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.

Treatment of groundwater with increase contents of ammonia, iron and manganese, needs more content of oxigen then realized in proceeding of aeration. Beside enriching water of oxigen, ozonization gives other important effects. For the first time, ozonization is practicaled on plant in Pancevo (Serbia), and it is base for define all of positive experiences. From this, we can recognize priorities of this proceeding, which will be aranged in this report.

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.

Determination of total arsenic and As(III) was performed in untreated and treated water samples collected in some small water supply systems in Northern Backa district (Serbia). Concentration of total arsenic in treated water was between 71 and 115% of total arsenic in untreated water (0.001-0.168 mg As/cubic dm). In untreated water concentration of As(III) was between is less than 0.001 and 0.078 mg As/cubic dm. However, during the water treatment (chlorination process) As (III) concentration decreased significantly to the level of 1 to 2% of start concentration in untreated water. Influence of conservation water sample with HCl increased with consumption of KMnO4 on determination of As(III).

A great floristic variety has been noted according to qualitative analysis of phytoplankton. The presence of 187 taxa from 7 divisions of algae has been noted. The results of quantitative analysis show the dominance of centric diatoms. The high values of biomass that point out on the trophicity increase are noted on the strech from Nestin to Zemun (Serbia) with the maximum at Centa (Serbia) with 15,885 mg/cubic dm. Downstream Zemun, it has been noted gradual decrease of biomass up to Pancevo (Serbia), and afterwards downstream the considerable reduction all the way up to Brnjica (Serbia), where the value of algal biomass was 1,697 mg/cubic dm.

The paper considers legal framework for the surface waters quality control as per our Regulation and Directive 75/440/EEC in terms of required quality of surface waters intended to be used for the drinking water production. Research has been done in eight accumulations designed for water supply in Serbia, and water quality index has been determined using WQI method during the period 2000-2004. The water quality in these accumulations was within the treshold values in relation to the required quality.

There are some water reservoirs on the territory of Zajecar district area (Serbia). Their purpose and time of building are very different. It is also different the organic matter production in those reservoirs. Water reservoirs for supplying with drinking water are very specific because the increased of organic products makes some difficulties in process of refinement reservoir water to drinking water. In this paper we are trying to explain, taking the reservoir Grliste for the example, if the biomanipulation exerts on water quality in the reservoirs.

The puddles Slatina and Pecena Slatina are the old meanders of the river Tamis. These ecosystems are periodicity fill with moderate salt and high alkaline water. The paper gives a review of qualitative and quantitative analysis of the algal compositions. Cyanoprokaryota and Euglenophyta are more common. All investigated parameters like compositions of lagal communities, their abundace, biomass and chlorphyll-a showed a high level of nature eutriphication in these ecosystems.

During spring of 2005, referent monitoring of the chemical quality of surface waters and sediments in some protected areas in Vojvodina (Serbia) was conducted as a supplement to the Regular monitoring program. The aim of the study was to establish the chemical quality of surface waters and sediments regarding nutrient content. It is shown that the water quality satisfies the criteria of the 1st/2nd class according to our legislation, with the exception of the Ludos location, which showed a contamination with nitrogen matter in water and sediments. With regard to the contamination of water with phosphorus, almost all locations may be considered as potentially problematic.