One of the processes that occurs in the body is called “inflammation.” Inflammation occurs when a cut into the skin also punctures a blood vessel. This situation directly exposes the blood to the air. Inflammation occurs in a few steps. First, the blood vessels near the wound are expanded (which causes the swelling that we see near the cut) and special proteins called “fibrins” are brought in. These fibrins bind to each other to form a net-like structure. We are all quite familiar with this net, which we call a blood clot. This net stops the bleeding and cuts the interaction between the air and the blood within a few minutes.

Next, it is time to quickly eliminate any foreign objects that got into the tissue. Special immune cells called “macrophages” are sent to the crime scene to clean up. Macrophages are large white blood cells that “eat” microbes and other foreign objects using a process called “phagocytosis.” After the scene is all cleaned up, these macrophages excrete special molecules that induce tissue repair and return the blood flow to normal. An important note here is the specific order of these events. Like every single process in the body, they occur in the most purposeful way possible. What do I mean? I mean that, first the wound is closed urgently; second, macrophages are sent in; third comes the tissue repair. Any other order would have greatly lowered the effectiveness of inflammation. Imagine that the wound is closed after the macrophages are sent in. Then, by the time the macrophages killed all the microbes, twice as many would have entered the scene. The body seems to know every single event beforehand and plans its defense accordingly.

Our body is perfectly calibrated to keep our blood, the milk of our organ systems, absolutely pristine.

Let’s say a microbe managed to sneak into the blood before inflammation occurred, and is long gone to another region of the body. Does the microbe win? Unfortunately for the microbe, it has to pass another test. This time the tester is the lymphatic system. The lymphatic system is the sewage system of the body. When the blood transfers its nutrients to the tissue, the fluid goes through the “interstitial area” (the empty space between organs). During this process, some of the fluid stays in this area and starts to accumulate. This is where the lymphatic system kicks in. The lymphatic system consists of many tubes running parallel to the blood vessels and recollects any excess fluid and transports them to the subclavian vein near the neck. This way, excess fluids of the body and all of the molecules in them, are reintroduced into the circulation. If there is a problem with this process, an abnormality called “edema” occurs. Of course, the blood is a very sensitive fluid because it travels through the whole body and seeps into almost every single cell. If a microbe were to get into it, it would easily spread and cause disease. So, the lympatics first does a checkup on the body fluid. This checkup occurs at special nodes in the system called lymph nodes found all over the body. Two of the most famous lymph nodes are the spleen and the tonsils. Within these nodes are lymphocytes, special immune cells that “tag” bacteria and other microbes to be later destroyed by macrophages. Thus, the blood is continuously cleaned and kept safe from harmful microbes.

Last but certainly not the least, the final inspection the blood goes through takes place in the kidneys. The aforementioned two checkpoints prevent the entrance of any foreign materials into the blood, and the elimination of any microbes lucky enough to somehow make it through. So, the only task to be completed is the elimination of excess molecules formed in the metabolism. For example, the blood in the veins (the vessels that carry carbon dioxide formed by the respiration of cells) is carried to the lungs where the carbon dioxide is exhaled. But, a much more precise mechanism comes into play in the kidneys. Blood vessels that come from all around the body form a knot-like structure in the kidney called the “glomerulus.” This knot-like shape increases the surface area of filtration. The blood running from the glomerulus is then filtered into the “Bowman capsule,” which surrounds the glomerulus.

But wait! The sanitation system is not satisfied with this first filtration and “thinks” that the filtrate is not ready to be excreted by the urine. So, a more delicate filtration occurs right after the filtrate enters the “proximal tubule.” While passing through this tubule, essential molecules are immediately reabsorbed into the body. The most valuable of all these molecules is glucose, since it is the main source of energy in the body. The proximal tubule reabsorbs around 98 % of all the glucose, while the distal tubule scouts out the rest. After the tubules are done with the filtration, not a single glucose molecule is left in the urine. As a matter of fact, the presence of even a few glucose molecules in the urine leads to a diagnosis of “renal glycosuria.”

After the proximal tubule, the filtrate goes into the “loop of Henle,” where it is dipped into a high-concentration environment. Water travels passively (without the need for energy) from low-concentration to high-concentration areas. In the loop of Henle, the urine is low-concentration, so water runs back into the body. Thus, any excess water in the urine is effectively and economically reabsorbed. The big machine that consists of the glomerulus, the Bowman capsule, the tubules, and the loop of Henle is called a “nephron.” Everything described above occurs in a single nephron. The average number of nephrons in one kidney is around 1,000,000. The human bladder holds around 150 ml of urine on average. So, each nephron is actually responsible for 0.00015 ml of urine production. The kidneys filter over 1,000 liters of blood each day, so our blood is kept just as we want it. Millions of tiny nephrons work in unison to take in huge amounts of blood and they know exactly what to leave and what to keep, 24 hours a day, 7 days a week.

