2025 年 16 巻 2 号 p. 81-90
Urbanization, coupled with inadequate sewage infrastructure, results in the accumulation of septic tank sludge, which poses significant environmental and public health risks. This study explored the potential of transforming dewatered septage into a valuable agricultural resource through composting, aligning with the goals of sustainable development and rural-urban synergy. This study investigated the composting of dewatered septage mixed with bulking agents (rice straw, sawdust, and wood chips), focusing on key environmental management aspects such as pathogen reduction, nutrient cycling, and heavy metal stability. Pathogen reduction was significant, with E. coli levels in rice straw and sawdust compost falling below the EPA Class A standard of 1,000 MPN/g, whereas wood chips met Class B standards with levels below 2,000,000 MPN/g. The composts contained no viable helminths, ensuring their safety for agricultural use. Nutrient analysis revealed suitable levels of nitrogen (2.20% in rice straw, 1.08% in sawdust, and 2.22% in wood chips), phosphorus (1.98% in rice straw, 0.70% in sawdust, and 1.97% in wood chips), and potassium (0.77% in rice straw, 0.04% in sawdust, and 0.14% in wood chips), which support soil fertility and land conservation efforts. This study provides a sustainable, circular approach to septage management, highlighting its potential to enhance soil quality, reduce environmental pollution, and promote climate resilience. This composting method offers an innovative pathway for transforming urban waste into agricultural resources, fostering rural-urban synergy, and supporting sustainable development. Future studies should optimize composting conditions and explore the long-term benefits of composting for agricultural productivity and environmental health.
