IZBOR MIKROLOKACIJE ISPUSTA IZ PPOV VELIKO SELO U FUNKCIJI UTICAJA NA KVALITET VODE U RECIPIJENTU

The paper presents and analyzes the impact which the discharge of treated and untreated wastewater from the Central sewerage system of the City of Belgrade has on the recipient - the Danube at the location of the Veliko Selo WWTP. The microlocation of the discharge from WWTP was selected based on the obtained results. The Central sewerage system of Belgrade includes about 85% of the sewerage network and currently serves more than 1,250,000 inhabitants. The hydrological data, namely the flow and level at the characteristic profiles of the Danube (minimum mean monthly flow for a 95% probability of occurrence) were collected and used to create the 2D hydraulic model RMA2. Data on the quantity and quality of treated and untreated wastewater in the rainy and dry mode of operation of the combined sewerage system were also collected and processed, and the load of wastewater with polluting substances (expressed using BOD5) was defined for the future period of operation of the WWTP (year 2041). This was then used as input data for the mathematical model of pollution transport and transformation in the recipient Danube - RMA4. A coupled 2D hydrodynamic-transport model RMA2/RMA4 was created, which simulated three variants of the discharge of treated and untreated wastewater in the dry and rainy periods for the future state (year 2041): 1. Riverbank discharge into the Dunavac, 2. Riverbank discharge into the Danube and 3. Bottom discharge in the middle of the Danube bed. It was concluded that the optimal outlet location is variant no. 2 – coastal outlet into the Danube. The discharge into the Danube proved to be a more favourable variant than the outlet into the Dunavac from the point of view of protecting the aquatic environment and meeting the regulatory standards as well as of the mixing zone that is formed downstream of the effluent outlet into the Danube, which has significantly smaller dimensions compared to the mixing zone in the Dunavac. The discharge into the middle of the Danube bed is an even more favourable option than the riverbank discharge into the Danube, but it is more complicated from the construction-technical-economic point of view and the provision of navigation on the international waterway.