Fatbergs, the Icebergs of a Wastewater Collection System


Contributed by Phil Vela

The term fatberg was first used in 2008 to describe the "large, rock-like lumps of cooking fat" washing up on beaches in Wales. In 2015 the word was added to the Oxford English Dictionary. In general a fatberg is a rock-like mass of waste matter in a sewer system formed by the combination of flushed non-biodegradable solids, such as wet wipes, and congealed grease or cooking fat. Fatbergs have been around since humans invented sewer systems and date back to Roman times when slaves were used to clean out effected areas. Because most of the mass cannot be seen, the term fatberg is used.

How do they form?

Fatbergs are basically a combination of fats, oils and grease (FOG) that congeal forming solid deposits in the collection system or at a lift station. These obstructions usually form at rough surfaces of sewers where the fluid flow becomes turbulent. All that FOG, along with human waste, settles into crevices in the sewer pipes. The fat can also interact with calcium that can either come from concrete pipes or water in the system that has flowed over concrete and undergoes the process of saponification, or turning into soap.

Recently the problem has increased due to the use of so called “flushable wipes”. Kimberly Worsham, founder of FLUSH (Facilitated Learning for Universal Sanitation and Hygiene) describes wet wipes as “absorbent cotton bastards” that, unlike toilet paper, don’t dissolve in water but instead are great at grabbing grease. “Imagine a bunch of fat-soaked wet wipes in a sewer about 2 feet wide—they’re going to get together and clump up.”

How big are they?

Fatbergs can be very large and can cause sewer backups. In 2017 a fatberg of congealed fat, wet wipes, and waste was discovered under the streets of Baltimore, Maryland that caused the spillage of 1.2 million gallons of sewage into Jones Falls.[1]. The largest fatberg in the UK was discovered in a sewer at Birchall Street in Liverpool. It weighed 440 tons and was 820 ft long. After 6 months is was still being removed from the sewer as it is proving to be difficult to break-down using conventional tools and equipment.[2] A fatberg the size of a gas tanker truck, found in Melbourne in April 2020, is thought to have grown so big due to a toilet paper shortage brought on by COVID-19, which spurred people to buy more wet wipes.[3, 4]

How can you prevent fatberg formation?

Fatberg formation can be minimized by simple actions including: 

  1. Installation of grease traps from commercial businesses. This is a common practice in the US and most cities have regulations relating to sizing and maintenance of the traps.
  2. Do not add coffee grounds, fat, oils or other food items to your drain. Even though you may have a garbage disposal, try to minimize the amount of material placed in them as it ultimately can add to the load on a wastewater treatment facility.
  3. Never flush wet wipes or anything other than toilet paper down the toilet. If you ever had a septic system, you know the problems and expense this will cause.

Fatberg in Macomb County, Michigan

While the super-sized fatbergs in major cities have gained significant media attention, this video from Detroit Public Television showcases a fatberg discovered in Macomb County, Michigan and features an interview with the public works commissioner.


  • https://en.wikipedia.org/wiki/Fatberg
  • https://www.mentalfloss.com/article/627079/fatberg-facts
  • 1Wells, Carrie. "'Fatberg' of congealed fat, wet wipes and waste discovered under Baltimore's streets, causing sewer overflows". The Baltimore Sun. Retrieved 26 September 2017
  • 2"Monster found in liverpool sewer". www.unitedutilities.com. Retrieved 22 July 2019.
  • 3"The flushed items that caused a 42-tonne 'fatberg' in Melbourne". 7NEWS.com.au. 14 April 2020. Retrieved 14 April 2020
  • 4"Giant fatberg heavier than petrol tanker discovered in Melbourne sewer". www.9news.com.au. Retrieved 14 April 2020
Image Credit: Macomb County Public Works


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