Our Company has successfully proven and used in the last years a regenerable weak anionic basic resin in the place of active carbons.
- By placing resins filters downstream of biological treatment plant a reduction of 20 - 50 % of C.O.D. and a great color removal are achieved.
- The regeneration is performed on - line either with soda at % 2 and sodium chloride at 10 %, so the expensive load and unload of active carbons for its regeneration are avoided. Sulphuric acid (2%) is dosed too in order to neutralize the alkaline effect of caustic soda on resins after regeneration.
- The operating cost of resins filtration is less than half in comparison with active carbons, even in the less favorable situation.
No effect is related to surfactants removal with above resins filtration.
The resins filters must be preceded by quartz filters to remove residual suspended solids. The choice of the washing system depends on the quantity of Chlorides in the final water with consequent use of caustic soda instead of sodium chloride. Often both are one by one used; also sulphuric acid at 2% concentration is dosed to neutralize alkalinity in the resins due to caustic soda use.
FILTRATION WITH RESINS
The second step of filtering process consists of a filtration through weak anionic resins.
Under construction point of view the filtration through weak anionic resins is similar to filtration through sand but with some differences.
The resins work like a sponge: is saturated with contaminants and then is “squeezed” through regeneration.