Theme 2 — Closing the Loop Across the Sanitation Service Chain
From individual toilets to verified, safe and sustained resource use
This programme does not begin with the question: what valuable products can be made from sanitation waste? It begins with the more demanding question: under what technical, operational, financial and institutional conditions can sanitation flows be safely converted into water, energy and nutrients — while protecting public health, safeguarding workers and keeping services affordable?
A system is not circular merely because a treatment plant produces treated water, biogas or dried sludge. Circularity is achieved only when waste is safely contained and collected, it reaches an authorised treatment facility, treatment consistently produces an output suitable for a defined use, workers and users are protected from exposure, the recovered product is actually used, and its use displaces freshwater, fossil energy, chemical fertiliser or another virgin resource.
Sulabh International has long considered public toilets as potential sites for decentralised resource recovery. A historical Sulabh technical paper describes public-toilet-linked biogas systems in which human excreta and flush water enter an anaerobic digester by gravity, with biogas used for cooking, lighting and electricity, and treated effluent proposed for toilet cleaning and horticulture.
Circular sanitation begins after a toilet is used, but it cannot be studied only at the treatment plant. We follow water, human waste and recovered resources across the complete sanitation service chain:
Use and water consumption → containment → inspection and emptying → transport → treatment → quality assurance → reuse or safe disposal
Drawing on Sulabh International's experience across household, school, institutional, public and community sanitation systems, the programme conducts research in real implementation environments: public toilet complexes, onsite containment systems, desludging routes, treatment facilities and resource-reuse sites.
A central focus is the economics of desludging. We examine household affordability, operator viability, transport distance, scheduled emptying, differential tariffs, municipal support, cross-subsidies and the relationship between regular desludging and treatment-plant performance.
The programme also places sanitation workers at the centre of the service chain. Research examines mechanisation, occupational exposure, wages, skills, social protection and dignity — ensuring that circular sanitation does not transfer environmental risks onto workers or depend on hazardous and stigmatised labour.
Our objective is to generate evidence for sanitation systems that are environmentally safe, financially viable, climate-resilient and socially just.
Sulabh's public-toilet network provides a real-world environment for studying the generation and management of blackwater, greywater and solid waste. Research will examine water used for flushing, bathing and cleaning, hourly and seasonal user variation, blackwater strength, detergents and disinfectants, septic-tank loading, sludge accumulation, biogas production, treated-water reuse, energy consumption and actual freshwater displacement — across railway and bus stations, markets, hospitals, tourist and pilgrimage centres, and neighbourhood community toilets.
Desludging is the logistical link between millions of onsite sanitation systems and treatment facilities. Research will follow sludge through inspection → booking → emptying → transfer → transport → authorised discharge — examining demand-based versus scheduled emptying, vehicle size and access, volume removed, distance and travel time, cost, user fees, municipal subsidies, illegal-disposal incentives, worker contact with untreated sludge, and GPS and digital manifest reliability.
Research will be conducted at standalone faecal-sludge treatment plants, co-treatment facilities, public-toilet-linked anaerobic digesters, Sulabh effluent-treatment systems, drying beds, co-composting facilities, solar sludge dryers and compact non-sewered treatment units. Performance will be evaluated through incoming volume and load, percentage of design capacity used, pathogen and helminth compliance, biogas production, treated-water quality, biosolids safety, lifecycle cost and worker exposure.
Calculating the full cost of service delivery — vehicle capital, driver wages, fuel, maintenance, insurance, route density, treatment fees, seasonality and the cost of legal disposal compared with illegal dumping. The central question: which service and financing model can simultaneously achieve universal coverage, household affordability, operator viability and adequate treatment-plant loading?
Comparing demand-based household payment, scheduled municipal service, sanitation tax, monthly subscription, institutional cross-subsidy, geographic route contracts, bundled emptying and treatment contracts, household vouchers and differential tariffs.
Testing whether separating bathing, handwashing and cleaning water from toilet wastewater improves treatment performance, enables more stable anaerobic digestion, allows simpler greywater treatment, reduces freshwater demand and lowers transport requirements.
Measuring actual gas yield, seasonal variation, minimum viable user load, effect of bathing and cleaning water, effect of disinfectants, gas leakage, generator uptime, cost of gas cleaning, value of displaced energy and digestate-treatment needs.
