Measuring the efficiency of wastewater services through Data Envelopment Analysis

Carbon emission efficiency evaluation of wastewater treatment plants: evidence from China

A scientific evaluation of the carbon emission efficiency is crucial for ensuring the sustainable development of wastewater treatment plants (WWTPs). In this paper, we applied a non-radial data envelopment analysis (DEA) model to calculate the carbon emission efficiency of 225 WWTPs located in China. The results showed that the average carbon emission efficiency of China's WWTPs was 0.59, indicating that the efficiencies of most samples still require improvement. The carbon emission efficiency of WWTPs from 2015 to 2017 decreased because of the decrease in technology efficiency. Among the influencing factors, different treating scales had positive impact on carbon emission efficiency improvement. WWTPs with anaerobic oxic process and the first-class A standard were likely to have higher carbon emission efficiency in the 225 WWTPs. By incorporating direct and indirect carbon emissions into WWTP efficiency evaluation, this study helped decision-makers and related water authorities to better understand the contribution of WWTPs to the aquatic and atmospheric environments.

Eco-efficiency assessment of municipal solid waste services: Influence of exogenous variables

Improving the eco-efficiency of municipalities in the provision of municipal solid waste (MSW) services is fundamental in the context of a circular economy. This study evaluates the eco-efficiency of a sample of Spanish municipalities, integrating the total cost as input, recyclable waste as desirable output, and unsorted waste as undesirable output. Following a pioneering approach, the weighted Russell directional distance model (a non-radial data envelopment analysis model) was employed, which allowed us to obtain a global inefficiency score and individual inefficiency scores for each variable integrated in the model. In the second stage of analysis, the potential factors affecting the previously computed inefficiency scores were investigated. The results indicated that one third of the municipalities evaluated were eco-efficient in the provision of MSW services with the total cost being the variable in which the municipalities exhibited the best performance. Moreover, the size of the municipalities, population served, population density, tourism, and availability of containers for separative collection of paper, glass, and plastic significantly affect the eco-efficiency of the municipalities. The findings of this study provide detailed information to support decision-making for the policy makers to improve the eco-efficiency of the municipalities in managing MSW.

The Small-Scale Treatment Plant Industry: Institutional Features of Companies, Problems and Functionality of Small-Scale Treatment Systems

The purposes of this study is to show the corporate characteristics of companies which have been operating in the fields of small-scale treatment plants' (SSTPs') design, construction, and installation processes, and to exhibit findings/perceptions of company employees on issues such as the initial investment and operating costs, common production and operating problems, the functionality of the small-scale treatment systems and the added value they provide to their customers' facilities. As a result of this study, it was determined that when the personnel participating in the survey were directly trained and recruited by the companies, which is generally the case, their training includes more practical methods and their experiences are shaped by the master-apprentice relationships in the sector. Regarding water treatment in SSTPs, the companies surveyed opted for traditional methods such as reverse osmosis and coagulation-flocculation, and preferred to use traditional biological treatment units-continuous flow or sequencing batch reactors (SBRs)- in wastewater treatment. In favor of businesses in need of water and wastewater management systems, the surveyed company employees have considered SSTPs as a successful, competitive advantage in the industry by maintaining low initial investment and operational costs while fulfilling the relevant environmental legal obligations. After examining the data regarding the opinions of company employees about SSTPs, it was found that there is a very significant relationship between the problems experienced during the installation/construction process and the problems during their operation.

Evaluation of the Efficiency of Basic Sanitation Integrated Management in Brazilian Municipalities

This study aims to evaluate the level of technical efficiency of companies that perform the integrated management of basic sanitation in Brazilian municipalities. A Multiple Data Envelopment Analysis (M-DEA) model was applied to estimate the performance of water supply and sewage services in 1628 municipalities covering more than 56% of the Brazilian population, identifying the factors that most influence the efficiency of the sector in the years 2008 and 2016. The M-DEA methodology is an extension of Data Envelopment Analysis (DEA) with multiple DEA executions considering all combinations of inputs and outputs to calculate efficiency scores. The methodology reduces possible biases in the selection of resources and products of the model, ability to support decision-making in favor of improvements in the sector's efficiency based on national regulatory framework. The analyses show that the companies analyzed can increase their operating results and attendance coverage by more than 60%, given the current levels of infrastructure, human and financial resources in the sector. Based on the simulation of potential efficiency gains in Brazilian basic sanitation companies, the estimates show that the coverage of the population with access to sanitary sewage would go from the current 59.9% to 76.5%. The evidence found provides indications to subsidize sanitation management in the country at the micro-analytical level, enabling a better competitive position in the sector for the integrated management of basic sanitation and its universalization in Brazil.

