The facts about fatbergs
With the news that a 400 tonne 'fatberg' has been found in a sewer in Liverpool, we thought we'd give you a quick insight into what causes these sewer monsters and the steps we can take to try and stop them.
A solid mass found in sewers formed by the combination of non-biodegradable solid matter (e.g. wet wipes) and congealed grease or cooking fat. Fatbergs can come very dense as the material solidifies.
The congealed grease and oil trap debris and goes through a process called saponification which coverts fat into a soap like product.
A fatberg is formed from a build-up of debris (like wet wipes) and congealed grease and fat, which stick together and increase in size.
Congealed grease and cooking fat, other non-biodegradable solid matter such as wet wipes, cotton buds, sanitary products and other items.
We estimate around 250 metres long, but it could be even longer.
400 tonnes
This fatberg is being taken away by specialist contractors to process and produce biodiesel.
Rancid, there's no smell like it and is extremely difficult to break down and dispose of.
We have been trialling a number of non-hazardous chemicals that could break down the fatberg, however the time required to break this colossal fatberg down sufficiently for us to remove it through suction or washing it through the sewer system is too long. We are continuing to explore options to reduce the build-up of congealed grease and fat through our ongoing cleaning programmes.
We look after more than 40,000 km of sewers across the North West (that's enough to go around the circumference of the earth) so monitoring what goes into and builds up in the sewer network is a huge task.
We will have to repair parts of the sewer which may have been damaged when removing the fatberg.
By never pouring fats, oils and grease down the sink or flushing wet wipes down the loo.
The fatberg will take us around six weeks to clear from the sewer.
This sewer will be put onto a regular cleaning programme and closely monitored.
Yes, we have found smaller build ups of solidified fat and oil which we have been able to clean but blockages on this scale are rare. We'll continue with our monitoring and cleaning programme and ask our customers to not to pour fats, oil and grease down the sink or flush wet wipes down the loo.
No, it is very similar to the solidified oil and grease you have in your frying pan if you leave it too long after cooking. It does however contain lots of waste material such as wet wipes, sanitary products and cotton buds which are not nice to handle and can cause us problems at our treatment works.
The fatberg is safe to handle when wearing protective clothing. There is a potential for gas pockets to form within the fatberg so full breathing apparatus equipment, gas detector and health and safety approced electrical equipment must be used when removing the material within a confined space in the sewer.
The fatberg is 5 meters underground.
The blockage is preventing any flow of sewage to our wastewater treatment works, so it could start to flood out into the street or into homes and gardens. Until we unblock the sewer, we will remove the sewage in our tankers.
Blockages such as fatbergs cause sewage to backup which can result in flooding to streets, homes and gardens.
We have tried to clear the fatberg by jetting it with high pressure water but this has not worked because of the density of the blockage. We've had to dig a big hole to get to the sewer and manually dig out the blockage. This needs a lot of planning such as traffic lights, sludge tankers and a large team to clear the sewer safely.
The fat will be brought to our wastewater treatment works in Liverpool where it will be collected by a specialist recycling company who take the fat away to produce biodiesel.
Never pour it down the sink. Put the fat into a heat-proof bowl and when it's cool, put it in the bin, or simply wipe the pans clean with kitchen towel and bin it. If you have a lot of oil to dispose of contact your local council for advice on where to take it in your area.
We look after more than 77,000 km of sewers across the North West (that's enough to go around the circumference of the earth) so monitoring what goes into and builds up in the sewer network is a huge task. The primary reason is that the sewer serves a small catchment but is oversized (large diameter) as it is a brick egg sewer constructed by hand at the start of the 20th century. The sewers needed to be big enough to allow workers to get through them during construction hence being larger in size than we would design and build now.