Abstract
The demand for water in a city area has enormously increased due to the concentration of population and improvement of the living quality. In this reason, the water shortage and the pollution by city sewage seem to be inevitable. For saving city water and meeting the demands from the city, the wastewater recycling system can be used, which makes used water reusable by a certain purification process. In Korea, the application of a wastewater recycling system to the buildings has continuously been adopted since its first appearance at the Lotte World Complex in 1989. However, the system has not been in fashion because of its high cost and users' negative attitude against recycled water. A research based on literature review and a case study for a recycling water system was carried out and an estimation and evaluation model was proposed. The results from the present study suggest that the optimal size of the recycling water system should be designed within 30-40% of total water demand in a building. Also, it was found that economic benefits could be expected within the payback period of 5.3 years by securing the operation rate over 70%.