Dubai struggles to treat sewage

14 December 2007

Water treatment facilities buckle under demands of rapid population growth and development.

Contaminated water is being used in Dubai’s irrigation networks and discharged into Dubai Creek because treatment facilities cannot cope, Dubai Municipality has admitted.

The government body says it is failing to meet quality standards in wastewater treatment as it struggles to cope with rapidly growing volumes of sewage.

The problem has not gone unnoticed by Dubai’s residents, who have become aware of what one describes as “a mild sewagey smell”.

“People are starting to complain about the odour,” Aisha al-Abdooli, head of sewage treatment plants at Dubai Municipality, told MEED’s Wastewater Treatment & Reuse 2007 conference in Abu Dhabi on 10 December.

But the unpleasant smell is the least of Dubai’s problems. As it struggles to cope with higher sewage levels, concern is growing over the quality of the treated effluent being produced.

Dubai’s only existing wastewater treatment plant, at Al-Aweer, is operating well above its capacity, producing treated sewage effluent that falls below international standards. The plant, which was designed to treat 260,000 cubic metres a day (cm/d) of sewage, now treats 460,000 cm/d.

“We are operating at 70 per cent above our design capacity,” said Al-Abdooli.

Rapid population growth and development in Dubai has caught the municipality unprepared. Some 3,000 trucks each day deposit 100,000 cubic metres of raw sewage at Al-Aweer plant for treatment.

“We were expecting more than 15 per cent annual growth in inflow [of sewage],” said Al-Abdooli. “It is now probably 25 per cent.”

One indicator of the under-capacity of Dubai’s treatment services is biological oxygen demand (BOD), which measures the rate at which micro-organisms decomposing waste take up oxygen. In Dubai, the BOD is 154 tonnes a day (t/d) - almost double the design level of 75.4 t/d at Al-Aweer. High BOD levels indicate high levels of activity by bacteria, and therefore high quantities of organic waste in the water supply.

“The treated effluent quality is at times absolutely shocking,” says a water sector consultant. “The BOD levels are so high it is sometimes easy to believe it is raw effluent they are pumping back around the system.”

Insufficiently treated sewage can continue to harbour dangerous pathogens including E. coli and salmonella creating potential health risks.

The municipality says it has alerted the relevant authorities. Consultants and developers have long been aware of the issue and have started to put their own contingency measures in place. One international consultant tells MEED his company has prepared an internal report on the problem and will be advising clients to introduce additional treatment for the effluent from Al-Aweer.

“We need to tell our clients who ask for architectural lawns and grass areas that they need to buy additional treatment until Dubai brings new capacity online,” says the consultant.
The company is in talks with manufacturers of small-scale treatment plants.

Major developers are also planning wastewater treatment plants. A plant with a capacity of 25,000 cm/d is planned to serve Burj Dubai, which is already producing 3,000 cm/d of wastewater. The same is true of Jumeirah Golf Estates, International City, Palm Jumeirah and Sports City. The wastewater treated on site will be reused in cooling plants.

Dubai Electricity & Water Authority says it will no longer provide drinking water for cooling plants, so developers must use treated sewage effluent. Given the lack of capacity, the Dubai Municipality will be unable to supply this to all of the emirate’s megaprojects. Designated wastewater treatment plants will allow developers to circumvent the issue.

Several projects are under way to alleviate the wastewater problem. “They are looking at a number of short-term solutions,” said Al-Abdooli.

These include plans for a 65,000-cm/d aerated lagoon at Jebel Ali to receive sewage. Two membrane bioreactor plants, each with a capacity of 25,000 cm/d, are also planned.

In the long term, additional capacity will be installed. A 300,000-cm/d treatment plant, due to be commissioned in 2010, is under construction at Jebel Ali, and a 65,000-cm/d second expansion of the Al-Aweer plant will be completed in January 2008. A third-phase expansion of the plant, which would add capacity of 80,000 cm/d, is also being studied.

Dubai is not the only place in the Gulf facing a shortage in wastewater treatment capacity. Many countries in the region are experiencing up to 7 per cent population growth.

With wastewater treatment plants taking an average of two years to build, many existing plants in the region are operating above their design capacity. However the problem is more acute in Dubai, which is far ahead of its peers in terms of real estate development.

Working above capacity: Al-Aweer capacity increase since design

  • Flow: 77%

  • Biological oxygen demand: 104%

  • Ammonia: 64%

Source: Dubai Municipality

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