The increase of impervious area in cities caused the unbalanced water cycle system and the accumulated various
contaminants, which make troubles as introducing into watershed. In Korea, most of rainfall in a year precipitate in a
summer season. This indicate that non-point source pollution control should be more important in summer and
careful rainfall reuse strategy is necessary. Accordingly, the aim of this study is to monitor the characteristics of
rainfall contaminants harvested in roofs and to develop the rainfall treatment system which are designed to fit well in
a typical domestic household including rain garden. The rain garden consists of peatmoss, gravel and san to specially
treat the initial rainfall contaminants. For this purpose, lab scale experiments with synthetic rainfall had been
conducted to optimize the removal efficiency of TN, TP and CODcr. After lab scale experiments, field scale rainfall
treatment system installed as a pilot scale in a field. This system has been monitored during June to July in 2015 in
four time rainfall events as investigating the function of time, rainfall, and pollutant concentrations. As results, high
loading of pollutants were introduced to the rainfall treatment system and its removal efficiency is increased as
increase of pollutant concentrations. Since it is common that the mega-size of rainfall treatment system is not
attractive in urban area, small scale rainfall treatment system is promising to treat the non-point source contaminants
from cities. In addition, this small scale rainfall treatment system could have a potential to water resue system in
islands, which usually suffer the shortage of water.