MATHEMATICAL MODELLING OF DRAVA RIVER SECTION 000+543 - 069+118 - WATER QUALITY

U programskom paketu MIKE 11 izrađen je jednodimenzionalni model rijeke Drave na dionici od 00+543 rkm do 69+118 rkm sa svrhom analize kakvoće vode rijeke Drave. Izrađena je pojednostavljena verzija promatrane dionice rijeke Drave bez pritoka. Za uzvodni rubni uvjet uneseni su protok i parametri kakvoće vode (otopljeni kisik, temperatura, amonijak, nitrati, otopljeni i partikularni fosfor te petodnevna biološka potrošnja kisika BPK5), na nizvodnom presjeku definiran je vodostaj dok je uvjet vezan za kakvoću vode ostao otvoren. Kao dio ulaznih podataka također su određene koncentracije spomenutih parametara kakvoće vode na uređaju za pročišćavanje Belišće na stacionaži 54+373 rkm i oni na položaju direktnog ispusta otpadne vode kod Osijeka sa stacionažom 14+580 rkm. Modelirana su dva scenarija. Za scenarij 1 uneseni su potoci i parametri kakvoće vode na pozicije tri prema dogovoru odabrana kišna preljeva (od ukupno osam u gradu Osijeku). Analizirano je kako otpadna voda, puštena preko preljeva za vrijeme kišnih razdoblja u trajanju od 30, 60, 120 i 240 minuta, a povratnim razdobljima od 1, 3, 5, 10 i 20 godina, utječe na kakvoću vode rijeke Drave. Scenarij 2 predstavlja ekstremnu situaciju: kvar na uređaju za pročišćavanje Belišće i njegov prestanak rada u trajanju od dva dana. Pretpostavljeno je da se tokom tog razdoblja u rijeku Dravu ispušta nepročišćena voda sa uređaja za pročišćavanje Belišće. Nakon modeliranja analizirane su dobivene koncentracije otopljenog kisika O2, BPK5, i amonijaka NH3. Za prvi scenarij konstruirane su ITP krivulje za svako povratno razdoblje. Rezultati su pokazali kako se koncentracije, nakon prvotnog pada/skoka, razmjerno brzo stabiliziraju na stanje prije kišne epizode. Scenarij 2 isto je ukazao na sposobnost samopročišćavanja rijeke Drave. Tokom kvara, koncentracije analiziranih parametara naglo su se povećale u skladu sa vrijednostima parametara nepročišćene vode, ali odmah po popravku uređaja također dolazi do vraćanja parametara na prvotnu kakvoću vode rijeke Drave. Diplomski rad napravljen je u suradnji sa Građevinskim fakultetom u Bratislavi u okviru Erasmus+ programa za mobilnost studenata.One-dimensional model of the Drava River between chainages 00+543 km and 69+118 km was created in 1D modelling software MIKE 11. Compared to the Drava River, the created model was simplified, without any tributaries, with the purpose of water quality analysis. Inflow boundary was specified upstream as well as water quality parameters (dissolved oxygen DO, temperature, ammonia, nitrates, dissolved and particular phosphorus and biochemical oxygen demand BOD). Water level and open boundary conditions were specified at the downstream end. Water quality parameters mentioned earlier were also defined at wastewater treatment plant (WWTP) Belišće (chainage 54+373 km) and wastewater outlet near Osijek (chainage 14+580 km) Two types of scenarios were modelled. For scenario 1, discharge and water quality parameters were specified for three combined sewer overflows (CSO) in Osijek. The purpose of this scenario was to analyse wastewater impact on the Drava River during the rainfall with the duration of 30, 60, 120 and 240 minutes and the frequency of 1, 3, 5, 10 and 20 years. Scenario 2 presented an extreme situation: 2-day failure of WWTP Belišće. It was assumed that during that time raw untreated water would be discharged into the river. After running the simulation, resulting concentrations of DO, BOD and ammonia were analysed. IDF curves were constructed for scenario 1. According to the results, concentrations of BOD and ammonia rapidly increase with the beginning of the rain but stabilize around concentration value close to primer river quality shortly after the rain stops. At the same time, DO concentrations rapidly decrease but stabilize too. As well as scenario 1, scenario 2 also pointed out the self-purification of the Drava River. During the failure, parameter concentrations promptly increased according to concentration values of untreated wastewater, but immediately after fixing WWTP they went back to pre-failure values. This Master’s Thesis was created in collaboration with Faculty of Civil Engineering at Slovak University of Technology in Bratislava during Erasmus+ Mobility Programme