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Assessment of the Influence of Evaporation and Evapotranspiration on the Volume of Sludge Accumulation in the Sludge Drying Beds

Velychko Svitlana, Dupliak Olena

Journal of Ecological Engineering

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2021

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Vol. 22, nr 2

63--69

EN

At present, the sludge drying beds of the Kyiv wastewater treatment plants are operated as a sludge accumulator in an emergency mode, practically without free volume. The purpose of the work was to determine the equation for the evaporation losses calculation from sludge drying beds and the required free volume for sludge accumulation for the next 7 years. The required free volume was calculated using the water budget method which takes into account evaporation from the water surface and evapotranspiration during the vegetation. The total losses from sludge drying beds is 1076 mm/year in normal year and is 920 mm/year in a cold year. The required free volume was calculated considering the trend of increasing average temperature over the last decade and considering the significant environmental risk. A correction was made for one unfavourable year with cold summer and warm winter and an additional rain rate of 1% probability. The additional free volume required is 3.24 million m3 for 7 years if all three sludge drying beds are operated.

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Hydrological Assessment of the Water Replenishment Possibility of the Uzh River Urbanized Floodplain on the Example of Bozdosky Park, Ukraine

Velychko Svitlana, Dupliak Olena

Ecological Engineering & Environmental Technology

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2021

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Vol. 22, iss. 4

30--38

EN

Over the last twenty years, the number of projects aimed at river restoration and rehabilitation increased significantly. In the city it is impossible to provide full river restoration, but at the same time it is possible to create a comfortable natural environment both for flora and fauna and for the citizens. In our work it was assessed the possibility of the floodplain restoration by the water replenishment of the dry old riverbed during the vegetation season on the example of the river inside the city. The simulation of the current state allowed to verify the main parameters of the model with the existing observations of the water levels in the river and lake and water levels in the wells located in the park. The river – floodplain interaction was simulated: floodplain was separated from the river by the flood control dyke, the water replenishment of the lake and the old riverbed was due to seepage (current state); the connection of the floodplain with the river by the culvert and the replenishment of the lake and the old riverbed with surface river water. The simulation showed that the lake isolated from the river is filled to a depth of not more than 0.5 m, the old riverbed is filled with water only during spring floods. The water balance calculations of the lake showed that in the conditions of isolation from the river, the lake volume is significantly affected by precipitation and evaporation from the lake water surface area. The connection of the lake with the river surface water reduces the impact of the vertical components of the water balance, at the same time increases the seepage losses from the lake because of the water level raising. The connection of the river with the floodplain makes it possible to replenish the old riverbed and the lake in the mean year, but in the dry years the water level in the lake does not allow to replenish the old riverbed during the vegetation season. Calculations showed that to be able to keep the constant water level in the lake and old riverbed, it is necessary to increase the water level in the lake.

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Assessment of the Influence of Mountain Flood Control Reservoir Operation on the Floodplain Stability During an Extreme Flood

Velychko Svitlana, Dupliak Olena

Ecological Engineering & Environmental Technology

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2021

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Vol. 22, iss. 1

31--38

EN

Construction of Mountain Flood Control Reservoir is an effective method of flood protection on mountain rivers. The Flood Control Reservoir works under the extreme condition of rapid water level rising and falling. The regime of intensive water level change affects the floodplain stability. Simulation of water penetration into the depth of soil, formation of the seepage curve under transient conditions during water rising and falling was carried out by Midas GTS NX software. A slope stability analysis was conducted for the floodplain of the Irshava River, flood of 1% probability (return period of 100 years) was assumed. Numerous simulations showed that the influence of the mechanical and hydraulic properties of the soil depends on the slope angle. The stability of the floodplain slope depends on the cohesion and hydraulic conductivity for steep slopes greater than 26°; if the slope is less than 26°, the stability is considerably dependent on cohesion, and the hydraulic conductivity practically has no influence. Thus, floodplain with the angle greater than 26°, additional geological surveys are required to determine the soil composition, mechanical and hydraulic properties for each layer. For the slopes lesser than 26° it is sufficient to determine the mechanical and hydraulic properties for the engineering and geological elements of soil, according to the national building regulations. Numerical simulation allows reducing the total volume of geological survey by minimizing survey of the slopes with an angle of less than 26°, which is 30% of the floodplain perimeter. The slope stability analysis showed that the slopes with the angle greater than 26° require stabilization structures in the lower part of floodplain before the Mountain Flood Control Reservoir construction.