Geograph - photograph every grid square

As part of Open Doors day, Avonmouth Sewage Treatment Works allow the public to look around this site. It serves much of Bristol and the near surrounding area and has to cope with enormous quantities every day, hence the large scale of the various treatment plants. Here a party are being shown the digesters - tanks that are fed the fine solid matter which is 'eaten' by specialised bacterial agents; the resultant products are methane (which is used by electrical generating engines nearby) and a cheap source of farm fertiliser, which is sold locally. See ST5379 : A land of pipes and tanks for another look around.