어승생 수원지 색도발생 원인 규명 및 정수처리 방안 연구

Abstract

This study investigated the cause of chromaticity and its removal methods at Eoseungsaeng water treatment plant(WTP) in Jeju. For removing the origin material of chromaticity, suitable water treatment process was sought by the comparison and the analysis of efficient chromaticity removal methods through the lab-tests by each process. To find the source material of chromaticity, monitoring the raw water was carried out by separating the field measurement with the lab test. And using the chlorine and ozone oxidation, the application of chromaticity removal through changing the conditions of oxidation was evaluated. The test results of field and lab showed that the concentration of Fe, Mn were N.D.∼ 0.02 mg/L, N.D.∼0.003 mg/L, respectively at 1st lake and N.D.∼0.02 mg/L, N.D.∼0.002 mg/L, respectively at 2nd lake which suggested that those were the least reason of chromaticity occurrence. The variations of pH, DO, chromaticity, Chl-a were similar along the depth. At 3∼4 m of depth, there were inflection point presumably due to algae. To find the basis about this theory, quantitative experiments of algae were conducted. This experiment showed that the variations of number of algae was similar to the trend of pH, DO, chromaticity, Chl-a along the depth. For estimating the source material of chromaticity, correlation of water quality parameters was analyzed. The correlation value between chromaticity and number of algae was the most high value of 0.4308, so algae was estimated as a cause of chromaticity. The chlorine oxidation experiments were implemented with various dosages(0.3∼1.5 mg/L) and pHs(7, 8, 9), and ozone oxidation experiments performed under pre&post injection with various dosages and pHs(7, 9). In chlorine oxidation, optimal dose of 1.0 mg/L with contact time of 30~60 min. leaded to 43% of chromaticity removal. On the other hand, 71.43% of chromaticity removal rate was noticed at post-ozone dosage of 0.931 mg/L under pH 9, and 86.71% of chromaticity removal rate was noticed at post-ozone dosage of 3.0 mg/L under pH 9. If the chromaticity concentration of raw water is low, present chlorine disinfection facility can be available. But if degree of chromaticity is higher, the introduction of ozone oxidation process may be necessary.