Research on the Effectiveness of Using Cloth as a Filter to Remove Turbidity from Water

Research on the Effectiveness of Using Cloth as a Filter to Remove Turbidity from Water Ramya Tammisetti STREAM A, Section G Blue Ms. Padmanabhan February 18, 2010 Table of Contents Abstract 2 Introduction
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Research on the Effectiveness of Using Cloth as a Filter to Remove Turbidity from Water Ramya Tammisetti STREAM A, Section G Blue Ms. Padmanabhan February 18, 2010 Table of Contents Abstract 2 Introduction 3 Literature Review 4 Research Plan 7 Methodology 9 Results/ Data Analysis/ Discussion 10 Conclusions 13 Limitations and Assumptions 14 Applications and Future Experiments 15 Literature Cited 16 Appendices 17 Acknowledgements 32 1 Abstract Water in most developing countries is consumed without filtration, resulting in the consumption of water-borne microbes, silt, and other particulate matter. Water was collected from the pond in Dean Park, Shrewsbury MA to simulate the drinking water in undeveloped countries. The water collected was tested for turbidity and then the filtered through different types of cloth with varying numbers of folds to try to eliminate as much suspended particulate matter as possible. Turbidity was measured after filtration. This method was followed with various other cloths. Applications for this research include helping the people of developing countries; if they start filtering their water, many more people could stay healthy as water-borne pathogens could be eliminated through this simple filtering strategy. A manual has been produced for translation and distribution in developing countries. 2 Introduction The purpose of this research project is to test the effectiveness of different cloths in filtering out turbidity. Turbidity is the measure of how cloudy the water is; a higher turbidity means cloudier water. The cloudiness can be a result of suspended particles, bacteria, or air bubbles. Cotton, silk, polyester, nylon, burlap, cellulose, woven plastic, and straw will each be tested; each cloth will be folded a different number of times to see how many folds will decrease the measure of turbidity the most. As more folds of cloth for the water to pass through will slow the filtration process down, the goal is to find the ideal number of folds; the number of folds that will decrease the turbidity measurement the most without slowing down the filtration process too much. This is important so that the larger particles that could be harmful are removed from the water prior to consuming. The cloths will be tested to see what to level of turbidity they can reduce the water. These simple filters must also be commercially available because this research will affect developing countries the most. If people in developing countries who rely on rivers as their main source of water can obtain and use a piece of cloth to filter their water before they drink it, fewer people might get sick because previous research showed that 99% of bacteria was eliminated from river water by filtering it through a cotton cloth folded four times. Also, the water they drink will look much more pleasant. 3 What is Turbidity? Turbidity is the measure of the scattering of light due to suspended particles in the water. Cloudy water is called turbid water. The cloudier the water is, the more turbid it is. Things that cause turbidity comprise anything that obstructs the passage of light through the water. Therefore, turbidity can be caused by dirt, organic matter, and also by microscopic organisms. ( General Information on Turbidity, n.d., Turbidity Section, para. 1-2) Turbidity is more concerning to human perception than to sanitation. Water can be completely safe to drink, but it might look unpleasant because it has a high turbidity (L. Soracco, personal communication). While a low level of turbidity is not a major concern in the filtration of water, a high level of turbidity can cause problems with disinfection as it provides suitable conditions for thriving microbes. From this, turbidity levels can point toward the presence of microbes. ( General Information on Turbidity, n.d., Turbidity Section, para. 1-2) What Affects Turbidity? Turbidity tends to have more of an effect in third-world and developing countries, especially in the villages there. Water for the villages is usually gathered straight from the stream or river flowing through the community. One factor that affects turbidity is flow rate. As a river flows, it picks up sediment from the river bottom, which increases the turbidity measurement. Other factors that increase turbidity include storms. Rainwater from storms can carry eroded soil to water sources, as well as carry debris from cities. Receding flood waters can also transport particles from the land surface to the water source, increasing the turbidity. Another factor is wastewater, which can flow from homes into the river also carting along additional turbidity; even if most of it is removed at a waste treatment plant beforehand, not everything can