Prevention of unintentional exposure to toxic gases in the wells
By: Awanish Kumar, Mathias Dockweiler, Swapnil Prasad, Tanisha Sushil
Toxic gases are formed inside farm wells, sceptic tanks, chick farms due to prevalence of anaerobic conditions and decomposition of organic matters. Common sites for toxic gases are farm well, septic tanks, sewers and natural gas operations. Majority of exposures are unintentional. Exposure leads to convulsions, coma and rapid loss of consciousness. Studies across globe have shown that poisoning with toxic gases cause blockade of oxidative phosphorylation during electron transport chain and inhibit various bio-enzymatic processes in our body. These gases rapidly distribute to vital organs like liver, lungs and brain. Later two are very prone to damage due to toxic exposure and gases like hydrogen sulphide (H2S) damages respiratory center in brain, cardiopulmonary damage leading to instantaneous death in a single breath beyond a threshold limit of around 1000 ppm.
Primary intended beneficiaries: Salt farmers, Chick farmers, Swine and Sewage tank sanitation workers where there is high level of hydrogen sulphide leads to death of people concern.
Chosen problem area: There are reports of unintentional exposure of toxic gases to salt farmers in farm wells of little Rann of Kutch. This is an occupational exposure. Method to prevent such toxic exposure to farmers and devise a strategy to prevent such tragedies is need of this hour.
Interaction with beneficiaries and prototype design: We found that majority of wells are around 5 to 20 feet in depth and 3 feet in breadth. We have not found any fencing around well observed and there were sign of water seepage leading to fragmentation of soil around it. Also there was no arrangement of stairs found in any well. Instead they dug the hole in order to move inside well. It is very risky and there is need of safety belts and proper mechanism which can safely take them out in case of emergency or knockdown in case of gas tragedy or during rescue operation.
On enquiry we found that this is a seasonal problem and they face it just after digging the old well for reuse. They told us about process of digging and closing of well during off season. It appears that after rain there is increase in water table which leads to filling of air pores present in soil. This leads to accumulation and spreading of gases through pipes. They also told this problem subsidise with time and not found in running tube wells. We thought that it might be due to decomposition of organic waste as well as inorganic type of situation present inside the deep bore. They predict the presence of toxic gases inside well by burning flame. If this flame suddenly extinguishes inside well, there is a possibility of toxic gases. This hints towards the presence of Carbon monoxide (CO) or CO2; as methane (CH4) and Hydrogen sulphide (H2S) are flammable in nature. This type of gases has also been reported in chick farms, swine farms leading to their low mass due to toxicity. Many times sanitation worker died in sceptic tanks during cleaning of tanks. This type of episodes can be eradicated by proper installation of aerator and ventilator in such sites. This also leads to increase in oxidation of sewage due to presence of oxidative conditions lowering the chances of formation of toxic gases and hazardous events.
Name of people interviewed in Kharaghoda village:
Meru Bhai Popat Bhai
Bharat Kumar Bhopa Bhai
Navgadh Bhai Mohan Bhai
Raju Bhai Rama Bhai
Prahlad Bhai Nanu Bhai
Narayan Bhai Soma Bhai Padaliya
PROOF OF CONCEPT/ PROTOTYPING
In order to circumvent this problem, we rely on aeration and ventilation of well in a swift manner and propose our concept. The local people participated and have given critical comments about its feasibility, durability and what are the local solutions available for its fabrication. We refine our approach after this discussion and ideate again to fabricate a prototype. Next hurdle was how to develop this at their native place. On further corroboration with end user it appears that there is requirement of ventilator in off-season (June to October), peak season (October to May) and for chemical analysis of gases there is a need of proper sampling mechanism at safe site.
Potential of our ventilator in field for field use:
This is cost effective, easy to use. Our ventilator can be used in conditions where there is high level of accumulation of toxic gases which leads to casualties in our country. These are sewage tank, chick farms, swine farms and in tube well during rainy season. This ventilation approach will prevent the tragedy and protect the marginal people from unintentional exposure. Also our regulator design will also help in slow release of gases in a slow manner to avoid any type of blast and help in sampling of complex mixture of gases under laboratory conditions. It will prove boon to their life.
