The team that wants to end manual scavenging

Manual scavenging refers to the practice of manually cleaning, carrying, disposing or handling in any manner, human excreta from dry latrines and sewers. It often involves using just the most basic tools such as buckets, brooms, and baskets.  The Prohibition and Employment of Manual Scavengers and their Rehabilitation Act, 2013, disallows all kinds of employment that forces individuals to engage with human excreta manually.


However, in India the manual cleaning of sewage and manholes continues unabated.  The deaths caused because of this are an open secret.  It is a very hazardous, unsafe, insanitary occupation and above all it is legally banned. Often, it is treated as a “cultural occupation”, carried out only by a few so-called “lower” castes.


A report from the National Commission for Safai Karmacharis (NCSK) revealed the shameful fact that “In India, every five days, a manual scavenger dies in a sewer, septic tank or a manhole”. This story is about one person and his team who invented a solution with the mission to end manual scavenging in India.

Professor Prabhu Rajagopal from IIT, Madras and his team have worked at creating a robot called the “Sepoy Septic Tank Robot” to clean septic tanks without any need for manual human intervention.


In India, 40 percent of sewage is collected into septic tanks, mostly from semi-urban and rural areas that do not have a modern sewage system.  Septic tanks are connected to individual households, housing complexes or business parks.  They collect sewage/waste material which is stored and does not get transferred anywhere.  As per law, a septic tank must be cleaned at least every 2 years.

We interviewed Prof Prabhu Rajagopal to learn more about their innovation.


Q: How did you come up with this idea?


One of my research areas of interest has been developing underwater robots and submersible robots.  While developing one of my first robots, which was for the inspection of submersible pipes, I suddenly had the idea that we could perhaps use this with sewer lines.  So I went and checked it with the sewer lines in IIT but that attempt was not successful.  I continued thinking about this problem.  Once I had a discussion with an NGO called “Safai Karamchari Andolan” through which I got to realize that the problem of cleaning septic tanks was quite serious. As of now there is no satisfactory solution.


Q: How can this problem be solved? How did you visualize your robot being a solution?


Right now, I don’t think there are any practical, workable solutions to this. I have spoken with a company which is involved in septic tank cleaning using rods and so on. You would have seen workers carry rods to clean the tank and once you suck up the entire contents top to bottom it feels like a solution.  Another way can be to add some chemicals to these tanks so that the sucking out process is easier.


What could be done is that once all the contents have been sucked out, then people can go in.  But that is also dangerous, as sucking out the contents does not remove the poisonous gases inside.  Moreover, it is harmful because there are dangerous bacteria in it and workers often enter the tank without any personal protective equipment.  They don’t use any gloves or masks. I have seen people who have lost all their fingernails to this work. That is a terrible price to pay for cleaning tanks.


So that is how the whole project was born.  We were doing something similar but then I realized that it was not directly applicable to septic tanks because they contain different things.  They contain even sanitary napkins.  Conventional pipes get blocked in these conditions.


So I started some research with the Master’s students on developing propulsion systems like that of fish, I thought fins could be helpful.  We developed the first version of what we call a Sepoy Robot.  This robot works like a Sepoy for the septic tank. When we showed this to the safai karamcharis they said that it was useful but didn’t solve the problem fully.

The first step is to have a mechanical solution as there is sludge accumulating at the bottom of the tank, which can be removed mechanically. So we first attached a cutter to our robot and tried to work with it.  But we found that it was not sufficient as our robot was only a meter in length and moreover it did not have enough power.


So, in the last one year what we have been doing is to develop a heavy duty mechanical cutter which we can lower into the tank to cut the accumulated sludge.


Q: How far have you tested the robot in the field?


At this time, laboratory trials are going on.  After we developed this new cutter, we had to develop a laboratory version of a septic tank, because it is very hazardous to work in real conditions and we didn’t have the funds to setup a lab like that.


We are also working on a synthetic sludge to test out our cutter.  We performed several studies and we have come up with what we believe is a substance that behaves like the sludge in a septic tank. Septic tank sludge is actually a non-Newtonian fluid.  A Newtonian fluid like water cannot be cut with a knife, but the sludge is a substance that can start to flow if we shear it.  It has a very complicated behaviour.  I believe we have found a material with mechanical behavior similar to the sludge but there are other properties that we have not yet checked out.  For example, septic tank sludge gets harder with time and coagulates. Also, we are in touch with the Safai Karamchari organization and have requested them to give us some sites which are not hazardous anymore for field trials.


We hope our students will form an organization and take this forward.


Q: Can you please tell us more about the team who worked on this?


It has been a very multi-disciplinary team and the list is quite long.


Tanuj was the first person who worked on the idea.  He developed a robot in 2014, and since then I have guided a couple of Master’s projects — one by Santosh and one by Srikanth.  Then I guided 3 dual degree projects with Aman, Kanthikethan and Tanmay Mothe.  This year I have a student called Divanshu who is also a student of the dual degree course. He is the one who developed the standalone homogenizer that will be used as the first step of the solution. He has already graduated but is still working with me on the project. Now, I have also recruited a full-time employee, Sri Hari.


So, the team currently comprises of Divanshu and Sri Hari. It is also supported by a Ph.D. student called Vishakh and one of my Master’s students, Bhavesh.


Q: What are your future plans?


Our dream is that we should be able to create a device which can sense if homogenization is done, sense areas that can’t be reached and inform a base station which will then send another robot to clean the unreachable parts. I know it is a big dream but I am hopeful it will be a reality one day.


We later plan to use AI techniques in the robot for the purpose of enhanced connectivity and predictability.  If this idea is taken up as a startup company it will definitely need government funding.


Q: Any last thoughts or message?


Apart from any technical solution, at the individual level also, we have to change a lot to help matters. We have to see to it that we do not put any garbage in the toilet. We should not flush down any wrappers or sanitary napkins. Also, good maintenance of manholes is essential as they can cause contamination of the environment.