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  • Graeme Warnell

How Can We Prevent Fatbergs ?

A "fatberg" is a congealed lump of fat, sanitary items, wet wipes, and similar items found in the sewer systems, which do not breakdown. Fat, oil and grease are the primary binding agents for all the debris disposed into the public sewer systems of the world.

Fat mainly enters the sewer systems via private homes and food retailing outlets.

At home, we all know not to empty the chip pan down the sink but just through normal cooking, cleaning and the use of dishwashers we still put fat, oil and grease into the sewers.

Food outlets should all have either grease traps installed or be signed up to a waste oil collection service, but even then, the daily washing of pots, pans, plates and kitchen floors still disposes a lot of fat into the sewers. Oil and grease are then emulsified by detergents and form a solid mass blocking the pipes.

Even small amounts of fat, oil and grease per household or food outlet entering the sewers have a massive accumulative effect. London, for example, has the highest concentration of food businesses in the country, and it produces an estimated 32m–44 million litres of used cooking oil every year.

Domestically UK households use over 100 million litres of cooking oil per annum.

To understand the financial impact of these fatbergs we need to understand the cost of not only removing them but also in business and domestic disruption when drains are blocked.

There are approximately 366,000 sewer blockages per year in the UK.

70% are due to fats, oil and grease

The annual cost to combined UK water authorities to deal with these blockages running at an estimated £80 million per annum

Thames Water Company dealt with over 200,000 blockages in the last five years, with 18,000 homes flooded with sewage. It spends approximately £1 million a month clearing fatbergs across its region. Ealing, Hounslow, Harrow, and Windsor & Maidenhead are blockage hotspots.

All this disruption and cost even though the law is very clear:

However, Section 111 of the Water Industry Act 1991 says that - “it is a criminal offence to discharge into the public sewers any matter which may interfere with the free flow of the sewerage system”

It is important to recognise that having a law with no real manpower or effective process to enforce it is a little toothless.

We only need to look at some of the recent fatbergs that have made news headlines to understand the scale of the problem

Shepherd's Bush in West London – a collection of waste, fat, wet wipes, food, tennis balls and wood planks the size of a Boeing 747 aeroplane was discovered and cleared by sanitation workers within a drain beneath a 260-foot section of road

Durham - a 30m long fatberg river has been found congealed in a sewage pipe under a road. The pipe collapsed due to fat being poured down residents' drains for several years.

Bedfordshire - a line of fatbergs clogged a 100m section of the sewer. Anglia Water has to ship in specialist remote control robotic equipment from the Netherlands to view and high pressure jet the blockage to help it disperse

Sidmouth in Devon - South West Water discovered a 64-metre fatberg in a sewer under the seaside resort. That’s longer than six double decker buses

Cardiff - Welsh Water said it had discovered and removed 800 tons of fat from sewers beneath its capital city.

Nearly all the UK water authorities ask food outlets not to pour fat, oil and grease down their sinks and drains. However, many feel that if their sink is not blocked, it cannot be their problem. So why do these fatbergs block the sewers?

The two main routes of fat, oil and grease getting into the sewers fall into two broad areas.

Malicious dumping of large volumes of cooking oil directly into drains by food outlets. Do not be fooled into thinking that this is just the small takeaway operators! Some of the worst fat, oil and grease blockages I have ever seen were caused by the biggest fast-food operator in the UK.

The disposal of fat, oil and grease from licenced food outlets has to be monitored by local authorities. Every food outlet should have a certificate confirming they either have an adequate grease trap installed and evidence that it is routinely maintained or should be able to prove it has its waste oil collected regularly by an authorised service provider.

Incidental Release of fats, oil and grease as part of daily cleaning regimes.

This is probably one of the most underestimated sources of fat, oil and grease release into the sewer network. The impact of routine floor cleaning creates two major issues. It is not just the fat, oil and grease that is a problem but also the toxic mix of cleaning chemicals that accompany it.

Traditional cleaning using chemical products simply moves dirt, fat, oil and grease from the floor to the drains. The harsh caustic floor cleaning products keep the fat emulsified, so it does not solidify until it accumulates in the sewers. In a typical sewer environment billions of harmless bacteria would start to ingest and break down some of the fat, oil and grease.

However, the pandemic witnessed a huge increase in the use of broad spectrum disinfectants and anti-bacterial products. These have flowed into the sewer network with a devastating effect on the colonies of harmless, yet essential bacteria responsible for breaking down our waste.

Is there anything we can do that is proactive to ensure floors are effectively cleaned that does not add to the fatberg problem or add to the amount of toxic chemical waste we pour into our drains and sewers?

The answer is YES. We need to break the cycle of this dependence on chemical cleaning products. There is a wide range of nature-based products that clean even more effectively than chemical products but do not add toxins to the drains or sewers. Even better still, there are nature-based cleaning products that put the essential, harmless bacteria back into our drains and sewers. These bacteria will help ingest the fats, oil and grease that get poured away with the wastewater after your cleaning process has finished.

Furthermore, these nature-based solutions can be used for dosing grease traps where they “eat” the fats, oil and grease.

To prove the effectiveness of nature-based products GW Environmental went to visit a busy Thai restaurant equipped with a grease trap.

Every 30 days the thickness of fat in the grease trap grew by 8 cm which meant it had to be emptied every 90 days or the drains would block.

The emptying process involved a tanker attending to remove the fat at a cost of over 300 euros each visit. The kitchen had to be closed during the process and a foul smell lingered in the premises for 2-3 days afterwards. It is also important to remember that the road tanker generates a significant carbon footprint with every visit.

We dosed the grease trap with a nature-based product and asked the restaurant to swap their chemical floor cleaner with a nature-based product. Every 3 months the grease trap received an additional booster dose administered by pouring it down the sink.

At the beginning of the trial the grease trap contained an 18 cm-thick layer of fat. By day 120 of the trial the fat level reduced and then stabilised at 8 cm. The grease trap never had to be emptied again.

The nature-based products, we recommended, were cheaper than the chemical floor cleaner that had been previously used at the restaurant. Thus the restaurant saved money both on cleaning products and not having to empty the grease trap anymore.

The staff were exceptionally pleased with the cleaning results of the nature-based product and the fact that it was much safer to handle.

Nothing toxic entered the sewer system or the environment.

If you found this article interesting and would like more information on using nature-based products for cleaning instead of toxic chemicals, please email the author Graeme Warnell at

By implementing environmentally responsible cleaning practises, you could help reduce the pollution of our rivers and oceans, create a safer workplace for your employees, reduce your carbon footprint and put something good back into the environment so why wouldn’t you?

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