UDC 556.18:628.16
DOI 10.35776/VST.2024.10.01

GERASIMOV M. M., Sverdlikov Aleksandr, Belyak А. А., SMIRNOV A. D., Nikolenko Il’ia, Safonov Aleksandr, Kopachevskii Anatolii

Estimation of the feasibility of using part of the Salgir River flow
to provide for the water security of the Crimea

Summary

A pilot complex for testing technologies for the purification of the Salgir River water has been developed, assembled and commissioned. The test results are presented for both the design process flow scheme of the water treatment facilities of the Mezhgornyi Hydroengineering Complex of the Republic of Crimea and a number of proposed upgraded flow schemes involving the use of sorbents and oxidizers at the pilot complex with real water from the water source. Meeting the required degree of water purification efficiency for the permanganate index and rated values of dichromate oxidizability was achieved with the process flow scheme with double dosing of powdered activated carbon in combination with an oxidizer – hydrogen peroxide. The feasibility of using the Salgir River as a water source for supplying water to the population of the Republic of Crimea has been confirmed.

Key words

UDC 556.531
DOI 10.35776/VST.2024.10.02

Mirasbekov Rakhman, Ialaletdinova A. V., Yalaletdinov Radik, Vazhdaev Konstantine, Аллабердин А. Б., Iusupov Artur

Simulation of the temporal variations in water color of a water source

Summary

The time series of water color at the surface water intake were processed for a 28-year period (1994–2021). The attained results were compared with the results of a previous study for 18 years (1997–2014). New patterns of water color variations (28 years) were identified that differ from those of the earlier studies (18 years). It was determined that the annual seasonal changes in water color noted earlier (18 years) existed also over the 28-year period; however, the values ​​of this indicator for the same months differed. It was found that the average annual values ​​of the indicator changed stochastically; periods of the water color reduction were noted (1998–2009, 2016–2021) alongside with the periods of the indicator value increase (1995–1998, 2009–2015). It was revealed that the downward trend in the indicator values ​​continued for another period of 28 years; however, more slowly compared to the 18-year period. Apparently, the upward trend in water color values ​​in the period 2009–2015 had certain effect on the trend equation for the entire period, as well as on the changes in the contribution of the time series components compared to the 18-year period. The analysis of the time series (additive modelling with the average annual smoothing method) revealed that for the 28-year period, the contribution of the seasonal value to the water color values ​​decreased and amounted more than 49.6%. A fairly significant increase in the contribution of the random variable (from 27.8 to 46.2%) was also noted. The analysis and comparison of different periods (1998–2009, 2009–2015 and 2016–2021) shows that the quality of water in the source by color is affected by different factors. An increase in the contributions of the seasonal and random components leads to an increase or decrease in the indicator values. Differentiation of the annual cycle of the water source into the periods characterized by similar trends in water color variations revealed differences in the time frames compared to the 18-year period. This may be evidence that, in addition to natural factors, water color may also be affected by the urban agglomeration.

Key words

water quality monitoring , time series , additive model , water color , surface water intake , seasonal component , random component , average annual smoothing method , trend-cyclic component

UDC 620.92:697.3:621.577
DOI 10.35776/VST.2024.10.03

Khabirov Iulai, Solov’ev Ruslan, Khamidullin Il’dar

Estimation of the possible use of wastewater thermal energy
for the auxiliaries of the treatment facilities

Summary

Through the example of the wastewater treatment facilities of Mayachnyi village in the urban district of Kumertau (Republic of Bashkortostan), the possibility of using the thermal energy of effluent to heat incoming wastewater in order to enhance the biological treatment process, as well as for heating buildings, is studied. A heat recovery scheme with the transfer of thermal energy for heating wastewater in a surge tank using a surface heater «jacket» mounted inside the tank of the pipe register or in a heat exchanger «pipe-in-pipe» installed downstream the tank is considered. The required heat output of the heat pump unit has been determined, and the design parameters of various heat exchange units have been calculated. The technical limitations that complicate using a «pipe-in-pipe» heat exchanger and pipe registers have been identified. The possibility of heating incoming wastewater to 18–25 °C has been demonstrated.

Key words

wastewater , ecology , heat pump , power efficiency , resource conservation , secondary thermal energy , recovery

UDC 621.671:532.528
DOI 10.35776/VST.2024.10.04

Baranchikova N. I., Yepifanov S. P., Kul’kov Viktor

Calculation of cavitation parameters of centrifugal pumps

Summary

The efficient long-lasting operation of pumping units with centrifugal pumps is achieved to a large extent by avoiding cavitation during the operation. To ensure the operation of pumps avoiding cavitation at the design and operation stage is only possible on the basis of correctly performed calculations of the cavitation parameters. By comparing the cavitation parameters with the required ones developing the essential operation modes of the pumping units is possible. Particular attention should be paid to pumping units with variable speed drives, since the recalculation of the cavitation characteristics while changing the rotation frequency of the impeller according to the one available plant characteristic does not always provide for obtaining an adequately changed cavitation characteristic. Therefore, for large pumps and with a sufficiently small cavitation NPSH, a method for recalculating cavitation characteristics using two basic cavitation characteristics of the pump is proposed. While using a pump with a sheared impeller, the cavitation characteristic for the sheared impeller shall be applied that is often just over the characteristic for the rated impeller. Another factor that should be taken into account to avoid cavitation in pumps is gaseous cavitation while determining the available NPSH. A widely used in foreign practice method for recalculating the available permissible NPSH to the actual one with account of the presence of gas cavitation, is given.

