The reuse of biosolids from sewage and septage treatment plants in India presents a remarkable opportunity to transform waste into a valuable resource
Photo: iStock India has approximately 1,469 sewage treatment plants (STP) and more than 500 faecal sludge treatment plants (FSTP). An estimate suggested that these 1,460 STPs generate 104,210 tonnes of sludge per day and FSTPs generate more than 250 tonnes of biosolids every day.
Biosolids generated by these plants are rich sources of nitrogen, phosphorous and potassium — the three essential nutrients for crop production across the world. India relies on imports to meet its demand for phosphorous and potassium, the reserves of which are increasingly becoming limited and depleting.
Treated sewage sludge from STPs can substitute 4,531 tonnes per day of urea used in agricultural activities in the country, estimates showed.
Biosolids, when treated and processed, possess high organic matter content, essential nutrients and beneficial microorganisms, making them excellent for soil health improvement. They can enhance soil fertility, improve crop productivity and reduce the dependence on chemical fertilisers.
The reuse of biosolids also aligns with the principles of the circular economy and supports the achievement of United Nations-mandated Sustainable Development Goals, highlighting its importance and positive impacts it can have on both local and global scales.
Delhi-based non-profit Centre for Science and Environment (CSE) on biosolids recently evaluated the quality of biosolids from 47 FSTPs and 14 co-treatment plants across India. The report with the findings represents the first-of-its-kind assessment done at this scale in India as well as globally. Here is what the report showed:
To explore the ways to reuse bio-solids and carry forward the learnings of the CSE report, the organisation, in collaboration with the Department of Housing and Urban Development (HUDD), Government of Odisha, conducted a workshop on “Reusing Bio-Solids Harvested from Septage and Sewage” on September 15, 2023 in Bhubaneswar.
The workshop was attended by experts and practitioners from other parts of India. About 50 municipal officials, representatives from para-state agencies and practitioners from Odisha participated.
Odisha is a pioneer in the sanitation journey and has constructed 118 FSTPs and STPs across 115 urban local bodies (ULB), G Mathi Vathanan, principal secretary, HUDD said in his inaugural speech. The state-wide rollout of convergence of rural and urban sanitation, he added, will further help in the treatment of more volume of faecal sludge and septage and, as a result, the amount of biosolids will be generated more. Therefore it is pertinent to have a solution for this issue.
The main barrier in reuse of harvested bio-solids from septage and sewage is its non-conformity with the Fertilizer Control Order of 2022, for meeting compost standards for organic waste and presence of pathogens and heavy metals, said Vinod Vijayan, deputy laboratory head at CSE. He stressed upon the quality of dried biosolids focusing on the carbon-nitrogen ratio and heavy metals.
Accelerated drying through innovative means such as solar greenhouse can aid in 40 per cent faster sludge drying and helminths inactivation.
The windrow method of co-composting treated faecal sludge with municipal wet waste eliminates pathogen contamination and helps in maintaining proper nutrient balance if done scientifically.
As per a study conducted by CDD India, a Bengaluru-based non-profit, the final matured compost meets most of the Fertilizer Control Order standards and is free from pathogen contamination.
Thermal treatment through dryer and pyrolyzer converts biosolids to biochar, eliminating all the pathogens, reducing the volume and confirming to the Class A biosolids, as prescribed by the Environment Protection Act. It can further be reused as a soil conditioner but further research and market for the reuse of biochar is still unexplored in India.
Besides the technical aspects of the reuse of biosolids in India, another important aspect is their market or appropriate business model.
An aggregator-based business model was presented by Finish Service Management Company Pvt Ltd. In this model, under a memorandum of understanding, the ULB bears the liability of providing raw materials — biosolids and organic waste, space for co-composting, labour and cost for lab tests. The aggregator is to provide technical and handholding support, product development support and marketing support.
The revenue generated by the sale of the product is shared between the ULB and the aggregator. This model provides a simple solution for reuse of biosolids, additional revenue source for ULBs, reduces soil and water contamination, reduces CO2 emissions, provides a substitute for chemical fertilisers and also livelihood creation as production and marketing is done by local people. This sets an excellent example of a public-private partnership.
The Toilet Board Coalition, working on applicable business models for reuse of biosolids, also suggested three models for enabling their reuse. One is from FSTPs to aggregators then to the end consumer.
Second is the online sale by ULBs by the permission of the state mission director and the third is engaging the small and medium entrepreneurs for the co-composting process. But all these models require an enabling environment to work effectively.
Ashok K Patra, Emeritus Scientist & Former Director, ICAR-Indian Institute of Soil Science, Bhopal, emphasised on the reuse of the biosolids in agriculture, considering the macro and micro nutrients value of the biosolids and a huge quantum of volume produced all over the world.
According to The State of Biofertilizers and Organic Fertilizers in India, about 85 per cent of the soil is deficient in organic carbon; 97 per cent in available nitrogen; 83 per cent in phosphorus; and 71 per cent in potassium.
The application of biosolids on land will not only help replenish macronutrients but also micronutrients. Through SWOT analysis, Patra showed the advantages and disadvantages of reuse of biosolids in agriculture but with proper safety measures and barriers, the biosolids application in agriculture can bring positive impacts on soil.
While the potential of biosolids reuse is immense, several challenges need to be addressed for its effective implementation in India:
The reuse of biosolids from sewage and septage treatment plants in India presents a remarkable opportunity to transform waste into a valuable resource. Government missions and programmes such as Swachh Bharat Mission, AMRUT, Waste to Wealth Mission, National Mission for Clean Ganga also promote circular economy.
By adopting sustainable practices and embracing biosolids reuse in agriculture, we can address multiple challenges simultaneously — improving soil health, conserving water resources, reducing pollution and enhancing food security.
It is time for India to recognise the potential of biosolids and take the necessary steps to promote their safe and efficient reuse. By doing so, we can pave the way for a sustainable and resilient future, where biosolids are not seen as a burden but as a valuable resource to be harnessed.
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