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Spanish water company uses reclaimed water to cope with extreme drought

Written by: Annabel Andrews | 19 September 2008

Climate change could see the problems Spain now faces with extreme drought mirrored in southern England. Annabel Andrews went to see how the Catalonians are coping.

Last summer, as the UK water industry was struggling to cope with too much water, its Catalonian counterpart in southern Spain faced the opposite problem. The region was in the midst of a two-year long drought, which caused water to be shipped in by boat as reservoir levels fell close to 15 per cent - the level at which the water becomes non-potable due to sediment. The drought continued until May this year, when heavy rainfall boosted reservoir levels to 52 per cent within two weeks.

To avoid such severe shortages in the future, the EMA-AMB, the water management organisation in the region's capital Barcelona, wants to see headroom - spare supply above demand - of at least 50 per cent. Currently, water resources of 627 million cubic metres (mcm) per year are just 13 per cent higher than the annual demand of 555 cubic hectometres.

Demand side
Martin Gullon, director of water services for the EMA-AMB, says it is adopting a twin-track approach to addressing the balance. Most of the demand-side measures have already been completed; Barcelona's per capita consumption is already one of the lowest in Europe, at 120 litres per person per day, thanks to low pressure at night, heavy fines for water wastage and media campaigning. Gullon predicts that network improvements will reduce demand by a further 5 mcm per year.
The rest must be met on the water resource side. The EMA-AMB is looking to desalination and water reuse plants to boost supply, as well as river transfers and other interconnections. A 60 mcm per year desalination plant is due to come on stream in 2009.

The Baix Llobregat water reclamation plant could provide 100 mcm per year, or nearly one fifth of the area's annual water demand, at full capacity. Output is growing every year, from 5.3 mcm in 2004 to 19.9 mcm in 2007. Projected total flow for 2008 is 30 mcm.

Reclamation plant
The reclamation plant takes secondary effluent from the El Prat de Llobregat wastewater treatment plant, which uses an activated sludge process and biological and chemical nutrient removal. The reclamation process was designed and commissioned by Veolia Water Solutions and Technologies and is based on the company's Actidisk process. The effluent first passes through ballasted coagulation-flocculation and lamella settling. This uses two-lines of Actiflo process, with added coagulant, sand particles and polyelectrolyte. After this it is filtered through two lines of five microscreen filters before UV disinfection. This is done by 1,600 lamps in four parallel rows. The plant keeps oxygen on site in a cryogenic tank, to ensure that water leaving for the plant for environmental uses has a dissolved concentration of oxygen above 7.4 milligrams per litre. This oxygen has not yet been required.

Currently, the only year-round use for the reclaimed water is to form a saline intrusion barrier for an aquifer under the Llobrogat delta. This water undergoes reverse osmosis after filtration and disinfection and is mixed with water from the domestic potable water supply network. This water is then injected into wells to the deep aquifer system, 55 metres below ground level.

The majority of the reclaimed water is used to maintain flow in the Llobregat river. Reclaimed water is pumped into the river just downstream of the abstraction point of the Sant Joan Despí water treatment plant. In the summer, 2 cubic metres per second will be used in this way. A further 0.4 cubic metres per second will be used to restore environmentally protected marshlands. These measures will enable the Sant Joan Despí to continue to abstract even during times of drought.

Farmers' abstraction
The Catalan Water Agency also wants to substitute 50 per cent of farmers' abstraction rights with reclaimed water. Farmers in the area have so far opposed the use of reclaimed water for irrigation purposes, claiming levels of dissolved minerals are too high and that international markets might reject produce grown using reclaimed waste water.
To address these concerns, the plant's owner, with the Catalan Water Agency, is constructing a two-phase electro dialysis reversal plant at a cost of €15.9 million to achieve the quality necessary for the crops commonly grown on the Llobregat Delta.
In an effort to change perceptions about reclaimed water, the Catalan Water Agency is currently devising a set of quality criteria for the different uses of reclaimed water based on accepted international standards.

Technically, the reclaimed water from the plant could be sent straight to a drinking water treatment plant and treated to a potable standard, as is done in Lesotho or Singapore. However, Frederic Certain, chief executive of Veolia Agua, says that Europe will not be "psychologically ready" to accept this for another 10 or 20 years.

Tags: Spain, water stress