Have you ever passed your local sewage treatment works and noticed the huge mountain of poo piled up? No, well that’s because there isn’t one!
So what happens to all of the poo that gets separated from waste water in the sewers?
You may be surprised to hear that most of it gets eaten by billions and billions of tiny creatures in the microscopic world, some of these creatures produce gas that can be burnt to produce electricity – poo-power!
Poo-power helps Thames Water to be the largest generator of renewable energy inside of the M25!
In the first stage of the sewage treatment process (after screening and grit removal) most of the solids, which are mainly poo and toilet paper, are separated from the wastewater and is now called sludge. This sludge is then piped into large anaerobic tanks called digesters. In these tanks huge numbers of tiny creatures digest the sludge and produce a range of different gases – very similar to what might happen after a large dinner!
Some of these creatures (called methogens) produce a gas called methane which is collected in giant balloons (called gas bags) and then burnt in gas engines to generate electricity. Thames Water uses this biogas to help power treatment works, any leftover electricity gets exported to the National Grid. Who knows, the computer you are reading this on might actually be powered by electricity generated from one of your own contributions of poo!
After the sludge is digested some material remains, similar to how ash is left at the end of a fire, and this dark brown/black material is called cake. Unfortunately this is not really the sort of cake you would want to eat on your birthday but it is great as a soil improver and used by farmers to fertilise their land.
Some finer bits of poo remain in the wastewater after the first stage of the sewage treatment process, and these are then digested by more microorganisms in large bubbly tanks of chocolate coloured liquid called aeration lanes. Lots of air is pumped into the aeration lanes (hence the name) to help keep the microbes alive and well, ready to feast upon your poo. A third stage is required in the treatment process to return the useful microorganisms back into the aeration lanes so that they can keep on eating more poo.
Thames Water may not have mountains of poo to climb but they do have some very interesting naturally occurring creatures; from tiny bacteria to larger rotifers, water bears and worms. Water bears are so remarkable and interesting that NASA has flown them into space to study!