Industrial Symbiosis: A Mechanism to Guarantee the Implementation of Circular Economy Practices

There is a growing concern regarding the scarcity of natural resources. The levels of resource exploitation generated by the current system of production and consumption has led the European Commission to develop a set of guidelines that aim to reduce the pressure on natural resources. The set of guidelines proposed by the European Union is based on the transformation of the current linear economic system into a circular system in which resources and materials remain in the production system for longer. However, for this change to take effect, practical measures are required. This paper presents an industrial symbiosis approach as a practical application of a circular economy model. The aim of this paper is to develop a guide to successfully implement an industrial symbiosis network, demonstrating that industrial symbiosis can achieve the goals of a circular economy. To demonstrate this, an example of its implementation is provided in a region of Spain, which is responsible for producing approximately 95% of the total ceramics products in the nation. This study emphasises the set of barriers that need to be addressed in order to make new models a reality for business and consumers, society, and the environment

Evaluación del comportamiento energético de las estaciones depuradoras de aguas residuales: Una aproximación económica

Las Estaciones Depuradoras de Aguas Residuales (EDARs) son una pieza básica del conjunto de infraestructuras urbanas, ya que son indispensables para garantizar la salud pública y del medio ambiente. Actualmente, en España existen aproximadamente 3.000 EDARs que tratan 4.700 hm3 de aguas residuales, de los cuales la mayor parte, un 55,8% y un 33,5% son vertidos a cauces fluviales y al mar, respectivamente, mientras que un 10,4% es reutilizado en la agricultura y el riego de jardines, y el 0,3% restante es infiltrado al suelo para la regeneración de acuíferos y otros fines. Según el destino del agua residual, la normativa en materia de aguas residuales urbanas y reutilización requiere el cumplimiento de unos criterios de calidad determinados, que se consiguen gracias a la implementación de tecnologías de tratamiento que requieren un elevado consumo energético para su funcionamiento. A lo largo de los años, se ha observado que el consumo energético utilizado en el sector de la depuración se ha intensificado debido a que la población conectada al sistema de alcantarillado es cada vez mayor, y a la necesidad de cumplir con las exigencias ambientales establecidas por la normativa europea y estatal en esta materia. El control del consumo energético de las EDARs se ha convertido en un aspecto fundamental para los operadores de las instalaciones debido al impacto económico que tiene en los costes operacionales del proceso, los cuales pueden suponer entre un 30 y un 40% de los costes totales, dependiendo de la tecnología empleada en el proceso, el tamaño de la población servida, así como de la calidad del efluente exigida, entre otros muchos factores. Además, se prevé que el consumo energético, y por ende los costes asociados a éste, incrementen en los próximos años como consecuencia de la publicación de una legislación que contemple requerimientos de calidad más exigentes que los actuales. Ante esta situación, a lo largo de los últimos años se han implementado las instalaciones con tecnologías más eficientes y sistemas de control automáticos que permiten regular su consumo energético. Pese a ello, aún existe un elevado potencial de mejora por lo que se refiere a la optimización del consumo energético de las EDARs, tal y como se demuestra en el artículo que forma parte del presente compendio titulado “Efficiency assessment of wastewater treatment plants: A data envelopment analysis approach integrating technical, economic, and environmental issues”. En esta publicación se prueba que el coste energético, y, por ende, el consumo energético de las EDARs presenta un gran potencial de mejora por lo que a la eficiencia del proceso se refiere. Para llevar a cabo este estudio se utiliza una metodología que ha despertado gran interés en los últimos años tanto entre la comunidad científica en general como en el ámbito del tratamiento de las aguas residuales por su gran versatilidad. Se trata del Análisis Envolvente de Datos (DEA), una metodología basada en los modelos de optimización lineal que permite medir la eficiencia relativa de un conjunto de unidades de producción a través de un procedimiento no paramétrico. Con el fin de optimizar el proceso y reducir consumos energéticos innecesarios es importante identificar los distintos factores que afectan al consumo energético de las plantas y