On-site treatment is the process of treating wastewater near the place where it is discharged, so it doesn't go directly into rivers. This is different from the traditional approach that channels wastewater via the sewer networks to centralized treatment plants.

Given the public's high expectation and demand on the water quality, the Ministry of Environment (MOENV) has taken necessary measures since 2002, "the year of river pollution remediation; to combat pollution. With the assistance of the MOENV, local governments started water purification engineering projects by setting up gravel aeration, constructed wetlands, and community-based wastewater treatment facilities near the pollution sources and the confluence of polluted branch rivers. Through interaction with oxygen, soil, macrobiotics and plants, polluted water was purified, thus reducing the pollutants discharged into the rivers.

After the methodologies and techniques from Europe, US and Japan were officially introduced in Taiwan in 2002, on-site treatment projects were implemented at more than 30 locations one after another, including free-flowing surface water and constructed wetland of groundwater, underground infiltration, gravel contact aeration and oxidation, grassed swales and buffer zones, and artificial floating wetlands. These ecological projects of building on-site treatment facilities at the riverfront did not only achieve the goal of water purification. The ecological effects they brought along also gave riverfront a makeover, a new look with more recreational and educational values.