1) What is a mixed oxidant solution (MOS), and how is it produced?

The main components of mixed oxidant solution (MOS) are chlorine and its derivatives (ClO− and HClO), along with hydrogen peroxide and other trace oxidants, which are produced by electrolysis of sodium chloride (salt). On-demand systems can safely produce a disinfectant solution for potable, non-potable, and utility water.  

2) How does MOS control Legionella and biofilm?

Mixed oxidant solution (MOS) penetrates and disrupts biofilm, improving control of organisms such as Legionella in building water systems. At equivalent dose and contact time to standard chlorine, mixed oxidants inactivate microbes faster and with more complete microbial control. 

3) What target residuals are used for Legionella control with MOS?

For Legionella control, a target concentration around 0.5 ppm (or higher as needed) will reduce Legionella substantially. At this level, Legionella is typically killed in the water, and biofilm is greatly reduced, but there are never any official “safe” levels for 100% eradication of Legionella. 

4) Where is MOS commonly applied?

Hospitals, senior living, nursing homes, and other healthcare facilities use mixed oxidant solution (MOS) for secondary disinfection. It is also used in cooling tower treatment and other building water applications.

5) How is MOS different from standard chlorine?

• Disinfection efficacy: Faster and broader microbial inactivation.
• Biofilm: More effective at penetrating and disrupting biofilm.

6) What makes mixed oxidant systems safe and practical to operate?

• Use only salt and water as precursors
• On-demand generation with simple maintenance
• Optional remote monitoring and easy integration with existing infrastructure

7) Can the same platform produce sodium hypochlorite instead of MOS?

Certain on-demand systems can be configured for either sodium hypochlorite or mixed oxidant production, offering flexibility for site needs.

8) Does MOS affect taste and odor?

Compared with basic chlorination, MOS can improve overall water quality and contribute to better taste and odor.

9) Are there charts or downloads that show MOS performance?

Yes. See the “Free Chlorine Levels and MIOX Impact on Biofilm” chart and the Mixed Oxidant Solution downloads (RIO Zuni, AE, VAULT, RIO M, RIO Grande) for performance and specifications.

• Mixed Oxidant Solution (MOS) overview
• Mixed Oxidant Systems models & downloads
• Mixed Oxidant & Chlorine Dioxide Levels for Legionella Control

11) Where can I request product literature or a quote?

Contact us for details, sizing guidance, and pricing:

• Contact Page
• Chlorine Demand Calculator and Guide for Legionella
• Secondary Disinfection Systems – Mixed Oxidant Systems
• Secondary Disinfection Systems – MOS page