Waste water treatment

The world's best lake to - to swim in. What a weird creek. I think it's the canal from the new Sewage Treatment Works. Yuck, sewage! And I just swallowed some.

Calm down, Leon! Water from a modern Treatment Works is actually pretty clean. But ... it hasn't always been like that. Once upon a time all the pee and poop from cities and villages ran straight out into the nearest lake or sea.

Fish died. Slimy algae grew. And nobody dared to swim anymore. So in many places people started building large facilities to clean the wastewater. There are many ways to do it.

For that reason, not all treatment works look the same. Let's take a closer look at one of them. We start by flushing something down the toilet. Any volunteers? Ah, here's one!

Exactly! Here's the camera. Now we'll shrink you. Relax, you're going to go water sliding! Superb camerawork!

Nice focus on the poop there. Just imagine, people used to let stuff like that go straight into lakes and oceans. And if they got their drinking water from a lake like that, they could get horrible stomach ailments from the dangerous bacteria. Sewage pipes from a house empty into larger pipes and tunnels, far below ground. Stand by, Yolo!

Now the fun starts. You're about to arrive at the treatment works. At the entrance to the treatment works there's a filter catching large things that definitely should not have been flushed down: Q-tips, tampoons, false teeth, panty hose... The rest runs into a vat that deals with the kind of dirt that doesn't dissolve in water. There, it sits still and calm so the dirty particles slowly sink to the bottom.

Is it smelly? Bring a gas mask next time, then. The next step is a paradise for bacteria. Here they feast on excrement and droppings day and night. This is called biological treatment.

It's the same thing that happens in nature when bacteria deals with dead plants and animals. But here we inject extra bacteria -- and pump in air -- to speed the process up. No, don't be scared. These are friendly bacteria. They consume the organic material dissolved in the water.

The bacteria also deal with the nitrogen compounds that should also be kept away from the lake. Otherwise the lake gets too many nutrients; too much algae will grow; and fish will die. Bacteria eat the nitrogen compounds -- and fart out the nitrogen as gas -- which bubbles to the surface. There it won't do any damage, since most of the air is already made up of nitrogen. See how the dirt and dead bacteria sink to the bottom.

They make a sticky goo called sludge. This is eventually pumped away. Yolo! Ask what happens with the sludge. Aha: "The sludge is dried and then ends up on fields and in forests as fertilizer... " In this vat the substance phosphorus is removed from the water.

The bacteria have already eaten some of it. But now we must get rid of the remainder, because phosphorus would also fertilize the lakes and seas... too much! Here, they add a substance that binds itself to phosphorous and forms clumps that sink to the bottom. This process is called flocculation.

There you go, now the water is almost pure. Sail carefully through the reeds... and watch out for the pike! Wow, that was lucky! Ooowwwww!

What happened? I WAS BITTEN! Aagh, by a huge horrible sea monster!