Matching treated water to clearly defined uses — toilet flushing, floor cleaning, landscaping, construction or agriculture — and measuring volume meeting the required quality, volume actually used and litres of freshwater demonstrably displaced per 1,000 toilet visits.
Examining whether sludge and pit contents meet defined safety requirements before being described as a recoverable product — testing pathogens, helminth eggs, heavy metals, emerging contaminants, antimicrobial resistance, nutrient content, storage stability and farmer acceptance.
Mapping worker exposure across the sanitation chain and testing improved equipment, training, contracts and monitoring. The long-term target: zero avoidable contact with untreated faecal matter.
Testing cluster systems serving groups of public toilets, schools, markets and transport hubs — determining the optimal balance between treatment scale, land requirement, transport distance, load stability, operator skill, capital cost and environmental performance.
Adding risk-based research on pharmaceuticals, antimicrobial-resistant organisms and genes, microplastics, PFAS and endocrine-disrupting compounds — particularly important where recovered water or biosolids are applied repeatedly to soil or crops.
Jha, P. K. Recycling and Reuse of Human Excreta from Public Toilets through Biogas Generation to Improve Sanitation, Community Health and Environment. Sulabh International Academy of Environmental Sanitation.
Historical technical paper describing Sulabh's public-toilet-linked biogas, separated greywater, effluent treatment, reuse and operating model.
Learn more about Sulabh's biogas workUnited Nations Environment Programme and GRID-Arendal. (2023). Wastewater: Turning Problem to Solution — A Rapid Response Assessment.
Establishes the global circular-economy opportunity associated with water, energy and nutrient recovery.
View reportWorld Bank. Citywide Inclusive Sanitation Initiative.
Frames sanitation as a service across the complete chain and supports appropriate combinations of onsite, decentralised, sewered and centralised systems.
View sourceWorld Health Organization. Guidelines for the Safe Use of Wastewater, Excreta and Greywater.
Provides a risk-based approach using health targets, treatment and exposure-control measures appropriate to specific reuse pathways.
View guidelinesWorld Health Organization. (2022). Sanitation Safety Planning: Manual for Step-by-Step Risk Management for Safely Managed Sanitation Systems, second edition.
View manualInternational Labour Organization, WaterAid, World Health Organization and World Bank. (2019). Health, Safety and Dignity of Sanitation Workers: An Initial Assessment.
Documents occupational, legal, financial and social risks across sanitation work.
View reportNITI Aayog and National Faecal Sludge and Septage Management Alliance. (2021). Faecal Sludge and Septage Management in Urban Areas: Service and Business Models.
Includes scheduled desludging, affordability, co-treatment, cluster systems, digital monitoring, inclusive operations and resource recovery.
View reportNITI Aayog. (2023). Reuse of Treated Wastewater in Urban/Peri-Urban Agriculture in India.
Addresses wastewater quality, governance, monitoring and demand for agricultural reuse.
View reportMinistry of Housing and Urban Affairs. (2025). Advisory on Promoting Offtake of Treated Sewage Sludge Using Solar Greenhouse Dryer.
Addresses dewatering, pathogen reduction, worker handling, quality and use of treated sludge as a soil conditioner.
View advisoryTyagi, M., Centre for Science and Environment. Evaluation of Faecal Sludge Treatment Plants Across India.
Assessment of 47 plants across seven states, identifying variation in treatment performance, plant underutilisation, inconsistent sludge supply and O&M challenges.
View reportMehta, M., Mehta, D. and Yadav, U. (2019). Citywide Inclusive Sanitation through Scheduled Desludging Services: Emerging Experience from India. Frontiers in Environmental Science.
Examines scheduled municipal desludging and performance-linked service models in Wai and Sinnar.
View articleGlobal Sanitation Center of Excellence, IIT Palakkad, and International Water Association. (2026). Second International Conference on Non-Sewered Sanitation Systems — ICNSS 2026.
Research themes include energy recovery, greywater reuse, sludge drying, biosolids, circular business models, AMR, emerging contaminants, climate resilience and lifecycle cost.
View conferencePhotographs from the field will be added to this page soon.