Municipal Water and Wastewater treatment

Magic!!!

Magic!!!

Magic?

Not really

I come from a RIVER in your state

Magic? I come from a LAKE or a RESERVOIR close to your city

I come from deep UNDER THE GROUND. Groundwater is relatively cleaner and does not

require the entire treatment process. It may only need to be treated for chemical

contamination.

I come from the SEA….but what follows is not my story, because I go through a different

path before I reach you.

A big 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 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?

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

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

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

Flocculation

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

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

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’

Sedimentation

Rapid sand filtrationWe 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

Chlorination

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

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

We then travelled a large distance

through pipes

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

to large tanks within your city

And from there to overhead tanks near your school

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

We got to your school this morning and here we come…….. Out of your tap

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

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/

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/

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/

AerationAir 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

A recap – water purification

Primary Filters (to remove large matter)

Flocculation tank

Sedimentation tank

Rapid / slow sand filtrationChlorination

Water from rivers / lakes

To tanks in the city

A recap – waste water treatment

Grit Filters (to remove large

matter)

Sedimentation tank

Trickling filter

AerationSecondary filters

Wastewater from city

To streamTertiary

treatment