Application of Emergy Analysis to the Sustainability Evaluation of Municipal Wastewater Treatment Plants

Abstract

Abstract:Municipal wastewater treatment plants consume much energy and manpower, are expensive to run, and generate sludge and treated wastewater whilst removing pollutants through specific treatment regimes. The sustainable development of the wastewater treatment industry is therefore challenging, and a comprehensive evaluation method is needed for assessing the sustainability of different wastewater treatment processes, for identifying the improvement potential of treatment plants, and for directing policymakers, management measures and development strategies. This study established improved evaluation indicators based on Emergy Analysis that place total wastewater, resources, energy, economic input and emission of pollutants on the same scale compared to the traditional indicators. The sustainability of four wastewater treatment plants and their associated Anaerobic-Anoxic-Oxic (A2O), Constant Waterlevel Sequencing Batch Reactor (CWSBR), Cyclic Activated Sludge Technology (CAST) and Biological Aerated Filter (BAF) treatment processes were assessed in a city in northeast China. Results show that the CWSBR process was the most sustainable wastewater treatment process according to its largest calculated value of Improved Emergy Sustainable Index (2.53 × 10 0 ), followed by BAF (1.60 × 10 0 ), A2O (9.78 × 10 −1 ) and CAST (5.77 × 10 −1 ). Emergy Analysis provided improved indicators that are suitable for comparing different wastewater treatment processes.

Development of the Emergy-Gis Method of Selecting Areas for Sponge-Like Urban Reconstruction

“…Therefore, this potential overestimation of runoff pollution with differences in orders of magnitude can potentially change the integration of the three indices, which can further affect the selection of suitable areas. Due to lack of the proper transformity of COD, a potential solution can be direct calculation of the emergy of runoff pollution in terms of the emergy associated with dilution of COD pollutant to its environmental safety concentration, using Equations 2 and 3 (Li et al, 2013;Shao et al, 2017 where MCOD is the quantity of COD in grams, CCOD is the environmental safety concentration of COD in g/m 3 , Mrunoff pollution is the total quantity of the runoff pollution in grams, G is the Gibbs free energy (4.82 J/g), UEVwater is the transformity of surface water (4.48 × 10 4 sej/J). According to China's environmental quality standard for surface water (GB 3838-2002), the environmental safety concentration of COD is 15 mg/L (EPB, 2002).…”

Sustainability Analysis of a Municipal Wastewater Treatment Plant through Emergy Evaluation

“…In recent years, many studies aimed to develop and use environmental management instruments to conceptualize and quantify human activities' direct and indirect effects on the environment, to enable decision-makers to track and measure progress towards sustainability goals and outcomes. These environmental management instruments include the Ecological Footprint [6,7], Cost-Benefit Analysis [8], Energy Flow Analysis [9], Exergy Analysis [8,10], Life Cycle Assessment (LCA) [11][12][13][14], Integrated assessments [15,16], and Emergy Analysis [1,8,[17][18][19][20]. However, a method that is suitable from the sustainable development perspective has to consider all interactions between environmental, social, and economic impacts of wastewater treatment systems.…”

“…In terms of sustainability, the relationship between wastewater treatment systems and the environment has become a topic of interest for researchers. Shao et al [18] created improved evaluation indicators based on emergy theory, to compare four different wastewater treatment processes from a sustainability perspective. The study provides guidance for policymakers, on choosing a wastewater treatment technology for a new plant or upgrading for existing plants.…”

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

“…The emergy approach has also compared two management schemes for biosolids generated from wastewater treatment plants [32]. Improved evaluation indicators based on emergy analysis were created to compare the sustainability of different wastewater treatment processes [33] and evaluate the wastewater treatment system of a sugar mill in Kenya [34].…”