How to sustain municipal sanitation: Delhi’s Aya Nagar offers some lessons

The pilot project is a prototypical model for evolving a sanitation management programme in a high density settlement

Plants growing in the reedbed system at Aya Nagar in Delhi. These have roots containing rhizomes which further clean the waste water generated by the project at the site. Photo: CSE

CORRECTION: This blog was published first on October 30, 2020. According to that version, the capital cost of the project mentioned in the piece was Rs 1.2 crore. This was corrected to Rs 2.1 crore on November 1, 2020. We regret the error

The fast pace of urbanisation is leading to the outgrowth of cities, expansion of peri-urban areas and increase in the number of urbanised villages, informal settlements and unauthorised colonies. These generally lack access to infrastructure services, particularly sanitation facilities. This often leads to environmental pollution and endangers the health of local residents.

This article attempts to examine how and the extent to which residents of one such unauthorised colony get access to improved sanitation. The findings show that community-led initiatives, partnerships and context-specific decentralised solutions are instrumental in improving the access to sanitation in such unauthorised colonies.

The case of Delhi 

Take the instance of Delhi, the capital of India, which is urbanising at a fast pace. Over the years, the number of villages has reduced to 112 in 2011 from 300 in 1961. The number of urbanised villages, meanwhile, has increased to 135 in 2011, from 20 in 1961.

Official statistics indicate that over four million people are living in unauthorised colonies. However, these unauthorised colonies lack the municipal services and utilities such as proper water and sanitation systems. 

In a recently concluded socio-economic survey of Delhi, 0.6 per cent households were found to still practice open defecation, 60.1 per cent of the households were connected to piped sewerage, 36.7 per cent had septic tanks and 1.2 per cent used toilets linked with open drains or open areas.

This leads to aesthetic nuisance, threat of organic pollution and several infectious diseases in epidemic proportions due to the contamination of ground water and drinking water resources.

Laying sewer networks is a cost-intensive and time-consuming project, keeping in view the city’s dynamics. It may not be financially viable to all areas of the city. On- site sewage management is gaining momentum as an alternative approach to the current conventional practice.

The advisory on On-site and off-site Sewage Management Practices by the Central Public Health and Environmental Engineering Organisation, Union Ministry of Housing and Urban Affairs, Government of India is a timely initiative to guide states / Union territories and other stakeholders on safe and holistic management of sewage and faecal matter. 

Case study of Aya Nagar

Aya Nagar, situated in southwest Delhi and adjacent to the Delhi-Haryana border, is one such provisionally regularised unauthorised colony and is majorly settled by migrants from all parts of the country.

Being an unauthorised colony, there was no provision for drainage. Hence, the storm water which flowed in open channels along the roads, also got mixed with sewage.

In a few cases, the sewage of houses was stored in a sump below them that were emptied by portable vacuum pumps and discharged in an unregulated manner, leading to unsanitary and extremely unhygienic living conditions for all citizens.

The open channels also became extended garbage bins, choked with plastic bags and other forms of solid waste. The open channels would overflow on the roads, especially when it rained — resulting in serious health hazards. 

GREHA, a non-profit primarily consisting of environmental design and planning experts based in Aya Nagar, spearheaded the challenge to improve the sanitation scenario of the neighbourhood.

The then-chief minister of Delhi, Sheila Dikshit, visited Aya Nagar in 1999 and declared it to be a model village. The Aya Nagar Vikas Samiti was then constituted and registered in 2001 to be the voice of local people, along with a task force to implement the plans proposed for development by the government.

In 2008, the government of Delhi, under a scheme of the Delhi Kalyan Samiti, granted research aid to GREHA, to propose options and possibilities that could be initiated to make Aya Nagar a role model. 

On-site sanitation approach

After extensive research and consultation with experts, GREHA proposed a new technology called small-scale (bore) sewer system in combination with the Biodigester technology developed by the Defence Research & Development Organisation (DRDO), that could be installed below the roads without entering private houses.

The project was started by mapping and surveying the neighbourhood, which included physical surveys, documenting the internal layout of the houses and conducting a demographic survey.

