A Sustainability Analysis Of The Sewage Slugde Treatment System Based On Emergy

With the continuous development of social economy, the output of municipal sewage sludge is becoming larger and larger.Although there are many kinds of sewage sludge treatment and disposal methods, the different methods have their ownissues related to the economy and resources and environment. These issues have influenced the normal operation of those sewage sludge treatment and disposal systems. Therefore, evaluating correctly and comprehensively the performance of different sewage sludge treatment and disposal systems is closely related to the choice of disposal methods. The traditional performance evaluation methods, such as economic analysis, energy analysis, due to neglect the environment contribution to the system and the differences of the different types of material and energy, cannot effectively serve the decision-making. However, emergy analysis has overcome these defects. Through analyzing the sewage sludge treatment and disposal systems, this paper established a serious of emergy indictors, and evaluate the system’s performances from the economic, environmental and sustainability aspects,and the proposed method and indicator system were used to research the comprehensive performances of the earthworm composting sludge treatment system of Lvshan company. The results show that the process can reduce the sludge to 70%; its treatment cycle is only one third to one fourth of that the microbial compost process; it makes the content of available nitrogen, phosphorus, potassium reach 523mg/kg,255.9 mg/kg,1600 mg/kg, respectively; heavy metal content is far below the limit values from "the quality of landscape mud" (CJ248-2007). Therein, the reduction of Pb, Cu and Hg excesses 50%. It also realizes the resource utilization of sewage sludge through providing fertilizer for landscape. The emergy analysis shows that its net emergy yield ratio(EYR) reaches 1.15, environmental loadingratio(ELR) is only 0.118, and environment sustainable index (ESI) is as high as9.75. Compared with other sludge treatment and disposal systems, the system has moderate economic benefit, low environmental pressure, and high sustainability. Finally, this paper put forward the corresponding countermeasures and suggestions for further improving the comprehensive performance of this company.