Pipes! Fatbergs! Chemistry!

Hey all,

One of my freetime interests is in pipes. When I was a kid, like maybe 5, my father was an engineer working on the country’s nuclear power plant. This had to do with a lot of printing and so where’s other 5 year olds were colouring pictures of animals, I was colouring cooling systems diagrams. I blame this for my fascination with pipes. The odds of someone else sharing this interest are probably exactly zero, but you never know right?

So, let’s start with something epic. How can sewage be epic you ask? Well, like this:

…this tank is capable of containing 13 giga-litres of sewage (13000000000 l). It fills up when it’s raining (and there is snow melt), so that’s why the camera is wet. Here’s a construction phase picture of the pipes that lead into it:

Feel sorry for the people who live in that town tho. That much sewage can’t smell nice no matter how well executed the containment is.

The truth is, as counter-intuitive as that may sound, sewage and water don’t mix. From the microbiological perspective, water makes it difficult for oxygen to reach the organic compounds and so their degradation slows, or the sewage becomes infested with microbes that do not use oxygen, producing a foul smell. Thus, as much as I admire the americans that built this fancy giga-litre storage tank, it’s fundamentally a bad idea. I do understand that they have no other way to really solve the issue though. It’s not like people are going to give up flush toilets to help them do it.


One of the more easier to get to videos about the sewers is this stuff pushed by the BBC:

What you have here is people who have no idea what they are talking about, sounding authoritative, because that’s just the way the BBC rolls. That stuff is not fat, it’s calcium soap.

Some searching online, will lead you to several research articles, there’s actually only a few (unsurprisingly not many scientists are interested in what goes on in the sewers). What happens is when sewage travels along the sewage network too far, it begins to decompose on route to the treatment plant. The microbes growing in it start to produce sulphuric acid, which eats away at the concrete pipes that the sewage is flowing through. This causes calcium and similar minerals to leech from the concrete, which when they come into contact with fresh water and fats from buildings further down the network, produces this calcium soap, which unlike normal soap is not water soluble and deposits in the pipes.

But, so you may say, the BBC is still correct in saying that this is because people are dumping oils into the sewers? Well, not really. Fat in the sewers is not just dumped oil, it’s also basically anything you use soap or dish soap for. Research shows that normal domestic outputs like sinks and showers from a single skyscraper, contribute enough fat to create a problem. The grease interceptors that they have been promoting as a result of this fatberg problem (which are a good idea by the way, EU requires them to be installed in basically every parking lot), actually lengthen the amount of time that the fats spend in the water and increases the amount of problematic compounds in the sewage.

In other words, carrying fats is the basic and unavoidable function of sewers, and the BBC is fooling you into believing it’s your fault that the sewers are incorrectly designed. But oh their glorious engineers from the 60s’! Infallible!


Didn’t really want to turn this into a rant, but hey it’s my blog! Deal with it!

Just kidding. Hope you learned something. Anything you may be wondering about, feel free to drop a comment.


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