Toxic Gas Detection For Salt Farmers
By: Karan, Vedprakash and Aman
The salt farmers of Kutch face the difficulty of sudden release of toxic gases like hydrogen sulphide and carbon monoxide from the wells. The problem situation they face involve the digging and subsequent opening of bore wells located 20 ft deep underground. The farmers, after initially digging the ground and inserting the bore wells, cover them up with an equivalent amount of soil and leave them for a time span of 4 months, having secured the bore well openings with pieces of tightly-stuffed cloth. However,the problems appear after they come back after 4 months,for re-digging. Having asked them for the procedures followed and the problems originating.they informed of two such situations,one,where the piece of cloth stuck to the mouth of the bore well doesn’t fit in tightly enough and leads to the slow leakage and thus,consequent exposure to the already mentioned toxic gases,two,whence although the cloth is tightly securing the out of the bore well pipe,the poisonous gases leak and result in the formation of air pockets 3 ft above the bore well surface.Thus,as the farmer digs and reaches a height of 17 ft below ground,he is exposed to the dangerous gases.
The above mentioned problems occurs during the process of opening and reopening of the bore wells. However,during the process of fitting the water pipe into the bore wells,sometimes,due to sudden leakage of gases, might cause death. Also, some of the major consequences result due to carelessness. The farmers, during the process of fitting pipes follow two natural safety mechanisms, one of which is to introduce birds inside the pit and wait for their reaction time-whether they live or die.The other method involves the introduction of a ‘mashal’ of fire into the pit,if the fire torch keeps burning the general hypothesis is that the air isn’t polluted with poisonous gases,on the other hand,the fire torch burns out after some time which gives an indication of the content of poisonous gases. Sometimes,the farmers like to play with death, hence, they enter the well alone, without any support system above, without any other person knowing whether he’s dead or alive for a long time, after the inevitable has occurred . Also,they refuse to tie rope-guards around themselves,which could decrease their escape-time,resulting in succumbing to the poisonous gases.
The problem statement which had to be worked on involved the main problem of detection of the released poisonous gases by any means such as sensors or through the use of other safety measures.The product needed by them should be such that it comprises of a nozzle,through which the water pipe can be fitted such that the poisonous gases get trapped inside,through the creation of a vacuum suction,while allowing the water pipe to pass through.Next,the gases trapped inside need to react with a chemical buffer,such that they get consumed and do not possess a harmful effect anymore.
Observation (Field visit 1)
Our field visit was based on detecting the problems of the salt farmers while digging the well and the process of the gas release which takes place throughout the duration of salt farming. The key findings which we got through our field visit were quite different than we were informed, On day 1 We met with the farmer family whose well was dug on high water-table. So we found that the well was dug max 5 ft. and the boring done was similar to the informed measurement of 30 ft. We interacted with the farmer regarding our curiosity about any kind of gas release in this situation of small well but we were happy to know that he doesn’t face such horrifying conditions of gas release.
He thoroughly explained us the entire process of the farming right from digging to the shipment of the salt to the factory. He told that his underground water has a minimal salt concentration of 10% so he has to perform the evaporation process for concentrating the water above 25% several times compared to the farmers who are having comparatively richer concentration of brine water. This 25% concentration quantity was informed to us by the farmer himself for the initial nucleation of the salt crystals, he even showed us the pre and post salt condition of farming. In the pre-condition huge crack has been observed which is thoroughly moistened with water and furrowed and ploughed using tractor and then filled with brine water for post conditions. He also mentioned that he ploughs the brine field land with his leg to provide the bed for salt formation which also hampers his feet condition. Though the boots have been provided by the government but it hurts his legs causing sores. The female farmers tug their sarees in the boots but it only worsens the conditions. After this interrogation regarding the power supply was done in which we got to know about two sources. The first source used during day time is solar powered silicon panels having the capacity of 300 WP and such 9 panels /equivalent to 2700 WP are used. The farmer mentioned that approximately 1 HP is required for each well thereby satisfying his requirements of 3 wells by solar power successfully. A tank of fresh water is provided monthly by the government for cleaning of solar panels. During the night time the motor is powered by DC generator having the tank capacity of 7 L and power capacity of approximately 3.5 HP The team even visited their jute sack made hut in the deserted land to know about their livelihood during their course of occupation which last for 8 months. We found that the wall made of sack is not capable enough to prevent heat transmission to take place inside the house from outside. The kitchen condition too was not good; lacking facilities like chimneys for smoke escape and lack of ‘Chula’ for proper cooking mechanism.
