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Improving water treatment processes through chalk recrystallisation

Improving water treatment processes through chalk recrystallisation

Objective

Calcite (CaCO3) plays a role in many public and industrial regimes that are critical for the health and economic well-being of society, but in many cases, a lack of understanding of the fundamental physical and chemical properties controlling calcite growth and dissolution translates to direct problems or to inefficiency in water treatment processes.

A common method for removing toxic trace-metal contamination during water treatment is to add lime (Ca(OH)2 or CaO). Trace metals are trapped in growing calcite as Ca combines with CO3 from the water.

However, production of lime requires burning of calcite, often in the form of limestone or chalk. This emits CO2, and though some CO2 is consumed during water treatment, considerable energy is required for lime production, which also contributes to the atmospheric carbon load. If a method could be developed to treat water directly with natural calcite, without first converting it to lime, considerable energy could be saved and CO2 emissions could be reduced.

We will investigate methods to alter the surface properties of chalk, to make it more effective at trapping trace metals. Our approach is to promote Ostwald ripening, the natural process where small particles dissolve to provide material for growth of larger particles. The growing calcite traps trace-metals, removing them from the water. To achieve this, we will apply nano-technological methods for characterising particle surfaces and use a bio-technological approach to develop environmentally friendly enzymes that can degrade the organic coatings on chalk particles, which are known to inhibit natural recrystallisation.

The Science and Technology results will lead to improved treatment processes for clean drinking water, and a decreased need for lime production with less consequent emissions of CO2, thus significantly improving energy efficiency and environment sustainability.

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Coordinator

UNIVERSITY OF COPENHAGEN

Address

NØRregade 10
Copenhagen K

Denmark

Administrative Contact

Susan L. Svane STIPP (Dr)

Project information

Grant agreement ID: 41374

  • Start date

    1 August 2008

  • End date

    31 July 2010

Funded under:

FP6-MOBILITY

Coordinated by:

UNIVERSITY OF COPENHAGEN

Denmark