Stage II : Chemical Dosing

pH adjustment
Distilled water has a pH of 7 (neither alkaline nor acidic) and sea water has an average pH of 8.3 (slightly alkaline). If the water is acidic (lower than 7), lime, soda ash or sodium hydroxide is added to raise the pH. For somewhat acidic, alkaline waters (lower than 6.5), other process need to be used raise the pH by stripping dissolved carbon dioxide (carbonic acid) from the water. Lime is commonly used for pH adjustment for municipal water, or at the start of a treatment plant for process water, as it is cheap, but it also increases the ionic load by raising the water hardness. Making the water slightly alkaline ensures that the next process i.e.coagulation and flocculation processes work effectively and also helps to minimize the risk of lead being dissolved from lead pipes and lead solder in pipe fittings. Acid (HCl or H2SO4) may be added to alkaline waters in some circumstances to lower the pH. Having an alkaline water does not necessarily mean that lead or copper from the plumbing system will not be dissolved into the water but as a generality, water with a pH above 7 is much less likely to dissolve heavy metal than a water with a pH below 7.

Scope of Automation:

  1. Dosing of chemicals as per the quantity and quality of incoming water using diaphragm dosing pumps.
  2. Automated mixing of chemicals

Benefits :

  1. Dosing on basis of final achieved water quality parameters and water storage at purified water sump
  2. Automated mixing of chemicals