(BAT) Reference Document for the Production of Chlor-alkali ...

Chapter 4
contaminated materials) [ 274, Ancery 2011 ], [ 276, French Ministry 2010 ]. Techniques to
remove mercury from waste gases include [ 1, Ullmann's 2006 ], [ 87, Euro Chlor 2006 ]:
adsorption on iodised or sulphurised activated carbon;
scrubbing with hypochlorite or chlorinated brine to form mercury(II) chloride;
adding chlorine to form dimercury dichloride (calomel) which is collected on a solid
substrate such as rock salt in a packed column.
Techniques to remove mercury from waste water will generally include a first settling stage to
remove large mercury droplets. For the second step, three options are generally employed
[ 91, Euro Chlor 2011 ]:
use of oxidising agents such as hypochlorite, chlorine or hydrogen peroxide to fully
convert mercury into its oxidised form with subsequent removal by ion-exchange resins.
The regeneration of the resins results in a liquid which requires further treatment;
use of oxidising agents such as hypochlorite, chlorine or hydrogen peroxide to fully
convert mercury into its oxidised form with subsequent precipitation as mercury
sulphide. The precipitate is treated as solid waste;
use of reducing agents such as hydrazine and hydroxylamine to fully convert mercury
into its elemental form with subsequent removal by sedimentation and filtration with
activated carbon.
Another technique which uses bacteria to reduce ionic mercury into metallic mercury before
adsorption on activated carbon was used by two plants in operation in 2011 [ 91, Euro Chlor
2011 ], [ 92, Gluszcz et al. 2007 ].
Laundry wash water arising from the cleaning of protective equipment is usually treated as
mercury-contaminated waste water [ 91, Euro Chlor 2011 ].
Depending on their conditions, buildings can be reused after decontamination. Experience has
shown that if the concrete is in good condition contamination is usually limited to the surface
layer. Decontamination can be achieved after removal of all equipment by cleaning the walls
followed by coating or painting to give them an impermeable surface. Renewal of non-structural
materials including the top layer of the concrete floor may be necessary. Furthermore, the
cleaning or, if necessary, renewal of the existing waste water collection systems in or around the
plant is usually carried out [ 94, Euro Chlor 2009 ].
The dismantling of the cell room at the Arkema plant in Saint Auban (France) was carried out in
the following sequence [ 276, French Ministry 2010 ]:
1) Dismantling of the concrete parts and segregation of the obtained gravel owing to the
mercury content;
2) Avoiding the production of dust by spraying water;
3) Dismantling of the building structure (in this order: beams, brick walls, concrete
foundation slab and finally roofing). Before dismantling the roof, a liner and a layer of
sand were installed to avoid a potential leaching.
WORKING DRAFT IN PROGRESS
Table 4.8 shows techniques which can be used to monitor mercury in air, water and waste.
166 December 2011 TB/EIPPCB/CAK_Draft_1