x Abu Dhabi, UAETuesday 25 July 2017

Garden thrives on recycled bathwater

A Dubai family has found a green way to keep their property that colour - recycling household effluent.

Adele Nigrini maintains her garden with waste water cleaned by her own recycling system, below.
Adele Nigrini maintains her garden with waste water cleaned by her own recycling system, below.

If all villa owners were like Adele Nigrini and her husband, Michel, the UAE would be well on the way to reversing its soaring water use. Figures from the Environment Agency-Abu Dhabi (EAD), show that in the largest emirate the average consumption of water per head is 550 litres a day, among the highest in the world - a statistic confirmed this week by a YouGov survey conducted for The National.

Agency data show that private gardens are responsible for a significant part of that consumption. It is the same story in Dubai, where the use of fresh desalinated water in gardening is regularly criticised by the Dubai Water and Electricity Authority. But not in Mrs Nigrini's garden, a substantial plot of more than 1,000 square metres sustaining mulberry trees, limes, a date palm, fig tree, banana trees, grape vines and even some sugar cane.

In winter, the family also enjoys a harvest of tomatoes as well as fresh herbs, including mint, basil and dill. Remarkably, just over half the water the garden needs comes from the family's waste water, recycled by a small-scale unit that harnesses the power of nature to clean it up. Her husband says the water initiative was born out of exclusively selfless motives - but it came to him, he said, after the family of five faced a utility bill of Dh17,000 (US$4,630) within a month of moving into their four-bedroom villa in Dubai.

"It was due to a leak that was not our fault, but in the end we had to pay. That to me was a wake-up call that I had to do something dramatic to reduce our water use." The idea chimed in with the family's feelings about sustainable living: "To me, this is the right thing to do in the first place, so I was looking to do it regardless," said the airline pilot. "It makes no sense to misuse water in the desert."

In most homes in the UAE, the outflow from sinks, showers, washing machines and lavatories goes down the pipes and is processed at large municipal treatment plants. In the Nigrini household, however, the waste water is routed instead to three tanks in the garden, where the heavier particles settle as sludge. The remainder is drawn off into a 15sq m patch known as a "constructed wetland". Enter Phragmites communis, aka the common reed, a plant that grows in marshes and lagoons all over the world. A subspecies even has a toehold in some wadis in the UAE.

For the Nigrini family, the common reed performs the uncommon task of filtering the water until it is fit to use for irrigation. "The most important thing is that we use the power of nature," said Wolfgang Sievert, an engineer with Waagner Biro Gulf, the Dubai company that designed and installed the system. "All is done by the bacteria which live on the roots of the reeds. These bacteria consume the organic pollution in waste water."

The end-product is safe for use, regardless of what type of cleaning agents are used in the household. "We advise people to use environmentally friendly cleaning products but there is no concern about the water quality even if conventional ones are used," said Mr Sievert. "These systems are also used to clean up industrial waste water." The system has now been at work in the garden for over two years and has helped to slash the family's utility bills. While neighbours pay up to Dh4,000 over the summer, Mrs Nigrini's bills are no more than Dh2,000.

Although, at about Dh30,000, the system cost almost as much as a small car, it pays for itself in three years, which means the family will break even on their investment in about six months. And the environment, of course, has been benefiting from day one. Waagner Biro Gulf has installed similar constructed wetlands for 15 clients in the UAE, said Peter Neuschaefer, the company's director of water, energy and environment technologies.

He believes the concept could soon become more popular, but one hurdle was the huge investment in large sewage treatment plants, which was putting pressure on authorities to maintain a centralised approach. However, data published in March in the Abu Dhabi Water Resources Master Plan showed that addressing the large water footprint of the nation's villas is key for any attempt to lower the nation's overall water consumption.

Abu Dhabi's average of 550 litres per person per day varies significantly, depending on where the person lives, says the master plan. Those who live in flats consume only between 170 and 200 litres, comparable to the average in developing countries of 150 to 250 litres. The range for those who live in villas, however, is far wider, varying from 270 to 1,760 litres per person per day. "This is because there are many green areas and plantations within private houses," said Dr Mohammed Dawoud, manager of the natural resources department at the EAD.

A lot of water is also used in swimming pools and for washing cars. At the present rate the emirate's existing desalination capacity will be unable to meet demand after 2012. Another factor is that desalination plants use vast amounts of energy. Habiba al Marashi, chairwoman of the Dubai-based Emirates Environmental Group, believes people will continue wasting water until they are made to realise the enormous economic and environmental implications of such profligacy.

"If people are aware of the costs and consequences of producing a single drop of water in the country, they will think twice in the way they consume it," she said. All the experts agree that there is really only one solution to the problem of wanton water usage: financial disincentive. In Abu Dhabi, for example, Emiratis are not charged for their water use at all, while expatriates pay only around 40 per cent of the cost, according to Dr Dawoud.

Leon Awerbuch, president of Leading Edge Technologies, a US desalination company with a number of projects in the region, said: "Subsidisation causes inefficiency and overconsumption. Demand is much higher than it should be." Mrs al Marashi agreed: "People and industries should pay for their actual water consumption based on a payment structure to be imposed by the Government." Last year, the Dubai Electricity and Water Authority (Dewa) introduced sliding charges related to volume, but it is not yet clear what impact the scheme has had on consumption.

Sources say a plan to increase water charges in Abu Dhabi, put forward by the Regulation and Supervision Bureau, has been postponed out of concern about public reaction. The Government has chosen first to work on increasing public awareness of the need to conserve water. vtodorova@thenational.ae