Biotesting – the modern criterion of evaluating the efficiency of UV-systems for water disinfection

Summary

Nowadays ultraviolet irradiation increasingly becomes an actual method of water disinfection. Herewith units with amalgam and mercury low pressure lamps are mostly used. In the radiation spectrum of these lamps the mercury resonance line is dominating with 253.7 nm wave length on which up to 40% of the lamp power can fall. Radiation with this wave length has a powerful disinfection effect. The impact of UV-irradiation results in irreversible DNA and RNA damage in microorganisms so that the latter lose their reproductive capacity (become inactivated). The main parameter that characterizes the efficiency of these installations is UV-irradiation dose. It is a calculated value, therefore to obtain the maximum information on the operation of a UV-disinfection unit it is advisable to carry out biotesting with the help of live microorganisms. Besides, in some countries (Germany, France, Austria, USA) biotesting of UV-systems is obligatory. In Russia bio-validation is not obligatory; therefore real biological tests are often substituted with computer simulation. Process simulation carried out for a seven-lamp unit manufactured by «LIT» Scientific-Production Association produces the results close to the results obtained during biotesting. This confirms the range of use of disinfection UV-unit claimed by the manufacturer. However, the absolute guarantee of the UV-unit efficiency is bio-validation only since it supposes the use of live water and microorganisms. The data obtained in the process of biotesting allow describing the specific features of the disinfection unit operation to the fullest extent possible. The certificate verifying biotesting is a credible guarantee that the unit will provide for the required level of water disinfection.

Key words

microorganisms , inactivation , biotesting , amalgam lamp , ultraviolet irradiation , UV disinfection , UV-unit , irradiation dose

Coronavirus SARS-CoV-2 in wastewater (review)

Summary

The COVID-19 pandemic, declared by WHO as a health emergency, is caused by a novel SARS-CoV-2 coronavirus. According to reports from the European Union, the United States and Australia, the potential survival of the SARS-CoV-2 coronavirus in feces and wastewater for a sufficiently long time creates a real threat of its entry with wastewater into treatment facilities or directly into surface water while raw wastewater is discharged. This indicates the potential for the transfer of SARS-CoV-2 by water. In this regard, the development of effective methods for the removal and inactivation of viruses at the treatment facilities is of special actuality. The presence of coronavirus infection in wastewater can pose a serious health hazard to people in contact with it. These include the personnel at the wastewater treatment facilities, as well as the general population, who may be directly exposed to raw or inadequately treated wastewater through defective water or sewer systems. In many countries wastewater epidemiology methods are used to obtain timely reliable information on the spread of coronavirus infection. Possible detection of RNA virus in wastewater even with a low prevalence rate of COVID-19 and the correlation between the concentration of SARS-CoV-2 RNA in wastewater and official information indicate that monitoring wastewater can become a sensitive tool for monitoring the circulation of the virus in the
population.

Key words

treatment facilities , wastewater , inactivation , SARS-CoV-2 coronavirus , feces , infection risk , removal , epidemiology of wastewater

Water Disinfection Using the UV-Irradiation at Water Treatment Facilities of the City of Angarsk

Summary

For the purpose of improving the barrier function with respect to viruses, parasites and water bacteria at water treatment facilities of Angarsk the station of potable water UV-disinfection was put into operation in 2009. The station’s equipment is located in the building of main facilities block before the vertical mixers. From the first days of operation the high efficiency of the UV-disinfection method was established. The analyses results show the complete inactivation of all water microorganisms and dependence of intensity of lamps radiation on physicochemical properties of river water as well. For the purpose of eliminating this dependence the alternative scheme of water feed is offered: treated water after the filter is delivered to UV-disinfection plants instead of river water.

Key words

potable water , chlorination , turbidity , ultra-violet disinfecting , water treatment , microorganisms , inactivation