Harmful effects of desalination on the environment
Borja Montaño and Martin Sevilla
The environmental impact of desalination is threefold:
- The effect of returning the brine water to the sea.
- The effect of CO2 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.
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. 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 CO2 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/m3, 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’s 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 through renewable sources as necessary to compensate electricity consumption from the new AGUA program desalination plants.
 “Alternative 1, option 3”.