The results of microbiological analyses of raw water of two water supplies of city of Novi Sad (Ratno Ostrvo and Petrovaradinska Ada) are presented. The sampling was performed monthly during 2008 and 2009. The following parameters were monitored: aerobic mesophilic bacteria count at 37 deg C, organotroph count (water categorization according to Kohl), facultative oligotrophs, lipolitic and hydrocarbon-oxidizing bacteria count. The count of organotrophic bacteria was determined using low nutritive R2A medium. In addition, water was classified according to enzymatic activity of water, expressed as index of phosphatase activity (IFA).

Novi Sad is one of the major consumers of water in the Republic of Serbia. This is why the presence of safe and abundant sources of raw dringing water has been of utmost importance for this city which is expanding urbanistically and demografically. This paper presents major data related, above all, to the capacity of the present water sources in Novi Sad, as well as the results of the analyses considering the possibilities for the expansion of source capacity. Furthermore, the text considers the problem of numerous pollutants which have been polluting water sources and offers possible measures for their efficient protection.

The possibility of applying the process solidification/stabilization for treatment of arsenic containing sludge, obtained after coagulation and flocculation treatment in the preparation of raw drinking water, using lime, cement and lime and cement in the mixture as stabilization agents was examined. Test results showed a high content of arsenic in the initial sample of sludge, above the allowable 41 mg As/kg by the USEPA prescribed for disposal of waste sludge. Performance of S/S process was investigated by two leaching tests, PCLP and DIN 38414-S4 test, which showed the highest efficiency of lime and cement mixture in the removal of arsenic by this procedure.

In order to protect the natural resources used, it is necessary that plant production has such a concept that its influence with the optimization minimizes the required yield. For this purpose it is necessary to adjust the measures taken for the purpose of regulation of water-air regime, especially in the area where land reclamation is applied. The difficult task require harmonization of approaches that are often contradictory, therefore it is necessary to make preparations for the changes in the existing principles of the existing land reclamation practices. These changes reflect primary in the rational use of resources that could result in the protection and improvement of biodiversity and therefore stable ecosystem in the agricultural area.

The aim of this paper is to present the current distribution of the species Corbicula fluminea and Corbicula fluminalis with new findings in Serbia. During the investigation performed from 1998-2008, these taxa were detected at 19 localities. It is noted that C. fluminea is well adapted to particular aquatic ecosystems, whereas C. fluminalis seems to be rare in Serbian waters. Wide distribution of alien clams, according to our results, showed that heavily modified main water ways are suitable recipient areas for introduction and adaptation of allochthonous organisms.

The paper presents the results of aquatic macroinvertebrates community analyses of the Milesevka river (Lim river watershed; Sava river basin) with aim to evaluate saprobiological status. Sampling was carried out on five localities during 2005. A diverse community (62 taxa) has been recorded during the investigation. Results of saprobiological investigation indicate satisfactory water quality, which is, according to national legislative, within 1st and 2nd quality class.

This paper presents the results of assessment of dredging activities at the Romanian side of the channel on the quality of water and sediment in the Begej channel (in Serbia). Sediment monitoring results have pointed to the increasing content of metals in surface sediments, as well as increased concentrations of some metals (Cd, Ni and Cr) compared to the period from 2008. Results of the water quality after the dredging at the Romanian side shows low metal concentrations, which is probably caused by coprecipitation of metal in the iron in forms of amorphous and hydrated oxide. Monitoring of water and sediment should be conducted continously through the year in order to follow the trend of sediment and water quality and targeted when we know the exact time of some of the activities in the channel.

The city of Novi Sad uses groundwater as drinking water source. For this purpose only water from Danube alluvium is used, and the water is abstracted at three sites. The Danube water and sediment quality in the zone of the drinking water sources is of great importance, as the river Danube recharge alluvial aquifer. The microbiological quality of these environments was monitored, in order to determine their influence on drinking water quality. The water characterization was carried out using sanitary and ecological microbiological parameters of Danube water and sediment.

This study was performed to investigate the efficiency of Fenton's process (FP) for removing natural organic matter, in particular the main disinfection by-products precursors. In order to determine the optimal reaction conditions of the process, the influence of pH, mixing speed and reaction time were investigated, as well as the influence of initial concentration and the molar ratio of Fe2+ and H2O2. The best results in terms of reducing the DOC content (by 82%) were achieved under pH 5, 30 rpm, reaction time of 15 min, Fe2+ concentration of 0.25 mM and a molar ratio of 1:10, and in terms of reducing trihalomethane and haloacetic acid precursors (by 98-99%) under a Fe2+ and H2O2 molar ratio of 1:20.

The paper presents aquatic macroinvertebrate community at four investigated localities of the Gradac river. Sampling was carried out during 2003 and 2006. Community structure and composition, together with field data, were used to estimate the water quality status of the river. A total of 87 taxa have been recorded. Insects were found to be the most diverse component, especially Ephemeroptera. Insects were dominant in the regard of the quantitative structure of the community, as well. Recorded community indicates good water quality, ranged between oligosaprobic and beta-mesosaprobic status (1st-2nd class according national classification scheme).