Construction And Application Of Water Footprint Impact Quantitative Model In China

Currently,water resources shortage and pollution seriously threaten human health and ecosystem quality.Thus,the environmental risk of the water environment in China should be quantified,assessed and managed in a scientific and systematic manner.Water footprint analysis,which is a comprehensive index used to evaluate water consumption and pollution status,can effectively address this problem.However,the traditional water footprint analysis method only can evaluate the amount of water consumption and pollution.Moreover,quantifying environmental impact and dealing with complex industrial systems are difficult to implement.Accordingly,the life cycle assessment method can effectively solve the aforementioned problems by identifying the environmental impact during the entire life cycle and identifying the key factors.Therefore,this paper uses the life cycle assessment method to quantify water footprint impact.The majority of the life cycle water footprint analysis models have often focused on the water scarcity footprint,whereas a few models have concentrated on water pollution footprints(e.g.,carcinogens,acidification,and freshwater ecotoxicity footprints).Some studies have used life cycle assessment to directly quantify water footprint,thereby leading to overestimation owing to the non-exclusion of intake pathways unrelated to the water medium and the environmental impact of residual pollutants in the air and soil media.Current studies have often failed to consider the air and soil pollutants affected the water quality indirectly,and this will result in low water footprint quantification results.Additionally,geography,water quality,environment,population,technical level,and other basic data needed in model construction and application have presented significant regional differences.Thus,adopting foreign models and databases does not meet China's conditions.The current research proposes a general indigenized life cycle water footprint impact quantification model.This model can quantify the environmental impact of water resources consumption and water environment pollution caused by human activities,and it can describe the relationship between industrial activities and natural ecosystem to identify the key factors.This paper also uses a papermaking enterprise,coal-based electricity generation industry,and industrial wastewater discharge as examples to conduct the application example research at the micro-,meso-and macro-levels,respectively.The detailed study is presented as follows.Firstly,this paper built a general indigenized life cycle water footprint impact quantification model based on China's situation.This model involved the inventory construction method,selection of impact categories at the midpoint level,calculation of characterization factors,and human health and ecosystem quality damage assessment.This model established the analysis boundary according to the ISO 14046 international standard,and then simulated the migration and transformation of over 3000 types of substances which can affect the water environment through the multi-media fugacity model to eliminate the components that do not enter the water medium finally.Meanwhile,the intake pathway only considered the oral intake related to the water media.Accordingly,the relationship between the inventory and six midpoint impact categories was identified,and 35,374 characterization equivalent factors were calculated at the midpoint level.The assessment of human health and ecosystem quality damage can be conducted as well.Secondly,the feasibility of the application of the proposed model at the micro(enterprise)level was verified through a water footprint analysis case study of one paper-making enterprise.The key factors and reduction scheme was also applied.It was found that carcinogens and non-carcinogens provided over 95%human health damage during the life cycle of straw pulp-based printing and writing paper production,and the ecosystem quality damage mainly came from freshwater ecotoxicity and water eutrophication footprints.The impact of other midpoints was less than 3%.To reduce the water footprint impact,the water footprint of the organic fertilizer recovery,wood pulp production,and chemical preparation should be reduced.When the influence of the aforementioned processes is reduced by 5%,the water footprint at the midpoint and endpoint levels will decrease between 0.3%and 3.4%.To control the water footprint impact,the enterprise can apply wood pulp with elemental-chlorine-free bleaching and black liquor recovery technology.Clean energy,such as hydropower or recycled energy,was also suggested.Additionally,reducing the water footprint impact of wastewater treatment by selecting reasonable wastewater treatment process(e.g.,deep-well aeration and biofilm filtration)and conducting wastewater recycle can obtain significant environmental benefit.Meanwhile,decreasing direct water consumption can facilitate the reduction of the water scarcity footprint.For pollutant emission control,the total phosphorus,total nitrogen,COD,BOD5,and heavy metals(e.g.,chromium,arsenic,mercury)emissions became points of concern.Thirdly,the feasibility of the application of the proposed model at the meso(industry)level was verified through the water footprint analysis of coal-based electricity generation industry in China.The characteristics and reasons of time series fluctuation were also analyzed.These can provide beneficial information for the management and control of water resource consumption and water environment pollution derived from the entire life cycle of the coal-based electricity generation industry in China.The water footprint impact on human health has been increasing from 2006 to 2015.Although such an effect began to decline after reaching its peak in 2013,it continued to increase by 47.3%as of 2015.The ecosystem quality damage was reduced by 26.0%during this period owing to a reduction in sulfur dioxide,COD,and