Virus inactivation effect of hypochlorite solution containing nitrate ions

Area of Science:

• Environmental Science
• Microbiology
• Chemical Engineering

Background:

• Hypochlorous acid (HClO) is a potent disinfectant but its efficacy is pH-dependent, decreasing in neutral to alkaline conditions.
• High concentrations of HClO raise safety and environmental concerns.
• There is a need for effective disinfection methods using lower concentrations of disinfectants.

Purpose of the Study:

• To investigate the enhancement of virucidal activity of low-concentration hypochlorous acid (HClO).
• To explore the role of monochloramine (NH2Cl) formation by supplementing with ammonium-form nitrogen (NH4+-N) or nitrate-form nitrogen (NO3--N).
• To evaluate the impact of different pH conditions on disinfection efficacy.

Main Methods:

• Utilized bacteriophage φ6 as a model enveloped virus.
• Conducted plaque assays to determine virus inactivation.
• Tested varying concentrations of HClO, NH4+-N, and NO3--N under acidic (pH 6) and alkaline (pH 8) conditions.

Main Results:

• Virus inactivation was most effective at pH 8 with 15-20 ppm NH4+-N added to 30 ppm HClO, achieving over 90% infectivity reduction.
• At pH 6, NH2Cl formation was limited, reducing efficacy, though increased NH4+-N improved inactivation.
• Enhanced NH2Cl formation at pH 8 significantly improved disinfection efficiency; similar results were seen with NO3--N.

Conclusions:

• Optimizing pH and nitrogen sources can significantly enhance the virucidal efficacy of low-concentration HClO solutions.
• In situ generation of monochloramine (NH2Cl) is a key mechanism for improved disinfection.
• This approach offers a safer and more sustainable alternative for viral disinfection.