Geoffrey James

Preventing Contaminants from Entering Your Body: Engineering in Water Purification

Drinking unclean water has cost millions of lives. Unclean water transmits harmful bacteria, viruses and unwanted chemicals that could be very detrimental to our bodies. This problem has resulted in numerous life-threatening epidemics taking place throughout history. People have attempted to develop water purification systems from as early as the ancient Mesopotamian period, but unseen contaminants continue to cause health problems. These facts drive scientists and engineers to develop more sophisticated ways to purify drinking water.

Introduction

Human beings have many basic physiological needs that must be met to ensure their survival. Without food, humans can survive for more than three weeks. On the other hand, without water, they are only able to survive for at most three days since every living cell inside the human body needs water to keep functioning [1]. Water is fundamental to sustaining humans’ lives, so our water supply needs to be kept hygienic. Drinking dirty water is dangerous because it often carries undesirable chemicals and harmful bacteria that could be damaging to our bodies. Hence, for scientists and engineers, water purification is a field that has limitless areas for improvement because purified water standards always become more stringent as new water related diseases are discovered. Water purification has evolved from a relatively simple process into one of the most complex engineering processes. Today, technology has advanced so much that it is possible to create a more advanced water purification process.

Background of Water Purification

Efforts to purify drinking water began in approximately 4000 B.C. The initial development of water purification techniques began with an attempt to filter the water using charcoal, as is shown in Figure 1. Once filtered, the water was heated through exposure to sunlight or by boiling, after which the water was strained. After that, the water was considered potable. Potable water exclusively refers to safe drinking water, not referring to clean water for washing and household use. [2]. People measured the quality of their drinking water by its turbidity, or the state of water clarity. The higher the turbidity, the cloudier the water appeared. This turbidity level provided an indication of how contaminated the water was [3].

Figure 1. Charcoal Filtration. http://www.practicalprimitive.com/images/newsletters/charcoalfilter/fullfilter.jpg

In early 1700s, water filtration, a process to remove hazardous particles was invented but filtration only began to get popular in the early 1800s in Europe. At that time, engineers started to play a role in creating effective water filtration techniques. The problem with filtration at that time was that there were some contaminants that were not visible to the naked eye, so filtration alone could not ensure that the water was safe to drink. For example, cholera, a disease that haunted London in 1854 and killed hundreds of people, is caused by bacteria found in contaminated water. John Snow, an English scientist, found that an ineffective water filtration mechanism on one of the street pumps caused the cholera epidemics. This tragedy shows us that microscopic organisms could be present in dirty water. Hence, it drives engineer to improve water purification systems to filter out most microbes that could be harmful to our health [4].

Furthermore, engineers began to use chlorine as a disinfectant to reduce turbidity, and this effort has successfully reduced the risk of contracting water-related diseases such as typhoid, dysentery, or cholera. This process was later called chlorination; along with filtration, it has become one of the most effective methods of water purification. However, it was not the end of the engineering journey, because in the 1980s it was found that some chlorine-resistant pathogens could exist in purified water. The pathogens were quite dangerous; they could cause hepatitis, gastroenteritis, or cryptosporidiosis, which could greatly threaten human lives [2]. This issue forces more engineers and scientist to devote their full attention to improving water purification methods so that more bad chemicals can be removed from the water.

Implications for Health

Approximately 3.5 million people still succumb each year to diseases that are caused by drinking contaminated water. Most of the time, approximately half of the world’s hospital beds are occupied by people suffering from plagues that were the result of drinking dirty water. These statistics indicate that the lack of access to clean drinking water is very severe in the world [5]. According to the National Academy of Sciences, illnesses that are caused by drinking dirty water can be categorized into five types: waterborne, water-washed, water-based, water-related and poor sanitation. However, only waterborne illnesses are associated with the danger of drinking dirty water. As shown in Figure 2, waterborne diseases result from drinking water that carries micro-parasites, bacteria and viruses that live in waste-contaminated water. Examples of the diseases are typhoid, cholera, dysentery, hepatitis, and Giardia [5].

