Abstract
Material dynamics in urban areas with developed water supply and sewerage systems are determined not only by the natural hydrological circulation system but also by the artificial water circulation system. In this study, we used data collection and field survey to quantitatively analyze the dynamics of nitrogen, phosphorus, and silicon in the artificial water circulation system in Osaka City. The impact of scenarios that the future policies may change the water and material flow in the system was also evaluated.
This study revealed that the loading amounts of total nitrogen and total phosphorus added by domestic drainage were the most dominant factors that affect material flow in the system. Additionally, the dissolved silicon (DSi) input by uptake from the purified water sources and infiltration of the water from unknown sources into sewerage pipes also had considerable influence on the flow. In addition, DSi was not removed by water purification and sewerage treatment process, and it was transported conservatively within the system. Moreover, the results indicated that, in the future, when the use of groundwater for industrial purposes is promoted or also when the intrusion of water form unknown sources into sewerage pipes is prevented, the proportion of N, P, and Si discharged from the sewerage treatment plants will change greatly; this change could result in affecting the water quality and the ecosystem of rivers.
