The work considers the effect of the ozonization process on the change of contents of natural organic matter (NOM) and formation of byproducts in the groundwater pretreated by preozonation (2.0 g O3/cubic m) and coagulation with polyaluminium-chlorosulfate (5 and 10 g Al/cubuc m). Experiments were carried out on a semi-industrial plant of capacity of 2 cubic m/h, using groundwater with a high content of NOM (5.1 mg/l TOC). It was found that in the course of ozonization NOM content shows a decrease (18-64%), as well as the potential of formation of trihalomethanes, PFTHM (12-59%), whereas content of aldehydes increases by 3.0-7.7 microgram/l, depending on the water pretreatment and applied ozone dose. It was found correlation between specific aldehyde content and decrease of the specific PFTHM (r=0.815-0.998).

New type of ozone generator based on barrier discharge was applied for removal of phenol from water under laboratory conditions. Three water samples with initial concentration of phenol of 6.0 mg/L were studied. In the experiment with distilled water containing phenol, 98.9% of phenol was removed (93.3% during the ozonization). Under similar conditions two different water samples from river Danube were used. In these cases, 76.7% and 80.0% of phenol were removed, respectively. In all experiments, water samples containing phenol passed only once through the ozonizer. It is reasonable to assume that better purification could be obtained with several passes of water through ozonizer and/or by optimization of the process (adjusting concentration of ozone, ozonization time, water flow, etc.).

The paper presents main recommendations for monitoring groundwater from the aspect of the EU Water Framework Directive. It is concerned with some basic notions of monitoring of quantitative and chemical state of groundwater. It is pointed out that the network of gauging stations must be planned for every catchment area, to ensure a holistic and all-encompassing survey of the chemical state of groundwater, and allow detection of long-term anthropogenic effects of pollution. In addition to usual numerical and graphical presentation, the state of groundwater quality should be also presented by colours: good state - green, bad state - red.

The diffusion of erosive processes in Serbia and frequency of torrential floods are the factors of degradation of environment. Communities in Serbia are obliged to make Plans for announcement of erosive regions and for protection by torrential floods on water courses out of regular system of defense. An example of Belgrade is presented in this paper, where the Plans for announcement of erosive regions and defense by torrential floods were carried out. These documents are the basis for water protection and usage of natural resources on the concept of sustainability.

The results of the examination point out on heterogenity of the phytoplankton community. The presence of 212 taxa has been noted. In the way of quality the green algae are dominant. In all the aspects of the quantitative analysis the domination of Bacillariophyta has been noted, first of all the centric forms. The amount of nutrients on the locality of border with Hungary is considerable, thus during low water and high temperature, the intensive algae development is usual.

One-year monitoring program was organized with the aim to assess the quality of sediment and water in some protected areas in Vojvodina regarding metal content (Cr, Cd, Cu, Ni, Pb, Zn, Hg) in them. Water was class 1/2 according to national requirements. Canadian probable effect guideline value for sediment quality is occasionally or constantly exceeded for all metals. Obtained results gained preliminary overview of water endangerment in watercourses.

During the 2004 research of Moraca river water quality was conducted onto six localities: Pernica, Zlatica, Gradska plaza, Kolektor, Grbavci and Vukovci. Physical, chemical and microbiological properties were analyzed. Physical and chemical analyses done were: water temperature, air temperature, pH, electro-conductivity, KMnO4 consumption, dissolved O2 and BCO5 (biological consumption of oxygen in five days). Microbiological analysis included determination of the total number of aerobic mezophyll bacteria, oligotrophic and heterotrophic bacteria, as well as the most probable number of colliform bacteria. In addition to distribution and population dynamics, identification of the bacteria was also done. Microbiological water analysis were performed using standard bacteriologic methods and identification of the bacteria using INVIC or, when needed, using API diagnostics.

In the frame of the project Revitalization of the Big DTD Canal and preparation for introducing modern wastewater treatment plants for the towns and industry in the Backa region, an all-inclusive program has been prepared for monitoring quality and quantity of water in the Big Canal and pertaining lateral canals. The paper presents results obtained for contents of nutrients (N and P) that indicate a poor quality of the Canal water, especially in the segment from the triangle to the hydrological node Vrbas. In many cases, measured concentrations of nitrogen and phosphorus were several times higher than maximal tolerable levels, so that it is necessary to undertake urgent measures with the aim of preventing further degradation of the Canal water, and eventually its revitalization.

In this paper we have presented the results of the investigation of phytoplankton carried out in the Hydrosystem DTD (Danube - Tisza - Danube) in Banat region from April 2003 till November 2004. Accordingly, halophilic algae community of eutrophic type has been described. Seasonal distribution and presence of algae taxa in the investigated water varied significantly. The diatoms were mostly represented by periphytic forms in the huge quantities, which was particularly the case with an avalanche of the eutrophic species such as: Bacillaria paradoxa, Anomoeoneis sphaerophora, Nitzschia acicularis, N. palea, Navicula cryptocephala, Fragilaria ulna, Melosira varians, Surirella ovalis, etc. The significant number of Cyclotella meneghiniana during summer and Euglenophyta in autumn revealed high trophic status in some sections of HS DTD.

The research of phytoplankton in water of Hydrosystem DTD in Banat region (canal complex and the rivers Zlatica, Old Begej) has been carried out seasonally i.e. in the spring, summer, autumn and winter of 2003 and 2004. According to guidance of Anon (2003) we selected biological element - phytoplankton in establishing referral body of water with maximum ecological potential (MEP) of the Danube-Tisza-Danube Hydrosystem also classified as artificial/heavily modified water. Classification was made according to Sorensen indices of similarity. Reference conditions with MEP were assigned to the HS DTD, canal Banatska Palanka - Novi Becej, Novi Becej - Melenci stretch. As determined by phytoplankton analyses, investigated canals and rivers could be classified as waters of good ecological potential, except the rivers Zlatica, Stari Begej (Old Begej) and some sections of the Canal Plovni Begej (Navigable Begej) what was designated to moderate ecological potential.