Application of the Social Return on Investment for Onsite Wastewater Treatment Systems in the Republic of Indonesia

抄録

To achieve the Sustainable Development Goal (Goal 6), “ensure availability and sustainable management of water and sanitation for all,” private companies need to appropriately treat domestic wastewater discharged from their business sites. However, in Indonesia, conventional septic tanks emit large amounts of greenhouse gases (GHGs) and discharge effluents with high biological oxygen demand (BOD) directly into the environment. Japanese Johkasou technology, which has a high BOD removal rate, is expected to replace septic tanks. A previous study showed that GHG emissions from septic tanks were 1.8 times higher than those from the Johkasou systems. However, in addition to GHGs, other environmental and social impacts (related to the SDGs) should be considered. In this study, we analyzed the social return on investment (SROI) for replacing septic tanks with Johkasou at two sites around Medan City, Indonesia. Technical education and public consultation meetings held in parallel with the installation of Johkasou were also included in the scope of the evaluation. The results showed that the SROI was 1.10. As the SROI exceeded 1.00, the replacement was an effective investment.