Arranging the discharge and treatment of urban wastewater in small wastewater treatment plants in areas of dispersed population is an obligation of the facilities’ owners, whereby the legal framework at the level of EU member states for this area was regulated in 2000 with Water Framework Directive. Among a multitude of existing technologies for urban wastewater treatment in areas outside agglomerations, nature-based and green treatment technologies are becoming increasingly recognisable as appropriate for an efficient protection of the natural and living environment. The purpose of this master thesis is to evaluate the operation of an innovative pilot small wastewater treatment plant, which is nature-based and resistant to external environmental factors and is intended for treating the wastewater of individual residential buildings. In order to evaluate the operation of the pilot small wastewater treatment plant we carried out sampling and measurements of physico-chemical parameters at the plant’s inlet and outlet from December 2018 to April 2021. The pH value, electrical conductivity, temperature, dissolved oxygen content, total suspended solids, COD, BOD5 were measured in the urban wastewater, and the impact of weather conditions was monitored. We measured the consumption of drinking water and thus obtained the hydraulic load. We carried out measurements of the hydraulic retention time and calculated the average value and the effect of the treatment on total suspended solids, COD, BOD5 and electrical conductivity. Standard methods were applied in our research. A 70% average effect of treating total suspended solids was achieved in the pilot small wastewater treatment plant with filtration medium in first 18 months, 74% for COD and 85% for BOD5. In the 28 months of COD monitoring we achieved even a higher value, 77% efficiency on average. We measured a 7-hour long actual hydraulic retention time. The average hydraulic load of pilot small wastewater treatment plant was 396 L/day. The external environmental factors and fluctuations of the hydraulic and pollution load did not affect the efficiency of the plant’s operation. Urban wastewater treatment at the pilot small wastewater treatment plant turned out to be an efficient nature-based solution for urban wastewater treatment in areas with dispersed population, since by statistically processing and examining the results of the measured parameters we have proven that the process of secondary treatment is sufficiently efficient in order to ensure the compliance with the prescribed limit values for release into the environment. The stability of parameters at the outlet is evidence of the robustness of the plant’s operation, since high treatment efficiency over 70% of the measured parameters were achieved. It would be reasonable to upgrade the research by carrying out measurements of nutrients and microbiological parameters with which we would be able to establish the plant's potential for re-use of treated urban wastewater for irrigation.
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