Abstract:
To research the influence of: the irradiation with ultraviolet (UV), the above- and over limit
moderate temperatures, the environment’s pH, as well as the combination of the above-mentioned
factors on microorganisms, aiming the detection of the factor with the highest capacity of
disinfection. We have collected air samples and isolated microorganisms from them. Then we’ve
grown the microorganisms on Petri boxes. These Petri boxes were distributed in groups and subjected
to different growing conditions (ultraviolet irradiation, action of different types of environment’s pH,
above- and over limit temperatures). After the incubation period, we have calculated the number and
the percent of survived colonies as well as the disinfection capacity of each factor. This study showed
that all the above mentioned factors, in some measure, affect the growth and development of
microorganisms. UV radiation has a high capacity of disinfection. Even a short time influence (5
minutes) causes a significant decrease (28%) of the microorganisms number. Increasing the duration
to 10 minutes, we didn’t obtain meaningful results (efficiency increased by only 8%). In case we use
UV irradiation for 15 minutes, we get an efficiency of about 64%. Above- and over limit moderate
temperatures don’t visibly affect the number of microorganisms (7% for low temperatures and 29%
for high temperatures). Environmental acidity is a factor with a noticeable influence on the number of
microorganisms. Both strong acidic pH (pH = 2), as well as the strong basic pH (pH = 12) cause an
obvious decrease of the microorganisms number (equal to 54% and 66% respectively). Combining
the high temperatures, the acid environment and ultraviolet irradiation for 15 minutes, we get an 85%
result. Combining ultraviolet irradiation for 15 minutes, basic pH and low temperatures, the
disinfection capacity decreases up to 64%. The method with the lowest efficiency is the action of over
limit moderate temperatures. The best results on the disinfection capacity were obtained by
combining physical and chemical factors. Each factor separately taken is unable to achieve such
results.
