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Water used for washing clothes may be used to clean toilet.

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Reduce

Repair

Re-use

3 R’s to save water

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Experiments with water

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Physical properties of water

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Dead sea

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Location of dead sea

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Municipal Water and Wastewater treatment

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Magic!!!

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Magic!!!

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Magic? �

Not really

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I come from a RIVER in your state

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Magic? �

I come from a LAKE or a RESERVOIR

close to your city

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I come from deep UNDER THE GROUND.

In the river bed and other places,

there are borewells through which

I come out during the

summer months

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I come from the SEA….

but what follows is not my story,

because I go through a different

path before I reach you.

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A big pipe sucked us in

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Along the way, there was a mesh

We could go through but 3 friends of

ours (pebble, stick and leaf) couldn’t make it.

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A pipe sucked us in

Along the way, there was a mesh.

We could go through but 3 friends of

ours (pebble, stick and leaf) couldn’t make it.

A pump pushed us a long distance until we reached this big factory like place called ‘Water treatment plant’

There were boards all around which said

‘Restricted Area’.

I wonder why. Do you know?

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Flocculation

From a dark gloomy pipe where we were really rushed,

we reached a BIG tank.

When we were resting, something called

Aluminium Sulphate (let’s call him ALUM ) and some of his friends joined us.

Flocculation is a process which removing any turbidity or colour in the raw water so that it is clear and colourless. This is done by causing a precipitate to form in the water which can be removed using simple physical methods. Ferric Chloride or Aluminium sulphate is added to the raw water along with a polymer that acts as a catalyst. A very small quantity of the polymer is required. These form sticky particles called ‘floc’ which attract colloidal and other particles suspended in water. Initially the precipitate forms as very small particles but as the water is gently stirred, the ‘floc’ particles along with the suspended colloidal particles stick together to form bigger particles - this process is called flocculation or coagulation. The combined weight of the dirt and the alum (floc) become heavy enough to sink to the bottom during sedimentation.

During the flocculation process, colloidal particles that are very difficult to settle by gravity can be removed. The positive and negative ions coalesce and the chemicals hasten this process. The colloidal particles also carry bacteria. The churning process helps to spread the chemicals across the flocculation tank.

Before the chemicals are added to the flocculation tank, a lab (jar) test is done, which tells us the different dosages and normalities of chemicals required for flocculation.

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Flocculation

Alum and his friends are very sticky and my pals ‘Dirt’ from the river, who managed to pass the mesh earlier on, got really attracted to them.

Flocculation is a process which removing any turbidity or colour in the raw water so that it is clear and colourless. This is done by causing a precipitate to form in the water which can be removed using simple physical methods. Ferric Chloride or Aluminium sulphate is added to the raw water along with a polymer that acts as a catalyst. A very small quantity of the polymer is required. These form sticky particles called ‘floc’ which attract colloidal and other particles suspended in water. Initially the precipitate forms as very small particles but as the water is gently stirred, the ‘floc’ particles along with the suspended colloidal particles stick together to form bigger particles - this process is called flocculation or coagulation. The combined weight of the dirt and the alum (floc) become heavy enough to sink to the bottom during sedimentation.

During the flocculation process, colloidal particles that are very difficult to settle by gravity can be removed. The positive and negative ions coalesce and the chemicals hasten this process. The colloidal particles also carry bacteria. The churning process helps to spread the chemicals across the flocculation tank.

Before the chemicals are added to the flocculation tank, a lab (jar) test is done, which tells us the different dosages and normalities of chemicals required for flocculation.

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Flocculation

Alum and friends, along with ‘Dirt’ stuck together. We called them ‘FLOC’

Flocculation is a process which removing any turbidity or colour in the raw water so that it is clear and colourless. This is done by causing a precipitate to form in the water which can be removed using simple physical methods. Ferric Chloride or Aluminium sulphate is added to the raw water along with a polymer that acts as a catalyst. A very small quantity of the polymer is required. These form sticky particles called ‘floc’ which attract colloidal and other particles suspended in water. Initially the precipitate forms as very small particles but as the water is gently stirred, the ‘floc’ particles along with the suspended colloidal particles stick together to form bigger particles - this process is called flocculation or coagulation. The combined weight of the dirt and the alum (floc) become heavy enough to sink to the bottom during sedimentation.

During the flocculation process, colloidal particles that are very difficult to settle by gravity can be removed. The positive and negative ions coalesce and the chemicals hasten this process. The colloidal particles also carry bacteria. The churning process helps to spread the chemicals across the flocculation tank.

Before the chemicals are added to the flocculation tank, a lab (jar) test is done, which tells us the different dosages and normalities of chemicals required for flocculation.

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Flocculation

Alum and friends, along with ‘Dirt’ stuck together. We called them ‘FLOC’

Flocculation is a process which removing any turbidity or colour in the raw water so that it is clear and colourless. This is done by causing a precipitate to form in the water which can be removed using simple physical methods. Ferric Chloride or Aluminium sulphate is added to the raw water along with a polymer that acts as a catalyst. A very small quantity of the polymer is required. These form sticky particles called ‘floc’ which attract colloidal and other particles suspended in water. Initially the precipitate forms as very small particles but as the water is gently stirred, the ‘floc’ particles along with the suspended colloidal particles stick together to form bigger particles - this process is called flocculation or coagulation. The combined weight of the dirt and the alum (floc) become heavy enough to sink to the bottom during sedimentation.

During the flocculation process, colloidal particles that are very difficult to settle by gravity can be removed. The positive and negative ions coalesce and the chemicals hasten this process. The colloidal particles also carry bacteria. The churning process helps to spread the chemicals across the flocculation tank.

