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Dihydrogen monoxide or DHMO, also known as Hydrogen Hydroxide or Hydronium Hydroxide is one of the most prolific chemicals contacted in daily life. It is colorless, odorless and tasteless, and sometimes considered harmless, and yet kills very large numbers of humans every year. DHMO is generally a liquid, but is also available in solid and gaseous forms. Prolonged exposure to solid DHMO causes severe tissue damage, accidental inhalation can be fatal, and ingestion can cause bloating, nausea leading to sweating and urination.
The web page for the “Coalition to Ban DHMO” lists a slew of hazards associated with it. DHMO is the primary ingredient of acid rain, contributes to the greenhouse effect, causes havoc with electrical equipment, can be been found in cancerous tissue, can cause severe burns, accelerates corrosion of metals and is the primary cause of thousands of other calamities (including tornadoes, flooding and tsunamis).
Yet, handling, distribution and use of DHMO is perfectly legal. It contaminates all of our streams, lakes and rivers. It is found in easily detectable quantities in the atmosphere. It is prolifically used as an industrial solvent and legally dumped it into the environment. Amongst other uses, DHMO is used in animal research, production of pesticides, manufacture of hazardous chemicals, detoxification of food, enhancement of plant growth and maintaining chemical balance in swimming pools. It is also used as a coolant in nuclear reactors, for manufacturing biological weapons, for religious rituals and has been used in death camps.
Yet, most unknowing victims consider DHMO vital to life. Absence of DHMO can lead to famine, renal failure and disease. It is used daily for food preparation and is present in most kitchens and bathrooms. It has been called the “elixir of life”. It is also vital to our existence, without DHMO we would be all dead.
In case you are wondering, where you may run into DHMO, try the nearest tap. The chemical formula for DHMO is, of course, H20 and the unenlightened masses tend to call it “water”.
Water is everywhere, yet it is often in short supply. The oceans hold about 98% of the total amount of water on earth, but seawater is unfit for consumption. Human habitations can exist only where fresh water is available. Yet, people have inhabited deserts by building canals and pipelines to bring water in from elsewhere.
Water is all pervasive and permeates everywhere. Consider an event that may have happened over 3000 years ago. In the year 1307 AD the most famous Pharaoh of them all, Tutankhamun, was crowned the King of Egypt at the age of nine. One day, when it was dinnertime at the Tutankhamun household, the boy-king was having a royal tantrum. Surrounded by fawning advisors and servants, he screamed and yelled and threw a goblet of water towards the “Ay” (or high official). Of course, the glass shattered and spilled water over the floor, which was promptly mopped up.
That was then, and this is now. As you read this, you may be sipping a glass of your favorite beverage. Is there any possibility that any molecules of water, from the royal fling, can show up in the beverage in your glass?
Surprising, but true, not just a few, but a lot of the royalty-tainted molecules, live close to you. Over the thousands of years, we can safely assume that Tutankhamun’s water has evaporated and dispersed over the entire world. A little arithmetic comes to the rescue. A glass of water (250 ml) contains about 8.36x1024 molecules of water. The earth contains about 140x107 cubic kilometers of water, which amounts to about 4.62x1046 molecules. If we disperse the glass of water into all the water on earth, and then pour a glass of the mixture, we find there are about 1,500 molecules from Tutankhamun’s goblet in our glass.
Of course, during his brief 18-year life, Tutankhamun used a lot more than a glass of water. All the hundred of liters of water that has passed near or through the Pharaoh contributes to millions of molecules in every drink today. Hence, fresh water is never quite so fresh.
In cities, we must have a supply of ample so-called fresh (or potable) water. Such water is first collected from streams, rivers and lakes or from underground aquifers. Most surface collected water contains non-palatable organisms and other matter of questionable origin that make it non-potable. Hence the water is first treated.
The method of water treatment varies upon its origin. Ground water does not need much treatment as it has filtered though many a layer of soil and sand, rendering it quite pure. Surface water needs more treatment, and wastewater needs even more. The majority of the cities use surface water for economic and ecological reasons. Water from underground does not get replenished quickly. It may take many years of torrential rain, followed by many years of soaking to replace a year’s worth of groundwater consumption. Levels in the world’s major aquifers are becoming dangerously low due to over consumption.
Surface water can come from two major sources. It can be from some natural sources such as a lake, river or stream, or from wastewater that flow out of the sewer systems. Of course, lake and river water is intermixed with wastewater from cities upstream. Hence, one person’s excreta can become another person’s elixir.
Collected water from natural sources is transformed into good water by a set of treatment phases. At the first step the water passes through a series of screens designed to remove large debris such as twigs and leaves. Then, the water slowly moves through a pre-sedimentation basin where much of the sand and silt settle to the bottom. The next phase consists of the adding of a liquid chemical, known as a coagulant, which consists of positively charged ions. Then the water flows into a large basin where it is slowly stirred by large paddles. Suspended particles, which are negatively charged, are attracted to the positively charged coagulant and they start to settle. After settling the water at the top of the basin moves to a large gravity filter made of hard coal (anthracite), gravel and sand. Finally, chlorine is added to kill any disease causing bacteria. Fluoride is added to help prevent tooth decay. As it leaves the treatment plant the water travels though old and rusty pipes to your residence.
A similar, though more elaborate process is used to convert wastewater, also called “gray water”, into drinking water. Gray water has concentrated amounts of nefarious stuff with awesome names such as Coliform, E-Coli, Cryptospridium, Giardia, and other unfriendly contaminants such as organic compounds, pesticides, heavy metals, and so on. Gray water is first sent through clarifiers, which separate water from sludge and then to oxidation ponds. In these ponds the organic matter is oxidized with the help of algae. From oxidation ponds, it flows to marshes, teeming with plant life, which consume unwanted nutrients from the water. Finally, it goes through the filtration, coagulation, sedimentation and chlorination phases. As a side effect, the recovered sludge can be passed though digesters, which generate methane gas (a good source of energy) and solids that can be used for soil conditioning.
Of course, even if gray water is not used for drinking, it can be used for agriculture. Even if that is not the case, the gray water is passed though the clarifying and oxidation phases before disposal to eliminate the chance of contaminating groundwater, or populations downstream.
Converting salty seawater to potable water is possible though expensive via desalination methods. Desalination can be done by distillation—boil the water and condense it. Distilled water is the purest form of water. Reverse osmosis is also used for desalination, where the water is forced though membranes that let the molecules of water through but not molecules of salt.
Finally, the finicky consumers of water worry about the taste and hardness of water. Water that contains dissolved calcium and magnesium compounds, notably bi-carbonates and sulfates is called “hard”. Hardness of water actually makes it taste better, but has detrimental effects on household pipes and utensils (hard crusty deposits form). Efficiency of soap and detergents is significantly reduced by hard water. Removing the calcium ions and replacing them with sodium ions by a process called ion exchange can soften water. Some charlatans claim that passing water through a magnetic field alters the calcium in such a way that is stops being nasty. The only people who benefit from the magnetic water treatment equipment is the manufacturers of such trash.
As for taste, the possessors of refined taste buds, purchase bottled water for prices far exceeding that of one of the most profitable beverages in the world—Coca Cola.
Partha Dasgupta is on the faculty of the Computer Science and Engineering Department at Arizona State University in Tempe. His specializations are in the areas of Operating Systems, Cryptography and Networking. His homepage is at http://cactus.eas.asu.edu/partha