Let's become Water Scientists

Hello kids! Welcome to the world of water science.

Water is one of the basic needs for us to survive and it is our responsibility to make sure that we consume good and healthy water.  Fascinating as it sounds, it is also equally fun to learn about the water supply, the different villains who could harm us and also how to remove these villains from water before consuming them.

The important part is that you learn about water and you enjoy doing it!

Let's become water scientists!!!..





"Financed by the European Union: The research leading to these results has received funding from the European Community's Seventh Framework Programme under grant agreement no 308496. The opinions proclaimed on this web site are not necessarily those of the EU, but are the consortium's own."


Where does water come from?

What are water sources?

How you ever wondered... where does the water you drink come from? or How is your house supplied with water? 

It is important to know where you get your water from because this defines the purity and the quality of the water you use. Even though 3/4th of the earth is filled with water, only 3% is freshwater. Over 60% of this fresh water exists in the form of ice and the little freshwater left is often even not drinkable without treatment. Shocking! isn't it.

Let's start our journey by learning more about these water sources...

Water Sources

This is our first step toward becoming a water scientist. Water sources are found all around us, and choosing a correct treatment for any type of water source is very important. To choose the treatment method we have to know what contaminants are there in that source and treat for it. Our scientists here are very excited to teach you about the different water sources.

Click and chat around with him and discover more fun facts about water source! and submit it once you are sure with the topics or you do not want to go through it again. Have fun!

What Percentage of the Earth's water is fresh?

  • 10%
  • 3%
  • 56%
Choose one of the options below.

What is the chemical symbol for water?

  • NaCl
  • H2O
  • H2SO4
Choose one correct option.

What is the process by which rainwater enter the ground to form the water table?

  • Perspiration
  • Evaporation
  • Percolation
  • Condensation
Choose one correct option.


Name any three oceans name that you learned from the course.

How can your access groundwater?

  • Wells
  • Bottles
  • Tubes
  • Evaporation

Water Processes

Match the term with its definition
  • Percolation
    The process of water penetrating through the earth soil.
  • Evaporation
    The change of water into water vapour through the process of heating
  • Condensation
    The process of cooling water vapour into liquid water.
  • Precipitation
    The pouring down of heavy clouds with water or snow.

Water cycle processes

  • Evaporation
  • Condensation
  • Precipitation
Arrange the following process in their order of occurrence in the water cycle starting from the ocean.

Name any 2 contaminants found in surface water?

Who is lying?

  • 80% of the Earth’s surface is covered with water
  • The ocean is the largest water source
  • A well is a manmade structure to access surface water
  • Ground water do not have any water contaminants
  • River is a surface water source
These are some statements made by our scientists, but some of them are lying. Can you figure out who is telling the truth and which statements are false?

The villains in water

Water Contaminants

The water world is filled with many bad guys who want to harm humans and other animals once they consume them. These bad guys are responsible for making us fall sick, vomiting etc.

Let us do a little research about these bad guys and see their effects on human bodies so that we can catch them and bring an end to them by water treatment methods.

Water Contaminants

Why is this glass of water brown?

  • Virus
  • Bacteria
  • Dirt
  • Chlorine

Disease detectives

Match the contaminant name with its disease.
  • E. coli
    Stomach infection
  • Salmonella typhi
  • Vibrio cholera
    Cholera disease
  • Poliovirus

Match the villians with their crime

Drag the names of the virus or bacteria and drop it on the respective images.
  • E-Coli
  • Thyphi
  • Hepatitis A
  • Polio Virus

The court of justice

What would you do if people come with water affected from..
  • Virus
  • Bacteria
  • Dirt
  • Salt

The water doctors

Water treatment methods

I am sure now you are familiar with where water comes from and what are the different contaminants that could be present in water that could harm our health or even threaten our life. Therefore, the water world really needs your help to destroy this evil to save humans!
To the laboratory!!!

However, if you have no idea what I am talking about I highly recommend you to go through 'Where does water come from?' and 'The villains in water' sections of this course. Our experts will teach you about the topics.

