Your email address will not be published. Log In Register Search. A blog about climate change, education, and the search for solutions in adaptation and mitigation. Skip to content. Home LoginPress My Calendar. Desalination: The Science Posted on October 8, by climatechangefork. It still includes the most important elements, without providing so much information that the viewer is overwhelmed: It emphasizes the way in which the sun-induced evaporation from the ocean separates fresh water from saltwater.
Phillip; Science , : Such an improvement in power consumption gives almost everybody hopes for a practical way to address the global water stress. About climatechangefork Micha Tomkiewicz, Ph. In addition, he is the founding-director of the Environmental Studies Program at Brooklyn College as well as director of the Electrochemistry Institute at that same institution. Bookmark the permalink. December 5, at am.
August 24, at am. June 17, at pm. Ben Gillott says:. January 13, at am. Fiji says:. December 1, at pm. David Fan says:. February 21, at am. January 19, at pm. Leave a Reply Cancel reply Your email address will not be published. Search for:. Does anyone own the ocean? Answer: No Do you think you could just go out to the ocean and fill a bottle of water for drinking? Answer: No The ocean is full of saltwater. If you drink large quantities of saltwater, you become severely dehydrated.
The more you drink, the thirstier you get. And, dehydration can lead to seizures, unconsciousness and brain damage, along with overtaxing your kidneys, which can be fatal.
Today we are going to learn how seawater can be turned into water suitable for drinking. At the core of this process is something called a filter.
Has anyone ever used a filter? A filter is an object that separates components from a given mixture. Maybe you have used one in class or at home.
Give the students a few minutes to think about this. Filters are in use all around us, every day. Whenever you drink filtered water, whenever you are in a car air filters, oil filters, etc. We are going to study filters that remove salt from saltwater. We are also going to learn about the way our planet naturally produces semi-clean water, and learn about technologies engineers have developed to turn saltwater into safe drinking water.
Show the attached PowerPoint presentation. Then hand out the attached Design a Desalination Plant Worksheet. Following the lesson, conduct the hands-on associated activity Saltwater Circuit to have students learn about its real-world application as a desalination plant tool to test for the removal of salt from ocean water. After practicing the fundamentals of this process, students can then use the associated activity Water Desalination Plant to design, build and test a model saltwater desalination plant, using a saltwater circuit to test its success in removing salt from the water.
To produce water suitable for drinking and irrigation, water desalination removes salt and minerals from seawater. The natural version of this process is the water cycle. Two fundamental human-made desalination methods are thermal technologies and membrane technologies.
Natural Water Desalination the Water Cycle — Water is the only substance that can exist as gas, liquid and solid in the naturally occurring temperature ranges on Earth. In fact, in some instances in the natural environment, water can be present in all three phases.
The amount of water on our planet stays approximately constant, which means that the amount of water on our planet today is the same as the quantity present during the age of the dinosaurs. The water on Earth plays a major role in the naturally occurring phenomena called the water cycle , which can be described by four major steps: evaporation, condensation, precipitation and collection:.
During the hydrologic cycle, water that evaporates from the ocean leaves its salt content behind because the salt in the water does not evaporate. So, the water cycle is, in essence, filtering saltwater, creating freshwater for the natural irrigation of plants, trees and crops.
Human-Made Desalination Systems — Engineers are challenged to develop cost effective ways to produce large quantities of water suitable for drinking and crop irrigation for regions of the world that suffer from water shortages.
Water desalination is expensive, requiring large amounts of energy and specialized equipment to convert saltwater into drinking water. Thermal Desalination: This approach involves heating saltwater until it evaporates and then forcing the evaporated water to condense. The condensed water is clean water. This approach mimics the water cycle; in fact, each step in a thermal process can be linked to a stage of the water cycle.
An example:. Membrane Desalination: This approach is the least expensive and works by forcing water through membrane sheets that prevent large saltwater molecules or ions from passing through the membrane. Two examples:. Both of these desalination techniques produce clean water for human consumption, but they also produce a waste product called brine. Brine is a sludge that has high concentrations of salt.
We can view processes, such as saltwater desalination, as objects composed of systems that perform certain tasks to achieve a desired goal. A system is an object that receives inputs and transforms it into output s. Systems are all around us and can be viewed both high- and low-resolution levels. For example, when listening to music on an MP3 player, the user selects a song, hits play, and music comes out of the speakers; this is a low-resolution view of the system that produces music from audio data files see Figure 1.
A high-resolution view of the same system might be: the user selects a song, hits play, data is converted from digital to analog format, and music comes out of the speakers.
This second description provides more information and is, therefore, considered a higher-resolution view of the system that produces music from audio data files see Figure 2. Figure 1. An MP3 audio player system diagram low-resolution view. Both of these system descriptions can be easily sketched as a system diagram. A system diagram is a box diagram with labeled inputs and outputs see Figures 1 and 2.
System diagrams are typically a first step in engineering design and analysis, helping engineers get an understanding of the flow of a system. Figure 2. An MP3 audio player system diagram higher-resolution view. Although the word "system" typically refers to something electrical or mechanical, systems are all around us. From the process in which you get dressed in the mornings, to the way you cook dinner in the evenings, any process can be viewed from a "systems perspective.
Watch this activity on YouTube. So how dirty is dirty before you decide you cannot drink water? Does the water have to be clear or can it be kind of cloudy? Give the students a minute to think about this. Home » Solutions » Desalination » What is Desalination?
Reverse Osmosis RO desalination uses the principle of osmosis to remove salt and other impurities, by transferring water through a series of semi-permeable membranes. Thermal desalination uses heat, often waste heat from power plantsor refineries, to evaporate and condense water to purify it. In the most advanced desalination plants, such as those built by IDE, water is pretreated in order to improve the efficiency of the plants.
RO desalination technology was initially developed in the late s, and has now evolved into the leading desalination technology globally. There are many different processes used in RO desalination, and a variety of factors come into play when selecting the appropriate solution for each situation — the quality of the source water, the desired quantity and quality of the water produced, pretreatment, energy requirements and disposal of concentrate.
RO can remove many types of molecules and ions, making it suited for potable and industrial uses. Standard osmosis involves a solvent such as water naturally moving from an area of low solute concentration, through a membrane, to an area of high solute concentration. The movement of a pure solvent reduces the free energy of the system by equalizing solute concentrations on each side of the membrane, generating osmotic pressure.
Applying an external pressure to reverse the natural flow of solvent is called reverse osmosis. To create clean water using this process, seawater or brackish water is pressurized against one surface of the membrane, causing salt-depleted water to move across the membrane, releasing clean water from the low-pressure side.
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