Parameters affecting bromate formation during the ozonation of source water and the applications which control bromate formation

Drinking water quality and its effects on human health were known for ages, so some applications such as chlorination, ozonation have been applied in drinking water. Ozonation technology is a common application for source water process to remove heavy metals from water, and provide disinfection of water. So that, ozonation improves the quality properties of water. There are many positive effects which change the water properties, also there are some factors causing side effects and limited usage of ozone because of the fact that ozone is a strong oxidizing agent and reacts with water components. In the presence of bromine which is present in water naturally, bromine ion reacts with ozone and bromate (BrO3-) ion has been formed. As a result of the bromate formation, water may contain toxic compounds and regarding this requirement some regulations have been applied. These regulations have limited the application of ozone to a certain dose. Although the studies on the side effects of bromate seem to be sufficient in laboratory, the studies for the industrial processes are quite limited and insufficient. Because of that the investments of the system are costly. Moreover, it is difficult to keep the optimum system under suitable conditions in the plant. In this study, source process was performed in a source water plant and the analysis was carried out in the laboratory. This study contributes to form accurate methods for the determination of bromate levels, investigates the parameters affecting bromate formation and tries to find applications for the control of bromate formation. Moreover, the detection limit for the analysis was arranged in order to detect low levels of bromate values. In general, the source water has been moved from the source to the plant through the pipelines and then the source water has been ozonized. The process consists of the stages of preform blowing, bottle washing with rincer (ozonized washing) water, ozonation of filling water, filling, capping, labelling, packaging and palletizing. In this study, water samples was collected from some production stages. These samples were mainly composed of ozonated filling water before/after UV and ozonated rincer water. After the water samples were collected, bromate levels were analyzed by chromatographic methods (HPLC) and ozone levels were elucidated by a colorimetric method. In this study, the improvement about the determination method of trace levels of bromate that was formed by the reaction of bromide ions and ozone was studied and a method was applied. Moreover, the relationship between the bromate and pH, ozone dose, contact time, temperature were evaluated. Then, the effects of pH reduction and UV254 application were investigated. Bromate analysis was performed by HPLC with UV-Vis detector. Hence, firstly the EPA 326 method was applied. In this post-column derivatization method, bromate reacted with potassium iodide (KI) and oxidized iodide to triiodide, so it was easy to determine the bromate levels at low concentrations and the detection limit was arranged to be a lower rate. The study about the determination of bromate levels precisely provided measuring 0.2 ppb bromate levels with the EPA 326 method process optimization. In this method, reagents, retention time, column type, flow rates of the reagents were studied and the most efficient condition for the analysis was described. Then, all bromate analysis in this study was performed with EPA 326 method and the results were reported in terms of 'ppb'. After the injection, the bromate levels were found to be between 8.8-8.9 minutes in this method. In order to analyze the samples, firstly process conditions (temperature, pH, degree of ozonation, contact time) were controlled and the information on the conditions were recorded. After the analyses were completed, there were many conditions and the results, so when the results were evaluated some parameters were selected and used to evaluate fairly. When the bromate results that were measured by EPA 326 were reviewed, no statistically significant changes occurred with 0.054 standard deviation in all samples which were ozonized between 0.035 ± 0.002 ppm (p<0.05). In this study, determination limit was defined as 0.2 ppb. Moreover, correlation coefficient of low concentration calibration curve and correlation coefficient of high concentration calibration curve were found as 0.9989 and 0.999, respectively. High concentration method was described for measurement of bromate levels of rincer water and low concentration method described for measurement of bromate levels of filling water. Because of that, rincer was ozonated with higher ozone values than filling water, so the bromate levels of the rincer water were higher and the calibration curve of the rincer water needed wide interval scale. In this study, the water samples with a temperature of 24 ± 1°C