Impact of natural and climatic factors on the efficiency
of open wastewater treatment facilities operation

Summary

The problem associated with the impact of natural and climatic factors on the efficiency of wastewater treatment in open treatment facilities is considered. The analysis of methods for calculating the basic units for mechanical treatment (primary settling tanks) and biological treatment (aeration tanks and secondary settling tanks) of municipal wastewater is presented. It is indicated that at the design stage of the complexes it is important to calculate correctly the temperature of the incoming wastewater. The long-term practice of operating municipal wastewater treatment facilities has shown that with a long retention time in open facilities waste liquid can be cooled during the cold period of the year and heat up to about 1.5–6 °C during the warm one. In the first case this negatively affects the processes of sedimentation of suspended solids in settling tanks and oxidation of organic substances in aeration tanks; whereas in the second case this negatively affects the saturation of mixed liquor in aeration tanks with oxygen resulting in a reduced treatment level. The purpose of the work was to develop recommendations that allow at the design stage of wastewater treatment facilities to correctly calculate the temperature of waste liquid in open structures for a certain project that has specific climatic conditions. To achieve this goal the data of laboratory and in-process control of the operating wastewater treatment complexes were analyzed. A theoretical analysis of the currently used methods for designing wastewater treatment facilities has been made; research has been carried out at the operating facilities. Mathematical models widely used in heat engineering have been studied to determine heat losses from the open surface and through enclosing structures as well as the heat input from solar energy and exothermic reactions.

Key words

aeration tank , sewerage treatment facilities , evaporation , primary and secondary settling tanks , wastewater temperature , cooling , evaporation , convection heat exchange

Microclimate in a heat sink of a nuclear power plant and its performance

Summary

The results of assessing the interaction of a heat sink at a nuclear power plant with the environment are presented. The impact of the microclimate changes on the performance of the heat sink is substantiated. Heat emissions into the environment from evaporation, convective and radiant heat fluxes as well as climatic indicators: temperature and pressure of saturated steams, wind speed (at the weather cock height), total cloud cover, aggregate values of average monthly and average annual precipitation, number of foggy days were considered as basic performance indicators. Routine observation series for 20 years (1990–2010) taken from the hydrometeorological survey technical reports at the Smolensk weather station located at the distance of 144 km from the Smolensk nuclear power plant as well at the Ekimovichi meteorological station (7 km from the Smolensk nuclear power plant) and at the meteorological station of the Smolensk nuclear power plant made the basis of the analyzed data base. The assessment of the performance indicators of the heat sink was carried out according to the nuclear power plant process design (RD 153-34.2-21.144-2003). For the given geotechnical facilities three options of the conditions determined by the meteorological data obtained at the meteorological stations of the Smolensk nuclear power plant, Ekimovichi and Smolensk were considered. The impact of the microclimate was determined by the difference in the heat loss parameters: heat release into the environment from evaporation and convective heat exchange. The analysis of the calculations of the seasonal thermal conditions of the heat sink showed their sensitivity to the microclimate changes and seasonal behavior; this fact shall be taken into consideration when undertaking commitments to increase the electric power generation.

Key words

nuclear power plant , heat sink , convective and radiant heat exchange , evaporation , hydrometeorological survey