DESALINATION – Desalination is a process primarily done in developed countries with enough money and resources. If technology continues to produce new methods and better solutions to the issues that exist today, there would be a whole new water resource for more and more countries that are facing drought, competition for water, and overpopulation. Though there are concerns in the scientific world about replacing our current overuse of water with complete reliance on seawater, it would undoubtedly be at least an option for many people struggling to survive or maintain their standard of living.

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Water Desalination

Desalination Expands as Technology Becomes More Affordable

by Xanthe Webb Aintablian

Contributing Writer

Desalination (also spelled desalinization) is the process of creating fresh water by removing saline (salt) from bodies of salt water.

There are varying degrees of salinity in water, which affects the difficulty and expense of treatment, and the level of saline is typically measured in parts per million (ppm).

The U.S. Geological Survey provides an outline of what constitutes saline water:

1,000 ppm – 3,000 ppm is low salinity,

3,000 ppm – 10,000 ppm is moderate salinity, and

10,000 ppm – 35,000 ppm is high salinity.

Water that contains saline levels less than 1,000 ppm is generally considered fresh water and is safe to drink and use for household and agricultural purposes.

For a reference point, typical ocean water contains about 35,000 ppm, the Great Salt Lake contains variations of 50,000 – 270,000 ppm, and the Caspian Sea contains an average of about 12,000 ppm.

The more concentrated saline is in a body of water, the more energy and effort it takes to desalinize it.

Desalination Processes

Reverse Osmosis

There are several setbacks of reverse osmosis. The membranes are currently prone to gather too much bacteria and “clog up,” although they have improved since they were first used.

The membranes deteriorate when chlorine is used to treat the bacteria.

Other setbacks are the arguable water quality that reverse osmosis produces, along with the considerable pre-treatment that the salt water requires.

Forward Osmosis

The main setback to forward osmosis is that it has great potential, but is still fairly new to large-scale desalination and therefore needs funding and research to explore the possibilities that could improve it and reduce energy costs.

Electrodialysis

Thermal Desalination

Multistage Flash Distillation

Multiple-Effect Distillation

Negatives of Desalination

Geography of Desalination

Saudi Arabia is currently the world’s number one producer of desalinated water.

They use multi-flash distillation in several large plants, providing water for many large cities, including the largest city, Riyadh, situated hundreds of miles from the coast.

In the United States, the largest desalination plant is located in Tampa Bay, Florida, though it has a very small output compared to most facilities in the Middle East.

Other states that are developing plans for large desalination plants include California and Texas.

The United States need for desalination plants is not as severe as many other countries, but as the population continues to explode in dry, coastal areas, the need increases.

Future Options of Desalination

Desalination is a process primarily done in developed countries with enough money and resources.

If technology continues to produce new methods and better solutions to the issues that exist today, there would be a whole new water resource for more and more countries that are facing drought, competition for water, and overpopulation.

Though there are concerns in the scientific world about replacing our current overuse of water with complete reliance on seawater, it would undoubtedly be at least an option for many people struggling to survive or maintain their standard of living.

Xanthe Webb Aintablian

Writing and Editing Professional

Winchester, Virginia

I am a professional writer and editor. I like to work hard, think critically, and build relationships. I enjoy outdoor adventure and learning about nature, geography, and science.

https://www.thoughtco.com/water-desalination-definition-1435826

THE CHEMICAL STRUCTURE OF BENZENE - Kekulé’s Dream - In Kekulé first dream, he saw atoms dance around and link to one another. He awakened and immediately began to sketch what he saw in his dream. Later, he had another dream, in which he saw atoms dance around, then form themselves into strings, moving about in a snake-like fashion. This vision continued until the snake of atoms formed itself into an image of a snake eating its own tail. This dream gave Kekulé the idea of the cyclic structure of benzene.

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The Chemical Structure Of Benzene

Kekulé’s Dream

Michael Verderese
Professor Heinz D. Roth

In 1890, at the 25th anniversary of the benzene structure discovery, Friedrich August Kekulé, a German chemist, reminisced about his major accomplishments and told of two dreams that he had at key moments of his work.

In his first dream, in 1865, he saw atoms dance around and link to one another. He awakened and immediately began to sketch what he saw in his dream.

Later, Kekulé had another dream, in which he saw atoms dance around, then form themselves into strings, moving about in a snake-like fashion.

This vision continued until the snake of atoms formed itself into an image of a snake eating its own tail. This dream gave Kekulé the idea of the cyclic structure of benzene.

Using the programming languages javascript and html5, I created an animation to simulate Kekule’s dream.

The program utilizes iChemLabs’ ChemDoodle Web Components’ Application Programming Interface (API), a particular set of rules and specifications governing the open source, web-based Cheminformatics program.

When I was first given this project, Professor H.D. Roth explained to me his vision of what the animation should look like.

He said that the animation should begin with carbon atoms bouncing around the screen.

