Introduction

With the primary goal of ensuring drinking water safety, chlorine dioxide (ClO₂) is typically employed as a pre-oxidant in water treatment processes. Prior to the formal oxidation stage, ClO₂ is dosed into raw water to inhibit the proliferation of bacteria and algae in subsequent treatment units, serving as a critical measure to safeguard drinking water security. In this chapter, we will examine the functional mechanisms of ClO₂ in drinking water systems in collaboration with Moody.

Functional Mechanisms of Chlorine Dioxide  

Upon dosing ClO₂into water, the agent reacts with aqueous matrices, oxidizing suspended particles sequentially. This process effectively reduces turbidity in surface water, thereby enhancing the multi-barrier protection of drinking water safety. Notably, ClO₂exhibits strong efficacy in removing pre-formed biofilms within water supply networks, directly targeting pathogenic microorganisms for inactivation. Additionally, ClO₂maintains its biological activity in water for up to 48 hours, enabling it to suppress the re-accumulation of biofilms in downstream systems.

The absence of ClO₂in the pre-oxidation stage significantly elevates the risk of bacterial and viral proliferation, which not only degrades water quality but also poses potential threats to ecological stability and human health in severe cases.

Safety Considerations and Regulatory Compliance

Moody emphasizes that prior knowledge of safety protocols is imperative before ClO₂ application. While ClO₂ is a widely used drinking water disinfectant, the U.S. Environmental Protection Agency (EPA) has established strict regulatory limits for its residual concentration in finished water. Exceeding these limits may induce adverse health effects such as dyspnea and coughing.

Furthermore, post-treatment monitoring is a non-negligible step: real-time water quality analyzers are installed at both the inlet and outlet of treatment facilities to continuously monitor water parameters. Only when the water quality meets safety standards is it deemed potable.