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.

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.

Coagulation and flocculation can be efficiency applied in drinkling water treatment, in order to remove natural organic matter (NOM). However, in the experiments presented in this paper, the water used is very rich in NOM, and required investigations of additional processes. In order to increase the efficiency of coagulation and flocculation processes in removing NOM from groundwater, the following processes were investigated: adsorption on powdered activated carbon (5-30 mg PAC/l) and preozonation with applied ozone doses of 1.1-6.3 mg O3/l. The parameters used to evaluated the changes in NOM content during the experiment were: KMnO4 consumption, UV absorbance at 254 nm, pH and turbidity.

Processes in the aquatic environment have been intensively explored in recent years, especially sorption processes. In this study, the sorption behavior of benzothiazole (BT) and 2-methylthiobenzothiazole (MTBT) was investigated, on geosorbents with different contents of organic carbon (OC). For both geosorbents and selected organic compounds, nonlinear isotherms were obtained. BT had the greatest degree of nonlinearity on the geosorbent with a higher content of OC, whereas the greatest degree of nonlinearity for MTBT was obtained on the geosorbent with lower OC content. From a comparison of logKoc for selected concentrations, it can be concluded that the geosorbent with the higher OC content has a higher affinity for the sorption of selected compounds.

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.

Within the pollutant analysis in sediments the total organic carbon (TOC) content is determined, as well as nutrients such as nitrogen and phosphorus. In addition to this form carbon may be present as elemental or inorganic ones, as the crucial issue for sample preparation. Total phosphorus content was determined after sample digestion with sulphuric and perchloric acid. Organic nitrogen values were determined according the Kjeldahl method. Concentrations of TC, TOC, TIC, total P, organic N and total N in river Tisza sediment samples from sites Martonos, Novi Becej and Titel during 2004 and 2005 were presented.

This work considers the effect of the ozonation process on formation of aldehydes in groundwater pretreated by aeration/preozonation (2.0 g O3/cubic meter) and coagulation with polyaluminium-chloride (5 and 10 g Al/cubic meter). Experiments were carried out on a semi-industrial plant of 2 cubic meter/h capacity. It was found that in the course of ozonation NOM content shows a decrease (up to 54% TOC), whereas content of aldehydes increases by 1.0-14 microgram/L, depending on the water pretreatment and applied ozone dose. The most prominent changes in specific aldehydes content during ozonation were detected after applying ozone dosages of 0.5-2.0 mg O3/mg TOC.

Conventionally treatment method in potable water preparing, such as coagulation/flocculation, sedimentation and filtration has been shown reduction in efficiency of the contents of natural organic matter. There has been developed many alternative NOM removal technologies, in recent years. It has been made significant research effort in finding optimal drinking water treatment for NOM range reduction prior disinfection, that can minimise the formation of disinfection by-products and reduce the residual required to control bacterial regrowth in the distribution system, which is a consequence of coagulant with humic matter settling. Conventionally treatment modified by MIEX resin appliance meet the current water quality standards, with significant reduction of the coagulant quantity.