Hlushchenko R. Improvement of the rainwater drainage system using ''green'' structures

The dissertation is dedicated to solve the problem of preventing flooding of urban areas using the technology of "green" structures, which is extremely relevant in today’s conditions for Ukraine and the world, in particular for the post-war reconstruction of infrastructure and construction objects. The analysis of literary sources showed that "green constructions" are a promising technology for rainwater management. On the basis of the conducted analysis, the concept of natural management of rainwater run-off in urbanized areas was created. The concept defines the location of each element involved in the collection and retention of rainwater. In order to effectively reduce rainwater flows, three models of ZinCo "green roof" of different systems were investigated. "Sedum Carpet" Florafrain FD25, "Scented Herbs" Florafrain FD40 and "Roof Garden" Florafrain FD60 with an area of ​​1 m². The first model showed the fastest water flow – 1.63 dm³/day. The second model retains water the best – 0.62 dm³/day. Therefore, it is recommended for rainwater management. For the reuse of rainwater run-off from the "green" roof, field studies of run-off from the green and ungreened roofs of the residential complex "Respublika" were performed. By all indicators, the water from the "green roof" meets the standards for drinking water. An innovative system of the green channel has been developed for direct, fast and uniform collection of rainwater from roadways with subsequent cleaning. Its layers are a FEM parking grid, crushed stone-sand mixture fraction 0-5 mm, fine-grained natural sand ρ = 1.63 t/m³, crushed stone fraction 10-20 mm, perforated PVC drainage pipe ø100-200. Experimental studies of the channel were performed by pouring the system with water at the rate of 8 dm³ per linear meter. When pouring water in 10 seconds, the water level reached only 30 mm. Experiments have shown that the channel passes these 8 dm³ of water per linear meter in 4 minutes. With the rainfall regime of the city of Kyiv for 2021-2022, the efficiency index of the channel is 2.7...4.33. For Povitroflotskiy Avenue in Kyiv, a volume of rain of 1.28 mm/min will be absorbed by channels on both sides of the roadway in less than 39 seconds. "Green" parking spaces have a significant potential for absorbing rainwater, and in addition, reducing the temperature – combating the heat island effect. The total area of ​​officially recognized parking spaces in Kyiv reaches 215 925 m². The total absorption of water by these parking spaces is 6,677 m³ of rainwater, which currently loads the city's storm sewerage. The practical application of the developed solutions is shown on the example of the "green" roof project with an area of ​​350 m² on the main building of the Kyiv National University of Construction and Architecture. We analysed the amount of precipitation in the city of Kyiv for 2022. The maximum amount of precipitation in the warm period of the year is 63.1 mm in September. The “Fragrant Herbs” system by the Zin-Co company was adopted with a specially selected set of plants, moisture-retaining mats and drainage elements Floradrain® FD40. Areas of green zones of 250 m², which retain water, and areas of pedestrian areas of 100 m² with a permeable coating, from where water is diverted. At maximum rainfall, in the absence of water accumulation, 10 % of it will not be retained and will enter the storm sewerage. Two options are offered: create reversible overtime watering. At the same time, the water will again pass through the substrate and plant roots, which should clean it of microorganisms and formed chemical pollutants and extend the storage period in the tank. This will require pumps. Another strategy is to use water for toilets on lower floors, which allows taking advantage of hydrostatic pressure for self-flow. Two toilets empty the tank in 10.4 days. Since the term of storage of water in the tank without deterioration of its quality is 14 days, such a decision is justified. Also, the practical application of the research results is shown on the example of a project with the installation of storage tanks for the accumulation of rainwater from the roof in the basement of an apartment building in the "Faina Taun" residential complex in Kyiv with the aim of transferring the irrigation water supply to a secondary source – wastewater from the "green" roof . It is shown that for the first stage of construction with a total roof area of ​​4208 m², it’s enough to install 8 tanks of 6 m³. A system of irrigation water supply with power from storage tanks and central water supply with priority by tanks has been developed. A comparison with the readings of the meter showed the possibility of saving up to 90 % of the costs of using centralized water supply.