Choosing the right biocide is critical to maintaining a safe, compliant, and efficient water system. Ask ten water treatment professionals which biocide is best, and you’ll likely hear ten different answers—often based on anecdotal experiences rather than data-driven outcomes. At Watertech of America, we believe in matching the right solution to each facility’s unique challenges. One biocide that consistently delivers powerful results across various applications is Chlorine Dioxide (ClO2).
In this article, we explore the properties, benefits, and best-use scenarios for Chlorine Dioxide—and why it's often our top pick when high-performance disinfection is essential.
What is Chlorine Dioxide?
Chlorine Dioxide (ClO2) is a yellowish, chlorine-based oxidizing agent generated by converting sodium chlorite. With decades of proven use in industries ranging from pulp and paper to potable water treatment, it has earned a reputation as an effective and versatile disinfectant.
Chlorine Dioxide gained early traction in municipal water systems beginning in 1944 in Niagara Falls, NY, where it replaced chlorine to reduce the formation of trihalomethanes (THMs)—carcinogenic byproducts of chlorine in organic-rich water. Its effectiveness in protecting public health has made it a trusted choice for facilities worldwide.
Key Benefits of Chlorine Dioxide
Chlorine Dioxide offers several advantages over traditional disinfectants like chlorine and bromine, including:
- Effective at higher pH levels: ClO2 remains highly effective even above a pH of 7, where chlorine loses efficacy.
- Less corrosive: It’s gentler on piping, system components, and infrastructure, reducing long-term maintenance costs.
- No harmful byproducts: Unlike chlorine, ClO2 does not produce trihalomethanes (THMs) or other hazardous residuals.
- Lower dosage requirements: Higher efficiency means less chemical usage, reducing inventory and transport-related expenses.
Considerations and Safety Notes
As with any oxidizer, Chlorine Dioxide should be handled with care. While the benefits are substantial, it’s important to consider:
- Safety of sodium chlorite: The precursor chemical is highly reactive and flammable (especially when dried), requiring specialized storage and handling protocols.
- Susceptibility to degradation: ClO2 is less stable than some alternatives and may require special storage or on-site generation for maximum efficacy.
- Higher upfront cost: Although more expensive than chlorine, the long-term value and performance often justify the investment.
Real-World Success with Watertech
At Watertech, we’ve successfully deployed Chlorine Dioxide in a range of challenging industrial applications, with impressive outcomes. Here are two notable examples:
Case Study 1: Legionella Control in a Chemical Plant
A large chemical manufacturer faced recurring Legionella outbreaks (up to 10,000 CFU) across multiple cooling towers. Standard biocides, including bromine and DBNPA, failed to resolve the issue. Watertech introduced a Chlorine Dioxide program with ORP-based control. Within a month:
- Bacteria dipslide results dropped from 105 to 10¹ CFU
- Legionella counts reached non-detectable levels
This demonstrates ClO2’s superior ability to control pathogens in difficult environments with much faster remediation times than alternative biocide.
Case Study 2: Bacterial Control in a Biotech Chilled Loop
A biotech firm producing bacterial cultures struggled with persistent high total bacteria counts in a chilled water loop, risking significant product losses. After transitioning from hydrogen peroxide to a Watertech-installed Chlorine Dioxide generator, maintaining a 0.6 PPM residual:
- Total bacteria levels dropped dramatically within two weeks
- Ongoing results have remained consistently negative
This switch not only preserved product quality but also improved operational confidence.
Partnering for the Right Biocide Solution
Selecting the best biocide isn’t about choosing the most “preferred” chemical—it’s about understanding your system, goals, costs, and risks. Chlorine Dioxide offers outstanding performance in many cases, but it’s not one-size-fits-all.
That’s why Watertech partners with each client to design customized biocide programs based on system design, compliance requirements, and performance objectives. From site surveys, on-site support, smart chemical automation, and pathogen testing, we provide a complete water management solution.
Ready to explore how Chlorine Dioxide can benefit your system?
Request a site survey today and let our Technical Engineers develop a treatment strategy tailored to your facility.
Shawn Kenar
Field Service Technician
Shawn has been with Watertech of America for 8 years providing industrial water treatment solutions for boiler, cooling and wastewater applications. Shawn leads educational training events and seminars to promote better water management and improve safety.