Research On Quantification Method And Influence Factors Of Desalination Water Footprint

During the China economic development,one of the limiting factor is the shortage of water resources.Increasing revenue and reducing expenditure is the fundamental measure to realize the sustainable development of water resources.So,it is essential to construct the desalination plants to solve the problem of freshwater resources shortage in China coastal areas.China's seawater desalination industry is developing rapidly,but its impact on water resources and environment is the most important problem that must be solved.With reference to advanced domestic and foreign seawater desalination research,experts have proposed comprehensive evaluation methods such as analytic hierarchy process and fuzzy comprehensive evaluation method to access the impact of seawater desalination on resources and environment.These methods are subjective and cannot quantitatively analyze the impact.Therefore,the most urgent task is to establish an evaluation method that can quantify the impact of seawater desalination on resources and environment.In this research,a water footprint model is used to establish a quantification method for the environmental impact of typical desalination processes,and to evaluate the impact of the quantification results,and propose improvement suggestions for the key factors in the evaluation.First,through the water footprint life cycle model,a universal quantitative method framework for seawater desalination is established,and the life cycle inventory of two seawater desalination processes,reverse osmosis(RO)and low-temperature multi-effect distillation(LT-MED)are analyzed according to this framework.Two quantitative methods of water footprint for RO and LT-MED desalination are established.Secondly,quantifying the water footprint of the two RO and four LT-MED desalination plants in the sample shows that the water scarcity footprint of the six desalination plants ranges from 0.00941 to 0.0756 m³/m³.In the water degradation footprint,the acidification footprint varies from 0.091-1.04 kg SO₂ eq/m³,the eutrophication footprint varies from 0.031-0.26 kg PO₄^3-eq/m³,and the ecotoxic footprint varies from 5.46 to 43.92 CTUe/m³.Based on the quantification results of various water footprints,a ten-point scale is used to formulate water footprint scoring standards.Finally,the impact evaluation of the water footprint quantification results is carried out,and the water footprint changes of different processes and different seasons and the key influencing factors in the water footprint are investigated,and suggestions for improvement are put forward for the key factors.The results show that the overall water footprint of the RO is relatively lower than LT-MED meaning the negative impact of RO on the environment is smaller.The key factor of the water scarcity footprint of the RO and LT-MED is power consumption,and the power consumption of steam is the most influential power consumption in LT-MED.In the water degradation footprint,the main influencing factors of the three water degradation footprints in the two processes are scale inhibitors.In addition to the scale inhibitors,the key influencing factors of the water degradation footprint in RO include carbon dioxide,calcium carbonate,and membrane module consumption.The important factors in LT-MED degradation footprint include the consumption of steam,flocculant,cleaning agent and defoamer.In this research,we use the water footprint model to establish a quantitative evaluation method for RO and LT-MED processes,and provides a solution for water resources environmental management of seawater desalination from a new perspective.