Key words

centrifugal pump , NPSH required, vaporous cavitation , vaporous cavitation , gaseous cavitation , head and rate , cavitation characteristic , pump impeller , pump impeller shearing

UDC 628.355.2:631.461.2
DOI 10.35776/VST.2024.10.05

Wang Weize, Makarova S. V.

Temperature effect on nitrification processes in activated sludge

Summary

Temperature has been an important factor affecting the efficiency of biological nitrogen removal by activated sludge at wastewater treatment facilities. A laboratory SBR reactor was used in the experiments; activated sludge for cultivation was obtained from aeration tanks of the municipal wastewater treatment facilities. The taxonomic composition of bacteria in activated sludge was determined by high throughput sequencing of the DNA section encoding 16S rRNA. The nitrification rate was determined at water temperatures of 1, 5, 8, 11, 17, 19 and 21°C. Nnitrifying bacteria Nitrosomonas spp. and Nitrospira spp. were found in activated sludge with the abundance of 0.07% and 0.34%, respectively. The maximum nitrification rate observed at 21 °C was 4.3 mg N–NO₃ per 1 g of ash-free substance of activated sludge per hour. The nitrification rate decreased with decreasing temperature and was 0.3 mg/(g·h) by N–NO₃ at 1°C. The results of the study can be used as a theoretical basis for optimizing the operation of the treatment facilities in areas with low temperatures to improve the efficiency of nitrogen removal from wastewater.

Key words

wastewater , nitrification , activated sludge , temperature , biological removal of nitrogen

UDC 628.1/.3:006.052
DOI 10.35776/VST.2024.10.06

Orlov V. А., Primin Oleg

Assessment of the air and water environment in gravity sewer networks and measures to control odors and gas formation

Summary

One of the global tasks of the municipal services is to ensure comfortable living conditions for people, for which purpose the greatest attention should be paid to such aspects as clean water and air. The regulatory and technical documentation on the analysis of the urban air and wastewater transported through gravity sewers with malodorous gases present in the underroof space, are subject to study and assessment. The sources of pollution with odors detrimental to human health that result from the intensive biochemical processes in gravity networks are considered, as also measures are analyzed to reduce or eliminate the harmful effects of gases detrimental to human health. An analytical review of the results of potential analysis of samples of wastewater and air in the underroof space of sewers was conducted. It was noted that some types of microorganisms present in the enclosed airspace of sewer manholes could produce a negative impact on the human body, i.e. pose health risks to the maintenance staff of sewer networks while working in manholes without individual respiratory protective means. Chemical, mechanical and hydrodynamic methods for neutralizing substances that provoke the appearance of malodors are considered.

Key words

gravity sewer , air microflora , water pollution , malodorous and toxic substances , odor neutralization

UDC 628.2:621.644.073
DOI 10.35776/VST.2024.10.07

Zakharov Iu. S.

Classification of gravity sewers at the pipeline rehabilitation
with flexible polymer liner

Summary

One of the dynamically developing areas of the construction industry since the early nineties of the last century has been the rehabilitation of damaged underground pipelines using «pipe-in-pipe» technologies. The rehabilitated pipeline shall meet the requirements for new pipelines, i. e. be hermetic, environmentally safe and safe in service, resistant to static loads, to transported wastewater, to abrasion and loads during water blasting. Based on the static calculation performed when selecting the parameters of a new pipe for pipeline rehabilitation, it is necessary to confirm the bearing capacity, serviceability and steadystate stability of the pipeline after rehabilitation, as well as, if necessary, the impossibility of soil collapse (sinking). A clear definition of the required wall thickness of a new polymer pipe, the choice of a suitable technology for pipeline rehabilitation and the service life of the pipeline after rehabilitation largely depend on the correct classification of the pipeline being restored. Therefore, in order to perform a high-quality static calculation, minimize errors in selecting the design and parameters of a flexible polymer liner, as also to ensure long-term trouble-free operation of the «new pipe – pipeline – soil» system, a visual inspection of the pipeline being restored should be carefully carried out in accordance with the classification given in the article.

Key words

pipeline , water disposal system , rehabilitation , flexible polymer liner , statistic calculations

UDC 697.9:614.481.33
DOI 10.35776/VST.2024.10.08

Райзер Ю. С., Gataullina Alina, Abdullin Zakir

Study of the fire resistance rating of fire dampers in the ventilation system

Summary

The results of testing fire dampers of the Vertro trademark: KZО-2-60-800×800-O-S220-T-KR, type KZО-2-60-O, KZО-2-90-800×800-O-S220-T-МC-KR, type KZО-2-90-O and KZО-2-120-800×800-O-М220-T-KR, type KZО-2-120-O against the declared fire resistance rating are considered. Fire dampers (fire-stopping) are designed to block the ventilation ducts in order to stop further fire spreading, supply fresh air to the fire sources, and provide for the smoke and other combustion products exhaust. The three valves are normally open, single-cassette with one flap, channel, with an outside drive. The valve body is made of galvanized steel. Along the flap perimeter there is a thermoactive seal that expands under the action of high temperatures and ensures the valve tightness. The flap is made of fire-resistant glass-magnesite. Depending on the fire resistance rating, a flap of different thickness is used. According to the test results, it was confirmed that the valves meet the fire resistance rating declared by the manufacturer.

Key words

ventilation system , fire damper , fire resistance rating , smoke exhaust