total nitrogen emissions.In 2015,the water footprint impact on human health and ecosystem quality of 1 kWh of coal-fired electricity supply in China was from 1.2×10-8 to 2.3×10-8 Daly and from 4.0×10-4 to 7.5×10-4 PDF.m2.yr,respectively.For human health damage,it mainly came from carcinogens and non-carcinogens caused by arsenic and chromium emitted from indirect processes,such as raw coal mining and washing,transportation,solid waste disposal,and crude oil and chemical production,as well as mercury emissions during the power generation stage of coal-fired power plants.The ecosystem quality damage was mainly from freshwater ecotoxicity and aquatic eutrophication resulting from the aforementioned indirect processes.Meanwhile,the acidification footprint caused by sulfur dioxide emission from coal-fired power plants played important roles.However,the reduction of other key pollutants(i.e.,total phosphorus and heavy metals)is not significant.Thus,the recommendation is to add these indicators in the total national amount control policy,Moreover,increasing the raw coal inclusion rate is effective to mitigate the impact of mercury and transportation.However,similar to pithead power plants and "West to East Power Transmission" project,these measures further aggravate the water shortage of main coal power production bases in China.Hence,the regional water resources carrying capacity should be considered comprehensively and the scale of the coal power industry must be limited strictly,particularly in areas with serious water shortage during the development of China's coal power generation industry.Another suggestion is to develop clean energy with low water resources consumption Additionally,railway and water carriage are beneficial to further reduce the water footprint impact.Fourthly,the feasibility of the application of the proposed model at the macro(region or country)level was verified through the water footprint analysis of industrial wastewater discharge in China and its temporal and spatial evolution regularities exploration.This information can provide theoretical basis and data reference for the entire life cycle control and precise management of China's industrial wastewater discharge.From 1992 to 2015,the water footprint impact showed a downward trend,and human health damage decreased by 89.84%.Given that ammonia nitrogen,which is the key pollutant of ecosystem quality damage,was listed in the statistics after 2000,the ecosystem quality damage showed a sharply increasing trend initially and declined significantly thereafter.This indicated that the control of ammonia nitrogen is necessary and effective.The relationship between the water footprint impact and growth of industrial output value was generally harmonious.The impact of industrial wastewater discharge on the water environment was effectively restrained while maintaining economic growth.However,the water footprint impact continued to be higher than the economic growth in some years.Therefore,management should be strengthened to prevent a rebound.For human health damage,non-carcinogens were higher than carcinogens,while the contribution of aquatic eutrophication and acidification was significant for ecosystem quality damage.To control human health damage,it was effective to control arsenic emissions from nonferrous metals mining and dressing,raw chemical materials and chemical products,and smelting and pressing of nonferrous metals industries as well as hexavalent chromium emitted from metal products industry.The suggestions for controlling ecosystem quality damage included focusing on COD and ammonia nitrogen emitted from the aforementioned four industrial sectors,and the contribution of food processing;papermaking and paper products;textile industry;petroleum processing,coking,and nuclear fuel processing;food production;and liquor,beverage and refined tea should not be disregarded.Meanwhile,spatial differences should be considered to improve the efficiency of water footprint impact reduction.For example,industrial wastewater recycling was suggested to be strengthened in Jiangsu,Guangdong and other eastern regions which presented enormous wastewater discharge.Moreover,it was encouraged to improve the cleaner production level in the northwest regions with high water footprint impact per ton of wastewater discharge.For Hubei,Hunan,Henan,Jiangxi and other provinces with significant unit water footprint impact and wastewater discharge,these areas should be focused and consider all aforementioned measures.Additionally,transformation and upgrading of industrial structure is necessary.Overall,a new indigenized life cycle water footprint impact quantification model with wide application pathway is conducted using the life cycle assessment method Meanwhile,feasibility and reliability of the multi-dimensional application are verified by case studies of the different geographical regions or time scales at the micro-,meso-,and macro-levels.This can modify the model and provide theoretical,data,and decision support for the source prevention,the entire life cycle control,and efficient treatment of water resource consumption and water environment pollution caused by China's industry.It can also provide theoretical support and practical experience for the life cycle water footprint assessment of other countries or industries.The innovation of this study includes:(1)a life cycle water footprint impact assessment model in accordance with the ISO 14046 international standard is established;the proposed model only consider the pollutants enter freshwater after migration and transformation in multi-media,and the intake pathway unrelated to water environment is excluded;(2)this study firstly proposed a life cycle water footprint quantization model that integrates water scarcity impact and ecosystem and human health damage of water pollution,and it can be applicable to China's actual situation;(3)this study completes the water footprint analysis of industrial systems at the enterprise and industry levels.