ver en qué medida influyen. Para ello, se propone el uso de técnicas estadísticas y econométricas que permiten analizar distintas variables o características de las instalaciones que pueden afectar al consumo energético. Detectar aquellas variables o parámetros estrechamente ligados al consumo energético de las EDARs permitirá a los gestores y operadores, ya sean públicos o privados, actuar sobre ellas y mejorar la eficiencia de las instalaciones. Con este propósito se desarrollan los artículos “The relevance of the design characteristics to the optimal operation of wastewater treatment plants: energy cost assessment” y “Modelling the energy costs of the wastewater treatment process: The influence of the aging factor”. El primero de ellos presenta las diferencias entre el caudal de diseño y el caudal real tratado por las instalaciones como un factor que puede afectar a los costes energéticos de las instalaciones, mientras que el segundo pretende evaluar y demostrar los efectos negativos que tiene el envejecimiento de las infraestructuras en el coste energético. Por lo que se refiere al dimensionamiento de las instalaciones son muchos los casos en los que se pueden observar grandes diferencias entre el caudal real que tratan las instalaciones y el de diseño, bien sea porque están sobredimensionadas ya que no se cumplieron las expectativas de crecimiento poblacional consideradas en el momento de construcción, o bien porque su capacidad de tratamiento se ve sobrepasada debido a que se tratan volúmenes de agua superiores a los de diseño. Sea cual sea el motivo del desajuste entre el caudal real y el de diseño, lo cierto es que los equipos que constituyen las instalaciones no están trabajando en el óptimo, siendo generalmente las instalaciones de pequeño tamaño las más afectadas ya que, a diferencia de las grandes, no suelen estar equipadas con sistemas de control que permiten optimizar el dimensionamiento. En cuanto al envejecimiento de las instalaciones, estamos ante una nueva situación que preocupa tanto a gestores públicos como privados, ya que se trata de infraestructuras que hay que mantener y renovar periódicamente para garantizar su correcto funcionamiento. Desde que entrara en vigor la Directiva 91/271/CEE el equipamiento relacionado con el sistema de saneamiento ha crecido notablemente, y son muchas las instalaciones que ya han superado su vida útil o se encuentran a mitad de este periodo, por lo que sin la existencia de estrategias de mantenimiento preventivo y un plan de reposición bien definido, el proceso y la calidad del agua residual se pueden ver afectadas poniendo en riesgo la salud de las personas y del medio ambiente. La relación entre los factores citados anteriormente, es decir, el desajuste entre el caudal real y el de diseño y el envejecimiento de las instalaciones, con el coste energético se materializa mediante el desarrollo de distintas funciones de coste que permiten modelizar el coste energético de las EDARs teniendo en cuenta estas variables, además de otro tipo de variables técnicas como el tamaño o la tecnología de tratamiento y la calidad del agua tratada. Se considera que este tipo de herramienta podría aportar información de gran utilidad a los gestores de las instalaciones, convirtiéndose en una herramienta útil para la toma de decisiones.Wastewater Treatment Plants (WWTPs) are a basic piece of urban infrastructure as they are essential to guarantee public and environmental health. Currently, in Spain, there are approximately 3,000 WWTPs that treat 4,700 hm3 of wastewater. Approximately, 55.8% and 33.5% of the wastewater treated is discharged into river channels and the sea, respectively, while 10.4 % is reused in agriculture and garden watering, and the remaining 0.3% is infiltrated to the ground for aquifer regeneration and other purposes. Depending on the final disposal of wastewater, different quality requirements established on urban wastewater and reuse regulations must be complied, and it can be achieved thanks to the implementation of treatment technologies that require high energy consumption for its operation. Over the years, it has been observed that the energy consumption used in the wastewater treatment sector has intensified because of the increase in the number of people connected to the sewerage system, and the need to meet the environmental requirements established by European and state regulations in this matter. The control of the energy consumption of the WWTPs has become a relevant aspect for the operators of the facilities due to the economic impact that it has on the operational costs of the process, which can represent between 30 and 40% of the total costs. Variations in energy costs depend on the technology used in the process, the size