be eliminated. Decomposing dead animals and plants near the water source release organic particles which increase the turbidity levels of the water. Algae forms when nutrients from the bottom of the water source are released. Nutrients are usually released during changes in season and can also occur with changes in the water current. Algae in the water can greatly increase the turbidity measurement. ( General Information on Turbidity, n.d., Soil Erosion Section, Urban Runoff Section, Wastewater and Septic System Treatment Section, Decaying Plants and Animals Section, Algal Blooms Section, Flooding Section, para. 7-13) Furthermore, some companies get rid of their garbage by dumping it in the nearest water source. This litter could be oil, dirty water, or actual waste. These factors are more common in developing villages than in cities because sanitation is more enforced in cities. The Effects of Turbidity On Water and Underwater Life There are many reasons to eradicate turbidity. The effects that a high turbidity has on the water comprise aftereffects of having less oxygen in the water. Turbidity has adverse effects on underwater life and on the water itself. High turbidity means more particles in the water, and particles absorb more heat, so the water becomes warmer. As water heats, it releases some of it dissolved oxygen (DO). Oxygen dissolves better in cold water. Furthermore, with a high 4 turbidity, not enough light reaches the plants underwater, slowing down the process of photosynthesis, and releasing even more DO. Also, the suspended particles responsible for the high turbidity can block fish gills, which reduces their resistance to disease. This in turn affects the growth rates, reducing them, as well as having an effect on egg and larval development, as settling particles can blanket fish eggs and invertebrates that live on the floor of the water source. ( Monitoring and Assessing Water Quality, 2006, What is turbidity and why is it important? Section, para. 2). This affects people who rely on the river to give them food. Figure 1. The effects of turbidity on fish populations over NTU levels increase, fish populations are affected in a variety of ways, ranging from stress and behavioral changes to delayed hatching rates and death. ( Turbidity--Why is it Important? Section, 2008) The Effects of Turbidity on Drinking Water Moreover, turbidity can affect people when they drink water with suspended particles. Although turbidity is more concerning to human perception than to sanitation, turbid water can have negative effects post drinking because people may have ingested bacteria that could include pathogens. High levels of turbidity can cause problems with disinfection as it provides suitable conditions for bacteria and is very dangerous to the consumer. ( General Information on Turbidity, n.d., Turbidity Section, para. 1-2) 5 Turbidity Measurements The standards set by the U.S. Environmental Protection Agency (EPA) Surface Water Treatment Rule declares that the turbidity of potable water is supposed to be under 5 Nephelometric Turbidity Units and the turbidity of filtered drinking water should not be greater than 1NTU( General Information on Turbidity, n.d., Turbidity Section, para. 1-2). Nephelometric refers to how the turbidimeter measures the scattering of light in the water due to suspended particles. A high NTU reading signifies a higher scattering, which means that the water is more cloudy ( NTU- Nephelometric Turbidity Unit, n.d., para. 1). Turbidity can be measured in many different ways. To get a general turbidity reading for a large body of water, like a lake, a Secchi disk is used. This device is a round, black-and-white disk that has a rope attached to the center of it. It is lowered into the water until the disk can no longer be seen. Measuring the rope will give the depth of the water, and calculations from this point give an estimated turbidity of the lake ( Turbidity How do we measure turbidity? Section, n.d., para ). A Secchi disk is shown below. Figure 2. A Secchi disk. The rope that lowers the disk is attached to the hook in the middle. The design is black and white to provide as much contrast as possible so the disk can be seen at a lower depth than if different colors were used. ( Turbidity How do we measure turbidity? Section, n.d.) For the duration of the experiment, the measurements of turbidity will be taken by a turbidimeter, also known as a nephelometer. It measures turbidity by passing light at a 90 angle through the water and measuring the intensity of the light after it passed through the water sample. ( Turbidity How do we measure turbidity? Section, n.d., para ) Previous Research In a similar research project done for the California State Science Fair in 2003, it was found that cotton is more effective at removing bacteria from water than silk and that silk is more effective than nylon. The tests done in this research project were the oxygen content of the water, the turbidity, and E. coli and coliform bacteria counts. It was found that after filtering the water