The Optimal Management Strategy Of Shale Gas Wastewater Based On Life Cycle Assement

Shale gas is an alternative energy with huge economic value and broad resource prospect,which has been widely concerned in recent years.However,the hydraulic fracturing technology used in the mining process consumes a lot of water and produces high salinity flowback / producted water containing complex organic compounds,which may induce the risks of water shortage,environmental pollution,human and ecological health damage.Although there have been many studies on the evaluation of shale gas wastewater treatment and disposal technologies,most of them focus on the analysis of the advantages and disadvantages of the technology,and lack of research on the impact of its ecological environment.In order to reduce the ecological environmental risks of shale gas mining and maximize the use of water resources,it is of great significance to explore the optimal management strategy of shale gas mining wastewater.Therefore,this paper studies the management strategy of shale gas wastewater based on life cycle analysis,uses analysis tools such as Simapro to construct corresponding evaluation indicators,and establish a comprehensive evaluation system for shale gas wastewater management,and select management plans from three aspects: human health,ecosystems,and resource depletion.Through literature and field surveys,this paper summarizes the management models,wastewater quality and typical wastewater treatment technologies of shale gas wastewater at home and abroad.According to the current status of shale gas wastewater treatment and disposal,we propose to give priority to the internal reuse,that is reuse for subsequent hydraulic fracturing.When the internal reuse is difficult or impossible,the shale will be discharged after treatment to achieve maximum water resource regeneration.Drawing on the idea of life cycle assessment,based on the above two types of management models,we select typical wastewater treatment technologies for inventory analysis,and we use the Ecoinvent database and Eco-indicator 99 evaluation methods to evaluate the treatment technologies.According to the analysis results of characterization,damage evaluation,and standardization,we recommend Coagulation-Flocculation for the internal reuse.For the removal of organic compounds,we recommend use the Biological Aerated Filter and the Electro-flocculation technology of the iron electrode.For the desalination of wastewater with lower salinity,the ecological environmental impact of Forward Osmosis is lower than Reverse Osmosis,but the desalination effect of Reverse Osmosis may be better.For the desalination of wastewater with higher salinity,we recommend use Multiple-Effect Evaporation with Mechanical Vapor Recompression.In order to verify the operability of the evaluation method,this paper takes the produced water treatment project of the Fuling shale gas as the research object for case analysis.The results show that the impact of the produced water treatment project in the Fuling shale gas on the ecological environment is: human health > resource depletion >ecosystem impact,and the main influencing factor in the pretreatment stage is the use of chemicals,while advanced treatment and evaporation of concentrated water is electricity.Through the comprehensive evaluation results,the pretreatment stage is the main impact stage of the ecological environment in the produced water treatment project of the Fuling shale gas.Based on the above research,the paper proposes an optimization plan that can be referred to.By establishing a life cycle assessment system for the management of shale gas wastewater and further improving the inventory data,this study provides a new idea and method for the management of shale gas wastewater.The results can provide reference for decision makers of shale gas development companies and relevant environmental protection departments.