Day 2 (Morning)
Salt farming on low water table was explored on the next day, the first thing we noticed was the walls of the well and its depth and the mechanism they were using to dig those wells and to come out of the wells. We found that some of the wells had cemented walls in order to avoid any chance of collapse being 20 Ft deep. The farmer informed us that the collapse of well takes place while digging and re-digging of the well for usage. Well collapse also account for the dead of farmers in the kutch. On further, interaction with the farmer we got to know the entire process of motor fitting, boring and well connections. In order to increase the efficiency of the motor it is placed at the bottom of the well; regular maintenance of motor is required, for that purpose a manual labor is required which possess the risk of exposure to the toxic gas if present in the initial 2-3 months of the salt farmer.
The one end of the pipe connected to the motor goes deep into the boring pipe which is 30ft down below the well and the other end of the motor pipe is above the ground to pump the water out. If the water table is below 50ft then that well is not used as it decreases the motor efficiency. A special kind of pipe is used for boring process which has spare like base which is used to dig. This tool is rotated and at the same pushed downwards to displace the soil and create a vertical hole; the length of the tool is flexible with the initial base having a length of 10ft on which another pipe of 20ft is mounted to get a bore depth of 30ft. After this process of boring, a pipe of adult palm diameter is fitted into the hole. If the water table is critically low than 2 or 3 wells are connected through an underground channel, in this manner the motor gets water equivalent to fully charged well. The underground pipes of three wells are brought to a junction where the motor is placed to pump the water out. We observed too much sparrows over their and asked about the presence. He told that the sparrows are used as a tool to detect the presence of toxic gas in the well, currently we are terming this method as a bird method. In bird method a pigeon or a sparrow is dropped into the well and if it dies within minutes, it signifies the presence of gas. He also described about his second best method in which there is no wild life harm; fire torch method. In fire torch method a fire torch is hang down into the boring pipe and if it blows off, it signifies the toxic gas. We inquired about his property loss during the monsoon time and here property includes the temporary stay they build during the 8 months livelihood. We got to know that the stay/hut gets washed away but the bamboo buried to know the position of the well stays firm.
Day 2 (Afternoon)
after the salt farm visit we were curious to know the ending manufacturing process so we visited the salt industry, there we saw huge heap of salt crystals and the remarkable thing about the crystals were that they were almost firm. We observed the entire process from crushing the crystals to getting iodized and packaging. One thing which troubled us that the laborers were not using gloves while ceiling the salt packets using electric conducting rod.
Day 2 (Evening)
We visited the village (kharagoda new) of salt farmer having its history right from British regime. We met those families who lost members due to toxic gas expulsion and understood the entire process of salt farming in details; Inquired about each chance of toxic gas expulsion during the entire process.
From the above observation we concluded that there were two problems that:
A proper ventilation is required in the kitchen which can be powered by wind A valve which can be opened from 20ft.
Field visit 2
After conceptualizing the idea of prototype 1.O we again visited the people of katch to know about user acceptance and any flaws.
After having brief interaction with them regarding the prototype we got to know that the gas problem happens not only during the reopening of the boring pipe but can also take place during their 8 month working period. Their is also a chance that the gas may leak out from the soil present around the boring pipe but the amount released is quite bearable still we advised the locals to sprinkle sodium carbonate on the soil. Now we had a second challenge in which we have to solve the gas problem while the water is pumping out of the boring well i.e we have to come up with the second version of our prototype which will allow water pumping but inhibit gas release.