What do water doctors do?

The main objective of the water doctors would be to treat the water for:

  • microorganisms/pathogens (bacteria, virus, protozoan, parasites)
  • solid/dirt particles and chemicals.

There are many ways of doing this, some most known methods that we will learn about are:

  • Disinfection
  • Filtration
  • Desalination

To the laboratory!!!!..

Water disinfection

Water disinfection means the removal, deactivation or killing of pathogenic microorganisms which cause harmful diseases when consumed.  The two most common disinfection methods are:

  1. Thermal disinfection (boiling)
  2. Physical disinfection ( UV, solar/sunlight)
  3. Chemical disinfection (Chlorine, ozone)

Lets go to the disinfection lab to see how this works..









Boiling is the physical process by which the water is heated to the boiling point to change the state of water to water vapour. The boiling point of water is at 100 degrees celsius at normal atmospheric pressure.

This is the most easiest and cheapest method of water treatment. Most moms use this water treatment in their house to protect their children from virus and bacteria.



How boiling helps in water treatment


So the next question would be how such a simple process helps in water treatment?

Water is heated up to a minimum temperature of 60-75°C or even to the boiling point of 100°C during this water treatment process.

When the water is boiling bubbly for min. 3 minutes most of the bacteria and virus present in water will be inactivated (cannot reproduce) and will be killed. This makes water microbiologically safe for drinking, but does not have any effect on harmful chemicals or dirt which might be present in the water too.

Boiling is a domestic water treatment method for a small water demand, but it is not preferred to treat a large quantity of water (for example for the public water supply), as it needs a lot of time and fuel.

The boiling exam

Boiling is the process of ​ water upto a minimum of  so that  are killed by making them . This process is very common in  as it is very cheap and easy.

Solar disinfection


The ultraviolet spectrum of the sunlight (UV-A rays) is able to kill pathogens. In order to treat water for microbiological contamination it can be filled into PET or glass boltless (max. 3 liter volume, (smaller volume is better) and exposed to the sunlight for minimum 6 hours (at full sunshine).



This simple treatment process is perfect for domestic use and has the highest efficiency on strong sunshine, high temperatures and clear (not turbid) water. If the weather is a little cloudy, it is recommended exposing the water bottles to the sun for around 2 days. 

Ultraviolet disinfection

UV-disinfection can be also applied by using electrically powered UV-lamps with a very high concentration on UV-C rays. These lamps are very efficient in order to treat any quantity of water in a very short time. Therefore they are used on domestic level as well as on the scale of public water supply in big treatment plants. This treatment process also works best with clear (not turbid) water. Bacteria and virus in dirty water might not be killed sufficiently, because they can hide from UV-rays behind the dirt particles.

The biggest advantage of UV-disinfection is its chemical free operation and high efficiency on microorganism (some of them are already resistant to disinfection chemicals).


Chemical treatment

Water can also be effectively disinfected with chemicals like chlorine, iodine and hydrogen peroxide. These chemicals are available in liquid or tablet form and are very inexpensive and easy to carry.

When using chemicals for water disinfection it is very important to dose them accurately and to adhere to the safety instructions handling and storage of the respective chemical.   

How does chemical treatment work?

The most typical chemical used for water disinfection is chlorine or hypochlorite. A safe disinfection should have a minimum of 20 minutes reaction time, using a concentration of max 0.5-1.0 mg of this chemical per liter water.  During disinfection the chlorine will be partially consumed and after disinfection its concentration should not exceed 0.1-0.3 mg per liter water. This treatment process also works best with clear (not turbid) water. Bacteria and virus in dirty water might not be killed sufficiently, because dirt and organic material will also consume the chlorine.

The biggest advantage of using a chemical like chlorine is that is has a lasting (residual) effect which avoids the recontamination of the disinfected water, once it get in contact with contaminative source like a dirty piping systems, dirty water storages or dirty water bottles.

Who is lying?

