Improving water treatment processes through chalk recrystallisation
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.
UNIVERSITY OF COPENHAGEN
Susan L. Svane STIPP (Dr)
Final Activity and Management Report Summary - RECRYST (Improving water treatment processes through chalk recrystallisation)
RECRYST has investigated the fundamental surface reactivity and environmental engineering utility of natural calcite (chalk) and bacterially precipitated calcite, and has demonstrated the utility of this mineral for enhancing the efficiency of toxic metal removal during water treatment processes, and solubility and mineral trapping during carbon capture and storage. This knowledge will contribute to enhancing the EU's ability to develop energy efficient, low carbon water and air treatment technologies through the 21st century for a long term environmentally sustainable future.
Deliverables not available
Publications not available