천연 무기 응집제와 미세기포를 이용한 녹조 제어에서의 수질 변화 = Changes of water qualities by controlling harmful algal blooms using natural inorganic coagulants and microbubbles

다국어 초록 (Multilingual Abstract)

The occurrences of rapid and excessive growth of algae, harmful algal blooms (HABs), have been reported all around the world. A number of technologies have been developed to control HABs and one of the common approach is applying coagulants to settle or float algal cells and removed them from water. However, coagulants themselves can induce environmental concerns like affecting pH and alkalinity. Therefore, it is important to monitor water quality changes after their application. This research presents how a natural inorganic coagulant and microbubbles can be used to control harmful algal blooms in fresh water bodies and the changes in water qualities. To evaluate the performance of the natural inorganic coagulant, raw water (50 ug/L of chlorophyll-a) was sampled from A reservoir in Gyeong-gi province in August when the reservoir was experiencing severe HABs. Jar test was conducted to determine the optimum dosage (2 ml/L), then the coagulant was added to two test columns filled with raw water and mixed thoroughly. Then, microbubbles were injected for a minute to float the algal cells and the algal scum was removed from only one column while the other was remained in the column. Turbidity, chlorophyll-a, total phosphorus, total nitrogen, and microcystin values from supernatant of two columns were analyzed daily for 16 days. The flocs were well flocculated throughout the experiment period. Total nitrogen concentrations from the scum remaining column were higher than the scum removed column which indicates nitrogen release from algal cells. The highlight of this research is that microcystin was not detected from the scum removed column while the sam value from the other column was keep increasing up to 1 ug/L. The results from this research suggests a healthier approach in controlling HABs by using coagulant and microbubbles to remove algal cells from water, in order to prevent further eutrophication and water pollution.