Evolution of sewage management: exploring the role of Japanese decentralised Johkasou systems in shaping India’s future effluent treatment landscape

The evolution of sewage management has been integral to human progress, shaped by societal, cultural, and technological developments. In India, rapid urbanization, uneven population distribution, and increased migration have challenged the establishment of centralized sewage treatment plants, making onsite sewage management a viable alternative. In this context, the Johkasou system offers a promising alternative to enhance India’s sanitation infrastructure, thus the current study aims to identify the deficiencies in current sewage management strategies and evaluate the potential of Johkasou systems to address these gaps. Through a historical analysis of sewage engineering, the study highlights the transition from basic disposal methods to modern treatment and resource recovery practices. This study also considers how advancements in sewage management practises have influenced urban design - a critical aspect in integrating Johkasou systems into urban settings. A preliminary case study supplementing the review was conducted to draw a comparison of Johkasou system, traditional septic tank, and centralized sewage treatment plant in Vellore, Tamil Nadu, India in terms of effluent quality revealing COD and BOD removal efficiency equivalent to 92.7% and 95% in Johkasou system, which forms the preliminary indicators in sewage treatment system analysis. The review combined with the case study highlights the role of Johkasou system in achieving SDG 6 in demographics similar to the Indian subcontinent.