THE ENVIRONMENTAL DAMAGE CAUSED BY DESALINATION

 

 

Unfortunately, experience has taught us that interaction between desalination

companies

 

 

, government and the general population will often have, at least, a partially

negative effect on the environment. This situation arises because, although environmental

welfare is important to the economic agents involved, certain short-term objectives are

considered more relevant (Montaño 2008). The question that we aim to answer in this

article is: why is some environmental damage resulting from desalination not avoided,

when it is technically feasible to do so? Our hypothesis prior to this article is that although

environmental welfare is viewed positively by the general population, companies and

government alike, all three attribute greater importance to other objectives

 

. This is the hypothesis we seek to contrast.

The current state of desalination in Spain

In recent years in Spain, the shortage of water resources has forced the country to

find solutions to provide access to water. With advances in technology, desalination has

become an economically viable way of increasing the amount of available water. With the

change of Government in 2004, the management of water resources underwent an

important change in Spain. The National Hydrology Plan was countermanded, and was

replaced by the AGUA program, a particularly relevant initiative in terms of sea-water

desalination (

 

Programa A.G.U.A In Alicante 2004).

Desalination methods in Spain and the rest of the world

There are two kinds of desalination – thermal or by membrane. Reverse osmosis is

the method currently used in Spain. This is a membrane-based system in which sea water

passes through semi-permeable membranes, overcoming the force of osmosis. The process

obtains two products: desalinated water, which after post-treatment is fit for human

consumption, and brine water, which due to its high salt content is returned to the sea. As

with electrodialysis and other membrane systems, reverse osmosis uses less power than the

thermal systems, which in Spain are highly expensive to run due to the amount of

electricity required. Thermal desalination methods first appeared at the end of the 1950s,

with membrane systems becoming more frequent by the end of the 1970s. Advances in

technology have focused on reverse osmosis and electrodialysis, and by the end of the

1990s membrane systems had surpassed thermal methods in terms of global capacity.

Harmful effects of desalination on the environment

The environmental impact of desalination is threefold:

– The effect of returning the brine water to the sea.

– The effect of CO

 

2 emissions resulting from power consumption.

– The visual impact of the desalination plant.

The possible negative effect of returning brine water to the sea is the most publicized

consequence of desalination, though as of 2008 its effects are not a cause for concern in

Spain, as investment to prevent environmental damage from brine has produced positive

results. Discretional returns to the sea of the brine produced during the desalination process

would increase the salinity of the sea water at the point of release, affecting the surrounding

ecosystem. On Spain’s Mediterranean coast,

 

Posidonia oceanica would be damaged, but

marine studies are carried out where the brine is to be returned to the sea to avoid this,

ensuring that the brine is dumped in desert areas where the salinity cannot harm these

algae. To dump the brine in these conditions, conduits often need to be built to avoid the

Posidonia fields, piping the brine into a safe area of the sea (Zarzo 2006) .Visual impact may be the kind of environmental damage that receives the least attention, due to the fact that the location of desalination plants has not led to any serious visual problems (Ministerio de Medio Ambiente 2006). However, the possible visual

impact requires efforts from both public and private bodies to optimize the location of these

plants. There are currently plans to build a plant in Mutxamel, which has led to a series of

problems in this regard, as the plant will be located in an area not on the coast, with an

intake of sea water from the dyke at the mouth of the Río Seco. This alternative

 

, which has

been studied by the Environment Ministry, prevents both the coastal area of the Serra

Gelada and the Serra Gelada nature park in Benidorm from being affected.

Regarding CO

 

2 emissions linked to desalination, it should be made clear that it is

 

not the desalination process itself that produces these emissions, but rather the power

 

consumption required for the process. As has occurred with the effects of the visual impact

and returning brine to the sea, there have been considerable improvements in recent years

with regard to power consumption. In 1990, power consumption for desalination was

around 8.5 kWh/m

 

3, whereas in 2004 this figure was down to around 3.8 kWh/m3. New energy recovery systems mean this rate can be reduced to 2.7 kWh/m3. If we suppose that desalination plants work at a power consumption rate of 3.5 kWh/m3, they emit 1.9 kg CO2/m3. CO2 emissions in desalination are highly affected by the country energy efficiency. In Spain, 51% of electricity is generated from heat sources. If the country were to convert to a system such as in France, where 73% of power is nuclear,emissions would be reduced by four, and if Spain converted to the Norwegian system, where 99% of energy has a hydroelectric source, CO2 emissions would be divided by 14.Therefore, desalination itself is not directly responsible for CO2 emissions; it is rather the power consumption involved, in both quantitative and qualitative terms. To reduce CO2 emissions, the current Ministry has committed to producing as much energy