This study was performed to investigate the influence of the ozonation process on natural organic matter (NOM) and trihalomethane, haloacetonitrile and chloropicrin precursors in groundwater. The largest reduction in dissolved organic carbon, DOC (up to 25%) and UV 254 values (up to 69%) was achieved using 3 mg O3/mg DOC. Reducing the total organic matter resulted in a reduction of trihalomethanes precursors to 194 micro g/L. On the other hand, when it comes to the precursors of the high priority nitrogenous disinfection by-products, the oxidation of NOM by ozone and the resulting increase in organic matter with a low molecular lead to an increase in the haloacetonitrile precursors compared to the raw water and the formation of chloropicrin precursors.

The paper deals with pilot-scale investigations of the effect of preozonation on NOM removal from groundwater by coagulation and flocculation processes. It was found that the preozonation increased the efficiency of organic matter removal by coagulation and flocculation from 23.6 to 47.2% as judged on the basis of KMnO4 values. From the aspect of the change of content of trihalomethanes precursors preozonation exhibits both the positive and negative effects if their content in the water after coagulation is considered in dependence of the applied ozone dose. The obtained values siggest the necessity of careful optimization of the processes of preozonation, coagulation, and flocculation, especially from the aspect of the change in content of the precursors of disinfection byproducts.

This paper examines the impact of ozonation (0.4 to 3.0 mg O3/mg DOC) and the Peroxone process – O3:H2O2 (0.4 to 3.0 mg O3/mg DOC; O3:H2O2 = 1:1) on the content of natural organic matter (NOM) in water. It was found that the Peroxone process results in a greater degree of total organic matter content removal (up to 81% UV254), but also oxidises a greater amount of hydrophobic NOM compared to ozonation. Ozonation was more effective for the removal of the specific haloacetic acid (HAA) precursors (29-50% HAAFP), whereas the Peroxone process was more effective in the removal of haloacetonitrile (HAN) precursors (19-43% HANFP).

A series of measurements has been conducted with various combinations of ejector dimensions. Variables were diameter of the nozzle and the distance between the end of the nozzle and the beginning of the pipe. Vacuum head in function of water flow was measured when there was no air flow, and when there was air flow (from a reservoir with constant volume). The results are presented in this paper.

Groundwater from the middle Banat region (Serbia) which is used as a drinking water supply for Zrenjanin town contains a high amount of natural organic matter and a high content of arsenic. In this study a pilot-scale system was used to investigate the influence of different ozone doses (0.4-0.9 mg O3/mg DOC) during a pre-ozonation process on NOM removal by coagulation. Ferric chloride coagulant was chosen at a dose of 100 g/cubic meter, as a traditional coagulant which can also help in arsenic removal. The obtained results indicate that an ozone dose of 0.4 mg O3/mg DOC has the best influence on structural changes of NOM. The coagulation process with ferric chloride as coagulant had a significant influence on the arsenic content of the water, with the measured values in the water after coagulation in all three investigated treatment trains being below 10 microgram/l, which is the standard MCL in Serbian legislation.

Coagulation and flocculation can be efficiency applied in drinkling water treatment, in order to remove natural organic matter (NOM). However, in the experiments presented in this paper, the water used is very rich in NOM, and required investigations of additional processes. In order to increase the efficiency of coagulation and flocculation processes in removing NOM from groundwater, the following processes were investigated: adsorption on powdered activated carbon (5-30 mg PAC/l) and preozonation with applied ozone doses of 1.1-6.3 mg O3/l. The parameters used to evaluated the changes in NOM content during the experiment were: KMnO4 consumption, UV absorbance at 254 nm, pH and turbidity.

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 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.).