In this study, we confirmed the stable wastewater treatment capacity and effectiveness of the portable unit-type sewage treatment system under disaster conditions. This unit-type wastewater treatment system was constructed in a short period of 26 days. In addition, effluent water quality of this system for one year were less than 15 mg/L for BOD and less than 3000 CFU/mL for total coliform. Furthermore, the GHG emissions of this system were comparable to the conventional activated sludge process. These results suggest that the application of this system to the damaged wastewater treatment plant can quickly recover the water treatment function.

 Although the revenue from sewerage charge is expected to decrease, especially in small municipalities because of the decline in population, they are obliged to decrease the emission of greenhouse gases. To address these problems, the Japanese government supports the development of innovative technologies that will reduce costs and energy consumption in wastewater treatment plants. However, the developed technologies for small-scale treatment plants have not yet been widely used. This study aimed to evaluate innovative technologies with multiple indicators, and clarify the obstacles to the introduction of those technologies through the analysis of sewerage statistics, sewerage management plans and interviews with related parties. It was found that those technologies have high potentials to save energy and cost; however, it was difficult to compare the efficiencies among them. Additionally, because small-scale treatment plants have not yet been due for renewal, they tend to postpone the installation of new technologies. Furthermore, the result of stakeholder analysis has revealed that there is a structural problem of discrepancy in the needs and different incentives for new technologies among the stakeholders, namely, the national government, municipalities, companies, and residents. Therefore, to promote the practical application of new wastewater treatment technologies, it is important to develop and support the introduction of technologies that can achieve national objectives and fulfill the needs of residents and municipalities concurrently, and to delineate their benefits to the residents and municipalities.

 Since the outbreak of COVID-19, it has been proposed to utilize wastewater information such as virus concentration and gene sequence information for infectious disease control. In this study, we evaluated the willingness to pay for sharing wastewater information with general populations. A web questionnaire was conducted in Sendai City, where a website for wastewater information sharing is operated and its information is disseminated by e-mail and TV reports. Among the six types of wastewater virus information surveyed, the willingness to pay for "sewage virus detection information in the city" was the highest at 306 yen/person, and "judgment of convergence in the city" was the lowest at 227 yen/person. Based on the assumption that the cost (C) for obtaining information on six types of sewage viruses is independent of each other, the ratio to the benefit (B) was calculated on a trial basis. As a result, B/C values of 1.3 to 4.9 were obtained for all six types of sewage virus information.