through the cloths, there was about a 50% reduction in bacteria. ( Silk Sari vs. Cotton Kenta: Water Filtration in Rural Populations Conclusions/Discussion Section, 2003, para. 1) 6 This project was inspired by reports of cholera reduction resulting in India. It was found that communities with lower counts of cholera filtered their drinking water, which came from rivers, through the cloth of the women s saris before drinking it. Cholera bacteria tends to ride on plankton and particles in the water so a cloth that was able to filter out most of the particles would also filter out most of the cholera bacteria. It was found that a sari cloth folded at least four times removed 99% of the cholera bacteria in the water. (Colwell, 2003, pp. 1051) It was found that an old sari cloth worked better than a new cloth because the fibers in the old cloth are looser and more frayed and therefore catch more of the zooplankton that the cholera bacterium attaches itself too. In the pilot study, it was found that the number of cholera cases was reduced by about 38% for filter users, but the group testing this was too small. In the larger study it was found that nylon and sari cloth filters are equally effective as filters. (Colwell, 2003, p ) Research Proposal The purpose of this research project is to find the cloth that reduces turbidity the most when water is filtered through. The goal is to find the ideal number of folds, the number of folds that reduce the turbidity as much as possible without slowing down the filtration process. To start the experimentation, about twenty liters of water for testing will be gathered. Then it will be decided what cloths to use in the test and how many times the cloth should be folded. Before filtering the water, the turbidity measurement in NTUs of the sample of water that will be poured through the filter will be taken and recorded by using the turbidimeter in the WPI Environmental Labs. After filtering, another turbidity reading will be taken and recorded. Comparing the results of the two groups determines if the filter was effective. This process will then be repeated using different cloths and a different number of folds. To prove statistical significance perform a Student t-test would need to be performed. The goal is to find the ideal combination of filtering speed and effectiveness in removing turbidity. Folding the cloth may make it a better filter, but the water would pass through more slowly. The pond in Dean Park, which is located in Shrewsbury, MA will be used as the water source and the first cloth tested will be cotton. Materials Used Four different types of cloth will be tested: cotton, silk, polyester, and burlap. These cloths were chosen based on many factors such as availability, pore size, and expense. A matrix of what cloths will be used and some basic information about all of them was created. The materials were obtained from Joanne s Fabrics. 7 Table 1. Materials Chosen and Rationale Name of Cloth Cotton Polyester Silk Burlap Reasons for Readily available, cheap, Readily available, Readily available, not very Readily available, very choosing this cloth used everywhere cheap, used expensive, used everywhere, cheap, used everywhere Fundamental polymer chemistry --Absorbency and moisture regain 7-8% at standard conditions --thermal properties decomposes at 300 F everywhere Water absorption - equilibrium ( % ) 0.7% --good chemical resistance small pore size --resistant to stretching -- resistant to most mineral acids Pore size Depends microns Less than 100 nanometers Can t find Areas where this cloth is readily available Everywhere, used to make clothes Everywhere, used to make clothes Everywhere, though it is more expensive, used to make clothes Everywhere Average cost $2.18/m $4.36/m $17.49/m $3.27/m Previous research Sari cloth in Bangladesh, the older the cloth, the better the filter Used as allergy pillow covers, tightly woven can Silk is more effective than nylon but less effective than cotton in filtration --Burlap is exceptionally strong, both in tensile strength and tear resistance. -- Burlap stands repeated wetting and drying with minimum loss of strength. Soaking the burlap makes the pore size smaller keep allergens out Availability Stores, labs Stores, labs Stores, labs Stores, labs, manufacturing plants The following sites were used in the designing of the matrix: ( Cotton, n.d.) ( Other Cotton Fabrics, 2009) ( Polyethylene terephthalate polyester ( pet, petp ) properties and applications supplier data by goodfellow, 2003) ( Silk, 2009) (Steinstraesser, L., Trust, G., Rittig, A., Al-Benna, S., Hirsch, T., Steinau, H., & Jacobsen, F. Colistin covered silk membranes against wound infection with pseudomonas aeruginosa. 2009) ( The History of the jute industry. 