Legionella prevention and biofilm removal using MIOX Mixed Oxidant Solution | News press | MIOX

Legionella Control in Cooling Tower Water Treatment using MIOX Mixed Oxidant Solution

MIOX Controls Legionella
MIOX’s Mixed Oxidant Solution is More Effective at
Removing Biofilm and Legionella from Water

MOS Shows Increased Efficacy against Legionella compared to Common Biocides

MIOX has performed comparative water disinfection studies using 3 oxidizing biocides and 3 commonly used non-oxidizing biocides against Legionella pneumophilia. The organism L. pneumophilia is known to be pathogenic and commonly resides within biofilms in cooling tower water and potable water treatment systems. Model cooling tower waters were used in a comparative efficacy study and disinfection was evaluated at pH 7.0 and 8.5. Due to the slow-acting nature of non-oxidizing biocides, L. pneumophilia inactivation was observed over an 18 hour period, with samples obtained after 0.5, 1, 4, and 18 hour exposure times to the various biocides.

Figure 1 shows disinfection results at pH 8.5 against Legionella. MOS provided better disinfection (>5.5 log inactivation) compared to the other biocides and validated field data whereby bromine chemistry and non-oxidizing biocides are easily replaced with MOS chemistry. Hypochlorite (bleach only) achieved a 4 log inactivation and bromine showed 4 log initially with decreased efficacy over time.

Figure 1: Biocide comparison study demonstrates MOS superiority. L. pneumophilia (ATCC 33152) exposed to 0.25 mg/L MOS, bleach or bromine, 5 mg/L MCIT, 5 mg/L DBNPA and 20 mg/L Glutaraldehyde at pH 8.5. Exposure times were 0.5 h, 1 h, 4 h and 18 h. MCIT = Methylchloroisothiazolinone; DBNPA = 2,2-dibromo-3-nitrilopropionamide; MOS = Mixed Oxidant Solution; Bleach = delivered hypochlorite; Bromine = Activated sodium bromide. Similar results showing MOS performance is superior to hypochlorite have been achieved during 3rd party testing and in the field.

MOS Shows Increased Biofilm Removal over other Biocides, especially at high pH

There have been two published studies comparing the disinfection efficacy of MOS with hypochlorite at various pH values. MOS consistently performs better at higher pH against a variety of organisms, including viruses, oocysts and bacteria. Studies conducted at the University of New Mexico comparing equivalent chlorine concentrations of hypochlorite to MOS showed that, after 10 minutes of exposure at a pH of 8.0, MOS achieved total kill against L. pneumophila and P. aeruginosa while chlorine alone did not, as shown in Figure 2.

Figure 2: Biocide comparison study demonstrates MOS superiority. P. aeruginosa and L. pneumophilia were exposed to 2 mg/L MOS or bleach at pH 8.0 for 10 minutes (Barton 1996).


Initial Microorganism Concentration

Mixed Oxidants

(2 mg/L)

NaOCl (2 mg/L)

Legionella pneumophila

1 x 105

0 CFU/mL

> 2 CFU/mL

Pseudomonas aeruginosa

1 x 105

0 CFU/mL

1,200 CFU/mL

Larry Barton, PhD, University of New Mexico "Disinfection of Simulated Cooling Tower Water” - March 4, 1996


Legionella Control using MIOX Mixed Oxidant Solution