How does UV light destroy microorganisms
Ultraviolet rays with wavelengths shorter than 300 nm are extremely effective in killing microorganisms. The most effective sterilizing range for UV is within the C bandwidth (UVC). This range is called the germicidal bandwidth. UVC has been used in hospitals for decades to sterilize surgical instruments, water, and the air in operating rooms. Many food and drug companies use germicidal lamps to disinfect various types of products and their containers.
All living organisms contain DNA (deoxyribonucleic acid). DNA provides the mechanism for all functions needed to sustain life. The UV light from 200 to 300 nm is easy to be absorbed by the cells, and the 253.7 nm has the strongest disinfection ability. The UV light penetrates the outer cell membranes of microorganisms, passes through the cell body, reaches the DNA and permanently alters the genetic material. The microorganisms are thereby destroyed in a non-chemical manner. | ||||||||||||||||||
UV disinfection is a purely physical process. Micro-organisms such as bacteria, viruses, yeast, etc. that are exposed to the effective UV-C radiation are inactivated within seconds. It does not add anything to the water, such as undesirable color, odor, taste or flavor, nor does it generate harmful byproducts. It is fast, efficient, effective, economical and environmentally friendly.
The following are incident energies of germicidal ultraviolet radiation at 254 nanometers necessary to inhibit colony formation in microorganisms (90%) and for complete destruction | ||||||||||||||||||
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| Bacillus paratyphusus | 3,200 | 6,100 |
| Bacillus subtilis spores | 11,600 | 22,000 |
| Bacillus subtilis | 5,800 | 11,000 |
| Clostridium tetani | 3,370 | 6,510 |
| Corynebacterium diphtheriae | 2,140 | 4,100 |
| Ebertelia typhosa | 3,000 | 6,600 |
| Escherichia coli | 3,150 | 6,000 |
| Leptospiracanicola - infectious Jaundice | 6,050 | 12,300 |
| Microccocus candidus | 1,000 | 15,400 |
| Microccocus sphaeroides | 6,200 | 10,000 |
| Mycobacterium tuberculosis | 4,400 | 8,000 |
| Neisseria catarrhalis | 3,000 | 6,600 |
| Phytomonas tumefaciens | 5,500 | 10,500 |
| Proteus vulgaris | 3,500 | 6,600 |
| Pseudomonas aeruginosa | 4,000 | 7,600 |
| Pseudomonas fluorescens | 3,200 | 6,100 |
| Salmonella enteritidis | 2,150 | 4,100 |
| Salmonela paratyphi - Enteric fever | 8,000 | 15,200 |
| Salmonella typhosa - Typhoid fever | 19,700 | 26,400 |
| Salmonella typhimurium | 2,420 | 6,160 |
| Sarcina lutea | 2,200 | 4,200 |
| Serratia marcescens | 1,700 | 3,400 |
| Shigella dyseteriae - Dysentery | 1,680 | 3,400 |
| Shigella flexneri - Dysentery | 4,400 | 6,160 |
| Shigella paradysenteriae | 1,840 | 5,720 |
| Spirillum rubrum | 2,600 | 6,600 |
| Staphylococcus albus | 2,160 | 5,500 |
| Staphylococcus aerius | 6,150 | 8,800 |
| Staphylococcus hemolyticus | 2,000 | 3,800 |
| Staphylococcus lactis | 6,150 | 8,800 |
| Streptococcus viridans | 2,000 | 3,800 |
| Vibrio comma – Cholera | 3,375; | 6,500 |
| Organisms: | ||
| Energy dosage of Ultraviolet radiation in цW/cm2 needed for kill factor | ||
| Molds | 90% | 100% |
| Aspergillius flavus | 4,520 | 8,700 |
| Aspergillius glaucus | 24,320 | 46,200 |
| Aspergillius niger | 2,730 | 5,200 |
| Mucor racemosus A | 1,300 | 2,500 |
| Mucor racemosus B | 3,200 | 6,100 |
| Oospora lactis | 11,600 | 22,000 |
| Penicillium expansum | 5,800 | 5,800 |
| Penicillium roqueforti | 3,370 | 6,510 |
| Penicillium digitatum | 2,140 | 4,100 |
| Rhisopus nigricans | 3,000 | 6,600 |
| Protozoa | 90% | 100% |
| Chlorella Vulgaris | 6,050 | 12,300 |
| Nematode Eggs | 1,000 | 15,400 |
| Paramecium | 6,200 | 10,000 |
| Virus | 90% | 100% |
| Bacteriopfage - E. Coli | 3,000 | 6,600 |
| Infectious Hepatitis | 5,500 | 10,500 |
| Influenza | 3,500 | 6,600 |
| Poliovirus - Poliomyelitis | 4,000 | 7,600 |
| Tobacco mosaic | 3,200 | 6,100 |
| Yeast | 90% | 100% |
| Brewers yeast | 8,000 | 15,200 |
| Common yeast cake | 19,700 | 26,400 |
| Saccharomyces carevisiae | 2,420 | 6,160 |
| Saccharomyces ellipsoideus | 2,200 | 4,200 |
| Saccharomyces spores | 1,700 | 3,400 |