Research On Life-Cycle Cost & Benefit Of Reclaimed Water Reuse Technology Based On System Dynamics

The "Thirteen Five" layout plan proposed: promote water-saving society construction comprehensively. Reclaimed water reuse is an important measure for the construction of water-saving society. it has become an important way to increase income & reduce expenditure, reduce water pollution, improve the ecological environment, alleviate the contradiction between water supply and demand and promote sustainable development of social economy. But national promotion range is not wide enough currently. Based on some people thinking reclaimed water reuse benefits not obvious, SD model reflecting the system structure and function of reclaimed water reuse technology life-cycle cost & benefit is established by means of system dynamics related theory and Vesim-PLE software. We use a reclaimed water reuse project of the new campus of a university in Gansu Province as an example to simulate and predict its life-cycle cost & benefit, so as to see comprehensive benefits of reclaimed water reuse technology visually. At the same time, different scenarios are analyzed through the change of decision making variables. The main research conclusions are as follows:(1) The life cycle of reclaimed water reuse technology is divided into four stages using life-cycle theory. The cost and benefit composition are decomposed, and its quantitative mathematical model is constructed accordingly.(2) Firstly, determine the purpose and boundaries of life-cycle cost & benefit system about reclaimed water reuse technology. Then the system is divided into two subsystems: life-cycle cost subsystem and life-cycle benefit subsystem. At last, the SD model of the whole system is constructed on the basis of structural analysis, and the relationships between variables are expressed quantitatively by writing structural equations.(3) In view of a reclaimed water reuse project of the new campus of a university in Gansu Province to study its life-cycle cost & benefit, determine the initial values of parameters in the model through collating, analyzing and calculating the 10 years operation statistical datas of this project and the relevant social-economic development datas of Gansu province.(4) Through the system running, forecast the life-cycle cost & benefit of this project. Results showed that: From the school’s point of view, the project life-cycle static net benefit is 15.4068 million yuan, the life-cycle dynamic net benefit is 72.1537 million yuan, static investment recycling period is 9 years. From the perspective of the whole society, the life-cycle static net benefit is 52.0728 million yuan, the life-cycle dynamic net benefit is 158.063 million yuan, which is 3.38 times and 2.19 times the net benefit from the angle of school respectively. Visibly, external indirect economic benefits of reclaimed water reuse technology are remarkable, and its social contribution is enormous. In addition, it can obtain that the reclaimed water running cost is 0.952 yuan per m3 including the infrastructure investment compensation fees and 0.525 yuan per m3 without compensation fees by simulation.(5) Different scenarios are analyzed by changing the different parameter values or combinations. The scenarios analysis of four solutions about investment and financing decisions shows that: the impact of planned repayment period to life-cycle cost & benefit is greater than that of self-financing. Relatively speaking, the repayment period is a sensitive factor, which explains why the school choose plan 1 reasonably from one hand. Scenario analysis is applied to municipal water pricing growth & annual average wage growth rate and daily maintenance level. The results show that: the changes of water price in future and daily maintenance level are important factors for the project life-cycle net benefit, annual average wage growth rate is not sensitive.