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.

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.

Microbiological and saprobiological characteristics of river Moraca and Skadar lake for period of 2004/2005 are done at localities: Pernica, Moraca estuary and Vranjina (Skadar Lake). The objective of the research is to establish quality of water of these aquatic ecosystems based on microbiological and saprobiological analyses, as well as, to show need for protection of these water ecosystems from permanent contaminations, mainly by sewage should be pointed out. Saprobiological index is determined based on Gulyas Pal, and Pantle Buck is used to determine saprobiological level.

One of the key issues related to the water quality in the Iron Gate reservoir is the pollution of the sediment. Sediment deposits retained in the Iron Gate reservoir originate from a wide river basin with more then 80 million inhabitants and highly developed municipal and industrial infrastructure. Besides mineral river sediment, various organic and inorganic matters entered and deposited within the Iron Gate reservoir. Sediment research objective was to assess the content of contaminants and nutrients which potentially could enter the water column.

In the frame of the project Water Supplying of the Cities and Protection of the Groundwater Quality in the Velika Morava Valley, was obtained the analysis of potential polluters of groundwater source of city Smederevska Palanka - Trnovce. This paper presents results of water physical, chemical and microbiological characteristics of soil. According to the results of research and way of usage of the soil, it was concluded that agricultural production does not have negative influence on quality of the groundwater source.

Protection of raw water quality at the water source is delicate and often very expensive. As it is known, the majority of hydrotechnical structures are complex and big in both technical and financial terms. This paper is aiming to show necessity to provide, if possible, multipurpose use of these structures in order to reduce and distribute the costs.

In this paper the results of zooplankton investigations (and its dominant group Copepoda) were presented from the part of the Boka Kotorska Bay with more intensive circulation with the open sea, from summer of 2005. Some results from the open South Adriatic were given, too - from the frontal zone exposed to anthropogenic eutrophication of Bojana and Drim rivers, and the impact of oligotrophic South Adriatic, simultaneously.

In this paper, results of phytoplankton investigations were performed in June 2005. The investigated positions are located near the entrance of Boka Kotorska Bay: two positions in the outer part (Zanjica and Mamula island) and two positions in the inner part of the Bay (Njivice and Tivat bay). In this area the influences of the open sea and the land are expressed to the phytoplankton community. As a consequence of that quantities of phytoplankton are lower in the outer part and higher in the inner part. The most dominant species is diatom Pseudo-nitzschia delicatissima which is very frequent in the eutrophic area.

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).