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UDC 628.166.085

Kostyuchenko S. V., Koudryavtsev N. N., Svitnev S. A., Timakov S. V., Ustiuzhaninov A. M., Shcheglov A. Iu.

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

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UDC 628.166.085

Bogun P. V.

On increasing the capacity of UV-units for liquid disinfection

Summary

The results of theoretical studies of the possible capacity improvement of units for disinfecting liquids including water by ultraviolet irradiation eliminating any increase in energy consumption are presented. Capacity improvement is possible at the fixed reactor geo­metry and source strength owing to the redistribution of liquid flows in the reactor. It is shown that the maximum possible efficient radiation dose is equal to the mean by reactor volume radiation intensity multiplied by the mean time of liquid residence in the reactor. The necessary and sufficient condition for obtaining this dose is the availability of liquid flow in every point of the reactor volume and equal radiation dose for every microvolume of liquid. By way of example the calculations of the maximum possible radiation dose for a spherical reactor with a point source of radiation and for a cylindrical reactor with a linear radiation source are presented. It is noted that widely manufactured at present UV water disinfection unit designs with a single source (a lamp) use only 30% of the source capa­city. The design with a cylindrical reactor and spiral downward liquid flow distributed along the reactor length provides for the maximum possible radiation dose and/or capacity of the installation.

Key words

water disinfection , ultraviolet irradiation , irradiation dose , reactor , installation capacity

DOI 10.35776/MNP.2020.05.01
UDC 628.166.085

Bogun P. V., Kniazeva Elena

Improving the energy efficiency of UV water disinfection systems

Symmary

The performance of a number of ultraviolet water disinfection systems available on the market is analyzed in comparison with systems of the maximum capacity reached as a result of theoretical studies, at the same energy consumption. It is demonstrated that the maximum performance values declared by the system manufacturers are 1.1–2 times less than could be obtained for the same designs, provided the irradiation uniformity of the treated flow is ensured. A technical solution is proposed that provides for the uniform exposure due to the flow velocity distribution that decreases with the distance from the lamp in proportion to a decrease in the average irradiation intensity along the length of the lamp. This solution allows approaching significantly the maximum design performance with the minimal cost and minor changes in the design. The distribution of treated water flows in a system with diaphragms-spreaders that ensure the required flow direction, is investigated. It is demonstrated that for a reactor vessel up to 50 cm long one diaphragm is enough, whereas for larger vessels installing additional flow spreaders can solve the problem. Possible use of the proposed solution for any systems with a longitudinal flow relative to the location of the UV lamps is shown.

Key words

ultraviolet , water disinfection , flow rate , irradiation dose , UV-lamp , flow spreader

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