and pH level of 8.9 ± 0.1 were ozonized at 0.035 ppm. The relationship between bromate levels and contact time with ozone of these samples were examined for 30 days and first day the bromate level of the sample was recorded as 0.28 ppb. Next days, average bromate level was determined as 0.48 ppb with 0.015 standard deviation. At the end of the first day, ozone application finished completely and resulted with 71% of increase in the bromate level. This information indicated that it was more effective if the bromate levels were analyzed after 1 day and the contact time of the ozone related with the bromate formation. The relationship between bromate levels and pH were determined by the use of water samples with a temperature of 24 ± 1°C. These samples were ozonized between 0.03-0.04 ppm and stayed for a day long. Then the bromate levels were measured. The measurements of the bromate levels were between 0.4-0.63 ppb. The results indicated that 22.1% positive correlation was determined between the pH and bromate levels (p<0.05). The pH value and the bromate levels were found to be related to each other. In this study, no specific reason caused getting out of process control limits between these pH values and bromate levels were kept between upper control limit and lower control limit. The relationship between bromate levels and temperature were determined by the use of water samples with a pH of 8.9 ± 0.1. These samples were ozonized between 0.02-0.03 ppm and stayed for a day long. Then the bromate levels were measured. The temperatures were arranged between 23 0C and 26 0C. The measurements of the bromate levels were between 0.2-0.35 ppb. The results indicated that 28.5% positive correlation was determined between the temperature and bromate levels (p<0.05). The temperature and the bromate levels related to each other. In this study, no specific reason caused getting out of process control limits between these temperature and bromate levels were kept between upper control limit and lower control limit. The relationship between bromate levels and ozone dose were determined by the use of water samples with a pH of 8.9 ± 0.1 and a temperature of 24 ± 1°C. Water samples were ozonized between 0.021 and 0.054 ppm. These ozonized samples stayed for a day long. Then the bromate levels were measured. Bromate levels were between 0-2.3 ppb. The results clearly indicated that 86.4% statistically significant positive correlation was determined between the ozone dose and bromate levels (p<0.05). Rincer water that was prepared by high ozone dose application and used for bottle washing has higher bromate levels than filling water. As the results obtained, the water was treated with 1-1.3 ppm ozone and stayed for a day long. The bromate levels were measured between 12,2-12.68 ppb. In this study, the residual effect of the bromate levels of rincer water to filling water were examined and no statistically significant correlation was determined (p>0.05). When the bottles of the filling water ozonized with 0.03-0.04 ppm and washed with rincer water, the bromate levels of the filling water were measured between 0.5-0.56 ppb. The pH of the water samples with a temperature of 24 ± 1°C ozonized between 0.04-0.05 ppm and stayed for a day long. pH 9.2 ± 0.1 level of the samples were decreased to pH 8.5 ± 0.1 level with the change of the source water during ozonation and the bromate levels were measured. It was observed that pH reduction caused 20.6% of decrease in the bromate level (p<0.05). The water samples with a temperature of 24 ± 1°C, and pH of 8.9 ± 0.1 ozonized between 0.03-0.04 ppm. Just after ozonation, these samples were exposed to UV254-C 330, UV254-C 400, UV254-C 800 and ozonation levels were measured. Respectively, 25%, 21.6% and 20.26% of decrease for ozone levels was occurred after UV254 application. Before and after UV254 application, statistically significant changes occurred for ozone levels (p<0.05). Also, before and after ozonation, these samples stayed for a day long. Then, bromate levels of the samples were measured again. According to the results, 20.5%, 16.6% and 15.9% of decrease for average bromate levels of the samples occurred, respectively. Statistically significant changes occurred for bromate levels of before and after UV254 application (p<0.05). The water samples with pH 8.8, 8.5 and a temperature of 24 ± 1°C ozonized between 0.03-0.04 ppm and stayed for a day long. After one day, the bromate levels were measured. Moreover, just after ozonation, these samples were exposed to UV254-C 800 and stayed for a day long. After a day, the bromate levels were measured again. According to the results, 40% and 35% of decrease for average bromate levels of samples which were exposed to UV254-C 800 occurred (p<0.05) respectively. Then, the difference of the decrease of the bromate levels were evaluated statistically. No statistically significant difference of bromate reduction related to different pH values were obtained by UV254-C 800 application (p>0.05).