Study on the Choice of Wastewater Treatment Process Based on the Emergy Theory

With the increase in industrialization and urbanization, water pollution has become increasingly serious, and wastewater treatment has become a common step in preventing this. For a greater understanding of the sustainability of different wastewater treatment systems, two processes, Anaerobic Baffled Reactor + Anaerobic-Anoxic-Oxic and Anaerobic Baffled Reactor + Cyclic Activated Sludge System, were selected, and their sustainability was evaluated based on three indicators, namely emergy yield ratio, environmental load rate, and emergy sustainability development index, according to emergy theory. The results show that the emergy yield ratio and environmental load rate of the ABR + CASS process were lower than those of the ABR + A2/O process, and the emergy sustainability development index of the ABR + CASS process was higher than that of the ABR + A2/O process, showing better sustainability. The research methods and findings of this study play an important role for decision makers in selecting sustainable wastewater treatment processes.

Integrated Energy System Planning Based on Life Cycle and Emergy Theory

Integrated energy system (IES) is of great significance in the construction of the modern energy system. Reasonable planning is one of the important means to improve the economy of the IES and promote the consumption of renewable energy. However, the complex coupling characteristics between energy sources make it difficult to quantify the production efficiency of multi-energy heterogeneous resources uniformly in the economic benefit model during the planning cycle. Quantifying the production efficiency of the IES for planning is currently an urgent problem to be solved. This study proposes a planning method for the IES based on the life cycle and emergy theory. First, emergy theory is applied to quantify the production efficiency of the IES. A complete economic benefit model is established based on life cycle theory. Second, a bi-level planning model of the IES is established. The upper-level model aims at minimizing the whole life cycle cost of the IES to plan the capacity and location of the coupling equipment. The lower-level model aims at maximizing the emergy yield ratio of the IES to provide the operating data for the upper level. Finally, comparing experimental evaluations with traditional planning schemes considering annual average cost and energy quality coefficient, the method in this study reduces planning costs by 23.16% and increases the consumption rate of renewable energy by 4.26%. It can be seen that the planning method proposed in this study improves the planning economy and the level of renewable energy consumption of the IES.

Sustainability of Regional Agroecological Economic System Based on Emergy Theory: A Case Study of Anhui Province, China

The agroecological economic system is the basic system on which human beings depend for survival. In order to better evaluate the operation status of a regional agroecological economic system and deepen the cognition of the input and output of the regional agroecological economic system from the angle of emergy, the evaluation method of sustainable development of the regional agroecological economic system with comprehensive consideration of resources, economy, and environment was proposed by constructing a unified dimensional measurement model. This paper analyzed and evaluated the data of the agroecological economic system in Anhui Province from 2010 to 2019. The results showed that the agroecological economic system in Anhui Province bore less environmental pressure and gradually decreased, and had a good system efficiency and economic benefits. The average emergy sustainability index (ESI) was 3.12, indicating that the agroecological economic system in Anhui Province had certain vitality of sustainable development. Based on this, the paper puts forward some suggestions on sustainable and high-quality agricultural development in Anhui Province, which provides theoretical and methodical support for sustainable development of a regional agricultural economy.

Quantitative Analysis of Eco-Economic Benefit of Urban Reclaimed Water Greening Based on Emergy Theory

With the faster urbanization and the higher living environment requirements of people, the urban green area is getting increasingly attention. But green irrigation consumes huge tap water, causes the waste of high-quality water resources. The reclaimed water meets the standard of green irrigation and the source is sufficient, it is a good alternative water source for urban greening. The eco-economic benefit of using reclaimed water as greening water was evaluated in this paper. The composition of benefit was analyzed and the difference in benefit brought by using reclaimed water greening instead of tap water was quantified based on emergy theory. Taking Zhengzhou in 2018 for example, the results showed that the eco-economic benefit of reclaimed water greening was remarkable. The total eco-economic benefit was $4.05 billion, which was three times of that of tap water. Among the benefits, economic benefit accounted for the largest proportion, reaching 69.22%. After deducting the cost, the net eco-economic benefit of reclaimed water greening was $2.00 billion, while tap water was negative. Therefore, using reclaimed water to irrigate urban green area can save a lot of high-quality water and bring a lot of economic, social and ecological environmental benefits. The quantitative results of this paper can provide reference for the promotion of reclaimed water greening and the allocation decision of reclaimed water in water shortage areas. And it is helpful to improve the utilization efficiency of water resources and alleviate the shortage of urban water resources.

Flood risk assessment in Ya'an, Sichuan, China based on the emergy theory

The emergy theory provides a new approach for flood risk assessment from an ecological perspective. By employing the emergy method, we used five indicators (rainfall runoff, medical workers and students per 10,000 people, social fixed assets investment, unit land GDP, and land-use types) from three dimensions (natural environment, population, and social economy) and the GIS technique to assess the potential impact and risk of a flood disaster on different regions in Ya'an City. Our findings revealed regional differences in the distribution of flood risks in Ya'an City: Lushan County and Yucheng District face the highest risks, followed by Tianquan County and Mingshan District, and Shimian County has the lowest risk. The index method was employed to analyze the regional differences. By training a back-propagation neural network with data of flood disasters in the study area, we produced a flood risk distribution map. We found that Mingshan District, Lushan County and Yucheng District have higher risks than other regions. The results largely agree with what we obtained using the emergy method. Our study shows that flood risk assessment based on the emergy theory can provide a scientific basis for flood control and disaster relief initiatives.

A Case Study of Flood Risk Evaluation Based on Emergy Theory and Cloud Model in Anyang Region, China

With the progression of climate change, the intensity and frequency of extreme rainfall have increased in many parts of the world, while the continuous acceleration of urbanization has made cities more vulnerable to floods. In order to effectively estimate and assess the risks brought by flood disasters, this paper proposes a regional flood disaster risk assessment model combining emergy theory and the cloud model. The emergy theory can measure many kinds of hazardous factor and convert them into unified solar emergy (sej) for quantification. The cloud model can transform the uncertainty in flood risk assessment into certainty in an appropriate way, making the urban flood risk assessment more accurate and effective. In this study, the flood risk assessment model combines the advantages of the two research methods to establish a natural and social dual flood risk assessment system. Based on this, the risk assessment system of the flood hazard cloud model is established. This model was used in a flood disaster risk assessment, and the risk level was divided into five levels: very low risk, low risk, medium risk, high risk, and very high risk. Flood hazard risk results were obtained by using the entropy weight method and fuzzy transformation method. As an example for the application of this model, this paper focuses on the Anyang region which has a typical continental monsoon climate. The results show that the Anyang region has a serious flood disaster threat. Within this region, Linzhou County and Anyang County have very high levels of risk for flood disaster, while Hua County, Neihuang County, Wenfeng District and Beiguan District have high levels of risk for flood disaster. These areas are the core urban areas and the economic center of local administrative regions, with 70% of the industrial clusters being situated in these regions. Only with the coordinated development of regional flood control planning, economy, and population, and reductions in the uncertainty of existing flood control and drainage facilities can the sustainable, healthy and stable development of the region be maintained.