Zero Liquid Discharge

Zero Liquid Discharge (ZLD) plants employ the most advanced wastewater treatment technologies to purify and recycle virtually all of the wastewater produced by using highly sophisticated plants for the purification and total reuse of waters coming from metal treatment using a combination of technologies such as: chemical-physical purification, sand and charcoal filtration, UF, RO and Evaporation.

The most common method for removing high concentrations of sulfate from water is through addition of hydrated lime (Ca(OH)₂). However, when you start with greater than 1500 ppm, it is not possible to achieve less than 500 ppm (for water to dump in river or lakes).
Only special technology, such as PUR-ALL (developed by MST Chemicals), overcome this problem and is able to provide dramatic removal capacity to less than 150 ppm or, with special technologies, also lower.

Fluorine is one of the most difficult Anion to be removed or reduce to limits of less than 6 ppm, as required by most of legislations. Only special technolgy and chemicals, such PUR-ALL (developed by MST Chemicals) overcomes this problem and achieves levels less than 4 ppm or, with special technologies, less than 2 ppm.

In Metal finishing lines COD is coming from Oils, fats used for metal working or lamination. In addition COD is coming from Surfactants in Alkaline or Acidic Cleaners used before final coating. The most common chemical product to remove COD are Charcoals, but specific blends must be developed for any local situation.
MST Chemicals have a great number of specific COD removal products such as PuroSorb able to reduce COD levels to under 100 ppm, as required for ZLD plants.

Calcium and Magnesium, as dissolved solids, are removed by either ion exchange (See below “Softening”) or by Reverse Osmosis technolgy. The first method is used, for example, to have soft water but with the same salinity (as happen for Cooling tower water). The second (RO) is used to eliminate all salts present including Ca and Mg.

The best method for groundwater heavy metal removal is the use of a selective ion exchange resin that MST Chemicals provide.