Figure 2. Waterborne disease. http://blog.ace4it.com/wp-content/uploads/2011/02/disease.png

The diseases usually come from bacteria that contaminate the water. The bacteria often originate from human and animal wastes that go back into the water supply and contaminate the water [6]. Not only that, but there are also industrial and agricultural chemical wastes that could pollute the water [7]. These chemicals are claimed to be very damaging to our bodies. The risks to human have become more threatening than before because of the increase in agricultural and industrial chemical uses. Once this polluted water reaches the consumers, it is too late to prevent them from getting catastrophic diseases [8]. Therefore, an advanced water purification system is needed to prevent this dirty water distribution problem from happening as we consume water on a regular basis. Thus, purified water helps us to be more healthy and protected from all the potential diseases.

Measuring the Quality of Drinking Water

In order to create an efficient water purification system, it is important to know the standards that determine whether the water is safe to drink. Appraising the water quality is quite tricky. How can we tell if any given water sample is hygienic? Is it the color or the odor? Yes, it is true that color and odor are the most obvious ways to assess the quality of the water. Nonetheless, scientists and engineers found that taste and odor are not the only parameters of safe drinking water. Just because the water looks clear and tasteless does not mean there are no harmful bacteria and chemicals that are not visible to the naked eye [9].

There are several factors that determine whether water is safe to drink, including pH level, turbidity, odor, nutrients, total suspended solids (TSS), and hardness. PH is a scale ranging from

0 to 14 that measures how acidic or basic the water is. If the pH level is too far from 7 (neutral), it indicates the possibility of there being some undesirable pollutants in the water that could be threatening to human health. As shown in Figure 3, turbidity has been one of the most important factors in determining water quality. If the water condition is muddy, it means that the turbidity level is high. Thus, it implies that people who drink the water will be more likely to experience gastrointestinal disease such as diarrhea. In addition, TSS are small solid materials that are contained in the water. They usually consist of calcium, chlorides, nitrate and other ions particles that are able to pass through the water filter. Higher concentrations of suspended solids can serve as carriers of toxic chemicals. For instance, pesticides used on irrigated crops might get carried away when the concentration of TTS is high, which could be dangerous when the water is consumed by humans. Last but not least is the idea of hardness in water. If the water is hard, it contains a substantial amount of calcium and magnesium, as well as a variety of other metals. As water goes through rock and soil, it dissolves a minuscule amount of minerals and holds them in solution. Hard water is safe to consume as long as the metal substances do not exceed 10% of the whole water solution [10]. These parameters allow water suppliers to examine the drinking water thoroughly so that the water passes the minimum standards for potable water, even if the water quality is not perfect.

Figure 3. Turbidity. http://steinhardtapps.es.its.nyu.edu/nyuhudson/wp-content/uploads/2012/10/turbidity.jpg

Drinking Water Purification Process

To sanitize the water, several steps need to be taken. The water purification process is useful because it may significantly decrease the number of particles including suspended solids, parasites, microscopic organisms, algae, viruses, fungus and a range of dissolved and particulate materials in the water [11]. There are several techniques for making potable water. Even though in different places the water purification standards may vary, the necessary steps of purifying water are still the same.

The most widely used water purification requires six fundamental steps. First, the water is taken from a water source such as a well, river, lake, or reservoir. [12]. Then, coagulants like lime and

alum are added to the water. A coagulant is a magnet-like substance that causes particles inside the water to cluster together. Once the particles are clustered together, they are called floc. Next, the water is clumped and shaken together. After that, the water is left for 24 hours so that the clumped materials can gravitate to the bottom of the water. This separation between floc and water is called clarification. After that, the water is filtered so that the water can be entirely separated to the floc. By this time, most harmful particles will have been discarded. However, we still need to remove the residual tiny particles that are not able to be removed by filtration. The water is then stored in a closed tank in order for it to be disinfected by both chlorine and ozone so that most viruses, germs and fungus are eliminated. Then, the water is aerated because lack of oxygen in water increases the relative population of microorganisms. Aeration is the process that increases the oxygen saturation, so that the water carries more oxygen. Ultimately, the water is channeled to households through pipes for distribution [13]. This method of water purification, as shown in Figure 4, has been adopted in most places because of its effectiveness in treating dirty water so that it becomes safe to drink.

