Algal Alert Issued at Nakdong River Mulgeum and Maeri Points: Busan City Focuses on Safe Tap Water Supply

High temperatures and strong sunlight continue to create conditions favorable for algae growth

Number of harmful cyanobacteria increases at Mulgeum and Maeri water intake points

Busan Metropolitan City (Mayor Park Hyungjoon) announced that on the 17th and 24th, measurements of algae cell counts at the downstream Nakdong River Mulgeum and Maeri points showed 3,219 and 4,639 cells per milliliter (ml), respectively. As these figures exceeded the algae alert system's 'Attention' threshold of 1,000 cells per ml for two consecutive times, the 'Attention' level of the algae alert system was issued on the 27th.

It appears that the continued presence of environmental conditions conducive to algae growth, such as high daytime maximum temperatures and strong solar radiation, has led to an increase in harmful cyanobacteria. Last year, the 'Attention' level of the algae alert was first issued on June 15, but this year, due to heavy rainfall in Busan and Gyeongnam from January to May, the issuance was delayed by about two weeks.

According to the Korea Meteorological Administration, frequent rainfall is expected for the time being due to a stationary front over the southern region, so the increase in algae cell counts is expected to slow down.

With the issuance of the 'Attention' level of the algae alert system, the city will implement measures to ensure the safe supply of tap water, including ▲ blocking algae inflow at water intake and purification plants (installing barriers, operating spraying devices) ▲ strengthening monitoring of raw and purified water at water sources ▲ enhancing water purification processes.

In addition, from July, when a large-scale algae bloom is expected, two algae removal vessels will be deployed at the Mulgeum and Maeri points to respond thoroughly to algae removal.

The city is inspecting algae cell counts daily at the Mulgeum and Maeri water intake points for algae monitoring, and is also conducting step-by-step inspections of nine types of algal toxins and two types of odor-causing substances on its own.

Even if algae are detected in the raw water at water sources due to a large-scale bloom, strengthening the water purification process?such as chlorine treatment, use of high-efficiency coagulants, and shortening the backwashing cycle of sand and activated carbon filters?completely removes algal toxins and odor-causing substances, making the tap water safe for use.

Additionally, the city is currently conducting basic and detailed design work for an intake tower that will allow selective water intake at different depths to avoid algae, with completion targeted for December 2025.

Since June this year, Busan has been piloting the algae alert system for waterfront sections at Samnak and Hwamyeong Leports Towns to ensure the safety of citizens’ water activities.

Mayor Park Hyungjoon stated, “The city is making every effort to ensure the safe supply of tap water by blocking algae inflow and strengthening purification processes to minimize citizens’ concerns about algae. In addition, we will continue to do our best to provide clean and safe drinking water by swiftly diversifying water sources to secure clean water.”

Busan City Hall