* Big rise in use of water from sewers, drains seen -report
* N.American "Niagara" of treated wastewater flows into sea
By Environment Correspondent Alister Doyle
OSLO, Sept 5 The world is set to use far more
treated wastewater to help irrigate crops and feed a rising
population as fresh water supplies dry up, a team of U.N.-backed
experts said on Thursday.
A study led by Japan's Tottori University and U.N.
University's Canadian-based Institute for Water, Environment and
Health (UNU-INWEH) forecast "a rapid increase in the use of
treated wastewater for farming and other purposes worldwide".
It did not forecast volumes, saying that many nations lack
data on sewer and drain water. Of 181 nations studied, only 55
had information on wastewater generation, treatment and re-use.
Many governments and companies have so far overlooked the
economic potential of vast amounts of wastewater, UNU-INWEH
director, Zafar Adeel, said.
North America generates about 85 cubic km (20 cubic miles)
of wastewater every year, of which about 61 cubic km is treated,
roughly the amount flowing over Niagara Falls, and only four
percent of that is re-used.
Wastewater also often contained nutrients such as potash,
nitrogen and phosphorus which saved fertiliser costs, the study
published in the journal Agricultural Water Management said.
"Properly treated, wastewater is a huge economic resource,"
Adeel told Reuters.
However, many developing nations cannot afford the equipment
to treat wastewater even though recycling it can be cheaper in
the long term than pumping water from deep aquifers, the report
said, and, in Pakistan, like many other emerging economies,
large areas are irrigated with mostly untreated wastewater.
Per-Arne Malmqvist, an associate of the Stockholm
International Water Institute, said treatment costs were coming
down. Orange County in California found it cheaper to recycle
wastewater into drinking water than alternatives such as pumping
it from the distant Colorado River, he said.
"It costs a lot of energy to treat the water with membranes
but the technology is getting cheaper," he said.
Manzoor Qadir, an author of the study at UNU-INWEH, said
costs of treatment could be kept down according to purity - for
drinking water, for food crops or for crops such as biofuels.