Field visit 1
Having a talk with the people of kutch , we got to know that they want no gas should come out of the boring pipe or atleast during their working duration. So we came up with a design in which their will be a lid(lower) surrounded by a rubber rim to hinder any type of gas leakage from the circumferential part of the pipe. The lower lid will be provided with a slight transnational motion in the vertical direction with the help of a nozzle mounted on the upper lid. A pulley will also be mounted on the upper lid which will be connected to the nozzle using a nylon rope. Pulley will be having a slag thread of 20ft after which any further pulling of thread will offer force on the nozzle thus forcing it to open; simultaneously the lower lid will move downwards thus freeing the rim from the inner surface of the pipe.
Instead of detecting the harmful gases we focused more on diminishing it. So a container containing sodium carbonate will be attached to the lower base of lid (lower). the container will be having circular holes near the neck for the gas to react with the sodium carbonate. Basically here we will be using Le ch-atelier principle in which the washing soda present in vapour phase consume by the reaction will drive the conversion of solid sodium carbonate to vapor phase; producing NAHS in liquid form with carbon monoxide and sulfur dioxide. Both carbon monoxide and sulfur dioxide require very high concentration and time duration to have any effect on human being. the amount of these gases produced during the reaction are comparatively very low for any harmful effects. So we can ignore their presence.
This model is quite similar to prototype 1.O in functioning having certain modifications. These modifications opening for water pipe , change in nozzle size, change in location of pulley and incorporation of pole for liver purpose. The lower lid also has been changed to suit the requirement for the opening of water pipe thus changing its shape from circular to crescent moon. Everything rest for the container and reaction remains the same.
Fig-1.1 Pulley on which thread will be rolled off
Fig-1.2 Lower Part of Valve.
Fig-1.3 Locking mechanism of Valve (lower lid)
Fig-1.4 Upper Part of Valve
Fig-1.5 Nozzle Opener
Detection and Prevention of Toxic Gas Accidents in Salt Wells of Kutch Region
By: Ratan, Neelanjana, Shreyasvi and Ayush
Every year salt farmers in the Kutch region dig wells to extract brine water which they evaporate to extract salt. The process of well digging is that they first dig a well of depth around 10-15 feet. Looking at the texture and the moisture of the soil they judge the presence of water. If there is a possibility of presence of water they further bore into the ground to reach the water table. During the processes of boring or extracting brine water, gases produced due to anaerobic respiration such as hydrogen sulfide, carbon monoxide and methane are released with a lot of pressure. The farmers inside the well generally cannot detect the presence of these gases and could come out. However the ejection of these gases causes drop in oxygen concentration. Gases like carbon monoxide and hydrogen sulfide further combine with our hemoglobin and reduce the oxygen carrying capacity of our blood. The farmers suffer from asphyxiation and many times lose their lives. The problem was the detection of these gases and device a mechanism which would help the farmers in these situations. As can be understood this issue is serious and needs to be addressed immediately. Every year many farmers succumb to these gases leaving behind their widowed wives and children in eternal pain. Very few farmers are lucky enough to face the gas attack and still see the sunrise of the next day and those who do survive have no idea of what happened to them except the faint remembrance of dizziness and then complete darkness.
The team left for the Rann in the morning at around 4 o'clock. The journey took around 6 hours and by 10 we reached Kharaghoda which is a part of the Little Rann of Kutch. There we were received by Ambu Bhai, a local. His father was a salt farmer and he had done some salt farming in his childhood, due to which he was an asset for our enquiry. He told many things about the Rann, It is a barren land of salty mud which stretches over the area of about 5000 square kilometre. There is almost no vegetation there because of the high concentration of salt in the soil.
After the monsoons, from the month of October, the salt farmers dig wells there in order to get the salty water which is used by them in the extraction of salt. This was an issue since there was no salt farming during our visit, benefiting us of having a hand on experience of salt farming. The depth of the well varies from a couple of feet to around 15 feet. Steps were made in the well by digging out mud for going in and out the well. After that they bore deeper to around 60 feet to get the brine water, which then goes through a number of processes before the salt is obtained. When we asked Ambu bhai about how do the salt farmers determine the best where they should dig, he told us that there is no logic behind it and that it was like a ‘lucky draw’. Thus many times the farmers dig a well to find no water inside it.
During the processes of digging and boring toxic gases are released. The farmers working inside the well suddenly become dizzy and unconscious due to which they are unable to escape timely. This results in the death of many salt farmers every year. Again, the depths when the gases would evolve and their toxicity is uncertain, making it difficult for the farmers of predicts the event and use the necessary precautions. Ambu Bhai also told us about a certain Ganpat Bhai who was a victim of the exposure to these toxic gases. He was provided with timely medical assistance due to which he survived. We decided to visit the village where the Agarias live to know more about these toxic gases and know about the experience of Ganpat bhai, which could be very helpful in our quest. There we saw some wells dug which were not in use at that time and then we went to stay at the guest house of Gantar, an NGO committed to the education of the children of Agarias and other such issues.
The Mighty Kutch
We were greeted by around 10-15 Agarias when we visited their village. Ganpat Bhai was not there when we reached but he soon joined. The information which we get there was very useful.They told us that it was their experience that when a well is freshly dug and bored, there are no cases of toxic gases. But when they come to the well the next year and remove the cloth from the mouth of the pipe, there is a rapid evolution of toxic gases. In order to detect the gas the farmers lower a lighted stick into the well. If the stick extinguishes, then there is presence of toxic gases. They tie ropes around the waist of the person going into the well so that he can be pulled out in case toxic gases start coming out. But these precautions are seldom observed by the farmers and they do such practices only after some such events have already occurred. Then we learnt what happened to Ganpat Bhai He told us that when he was inside the well he suddenly started feeling dizzy and become unconscious after sometime, due to which he was unable to speak and ask for help. The farmers outside the well had a hard time saving him. Since he was not tied to any rope, the farmers sent a person in the well to tie rope around his waist. But as soon as this person reached the bottom he also became unconscious. He was brought out immediately till he regained his consciousness after which he was again sent down. Finally they were able to bring Ganpat bhai out of the well. This happened three times due to which the rescue operation took around one and a half hour. Finally they were able to bring Ganpat bhai out of the well. He was immediately rushed to a hospital in the nearby city where he was treated and given oxygen. The timely help provided helped him in regaining his consciousness. He told us that he did not feel any odour of the gas when he was inside the well.
A typical Dug cum Bore well in Kutch region
Based on the descriptions provided by the farmers we came to know that the gas was extremely toxic, it was odourless and did not support combustion because a lighted stick thrown in the well was observed to be extinguished. Carbon monoxide was the prime contender of being this mysterious toxic gas. We also suspected the presence of hydrocarbons like methane because they are odorless and are found at places like these.
The next day we again went to the field with the aim to get some samples of the well water and know more about the gases that come out of these wells. We met Veer Singh, an Agaria, who agreed to help us. He took us to his well which was quite shallow compared to the wells we had seen the day earlier. He removed the cloth which was used to cover the pipe bored into the ground. As soon as the cloth was removed we smelt the unmistakable foul smell of hydrogen sulphide. This was a surprise since we were earlier told that the gas was odorless . We took the samples of the soil on the outer surface as well as from the depth of around 2 feet. We also took the water from the well in a bottle which contained the dissolved hydrogen sulphide. We then went to the village dispensary to gain some insight into the effects of the gas. The doctor told us that the main diseases prevalent among the salt farmers are asthma, hypertension. He also told us that many people have come to the village in the past with similar questions but no steps have ever been taken.
We then visited the residence of Ganpat bhai and asked him to smell the gases coming from the water collected in the bottle. Surprisingly he said that he could not smell anything even though we could clearly smell the foul odor. This showed that due to exposure over a long period of time these farmers have become accustomed to the smell of the gases. It was an unexpected observation which led us to conclude that the major gas present in the well is hydrogen sulfide but the farmers could not detect it because they have become accustomed to the foul odor of this gas. Meanwhile we took the water sample and from the well with the hope that chemical analysis of the sample would give us information about the other gases present inside the wells along with their concentrations. However when we reached the lab we found that all there were no gases present which made us conclude that the gases, if present, have already escaped the water in the bottle.
After returning we embarked upon the path of finding a way for detection of gases. From the information we gained from the field we knew that the gases present in the well were toxic. We were confirmed that hydrogen sulfide was present along with the possibility of carbon monoxide and hydrocarbons. We needed to know more about the properties of the gases and how can we devise methods to detect.
For having a better understanding of the toxic gases we went to Gujarat Forensic Science University. There we had a meeting with Mr. Mohinder Singh Dahia, Director of GFSU. We told him about the situation and sought his advice. He proved to be a very cooperative person. He first and explained us the process through which these gases are formed underground. He also told us that similar gases are formed in the gutters and affect the sewage workers. We told about the gases that we suspect to be present in the well, to which he agreed, with strong emphasis on the presence of carbon monoxide. For the detection of hydrogen sulfide he suggested that we can use a chemical based approach and find some chemical that gives a positive test for hydrogen sulfide. He further suggested that we can make paper strips of the chemicals and use them on the site for the detection of the gases.
We asked him if he can provide us with a source hydrogen sulfide to perform the chemical tests and know about its chemical properties, to which he smilingly refused saying that they do not perform tests on gases in the forensic lab. On the same day Professor Amit Sheth, HOD of the Department of Design at the Nirma University visited the summer school. We asked him about the design that our prototype should have to cater to the need at hand. Currently the farmers cover the opening of the bore pipe with a cloth at the end of the farming season, which they remove when they come to extract the brine water the next year. Now what happens is that the toxic gases, formed as a result of anaerobic respiration, get accumulated in the pipe. When the farmers remove the cloth these gases come out with a lot of pressure and knocks down the farmers at times.
Lid for the bore with a slider
The problem we presented before him was how could we detect the presence of gases trapped in the pipe without removing the cloth. He gave some very good solutions for this problem. He suggested that we could use a mechanism similar to that used in the talcum powders, where there is a cover with a sliding lid. The cover has holes on half of the surface while other half is covered. The slider can be moved on the holed surface to prevent the escape of powder from the container. He also suggested that we use an injection to lower the chemical or the sensor inside the hole without removing the cloth so that the gas is detected without causing any harm to the person. We liked the cover idea very much and decided to go further with it.
We had a Skype session with Mr. Sanjay Sharma, associate professor in Mechanical Department . He agreed with our observations during the field visit and also provided us with a very important insight. He told us that hydrogen sulphide has a very foul smell of rotten eggs. But if the gas is in a high concentration, it affects our olfactory system and weakens our smell of sense. Then we recalled a detail we missed during the field visit. When the farmer removed the cloth from the well and the gases were ejected, we immediately smelt the foul smell of hydrogen sulfide. But the farmer who was with us did not smell the gas. Back at that time we ignored this but on getting this detail, the incident was justified.
Next we talked to Ted Moellam, who has been a fellow student at MIT. We told him about the problem and our approaches towards solving it. He was very excited with our findings and our approaches. We showed him the sensor based project that we had built till that time built on arduous uno. He suggested us to make the project as cost effective as possible because the economic conditions of the farmers is not very good. He advised us to use arduino nano which is cheaper and smaller than uno. We found his advice to be useful and decided to implement it. So we start working to replace uno with nano in our project.
Development of Prototype
The suggestions provided by the mentors helped us with our further approach towards the problem. We worked upon the suggestions of Mr. Dahia and did a study on the properties of hydrogen sulphide to know about its chemical and physical properties. We found that the gas gives the colorless solution of lead acetate brown. This could be used for the detection of the gas. So we prepared paper strips dipped in the solution of lead acetate. For making hydrogen sulphide, we used Kipps apparatus in which ferrous sulphide was reacted with concentrated hydrochloric acid to yield hydrogen sulphide. The test was successful, so we decided to go forward with it. There was however one problem with this. The water used in this region is very salty and contains a lot of chloride ions. When we made lead acetate solution, a lot of salt precipitated as white lead chloride. This reduces the solubility and hence the concentration of the solution. For this we began searching for a chemical that is cheap, does not precipitate in the presence of chloride ions and gives a change in color in the presence of hydrogen sulphide and should be easily available. The compound which fulfilled all these criteria was found to be hydrated copper sulphate, commonly called as blue vitriol. It changes its color from blue to black in the presence of hydrogen sulphide, it dissolves in the presence of chloride ions, is commercially available and completely affordable. So we prepared the strips of copper sulphate of one molar concentration. The strips showed excellent colour change in the presence of hydrogen sulphide. The reaction was possible even when the strips were completely dry, because the gas produced was moist.
During the preliminary phase of development of the project, the major question was the type of gas that was found in the area as it wasn’t clear even from the visit of the local medical centre about the details of the gas. Therefore, for the preliminary part of the research, we made a device consisting of several different types of gas sensors that were quite specific to one aspect of the mixture of the gas. Among all of these, we had our suspicions over the gas of H2S (hydrogen sulphide) and Carbon monoxide due to the following reasons.
1. Carbon monoxide was odourless and the gas that was told to us about by the people was also said to be odourless.
2. Hydrogen Sulphide though wasn’t odourless and has a distinct rotten egg smell, in higher concentration tends to cause loosening of the sense of smelling to the people that are being affected by it making it seem like it’s an odorless gas.
In order to find out the right gas, we tested two gas sensors, MQ135 and MQ7 which were quite particular in finding out specifically the gas that was present in the gas wells. Apart from just moving forward on this project from the electronics aspect we were also taking into consideration the possibility of using a chemical sensor in order to carry out the diagnose. Therefore, we prepared another chemical based sensor in order to detect gas specifically designed for H2S.
For the preparation of the electronics module for finding out the specific gas that was present in the well, we used an Arduino Uno Board with a small buzzer that would only beep if the concentration of the gas is present above a particular value that was calibrated after going to the site of the wells.
Furthermore, for the preparation of the chemical based sensor, we used lead acetate strips that were found to react with hydrogen sulphide gas in order to give a black precipitate. The same reaction used to turn the strips black due to the reaction. However, as it wasn’t enough to know whether that concentration of the gas is harmful or not, we installed a photo-diode and a compactor circuit which basically used to convert the amount of reaction that has been carried out in between the strip and the gas present. The calibration of the same can be done by simple adjusting the value at which the sensor should activate the buzzer to beep.
Testing of the prototypes (Gas Detection):
After both of the prototypes were made, they were taken to the site in order to find out the toxic gas that was present. Initial testing related to the prototype was done by preparing H2S using Kipp’s Apparatus in lab where the MQ135 sensor showed higher analog signal value (around 800 compared to its normal value, around 200) with the analog signal value from the MQ7 being almost the same with not much increase (around 300, compared to its normal value, around 200). Once, the preliminary testing was done, while carrying out the same in the field, the prototype showed a significant increase in the analog signal value for the MQ7 sensor (around 500-600, compared to its normal value, 200), with the other sensor MQ135 not showing any significant increase (around 300, compared to its normal value of around 200). As a result it was found that there is a presence of a mixture of gases there with a major percentage of it being Carbon Monoxide along with presence of H2S.
We showed our prototypes to Mr. Veer Singh, an Agaria, who was the owner of the wells and accompanied us to the wells. He was very glad when the solutions to the problems that he has been seeing around him for years. He said that the prototypes are good and he could use them if they are affordable. We asked him the expected price for the sensors. He gave a range of 500-1000 INR which was much greater than the price at which we intended to market the products, which was in the range of 200-300 INR. He also praised the lid that we had made and said that it is better than the cloth that they use or covering the bore. We could not get reviews from any other farmer because it was an off season when we visited the field and there was no farming going on. Nevertheless the reviews we got from Veer Singh were inspiring and encouraged us to improve our design.
Demonstrating the prototypes to farmers
Being a part of the system that targets to improve the quality of life of salt farmers gives ussatisfaction, both socially as well as morally because: "हमने कच्छ का नमक खाया है"
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 sewage 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 firsthand 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 mud. 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.