Study Of Phosphorus Flow In The System Of Urban Household Consumption

With the process of urbanization in China, more and more people lives in urban areas. Statistics show that China’s urbanization rate has exceeded50%, and there is an increasing trend in the future. As a consequence of urbanization, a large number of industrial wastewater and domestic sewage are discharged, which lead to the widespread contamination, especially the eutrophication of urban surface water. Studies have shown that excessive input of nitrogen (N) and phosphorus (P) tend to cause eutrophication and P is considered as the critical control factor. As an essential element of human life, P flows with the family metabolic process. The model and path of P flow are closely related to the quality of ecological environment. With the growing of income and urbanization, the consumer behavior and consumption structure of urban residents will also change. These changes will drive the adjustment of the model and path of P flow in the system of urban household consumption, which will have a major impact to the urban ecological environment, especially the surface water. In this study, we applied Substance Flow Analysis (SFA) to establish the phosphorus flow analysis framework and its accounting model in the system of urban household consumption. Based on the accounting model, we carried out quantitative analysis of phosphorus flows in the system of urban household consumption in Chaohu City,2008. Then we used phosphorus emission index study the characteristics of phosphorus emissions in the system of urban household consumption in Chaohu Lake Basin. Finally, scenario analysis was carried out to analysis the characteristics of phosphorus flows in the future after changing food consumption structure. The results were shown as follows.(1) The input of food consumption was the most important part of P input in the system of urban household consumption. The total input of P in the system of urban household consumption in Chaohu City was186.57t in2008and more than90%was caused by food consumption. The input of P caused by dining out was obviously. Our research showed that, the amount of input P caused by dining out was about13.17tP, accounting for nearly7.1%of food consumption in the system. Due to a series of policies of banning or controlling P for solving eutrophication of local surface water, non-phosphorus and low-phosphorus detergent are widely used in the region. Thus, the amount of input P in the form of detergents was relatively small, less than1%of the total input in the system.(2) Human waste was the most important output flow of P in the system of urban household consumption. The amount of output flows of P in the form of human waste was93.77t, about51%of the total P output. The P output of garbage accounted for41.54t, and lots amount of the P were collected for disposal and others (nearly12.47tP) remained within the system. Nearly a half of them were collected into the sewage treatment plant for further treatment, and others (about62.64tP) were discharged directly, which may adversely affect surface water.(3) Urban sewage collection and treatment system could effectively reduce the amount of P that discharged into local surface water from the system of urban household consumption. The total amount of P discharged from the system of urban household consumption of the whole Chaohu Lake Basin was1534.69t. About618.12tP eventually entered local surface water, and the remaining60%(916.57, tP) was collected to enter the sewage treatment plant, which greatly reducing the amount of P that was discharged into surface water.(4) Optimization of food structure may have has two opposite effects. For the purpose of a balanced diet to optimize the food structure, will cause increased P input in food consumption per capita, and thus, the difficulties in the optimization and regulation of phosphorus will also increase.