Potential Evaluation And Optimized Allocation Of Reclaimed Water Utilization In Northwest Inland Region

Reclaimed water plays an important role in maintaining the sustainable use of water resources as a relatively reliable alternative water source in the world.However,in the inland areas of northwest China,there are still obstacles such as insufficient funding,backward technology,and delayed planning for the promotion of sewage recycling.This paper constructs a system dynamics model that simulates the supply and demand of recycled water in the northwest inland region and a multi-stage and multi-objective non-linear optimization model for the distribution and distribution of recycled water based on the national key research and development plan "Integration and Application of Water Resources Security Guarantee Technology in the Northwest Inland Region".Systematic potential assessment and optimization of utilization models were performed for typical cities in northwest inland region.The results of the study show that reclaimed water in the northwest inland area has great development potential.In the future,it can alleviate regional water shortage problems and maintain urban ecological stability to a certain extent.This research provides a reference for the formulation and implementation of relevant local policies.The main contents and results of this paper are as follows:(1)An evaluation index system for the level of reclaimed water use was constructed by analyzing the impact of different natural and social factors on the use of reclaimed water in the northwest inland region.Then the five northwestern provinces,Jiangsu province,and Beijing were chosen to evaluate the current status of reclaimed water use using the analytic hierarchy process.The results show that cities with high levels of economic development have significantly higher levels of recycled water utilization than the Northwest cities.The sewage treatment and reclaimed water utilization rates in Gansu,Xinjiang,and Qinghai districts in the northwest inland region are all lower than the national average restricted by geographical conditions and regional economic constraints,of which Qinghai has the worst performance.(2)A system dynamic model for simulating changes in the supply and demand of urban reclaimed water was constructed.The reclaimed water supply and demand balance index(RWB)and utilization efficiency index(RWUE)were proposed as potential evaluation indicators.Urumqi,Xinjiang Province,Wuwei,Gansu Province,and Xining,Qinghai Province were selected as typical cities in the northwest inland region to simulate and predict the supply and demand of reclaimed water.Then a parts of system parameters were changed within the range of 10%-20% to observe the changes in the prediction results.The simulation results show that the adjusted RWB and RWUE of the three typical cities are closer to the ideal value,that is,targeted policy changes can accelerate the development of the supply and demand potential of recycled water in the northwest inland cities.(3)A city reclaimed water recycling model with the ecological reuse of reclaimed water as the core was constructed combined with the quality of reclaimed water and the demand of users.And then a multi-stage and multi-objective non-linear optimization model for urban reclaimed water allocation was established with the optimization goals of minimum water delivery cost and maximum water fee benefit.Finally,Urumqi,Xinjiang was taken as a case for optimal allocation calculation.The results show that reclaimed water can replace 37% of the city's tap water supply on the premise of maintaining the ecological stability of urban rivers and lakes landscape.