A comprehensive economic analysis of the associated costs and benefits derived from wastewater treatment is a prerequisite for ensuring long-term economic, environmental, and social sustainability. This study aims to improve the economic evaluation of wastewater reuse. A methodological framework is presented for the application of cost-benefit analysis to wastewater project plants. The method considers two alternative scenarios for the irrigation use of treated water: (i) for newly irrigated land; and (ii) as an alternative to current groundwater sources. A case study is carried out in Puglia, Southern Italy, where two thirds of irrigation water comes from groundwater. The results show that improved urban wastewater treatment would increase the regional availability of irrigation water by 60 million m3 per year, about 10% of the overall irrigation water demand. While treatment costs are highly dependent on the incoming effluent quality and plant size, the benefits are quite stable. These results point to a case-specific analysis, whereby the economic convenience of wastewater reuse could be assessed against the local context.

The siting of solid biomass energy plants can be conceived as a transaction process talcing place between two specific economic agents, the investor and local community, The investor is interested in obtaining the use rights for local resources (e.g., area for setting; natural resources to feed the process, release of pollutants into the environment) while the community expects an increase in net benefits (e.g.. job opportunities, induced industrial development). This transaction process has been analyzed according to the typical transaction costs theory, where the economic activities are conceived as the result of transactions among economic agents, which are hindered by three main obstacles: i) bounded rationality, ii) opportunism, iii) asset specificity, By applying the New Institutional theory approach, we treat the issue of social acceptance as a transaction cost problem. The aim is to identify the best practices adopted by biomass firms' managers in order to enhance the social acceptance of solid biomass plants at the local community level, In this paper, we conduct a positive analysis where the methodological approach is based on the comparison of six successful study cases, This allowed us to identify twelve measures capable of fostering social acceptance and consequently of reducing the costs related to the investment.