Larvae in Seoul Tap Water Originated Externally... "No Abnormalities in Purification Process"

Seoul Waterworks Authority Confirms Safety of Granular Activated Carbon Beds and Overall Water Purification Process
No Chironomidae Found Among 15 Larvae Samples from Complaints... Moth Flies and Earthworms Unrelated to Tap Water

[Asia Economy Reporter Jo In-kyung] The larvae found in bathrooms and washbasins of households in the Seoul area were confirmed to have originated not from tap water but from external sources such as drains or water storage tanks. The larvae were mainly types of moth flies or earthworms, and the larvae of chironomids, which caused issues in Incheon tap water, were not found in Seoul.

On the 28th, the Seoul Metropolitan Waterworks Authority held a press briefing at Seoul City Hall and stated, "There were a total of 73 larva-related complaints received by the Seoul Metropolitan Waterworks Authority from the 14th to the 26th of this month, and detailed analysis by the Seoul Water Institute of tap water samples collected from these areas found no abnormalities."

Of the 15 larva specimens collected from complaint sites, analysis by the National Institute of Biological Resources under the Ministry of Environment identified 7 as moth flies, 4 as earthworms, 1 as moths, 1 as insects, and 2 as unidentified species not belonging to chironomids.

Among these, larvae found on the bathroom floor of an officetel in Jung-gu, Seoul on the 19th were confirmed to be earthworms, with the shower drain, where foreign substances had accumulated, identified as the main habitat.

Health and environmental experts concluded that unlike chironomid larvae, which can breathe underwater, moth fly larvae require atmospheric oxygen and cannot survive inside water supply pipes, and earthworms have low resistance to disinfection, making survival in chlorinated tap water difficult, thus ruling out tap water as the source. The Waterworks Authority also explained that adult moth flies were found in bathrooms where larvae appeared, and many water storage tanks were not hygienic or regularly cleaned.

On the 21st, as public concern over larvae in tap water grows, officials are collecting samples at the activated carbon adsorption chamber of the Ttukdo Arisu Water Purification Center in Seongdong-gu, Seoul. Photo by Mun Ho-nam munonam@

On the 22nd, a joint public-private investigation team consisting of experts in biology, water supply, and environment, along with researchers from the Seoul Water Institute, inspected the Gwangam, Amsa, Gangbuk, Guui, and Yeongdeungpo water purification centers. The inspection confirmed that there were no issues throughout the purification process, including granular activated carbon beds, at all purification centers operated by the city. Earlier, on the 20th, the Ministry of Environment's investigation team inspected the Ttukdo purification center, confirming the safety of all six Arisu purification centers in Seoul, according to the Waterworks Authority.

According to the authority, the advanced water treatment facilities at Seoul's purification centers are all fully enclosed, unlike those in Incheon, and insect screens and pest prevention facilities were well maintained. The internal and external environments of the activated carbon filtration beds were also well managed, according to the investigation team.

An official from the authority emphasized, "Currently, the backwash cycle of all granular activated carbon beds at purification centers is being strengthened to about every five days, and the ozone injection amount is increased to enhance sterilization, striving for optimal facility operation."

The Waterworks Authority plans to establish a continuous monitoring system by frequently sampling granular activated carbon beds at purification centers to check for larvae presence and to advance the tap water network management system to alleviate remaining public concerns despite confirming tap water safety. Additionally, rapid and accurate epidemiological investigations will be conducted regarding larva inflow routes in households reporting larvae complaints.

Baek Ho, head of the Seoul Metropolitan Waterworks Authority, said, "Although reports of larvae found in bathrooms and washbasins have increased amid growing public anxiety about tap water, there were no abnormalities throughout the entire tap water production and supply process. To ease citizens' concerns, we will form a team of pipe and pest control experts to conduct epidemiological investigations and perform detailed analyses of larva occurrence areas and facilities."

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