Before the chemicals are added to the flocculation tank, a lab (jar) test is done, which tells us the different dosages and normalities of chemicals required for flocculation.

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Flocculation

We were then stirred and churned around and the ‘FLOC’ started getting bigger with more dirt sticking around.

We also saw many more ‘flocs’ forming

Flocculation is a process which removing any turbidity or colour in the raw water so that it is clear and colourless. This is done by causing a precipitate to form in the water which can be removed using simple physical methods. Ferric Chloride or Aluminium sulphate is added to the raw water along with a polymer that acts as a catalyst. A very small quantity of the polymer is required. These form sticky particles called ‘floc’ which attract colloidal and other particles suspended in water. Initially the precipitate forms as very small particles but as the water is gently stirred, the ‘floc’ particles along with the suspended colloidal particles stick together to form bigger particles - this process is called flocculation or coagulation. The combined weight of the dirt and the alum (floc) become heavy enough to sink to the bottom during sedimentation.

During the flocculation process, colloidal particles that are very difficult to settle by gravity can be removed. The positive and negative ions coalesce and the chemicals hasten this process. The colloidal particles also carry bacteria. The churning process helps to spread the chemicals across the flocculation tank.

Before the chemicals are added to the flocculation tank, a lab (jar) test is done, which tells us the different dosages and normalities of chemicals required for flocculation.

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Sedimentation

We were then pushed into another tank. Ah! Rest at last.

This was called the sedimentation tank. Hey! the flocs are sinking.

The big ones are going down first.

Our friend ‘Dirt’ has gone down too with his ‘floc’

We were in this tank for about 2 hours and by then all the flocs had sunk down below and formed a gooey mass called ‘sludge’

Water exiting the flocculation basin may enter the sedimentation tank, also called a clarifier or settling tank. It is a large tank with slow flow, allowing floc to sink to the bottom. The sedimentation tank is best located close to the flocculation tank so the transit between does not permit settlement or floc break up. Sedimentation tanks can be rectangular, where water flows from end to end, or circular where flow is from the centre outward. Tube settlers are much faster. Sedimentation tank outflow is typically over a weir so only a thin top layer - furthest from the sediment - exits. The amount of floc that sinks is dependent on the time the water spends in the tank and the depth of the tank. The typical clarifier retention time is 2 – 2.5 hours. A deep tank will allow more floc to settle out than a shallow tank. This is because large particles settle faster than smaller ones, so large particles bump into and integrate smaller particles as they settle. In effect, large particles sweep vertically though the tank and clean out smaller particles on their way to the bottom.�As particles settle to the bottom of the basin a layer of sludge is formed on the floor of the tank. This layer of sludge must be removed and treated. The amount of sludge that is generated is significant, often 3%-5% of the total volume of water that is treated. The cost of treating and disposing of the sludge can be a significant part of the operating cost of a water treatment plant. The tank may be equipped with mechanical cleaning devices that continually clean the bottom of the tank or with hopper bottoms which can open out.

(source: Wikipedia: http://en.wikipedia.org/wiki/Water_purification)

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Rapid sand filtration

We then passed quickly through another tank with a layer of sand and gravel

Little flocs and some dirt that did not get into flocs, got trapped in the sand

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Chlorination

A small amount of chlorine was then added to our tank, which killed pathogenic bacteria, protozoa, viruses, helminths and other micro organisms.

http://www.cpcb.nic.in/oldwebsite/New%20Item/status-WTP-In-India/Chapter1%20.rtf will give you some more information on municipal water treatment systems in India

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We then travelled a large distance �

Photo by C C Krause; Source: http://www.flickr.com/photos/charleskrause/3185090628/

through pipes

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to large tanks within your city

Photo by John Brian Silverio; Source: http://www.flickr.com/photos/psilver/2280385292

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And from there to overhead tanks near your school

Photo by BockBilbo; source: http://www.flickr.com/photos/bockbilbo/247405160/

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We got to your school this morning and here

we come…….. Out of your tap

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Waste water treatment

Once you wash your hands with us or flush us down the toilet, we go down through the drains of your school, and through bigger drains under your city and reach a waste water treatment plant.

Our story doesn’t end here

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This is what we look like when we reach the wastewater treatment plant

We’re full of poop, soap, oil, grease, soil, garbage, chemicals….all kinds of stuff

Photo by flippy rice; Source: http://www.flickr.com/photos/flippy/110659044/

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Sedimentation

All the solid stuff is separated out

We then go to sedimentation tanks where the sludge settles down and oil and grease float on top.

Both these are removed

Photo by Benjamin Pender; Source: http://www.flickr.com/photos/benpender/2432095138/

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Trickling Filter

We trickle on to a bed of rocks and gravel on which a layer of microbes are present.

Bacteria, protozoa and fungi on this bed

eat up the organic matter in the sewage

Photo by Naturenet; Source: http://www.flickr.com/photos/naturenet/199836849/

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Aeration

Air is pumped through us in aeration tanks

We may go through another round of the trickling filter

Sometimes we go through a tertiary treatment system where chemicals are added to purify us

Then we rejoin a stream

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A recap – water treatment

Primary Filters (to remove large matter)

Flocculation tank

Sedimentation tank

Rapid / slow sand filtration

Chlorination

Water from rivers / lakes

To tanks in the city

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A recap – waste water treatment

Grit Filters (to remove large matter)

Sedimentation tank

Trickling filter

Aeration

Secondary filters

Wastewater from city

To stream

Tertiary treatment

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Activity

Organize a field visit to a water or wastewater treatment plant

Have the students work on a bulletin board with their thoughts on the visit

How much energy do they think is required to bring us our water and treat our waste water