## 5 Conclusions  
Being a scarce but renewable resource, water possesses high economic value, and thus, water-related issues, namely its scarcity and reuse, have attracted larger attention in academia worldwide in recent years. Accordingly, the European Commission (EC) makes efforts to stimulate Europe's transition toward a circular economy. This action is expected to boost firms' competitiveness, foster economic growth, and generate employment. An important part of the environmental degradation is caused by the discharge of untreated or mistreated wastewater, making the reuse of water a central part of the National Strategic Plan for the Water Supply and Wastewater Sanitation Sector in Portugal and Spain. However, investment in resource management has been utterly neglected. Wastewater treatment plants mitigate environmental impacts and contribute to the financial savings of other firms. Though, the inefficiency of centralized treatment systems showed that the environmental issues must be tackled at the regional level. Furthermore, the assessment of WWTPs' financial and economic performance should also be a concern among scholars and stakeholders that study the economic viability of a resource recovery technology. Yet, the literature evaluating WWTPs' financial performance and economic sustainability does not abound. This paper is an attempt to fill the gap by analyzing the financial sustainability of WWTPs across Portuguese and Spanish NUTS II regions in 2016-2019. Using firms' financial reports from SABI, results show that several Portuguese and Spanish firms operating in sewage, especially the SMEs, present high levels of indebtedness, making it difficult to invest in ways to reuse water. In fact, in mean, 90.13% and 65.66% of total assets are financed by liabilities to Portugal and Spain, respectively. The number of firms is concentrated in the northern region in Portugal, which is the third region in terms of population density, while in Spain, most of the firms (17.9%) are concentrated in the region of Catalonia, which is the fifth region regarding population density. This fact suggests that the number of firms operating in this sector is not related to the population existent. Moreover, there are huge differences across regions, being the Algarve region (in Portugal) and La Rioja (in Spain), where firms performed better on financial and economic grounds when compared to the rest of the country. The superior performance of WWTPs in Algarve (since it is the region with higher profitability, less in debt, and more value added) can be explained in part due to a concession contract in 2019 that joined the water supply and wastewater sanitation systems. This allowed for important investments to improve water services and to maintain and rehabilitate the infrastructures, reinforcing the resilience of the system to face climate change. The north of Portugal is the second region with better financial sustainability, and it is also the region with more companies in the sewerage sector in the country. Regarding Spain, WWTPs in La Rioja are more profitable (ROA = 16.34% and ROE = 23.43%) and less indebted (debt ratio = 29.19%). These firms treat over 14,000 m3/day and have different wastewater treatment systems, such as extended aeration, low-load trickling filter, and subsurface flow wetlands. The sludge generated during the secondary treatment undergoes a centrifugal dewatering process with the use of polyelectrolytes. This sludge is stored in silos for subsequent use in agriculture. Financial analysis shows if a firm can obtain profit from its activity and to draw some conclusions on firms' ability to generate enough incomes to cover its costs and achieve a reasonable profit, i.e., to be economically and/or financially sustainable. Through the application of this financial performance measurement framework using a benchmarking methodology, it is possible to identify relatively strong and weak firms and regions.