MCDA-DEA approach to construct a composite indicator for effluents from WWTPs considering the influence of PPCPs.

Considering current water situation, reuse is an effective solution to meet water demand and reduce pressure on conventional water sources. However, pharmaceutical and personal care products (PPCPs) in effluents from wastewater treatment plants (WWTPs) decrease their quality and suitability. With the aim of identifying and monitoring both the influence of PPCPs and the suitability of effluents to be reused, this study proposes the development of a composite indicator (CI) related to PPCP presence in WWTPs, through the common weight multi-criteria decision analysis (MCDA)-data envelopment analysis (DEA) model. Obtaining a CI for PPCPs is a novel approach in the published literature, showing a new perspective in PPCP management and their influence in wastewater treatment. Furthermore, this study proposes an improvement on MCDA-DEA model which maintains the initial hierarchy obtained for the units analyzed. The development of CI is based on information about the technological, environmental, social, and biological issues of WWTPs. Results show that 4 of the 33 WWTPs analysed had the best CI values, meaning that their effluents have lower environmental impact. The development of a CI related to PPCPs in WWTPs suggests that further steps are needed to manage the WWTP effluents. Hence, the need to implement preventive measures in WWTPs has been shown, even though the removal of PPCPs is not yet part of European law. This work highlights the importance of considering PPCPs as priority pollutants in wastewater management and reuse frameworks, to guarantee low environmental impact and adapt wastewater reuse based on a circular economy approach. HIGHLIGHTS: Emerging contaminants (PPCPs) are used as effluent quality indicators. A composite indicator for PPCPs performance has been developed through MCDA-DEA model. Indicator obtained allow decision makers implementing concrete actions to assess effluent quality. Results show the improvement capacity of the effluents quality through PPCPs removing.

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.

Identification and correction of congestion in wastewater treatment plants in the Community of Valencia, Spain.

The present work analyses the existence of congestion in a set of wastewater treatment plants (WWTPs) for the first time. The study sample included 47 WWTPs managed by the same operator and located in the Valencia region (eastern Spain). The method of analysis consisted in applying a new statistical model to identify and correct congestion situations based on data envelopment analysis (DEA), which takes into account undesirable outputs and multiple projections. The results showed a strong concentration of congested WWTPs (48.94-57.45%). Furthermore, the necessary corrections to avoid the congestion statuses entailed an average input reduction between 57.03 and 74.13% and an average increase in desirable outputs between 46.08% and 50.08%. In addition, only plant size had a significant relationship with the correction levels. The remaining contextual variables (age, overcapacity and type of water and sludge line) failed to show any significant impact on those corrections. To conclude, policy recommendations to improve the management of WWTPs are put forward, notably improving the management of smaller plants, which concentrate the largest percentage of correction.

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.

Monetary valuation of salicylic acid, methylparaben and THCOOH in a Mediterranean coastal wetland through the shadow prices methodology.

The presence of pharmaceutical and personal care products and drugs of abuse (PPCPs) in wastewater treatment plants (WWTPs) indicates discharge of the effluent may not be suitable for the ecological balance of water ecosystems, such as wetlands. These PPCPs degrade water quality, considered as an ecosystem service (ES), provoking serious environmental impacts. Assessing the monetary value of PPCPs can be used as a proxy for environmental status of the ES of water quality (ESWQ). Considering PPCPs as non-desirable outputs of WWTPs, the shadow prices methodology has been implemented using directional distance function to measure the environmental avoided cost of removing salicylic acid (SA), methylparaben (MP), and THCOOH from WWTPs effluents discharged to Albufera Natural Park (Spain). The SA shows the highest shadow price (138.16 €/µg), followed by THCOOH (48.15 €/µg), and MP (30.66 €/µg). These values are interpreted as the environmental cost that would be avoided if SA, MP, and THCOOH were removed from WWTPs effluents. The non-parametric tests show that wastewater treatment technology, together with population equivalent (as a proxy of the size of urban areas) and seasonality are factors that influence shadow prices obtained. The approach used in this study highlights the use of PPCPs as status indicators of ESWQ quantified in monetary units. As a way to synthesize the essential concepts to implement the shadow prices approach, this study proposes a flow diagram to represent the relationship between all the factors involved in this work. The use of shadow prices methodology proves that removing SA, MP, and THCOOH is associated with a measurable improvement in the ESWQ of Albufera Natural Park. The findings of this study will be useful for plant managers in order to make decisions about the removal of PPCPs in WWTPs effluents.

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.