The benefits of circular economy strategies in urban water facilities.

Circular economy has become a very popular item in the last decades in many fields. Particularly, in the water and wastewater sector, since a lot of pressure has been put on water resources. Although the main target of the application of circular economy in this sector has been waste management, the current research intends to extend its application to other aspects. In this sense, it is highlighted the role that asset management could play in wastewater treatments plants extending the useful life of the equipment and the facilities, and how it could contribute to the circular economy, measuring the impact in economic and environmental terms. Making use of the Analytical Hierarchy Process (AHP) it can be observed that maintenance tasks are one of the most important factors to avoid equipment deterioration. This research offers valuable results that will be useful to assess the condition of the equipment helping the decision-makers to optimize the maintenance tasks and plan replacement strategies that will lead to accomplishing the principles of circular economy, increasing the service life span of the equipment, and reducing the repairing costs, and minimizing the environmental impact associated to the replacement of the equipment.

The relevance of the design characteristics to the optimal operation of wastewater treatment plants: Energy cost assessment.

Operational parameters of the wastewater treatment process do not always fit the design ones for several reasons, such as the seasonality or an inaccurate estimation of the population connected. This fact has an effect on the performance of the Wastewater Treatment Plants (WWTPs) and their energy costs. The aim of this paper is to develop a cost function for the energy cost that takes into account the mismatching between the design and the operational inflow. For this purpose, a performance index is constructed in order to represent how far the operational inflow is from the design one, and will be included in the cost model. Moreover, three cost functions, depending on the size of the plants are developed in order to provide the managers of the WWTPs with valuable information that could be used to optimise the wastewater treatment process.

Modelling the energy costs of the wastewater treatment process: The influence of the aging factor.

Wastewater treatment plants (WWTPs) are aging and its effects on the process are more evident as time goes by. Due to the deterioration of the facilities, the efficiency of the treatment process decreases gradually. Within this framework, this paper proves the increase in the energy consumption of the WWTPs with time, and finds differences among facilities size. Accordingly, the paper aims to develop a dynamic energy cost function capable of predicting the energy cost of the process in the future. The time variable is used to introduce the aging effects on the energy cost estimation in order to increase the accuracy of the estimation. For this purpose, the evolution of energy costs will be assessed and modelled for a group of WWTPs using the methodology of cost functions. The results will be useful for the managers of the facilities in the decision making process.