The paper presents results of microbiological quality of three drinking water sources – Ratno ostrvo, Petrovaradinska ada and Strand. The following analyses were carried out in 2010: total count of aerobic mesophilic bacteria at 37 deg C, count of organotrophs (categorization according to Kohl), aerobic facultative organotrophs, lipolytic and hydrocarbon oxidizing bacteria. Organotrophic count was determined on low nutritive R2A medium. Enzymatic activity of water was also determined and water was categorized according to index of phosphatase activity (IFA).

This study was performed to investigate the influence of the ozonation process on natural organic matter (NOM) and trihalomethane, haloacetonitrile and chloropicrin precursors in groundwater. The largest reduction in dissolved organic carbon, DOC (up to 25%) and UV 254 values (up to 69%) was achieved using 3 mg O3/mg DOC. Reducing the total organic matter resulted in a reduction of trihalomethanes precursors to 194 micro g/L. On the other hand, when it comes to the precursors of the high priority nitrogenous disinfection by-products, the oxidation of NOM by ozone and the resulting increase in organic matter with a low molecular lead to an increase in the haloacetonitrile precursors compared to the raw water and the formation of chloropicrin precursors.

A contemporary biostability assessment of raw and treated water requires determination of biodegradable organic matter fraction responsible for bacterial growth. BDOC test allows monitoring of bacterial growth by assaying chemical changes in the test-water and thereby determine the content of biodegradable dissolved organic carbon (BDOC). The aim of this study was to optimize the required period for performance of BDOC tests, and to examine the use effectiveness of different biofilm carrier. The results indicate that the BDOC test with sand-inoculation is more effective compared to the anthracite, and recommendations for monitoring of biodegradation process are a period of 3-5 days.

The content of aluminum, boron, chromium, manganese, cobalt, nickel, copper, zinc, arsenic, cadmium, barium and lead was analyzed in raw water and drinking water that is used by the Belgrade Water Supply and Sewage Company. Total of 14 samples were examined from all water treatment plants that are part of the Belgrade Water Supply and Sewage. The measurements were conducted using the inductively coupled plasma-mass spectrometry (ICP-MS) technique. The aim of this research was to examine the effectiveness of the process of drinking water preparation in the existing plants. In all drinking water samples concentrations of the elements were bellow the maximum allowed levels according to the Serbian regulations. Correlation coefficients for the elements, which were analyzed in this paper, show that three groups of elements can be distinguished. Boron, manganese, arsenic and barium are related to each other and probably originate from the same source; copper, nickel and zinc have lower mutual correlation coefficients, indicating a potential common origin; finally, lead, aluminum and cadmium are not in correlation with any tested element.