Since 2014, India has made progress in sanitation. The country was declared open defecation-free in 2019, following sustained political commitment and community participation at all levels. With the construction of 6.3 million household toilets and more than 600,000 community and public toilets, urban areas have achieved universal toilet access, marking a key milestone.
However, with only 40 per cent of urban India connected to sewer networks and approximately 1,529 operational, under-construction or proposed sewage treatment plants (STP), the majority of toilets (60 per cent) rely on on-site sanitation systems (OSS).
To treat the waste generated from these on-site systems, around 1,500 faecal sludge treatment plants (FSTP) have been built using different technologies and capacities across India. However, many of these plants face underutilisation due to flaws in the planning and design phases.
Let us look at Uttar Pradesh — which is no exception. The state currently houses 59 treatment plants. As of December 2024, 19 out of 39 towns with FSTPs and six out of 20 towns with co-treatment facilities are operating at 20 per cent or lower treatment capacity.
This is due to a fundamental flaw — the one-size-fits-all approach to design capacity. Under Atal Mission for Rejuvenation and Urban Transformation (AMRUT), a fixed design capacity of 32 kilolitres per day (KLD) was adopted in 35 FSTP towns without considering local contexts and population dynamics.
Demand-based desludging refers to a household requesting a septic emptying service when the tank is full or when backflow in the toilet is observed. It remains a common practice in most areas. Initially, the shift from demand-based desludging — the prevalent practice — to scheduled desludging was advocated to maintain the performance of septic tanks and mitigate environmental risks. However, scheduled desludging also improves treatment plant utilisation.
Scheduled desludging ensures regular desludging of all properties along a defined route, with property occupants notified in advance. In this system, all septic tanks in the city are desludged once within a fixed cycle according to a predetermined schedule. The service is provided by a government-licensed operator, similar to an annual maintenance contract (AMC) for appliances like water filters or air conditioners, or the way solid waste is collected daily from households.
In 2018, Wai, a small town in Maharashtra with a population of 45,000, became the first in India to implement scheduled desludging.
In Wai, the service is provided through a public-private partnership (PPP) model, where desludging is carried out by a private contractor engaged on a performance-based annuity contract. The local government makes payments to the contractor based on performance targets, funded through a “sanitation tax” added to property tax bills.
The town reported an increase in desludging numbers due to mandatory desludging. The frequency was increased from 8-10 years to three years, resulting in a 33 per cent rise in desludging coverage, compared to just 2 per cent previously. The improved desludging frequency also enhanced the efficiency of septic tanks, leading to better quality supernatant with reduced BOD and coliform levels, thus contributing to positive environmental outcomes.
Additionally, as all properties — including private, commercial and slum areas — were covered, the cost of desludging services was reduced due to assured demand and optimised trip routes, enhancing both equity and affordability.
Although scheduled desludging has several advantages, it also comes with challenges. While implementation is relatively straightforward in small towns with populations under 50,000, the complexity of collecting baseline data increases significantly in medium-sized towns. Furthermore, revenue generation through an added “sanitation tax” within property tax structures is only viable where collection rates are high.
Implementing such an approach is challenging, particularly in Uttar Pradesh. The state has low property tax collection rates and lacks accurate baseline data on households with septic tanks. In such a scenario, a different approach was required — one that mitigates these challenges while ensuring improved treatment plant utilisation.
One such alternative, advocated by Delhi-based think tank Centre for Science and Environment (CSE) in Uttar Pradesh, is scheduled institutional desludging. This involves the mandatory desludging of septic tanks in all government-owned or managed establishments, including community and public toilets (with high footfall), government offices and buildings, housing colonies (Awas Vikas), educational institutions, hostels, healthcare centres, hospitals and community halls, at fixed intervals.
Meanwhile, residential and commercial properties remain on a demand-based desludging system.
Municipalities must categorise establishments based on footfall — high footfall areas like community and public toilets and low footfall areas like government offices and housing colonies — before setting desludging frequencies suited to the local context.
Once this framework is in place, a list of establishments with desludging schedules under one year and those exceeding one year is prepared. A daily desludging schedule is then shared with the desludging operator for execution. On September 13, 2024, the Department of Urban Development, Government of Uttar Pradesh, issued Guidelines for Improving Treatment Plant Utilisation through Implementing Scheduled Institutional Desludging Plans to all AMRUT towns.
The desludging services are provided by government operators, with expenses covered by the municipality. Over time, this could be extended to households and commercial establishments, reinforcing the principle that "sanitation is a public service."
This combination of demand-based desludging and mandated institutional desludging ensures a consistent supply of sludge to treatment plants, improving their capacity utilisation.
While this approach is easier to implement than full-scale scheduled desludging, challenges remain. Municipalities must be adequately trained to follow the correct implementation approach. Additionally, gathering accurate baseline data on all establishments remains a difficult task.
A field study conducted by CSE in 18 cities in 2024 revealed that implementing this combined approach could enhance treatment plant utilisation in Uttar Pradesh from 40 per cent (under a purely demand-based desludging system) to as much as 64 per cent of capacity.
So far, Saharanpur has implemented this approach, resulting in capacity utilisation of over 90 per cent in a 25 KLD co-treatment plant, up from the previous 10 per cent.