Ozonlama İşlemi Sırasında Doğal Kaynak Suyunda Bromat Oluşumunu Etkileyen Parametreler Ve Bromat Miktarının Kontrolünü Sağlayan Uygulamalar

Abstract

Ozonlama teknolojisi, sudan ağır metallerin uzaklaştırılmasını ve suyun dezenfeksiyonunu sağlaması nedeniyle, doğal kaynak suyu proseslerinde kullanımı yaygın olan bir uygulamadır. Ozonlama prosesinin suda meydana getirdiği değişimlerin olumlu etkilerinin yanında, ozonun kullanımını kısıtlayıcı yan etkileri de bulunmaktadır. Bu yan etkiler ile ilgili laboratuar ortamında yapılan çalışmalar yeterli gözükmesine rağmen, endüstriyel uygulamalar ile ilgili çalışmalar oldukça sınırlı ve yetersizdir. Bu çalışma ile tekniğine uygun ozonlama işlemine tabi tutulmuş doğal su örneklerinde, ozonlama işleminden sonra düzenlenen metotlarla oluşan bromat maddesinin doğru ölçümlenmesi sağlanarak, bromat oluşumunu etkileyen parametrelerin ve bromat oluşumunun kontrolünü sağlayan uygulamaların tespit edilmesi sağlanmıştır. Doğal kaynak suyu şişeleme tesislerinde genel olarak kaynak suyu, boru hatları boyunca su tesislerine taşınarak ozonlanmaktadır. Proses; preform şişirme, rinser (ozonlu yıkama) suyuyla şişe yıkama, dolum suyu ozonlama, dolum, kapaklama, etiketleme, paketleme ve paletleme aşamalarından oluşmaktadır. Bu çalışmada, üretim sürecinin belirlenen aşamalarında, su örnekleri alınmış; örneklerde kolorimetrik yöntemlerle ozon tayini ve kromatografik yöntemlerle (HPLC) bromat tayini gerçekleştirilmiştir. Bu çalışmada ozonlama prosesi boyunca doğal kaynak suyu içerisinde doğal olarak bulunan bromür iyonunun ozon ile reaksiyonu sonucu oluşan bromat maddesinin çok düşük miktarları için ölçüm yönteminin geliştirilmesi çalışılmıştır. Ayrıca ozonlama sonucu oluşan bromatın pH, ozon dozu, sıcaklık ve temas süresi ile ilişkisi incelenerek; pH düşürülmesinin ve UV254 kullanımının bromat kontrolü üzerine etkisi araştırılmıştır. Bromat ölçümü konusunda hassas bir metot oluşturma çalışması, HPLC cihazında EPA 326 metodunun uygulaması ile birlikte bromat parametresinin 0,2 ppb düzeylerinde ölçüm yapılabilmesini sağlamıştır. Daha sonra çalışmada yapılan tüm bromat analizleri EPA 326 metodu ile gerçekleştirilmiş ve ‘ppb’ cinsinden raporlanmıştır. EPA 326 metodu sonuçları incelendiğinde, 0,035 ± 0,002 ppm aralığında ozonlama yapılmış sulardaki bromat ölçümleri arasındaki farkların 0,054 standart sapma ile istatistiksel olarak önemli düzeyde olmadığı görülmüştür (p0,05). Şişeleri rinser suyu ile yıkandıktan sonra 0,03-0,04 ppm skalasında ozonlandırılmış su ile doldurulan örneklerin bromat değerleri 0,5-0,56 skalasında ölçümlenmiştir. Ozon değerleri 0,04-0,05 ppm aralığında tutulmuş, ölçüm sıcaklığı 24 ± 1°C’ye sabitlenmiş pH 9,2 ± 0,1 değerine sahip örneklerinde, proses aşamasında kaynak değiştirme çalışması uygulanıp pH 8,5 ± 0,1 derecelerine düşürülerek bu uygulamanın etkisi incelenmiş, elde edilen sonuçlara göre, pH düşürülmesinin bromat değerinde ortalama %20,6 oranında azalmaya sebep olduğu görülmüştür (p0,05).

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 (p0.05). 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 (p0.05).