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Sewage solution

by Adam Dawson on Feb 28, 2007




Throughout the world water is becoming a precious commodity and no more so than in the Middle East today. Huge industrial growth coupled with a population increase means that the recycling of sewage is being looked into as a viable option for district cooling systems. The previously unconventional technology of membrane bio-reactors has recently been introduced to the UAE and the high standard of effluent this produces is being hailed as a way of doing it.

The Middle East may represent 5% of the world’s population, but it only has about 1% of its renewable fresh water. At present, around 70% of the UAE’s water comes from desalination plants and the Kingdom of Saudi Arabia is the world’s largest producer of desalinated water, with around 30% of the total global production. Demand in the Arab world is increasing at an annual growth rate of 6%, compared with the global average of 3%.

“We have little natural resources when it comes to water,” says Mohamad Mohd Saleh, director of water for the Federal Electricity & Water Authority (FEWA). “There are no regulations on the amount of water people use, so there must be more education on water use. People turn on the tap and the water is there. The next generation must know where this water is coming from,” adds Saleh.

The UAE produces enough water from desalination plants to meet its current industrial and population needs. However, using desalination plants is expensive and energy-intensive, and with a growing population and increasing industrial needs in the Emirates there are alternatives that need to be considered.

“It isn’t just water supply that we need to look at, it’s water reuse,” says Mohanned Awad, group marketing officer for water treatment company Concorde-Corodex Group. “We have treated sewage effluent, so what can we do with it? In some parts of the world like Singapore they are drinking the stuff. I’m not saying we should do that, but it should be used in some way. Water is precious in the region and with the current growth rate it is good to cut down the amount we rely on desalinated water.”

Concorde-Corodex is the first water treatment company in the region to make use of membrane bio-reactors (MBR) to allow domestic sewage to be treated and safely used for industrial application.

“There are advantages in using this type of technology,” states Awad. “There is a much smaller footprint compared to traditional technology and in Dubai, where land comes at a high premium, this is important.

Also, the quality of the effluent is high because you have a higher pathogen kill-off and the sludge production is very low.”

Concorde-Corodex has MBR sewage treatment plants on both the Jumeirah Palm and in International City, Dubai. The high quality effluent from the plants is being used for restricted landscape irrigation throughout the two areas.

“There are other applications that it can be used for,” adds Awad. “You can use this water for growing vegetables, for use in toilets and fountains and to wash your car, but you need to use it in conjunction with reverse osmosis technology. Putting it through a polishing plant produces an even higher level of treated sewage effluent.”

This high level of treated sewage is interesting for the region right now as it can be used in district cooling. “Many of the district cooling companies are looking into this,” says Bruce Dorey, director of McQuay International Middle East. “Using a higher level of polished water results in more efficiency within your plant and less build-up of scale and deposits. I think they’ll be using this technology within six months to a year.”

It may be a lot sooner. District cooling service provider Emicool has already approached Concorde-Corodex with the view to using their treated effluent. “Emicool not only want us to provide them with water,” says Awad.

“They want us to recycle 80-85% of their blowdown water as well. This is an holistic approach to water management. It’s forward-looking and it saves money as well,” Awad reports.

Concorde-Corodex has provided Emicool with a pilot plant and at the time of printing it was awaiting the results of a six week trial. General manager of Emicool, Fouad Younan says using this technology will save on costs. “We’re very excited about this new technology. We will save money if we can recycle the blowdown water, but at the same time cut down on our waste and it’s better for the environment.”

And it’s not just Emicool who are interested in the technology. Palm District Cooling has also expressed an interest in using the treated effluent. “We’re always looking for new technology that increases efficiency,” says md Sharif Khoori. “We aren’t using this technology yet but we are definitely looking into it. Within the next year we will be in a position to use it.”

Awad believes that there is a huge market for MBR technology within the region. “Private individuals and companies will start using these plants,” he says. “They won’t wait for the Dubai government to install them, and in using them they can cut down on their costs.”

The future seems bright for effluent treated in this way. And if water shortages continue, one day we may even be drinking it. That may be some way off, but for now, it seems that district cooling companies are more than happy to exploit the benefits of sewage treated through MBR technology.

Membrane bio-reactors: the technology

A membrane bio-reactor (MBR) is a suspended growth activated sludge system with a micro- or ultra-filtration membrane system that rejects particles and replaces the conventional arrangement of aeration tank, settling tank and filtration. The membranes are immersed within the aeration tank and bathed in the wastewater. A pump then draws the water through the ultra-filtration membranes, while intermittent airflow cleans the surface of the membranes.

As the pore openings on the membranes are generally in the range of 0.1-0.5µm they trap a significant proportion of pathogenic organisms, producing a high quality of effluent and meaning that there is less need for disinfectant.


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