Water Treatment

TOC/Color removal

TOC = Total Organic Carbon.

All surface waters contain varying amounts of naturally occurring organic acids. The most commonly encountered being tannic and humic. These substances have varying molecular weights and varying amounts of carboxylic functionality. There has been much interest in the removal of these substances from drinking water supplies due to their tendency to form THM's when chlorinated. They can be removed effectively by use of anion exchange resins operated in the chloride form. Because the organics can be removed by regeneration with brine, this technology is far most economical. 
The resin requires periodic cleaning with caustic which opens the pore size of the resin and will remove organic acids which stick to the resin.

There are two commonly referred to types of natural organic acids:
  • Humic acid comes from decayed leaves and other vegetation.
  • Tannic acid comes primarily from decayed trees and from certain types of plants such as tea.

To reduce the level of organics going forward on to the main ion exchange plant it is possible, on highly fouling waters, to employ an organic scavenger resin. Removal of organics is a common requirement at a water treatment works. Organics affect odour, taste and colour of the treated water and are associated with adverse health effects.

The color removal process will consist out of four stages:
  1. adsorption of the TOC onto the resin
  2. displacement/backwash of the resin with softened water
  3. regeneration of the resin with brine or periodically with caustic
  4. and finally rinse using softened water. 

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