of the population served, as well as the quality of the effluent required, among many other factors. In addition, it is expected that energy consumption, and therefore the costs associated with it, will increase in the near future as a result of the publication of a new legislation that contemplates more demanding quality requirements than the current ones. Given this situation, over the last few years, facilities with more efficient technologies and automatic control systems have been implemented to regulate the energy consumption of the facilities. Despite this, there is still a high potential for improvement in terms of optimizing the energy consumption of the facilities, as demonstrated in the paper that is part of this compendium entitled Efficiency assessment of wastewater treatment plants: A data envelopment analysis approach integrating technical, economic, and environmental issues. In this study, it is proved that the energy cost, and, therefore, the energy consumption of the WWTPs could be reduced giving, as a result, a more efficient process. To carry out this study, a methodology that has aroused great interest because of its great versatility in both the scientific community and in the field of wastewater treatment has been used. This is the Data Envelopment Analysis (DEA), a methodology based on linear optimization models that allow measuring the relative efficiency of a set of production units through a non-parametric procedure. In order to optimize the process and reduce unnecessary energy consumption, it is important to identify those factors that affect the energy consumption of the plants and analyze their influence. For this purpose, the use of statistical and econometric techniques is proposed, since they allow us to assess how different variables or characteristics of the facilities may affect energy consumption. Detecting those variables or parameters closely linked to the energy consumption of wastewater treatment plants will allow managers and operators, whether public or private, to act on them and improve the efficiency of the facilities. In the light of this, the papers named 'The relevance of the design characteristics to the optimal operation of wastewater treatment plants: energy cost assessment' and 'Modeling the energy costs of the wastewater treatment process: The influence of the aging factor' are developed. The first of the publications mentioned above presents the differences between the design inflow and the real flow treated by the facilities as a factor that may affect the energy costs of the facilities, while the second aims to evaluate and demonstrate the negative effects that the aging of the infrastructure has on the energy cost. With regard to the size of the facilities, there are many examples in which large differences between the real flow of the facilities and the design can be observed, either because they are oversized since the expectations of population growth considered at the time of construction were not met, or because its treatment capacity is exceeded due to the fact that the wastewater volumes treated are higher than the design flow. Whatever the reason for the mismatch between the actual and the design flow, the truth is that the equipment that constitutes the facilities is not working at the optimum, being small-sized facilities the most affected since, unlike the large, they are not usually equipped with control systems that optimize the sizing. Regarding the aging of the facilities, we are facing a new situation that concerns both public and private managers, since these are infrastructures that must be maintained and renewed periodically to ensure their proper functioning. Since Directive 91/271 / EEC entered into force, the equipment related to the sewage system has grown remarkably, and there are many facilities that have already exceeded their useful life or are in the middle of this period, so without the existence of preventive maintenance strategies and a well-defined replacement plans, the process and the quality of wastewater can be affected, putting the health of people and the environment at risk. The relationship between the factors mentioned previously, that is, the mismatch between the real and the design flow and the aging of the facilities, with the energy cost, is materialized through the development of different cost functions that enables the managers and operators to mode the energy cost of the WWTPs taking into account these variables, in addition to other technical variables such as the size of the facilities, the technology used and the quality of the wastewater. It is considered that this kind of tools could provide useful information to the managers, becoming a useful tool for the decision making process

