Research On Collaborative Environmental Benefits Of Energy Recovery From Wastewater Of Typical Industrial Sectors In Chinese Provincial Regions

With the rapid development of China’s social economy,a large amount of industrial wastewater has been generated,and there is also a huge demand for energy.Facing the dual challenges of environmental sustainability and energy security,energy resource recovery methods for wastewater are also constantly innovating,which is also an opportunity for the development of industrial enterprises.The energy utilization of wastewater can not only alleviate environmental and energy pressures,but also create additional value for enterprises and promote economic development.In order to provide reference for the widespread promotion of policies related to the energy utilization of wastewater,this study conducted a comprehensive analysis and evaluation of the synergistic environmental benefits generated by the energy utilization of high-organic-concentration industrial wastewater（HOCIW）at the provincial level in China.This study focused on the high organic content industrial wastewater generated by typical industrial sectors in the provincial regions of China in 2017.The study applied the life cycle assessment（LCA）method to identify the input and output of substances and energy in the wastewater treatment process.Then,eight environmental impact categories,such as global warming,ozone depletion,and eutrophication,were selected as the main environmental impact categories.The study used scenario analysis to evaluate the impact of the wastewater treatment process on the ecological environment under different scenarios and analyzed the synergistic environmental benefits brought by the energy utilization of wastewater.The results showed that:（1）At the national level,the standardized environmental impact scores of the two scenarios about high organic content industrial wastewater treatment varied between 0.0001 and 0.016 in each environmental impact category.The impact scores of eutrophication in the ocean and freshwater had the largest relative impact（>0.004）,followed by global warming,stratospheric ozone depletion,and terrestrial acidification（0.001～0.002）,and the impact scores of other environmental impact categories were less than 0.001.（2）In the baseline scenario,the environmental impacts of marine eutrophication and freshwater eutrophication are mainly derived from the waste disposal stage,while the impacts of other environmental impact categories mainly come from the digestion disposal stage.However,in the future scenario,the impact on stratospheric ozone depletion mainly comes from the waste disposal stage.（3）The avoided environmental impact scores for each environmental impact category are all below 0.002.The substitution of electricity has avoided emissions of CO₂,SO₂ and NO_x,resulting in negative scores in five categories,such as global warming,while the substitution of fertilizers has negative scores in seven categories,excluding marine eutrophication.（4）Compared with the baseline scenario,the standardized environmental impact scores of the future scenario have decreased significantly in all seven environmental impact categories,with reductions ranging from 34.5%to 557.8%.The reductions in six impact categories exceed 100%,indicating that more environmental benefits have been generated in those categories.（5）Eastern coastal provinces have a higher level of industrial development and produce more high-organic-concentration industrial wastewater.Therefore,utilizing the wastewater for energy production can not only offset the environmental impacts caused by the wastewater treatment process,but also generate certain environmental benefits in most impact categories.In contrast,in the central and western regions where the production of high-organic-concentration industrial wastewater is relatively low,its energy utilization will still have a negative impact on the environment in some impact categories.（6）In 2017,the substitutable electricity and fertilizer from typical industrial wastewater energy utilization in China were 9.8 billion k Wh and 449,000 tons,respectively.The province with the largest substitution of electricity and fertilizer is Shandong Province（1.7 billion k Wh and 76,000 tons）,followed by Guangdong Province（1.4 billion k Wh and 60,000 tons）.This study identified the key stages of the wastewater treatment process that have environmental impacts,evaluated the synergistic environmental benefits of wastewater-to-energy utilization at the national and provincial levels,and estimated the amount of electricity and fertilizers that can be substituted through wastewater-to-energy utilization.From the perspective of environmental impacts and energy potential,the synergistic environmental benefits of wastewater-to-energy utilization were analyzed,providing a methodological approach for quantifying the potential of wastewater-to-energy utilization and a scientific basis for formulating policies to promote it.By reducing the environmental impacts of the wastewater treatment process,the aim is to achieve the goal of enriching and optimizing the regional energy structure.