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On the sludge management and reuse potential in Bangalore

May 12, 2014

One of the many critical factors affecting productivity in Indian soils is the absence of nutrients such as Nitrogen, Potassium and Phosphates. Even Carbon is in short supply as well as micro-nutrients such as Zinc and Boron.  AA substantial part of our artificial fertilizers is imported and we run up quite a huge bill. Fertilizer prices too are shooting up leading to an imbalance in their application. It has been reported for example that Urea which is relatively cheaper is over applied on soils causing more harm than good.

Cut to urban cities. Sewage treatment plants are coming up in large numbers. The Bangalore Water Supply and Sewerage Board –the utility responsible for sanitation and sewage, will eventually be setting up 25 sewage treatment plants treating nearly 1100 Million Litres Per day of sewage. These plants will mostly be secondary and tertiary treatment plants. Each million litre of sewage generates nearly a Tonne of sludge. Imagine 1100 Tonnes of sludge will be generated in the city of Bangalore alone. This is 120 truckloads of sludge.

There are smaller sewage treatment plants dotting the landscape in apartments and layouts too. These too generate smaller quantities of sludge. Overall this represents a management challenge of large proportions.

Research:  Currently at the GKVK-University of Agricultural Sciences – research work is going on to understand the nutrient value of this sludge. A Ph D student is pursuing her Doctorate and is experimenting on field trials using the sludge as manure. The initial test results show very good amounts of Potassium and Phosphates in the sludge.

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Separately sludge is also being picked up from Ecosan toilets. These are source separating composting toilets which segregate urine and solids. The solids are covered with ash after every use and desiccated before application as a fertilizer on soils. Farmers of Kamasamudram and H.D.Kote have such toilets in their homes and are very happy with the fertilizer they get. In fact this compost is priced at Rs 10 a kg.

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Sludge sells for upto Rs 10 a kg.

Similarly the landscape of rural India is dotted with pit toilets, more than 130 million of them at the last count. These too accumulate solid sludge and need to be emptied using mechanical systems. They are also found to be rich in Phosphates and Potassium.

All these various forms of sludge will be taken, tested applied on fields and crop productivity tested under expert supervision.

When research and application come together in a spirit of cooperation, it is possible to find solutions for India’s vast water, food and sanitation problems. At the base, this is a nutrient cycle at play. How we scientifically understand and manage it will show us the path to solutions. If every gram of sludge generated in our Sewage Treatment Plants become useful as manure it will partially solve India’s fertilizer needs and eliminate pollution. It will also increase productivity and richness of our soils as well as enhance the livelihood opportunities of farmers.

Recognizing and converting waste to a resource will help thousand of apartments and layouts, small and medium towns and even metropolis to manage their sewage efficiently for reuse and recycling. This would be water wisdom.

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