Effects of UV/H2O2 Process on Characteristics of Disinfection By-products (DBPs) Formation from Nitrogenous Organic Precursors
Date Issued
2016
Date
2016
Author(s)
Leong, Dexter
Abstract
In water treatment processes, chlorination has been widely used as a disinfectant method to oxidize the pollutants or control microorganism growth in water including in distribution systems. Various disinfectant by-products (DBPs) could be formed when chlorine reacts with the organic compounds in the water. Among these, DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) are proved to have carcinogenicities and can cause adverse health effects on human health. In order to control the DBPs concentration, it is very important for the water treatment plants to include effective water treatment procedures to remove organic precursors in water. The advanced oxidation process (AOP) is a chemical oxidation based method use in the water treatments to remove certain organic chemical materials. In the UV/H2O2 method, it create hydroxyl radicals through the dissociation of H2O2 when it received UV irradiance at the O-O double bonds, which gave it a very high oxidation potential to react with all kinds of organic compounds in non-selectively way. Thus, it shows a great solution to treat polluted water which cannot be treated well with traditional water treatment process. Some studies show effectiveness of UV/H2O2 to reduce dissolved organic compound in the natural water, which resulting in DBPFPs reduction after disinfection, but the complexity of the organic matter in natural water making it hard to clarify the source of DBP precursors. This study intended to assess the effects of UV/H2O2 towards DBP precursors reduction from nitrogen containing chemicals. The chemicals studied include N-[3-(Dimethylamino)propyl]methacrylamide (DMAPMA)，(+)-cis-Diltiazem Hydrocloride (Diltiazem) and Benzalkonium chloride (BKC) . The results showed that UV/H2O2 treatments can alter the DBPs formation trends of the three chemicals tested. These chemicals have high potentials to form DBPs including trihalomethane, haloacetic acids, and trichloronitromethane. The amounts of DBPs formed have strong correlations with values of UV-254 absorbance, followed by DOC and DON. During the UV/H2O2 process, the efficacy of hydroxyl radicals formation rely on the concentration of H2O2 which also act as scavengers to UV light. This study also discussed the efficiency of UV/H2O2 process using LED as alternative UV light source and compare the results with low pressure mercury lamp. Results showed that UV-LED were capable of degrading substances which have high absorbance on 254 nm, but it was ineffective in mineralizing the NPDOC when compared with low pressured mercury lamp. The UV-LED apparatus used in this study are also found to be more energy consuming when the results were compared with low pressure mercury lamp in term of AOP efficiency.
Subjects
Disinfection by-products
nitrogenous organic chemical
UV-LED
Type
thesis
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