There was carried out microbiological analysis of five bottled water of manufacturers from Serbia. Bacteriological quality was estimated using important parameter-aerobic mesophylic bacteria. Two nutrient media were used: standard (PCA) and low nutrient R2A. Plates were incubated at two temperatures (37 deg C and 22 deg C) during 24 hours, 48 hours, 3 days and 5 days. Results show that this group of bacteria is very abudant in bottled waters and their number depends on water types and manufacturers. Moreover, water from different bottles of the same manufacturer has different microbiological quality. Used media, temperatures and period of incubation also have influence on results and R2A medium gives higher values of aerobic mesophylic bacteria.

Removal of colour by coagulation in the drinking water treatment is described. Optimal results are obtained by pH correction. Buffer capacity of raw water is dominant on efficiency and rentability of the process.

This work considers the possibility of enhancing the iron (III) chloride coagulation process in natural organic matter removal by flocculation sludge recirculation. The results show that flocculation sludge has the potential to coagulate organic matter, and shows a dependence on the depth in the precipitator (0, 30 or 70 cm). Recirculation of flocculation sludge at a dose of 1.6 g/l (from a depth of 30 cm), results in a reduction of required coagulant by 25%.

One of the biggest problems in drinking water treatment is the presence of a high natural organic matter (NOM) content in water resources. This paper presents the results of a study which aimed mainly to determine a combined coagulation and preozonization process application for trihalomethanes and haloacetic acids precursors content in ground water rich in natural organic matter.

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.

In this paper two different combinations for wastewater treatment are proposed for specific problems that Vojvodina (Serbia) has with arsenic. Both proposed technologies take into account treatment of water and treatment of waste. In this paper the concrete solution for water treatment is proposed for water that contains arsenic (the concentration is around 100 microgram/L) in Obrovac and Palic. With these water treatment plants the removal of ammonia (measured concentration was above the maximum allowed value, from 1.35-2.5 mg/L) is also included in case of Obrovac wastewater plant, and for Palic the proposed treatment plant the removal of iron (measured concentration was above the maximum allowed value, from 1.35-2.5 mg/L) is also included. With both treatment plants and with both proposed technologies the overall treatment of water is planned.

The paper analyses application of different methods for removal of the high content of ammonia from groundwater sources of the Grocka municipality neighborhoods Umcari and Pudarci. According to the relevant data from this field method, biochemical oxidation with the Nitrosomonas and Nitrobacter bacteria was used. Parameters of biological processes of the ammonia oxidation were defined on the pilot model located at the groundwater source. On the pilot model, consisting of a trickling filter and a fast gravel filter, quantitative oxidation NH4 to NO3 was done. Purification plant was designed with parameters of the pilot model, with minimal investment and exploitation expenses, without undesired side products and ecological risks characteristic for procedure of chemical oxidation of ammonia, which recommends this procedure as the optimal solution.

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).

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.

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.