Comparison of Water Quality for 20 Years Before and After Construction of 8 Nakdonggang Weirs Helps Improve Water Quality at Busan Intake Source

Water Sources in Mulgeum and Maeri Show Water Quality Improvement in 9 out of 11 Comparison Items After Construction

Despite Severe Summer Algal Bloom Issues Every Year, Annual Average Algae Concentration Decreased by About 62%

Busan City Hall.

[Asia Economy Yeongnam Reporting Headquarters Reporter Dongguk Lee] The Busan Metropolitan Waterworks Headquarters announced that the water quality of the Nakdong River Mulgeum and Maeri intake sources, which account for about 90% of the city's water supply, has significantly improved compared to before the construction of the eight weirs on the Nakdong River.

This is the result of comparing and evaluating the water quality for nine years before and after the construction of the weirs, excluding the two-year construction period (2010?2012), over a total of 20 years from 2001 to 2021.

The inspection was conducted on 11 items including BOD (Biochemical Oxygen Demand) out of the 39 legally mandated inspection items, excluding 21 items such as heavy metals that were not detected over 20 years, and 7 items such as Total Organic Carbon (TOC) that were newly established after the weir construction in 2013 and 2021 and thus had no comparable data.

Among the 11 comparable items, nine items showed improvement, including representative general water quality indicators such as ▲BOD (Biochemical Oxygen Demand), suspended solids and algae-related items such as ▲Chlorophyll-a (algal concentration), and nutrients (ammonia nitrogen, nitrate nitrogen, total phosphorus).

However, two microbial-related items, total coliform and fecal coliform, showed an increase. This is believed to be due to changes in microbial habitats caused by rising water temperatures from climate change and increased retention time at the eight weirs. Overall, it was analyzed that there was a positive effect on the water quality improvement of our intake sources.

The 11 evaluation items are included in Article 29 of the Water Supply Act and Article 24 of the Water Source Management Regulations. They include representative water pollution indicators such as pH (hydrogen ion concentration), dissolved oxygen (DO), BOD (Biochemical Oxygen Demand), chlorophyll-a (algal concentration) related to suspended solids and algae occurrence, nutrients (ammonia nitrogen, nitrate nitrogen, total phosphorus), microbial contamination indicators such as total coliform and fecal coliform, and other harmful substances such as dichloromethane.

The comparison of water quality for the 11 items at the intake sources confirmed water quality improvement effects with decreases in ▲algal concentration (chlorophyll-a) by 62%, ▲total phosphorus (TP) by 61%, ▲suspended solids (SS) by 61%, ▲ammonia nitrogen by 40%, ▲BOD (Biochemical Oxygen Demand) by 27%, ▲nitrate nitrogen by 20%, and ▲dichloromethane (volatile organic compounds). Additionally, ▲pH and ▲dissolved oxygen (DO) also decreased due to the reduction in algae.

This is judged to be a positive effect of the Four Major Rivers Project, including self-purification effects due to increased water volume and retention time at the eight weirs such as Changnyeong-Haman Weir, riverbed dredging, removal and management of non-point pollution sources along riverbanks, expansion of sewage and wastewater treatment facilities, and strengthening of total phosphorus discharge standards with installation of advanced treatment facilities.

Other legally mandated items, including 21 types of harmful heavy metals, volatile organic compounds (VOCs), and specific water quality hazardous substances, were consistently undetected, indicating safety.

Park Jin-ok, head of the Busan Metropolitan Waterworks Headquarters, stated, “Contrary to concerns, the water quality of Busan’s intake sources has rather improved after the construction of the eight weirs, showing the effects of water quality improvement projects on the Nakdong River such as expansion of environmental infrastructure and strengthened management of non-point pollution sources.”

“However, since there remains a possibility of increased microorganisms and summer algae due to increased retention time and rising water temperatures from climate change, and concerns about algal toxins, we will drastically reduce algal concentration through the construction of intake towers, and additionally monitor a total of 10 types of toxic substances by adding five more monitoring items this year to the five monitored last year, ensuring thorough management of the Nakdong River intake water,” he added.

This content was produced with the assistance of AI translation services.