Due to global warming and the increase of nutrient input from pollutant sources of pollutants, eutrophication of lakes and rivers used as the water supply sources has been getting worse. Algal bloom caused by eutrophication may bring out psychological discomfort and death of aquatic organisms due to cyanobacterial toxins. Additionally it can result in contamination of toxins and odor and filter clogging in tap-water production facilities when the eutrophicated rivers or reservoirs are used as drinking water sources.
Many kinds of algal removal processes have been developed in order to prevent these problems, but most of them can not be applied to the reservoirs and rivers with the huge water body such as Daecheong Reservoir and Nakdong River, even though these processes showed the high algal removal efficiency in the small-sized water bodies.
In this study the algal removal efficiency was estimated with a mobile algal removal device in the So-ok Stream which located in the tributary of the Daecheong Reservoir. This device is consisted with main body, buoyant, transfer hopper, screen conveyor, sludge remover, and auxiliary equipments(chemical sprinkler, generator etc.). Using this device the algal scum was directly removed after spraying a coagulant. The treatment capacity of the device is about 80,000m3/day based on eight work hours per day.
The device was operated in the algal blooming season from 6, agust to 16, October in year 2015. In the operating period 1,516.25 kg(dry weight) of algal biomass was removed. The area of 40,478㎡ per day was treated. Through the operation the concentration of chlorophyll a was reduced by 0.511 mg/㎥ per operation. It was estimated that it costed 17.8 million Won for reducing the concentration of chlorophyll a by 1 mg/㎥ in So-ok Stream(350,000㎥). There was no release of cyanobacterial toxins during coagulant dosing and operation for coagulation.
It is concluded that the device used in this study could be appliable to control the algal bloom in the large-sized reservoirs and rivers because of it''s big treatment capacity and high cost-effectiveness.