cooling tower and evaporated.”
The Zeeland area that hosts the chemical plant is a water-scarce site so the benefits of reuse were attractive to the local water authority, Waterschap Zeeuws-Vlaanderen. Reusing the local community’s treated wastewater twice, first in manufacturing plants and then again in cooling towers, ensures every litre of water is used three times instead of once. According to Dow, this process reduces the energy use for water purification by 65 per cent and reduces carbon dioxide emissions by 5,000 tonnes a year.
For companies considering this approach, Kadri says that water quality concerns should not hinder reuse. “There are some industries that may feel water quality is an issue, but if Dow can do it in the Netherlands, I believe that we can do it in the Middle East as well.”