By Yun Suh-young
Seoul City is preparing to spray red clay in parts of the Han River as the amount of green algae present is reaching dangerous levels.
The green algae, first found in large quantities along the northern Han River is now being found in Seoul due to an increase in water temperature and a lack of rain caused mainly by the continuing heat wave. The algae is more likely to spread rapidly in higher temperatures.
The city government said Tuesday that it is waiting for results from the National Institute of Environmental Research (NIER) on the toxicity of the green algae and for the amount of clay to be spread in the rivers. The city has prepared 12 tons of red clay powder to alleviate the problem.
According to an inspection conducted by the city last Wednesday, high levels of chlorophyll-a, which is a component that indicates the appearance of green algae, was found in three of the water intake facilities in Seoul.
The green algae warning will be issued if the level of chlorophyll exceeds the standard level of 15 in a re-inspection to be held today, the city government said.
Until now, the red clay could only be sprayed in cases of a severe green algae outbreak but since the Ministry of Environment changed the regulations in June, it can now be sprayed even at a warning level which is two steps below a severe outbreak.
“When the red clay is sprayed on the water, it combines with the green algae and sinks to the sea bed. It then dies and is highly unlikely to resurface,” said Lee Soo-hyung, team manager of the water environmental engineering research division at NIER.
The Seoul Metropolitan Government plans to check with the NIER on whether the spread of red clay has any detrimental environmental effects on living water organisms. If the environmental office in control of Han River makes the final decision, the clay will be dispatched.
A guideline for citizens will also be distributed to citizens, the city government said.
If a warning is issued, those who have sensitive skin or skin diseases will have to restrain from engaging in water sports activities such as water skiing and swimming.
Also, in order to eliminate the mold smell in tap water caused by a compound called “geosmin,” tap water must be boiled for over three minutes in temperatures over 100 degrees Celsius.
Geosmin is a by-product from the spread of “anabaena,” which creates the green algae. The toxic material from anabaena can attack the liver and the nervous system if ingested by humans.
The green algae began to spread from regions in the upper Han River near Paldang Dam in Gyeonggi Province. Dozens of residents near the dam complained that their tap water smelled unpleasant.
The initial occurrence in the northern region is attributed to the amount of water discharge from a dam near North Korea, according to Lee.
“The green algae phenomenon occurred last winter in the upper regions due to the halt in water discharge from the dam. It looks like the latent particles of algae from that time reappeared,” Lee said.