Associated Effects and Efficiency Evaluation between Wastewater Pollution and Water Disease Based on the Dynamic Two-Stage DEA Model

The lack of basic water supply and treatment facilities during China's urbanization and industrialization process has resulted in a large amount of wastewater pollution, with the most serious water diseases being water-borne endemic fluorosis and arsenic poisoning, which have affected more than 20 million people. This research therefore uses the improved modified undesirable dynamic network model to analyze data of 31 provincial administrative regions to focus on the associated effects and efficiency evaluation between wastewater pollution and water disease in China. The results show that the efficiency of water pollution disease in all four regions of the country and the total efficiency in the east, west, and central regions all show a decreasing trend, while the efficiency scores and rankings of all provinces and cities within the region fluctuate greatly. The eastern region with the most developed economy has the best overall performance, with higher efficiency in water consumption and water disease control. However, the efficiency of wastewater treatment in northeast China is stable and better. Given the high level of the nation's economic development and the results of efficiency in water pollution and water diseases, improving the efficiency and quality of wastewater treatment in China is regarded as an important factor for achieving the strategic goal of green growth.

Cost of Urban Wastewater Treatment and Ecotaxes: Evidence from Municipalities in Southern Europe

The principle of cost recovery established by the Water Framework Directive underlines the need for tax rates, which can raise enough revenue to finance the cost of treatments applied to wastewater. The objective of this research is to gain an understanding the different types of charges related to urban wastewater treatment that can be levied by the authorities responsible for this service. This paper also aims to determine whether these taxes contribute to guaranteeing the economic feasibility of the wastewater treatment plants. The proposed methodological approach is applied to 18 municipalities of a province in southern Europe in 2017. The results confirm that in most of these cases, the taxes levied do not guarantee adequate tax revenues to cover the running, maintenance and investment costs of municipal wastewater treatment plants. This situation leads to a lack of financial self-sufficiency in the wastewater management service, meaning that the imbalance between income and expenditure has to be covered by government subsidies. The results of this study will help guide authorities around the world that are in charge of managing urban wastewater treatment services.

Efficiency of wastewater treatment facilities: The influence of scale economies

The water cycle, from catchment to discharge, is a sector that involves an important investment and operation and maintenance costs. In particular, sewage treatment is a challenge for governments because they are having to consider economic, environmental, and social aspects. Within the European Union, implementation of Directive 91/271/EEC is responsible for the location of wastewater treatment facilities in the territory, due to the requirement that all urban areas must have this infrastructure to reduce the environmental impact of treated water in water bodies. Different sizes of municipalities affect the design of each wastewater treatment plant (WWTP) and cause variations in the operation process. The presence of scale economies in this sector has a significant influence on the efficiency of the wastewater treatment process and has a direct impact on the operational costs. Based on the pursuit of economic and environmental efficiency, this analysis extends the scope of the current literature because it recommends a specific, population equivalent (p.e.) range for which it would be suitable to achieve efficiency in wastewater treatment facilities-shedding light on the open debate about scale economies in WWTPs.

Measuring the eco-efficiency of wastewater treatment plants under data uncertainty

Eco-efficiency assessment is a useful tool for improving the sustainability of wastewater treatment plants (WWTPs). However, it is a complex task that requires the integration of several performance indicators into a single index. Data envelopment analysis (DEA) is established as a highly effective methodology for achieving this as it permits the integration of the service value, resource consumption and environmental impact variables as the desirable outputs, inputs and undesirable outputs, respectively. However, traditional DEA models omit uncertainties in the data that are likely to result in biased conclusions. This study pioneers the assessment of the eco-efficiency of WWTPs while accounting for the data uncertainty and integrating the greenhouse gas emissions as an undesirable output. The DEA-tolerance model was applied to compute the eco-efficiency scores for 729 scenarios for each facility tested for identifying the best- and worst-case scenarios. The WWTPs were also ranked based on their eco-efficiency scores. The results demonstrated the importance of integrating data uncertainty in eco-efficiency assessments; the performances of the WWTPs change notably based on the evaluated set of scenarios. The proposed methodological approach provides a reliable and robust framework for supporting decision-making processes.

Efficiency assessment of wastewater treatment plants: A data envelopment analysis approach integrating technical, economic, and environmental issues

The assessment of the efficiency of wastewater treatment plants (WWTPs) is essential to compare their performance and consequently to identify the best operational practices that can contribute to the reduction of operational costs. Previous studies have evaluated the efficiency of WWTPs using conventional data envelopment analysis (DEA) models. Most of these studies have considered the operational costs of the WWTPs as inputs, while the pollutants removed from wastewater are treated as outputs. However, they have ignored the fact that each pollutant removed by a WWTP involves a different environmental impact. To overcome this limitation, this paper evaluates for the first time the efficiency of a sample of WWTPs by applying the weighted slacks-based measure model. It is a non-radial DEA model which allows assigning weights to the inputs and outputs according their importance. Thus, the assessment carried out integrates environmental issues with the traditional "techno-economic" efficiency assessment of WWTPs. Moreover, the potential economic savings for each cost item have been quantified at a plant level. It is illustrated that the WWTPs analyzed have significant room to save staff and energy costs. Several managerial implications to help WWTPs' operators make informed decisions were drawn from the methodology and empirical application carried out.