Original Article
Study on the implementation and operational cost calculation of by-product utilization system in sewerage management
Chihiro Konasugawa and Akira Nagamatsu  
Tohoku University, Sendai, Japan

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Global environmental issues have become increasingly serious in recent years and have had a major impact on the economy and society. Water-related problems are one of these environmental issues, and effective utilization of water resources is required. One such measure is the utilization of energy from by-products generated in sewerage projects. It has been proven that the utilization of energy from by-products in sewage systems contributes to substantial reductions in greenhouse gas emissions, but in Japan, the utilization rate is not high. One of the reasons for this is a lack of consideration of the economic aspects of the project and concerns about investment costs. Therefore, in order to increase the utilization rate, it is necessary to verify the economic feasibility of this project, and this study will conduct such verification. In order to verify the economic feasibility of this project, the city of Yokohama, which already has several years of experience in this field, was selected as the target city, and a hypothesis was formulated that the project would be economically useful. Specifically, it was assumed that energy utilization of by-products would lead to lower energy demand and energy sales, which would contribute to lower running costs. In addition, two sub-hypotheses were developed for specific verification. Sub-hypothesis 1 assumes a large-scale investment type that comprehensively implements everything from sewage treatment to the conversion of by-products into energy. Sub-hypothesis 2 assumes a small-scale investment type in which the fuel and energy conversion portions are outsourced. The verification of sub-hypothesis 1 and sub-hypothesis 2 was conducted by simulation and by using the financial data of Yokohama City, respectively, and it was confirmed that each of them contributes to the reduction of running costs. Based on the above, the hypothesis was judged to be valid.


  1. Sewerage
  2. By-product
  3. Cost calculation
  4. System dynamics