An important part of the project was to engage and consult with community members. A scale model was created and used as a planning tool. Delhi Urban Shelter Improvement Board (DUSIB) spearheaded the project.

Sewage treatment in the biodigester takes place through the action of a specially designed bacteria which is the inoculum introduced into the airtight container. The inoculum has the property of regenerating through its action with faecal bacteria to produce treated effluent.

Biodigester installation is 50 per cent cheaper than septic tank and gives out natural methane and carbon dioxide (minimal air and water pollution) and requires 25-30 per cent less space, compared to septic tanks. Per unit of biodigester for household costs Rs 30,000-50,000, based on the location. 

The treated effluent from the biodigesters, along with grey water from the households and rainwater undergo secondary treatment through bio-remediation in a 100 kilolitres per day reedbed system in the nearest suitable open space available.

Technical support for implementation of the reedbed system was provided by Delhi-based nonprofit, Centre for Science and Environment (CSE). In the reedbed, wastewater is circulated through a crushed stone medium. Within this are growing plants that have roots containing rhizomes which further clean the waste water.

The reedbed helps in removing nutrients from the wastewater. Reedbed-treated effluent is then passed through multi-grade filter and activated carbon filter for final treatment and disinfection.

The proposed reuse for the treated water is for road cleaning, horticulture, etc. Alternatively, it can be used for reviving the nearby Johad or percolation ponds. Currently, the treated water is being discharged in the open drain after the treatment due to the lack of funds.

Thus, the scheme shows a way of creating a closed loop water supply system, which, if carefully engineered to an extent across the urban area, could also play a major role in controlling the pollution of the river Yamuna.

This hybrid system has been put up in Z-block, Ayanagar which caters to the population of around 1,200-1,500, without disturbing the privacy of households and with no special maintenance requirement. The whole system cost approximately Rs 2.1 crore.

Project Key highlights of the sanitation system

Scale of Service

Community Level

Year of Installation


pH of treated water


Capital Cost

Rs. 2.1 Crores

BOD of treated water (mg/l)


Proposed reuse of treated wastewater

Non-potable (Road cleaning, horticulture, etc)

Technical layout of the project (Credit: GREHA)
Technical layout of the project (Credit: GREHA)

“The Aya Nagar project, devised and facilitated by GREHA, demonstrates a new urban paradigm which places the concerns of the marginalised majority at the forefront, using techniques to make urban systems responsive to the imperatives of social justice and ecological viability. Foremost being the management of the water cycle by decentralised sewage treatment and waste water re-use,” says MN Ashish Ganju, Principal Architect, GREHA
“The Aya Nagar project was an extremely challenging project where within an existing, high density slum-like habitation, underground systems were required to be laid out with minimal disturbance to the local residents. Once the fruits of the labour became visible in terms of management of sewage in the most sustainable manner, the ease and comfort that the installed systems provided to the local residents were extremely satisfying professionally. We also learned many things which will make designing and commissioning future decentralised sewage treatment system in high density habitations much easier and smoother compared to the one that we did at Aya Nagar,” says Manoj Jha, chief executive, Arkin Creations Pvt Ltd

Way forward
The Aya Nagar project has been instrumental in representing the will of the local community. The project is an example of a good, successful model for effective sanitation improvement by a decentralised sewage treatment system in a high density habitation. It was done with little political help and technical support. The project has caused remarkable improvement in the drainage and sanitation scenario of the Z block.

However, to make it a more robust and sustainable system, the following recommendations can be considered.

  • To work rigorously upon the information, education and communication of the community by using pamphlets and make them aware about the system
  • For proper operations and maintenance of the system, self help groups can be created in the community
  • New avenues for the reuse of treated water can be explored, which can ensure financial aid to the community

Through a community-embedded approach, the aim was to devise techniques for making the urban system responsive to the imperatives of social justice and ecological viability.

The Aya Nagar pilot project is a prototypical model for evolving a sanitation management programme in a high density settlement. The methods and techniques evolved will serve as a guide for informal settlements in Delhi and across the country.

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