수돗물의 냄새 유발물질 분석 및 처리

Abstract

Musty and earthy smell odorous compounds in the raw water are generally attributed to 2-MIB(2-methylisoborneol), geosmin, IBMP(2-Isobutyl-3-methoxy pyrazine), IPMP(2-Isopropyl-3-methoxypyrazine), TCA(2,4,6-Trichloroanisole). An easy, fast and reliable analytical method is proposed for the determination of the concentration of these odorous compounds. The novel stir bar sorptive extraction (SBSE) technique is employed, following a simple and fast procedure that allows many samples to be extracted simultaneously using very small volume. Extracts are desorbed in a thermodesorption system(TDS) coupled on-line to a gas chromatograph-mass spectrometry system. The SBSE offers good recovery and linear regression coefficient(r2) for the five odorous compounds. From each calibration curve, the regression coeffficients(r2) were obtained from 0.9957 to 0.9994 in 5~50 ng/L concentration. And the limits of detection LODs were determined from 1 ng/L to 3 ng/L, and limits of quantitation LOQs were from 6 ng/L to 8 ng/L. The good repeatability of this method can be deduced from the low R.S.D. values of for five odorous compounds. The mass spectrometric detection in selected ion monitoring mode contributes to the lower detection limit and good sensibility obtained with this method. In this study, five different odor producing compounds in the raw water from the Nakdong river and rapid sand filtered water were treated by oxidation from O₃/H₂O₂process. In addition, the change in BDOC formation by the O₃/H₂O₂ process was also investigated for considering this advenced oxidation process as a pretreatment to the BAC treatment process. The experimental result showed that the removal efficiency of geosmin was higher with the use of 5 mg/L of O₃ and 0.2 mg/L of H₂O₂ than with the use of 20mg/L of O₃ alone for the sand filtered water. And in general, the removal efficiency of geosmin in the raw water was 12~27% lower than the one in sand filtered water. In the sand filtered water, the removal efficiencies of geosmin and IPMP decreased when H₂O₂/O₃ ratio increases above the optimum ratio. The optimum ratio of H₂O₂/O₃ dose was 0.5~1.0 for geosmin and 0.2~1.0 for IPMP. However, the optimum ratio of H₂O₂/O₃ in the raw water remove geosmin appeared to 1.0~3.0. According to the experimental results for the removal of 5 different odor causing compounds under varied O₃ doses, the removal efficiency of IPMP was the highest with 60% and, in overall, O₃/H₂O₂process showed higher removal efficiency than O₃ alone process. The BDOC formation by the O₃/H₂O₂ process increased from 0.1~0.25 to 0.19~0.34 comparing to O₃ process alone. Therefore, it is concluded that the advanced oxidation process with O₃/H₂O₂ can be used as a pretreatment to the BAC process. Powdered activated carbon(PAC) is widely used to control odorous compounds causing earthy-musty odor in the drinking water supplies. When PAC is added at the just before incorporation of PAC into coagulants floc particle may affect adsorption rate and capacity. It was known that chlorine is one of the chemicals often come into contact with activated carbon. But activated carbon react with chlorine and surface oxide accumulate on carbon surface. As result, adsorption capacity of activated carbon is reduced. Granular activated carbon(GAC) has been identified as a best available technology for removal odorous compound. Rapid small scale column test were used to investigate 3 types of carbon(coal, coconut, wood) for their affinity to absorb odorous compounds. Five odorous compounds(2-MIB, geosmin, IPMP, IBMP, TCA) concentrations were measured in the column effluent to track GAC breakthrough. Odorous compounds breakthrough occurred at around 50,000~90,000 bed volumes(BVs) of operation for coal virgin GAC investigated. The coal based avtivated carbons(F-400) were determined to have the highest adsorption capacity for odorous compounds.