Types of Bacteria Inactivated by Low-Pressure High Output (LPHO) UV Disinfector

LPHO UV lamps emit monochromatic UV light mainly at 254 nm. It targets and damages microbial DNA and RNA, achieving broad-spectrum inactivation of Gram-positive and Gram-negative bacteria. With adequate UV dose and good UV transmittance of water, inactivation efficiency can reach 99.9%~99.99%.

Gram-negative Bacteria (Common pathogens in swimming pools)

• Legionella pneumophila

• Pseudomonas aeruginosa

• Escherichia coli

• Klebsiella pneumoniae

• Salmonella spp.

• Shigella spp.

• Vibrio cholerae, Vibrio parahaemolyticus

Gram-positive Bacteria

• Staphylococcus aureus

• Enterococcus faecalis, Enterococcus faecium (indicator bacteria of NSF/ANSI 50 for swimming pools)

• Streptococcus spp.

Note: Bacterial spores are highly resistant. LPHO UV at 254 nm requires extremely high dosage for effective inactivation, and performs worse than medium-pressure UV under the same conditions.

Other Pathogens

Viruses: Adenovirus, Norovirus, Rotavirus, Hepatitis A virus Protozoa: Cryptosporidium parvum, Giardia lamblia (LPHO UV can inactivate them when the required UV dose is met, widely adopted in swimming pool industry) Algae: Inhibit algae activity, limited effect on mature algae.

Important Notes

1. LPHO UV works as secondary disinfection. Residual chlorine shall be kept in pool water as UV has no persistent disinfection effect.

2. Performance depends on UV transmittance, flow rate and UV dose. Suspended solids block UV rays and reduce disinfection efficiency.

3. Limitation: Single wavelength at 254 nm. Some microbes have the risk of photoreactivation (DNA repair under visible light). LPHO UV is less effective than medium-pressure UV in suppressing photoreactivation.