Figure 4. Water purification process. https://www.ecwa.org/content/learningcenter/treatment.gifs

Future Developments

By using the current water purification method, we can arrive at water that is relatively safe to drink. However, scientists and engineers are still trying to find better ways to improve this technique, since there could still be a very tiny harmful particle that is very difficult to remove using the current method. This results in more people expecting scientists and engineers to come up with a new advanced way of purifying water. Although most water purification systems in the U.S. are already sophisticated enough, there are still small fractions of people who do not have access to clean water. One potential future water treatment was found by the Southern California Institute of Architecture when they held a contest to select the best project for the 4-mile area near the Los Angeles River and promised ten thousand dollars in prizes for winners. Project Umbrella ended up winning the competition, it is mushroom-like structures named solar evaporators that penetrate into the city's sewage, gathering and purifying the dirty water originating from the surrounding neighborhoods. Through the process of evaporation and condensation, clean water is allocated and released into the streets which reconstructs the conventional streets into a network of lush and cultivated landscapes as shown in Figure 5 [14].

Figure 5. Project Umbrella. http://brentwoodlifestyle.losangelesrealestatevoice.com/2010/10/07/new-construction-series-project-umbrella/

However, if we look to many developing countries such as countries in Africa or South East Asia, the problem of dirty water is much worse. So we should not only care about developing the United States’ water purification system, we could also help other developing countries to revitalize their water treatment processes. The problem is that most developing countries do not have tremendous resources like the United States has with the Project Umbrella so they might not be able to create large-scale water purification processes which cost a lot of money. Consequently, small-scale devices are being developed for developing countries where the regular water purification system is not yet capable of generating clean water. The device is a lifestraw, which is a tube that can be used to purify the unclean water and make it safe to drink, as shown in Figure 6. This straw can greatly reduce the chance of people contracting familiar water-related diseases such as typhoid, cholera, and diarrhea. Also, this device is not expensive, so that it is possible for destitute families to afford it and use it on a daily basis [15].

Figure 6. Lifestraw. http://inhabitat.com/6-water-purifying-devices-for-clean-drinking-water-in-the-developing-world/

The lifestraw example indicates that we do not have to invent an expensive, huge, or futuristic water purification process. A simple tool that can make other lives easier is enough for the future development of water purification. Now, it becomes a challenge for engineers to come up with better and cleverer methods of purifying water that could decrease the number of casualties due to drinking dirty water.

References:

[1] C. Binns et al (2013, November). How Long Can a Person Survive Without Water? [Online]. Available: http://www.livescience.com/32320-how-long-can-a-person-survive-without-water.html

[2] The History of Drinking Water Treatment [Online]. Available: http://www.epa.gov/safewater/consumer/pdf/hist.pdf

[3] Water Quality – Turbidity [Online]. Available: http://www2.vernier.com/sample_labs/ESV-12-COMP-water_quality_turbidity.pdf

[4] E. R. Tufte, “John Snow and the Cholera Epidemic,” in Visual and Statistical Thinking: Displays of Evidence for Making Decisions, 5th ed. Cheshire, CT: Graphics Press LLC, 1997, pp. 5-16.

[5] B. Robinson. (2013, June 8). The Dangers of Dirty Water [Online]. Available: http://www.weathermatic.com/blog/dangers-dirty-water

[6 Health through Safe Drinking Water and Basic Sanitation [Online]. Available: http://www.who.int/water_sanitation_health/mdg1/en/

[7] S. R. Overmann. Water Pollution by Agricultural Chemicals [Online]. Available: http://wps.prenhall.com/wps/media/objects/1027/1052055/Regional_Updates/update30.htm

[8] C. Taylor and J. Yarner. Wastewater [Online]. Available: https://engineering.purdue.edu/~frankenb/NU-prowd/wwater.htm

[9] Is it Safe to Drink? [Online]. Available: http://www.novascotia.ca/nse/water/docs/wellwaterbooklet1.pdf

[10] Measurement of Water Quality [Online]. Available: https://wiki.engr.illinois.edu/download/attachments/31394596/Week5.pdf?version=1

[11] Decontamination: What Exactly is Decontamination [Online]. Available: http://mantisenvironmental.com/decontamination/

[12] Where Does Our Household Water Come From? [Online]. Available: http://water.usgs.gov/edu/qa-home-wherefrom.html

[13] Water Treatment Process [Online]. Available: http://water.epa.gov/learn/kids/drinkingwater/watertreatmentprocess.cfm

[14] F.R. Smith. Community Watch… Project Umbrella [Online]. Available: http://brentwoodlifestyle.losangelesrealestatevoice.com/2010/10/07/new-construction-series-project-umbrella/

[15] 6 Water-purifying Devices for Clean Drinking Water in the Developing World [Online]. Available: http://inhabitat.com/6-water-purifying-devices-for-clean-drinking-water-in-the-developing-world/