NCWR

About NCWR

Wastewater treatment

In a nutshell

In this activity we are informed about the treatment process of the urban wastewater and why this is considered as an important non-conventional water resource.

A school day

12-13 years old

In the field

Our objectives

In this activity you will:

  • Differentiate between ‘black’ and ‘grey’ water.
  • Be informed about the steps followed in a wastewater treatment plant.
  • Find out the uses of the treated wastewater.

Things to use

Notebooks and pens, photo camera

Play & Learn

Black water VS greywater

Have you ever heard of the terms “black water”and “grey water”? What is the difference between them?

Water-readings

The wastewater treatment process

The municipal wastewater of a city is led to to the wastewater treatment plant through the sewage system. There wastewater undergoes certain processes:

  1. Screening: The sewage is led to tanks with large vertical grates (like huge combs) that hold large solids (e.g. pieces of plastic, wood, cloth, etc).
  2. Primary settlement:The sewage is lead to these tanks to allow the heavier particles to settle in the bottom of the tank, as sludge.
  3. Secondary or biological treatment: The overflowing liquid moves on to the aeration tanks, where the microorganisms contained in it, with the help of the oxygen (aeration), grow rapidly and feed on the organic substances. As they grow, microorganisms tend to join with each other, creating flocks.
  4. Secondary settlement: The effluent is led to tanks and the remaining solids – sludge together with flocks of microorganisms- settle down. In fact, a part of them is sent back to the aeration tank to “help” microorganisms to consume the organic matter. The overflowing liquid is free of organic substances.
  5. Disinfection: To make sure no microorganisms are left in the recovered water, a disinfection is usually done through adding chlorine.

Stop and wonder

The “recovered” water (water resulting from the wastewater treatment) is usually led to a water body (sea or river) without causing risks of contamination or pollution. However, this practice is a big waste, since this water is suitable for various uses, after some further treatment (polishing)  to meet certain quality criteria. For example, it can be used to water the parks of a city, or some crops, as well as for cooling purposes in factories. In addition, the sludge produced during the wastewater treatment can be used as a fertilizer or fuel.

DID YOU KNOW THAT ?


  1. Municipal wastewater treatment is mandatory for EU countries and many Mediterranean countries. What about your country?
  2. Large industries and enterprises (e.g. hotels) are in many countries obliged to process their own wastewater.
  3. There is a Mediterranean country that uses  80% of the recovered wastewater for irrigation in agriculture. Which one?
    We give you an hint: while this country is almost arid, it has developed such a technology that it gradually turns the desert into arable land; it actually exports a lot of its produce to Europe and elsewhere!

 

Play & learn

Based on what you have read in the previous section drag and drop the processes of the wastewater treatment with their proper place in the image.

 wastewater-treatment quiz-hotspot
1
2
3
4
5
6
7
8
9
10
  • 1 1 intake
  • 2 2 screening
  • 3 3 primary settlement
  • 4 4 secondary/biological treatment
  • 5 5 sludge treatment (digestion)
  • 6 6 secondary settlement
  • 7 7 tertiary settlement
  • 8 8 disinfection
  • 9 9 irrigation with the recovered water
  • 10 10 discharge of the recovered water to the sea

Group activity

Visit to the wastewater treatment plant

Organise a visit to the wastewater treatment plant of your area and collect information about the processes included.

Before your visit:


Observe on the map the area where the wastewater plant is located. Why do you think the particular location was chosen?

During your visit:


  1. Keep notes  and take photos of all the stages.
  2. Do you find any differences between this plant and the general one described in the Water Readings? Is there any step ‘missing’ or ‘new’?
  3. Ask the staff where the recovered water ends up e.g. to the sea or a river  or is it used for a certain purpose (if yes, which one)?
  4. Try to collect information about the sludge produced as well, if it is used somehow.

Water meter

Provided that all quality regulations are followed during the wastewater treatment, how much do you agree with using the recovered water...
not at all a little so and so very much totally
for watering the parks and golf courses

to fertilize tree crops e.g. orange trees, olives

for watering the school yard

for toilet flushing

for cooling purposes in the factories

Water meter

I liked this activity .. .

Way forward

Dive in…

Rainwater harvesting   

Do you know about grey water?   

Desalination

if you want to  know about other non-conventional water resources.

Go back to the homepage!

Acting for Climate

Water works through time

Water in the city

The water basins

Desalination

Greywater recycling in practice

Do you know about grey water?

Wastewater treatment

Rainwater Harvesting Systems in practice

Rainwater harvesting

Reduce-Reuse-Recycle

Climate change: Why should I care?

Water resources

The water cycle

Where do I begin?

Acting for Climate

What are the main sectors contributing to climate change? What are countries doing to address it? What can we do for climate collectively at school and at community level?

Continue!

Water works through time

Let's discover the story behind the old fountains, cisterns and aqueducts of our town!

Continue!

Water in the city

What is the "urban water cycle"? Which are the important aspects of water management within a city environment?

Continue!

The water basins

In this activity we learn what a water drainage basin is and why it is important for the experts to study it.

Continue!

Desalination

Let's find out how sea and brackish water can become a freshwater resource!

Continue!

Greywater recycling in practice

How a greywater system is installed? Let's find out!

Continue!

Do you know about grey water?

Let's find out what "greywater” is and how we can use it!

Continue!

Wastewater treatment

In this activity we learn about how wastewater is treated and what we can do with the treated water.

Continue!

Rainwater Harvesting Systems in practice

What are the various types of rainwater harvesting systems? Let's find out more about them!

Continue!

Rainwater harvesting

Can we collect rainwater? And how do we use it? Let's find out!

Continue!

Reduce-Reuse-Recycle

What is our water footprint and how can we reduce it?

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Climate change: Why should I care?

We discuss the greenhouse effect and the greenhouse gases, how climate change is linked to our lifestyles and ways we can cope with it on a personal level.

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Water resources

Lt's discover the water resources of our region.

Continue!

The water cycle

Let's travel within the water cycle!

Continue!

Where do I begin?

Let's see why it is important to know about water in our region.

Continue!