| Abstract [eng] |
SUMMARY Assessment of water quality in the Venta River based on macrozoobenthos Vaidotas Sivickas Water is one of the most significant natural resources available in Lithuania. Unlike in many countries around the world, Lithuania does not have its shortage and water quality and the condition of aquatic ecosystems play a very important role in the economy and human well-being, and require strict control. Research goal: evaluating Venta River water quality above and below wastewater treatment plants in Kursenai and Mazeikiai. The master thesis focuses on identifying groups of macrozoobenthos organisms and assessing the water quality and management of the Venta River based on them. The research aims to 1) determine the diversity of macrozoobenthos in the Venta River and to assess water quality by DUFI method; 2) compare the obtained results with the researches performed in the Venta River by the same method during the period of 2008-2017 with the results of the Merkys River research; 3) use bioindication methods to evaluate the impact wastewater treatment plants in Kursenai and Mazeikiai have on water quality. The research was performed using the DUFI test method for the identification of organisms, later assigning them to the appropriate group, according to which water quality is decided. The macrozoobenthos study was based on LAND 57-2003 “Macrozoobenthos study methodology in surface water bodies”. Following the DUFI test in the Venta River, the most frequently detected were the macrozoobenthos organisms belonging to the first indicator group (IG1), which corresponds to the DUFI 4 index, fauna class 3, regardless of the sampling time and test sites, mean that the water quality is average. Comparing the results of the study with the data from 2008-2017 at the outlets of the Kursenai and Mazeikiai wastewater treatment plants, the situation is similar and corresponds to the value of 4 DUFI, which represents the average fauna class, thus the water quality remained unchanged. According to the data of the study, the water quality of the Venta River is slightly better at the beginning of the Kursenai and Mazeikiai wastewater treatment plants compared to the water at the end of the wastewater treatment plants at both cities. A DUFI value of 3 and a DUFI value of 4 were determined at the beginning of the wastewater treatment plants at Kursenai. Thus, wastewater treatment plants are not the main polluters of the Venta River. While taking research samples, it was observed that the river banks near Silenai are muddy, overgrown with macrophytes and bushes. One of the recommendations is the removal of macrophytes from the coast. In the riverbeds, macrophytes function as a natural biofilter and absorb nutrients dissolved and suspended in water, partially absorbing heavy metals, fats and oil products (Ventos upes pakrančių Kursenu mieste..., 2014). Removing macrophyte biomass at the end of vegetation can significantly reduce river pollution and improve water quality. |
