Connecting Waterpeople

Reclaiming polluted water: capacitive desalination

About the blog

ACCIONA
  • Reclaiming polluted water: capacitive desalination

Treatment of effluents from industries before discharge into the environment is a subject of concern today because of the disease burden it creates.

Among the pollutants of concern, metals and dissolved industrial chemicals are significant.

Though several treatment strategies have been used before, efficiency of pollutant removal still has a long way to go.

But among the prevailing pollution control strategies desalination holds the key in not only reclaiming polluted water but also in recovering important dissolved substances in water.

Desalination involves the removal of dissolved pollutants from water.

Solar desalination for instance uses the power of the sun’s heat to evaporate seawater in order to recover back condensed fresh water.

However, the salt concentrate left behind creates significant environmental challenges when discharged into the ocean.

Other desalination strategies such as reverse osmosis and ultra-filtration use significant amounts of power making them unlikely candidates for use in industrial effluent treatment.

Capacitive desalination

Capacitive desalination on the other hand is a water treatment strategy capable efficiently removing pollutants from polluted water while utilizing minimum energy.

The set-up of a capacitive desalination unit involves two carbon-based electrodes connected to a power source (see header image)

Polluted water is allowed to flow between these electrodes which end up attracting dissolved pollutants depending on their charges.

The cool thing with capacitive desalination (also known as capacitive deionization or CDI) is that it utilizes minimal power (less than 2 volts).

Though CDI is predominantly in its testing stages, its efficiency in removing key pollutants of concern has been successfully tested in several instances.

Fluoride

Fluoride contaminated water is a natural occurrence in many parts of the world leading to health conditions such as dental and skeletal fluorosis.

Though fluoride removal has been tried and tested using affordable materials such as bone based biochar, the removal efficiency has generally been low.

CDI promises greater efficiency in fluoride removal thereby safeguarding the health of the affected communities.

Toxic heavy metals

Being found in significant quantities in industrial effluents, toxic metals play a role in the promotion of diseases among affected communities.

CDI has been tried and tested to be very effective in targeting specific metals for removal from polluted water.

For example research has shown promising results in the removal of lead ions from polluted water.

Water hardness

Water hardness is a cause of concern in many places affected by high calcium and magnesium levels in underground rocks.

Water hardness renders water unpleasant to drink leading to many boreholes being abandoned.

CDI has shown a potential in the reduction of calcium salts in water helping in reducing hardness giving water a better taste.

Conclusion

Capacitive deionization shows potential not only as a pollution control strategy but also as a water treatment technique for use in domestic point-of-use systems.

However, it is also ripe for more R & D in order to make it robust, affordable and reliant on renewable energy to make it more sustainable.

Originally posted on John Mmbaga's blog

Comments