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.

Due to development in the science, especially in the area of biodegradation, it becomes clear that different species of aerobic and anaerobic bacteria are indigenous in the ground water. Due to changed condition in ground water, like infiltration of petroleum hydrocarbons, indigenous bacteria start to react and are involved in different processes of natural biodegradation. Also, great contribution of understanding how bacteria functionating in ground water is given from the field of well regeneration due to consequences of biofouling and biologically induced corrosion. In this article several natural processes related to bacteria are analyzed and its importance and distribution in ground water is shown.

The microbiological quality of the groundwater was monitored by determining relevant physiological groups of bacteria (organotrophic bacteria) which are indicators of water organic pollution. Standard high nutritive medium (Nutrient Agar) and low nutritive medium (R2A agar) were used. The enzymatic activity was also estimated based on IFA determination (index of phosphatase activity). According to the number of organotrophic bacteria and categorization by Kohl (Kohl, 1975) water is generally classified in category II. IFA showed variation of water quality, which varied from polluted to very pollute. The results showed organic pollution of groundwater and confirmed the sensitivity of enzymatic methods. In addition, cultivation methods confirmed superiority of low nutritive media.

Groundwater from the middle Banat region (Serbia) which is used as a drinking water supply for Zrenjanin town contains a high amount of natural organic matter and a high content of arsenic. In this study a pilot-scale system was used to investigate the influence of different ozone doses (0.4-0.9 mg O3/mg DOC) during a pre-ozonation process on NOM removal by coagulation. Ferric chloride coagulant was chosen at a dose of 100 g/cubic meter, as a traditional coagulant which can also help in arsenic removal. The obtained results indicate that an ozone dose of 0.4 mg O3/mg DOC has the best influence on structural changes of NOM. The coagulation process with ferric chloride as coagulant had a significant influence on the arsenic content of the water, with the measured values in the water after coagulation in all three investigated treatment trains being below 10 microgram/l, which is the standard MCL in Serbian legislation.

The stable isotope content of hydrogen (2H/1H), carbon (13C/12C), nitrogen (15N/14N), and oxygen (18O/16O) in surface water (the Sava river and channels) and groundwater (Ranney wells) were determined in Belgrade (Serbia) during July 2008. Detailed evaporation calculation has estimated that fraction of water loss to be between 10 and 20% in the channels using the local meteoric water line and the local evaporation line. Carbon-13 content in dissolved inorganic carbon is distinguished between surface water and groundwater indicating different evolution pathways of carbon. Based on carbon and nitrogen isotopic composition and C/N ratios, sources of inorganic carbon and of organic matter in analyzed waters are discussed.

The paper presents the results of laboratory research and application of continuous electro-coagulation and electro-flotation (ECEF) to remove natural organic matter (NOM) from groundwater in the treatment of drinking water. The highest NOM removal efficiency for current density of 5.78 mA/ cm square according to UV254 absorbance and dissolved organic matter (DOC) was 77% and 71% respectively. The specific energy and aluminum electrode consumption was 2.01 kWh/cubic m, 80 g Al/cubic m, respectively.

Quality of groundwater from aquifers used for water supply in the town of Zrenjanin, does not meet the drinking water quality requirements. Among the basic problems are the high content of natural organic matter and arsenic, but also sodium and boron. This paper presents one of possible alternative of technological solutions for drinking water preparation in Zrenjanin. Research has lasted three years. The paper presents a only an outline of the drinking water preparation processes.

Content of arsenic in groundwater form south Banat which are used for water supply of local population was determined. 228 wells were analyzed, and for arsenic determination was used atomic apsorption spectrometry - graphite furnace technique (Perkin Elmer Analyst 700). Arsenic is detected in concentrations over 10 microgram/l in several locations: Pancevo (water supply Filter Stanica, Gradska Suma, OB, and in part of water supply Sibnica), Kovin, Dubovac, Idvor, Veliki Gaj, Glogonj, Sefkerin and part of Sakule. The lowest concentrations of arsenic are detected in the territory of Deliblatska Pescara and municipalities of Vrsac and Bela Crkva.

In the 21 century drinking water of acceptable quality should be available to every person. Numerous investigations are on-going worldwide around the world, to develop innovative and cost attractive approaches for production of high quality drinking water. To allow application of new treatment technology in practice, pilot testing under field conditions are required. Groundwater used for drinking water productions in the Subotica municipalities (Serbia) contains elevated concentrations of arsenic, iron and ammonia, and therefore provided a good basis for continuation of research of UNESCO-IHE, the Netherlands Institute for Water Education, that has been developing innovative water treatment technologies specifically in the field of groundwater treatment and specifically arsenic removal. Objective of this project presented in this paper were to test under field conditions IHE ADART, the innovative adsorptive arsenic removal technology. The pilot project has demonstrated that in addition to conventional approach based on coagulation and break-point chlorination, there is and alternative treatment approach based on biological ammonia removal and adsorptive removal of arsenic that could be economically and ecologically attractive.