Recycling is the future

Eagle Electromechanical's latest 25,000m? MBR plant is based in Dubai Sports City, part of the Dubailand complex.
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The challenge for the local authorities is to carefully look into areas where water reuse can be applicable. “In the UAE, specifically, the greatest challenge has been aligned with the expansion of the portfolio for effluent reuse,” says Eagle’s Hijaz. “We are liaising with local authorities, who are currently reshaping their guidelines, to diversify the reuse areas which were previously inaccessible. These include industrial re-use applications and non-potable urban uses, e.g. in fountains, lakes etc, amongst others.”

While some projects, such as that being constructed at Al Wathba in Abu Dhabi, are treating wastewater to irrigation quality for reuse, the question is being asked whether that is entirely viable. “Water treated to irrigation quality will not be directly suitable for use in many water reuse applications and restricts the reuse opportunities to use in irrigation only,” explains Robert Garner, lead design engineer at MWH.

“The question to raise therefore is whether treating wastewater to irrigation quality is the most ‘sustainable’ and valuable use of the treated water and whether we should be promoting schemes whereby non-native planting of roadsides and parks is consuming huge volumes of treated wastewater.”

One train of thought suggests that reused wastewater would be better utilised to accomplish reductions in potable water consumption, which requires a large amount of energy and generates large volumes of brine with chemical contaminates back into the sea. The requirement to use treated effluent for district cooling plants gives an immediate need to address the quality issues for treating effluent but also raises challenges in the handling of the reject from polishing plants and the blowdown from cooling schemes.

All of this amounts to some stiff decision-making for the local water authorities in the GCC. About the only issue that can be confirmed with certainty is that wastewater, despite its name, is far too valuable a resource to be thrown away. Of course, with financing becoming more of an issue in the current climate, the investment required to change regulations must also be kept to a minimum.

Surely at this stage, however, the strategy must be to focus on long-term planning. “By designing water infrastructure (specifically infrastructure to support non- potable water requirements) so that it could, in the future be segregated from the drinking water network, the potential to minimise the use of seawater desalinated water and maximise the re-use of wastewater can be realised,” indicates Ord. “While current irrigation requirements may consume all the available final effluent produced by a specific site, future wastewater treatment plant expansions may result in the production of excess effluent and at this point the advanced re-use system could be installed.”

Advanced re-use through RO technology could potentially reduce power demands – another key element in the electricity-hungry GCC – as well as increasing overall system sustainability. By preparing for its use within the network system at the design stage the advanced re-use system can be installed as and when it becomes financially and technically viable.

“We cannot be a wasteful society in terms of letting this valuable resource slip through our fingers and on the other end of the spectrum we should not be over-designing treatment systems,” says Eagle’s Hijaz.

As demand for water increases, the demand for advanced reuse systems will continue, which, in an ideal world, should enable the region to benefit from a balanced desalination and advanced effluent reuse network.

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Project focus: Jebel Ali STP

Client: Dubai Municipality
Capital value: US $300 million (estimated for Stage 1)
In 2007, MWH Global – which designed Dubai’s first STP in the 1970s - won the preliminary study, detailed design and construction supervision contract for the Jebel Ali STP. The plant is planned to be one of the largest in the world, serving an ultimate population of 4.5 million. Residual biosolids will be converted into a dried pellet product, which will be suitable for use as a large-scale fertiliser.

“Jebel Ali STP will treat the wastewater from Dubai’s rapidly developing new housing and industrial areas and provide irrigation water for the large scale beautification of the city,” says Robert Garner, MWH Global’s lead design engineer. “The STP will be designed and built in four stages, with each stage serving an equivalent population of 1.1 million people and an ADWF of 300ML/d (0.3m m³/d). The first module is under commissioning in 2009.”

Company focus: Eagle’s project list

Masdar Waste Water Treatment 500 m³/day (3 MBR modules)
Knowledge Village Universities 5,000 m³/day and 1,800 m³/day (sequential batch reactor)
Dubai Studio City 1,300m³/day (MBR)
Dubai Bio Technology 2,000 m³/day (MBR)
International Media Production Zone 4,000 m³/day (MBR)
Al Quoz Land Development STP – Phase II 7,500 m³/day (MBR)
Mina Al Arab Phase I – Infrastructure 6,500 m³/day (MBR)
Gardens 30,000m³/day (EA)
Dubai Motor City 8,000 m³/day (MBR) and Dubai Sports City 25,000 m³/day (MBR)
JAFZA 8,000 m³/day and 1,000 MBR m³/day (BOOT)

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