Aspiration to multipurpose use of built drainage systems structure in Vojvodina, total length about 20,000 km, must be followed by detailed investigation of influence of water stream through detailed canal network (DCN) from water source to the final consumer. Typical cases of two purpose use of DCN is supply canal of drainage / irrigation system on region Middle Banat, Zrenjanin, characterized by taking water from Begej river and long stream to the final consumer. Influence of long stream through DCN to water quality change are investigated on mentioned localities during 2004. Obtained results are pointed out water quality decrease in these conditions. Decrease is expressive in case of smaller flow. This paper deals with estimation of water suitability for irrigation taking into consideration possible undersirable effects of this water to irrigated soil.

During several years of hydrobiological investigation of the Zapadna Morava river the Medjuvrsje and Stancici localities stood out; the most favourable water quality was registered with the Medjuvrsje reservoir (being constantly of the class 2), whilst, according to all the data obtained over the years, water quality of the Zapadna Morava at Stancici locality was the worts. The Medjuvrsje reservoir is in stable eutrophic phase. The saprobic index value points to a certain water quality improvement. Floristic diversity in the locality of Stancici increased over the years. An increase in the percental share of the oligosaprobity indicator indicates a certain organic load decrease and an improving water quality trend was recorded as indicated by lower saprobic index values.

According to the Programme of systematic examination of surface water quality of the Republic Hydrometeorological Service of Serbia the examinations of Medjuvrsje water reservoir have been carried out during October 2002 and August 2003. The examinations have been carried out at the dam, in central part and at the entrance of the water reservoir, on three depths. This paper shows the results on phytoplankton composition, chemicophysical properties and the trophic status of water reservoir. The qualitative analysis of the phytoplankton shows the presence of 96 taxa from six divisions of algae. Following the standard of Swedish Agency for Environmental Protection, the high concentrations of primary nutrients belong to the fifth class, by the categorization. According to OECD classification trophic status of water reservoir may be characterized as eutrophic and hypereutrophic.

Nitrogen and phosphorus contents in water, sediment and shoots of Phragmites communis Trin, and Typha latifolia L., as possible indicators of trophic state were used in the area of the Bardaca fish-pond. The results of total nitrogen and phosphorus contents during growing season indicate the hypertrophic state of waters in all locations.

Eutrophicationn problems in the Kotor bay were studied monthly from September 2003 to August 2004. As a result of nutrient enrichment (directly dependent on human activities), phytoplankton growth was very intensive, reflected by high concentration of chlorophyll a (7.46 mg/cubic m).

The paper presents the seasonal overview of horizontal distribution and abundance for the species of genus Oithona in Bokokotorski Bay. Three species have been recorded. Oithona helgolandica and Oithona plumifera have a wide horizontal distribution within the Adriatic Sea, while Oithona nana is a typical euritherm and eurihaline form that occupies shallow and closed coastal areas along the eastern coast of Adriatic. Also presented are seasonal oscillations and quantitative presence of these species in the Copepoda population during 2002.

The aim of this study was to determine the content of heavy metals, cadmium and lead, in drinking water, spring and well water from rural part of south Serbia, as in water of river Jablanica and in the top water. The content of cadmium and lead, a very toxic metals, were studied simulataneously by potentiometric stripping analysis (PSA) in water samples using thin mercury film electrode, as a working electrode, by standard addition method in the presence of supporting electrolyte. The results of content of examined heavy metals obtained in examined water samples by PSA method, are compared with results obtained by using AAS and GF-AAS spectrometry.

Potentiometric stripping analysis (PSA) is highly sensitive electroanalytical method for determination of traces of heavy metals. In this paper detection limit and linearity of potentiometric stripping analysis for lead was investigated. Method was successfully used for determination of traces of lead ion (detection limit 5 microgram/cubic dm) in stream water of river Ibar, before and after joint of potential pollutant.

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.).