THE ASSESSMENT OF THE SURFACE WATER QUALITY USINGTHE WATER POLLUTION INDEX: A CASE STUDY OF THE TIMOK RIVER (THE DANUBE RIVER BASIN), SERBIA

摘要

The Timok River (202 km long, 4547 km~2 basin area) is located in East Serbia. It is a right tributary of the Danube River and one of the most polluted watercourses in Serbia. On the basis of the data provided by the Republic Hydrometeorological Service of Serbia, the paper presents an analysis of water quality and pollution using the combined physico-chemical WPI index (Water Pollution Index) calculated for two periods - 1993-96 and 2006-2009 at four hydrological stations: Zajecar-Gamzigrad (Crni Timok River), Zajecar (Beli Timok River), Rgotina (Borska Reka River) and Cokonjar (Timok River). The following parameters were taken into consideration: dissolved O_22, O_22 saturation, pH, suspended sediments, Five Day Biochemical Oxygen Demand (BOD_5),Chemical Oxygen Demand (COD_(Mn)), nitrites, nitrates, orthophosphates, ammonium, metals (Cu, Fe, Mn, Hg, Ni, Zn, Cd), sulphates and coliform germs. The average WPI values were calculated for the observed periods based on the comparison of the annual average values of the listed parameters and defined standard values for the I water quality class (according to the Regulation on the Hygienic Acceptability of Potable Water of the Republic of Serbia). The highest pollution degree was recorded in the BorskaReka River, where heavy metal levels (especially manganese and iron) were significantly increased. These metals are indicators of inorganic pollution (primarily caused by copper mining). Also, increased values of the organic pollution indicators (ammonium, coliform germs, Five-Day Biological Oxygen Demand - BOD_5) in the Borska Reka and the Timok rivers are the result of uncontrolled domestic wastewater discharge.