2009) 8 Methodology The ambient air temperature was taken and recorded from Ten liters of water from Dean Park Pond in Shrewsbury, MA were collected and held in plastic gallon milk cartons. The types of cloth used in the experiment (cotton, silk, polyester, nylon, cellulose, burlap, woven plastic, and straw) were recorded. Thirty milliliters of water was decanted into one of twelve clean, standard, sample cells. The temperature of the water was taken with a thermometer just before testing. The sample cell was cleaned with a KimWipe before the cell was placed in the turbidimeter (Hach brand, 2100AN model). The turbidimeter was turned on and allowed to warm up for fifteen minutes before experimentation began. The sample cell was taken to the turbidimeter and the turbidity reading was taken and recorded. Then each sample of turbid water was filtered through a cloth into a correspondingly labeled clean sample cell. The type and number of times the cloth was folded were recorded. This cell was then cleaned with a KimWipe and placed in the turbidimeter and the results were recorded. All the water samples were passed through different samples of the same cloth folded the same number of times. This process was repeated for all the different types of cloths and the numbers of folds they had. A Student T-test was performed on the data to assess statistical significance. 9 Results/ Data Analysis/ Discussion Each type of cloth folded a certain number of times was tested twelve times so that a student t-test statistical analysis could be performed on the data. The turbidity for each sample was taken before and after filtration and the percent reduction for each trial was calculated. Each cloth was tested with zero folds, one fold, two folds, and three folds. Each time the cloth was folded, the number of layers of cloth that the water had to pass through would double. However, polyester was not tested for all of the number of folds, rather, it was only tested for zero folds, three times. This is because the cloth was not successful at removing turbidity, rather, it added to the turbidity of the water after the filtration process. The relative speed at which the water filtered through was also observed. Each of the trials was noted and graphed. The appendices contain the results for each type of cloth tested. 10 Turbidity Removed (Percent) Cloth Filter and Turbidity Table 2: Summary Table Type of Cloth Number of Folds Average Turbidity Percent Reduction after Filtration Cotton Cotton Cotton Cotton Silk Silk Silk Silk Burlap Burlap Burlap Burlap Polyester 0 (Trial 1) 3.27 N/A Polyester 0 (Trial 2) 2.94 N/A Polyester 0 (Trial 3) 3.18 N/A Cotton Silk Burlap Polyester Number of Folds Figure 3. Average Percent Turbidity Removed. This graph shows the percent of turbidity removed from the water after filtration for each of the cloths. Because polyester was unsuccessful in reducing turbidity, it is always zero. 11 All the cloths, with the exception of polyester, reduced the amount of turbidity in the water. Also, as the number of folds increased, the percent of the turbidity removed increased as well. However, in accordance with that, the rate of filtration decreased because it took longer for the water to filter through so many layers of cloth. Silk, which was the most tightly woven of all the cloths, took the longest to filter through, although it did not provide the best results. That is probably because the cloth let some of the fibers in it to fall into the filtered water. The difference in the percent of turbidity removed between two folds and three folds wasn t that big because more fibers would have the chance to fall into the filtered water when the water was passing through more layers of cloth. Burlap was the quickest cloth to filter through because it had such a big pore size. This showed when water was filtered through only one layer (zero folds) of it, the burlap barley reduced the amount of turbidity in the water. Surprisingly, though, burlap was the most effective filter for water. Cotton was a fairly quick filter for water as well as the second most effective filter. It also let fibers into the water, but it was not nearly as many as the silk did. Polyester took a little longer than cotton to filter through, and it was not a very successful filter at all. The polyester did not remove any turbidity from the water, but added to it. 12 Conclusions Burlap folded over three times (eight layers) was found to be the best filter for removing turbidity. This was surprising because burlap has many loose fibers. However, those fibers must have caught more turbidity than expected. Polyester also behaved unexpectedly. After the water was filtered through the polyester, the turbidity reading increased. It is possible that the loose fibers in the cloth fell into the filtered water, therefore increasing the turbidity reading. A Student t-test was performed on the data collected from cotton, silk, and burlap. They all had over a 99% confidence interval. This means that there is over a 99% chance that, after filtering water through one of these cloths, the turbidity reading will decrease. As increasing the number of folds from two to three did not have a great effect on silk, it is possible that increasing the number of folds could have an adverse effect. This wo
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