Desalination Pretreatment: Seawater chlorination

Chlorination

Surface water contains various microorganisms, bacteria, protozoan, that would contributes to a biofilm formation on the membrane surface. A biofilm is a bacteria colony that grows on a designated surface where a carbon source and nutrients are available. Killing bacteria and microorganism before entering the membranes will prevent biofouling.

The typical chlorine dose is about 3 mg/L of active chlorine. It gas be injected by dosing Sodium Hypochlorite (NaOCl) for small scale plant or Chlorine gas (Cl2) for medium scale plants.

Large Scale desalination plants uses electrochlorination to produce sodium hypochlorite (NaOCl) from the excess of sodium chloride salt (NaCl) present in seawater at about 30 to 40 g/L:

NaCl + H2O + direct current --> NaOCl + H2

pH should be corrected around 7.5 to have optimized chlorine disinfection potential.

More details on Chlorine disinfection mechanisms, click here.