Life Cycle Assessment And Cost Of Ecological Restoration Technology For Polluted River

Urban rivers have important ecological functions,but the surface water quality in China has been seriously deteriorated,which endangers human health and affects the stability of the ecosystem in this regard.China has issued a series of laws,regulations and policies to emphasize the importance and urgency of the restoration of polluted rivers,and to regulate the restoration projects.As an important measure,ecological restoration technology has been mentioned many times.The combined ecological restoration technique of microbial enhanced degradation,aeration and ecological floating bed has been widely used in the restoration of polluted rivers in China,and the water quality has been improved significantly.But the production,installation and maintenance of equipment in restoraion projects not only consumpts resource and discharges pollution,but also need financial support.Along with the advancement of the national polluted river restoraion,it is necessary to identify the key process from the perspective of life cycle,and put forward improvement suggestions which are resource effective,environment friendly and cost saving.At present,the research about the life cycle of polluted river restoration is limited both at home and abroad.This study take the relatively mature research experience of the life cycle of wastewater treatment technologies for reference;chose three common and typical technologies of polluted river ecological restoration,which are bio-cord,microporous aeration and ecological floating bed,to make life cycle assessment and life cycle cost analysis with the aid of GaBi 6 software.The life cycle assessment method used in this study was CML 2001-dec.07,Experts IKP.The environmental impact assessment categories include abioticdepletion potential(ADP),acidification potential(AP),eutrophication potential(EP),global warning potential(GWP,100 years),ozone layer depletion potential(ODP),photochemical oxidation potential(POCP).The results of life cycle environmental impact assessment(LCIA)show that the operation and maintenance contributes more than 99%of LCIA's total result.The main impacts in the production and installation stage are ADP and GWP.Bio-cord reactor contributes the most to the LCIA's total result and GWP.The key process of GWP is the production of the square steel frame of bio-cord reactor,and the key factor is CO2.However,the adoption of alternative wooden frame and PVC pipe frame can reduce the LCIA's total result of bio-cord reactor's production and installation by 86.8%and 85.7%respectively.The production and installation of microporous aeration equipment makes a great contribution to the total EP and ODP,the key process of EP is the production and machining process of the steel of blower,and the key factors are phosphate and NOx.Ecological floating bed contributes a lot to ADP and AP.The key processe is the production of HDPE floating bed blocks,and the key factors of AP are SO2 and NOx.EP,GWP and AP are the main influences in the operation and maintenance stage.Except EP,the other five selected environmental impact potentials in this study show positive results.Microporous aeration contributes the most to the LCIA's total result;and contributes almost 100%to ADP,AP,ODP and POCP;contributes more than half to GWP.The key process of the microporous aeration operation stage was the power consumption of blowers,accounting for 54.7%of the LCIA's total result of operation and maintenance of minfeng river ecological restoration project.The reduction of EP mainly due to the bio-cord from bio-cord reactor and ecological floating bed.The key factor is NH3-N.But CO2 and N2O generated by microbial nitrification and denitrification contributes a lot to GWP,which leads to a positive LCIA's total result of bio-cord.Ecological floating bed plant reduces the LCIA's total result,EP and GWP,but only by a small margin.The contribution of GWP is complex:the carbon sequestration of plant cuts the GWP;but the emission of N2O from microorganism in plant roots,and the emission of CH4 and CO2 from plant residues landfill makes positive contribution to GWP.The results of Llife cycle cost show that operation contributes more than installation,and bio-cord reactor,microporous aeration system and ecological floating bed contribute 10.05%,55.86%and 34.09%to the total cost of restoration project.During installation stage,the cost of materials accounts for the vast majority.Microporous aeration system and ecological floating bed contributed respectively 81.18%and 18.82%to the total costs of maintenance,bio-cord reactor does not incur cost because it doesn't require maintenance.The maintenance cost of microporous aeration system mainly comes from the power consumption of blower,which accounted for 71.57%.The cost of aerator pipe replacement and labor should not be ignored.In addition,scrap recycling can generate revenue to cut costs.The cost of ecological floating bed maintenance mainly comes from the purchase of aquatic plants and the labor to grow and harvest plants.Based on the research results,and in order to further reduce the environmental impact and economic cost of the system,the following suggestions are proposed:1.Select wooden frame or PVC pipe frame in bio-cord reactor;2.Select high-efficiency and energy-saving blower,use automatic monitoring equipment to make low-intensity and intermittent aeration come true;3.Select aquatic plants with high survival rate and use miniaturized and intelligent aquatic plant harvesting equipment;4.Realize resource utilization of plant residues;5.Optimize the energy structure and advocate the use of clean and renewable energy.