  • Disinfection do not remove dirt particles
  • Sunlight do not ultraviolet spectrum
  • Microorgainisms are removed during disinfection process
  • The UV radiation affects the DNA of the microorgainisms
  • Disinfection do not treat for bacteria


Membrane Filtration

Filtration is a mechanical or physical operation which is used for the separation of solid particles (like dirt, chemicals and even micro-organisms) from water by forcing it to pass through a porous medium through which only water can pass.

There are many different types of filters using for instance granular filter media, plastic and metal strainers, clothes and fibres or even membranes made from plastic or ceramics.  

Sand filter(media filter)

When water flows through the porous sand, the most particulates will be captured between the grains. There are two different types of sand filters. Rapid sand filters, which are very effective in terms of time but usually followed by additional treatment steps and slow sand filters, which are very effective in terms of water quality and able to produce even pathogen-free water. 

Ever wondered why aliens abduct cows? This is why.


Video credits: gobalize-this.org

Carbon filters

Carbon Filtering

Carbon filtering is a method of filtering that uses a bed of activated carbon to remove contaminants and impurities. Activated carbon works via a process called adsorption, whereby pollutant molecules in the fluid to be treated are trapped inside the pore structure of the carbon substrate.

Active charcoal carbon filters are most effective at removing chlorine, sediment, volatile organic compounds (VOCs), taste and odor from water. They are not effective at removing minerals, salts, and dissolved inorganic compounds. Typical particle sizes that can be removed by carbon filters range from 0.5 to 50 microns. The particle size will be used as part of the filter description. 


Membrane filter

Membrane filtration is a physical water treatment process driven by pressure. In this process water can flow through a membrane with a specific size of small pores, while suspended solids and other substances will be filtered out. Depending on its pore-size the membrane is able to retain dirt, bacteria, virus or even minerals and salt from the water. 



Desalination is a process that removes minerals from saline water. Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. One potential by-product of desalination is salt.

Usually desalination is applied by thermal processes (distillation = evaporation and condensation – similar to the formation of rain) or membrane filtration processes

Reverse osmosis

Reverse osmosis is a membrane filtration process using a membrane with very small pores. These pores are that small that they are even able to filter dissolved elements like minerals or salt or other harmful chemicals like arsenic or fluoride. 

The reverse osmosis membrane is as explained by the video:

Source: SydneyWaterTV

How exactly is the process done?


Source: SydneyWaterTV

Treatment scientist

These are the drawings from our little scientists who are trying to depict different water treatment process. Would be able to crack their code?

Try matching the words with the images.

  • Filtration
  • Solar Disinfection
  • UV Disinfection
  • Chemical Disinfection
  • Reverse osmosis
  • Boiling

Water treatment plant

A water treatment plant is the combination of different water treatment methods. As you would have guessed from the previous videos a single treatment method can be coupled with other to remove more contaminants. For example, filtration removes dirt and large particles and UV disinfection removes microorganisms

Also, some methods can depend on other treatment methods for improved efficiency. For example, before membrane filtration or reverse osmosis large particles like rocks and leaves which can tear the membrane should be removed by mesh filter.

Here is an example of UV-Purification System..



Real water treatment plant

What you saw before is just a schematics of  a treatment plant. It does not look like a series of boxes but this is how an actual water treatment plant looks like:

Match their super power

We have seen a lot of types of water treatment processes. Would you guess which methods is used majorly or commonly used for which process / contaminant?
  • Reverse Osmosis
    To remove salt from the water.
  • Membrane filtration
    To remove micro or even smaller particles
  • Disinfection
    To kill micro organisms by changing their DNA
  • Mesh Filter
    To filter visibly large particles
  • Boiling
    To kill microorganisms by heat

Clean the water

  • Mesh filter - Removes large particles
  • Membrane filter - Removes small Particles
  • Carbon Filters - Improves taste
  • UV Disinfection - Kills Bacteria and Virus
Awesome! You are already a water scientist now! Just one last task. Based on your understanding of the different process that can be used in the industry how would you arrange the following in the order of stages to treat dirty water?