Life Cycle Environmental Impact Assessment On Implementation Of Category Ⅳ Equivalent Wastewater Treatment Plant Effluent Standard In China

The establishment of discharge standards for water pollutants is one of the important issues for water pollution control.In recent years,many places in China launched local sewage treatment plant CategoryⅣEquivalent pollutant discharge standards to achieve the goal of water pollution control action plan,which triggered extensive discussions and debates in the this industry.Overall,main controversies tended to be the trade-off between necessity of water environment management,technical feasibility,techniques and impacts caused by upgrading wastewater treatment plant for implementation of CategoryⅣEquivalent standard,however the whole social life cycle environmental impact caused by implementation of CategoryⅣEquivalent standard has not been brought into focues and studied.It is no doubt that Upgrading wastewater treatment plant for implementing CategoryⅣEquivalent standard could improve the water environment,but it may bring about life cycle environmental impact due to new policy formulation and implementation,equipping new facilities and new materials,increasing energy and reagents.This thesis aimed at using Life Cycle Assessment（LCA）,from the aspects of standard formulation and implementation process,as well as upgrading wastewater treatment plants,to analyse life cycle environmental impact of implementation of CategoryⅣEquivalent effluent standard in our country,in order to identify the important component and to obtain environmental impact of policy making,so as to provide reference from the prospective of life cycle environmental impact for implementing CategoryⅣEquivalent effluent standard.The thesis summarised and analysed the state-of-art environmental sustainability issues concerning CategoryⅣEquivalent wastewater treatment effluent standard through literature review.On the basis of the ISO 14040 and ISO 14044 life cycle methodology framework,life cycle environmental impact of the CategoryⅣEquivalent standard making procedures（subsystem 1）and upgrading wastewater treatment plants in compliance with CategoryⅣEquivalent standard（subsystem 2）were evaluated.Functional units of these subsystems were considered to be one CategoryⅣEquivalent effluent standard and 1m³ of treated water.For subsystem 1,activities were divided into indoor and outdoor for inventory analysis,of which the former was mainly collected through the literatures and design manual,and the latter were collected via information from the Baidu map open source platform,data preprocessing by Arc GIS,calculation of the geographical distance matrix and design of ant colony optimisation algorithm to achieve optimal traffic route by Python 3.7.For Subsystem 2,existing data from literature in combination with design manual,design standards,engineering budget manual and other materials was to complete the Subsystem 2 data inventory.Life cycle environmental impact were analysed via Ga Bi Education 9.1 with CML 2001 methodology.Abiotic Depletion（non fossil）,Abiotic Depletion（fossil）,Acidification Potential,Eutrophication,Freshwater Aquatic Ecotoxicity,Global Warming,Global Warming（excluding biogenic carbon）,Human Toxicity,Marine Aquatic Ecotoxicity,Ozone Layer Depletion,Photochem.Ozone Creation,Terrestric Ecotoxicity were selected as impact categories for classification,characterization and normalization,to quantify,compare and identify environmental impact and their significance.Uncertainty of travel mode,number of participants,and treatment scales of upgraded CategoryⅣEquivalent wastewater treatment plants were examined for comprehensively studying the variation of the system environmental burden when these conditions change.The results indicated that:（1）in the life cycle of CategoryⅣEquivalent making process,Marine Aquatic Ecotoxicity was the one of the major environmental impact categories,followed by Abiotic Depletion（fossil）.Indoor activities concerning technical review,workshops and training,and environmental practioners’related works for CategoryⅣEquivalent standard contributed to mostly these impact categories with potential about 6.33E+11 kg DCB eq.and 3.35E+10 MJ respectively.The potentials of Ozone Layer Depletion and Abiotic Depletion（non fossil）in this subsystem were relatively small,with which were 8.82E-09kg R11 eq.,and 2.67E-01kg Sb eq.,respectively.（2）Within the life cycle of upgrading sewage treatment plants for implementing CategoryⅣEquivalent standard,the environmental load in the operation phase was much higher than that in the construction phase.The construction and operation phase enabled environmental benefits for Ozone Layer Depletion and Eutrophication respectively,which reduced by 5.86E-11 kg R11 eq.,and 2.24E-02 kg Phosphate eq.,respectively.Global warming potential was the largest in the operation stage,with a potential of 3.01E+03 kg CO₂ eq.Human toxicity was the most significant environmental impact category in the construction phase.Global warming was the most important environmental impact category in the operation stage as well as in the life cycle of upgrading sewage treatment plant.（3）Within the life cycle of the overall system,the environmental impact of upgrading sewage plants for implementing CategoryⅣEquivalent standard was far greater than that of CategoryⅣEquivalent standard making process,and the difference in magnitude of the characterisation results were about 10²～10⁵;The two subsystems also have different dominant categories,namely Marine Aquatic Ecotoxicity and Global Warming respectively.The normalised result showed that Global Warming was the most significant category of the overall system,with a normalized value of about 4.9E+02.（4）Within the life cycle of the formulation process of CategoryⅣEquivalent standard,the change of travel mode caused great fluctuation on environmental load;For short trips,the environmental load caused by high-speed trains was relatively smaller but not obvious,compared to that by regular trains.Transport over long distances using high speed railway instead of plane resulted in shift of dominant environment load,long distance travel by airplane travel caused greater impacts on Abiotic Depletion（fossil）,Eutrophication,Freshwater Aquatic Ecotoxicity,Global Warming,Human Toxicity,while using high-speed railway,unlike planes,it mainly affected Marine Aquatic Ecotoxicity,Ozone Layer Depletion and Terrestric Ecotoxicity Potential.Adopting high-speed railway as the main mode of travel may reduced more environmental footprint compared to that by aircraft.By analysing the uncertainty of participants,it could be seen that the change of environmental impact load increased with the number of participants increased.The change of the number of participants mainly affects the production of printing materials for the conference program and proceedings of the academic conference,the bags used in the conference,energy consumption of the conference room and overnight stay of participants.No obvious influence on the process of CategoryⅣEquivalent standard making by changing treatment scale of the upgraded sewage treatment plant implementing CategoryⅣEquivalent standard.（5）For the life cycle of upgrading sewage treatment plants that implement CategoryⅣEquivalent standard,changes in travel mode and number of participants had no direct impact on upgrading such sewage treatment plants.In addition to Eutrophication and Ozone Layer Depletion,as the treatment scale of sewage treatment plant increased,potentials of other environmental impacts increased,while these two categories behaved oppositely,indicating that constructing and operating sewage treatment plants with CategoryⅣEquivalent standard could reduce burden of the Eutrophication and Ozone Layer Depletion at the same time,but was also associated with other environmental problems.（6）The comprehensive analysis of the two subsystems shows that when the daily treatment scale equivalent of sewage treatment plants with CategoryⅣEquivalent standard was about 10,124,000 m³/d,the eutrophication and ozone layer depletion potential caused by the two subsystems were close to each other,indicating that the elimination benefit of sewage treatment plant to environmental pollution was not obvious.