Climate change influences both water availability and water quality through floods and droughts [1
]. In Korea, the characteristics of water sources and their availability have been affected by economic growth, insufficient water management, and uncertainties due to climate change [2
]. Therefore, it will become more difficult to secure clean water during extreme meteorological events. Korea is also included among the world’s water-stressed nations between 2000 and 2025 [3
]. South Korea is heavily dependent on its surface water for sources of drinking water, and approximately more than 90% of its drinking water comes from a river or man-made reservoir. The rainfall from June to September provides nearly 70% of the regional drinking water supply [4
]. The mean annual rainfall is 1274 mm, and heavy rainfall that occurs during the summer leads to water shortages during the dry season (spring). Environmental accidents, including the contamination of tap water sources in the 1990s, raised many concerns and caused people in Korea to be reluctant to use tap water as drinking water [2
]. Therefore, there is a need to find other water resources that are safe and to improve the public view of tap water quality.
When surface water’s characteristics change due to extreme weather events, conventional water treatments have difficulty securing high quality water resources. To secure high quality water resources, alternative water resources such as managed aquifer recharge (MAR) systems were investigated [5
]. MAR systems use natural water treatments and are effective at removing biodegradable organic matter. MAR systems such as riverbank filtration (RBF) are emerging in Korea as an alternative solution [2
]. RBF is a water treatment process that uses the physical, chemical and biological degradation processes of aquifers [6
], and it is a nature-friendly water treatment process that removes pollutants without using chemicals [8
]. RBF is also effective at alleviating the production of disinfection by-products and reducing trace organic contaminants [9
]. In addition, it is also suitable for water safety and management [8
]. In the early 2000s, a RBF system was first introduced to improve the water quality of drinking water resources in South Korea, especially in the regions where there was poor water quality for a decade due to the wastewater effluents discharged from local industries. A number of chemical spills had occurred in the river, which caused people to lose confidence in tap water quality [5
A number of cities located downstream of the Nakdong River (Busan, Korea) are vulnerable to various water pollution sources and the seasonal water quality changes. Therefore, it is necessary to improve their water treatment system by improving the water source’s quality. Currently, there are three drinking water treatment plants that are currently providing water via RBF using the Nakdong River (Table 1
). The city of Changwon, which is on the Nakdong River in Korea, has been providing 80,000 m3
/day of drinking water since 2006 using RBF systems with vertical and horizontal collector wells. This system was the first RBF site installed to supply drinking water in South Korea. The city of Gimhae, South Korea, is currently providing 127,000 m3
/day via RBF (designed capacity: 180,000 m3
/day). Moreover, the Korea Water Resources Corporation (K-Water, Dajeon) in South Korea is currently investigating potential RBF sites that can supply 680,000 m3
/day to cities including Busan that are located near the lower part of the Nakdong River. This field study of two vertical wells will be used for the design of the horizontal collector wells that contribute part of the water supply to the city of Busan.
Before the installation of eleven horizontal collector wells, which provide 280,000 m3
/day, the field study was carried out using two vertical wells to investigate the quality of RBF. To improve the post-treatment requirements after the RBF, there is a need to investigate the water quality of RBF filtrates, including the dissolved organic matter’s characteristics. Previously, Lee et al. [5
] investigated the performance of RBF filtrates by comparing river water quality. However, there were no studies conducted on the fate of dissolved organic matter characteristics during RBF from a field study in South Korea. Moreover, there has been no report on using vertical wells to determine the depths of the laterals for horizontal collector wells.
The objective of this study was to conduct a detailed investigation of the characteristics of dissolved organic matter during soil passage using two vertical wells along the Nakdong River, South Korea (January to June, 2011). This study also investigated the removal efficiency of dissolved organic matter and the turbidity of two vertical wells whose screens are located at different depths (i.e., sand and gravel layers). The performances of the vertical wells at different pumping rates were also investigated. The water quality characteristics from two different vertical wells helped to determine the depth of the laterals for horizontal collector wells, even when there were other factors that needed to be considered (such as quantity).