Our blood is our life source. It is the milk of the organs, and our organs would dry up without it. Believe it or not, our organs are quite picky. If they are to receive anything they don’t like, they will start acting up. In order to keep the organs happy, the three mechanisms mentioned above have to work hard and not make a single mistake. These mechanisms are, of course, also made up of cells. These miniscule cells “know” exactly what their clients on the ends of the body like and don’t like, and prepare the blood composition accordingly. Only one word can describe these wondrous mechanisms: Impeccable.

Brian Turk is a medical student from New Jersey. He writes on medicine, health, and biology on a freelance basis.

Today, more than 1 billion people are suffering from the lack of potable water. About 2.3 billion people (41 percent of the earth’s population) live in regions with water scarcity; this number is estimated to be 3.5 billion by 2025.1

96.5 percent of the world’s water is found in seas and oceans, and the remainder is found as ice caps, brackish water, and fresh water sources (e.g. lakes, rivers, and ground waters). To overcome water shortage problems, methods such as water conservation and dam construction have been applied for several years, but they are not enough against increasing water demand and decreasing fresh water sources.2

Water is also very important for generating energy, and vice versa. The largest portion of U.S. electric production is provided by thermoelectric power generation, where steam-driven turbine generators are used to generate electricity. In 2000, thermoelectric power plants used 39 percent of all fresh water sources in the United States.3 All these reasons make the production of drinking water a worldwide issue.

Desalination

Since most of world’s water supply is found in oceans and seas, desalination is the process of removing salts and minerals from either ocean or brackish water to make it safe for human consumption and use. The most widely applied desalination processes are divided into two main categories, thermal distillation processes and membrane processes.

Desalination via thermal distillation methods, which separate liquid mixtures based on their boiling points, mainly fall into three categories: multi-stage flash (MSF), multi-effect distillation (MED), and mechanical vapor compression (MVC). Thermal distillation processes require the evaporation of water while leaving the salt in a concentrated brine. Middle Eastern countries mainly use thermal-based desalination plants to produce fresh water because of their easily accessible fossil fuel sources.2, 4

Membrane-based separations are the main choice of producing potable water in countries outside the Middle East. More than 50 percent of the newly installed desalination plants have been using reverse osmosis (RO) membrane technology (since 2001).2

Membrane separations

A membrane is an interphase between two adjacent phases acting as a selective barrier, regulating the transport of substances between the two compartments. It is a very thin film that allows passage of some types of substances while preventing the passage of other substances, depending on their sizes. Membranes used for separation technology gave rise to an interdisciplinary area including many fields of science and engineering such as chemistry, chemical engineering, material science, process engineering, environmental science, ecology, and economics.5, 6 Today, the membrane industry is impressively large. The membrane separation technology market is quite diverse and ranges from medicine to the chemical industry, and the most important markets are medical devices and water treatment. There was a $2 billion sale of synthetic membranes worldwide in 2003.6

Water purification membranes

Water treatment processes employ several types of membranes. They include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. They are designed to remove materials of increasing sizes. MF membranes have the largest pore size and typically reject large particles and various microorganisms. UF membranes have smaller pores than MF membranes and, therefore, in addition to large particles and microorganisms, they can reject bacteria and soluble macromolecules such as proteins. RO membranes are effectively nonporous and therefore exclude particles and even many low molar mass species such as salt ions, organic substances, etc.7 NF membranes are relatively new and are sometimes called “loose” RO membranes. They are porous membranes, but since the pores are ten of angstroms or less, they exhibit performance between that of RO and UF membranes.8 Of these membranes, NF and RO membranes constitute the dominant technology for desalination of water.9

2.1 Nanofiltration Membranes

Membranes for nanofiltration (NF) are usually comprised of cellulose acetate or aromatic polyamides. NF allows diffusion of organic compounds, and rejects some salts with low pressures being applied. NF itself cannot purify seawater to drinking water standards, but it is a process that can be used to produce mildly salty water, or as a water-softening technique.2, 4 When NF is coupled with RO, then it can be used to turn seawater into drinking water.10

