| In recent decades,with the rapid development of China’s industry,the continuous increase in the use of nitrogen fertilizer,the increasing population and the burning of fossil fuels,the nitrogen load in the ecosystem has been increasing.Therefore,how to improve the efficiency of urban sewage and industrial wastewater treatment and reduce environmental nitrogen load has become an important means of water environmental nitrogen index in China.To establish a more comprehensive and scientific water treatment technology and process nitrogen load removal efficiency evaluation method is to optimize the urban sewage and industrial waste water treatment technology system,and effectively improve the efficiency of nitrogen load removal efficiency.In this paper,the evaluation of nitrogen in waste water is limited to the process of water import and export,and the comprehensive evaluation method of nitrogen pollution removal efficiency in the whole process of sewage treatment is lack.From the point of view of life cycle evaluation,we use N-PRINT for reference.The core idea is to establish a nitrogen Footprint Assessment Model for evaluating the whole process treatment effect of sewage sludge treatment system,and to use this model to carry out 3 sewage treatment for BNR-MBR,MSBR and MBR,as well as BNR-MBR+ agricultural use(B1),BNR-MBR+ landfill(B2),BNR-MBR+incineration(B3),MSBR+ agricultural use(MS1),MS.BR+ landfill(MS2),MSBR+incineration(MS3),MBR+ agricultural use(M1),MBR+ landfill(M2),MBR+incineration(M3),9 kinds of sewage sludge combination treatment system,an empirical study of nitrogen footprint.The main achievements of this paper are as follows:(1)based on the perspective of life cycle assessment,a systematic studyboundary is established not only of the technological process of the upstream and downstream of the sewage treatment system,but also the management and support of the lateral objective,and a nitrogen Footprint Evaluation Model of the sewage sludge treatment system is established to scientifically evaluate the sewage sludge combination on a larger scale.It provides new ideas and effective tools to deal with nitrogen removal efficiency.(2)In the study of sewage treatment,the nitrogen footprint of the effluent was 69.35%,the nitrogen footprint of the sludge was 27.74%,the power nitrogen footprint was 2.78%,the nitrogen footprint of the effluent was 64.44%,the nitrogen footprint of the sludge was 33.32%,the power nitrogen footprint was 2.06%,and the nitrogen footprint of the effluent in the MBR process was 78.28%in the MBR process,and the nitrogen footprint of the effluent in the MBR process was 78.28%and sludge nitrogen.The footprint is 19.73%,and the power nitrogen footprint is 1.98%.In the three sewage treatment processes,the nitrogen footprint of the water entering the environment is the largest,followed by the nitrogen footprint of the sludge,the second is the power nitrogen footprint,and the nitrogen footprint released into the air is less.Under the same influent conditions,the nitrogen footprint of three processes of BNR-MBR,MSBR and MBR was estimated.The results showed that the comprehensive removal rate of total nitrogen was 76.89%when the total nitrogen direct removal rate was 83.97%,which was the least active nitrogen loading process in the 3 sewage treatment processes.(3)The nitrogen footprint of the three processes of BNR-MBR,MSBR and MBR was estimated.The results showed that the total nitrogen direct removal rate of the 3 sewage treatment processes was higher than the comprehensive removal rate of total nitrogen,which means that the 3 kinds of technology combination removal of nitrogen in sewage and the release of new active nitrogen to the environment.Meanwhile,the total nitrogen direct removal rate of the MSBR process is higher than that of the MBR process,but the total nitrogen comprehensive removal rate is lower than that of the MBR process.This is because in the MSBR process,the total nitrogen concentration of the influent is low,which is 50.3mg/L,and the nitrogen footprint of the influent is low,which makes the ratio of nitrogen footprint released into the environment and the ratio of the influent nitrogen footprint in the process of MSBR treatment.Therefore,when dealing with the wastewater with lower total nitrogen concentration,the total nitrogen removal rate will be more than that of the total nitrogen removal rate.(4)The nitrogen footprint of BNR-MBR+ agricultural utilization(B1),BNR-MBR+ landfill(B2),BNR-MBR+ incineration(B3),MSBR+ agricultural utilization(MS1),MSBR+ landfill(MS2),MSBR+ incineration(MS3),agricultural utilization,sewage disposal and sludge incineration technology system of sewage sludge treatment technology were estimated.Compared with the potential value of environmental impact factors released to the environment,the results show that the BNR-MBR wastewater treatment process will produce more greenhouse gas N2O in the process of treatment,thus the potential impact of the BNR-MBR combined process treatment system on global warming is larger,and a large amount of NH3 is produced in the process of landfill disposal.Therefore,the combined treatment system using this technology has great influence on the potential environment of acidification and nutrition.Through the construction of the nitrogen footprint model and the empirical study of the sewage sludge treatment system,this paper further perfects the scientific quantitative evaluation theory method system of the real nitrogen emission and the contribution degree of environmental pollution to the sewage sludge treatment system.On the other hand,it can also optimize the new technology of the actual sewage sludge treatment system in China.The optimization of process combination provides a new evaluation and management decision support tool. |
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