The Practical Advantages of Chlorine Gas Disinfection

Chlorination of water supplies can be achieved using three different chemical mediums; chlorine gas, calcium hypochlorite (available as a solid in granular form), or sodium hypochlorite (the equivalent to liquid bleach).

The practical advantages and disadvantages of each are summarized in the following table (White, 1996):

 GasCalcium HypochloriteSodium Hypochlorite
% Concentration by Weight of Available Chlorine100%65%3% to 12.5%
Quantity of Media RequiredLowModerateHigh
Required Storage SpaceMinimalModerateHigh
Transportation CostsMinimalMinimalHigh
Safety Concerns
(Chlorine gas is a skin and mucous membrane irritant. Chlorine gassings can be the result of a leak from a gas chlorine system or off-gassing from sodium hypochlorite liquid or the predisinfection solution prepared by mixing water with calcium hypochlorite).
  • Potential gas release
  • Corrosive
  • Sensitive to heat and sunlight
  • Off gassing of chlorine, especially from solution
  • Spontaneously combusts
  • Corrosive
  • Sensitive to heat and sunlight
  • Off gassing of chlorine
  • Corrosive
  • Sensitive to heat and sunlight
Chemical AdditionNoneCalciumSodium
(Degradation of potency with time, as dependent on conditions while releasing chlorine gas)
Personnel OversightMinimalHighModerate
Additional Comments"Clean" application"Messy" application and residue problems are common"Messy" application

To summarize, the advantages of GAS chlorination are obvious.

The only theoretical disadvantage is the potential for a gas leak in poorly designed systems. For this reason, all Hydro chlorinators are designed to mount directly onto the chlorine cylinder, thereby eliminating ANY pressure lines. Hydro gas chlorination systems are vacuum operated, therefore if a break in the system occurs it automatically shuts down, eliminating the potential for a leak. Hypochlorite systems inject the treatment solutions (at 10 to 15% concentration) directly into the water stream under pressure. If a leak in a hypochlorite treatment system occurs, copious volumes of treatment solution can be released and chlorine gas is immediately vaporized from the concentrated solutions into the surrounding atmosphere. For this reason, hypochlorite systems are no safer than chlorine gas systems.

Besides these practical advantages, there are also considerable economic advantages to the usage of chlorine gas disinfection.