Fatberg


A fatberg is a congealed mass in a sewer system formed by the combination of flushed non-biodegradable solid matter, such as wet wipes, and congealed grease or cooking fat. Fatbergs became a problem in the 2010s in Britain, because of ageing Victorian sewers and the rise in usage of disposable cloths.

Description

Fatbergs form at the rough surfaces of sewers where the fluid flow becomes turbulent. In pipes and tubes with smooth inner linings, fluid near the containing wall flows only slightly slower than fluid in the central channel of the pipe; thus, the whole volume of fluid flows smoothly and freely. When fluid encounters an obstruction, a resulting swirl of water starts trapping debris.
An obstruction can be any type of rough surface capable of snagging debris. In brick or concrete sewers there may be surplus cement drips, damaged brickwork, or loose mortar joints damaged by frost heave. In any sub-surface pipe, even of the most advanced design, penetration by foreign intrusions such as tree roots is a commonplace cause of a fatberg blockage.
In sewers carrying alkaline fluids, lipids can become calcified and solidify. Comprising not only wet wipes and fat, fatbergs may contain other items that do not break apart or dissolve when flushed down the toilet, such as sanitary napkins, cotton buds, needles, condoms and food waste washed down kitchen sinks. The resulting lumps of congealed material can be as strong as concrete, and require specialist equipment to remove.
In some areas, such as London, fat blocked in a sewer can react with the lining of the pipe and undergo saponification, converting the oil into a solid, soap-like substance.
Grease and fat blockages can cause sanitary sewer overflows, in which sewage is discharged into the environment without treatment. In the United States, almost half of all sewer blockages are caused by grease.
Fatbergs have been considered as a source of fuel, specifically biogas. Most of the fatberg discovered in Whitechapel in London in 2017, weighing and stretching more than, was converted into biodiesel.
Fatbergs can be mitigated through public awareness campaigns about flushable waste and grease traps for filtration at the source. Campaigns have been launched against wet wipes because of their effect on sewer systems, most notably by Surfers Against Sewage and the Marine Conservation Society, among other environmental NGOs, who called on the UK's Advertising Standards Authority to end “misleading” branding and packaging.

Occurrence

Fatbergs occur in sewer systems around the globe, in cities and smaller towns. Giant fatbergs have blocked sewers in London, New York, Denver, Valencia, and Melbourne.

Etymology

Fatberg is a compound of the words fat and berg, after iceberg. The word was used in 2008 to describe "large, rock-like lumps of cooking fat" washing up on beaches in Wales, and by 2010 was used in reference to sewer-blocking fat deposits in London.
The word was added to Oxford Dictionaries Online in 2015. The term is used by authorities at Thames Water and South West Water, both in southern England.

Notable fatbergs

The 2020 Everything Everything single "Arch Enemy" has the narrator of the song praying to a sentient fatberg, willing it to destroy the world above the sewer it dwells in.