The international Minamata Convention on Mercury1 signed by France in 2013 decrees the curtailment of the production and use of mercury, along with a reduction in its content in emissions into the air and waste discharged into water and soil. This mercury – derived from a wide variety of sources, including dental amalgams, batteries and energy-saving lamps – must therefore be collected and treated.
There are two treatment options available to date: purification and neutralization. Purification is carried out using conventional distillation methods, under draconian impermeability conditions to prevent any leaks. This yields mercury purified to 99.9999%, which can be reused for industrial applications.
Neutralization makes it possible to transform mercury into a mercury salt, which is less toxic than the metallic form.
“We have invented and patented a mercury stabilization process,” states Thierry Gosset, Sarpi’s Technical Director. “By adding sulfur residues to the liquid mercury, we obtain mercury sulfide, similar to what we find in natural rock. It can then be stocked in salt mines in Germany.”
Despite increasingly better organized collections, non-hazardous waste containing mercury is regularly incinerated. Some mercury is therefore found in its combustion fumes. “These mercury emissions are now measured four times a year, but European regulations will soon require continuous measurement,” explains Thierry Gosset. “We will then become aware of the existence of occasional mercury emissions beyond the limits.
We have therefore developed a system for continually treating mercury in the incinerators.” Its principle: as soon as an increase in mercury in the fumes is measured, bromine-based chemicals that oxidize mercury are injected. This oxidized mercury is then captured by activated carbon. Veolia today applies this process to its own incinerators, and has begun marketing it in Europe.
1 http://www.mercuryconvention.org/Portals/11/documents/Booklets/1400281_F_WEB.pdf
1,960 metric tons* of mercury were emitted in 2010 due to human activity, over 60% of which was from gold panning and coal combustion (UNEP, Global Mercury Assessment 2013).
5 micrograms of mercury per kilogram of body weight (height/weight ratio for humans): this is the provisional tolerable weekly dose set by the World Health Organization (WHO).
Sarpi: a unique expertise
Mercury waste is collected from battery and lamp drop-off points used by European consumers and from dentists. Then Veolia, through its subsidiary Sarpi, treats this mercury in its Wimmis (Switzerland) factory in the strictest compliance with environmental and safety rules. Part of the mercury treated is purified and reused in industry; the other part is neutralized and stocked in secure salt mines. The mercury that escapes this collection and ends up in waste may also be treated: Sarpi retrieves it from the very heart of the incinerators using a new patented technology.
