INDICATORS OF OXYGEN DEMAND IN THE ECOSYSTEM OF THE DANUBE IN SERBIA

Actual problems of pollution of aquatic systems require the determination of the ecological status of the Danube, stressing the importance to the realization of the principles of sustainable water management, Directive 2000/60EC, as well as the preservation of the environment. The aim of this paper is to monitor oxygen concentration demand by measuring stations along the river, and use these data to determine the ecological status of the Danube in Serbia. Indicator of the oxygen regime in the watercourse involves monitoring the concentration of biological oxygen demand (BOD-5) and ammonium ions (NH4-N), by monitoring state of the environment based on the load of surface water with organic matter and ammonium, respectively (Regulation on the national list of environmental indicators, "Official Gazette of the RS", no. 37/2011). The paper used the Ministry of Agriculture and Environmental Protection, Agency for Environmental Protection of the Republic of Serbia water quality data for the year 2012, obtained from ten hydrological measuring stations on the Danube. Mean annual concentrations values of two indicators of oxygen demand, calculated for the year 2012, are BOD-5 = 1.93 mg/L and the NH4-N = 0.08 mg/L, respectively. Comparative analysis, based on the values of these environmental indicators, showed that the water quality of the Danube in Serbia fits high ecological status or class I surface waters. Generally, it is necessary to perform monitoring and analysis of other environmental indicators in order to assess conditions of the functioning of the Danube ecosystem in Serbia.