The chemical compound “chlorine dioxide” is often mistaken for chlorine (bleach) but their disinfection capabilities are very different. Understanding these key differences are critical when choosing a ballast water management system (BWMS) for your ship.
Chlorine dioxide has been safely used for over 70 years in many land-based applications, including the disinfection of drinking water. It also works for a variety of antimicrobial applications in the health, industrial, oil and gas, and food industries─including fruits and vegetables disinfection, paper pulp manufacturing, and sterilization of medical and laboratory equipment to name a few.

Treatment Effectiveness

Chlorine(bleach) and chlorine dioxide are both oxidizing agents. However, chlorine dioxide is more selective in its reactions, making it effective at lower concentrations, resulting in it having 2.6 times the oxidative power than chlorine! This means that ships need to use almost triple the amount of chlorine to achieve the effectiveness of chlorine dioxide.
Chlorine dioxide reacts with living cells by first penetrating the bacterial cell wall and then reacting with the material within the living cell in order to kill the organism. Chlorine dioxide has very limited reactions with organic matter present in ambient water and works exceptionally well where high levels of organic materials(“dirty” or turbid waters) are anticipated to be present. This greatly reduces the formation of disinfection by-products and means that chlorine dioxide treatment effectiveness is not affected by turbidity, salinity or temperature.
On the other hand, chlorine reacts with almost any organic material (living and non-living) such as oil, algae, sediments, etc., This means that waters with high levels of organic matter can increase the background oxidant demand for chlorine, leaving less available to treat living organisms in ballast water or requiring an increased chlorine treatment dose. Due to the types of reactions that chlorine has with both organic and inorganic compounds, chlorine has greater potential to form undesirable by-products in the water. These by-products can pose toxicity risks to both aquatic organisms and human health.

Neutralization of Treated Water

The higher levels of chlorine required to treat ballast water comes with limitations as neutralization is required to ensure chlorine can be discharged at a safe level.
Because of its highly reactive nature with living organisms and low chemical dose, chlorine dioxide does not require neutralization or re-treatment(as is the case with UV) prior to discharging treated ballast water because it naturally decays to a safe discharge concentration.

Solubility and Disinfection Capacity Influences of pH and Water Temperature

Solubility is another important advantage in the use of chlorine dioxide for water treatment. Chlorine dioxide is 10 times more soluble in water than chlorine, making it faster-acting (especially if the water pH rises), even in cold water conditions. Chlorine dioxide effectively operates in a broader range of pH levels, ranging from 4–10, whereas chlorine has an optimum treatment range of 6—8.

Conclusion

The chlorine dioxide treatment technology is extremely powerful in low doses and is not affected by varying water conditions, such as turbidity, salt, temperature or pH. Chlorine dioxide is generated as-needed at the point of use making it an extremely safe, cost-effective and far more effective technology for the treatment of ballast water.

■ Contact: https://ecochlor.com/