Swachh Bharat Abhiyan in peri-urban areas: Is groundwater being contaminated?

A study in Bengaluru's Nelamangala town found that poor sanitation structures are known to leach faecal contaminants into the groundwater.
Swachh Bharat Abhiyan in peri-urban areas: Is groundwater being contaminated?
Swachh Bharat Abhiyan in peri-urban areas: Is groundwater being contaminated?
Written by:

Priyanka Jamwal and Durba Biswas

By 2030, India plans to meet sustainable development goals (SDGs), including SDG 6, which states that every human being has a right to clean drinking water and safe sanitation. To its credit, India has a vision, in its Swachh Bharat Abhiyan, to eradicate open defecation and provide safe sanitation.

Under this scheme, funds are provided to households to build toilets. Since 2015, the scheme has resulted in the construction of over 31,04,542 individual household toilets. But in India’s growing peri-urban areas, Swachh Bharat’s one-size-fits-all strategy of building toilets may end up doing more harm than good.

Peri-urban areas comprise a mix of rural and urban characteristics, such as large amounts of agricultural lands co-existing with rapidly transforming urban spaces. These areas depend on groundwater for drinking and other domestic needs, and on on-site sanitation systems to manage human waste. But poor sanitation structures are known to leach faecal contaminants into the groundwater which can adversely affect human health.

To understand the links between poor sanitation structures and groundwater contamination, and to understand its fallouts, let us take the example of a peri-urban town called Nelamangala located on the outskirts of Bengaluru city. Nelamangala has a population of 37,232 and according to Census 2011, nearly 98% of the households here have access to some form of on-site sanitation system (either soak pits or septic tanks), which means that a large number of the families dispose of their waste (black water) locally underground. With nearly all middle and high income families having access to on-site sanitation systems, there is now a growing number of soak pits in this town that are close to borewells, which can pollute the local drinking water. 

Soak pits are typically 4 to 5 feet deep circular underground pits with concrete linings on the sides and an unlined bottom. The base of the tank is kept unlined to reduce the frequency of cleaning up the pit. According to our field studies, public and private borewells located in the town are in close proximity to these soak pits (figure 1a). Our data on the quality of groundwater shows that the levels of nitrates and faecal coliforms in the borewells situated within the town, are much higher than the borewells located away from the town, indicating a link between the soak pit density and groundwater quality (see figure 1b).

Figure 1a: Proximity of soak pits to borewells in Nelamangala town

Figure 1b: Nitrate levels in the Nelamangala town borewells 

By only focussing its efforts on building toilets to ensure safe sanitation, without considering the cost of unsafe sanitation systems, Swachh Bharat Abhiyan may compromise access to safe drinking water, in turn adversely affecting human health. And while middle and high income households can mitigate the impact of the contaminated groundwater by investing in expensive household level water treatment technologies like reverse osmosis, slum households bear a disproportionate burden. Slum households in Nelamangala report that water from the public standpipes makes them ill, forcing them to buy water cans for anywhere between Rs 15 to 40 per can, depending on the vendor.

Figure 2: Faecal coliform levels at various locations in the stream in Nelamangala town

Figure 3: Chloride levels in the borewells of Nelamangala town

Way forward 

For towns like Nelamangala, the need of the hour is to close the wastewater loop, which not only includes faecal contamination of groundwater, but also the treatment of wastewater generated by kitchens and bathrooms that get disposed into local surface water bodies without treatment.

Improved sanitation solutions need not be only in the form of underground drainage networks and a sizeable centralised wastewater treatment plant. Several studies in the past have reported the ineffectiveness of waste water treatment plants to prevent water pollution.

Instead, improved on-site sanitation systems that are easy to manage can significantly contribute to improved environmental and human health. Septic tanks are proven to be better alternatives to soak pits, and are easy to implement in rural and peri-urban towns where the segregation of black and grey water takes place at the household level.

One way to achieve this is by educating construction workers and households about the impact of soak pits and present them with better designs for septic tanks. Our study in Nelamangala found that irrespective of household income levels, all individual homeowners built soak pits and almost all of them were unaware of the difference between soak pits and septic tanks.

Faecal sludge and grey water management 

Faecal sludge is rich in nutrients and when harvested can be used as a replacement for fertilisers. The availability of agricultural land close to the rural and peri-urban spaces makes the process of transportation and usage of faecal sludge feasible. This presents the local government and panchayats with an opportunity to formalise the collection and marketing of faecal sludge by creating incentives to both the suppliers and the buyers.

For treating grey water, in-stream treatment technologies have proven to be effective, and offer the potential to remove grey water nutrients and faecal coliforms. These treatment technologies incorporate locally available materials and plants within the stream to remove contaminants.

In India, there is a long history of toilets being built but not being used for reasons like poor infrastructure, non-availability of water and poor location. The mistakes made in large cities need not be repeated by Swachh Bharat Mission in peri-urban areas. These areas present opportunities to try newer and more sustainable ways of managing waste. And given that these areas grow rapidly, it makes it all the more necessary for governments to consider alternative strategies.

Durba Biswas and Priyanka Jamwal are Fellows at ATREE (Ashoka Trust for Research in Ecology and the Environment) and their current research explores the links between groundwater contamination and sanitation in peri-urban areas, and how it affects the lives of those who reside in these towns.

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