Water Sifu #28: Chemicals in Water Treatment

The Water Sifu

Chemicals in Water Treatment

In this episode I answer a couple of common questions I often receive pertaining to searching for jobs in the water industry. I discuss a speech I recently gave about this podcast, and then we hop into the meat of the show covering chemicals we use in treatment. We discuss ferric chloride and alum as coagulants, lime and carbon dioxide for alkalininty, hardness, and pH control, and gas chlorine, liquid chlorine, and chloramines as disinfectants. We also discuss perchorate and, wrapping up the show, I ask you to do me a favor.

As discussed in the show, below are some chemical equations for subjects which we covered:

Adding gas chlorine to water drops pH by formation of two acids:
Cl₂ + H₂O = HOCL (Hypochlorous) + HCL (Hydrochloric Acid)

Hypochlorous acid breaking into the hypochlorite ion at higher pH:
OH (Hydroxyl) + HOCL (Hypochlorous) = H2O (Water) + OCL (Hypochlorite)

Adding liquid chlorine to water raises pH by forming caustic soda:
NaOCL (Sodium Hypochlorite) + H₂O = HOCL + NaOH (Sodium Hydroxide / Caustic Soda)

The combination of hypochlorous acid and ammonia forms chloramines:
NH₃ + HOCl = NH₂Cl + H₂O