A Comparative Study of Water Supply Systems in Depopulating Society Based on Water Quality and the Maintenance Costs

Abstract

 In the depopulating society, several problems arising out of the decrease in water demands should be considered. First, it will be difficult to continue investing adequate money in distribution systems. Second, increase of retention time of drinking water within the pipelines will lead to rise of the concentration of total trihalomethanes (TTHM) at the final faucet above the standard value. In this study, we suggested several scenarios for the future water supply system and compared them with two indices: total cost of maintenance and renovation, and concentration of TTHM. We set several patterns of population distribution for each scenario and analyzed how each pattern contributed to the outcome. The result showed that the scenario of introducing advanced treatment system did not improve the water quality if most people lived densely in one district. On the other hand, the scenarios of downsizing pipelines and introducing decentralized treatment systems decreased the concentration of TTHM regardless of population distribution.