Determination of precursors to formation of haloacetic acids in the source water in Bangkok / Vorapot Kanokkantapong = การหาสารก่อตัวของสารฮาโลอะซิติกแอซิดในแหล่งน้ำดิบในกรุงเทพมหานคร / วรพจน์ กนกกันฑพงษ์
This work investigated the formation of potentially carcinogenic haloacetic acids (HAAs) compounds in the raw water of the Bangkhen water treatment plant. The resin adsorption technique (with three different types of esins, i.e. DAX-8, AG-MP-50, and WA-10) was employed to characterize the dissolved organic carbon (DOC) content in the raw water into six fractions, i.e. hydrophobic neutral, hydrophobic acid, hydrophobic base, hydrophilic neutral, hydrophilic acid and hydrophilic base. Hydrophilic species seemed to be the predominant organic species in this water source (approx. 60%) with the neutral fraction being the most abundant (approx. 40%). Hydrophobic species, on the other hand, played the most important role in the formation of haloacetic acids as they contributed to as much as approx. 56% of total Haloacetic acids formation potential (HAAFP). Among the six fractions, the hydrophobic base exhibited the highes specific haloacetic acids formation with 207.69 uhHAAs/mgDOC whereas hydrophilic acid performed the least with 33.11 ugHAAs/mgDOC In the study of the interaction between organic fractions during the formation of HAAs, the components with base property were found to promote the HAA formation whereas the acid species were found to have inhibitory effect. Only three regulated HAAs species (mono-, di-, and trichloroacetic acids) were detected in this study, among which, dichloracetic acid was found to be the predominant species in the chlorination of individual organic fraction tests. Monochloroacetic acid was, on the other hand, prefominant in the mixture of multi-component fraction tests. Each organic fraction was examined for their associated functional groups by Fourier Transform Infrared (FTIR). The investigation of the formation mechanism of HAAs was achieved by tracking the changes in the FTIR results of the same water sample before and after the chlorination reaction. Carboxylic acids, ketone, amide, amino acids and aromatic characteristic organics seemed to be the main precursors to the HAA formation.