N5-Disinfection and Biofouling Control Alternatives to Chlorination

Many facilities are presently using a chlorine gas injection system for biofouling control.  I would like to take this opportunity to indicate a simple alternative to this control strategy.  This alternative is to replace chlorine gas with 12% sodium hypochlorite (also commonly referred to as Javex).

A number of companies in North America have opted to change from a gas to a liquid chlorination system.  The main driving forces behind this conversion trend are the Health and Safety concerns associated with chlorine gas.  Since the Mississauga incident in November, 1979, which resulted in a large release of chlorine gas to the environment, many firms have become concerned that gas systems pose an unacceptably high risk to company personnel, the public, the environment and the facility itself.  Chlorine gas is very toxic and corrosive if released into a work area and/or the environment. It is also important to note that heat generated from a fire or chemical reaction(s) can result in equipment made of steel in contact with chlorine vapour to burn spontaneously.

Many operators are also concerned about handling pressurized chlorine cylinders, supply tankers and gas distribution systems.  Leaks not only pose a health and safety concern but can also attack equipment in the local vicinity.  Extreme safety measures must be implemented to protect both the gas system itself, as well as to warn personnel of chlorine gas leaks.  In order to minimize risk, it is critical that routine maintenance is performed in order to protect the operating integrity of the system.

From a risk management viewpoint, 12% sodium hypochlorite significantly reduces the health and safety concerns for company personnel, the public and the environment.  It also reduces the risk to the system operating integrity.  This is because sodium hypochlorite is less toxic and less corrosive than chlorine gas.

From an operating and handling viewpoint, sodium hypochlorite systems require less maintenance and the chemical attacks skin and/or other moist membranes at a significantly slower rate than chlorine gas.

From an environmental viewpoint, it is far easier to contain a leak from a liquid sodium hypochlorite chlorination system than from a gas chlorination system.  The potential area of impact is significantly less for liquid sodium hypochlorite chlorination systems.

The author of this article is a project engineer and has installed a number of state of the art automatic liquid chlorination systems.  These systems use proven control strategies and incorporate safety measures and alarms to ensure the reliable operation of the system and meet environmental compliance requirements.