Nanofiltration membranes usually have negative charges (e.g., carboxylate groups, sulfonate groups, etc.), and as a result, ion repulsion is a major factor in determining salt rejection. More highly charged ions, such as sulfate, are more highly rejected than monovalent ions, such as chloride, by a negatively charged nanofiltration membrane. In particular, NF membranes are used to remove divalent ions such as calcium and magnesium, which are mainly responsible for water hardness. These membranes also usually display good rejection of organic compounds with molecular weights above 200 to 500 grams.2,11,12

2.2 Reverse osmosis membranes

Osmosis is a natural process in which water molecules move across a semipermeable membrane from a lower solute concentration area to the higher solute concentration area. Water flows until a chemical potential equilibrium of water is established. When equilibrium is reached, the pressure difference between the two sides of the membrane is equal to the osmotic pressure of the solution.12

Reverse osmosis (RO) is the process of forcing water from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure that is greater than the osmotic pressure. As a result, separation of water from the solution occurs as pure water from the high concentration side to the low concentration side. The RO process includes a feed water source, feed pre-treatment, a high-pressure pump, RO membrane modules and post-treatment steps.

RO membranes are capable of rejecting monovalent ions such as sodium and chloride, which makes the RO process a valuable method for desalination. Membranes used for RO processes have salt rejections of more than 99 percent. RO membranes do not have distinct pores, but rather rely on free volume within the polymer film.

RO membrane separations depend highly on the properties of the polymer film such as the chemical and physical structure of the membrane material. Desired RO membranes should be resistant to chemical substances and microbial organisms, stable over a long time both mechanically and structurally, and have ideal separation properties such as high water flux, high salt rejection, chlorine, and fouling (clogging of membrane pores) resistance.

Approximately one billion of six billion people in the world live in water-stressed areas, and RO membrane technology is the leading desalination technology to overcome the problem of insufficient clean water and estimated to continue its leadership in the near future.13 Scientists and engineers are extensively investigating the development of the most efficient membrane desalination technology to produce the cheapest potable water.

On the other hand, cells use membranes, though scientists do not try to further develop them, since they were already designed in a perfect manner. Cellular membranes have a phospholipid structure with embedded proteins. They control many different kinds of transportations of substances in and out of cells (e.g. sugar, drugs, ions). They are so well designed that they know which substances are helpful or harmful for the cell, and decide on the passage of substances based on that. Many researchers have tried countless times for many years to produce an equally wonderful membrane technology for making clean water. But cellular membranes, consisting of hundreds of functions in living organisms, do not form spontaneously.

REFERENCES

1) R.F. Service, Freshwater resources, desalination freshens up. Science, (2006). 313, 1088- 1090.

2) L.F. Greenlee, D.F.Lawler, B.D. Freeman, B. Marrot, P. Moulin, Reverse osmosis desalination: Water sources, technology and today’s challenges. Water Research (2009), 43, 2317-2348.

3) T.J. Feeley, T.J. Skone, G.J.Stiegel, A. McNemar, M.Nemeth, B. Schimmoller, J.T. Murphy, L. Manfredo, Water: A critical resource in the thermoelectric power industry.Energy (2008), 33, 1-11.

4) G. A. Tularam, M. Ilahee, Environmental concerns of desalinating seawater using reverse osmosis. J. Environ. Monit.(2007), 9, 805–813.

5) P. Vandezande, L. E. M. Gevers, I. F. J. Vankelecom, Solvent resistant nanofiltration: separating on a molecular level. Chem. Soc. Rev.(2008), 37, 365–405.

6) M. Ulbricht, Advanced functional polymer membranes. Polymer (2006), 47, 2217–2262.

7) R.H. Perry, D.W.Green, Eds., Perry’s Chemical Engineers’ Handbook, 7th ed., McGraw-Hill: New York, 1997.

8) Sagle, A., and B. Freeman, “Fundamentals of Membranes for Water Treatment,” in The Future of Desalination in Texas: Volume 2, Report Number 363, Texas Water Development Board, Austin, TX, pp. 137-154 (2004).

9) H.B.Park, B.D.Freeman, Z.Zhang, M.Sankir, J.E.McGrath, Highly Chlorine-Tolerant Polymers for Desalination, Angew. Chem. Int. Ed. (2008), 47, 6019-6024.

10) N. Hilal, H. Al-Zoubi, N. A. Darwish, A. W. Mohammad, M. Abu Arabi, A comprehensive review of nanofiltration membranes: Treatment, pretreatment, modelling, and atomic force microscopy, Desalination (2004), 170, 281-308.

11) A. Gorenflo, D. Velazquez-Padron, F.H. Frimmel, Nanofiltration of a German groundwater of high hardness and NOM content: performance and costs. Desalination (2002), 151, 253-265.

