Chlorination is the most common disinfection method used in the drinking water production. Reactivity of chlorine with organic molecules could generate disinfection by-product (DBPs), which are harmful to the human health. Natural organic matter (NOM) is a complex mixture of chemicals existing in source water. Because of its complexity, it is conjectured that formation of many different DBPs can arise from the reaction of organic matter and a chemical disinfectant. This study used model compounds as NOM surrogates in order to reveal the specific organic fraction and DBPs formation potential removed by different coagulants. Model compounds, as an artificial sample, were made from a mixture of Suwannee River Humic Acid (SRHA), Suwannee River Fulvic Acid (SRFA), Bovine Serum Albumin (BSA), Alginic Acid (AA). Alum and FeCl3 were used as coagulants. The samples were analyzed for organic parameters, such as total organic carbon (TOC), ultraviolet at 254 nm wavelength (UV254), specific UV absorbance (SUVA), and organic fractionated by high performance size exclusion chromatograph with organic carbon detector (HPSEC-OCD). The concentration of trihalomethanes (THMs) and haloacetic acids (HAAs) was measured to present the DBPs formation. The results show alum and FeCl3 removed biopolymer (Peak A), humic substances-like (Peak B, Peak C) at the same percentage, while low molecular weight acid and neutral (Peak D) showed a higher removal with alum than FeCl3. HAAs removal led to a greater reduction than THMs removal, and FeCl3 showed a higher removal than the alum coagulant. It indicated that alum and FeCl3 coagulant have different ability in removing specific organic fractions, which are precursors of THMs and HAAs formation.
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A photocatalytic process of degradation of the selected sulfonamides (sulfathiazole, sulfamethoxazole and sulfadiazine) added to real wastewater was studied in this work. The process was initiated by UV-a irradiation and TiO2-P25, FeCl3 and mixtures of TiO2-P25 with FeCl3 were used as photocatalysts. The effect of pre-treatment of wastewater and the influence of process parameters on the efficiency of sulfonamides removal were also determined. It was found that the highest efficiency of degradation was achieved in the process carried out in the presence of TiO2-P25/FeCl3 mixture, in full scale effluent wastewater treatment plant..
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