Written by Sakthi Sangeetha Devi, Consultant – Word Lab, IIHS.

Having heard and read a lot about Fecal Sludge Treatment Plants (FSTPs), their treatment methodologies, challenges and expansion plans for over a year, I was excited to finally see a facility in person. Among the 39 FSTPs and 48 Sewage Treatment Plants (STPs) currently treating fecal sludge in the state, the plant in Tenkasi was well-known for its meticulous operation and maintenance. When I entered the plant, I knew why. It was an unassuming structure, without a hint of its critical role in the sanitation cycle. Spread over 8,000 square metres, the plant was a part of a larger solid waste management (SWM) site.

It was 10 am on a Friday this month, and the sun was blazing over us, with a half-hearted breeze trying to twirl the heat away. The FSTP was abuzz with six workers getting ready for the day, scattered across various sections of the plant and other treatment units in the vicinity. Soon, they were joined by a couple of de-sludging operators who had just driven in with the first load of the day. Talking animatedly, they donned their personal protective gear to empty the vehicles lined up at the screen chamber. 

Walking across the roof of underground chambers, I wondered aloud about the distinct uses of the chambers below, all of which looked the same above. A technical consultant explained that being a gravity-based system, the subtle changes in the slopes of the chambers must be carefully marked during construction so that the sludge moves naturally to successive chambers for treatment without obstructing the flow.

He further added, “Already existing solid waste management sites are utilised for FSTPs so that fecal sludge can be co-composted without having to take up space for an additional facility. Although, once the legacy waste is cleared, it alters the soil profile, which means, each SWM site has to follow customised construction methods.”

I moved towards the screen chamber, where septage enters the plant. I assumed the trucks would start emptying the sludge into the chamber right after entering, but it was not before testing the quality of the loads. This prevents the disposal of non-fecal effluent in the plant, as it both threatens the safety of the workers as well as causes breakdown of the plant.

The plant operator explained to me that they reject loads if treatment parameters are not met. “If any other waste is emptied here, we have to even turn away treatable septage because the entire plant operation will be affected.”

After watching the de-sludging process, I followed the operator to the sludge drying beds. Walking between the sludge drying beds, I saw the actual process of dewatering itself visible across the entire length of the beds. Beginning with thick sludge mixed with liquid, the successive beds held increasingly dried sludge. The liquid had percolated through underground pipes and was collected for further treatment. Despite treating a highly ostracised waste, not one area in the plant showed signs of what was being processed. When I admired the immaculate premises, the operator informed me, “We regularly clean the units and maintain the plant hygienically. In fact, we even have our lunch inside the plant.”

As I moved to the next the part of the system, the various other treatment units caught my eye. The multi-purpose treatment site promoted collaboration between solid waste and fecal sludge management systems. The dried sludge was co-composted along with the organic waste in the composting centre, whereas the debris was discharged with waste from the resource recovery centre. Even the treated water was reused for gardening within the plant premises.

At a corner of the plant, a mound of dried sludge awaited co-composting after which it would be distributed to farmers. It became evident to me that improvements to sanitation come from various perspectives, especially local knowledge. Discussing methods for disposing of dried sludge, an elderly operator of the plant remarked, “This (dried sludge) doesn’t have the same nutritional value as animal waste. So, it cannot be used separately. But the co-composted waste is well-received here as it improves the soil fertility.” Impressive example for circular usage, isn’t it? 

Reflecting on the visit, the importance of every sanitation stakeholder in maintaining public health became apparent to me. It is easy to forget about waste once it leaves our home—unless we are affected in some way, like the odour from dump yards or blocked drainage in our streets.

With the administration keen on implementing innovative solutions, and skilled resources available for operation and maintenance of treatment facilities, we, as waste generators, need to be more aware of the full cycle of sanitation. Until then, we cannot truly appreciate the significance of treatment plants in our lives. 

Further Reading

  • Indian Institute for Human Settlements. (2025). TNUSSP Annual Newsletter. In TNUSSP.
  • Sebastian, O. S., & Sundar, S. (2018, May 2). Why does your drain smell so bad? TNUSSP.

Acknowledgements

I thank Sivaraj, Sasikumar and the Tenkasi FSTP workers for their detailed technical inputs.

Special thanks to Sofia Juliet Rajan for the crisp editing. 

Photographs: Anand and Sivaraj