Use of chlorine dioxide for water disinfection and determination of residue by field method

Namen magistrskega dela je razvoj analitske metode za terensko merjenje klorovega dioksida. Za terensko delo je primerna DPD metoda, ki smo jo želeli primerjati z jodometrično metodo. Uporaba klorovega dioksida kot sredstva za razkuževanje pitne vode se je v zadnjih letih precej povečala. Klorov dioksid je dražji, bolj zapleten za uporabo, vendar učinkovit že pri nizkih koncentracijah. Glavna prednost je manj stranskih produktov, predvsem nižje koncentracije trihalometanov. Hkrati smo preverili tudi delovanje aparata za merjenje klora na terenu, uporabili smo tudi revalidacijo, naš namen je bil znižati mejo zaznavanja (LOD) na 0,03 mg/l. V magistrski nalogi je bila merilna negotovost en izmed pomembnejših faktorjev metode. Ugotovili smo, da je merilna negotovost najvišja pri najnižji izmerjeni koncentraciji klora, pri višjih koncentracijah pa je bila manjša merilna negotovost. Izračuna merilne negotovosti za klor dioksid pa ni bilo možno izračunati, saj so nam manjkali podatki meritve pri obnovljivosti metode. Klor dioksid se v vodi hitro porablja, istega vzorca nismo mogli uporabiti v daljšem časovnem obdobju. Pri jodometrični metodi pa smo prišli do zaključka, da se je koncentracija pripravljene raztopine klora dioksida znižala po določenih dneh. Predpostavljamo, da je v laboratoriju pripravljena raztopina klor dioksid neobstojna in kot taka težko merljiva v laboratoriju.The purpuse of the masters thesis is development of field method for chlorine dioxide measurement. Appropriate method for field measurements of chlorine dioxide is DPD method, which we wanted to test against iodometric method for measurement of chlorine dioxide. Use of chlorine dioxide as disinfecting agent for drinking water has risen a lot in latest years. Chlorine dioxide is more expensive, more complex for use, but on the other hand, effective at lower concentrations. Its main advantage is less side products and most of all, lower concentrations of trihalomethanes. We have concurrently checked working of field aparatus for chlorine measurement, used revalidation and our goal was to lower the LOD to 0,03 mg/l. In the masters thesis, uncertainty of measurement was one of the most important factors of the method. We found that the measurement uncertainty was highest at the lowest measured chlorine concentration, and at the higher concentrations the measurement uncertainty was lower. It was not possible to calculate the measurement uncertainty for chlorine dioxide. We lacked measurement data in the reproducibility of the method. Chlorine dioxide is consumed quickly in water and the same sample could not be used for a long period of time. In the iodometric method we came to the conclusion that the concentration of the prepared chlorine dioxide solution decreased after certain days. We assumed that the chlorine dioxide solution is unstable and as such difficult to measure in the laboratory