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India’s water security debate overlooks that nearly 80 per cent of used water returns as a potential resource.
Treating water and sludge together is vital: Biosolids can restore nutrient-poor soils and fuel industries.
Regulatory gaps, not technology, block safe reuse. Closing this loop is essential for a resilient, water-stressed India.
India is home to 18 per cent of the world’s population, but only 4 per cent of its freshwater resources. Much of the conversation around water security therefore tends to focus on supply, how to store more, distribute better and stretch what little there is. While necessary, this conversation remains one-dimensional.
Nearly 80 per cent of the water used, leaves our homes as 'usedwater'. In a water-stressed nation, this isn't just ‘waste’; it is a massive, untapped resource that returns to the system every single day. Until we bridge the gap between water supply and its inevitable return as a treated resource, our water security will remain a ‘leaky bucket’ — constantly trying to fill a container without addressing where the contents are going.
Water and sanitation are often treated as separate focus areas, but they are two sides of the same coin. When we talk about ‘treated water,’ the conversation usually stops at the liquid. We focus on how to clean the water for reuse in gardens or industry, but in doing so, we lose sight of another valuable ‘by-product’: The sludge.
Sludge is a nutrient goldmine. Whether it is faecal sludge from septic tanks and pits or sewage sludge from sewage treatment plants, this material is packed with the organic carbon, nitrogen, phosphorus, and potassium that India’s soils are starving for. About 85 per cent of India’s soils are deficient in organic carbon. By ignoring sludge, we are essentially throwing away the very nutrients we currently spend billions importing as chemical fertilisers.
The potential of this ‘waste’ is not a theoretical dream; it is a proven reality waiting to be scaled. We have already demonstrated two powerful pathways for reuse:
In agriculture: In Devanahalli, a small town in Karnataka, a low-cost treatment plant has been co-composting faecal sludge since 2015. The result? A nutrient-rich compost that meets Fertilizer Control Order norms and is so effective that local farmers actively seek it out.
In industry: Sewage sludge has a high calorific value, making it an excellent fuel source. By co-processing dried sludge in cement kilns or brick kilns, we can turn a disposal headache into a renewable energy source, reducing the industrial reliance on coal.
From the fields of Odisha to the kilns of the cement industry, the evidence is mounting: Sludge is a productive resource.
If the value is known and the technology is proven, why are piles of sludge still accumulating at sewage treatment plants? Why does sludge management continue to fly under the radar of our national water agenda?The answer lies in a combination of regulatory gaps and broken links. Even when treatment is successful, there is often no clear regulatory pathway or certification to move these biosolids into the market.
The Fertiliser Control Order of 1985 has yet to fully integrate treated human waste as a mainstream input. Without enforceable national standards and a testing infrastructure that guarantees safety, ‘waste’ stays ‘waste,’ piling up at treatment sites because there is no official "permission" to use it.
The quality of India’s rivers, the safety of its groundwater, and the health of its soils are all downstream of how we manage these outputs. From Devanahalli to Dhenkanal, we see that the technical barriers are not what is holding us back. Farmers want the product. Industries can use the energy.
The ‘sludge piles’ at our treatment plants are a physical manifestation of a policy gap. Regulatory gaps are, ultimately, a choice.
Water security must be understood as more than access to freshwater alone. It is about the responsibility to close the loop. Sanitation reuse must be recognized as a core pillar of our water strategy - not as a technical footnote, but as a practical, fundable pathway to a more resilient India.
This article draws on the Compendium on Biosolids Management: Way Ahead for India (GSCOE, IIT Palakkad, 2025), A National Framework for Biosolids Management in India: Transforming Waste into a Valuable Resource (CSE, 2023), Sludge for Food, Food for Thought - What if The Problem is The Solution? (CDD India, June 2024), Background Note to Quality in Faecal Sludge Management (NFSSM Alliance / WASH Institute, 2020), field data from Devanahalli and Dhenkanal FSTPs, field data from STPs in 5+ states and data from the Central Pollution Control Board.
Krishna Swaroop Konidena is a senior programme manager, Consortium for DEWATS Dissemination and member of NFSSM Alliance. Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth.