Water Purification in Thailand

Transcription

1 Water Purification in Thailand Isabel Henderson Cori Rose Schroer Rebecca Jung July 23, 2010 Meghan Duggan Abstract Water is a necessary part of life, but without proper filtration, it could cause problems such as illness or death. While citizens of developed countries may take the water that flows from their taps for granted, many parts of the world do not have access to clean water. A small village in Thailand called Nong Bua is one such community that is hindered by the quality of their water supply. Nong Bua has a water filtration and distribution system, but this treatment process is doing more harm than good. The drinking water in Nong Bua is contaminated with a myriad of harmful substances including coliform bacteria, manganese, and iron. With these problems in mind, our group used creative engineering in order to build a water filtration system for Nong Bua. While we could not acquire water from Nong Bua for testing, we used water from the local Raritan River instead. The tests that we conducted on this water found bacteria as a contaminant. The system we built to address these problems is made up of a system of filters and chlorinators used to kill bacteria in the water. The water will be pumped through a sand filter, which is used to trap small particles and remaining bacteria. The water also goes through a mechanical particle filtration system. Finally, the water passes through an activated carbon filter that will remove large heavy metal particles, and remove the unpleasant taste of chlorine that deterred the Thai people from drinking the water. Our filter worked in removing contaminants from the Raritan River water. To improve our design, we could add lids to each component of the system to ensure that no external sources could pollute it further. We could also improve the quality of the caulking on our particle separator to make it more stable against higher water pressures. 1 Introduction Water, covering approximately 70 percent of the Earth s surface, is one of the most vital supplies for all forms of life. While it may seem abundant, drinkable water is actually considered to be very scarce in many areas around the world. A lack of consumable water has been a problem for many people, including the villagers of Nong Bua. In the 1990s, the government installed wells and a filtration system in the village. However, community members were not taught how to properly maintain the current system, which is not successful at removing contaminants found in the well water. The water has not been tested by the government, nor the system inspected, since it was constructed. This has led to water coming out of the filtration system even more polluted than when it went in. Due to the poor water quality of the water coming out of the original system, the villagers are forced to buy expensive bottled water for drinking and cooking. They only use water from the well to wash their clothes and bathe. [?] Based on the deteriorating status of the original system in Nong Bua, we decided to replace it with a more effective one. The most important factors that we considered in our design process were affordability and manageability. We collaborated with Engineers Without Borders, and used their expertise on the situation in Nong Bua to create a filtration system to replace the government implemented system. 2 Background: The Situation in Thailand 2.1 Why Nong Bua? Engineers Without Borders originally chose to focus on Nong Bua, Thailand for its unique situation. The problem in Thailand is not a lack of water, but rather a problem acquiring clean water. Pollu- 1

2 tion levels have become unsafe in Thailand due to a rapid growth in population, as well as industrial expansion. This has led to the pollution of Thailands waterways and surface water bodies, about one-third of which are of poor quality. As the population continues to grow rapidly, the water problem is exacerbated due to increasing demand. These problems are clearly seen in Nong Bua. As a small farming community located in northern Thailand with a population of 481 people making up 143 households. Its climate is tropical and warm, with a rainy season from June to October and a dry season for the rest of the year. While the villagers have access to running water that is pumped from the ground, this is not safe for drinking. A filtration system is necessary before the villagers can use the water. In Nong Bua, the average income per household is about $1,270 per year (40,000 Baht). Their low income makes the community s current reliance on expensive bottled water a significant financial burden. By eliminating the need to buy bottled water, a water filtration system would provide a significant benefit to the community- in both their economy and quality of life. 2.2 Current Filtration System The saga of water filtration in Nong Bua began In the 1990s, when the government installed wells in the village. The current water filtration system in Thailand starts with a well that reaches 88 meters deep. From here, the water is pumped to an aeration unit, which exposes contaminants and other chemicals found in the water source, by exposing the water to oxygen. As the water cascades down the unit, the increased levels of oxygen precipitates out the chemicals in the water. The precipitate is caught by a sifter while the water continues through the system. Next, the water seeps through a multimedia filter made of porous bags filled with an alternation of large rocks, gravel and sand. The multimedia filter is supposed to filter out any sediment. From the filter, the water is stored in holding tanks. Once in the holding tanks, the water is distributed throughout Nong Bua. While the filtration process in itself is not flawed, the government has failed to follow up on their installation with testing or maintenance. The water turns the villagers clothing yellow due to the high concentration of iron in the water, and they refuse to use it for drinking or cooking. Within this process, the multimedia filter, the aeration unit, and the holding tanks all posed problems which make the system unsuccessful. For instance, the multimedia filter needs to be replaced. Instead of filtering out bacteria and particles, the pores of the bags have become clogged, and the Figure 1: The current aeration filter in Nong Bua. Figure 2: A sketch of the water filtration system. sediment that gathers on the outside of the bags is carried through the system by the water that passes through. In addition, the lack of a covering on the aeration unit has led to animals drinking from it. The unit is contaminated with chicken fecal matter, which dangerously increases the amount of coliforms in the drinking water. Another design flaw is that the holding tanks drain from the bottom of the tank, where sediment mixes with the water, rather than the top, which holds clearer water. 2.3 A Lack of Maintenance The most evident problem in the water system in Nong Bua is a lack of maintenance. Due to lack of attention, silt and contaminants have built up inside the pipes, significantly decreasing their diameter. This has increased the pressure at which the water flowed through the pipes, and caused them to burst. Also, while many people within the town avoid drinking the contaminated water, there are still some reports of cold, flu, stomachache and giardia, an infection of the small intestine caused by 2

3 Figure 3: Due to a lack of maintenance, the water coming out of the filtration system is actually dirtier than the water going in. contaminants. Our test results were for pesticides and lead. We found safe amounts of nitrates, nitrites, iron, copper, chlorine, and arsenic. We also found that the water was slightly alkaline, at 80 ppm, but still within safe levels. The ph was slightly high at 9.5. However, the focus of our design was determined when the test for bacteria came back positive. While the Raritan water sample did not test positive for iron or manganese, as the water from Nong Bua did, it contained bacteria, which was also present in the water from Thailand. These results led us to focus our efforts on reducing the levels of bacteria in the water. Test results Nitrates Nitrites Total Alkalinity Total Hardness Iron Copper Chlorine Arsenic Bacteria positive Atrazine Pesticide Simazine Pesticide Lead ph Apparatus Design Figure 4: The iron test, which came out. organisms. These illnesses may be due to the contaminants in the water and the faulty filtration system in place. 3 Creating and Maintaining a Functional Filtration System 3.1 Testing of Local Water The first step we took in our design process was testing water from the Raritan River in New Brunswick, New Jersey. Given the difficulty of testing the water in Thailand ourselves, we used these local samples to find parallels with data from Thailand to analyze. We used a simple water testing kit that is available at home improvement stores to find We researched designs for our filtration system and decided on filtration apparatus that included a slow gravity sand filter, carbon filter, and a simple mechanical particle separation tank. The water was treated with chlorine bleach, for disinfection, when it reached the carbon filter. We did this by inserting a funnel in the top of the lid of the carbon filter. The carbon filter removed the chlorine taste, as well as organic contaminants like bacteria, from the water. In addition to our purification goals, we kept in mind the mission of Engineers Without Borders. They work to improve the quality of life for communities abroad, rather than simply acting as a charity that gives aid. With this mission in mind, we created a filter that would be sustainable and manageable for the villagers of Nong Bua. We also used inexpensive items for our apparatus to make sure that people in Thailand would have access to these materials. 3.3 Initial Construction After finalizing our design, we began construction. We used two five-gallon buckets for the sand and carbon filters. We used plastic tubing to attach the 3

4 Figure 5: A sketch of our initial design. Figure 7: The sand filter. gressed from fine sand to coarser sand, particles of various sizes were filtered out. The bottom of the sand filter consisted of pebbles and larger stones. We used a screen and chicken wire to hold the sand filter up. These screens had the additional benefit of eliminating particles that remained in the water. The sand filter led to a funnel where the clean water from the filter flowed out. It then entered PVC tubing to the carbon filter. Through the top of the carbon filter, we added 0.5 ml of chlorine bleach per gallon of untreated water after referencing the Environmental Protection Agency. This addition of chlorine disinfected the water and killed bacteria. The water then traveled through the carbon filter, where a layer of cotton and activated carbon was used to remove heavy metals and any bad tastes or odors from the chlorine?? The water then traveled to the particle filter, where water flowing through the tank rose to the top, and larger particles settled to the bottom. Any particles that escaped from the sand filter dropped down to the bottom of the tank. The clean water then rose over the plastic wall we constructed in the tank, and flowed out of another hole in the tank through more PVC tubing. The purified water then flows out the final PVC tube, and can be used for household purposes and as drinking water. Figure 6: Meghan caulking the plastic wall in the particle separator. filters and a plastic tub for the mechanical particle separator. We used sturdy plastic for the wall inside the particle separator and made it watertight so that the clean water must pass directly over the wall and the dirty particles stay at the bottom of the filter. To treat the water, we used household bleach and water to chlorinate the water. The sand filter is made of fine sand and larger particle sand as well as small pebbles and stone. The carbon filter consists of cotton and activated carbon from wood charcoal. Other items include the mesh screens and chicken wire above and below each filter. We placed the entire system on a wooden support shelf by attaching the handles of the sand and carbon filters to the wood with metal hooks and washers. 3.4 Water Flow Through the System 3.5 When the water flowed through the sand filter, it reached the top layer, known as the schmutzdecke. This is a layer of beneficial bacterial that traps dangerous bacteria and viruses. Water then moved down through fine particle sand. As the water pro- Removing Chlorine Taste While chlorine is beneficial for its ability to disinfect, it leaves the water with a taste that many people find unpleasant. To counter this, we decided to use an activated carbon filter, which reacts with the chlorine and removes it both physically and chem4

5 ically. The surface oxides of the activated carbon change the chemical structure of the chlorine. The surface of the activated carbon then attracts the chlorine, and a reduction-oxidation reaction occurs [?], as seen in equation??. 3.6 N H2 Cl + H2 O + GAC > N H3 + HCl (1) 2N H2 Cl + GAC > N2 + 2HCl + H2 O (2) Problems in Constructing the Particle Filter While our final design placed the particle separator at the end of the system, our first design set up the particle separator between the sand and carbon filters. However, when we attempted to construct the system in this order, the size of the particle separator made it difficult to fit within the wooden support shelf. Also, placing the particle separator between the sand and carbon filters would require very sharp angles of piping between these components, which would place excess pressure on their caulked connections. This pressure could cause leaks or breakage. In our first tests of the system, the plastic wall that we caulked in the middle of the particle separator began to bend from the pressure of the water behind it. We addressed this by using a soldering iron to create a hole approximately twelve centimeters from the bottom of the wall. These factors led to our decision to place the particle filter at the end of the system. We also attempted to remedy the problem of the oversized particle separator by trying to replace it with a milk jug. We tried to Figure 8: The system with the milk jug particle separado this by inserting PVC tubing at the bottom of tor, which we later took it out of our design. an empty gallon jug of milk, and cut a hole in the handle to allow water to flow out and onward to the carbon filter. This design seemed successful on paper, but in practice it was flawed. The high density polyethylene that made up the milk jug was not compatible with the caulk that we used to attach it to the PVC tubing. Its sturdiness in general was not up to the standards of the other components of the filter, and when considered its performance in a tropical outdoor environment, we decided to eliminate it from our design and revert to the original particle separator. 3.7 Maintaining the System The system is designed so that it can be easily maintained. For example, the schmutzdecke, the Figure 9: The funnel, which was used to insert chlorine top layer of sand, must be scraped off and replaced bleach. when the bacteria has built up to unsafe levels, or 5

6 Figure 11: The untreated water, on the left, compared with treated water on the right. around 2.5 centimeters in height. The villagers can easily be taught how to remove the sand. Another factor in maintenance is the carbon filter, which will have to be replaced every 12 months. In addition, the whole system should be backwashed to remove any particles that remain stuck in the apparatus. The amount of time before replacement will depend on how much water and sediment go through the system. However, basic maintenance should be manageable and easy, as the parts of our filter are removable and accessible in the event that they need to be replaced. 4 Results and Discussion After designing, constructing and testing a new filtration system for the people of Nong Bua, our results indicated that it not longer tested positive for bacteria. In comparing the results of our final water test to the second round of testing, we found that the water no longer tested positive for bacteria, which was our main goal. The turbidity test, which compared the untreated and treated water, was indisputably clear. The untreated water, which was rust-colored and filled with particles, shows significant improvement after treatment. Our design was a constantly changing process. We had several problems with our initial implementation of the particle separator. We worked around this by switching around the placement of the various components of our filter, and in the end, found a setup that solved these problems. Our inability to test the water in Thailand presented one of the most interesting challenges of our design. Although we Figure 10: The final system at work. 6

7 had a knowledge of the possible contaminants in the water in Thailand, we were not able to test the effectiveness of our filter in removing these contaminants. As far as its status as a prototype, our model could either be made in mass production as a series of smaller filters, or scaled up to produce one large system. The next step in the development of our filter would be to test its effectiveness with water from Nong Bua. Test results Nitrates Nitrites Total Alkalinity Total Hardness Iron Copper Chlorine Arsenic Bacteria Atrazine Pesticide Simazine Pesticide Lead ph 9.5 Beardsley, Chair and Laura Overdeck, Vice Chair). We would also like to thank the sponsors of the 2010 Governor s School, particularly Rugters University, the Rutgers University School of Engineering, Morgan Stanley, the State of New Jersey, Lockheed Martin, PSE&G, the Tomasetta Family, the Provident Bank NJ Foundation, Silver Line Building Products, and the families of Governor s School Alumni. References [1] Emergency Disinfection of Drinking Water. The Environmental Protection Agency. Epa.gov. [2] Phil Adams. Chloramines removal by activated carbon. Water Technology Magazine. Volume 27, Issue 3. March [3] Engineers Without Borders, Rutgers Chapter. Thailand Project. 5 Conclusion In tackling the problem of clean water in Nong Bua, our design for an improved water filtration system can be used effectively due to its low cost, practicality, and ease of use. It employs inexpensive and widely available materials that are effective in their purpose. Although we had several changes and problems with our initial design, predominantly with the particle separator, the ultimate design performed its function successfully. Of course, the water system only has worth if it remains clean and correctly functioning: it requires routine checks and maintenance. While we used our engineering skills to design the filter, it is by no means a charity item; the people of Nong Bua will have to maintain it themselves in order for it to have long-lasting benefits to the community. 6 Acknowledgments We would like to thank everyone involved in helping us conduct our experiment. These thanks go to Matthew Mauro (our project mentor). Amber Cox and Monal Agrawal (our RTA mentors), Blase E. Ur (GSET Program Coordinator), Ilene Rosen (GSET Program Director), Kristin Frank (Head RTA), Jameslevi Schmidt (Research RTA), and Fedja Buzancic (who helped us collect water and supplies). We would also like to than the Governor s School Board of Overseers (Marguerite 7