Then, one by one the atoms should link together to form a chain of atoms as in Kekulé’s first dream.

Finally, the chain should come together to form a ring, and the snake Kekulé saw eating its own tail should appear.

Kevin Theisen, of iChemLabs, provided a sixty-line code for an animation of a single carbon, represented by a gray circle, bouncing up and down inside a rectangular canvas.

The code utilizes ChemDoodle’s API, which is based on html5 and javascript. Using this API is advantageous because it can be run on any modern browser without requiring any additional plug-ins.

The bouncing motion was achieved by moving the atom a fixed number of pixels every frame (along the y coordinate), then reversing its direction once it reached the edge of the canvas.

Starting with this code, the previously fixed x coordinate was varied to allow the atom to move in two dimensions.

To allow for random speed and direction, the carbon’s x-axis and y-axis movements per frame were multiplied by a random decimal number between 0 and 1.

Once this was accomplished, more carbons were introduced to the canvas by adding carbon objects to the atom array of the molecule object supplied by the ChemDoodle API (Figure 1).

Collisions between the atoms are handled by exchanging the x and y vectors of one carbon with the other.

In order to give the animation the euphoric feeling of a dream, a random fading/flashing effect was added to the animation by randomly changing the opacity of the entire canvas. This effect carries through the entire animation.

In order to depict the vision of the atoms joining each other and moving around in a snake-like fashion, an algorithm was created to allow for one (lead) atom to move freely and for the others to join and follow it.

Upon each click of the mouse, the free carbon closest to the tail atom of the carbon string is linked to, and then pulled towards the tail atom.

This was achieved by creating a “bond” (part of ChemDoodle’s API) between the tail atom and the atom closest to it upon the mouse click.

The newly attached carbon then moves towards the end of the chain, exponentially increasing speed until its distance from the tail atom is 50 pixels.

Every frame, the program checks if any two atoms in the chain will be farther apart than 50 pixels, and prevents this by moving such atoms towards the one ahead of it in the chain.

After six carbons are linked together, the next mouse-click causes the chain to move to the center of the canvas and form a horizontal, six-carbon, zig-zag chain with 120-degree angles (Figure 2).

This was achieved by releasing the chain from the random snake-movement algorithm, and instead, each atom moves to its predetermined point in 150 frames.

Following the next mouse-click, the chain begins to rotate cylindrically. In order to give the illusion of the chain moving in three-dimensional space, the atoms move up and down according to a coordinated sinusoidal function.

This part of the animation is meant to represent the chain structure Kekulé envisioned in his first dream. The next click of the mouse releases the chain to move around as a string again.

The vision of the carbons coming together to form a snake eating its own tail is the pinnacle of Kekule’s benzene dream, and therefore required dramatic creation.

Upon the next mouse-click, the carbon chain again moves to the center of the screen, forming a hexagonal “ring” (Figure 3).

The movement of the ring was achieved by moving each atom to its next predetermined point in 150 frames, similar to the movement of the chain to its fixed horizontal position (Figure 2).

The next click causes the ring to expand and fade into the snake that Kekulé saw in his dream (Figure 4).

The snake is drawn over the molecule using the html5 drawImage function, which draws an image at a specified x,y coordinate.

The snake image is made to fade into view by increasing the opacity (alpha value) of the picture each frame, until it is completely opaque.

When Kekulé saw this snake, he made the connection to the chemical structure of benzene. This is portrayed following the next mouse-click.

As the snake begins to spin, the hexagon shrinks to fit inside the center of the snake, and one hydrogen atom is attached to each of the carbons (Figure 5).

In order for the snake to rotate, the orientation of the picture is rotated by 2 degrees each frame before being drawn.

When the snake begins to spin, the flashing effect observed throughout the animation ends, representing Kekule’s clarity at the end of the dream.

Altogether, this representation of Kekulé’s was achieved by approximately 550 lines of code. The residence time in each phase of the animation is determined entirely by the user.

The ChemDoodle Web Components library is very powerful, and implementing the functionality you want can take a while. We would like to help you. We can provide integration support, custom development, and custom licenses to you. Don't wait any longer. View our support options today and make your website one of the most advanced and futuristic scientific sites on the web!https://web.chemdoodle.com/kekules-dream/

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Figure 2: Six carbons have linked to form a chain.

Figure 1: A random array of fourteen carbons, represented by gray circles

Figure 3: The chain has closed to form a hexagonal “ring.”

Figure 5: As the snake disappears, the carbon hexagon is surrounded by hydrogen atoms

Figure 4: The ring is surrounded by a snake eating its own tail.

SEDIMENT GRAINS - Sediments are classified by their method of erosion as either clastic or chemical. Chemical sediment is broken down through chemical weathering with transportation, a process known as corrosion, or without. That chemical sediment is then suspended in a solution until it precipitates. Think of what happens to a glass of saltwater that has been sitting out in the sun. Clastic sediments are broken down through mechanical means, like abrasion from wind, water or ice. They are what most people think of when mentioning sediment; things like sand, silt, and clay.

