DETECTION AND PREVENTION OF TOXIC GAS ACCIDENTS IN SALT WELLS OF KUTCH REGION

Ratan Das, Neelanjana Paul, Shreyasvi Natraj, Ayush Jain


Summary:

Generation of toxic gases in brine wells is a very frequent phenomenon. Every year there are numerous cases of accidents including fatalities resulting from harmful gases. Although there are industrial detectors available for toxic gas sensing, the high cost of such systems make them beyond reach of the salt farmers, who are one of the poorest section of 'producers' in our country.


So, we did a literature search to find various harmful gases that are generated in salt wells of Little Kutch region. However, we were surprised to find no study specific to Kutch area for this problem. But there are reported incidents of carbon monoxide, carbon dioxide and hydrogen sulphide poisoning in other wells and sewages across the globe. During our first field visit to Rann of Kutch, we talked to a group of salt farmers and one survivor (Ganpat bhai) for understanding the before and after effects of such accidents. Combining all inputs from prior art search, inspection of actual brine well sites, lab sample test and the farmers feedback, we concluded that hydrogen sulphide(H2S) is the prime cause for toxicity, although presence of other gases like carbon monoxide cannot be ruled out. But we were sure of hydrogen sulphide and thus took the challenge of designing a cost effective solution to detect H2S during this summer school. We decided to tackle the problem from two approaches- one using commercially available gas sensors and other by using basic chemical test method.


We came up with a very cheap (one rupee per test) paper based colour test method to detect H2S presence. The strip changes its colour when it comes in contact with H2S. To make the system more effective and robust, we designed an electronic system using a pair of simple light transducer and discrete electronic components that generates an alarm whenever the colour of this strip changes. The cost of all the discrete components together stands around 100 rupees. We tested the device in lab repeatedly and were thrilled to find a true alarm every time the system was subjected to H2S environment. During our brainstorming sessions and group discussions, we also discussed on possibility of a first-hand measure for providing little extra escape time to the person inside the well if a positive alarm is triggered and gas is detected. So we also made a simple gas mask using membrane cloth and activated charcoal, which is an effective H2S adsorbent. It can easily be replicated by anyone in home and is also very economic. So on our second field visit for testing the systems on real environment, we went to two different sites and inspected 7-8 wells. In first site, the water level was hardly couple of feet deep from surface, thus chance of gas presence was very limited. From one well where we detected presence of H2S during our first visit, we did get a positive detection of H2S using the colour strip but the concentration was very small. Also, we did get a good rise in carbon monoxide level reading from electronic sensor. Then we went for 2nd field, almost 30 km far from first site, where the wells were deeper (20 to 30 feet) and reports of occurrence of toxic gas accidents were more frequent. However, being an off season, all the bore wells were left covered with 3-4 feet of muds. We tried digging it by hand but were unsuccessful and so could not test our system there either. We happened to meet Veer Singh Ji, who was one of the farmers we talked to during our first visit. We demonstrated all our prototypes to him in field, and he liked the solutions, especially the idea of the pipe lid design.


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