Effective and Efficient Use of Chlorine in the Offshore and Maritime Industries

Chlorine is by far the most widely used disinfectant in drinking water systems.

It is the method of choice for most municipal water utilities in all regions of the world. Where it is used, it has been crucial in the eradication of waterborne diseases such as cholera, typhoid, and dysentery.

The nearly universal application of this method can be attributed to the following factors:

• Its effectiveness against waterborne pathogens (bacteria, viruses, protozoa, and worms). Chlorine disinfection can destroy more than 99.9% of bacteria
• The precision with which the process can be monitored and controlled. Its high solubility in water makes it easy to apply in controlled quantities
• It is inexpensive and relatively easy to produce, store, transport, and use
• Its highly satisfactory performance as a disinfectant has been proven by decades of use. It has been so successful that the absence of epidemics of waterborne diseases is now virtually taken for granted. There are no documented cases of health problems resulting from correct and controlled use within drinking water systems.

Chlorine in drinking water is safe for consumption. The small amount of chlorine typically used to disinfect water poses no risk to human health. The World Health Organization (WHO) has established a guideline value of 5 mg/l (ppm) for chlorine in drinking water, meaning that such concentrations are considered acceptable for lifelong human consumption.

Chlorine is a residual disinfectant. This means that when the procedure is carried out correctly, the disinfecting properties of chlorine—and thus control—are present wherever the water is found. This distinguishes it from non-residual disinfection methods such as UV and ozone. These disinfection methods do not “travel” with the water and therefore have significant limitations.

However, it has been documented that the use of chlorine as a disinfectant can have disadvantages in the offshore/maritime industry, and these are worth noting.

Harmful byproducts

It is true that if the source water has a high organic load and is consistently over-chlorinated, the risk of forming hazardous byproducts increases. Although some of these byproducts are carcinogenic, this should not automatically lead users to refrain from using chlorine as a disinfectant. Only under exceptional circumstances would the water in the offshore sector contain sufficient organic load to pose a risk of carcinogenic byproducts. OWM has never encountered such circumstances.

There are known water sources where the organic load is high, such as in Norway, but even in such cases, an appropriate risk assessment and the right control mechanisms can ensure that chlorine remains the safe and effective disinfectant of choice. However, if a decision is made to forego residual disinfection, users must carefully consider how this may affect control. In these cases, users must still be able to demonstrate how the water is managed and maintained throughout the entire system without compromising control.

When prioritizing risks, the following statement from the WHO (World Health Organization) should be taken into account:

“The health risks of byproducts that may be present in drinking water are extremely small compared to the risks associated with inadequate disinfection. It is therefore important that disinfection is not compromised in efforts to control such byproducts.”

Unpleasant taste and odor

Sensitivity to the taste and odor of chlorine is an aesthetic issue and should never take precedence over health and safety concerns. Sensitivity to the taste and odor of chlorine in water is primarily determined by two criteria: what a person is accustomed to and the chlorine concentrations in a water system.

If a person is accustomed to drinking water that does not contain chlorine, concentrations at the upper end of the control points (0.2 ppm–0.5 ppm) or slightly above may be noticeable. If concentrations are consistently higher than the control points and continue to rise, eventually all individuals will perceive chlorine as a taste, odor, or both. (In both cases, as long as chlorine concentrations are below 5.0 ppm—that is, 10 times the control level—there is no health risk.) To reduce complaints about taste and odor, chlorine addition must be kept within the control limits. The proper selection and use of chlorine dosing equipment ensures that this is always the case.

The primary goal of disinfection in all public and private water supplies is the elimination of pathogens responsible for waterborne diseases. OWM is an independent provider of all services and support in the field of water management, and we recommend the use of chlorine as a safe and reliable solution for this purpose.