The Controlled Natural Attenuation (CNA) method of pollution treatment is an approach that uses natural contaminant degradation processes to clean up polluted sites. This method aims to accelerate the natural process of contaminant degradation by creating optimal environmental conditions for pollutant-degrading microorganisms.
The CNA process can be implemented on sites contaminated by petroleum products, solvents, pesticides, heavy metals or other organic and inorganic pollutants. It generally involves manipulating soil, groundwater or air conditions to promote the natural degradation of contaminants.
Techniques used in CNA may include injecting nutrients into the soil to stimulate the growth of degradative microorganisms, reducing oxygen supply to promote anaerobic degradation processes, or stimulating biodegradation by adding specific microorganisms.
CNA can be an effective approach to cleaning up polluted sites at low cost and with minimal intervention in the environment. However, this method requires a careful assessment of the polluted site, its geological and hydrogeological characteristics, and the properties of the contaminants present, before we can determine whether this approach is viable. It is important to note that CNA can take longer to completely clean up a site than other more aggressive methods such as excavation or remediation.
For in-situ remediation, other treatment methods can be used, such as biosparging, thermal desorption, dual-phase extraction, flushing, chemical oxidation, pump and skim, pump and treat, chemical reduction, sparging or venting.