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Sediment Grains

All About Sediment Grain Size

by Andrew Alden 

The grain sizes of sediments and sedimentary rocks are a matter of great interest to geologists.

Different size sediment grains form different types of rocks and can reveal information about the landform and environment of an area from millions of years prior.

Types of Sediment Grains

Sediments are classified by their method of erosion as either clastic or chemical.

Chemical sediment is broken down through chemical weathering with transportation, a process known as corrosion, or without.

That chemical sediment is then suspended in a solution until it precipitates. Think of what happens to a glass of saltwater that has been sitting out in the sun. 

Clastic sediments are broken down through mechanical means, like abrasion from wind, water or ice.

They are what most people think of when mentioning sediment; things like sand, silt, and clay.

Several physical properties are used to describe sediment, like shape (sphericity), roundness and grain size.

Of these properties, grain size is arguably the most important.

It can help a geologist interpret the geomorphic setting (both present and historical) of a site, as well as whether the sediment was transported there from regional or local settings.

Grain size determines just how far a piece of sediment can travel before coming to a halt. 

Clastic sediments form a wide range of rocks, from mudstone to conglomerate, and soil depending on their grain size.

Within many of these rocks, the sediments are clearly distinguishable -- especially with a little help from a magnifier. 

Sediment Grain Sizes

The Wentworth scale was published in 1922 by Chester K. Wentworth, modifying an earlier scale by Johan A. Udden.

Wentworth's grades and sizes were later supplemented by William Krumbein's phi or logarithmic scale, which transforms the millimeter number by taking the negative of its logarithm in base 2 to yield simple whole numbers.

The following is a simplified version of the much more detailed USGS version. 

Millimeters	Wentworth Grade	Phi (Φ) Scale
>256	Boulder	–8
>64	Cobble	–6
>4	Pebble	–2
>2	Granule	–1
>1	Very coarse sand	0
>1/2	Coarse sand	1
>1/4	Medium sand	2
>1/8	Fine sand	3
>1/16	Very fine sand	4
>1/32	Coarse silt	5
>1/64	Medium silt	6
>1/128	Fine silt	7
>1/256	Very fine silt	8
<1/256	Clay	>8

The size fraction larger than sand (granules, pebbles, cobbles. and boulders) is collectively called gravel, and the size fraction smaller than sand (silt and clay) is collectively called mud. 

Clastic Sedimentary Rocks

Sedimentary rocks form whenever these sediments are deposited and lithified and can be classified based on the size of their grains.

·         Gravel forms coarse rocks with grains over 2 mm in size. If the fragments are rounded, they form conglomerate, and if they are angular, they form breccia.

·         Sand, as you may guess, forms sandstone. Sandstone is medium-grained, meaning its fragments are between 1/16 mm and 2 mm. 

·        Silt forms fine-grained siltstone, with fragments between 1/16 mm and 1/256 mm. 

·        Anything less than 1/256 mm results in either claystone or mudstone. Two types of mudstone are shale and argillite, which is shale that has undergone very low-grade metamorphism. 

Geologists determine grain sizes in the field using printed cards called comparators, which usually have a millimeter scale, phi scale, and angularity chart.

They are especially useful for larger sediment grains. In the laboratory, comparators are supplemented by standard sieves.

Andrew Alden

Professional geologist, writer, photographer, and geological tour guide

Thirty-seven years of experience writing about geological subjects

Six years as a research guide with U.S. Geological Survey (USGS)

Member of Geological Society of America (GSA), and American Geophysical Union (AGU)

Experience

Andrew Alden is a former writer for ThoughtCo who contributed hundreds of articles for more than 17 years. Andrew works as a geologist, writer, editor, and photographer. He has written on geological subjects since 1981 and participates actively in his field. For example, Andrew spent six years as a research guide with the U.S. Geological Survey, leading excursions on both land land and at sea. And since 1992, he has hosted the earthquakes conference for the online discussion platform, The Well, which began as a dialogue between the writers and readers of the Whole Earth Review. 

In addition, Andrew is a longtime member of the member of the Geological Society of America — an international society that serves members in academia, government, and industry; and the American Geophysical Union — a community of earth and space scientists that advances the power of science to ensure a sustainable future.

Andrew lives in Oakland, California; and though he writes about the whole planet and beyond, Andrew finds his own city full of interest too and blogs about its geology. 

Education

Andrew Alden holds a bachelor's (B.A.) degree in Earth Science from the University of New Hampshire, College of Engineering and Physical Sciences, in Durham, N.H.

Awards and Publications

Andrew Alden on Earthquakes ​(The Well Group, Inc., 2011)

Assessment of River — Floodplain Aquifer Interactions (Environmental and Engineering Geoscience, 1997)

Andrew Alden on Hosting (The Well Group, Inc., 1995)

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