12) M.E.Williams, A Brief Review of Reverse Osmosis Membrane Technology,EET Corporation and Williams Engineering Services Company, Inc., Harriman, TN, 2003.

13) K. P. Lee, T. C. Arnot, D. Mattia, A Review of Reverse Osmosis Membrane Materials for Desalination – Development to Date and Future Potential. J. Membr. Sci. 370 (2011) 1-22.

It could be said that the first pollution started with the lighting of the first fire. In 1869, the declaration of the Massachusetts Public Health Committee gave the first important scientific warning that highlighted that environmental concerns had reached threatening dimensions. Today, environmental problems arise for the most part from industrialization and unplanned urbanization that is the consequence of industrialization.

Cleanliness and economy are fundamental precautions that need to be taken to protect the environment. In the Holy Qur’an and in the hadiths cleanliness is given great importance:

Truly God loves those who turn unto Him, and loves those who have a care for cleanliness. (Baqara 2:222)

In this verse, we are being told that the people whom God loves are those who regret their wrongdoings and turn to Him and those who are clean. Thus, a moral cleanliness with penitence is stressed alongside physical cleanliness.

Environmental problems are wide ranging: Global warming, the destruction of forests, erosion, desertification, the depletion of the ozone layer, the contamination of lakes and rivers, accumulation of solid waste, air pollution in major cities, electromagnetic pollution, radioactive pollution, noise pollution, etc. All those are of importance and require special attention, one by one. The most important environmental problems which face our world today are:

1. Global warming

2. An increase in the depletion of the ozone layer

The ozone layer that surrounds our world is a subject that has to be approached seriously. The Earth’s crust is the layer that consists of the atmosphere, the oceans, and the solid part of the Earth on which we live that extends 17 kilometers down. The most plentiful element on the surface of the Earth is oxygen; its mass is at a rate of 49.5%. Oxygen is found in metal ores, plants, animals, humans, water, and in the atmosphere. In its free state it usually exists in a diatomic molecule; that is O2. The molecule that consists of three oxygen atoms is called ozone. Ozone is an allotrope of oxygen, and thus has a different structure. If a certain amount of energy is given to diatomic oxygen molecules, then triatomic ozone molecules are formed, as seen in the following formula:

3 02 (g) + 68 Kcal –> 2 03 (g)

While oxygen makes up 20% of the atmosphere in volume, and 21% by mass, the average amount of ozone is 0.02% ppm by volume; that is equal to 1/10 billionth the amount of oxygen. Due to its higher oxidating effect in comparison to oxygen, a high ozone concentration would be very harmful to living beings. Ozone concentration, which in low altitudes is low, increases with altitude, until 30 km; in the stratosphere it reaches a tenfold concentration, 0.2% ppm. In altitudes that are higher than 30 km, the ozone concentration decreases gradually, with no ozone being found in altitudes higher than 80 km.

This high concentration of ozone in the atmosphere at altitudes of 30 km is what is known as the ozone layer. The ozone layer acts like a curtain that protects living beings from harmful effects of high energy sun radiation, and is therefore vital for human life. The sun protects us by filtering the harmful UV rays of the sun and preventing them from reaching the surface of the Earth. If this rate of prevention of UV rays falls below 99% the consequences in nature are critical. The most basic of such results would be an increase in cases of human skin cancer. In the long term, the high energy rays would destroy the C – H and 0 – H bonds that are found in living organisms, and thus would mean the destruction of life.

In chemistry books we can already find chemical equations that show us why ozone exists at 30 km high and why certain industrial chemicals decompose and destroy the ozone layer; we can also discover why this activity is occurring at the North and South Poles. Preventive measures are also listed in such books so that we can take to prevent this from happening.

The most important aspect of this topic for us is that it is totally impossible for these molecules to cause such consequences by their own will and choice; this is due to the great mercy and wisdom that is inherent in the creation of the Earth. While this substance is harmful to living creatures in low altitudes, its existence in higher regions of the atmosphere is vital to all the life on the Earth.

In chemistry books, the abundance of hydrogen in higher regions of the atmosphere is explained by its small molecule weight (2g), but not a single word is mentioned about the miraculous formation of the ozone layer at 30 km! But, logically one would presume that due to its being 24 times heavier (48g) than hydrogen, ozone should be found in its highest concentration nearest to the surface of Earth.

The “ozone curtain” is truly a curtain. It is a test for us: A curtain that hides the truth of a protective hand; a curtain beyond which we should try to see.

Note

1. Bediuzzaman Said Nursi, The Rays, Fourth Ray, Sozler Publications.