A Tariff Model for Reclaimed Water in Industrial Sectors: An Opportunity from the Circular Economy

The growth of the world’s population is associated with an increase in demand for water. The consequences of this increase are twofold: On the one hand, it endangers the water balance of the ecosystem, and on the other hand, it considerably increases the volume of wastewater generated. In this sense, wastewater treatment plants (WWTPs) play a fundamental role since their objective is to guarantee the quality of the effluents discharged into the environment. Moreover, current treatment systems allow for the subsequent use of the effluent. Thus, the wastewater treatment sector can be seen as an unconventional source of water, acquiring a special importance in the framework of the circular economy. In this context, water reclamation and reuse are identified as key components of water resource management. However, the economic aspects, in terms of tariff design and cost recovery, represent a major barrier to incentivizing its use. In this paper, the authors analyze these aspects and propose a tariff that combines the cost recovery, an incentive to use reclaimed water and other relevant aspects that guarantee the success of water reuse projects. With this objective, three industrial sectors are evaluated. For the first sector, the user industries would achieve a saving of approximately 10% by changing the consumption of conventional water to reclaimed water; in the second sector, they would achieve a saving of 18% and in the third sector a saving of approximately 16%. In addition to guaranteeing sustainability in the consumption of reclaimed water in industry, the viability of the supplying company is ensured. This research offers valuable results that will be useful for establishing future strategies aimed at encouraging the use of reclaimed water in industrial environments

Industrial Symbiosis: A Mechanism to Guarantee the Implementation of Circular Economy Practices

There is a growing concern regarding the scarcity of natural resources. The levels of resource exploitation generated by the current system of production and consumption has led the European Commission to develop a set of guidelines that aim to reduce the pressure on natural resources. The set of guidelines proposed by the European Union is based on the transformation of the current linear economic system into a circular system in which resources and materials remain in the production system for longer. However, for this change to take effect, practical measures are required. This paper presents an industrial symbiosis approach as a practical application of a circular economy model. The aim of this paper is to develop a guide to successfully implement an industrial symbiosis network, demonstrating that industrial symbiosis can achieve the goals of a circular economy. To demonstrate this, an example of its implementation is provided in a region of Spain, which is responsible for producing approximately 95% of the total ceramics products in the nation. This study emphasises the set of barriers that need to be addressed in order to make new models a reality for business and consumers, society, and the environment

The Potential of Digitalization to Promote a Circular Economy in the Water Sector

The current amount of data coming from all kinds of devices together with the incessant increase in computing capacity is revolutionizing almost all existing sectors, and the water sector is no exception. The monitoring of urban water cycle infrastructures makes it possible to generate a large amount of data, this information, previously processed, helps to increase the efficiency of the processes carried out in these infrastructures, from catchment to purification and subsequent discharge. This information, in addition to improving internal aspects such as the operation and maintenance of the infrastructures, allows them to be linked to multiple other variables in other sectors, making new technological approaches and more effective management strategies possible. A practical example is wastewater treatment plants. From the perspective of the circular economy, these infrastructures are capable of producing a large amount of resources, which, if properly managed, can reduce the pressure on conventional resources. In this sense, digitization allows the integration of the different market players, thus optimizing the supply and demand of these resources and ultimately advancing the practical application of the circular economy. This paper reviews the potential of digitalization in the urban water sector and proposes numerous practical examples to accelerate the transition towards economic, social, and environmental sustainability

AI Applied to the Circular Economy: An Approach in the Wastewater Sector

Water is one of the most basic and essential resources for life and is also a strategic component for the development of the economies of the different countries of the planet. The water sector in the context of ecological transition and the circular economy has enormous economic potential. However, the water resources present in a territory are, in many cases, very limited, and their availability is increasingly restricted. In this respect, current technologies make it possible to generate a whole range of renewable resources. In the case of wastewater treatment plants, in addition to obtaining clean water in sufficient quantity and quality, it is possible to take advantage of multiple other resources generated in the purification processes, such as fertilizers, biogas, bioplastics, and glass, and even recover adsorbents such as enzymes and proteins from wastewater. These resources represent a valuable social, environmental, and economic contribution. The scarcity of some of these resources causes continuous increases in market prices, generating economic tensions between producers and potential users. This work proposes to guide the potential of artificial intelligence (AI)-based methodologies in aspects related to the supply and demand of the resources generated in these infrastructures. Specifically, the use of machine learning (ML) allows for projecting economic scenarios based on multiple variables, such as the quality and quantity of the treated flows, the resources generated in the infrastructures, the current demands, and the prices of substitute goods. This aspect represents a substantial advance in terms of the circular economy since, beyond the technical aspects related to the processes, it ensures a sustainable balance between potential producers and end users. In conclusion, it brings sustainability to the urban water-cycle sector, ensuring the viability of the resources generated

