Bovril boats, also known as sludge vessels, were specially designed sewage dumping vessels that operated on the River Thames from 1887 to 1998. Their task was to remove London's sludge waste from Beckton and Crossness for disposal on the ebb tide at sea, at Black Deep, an extremely deep part of the North Sea located fifteen miles off Foulness, on one of the main approaches to the Thames Estuary. Similar boats operated on the Manchester Ship Canal and the Tyne.
The invention of the flush toilet in the 1840s caused London's sewers to overflow. In 1858 following the summer of The Great Stink and outbreaks of cholera, Sir Joseph Bazalgette was appointed to redesign London's sewage system. He was only partially successful however as the sludge part of the sewage began to build up on mud banks further down stream along the Thames. In 1878 the passenger steamer The Princess Alice sank in a collision with great loss of life. When the dead were later recovered by watermen, it was found that many had in fact not drowned, but had died from ingesting the poisoned waters of the toxic sludge filled river.
A Royal Commission of 1882 concluded that it was necessary to create a cleaner river by separating the sludge part from the liquid sewage and remove it via boat for disposal at sea. In 1887 the first ship of a long line of 'pump and dump' effluent tanker vessels was launched. These ships, later nicknamed Bovril boats to describe their liquid cargo by those who crewed them, were very well maintained and specially designed for marine disposal. Complex hydrostatic calculations had to be made when carrying liquid cargo but crews could expect reasonably good pay and regular work. The last of the fleet were: Bexley, Hounslow, and Newham, all named after London Boroughs.
European Union legislation
In the 1990s, European Union legislation forbidding the dumping of sewage at sea and popular environmentalism's concerns that sewage was contaminating beaches led to the phasing out of the fleet and many were scrapped or sold on to private companies. Newer technology  finally allowed the sludge to be incinerated in a self-powering incinerator and sold on as fertilizer pellets for use on food crops.
- Bentwich, Helen (1962). Our Councils, The Story of Local Government. Routledge and Kegan Paul Ltd. p. 19.
- National Research Council (U.S.). Committee on a Multimedium Approach to Municipal Sludge Management, United States. Environmental Protection Agency (1978). Multimedium management of municipal sludge: a report to the U.S. Environmental Protection Agency. National Academies Press. p. 40.
- History: https://web.archive.org/web/20071008144122/http://www.portcities.org.uk/london/server.php?show=ConNarrative.153&chapterId=3192