Circular economy and efficiency to ensure the sustainability in the wastewater treatment plants

Wastewater treatment plants (WWTPs) represent a great opportunity within the framework of the circular economy. Not only are WWTPs an alternative source of water, but they can provide other valuable resources for other sectors such as water and energy. For instance, the nutrients contained in wastewater are of great importance for agriculture, since they can be used as fertilizers. In this sense, evaluating the efficiency of wastewater treatment processes makes it possible to identify those aspects that improve the performance of these infrastructures, thus ensuring their long-term sustainability. Most of the previous studies evaluate the efficiency based on the resources used and the total pollutant removal, this aspect does not consider that the quantity of pollutants that WWTPs are obliged to remove depend on the characteristics of the discharge location. To address this, an advanced efficiency model is applied to differentiate between the amount of pollutants that the Directive 91/271/EEC oblige to remove and the extra quantity of pollutants that WWTPs remove beyond the legal requirements. The results show that most of the facilities are able to remove a higher quantity of pollutants and, consequently, generate more resources for the society. The methodology and results of this study are of great interest to WWTP managers and administrations, encouraging the implementation of design-based solutions to maximize by-product collection in the wastewater treatment sector and improve the efficiency of these facilities

The Potential of Digitalization to Promote a Circular Economy in the Water Sector

The current amount of data coming from all kinds of devices together with the incessant increase in computing capacity is revolutionizing almost all existing sectors, and the water sector is no exception. The monitoring of urban water cycle infrastructures makes it possible to generate a large amount of data, this information, previously processed, helps to increase the efficiency of the processes carried out in these infrastructures, from catchment to purification and subsequent discharge. This information, in addition to improving internal aspects such as the operation and maintenance of the infrastructures, allows them to be linked to multiple other variables in other sectors, making new technological approaches and more effective management strategies possible. A practical example is wastewater treatment plants. From the perspective of the circular economy, these infrastructures are capable of producing a large amount of resources, which, if properly managed, can reduce the pressure on conventional resources. In this sense, digitization allows the integration of the different market players, thus optimizing the supply and demand of these resources and ultimately advancing the practical application of the circular economy. This paper reviews the potential of digitalization in the urban water sector and proposes numerous practical examples to accelerate the transition towards economic, social, and environmental sustainability

The Quantification of Non-Action Costs as an Incentive to Address Water Pollution Problems

Diffuse pollution is one type of pollution generated by agricultural, livestock, and urban runoff that is responsible for surface and groundwater pollution. As a result, the exposed population develops different diseases that affect their short, medium, and long-term quality of life. Researchers need to be able to assess the loss of quality of life in monetary terms to include this social impact in decision-making processes. Specifically, if no measure is implemented to correct the situation, these costs can be considered as the non-action costs of the social impact of water pollution. This study assesses the importance of measuring healthcare costs as a proxy for non-action costs for the economic assessment of water pollution consequences. Thanks to this analysis, it is possible to identify the health costs produced by the current environmental situation, making it possible to obtain an economic baseline scenario prior to the implementation of any project or measure. This approach is a novelty in the literature since, to date, healthcare costs have not been related to non-action costs. Including these costs in economic feasibility studies allow us to assess in detail both the social impact of pollution and the social benefits of develop water-quality improvement projects