Dealing With Fats, Oils and Greases (FOGs)

Food businesses produce FOGs and are responsible for dealing with them before they get to the sewer.

The problem is most people don’t understand how grease traps work, how to maintain them or what size they legally need to be.

What this means is most greasetraps are undersized, aren’t maintained properly and can’t cope with the effluent going through them.

The result?

Build up of FOGs in drainage systems causing blockages and foul odours, and further down the line fatbergs in sewers. First, let’s understand the types of system out there.

FOGs blocking pipe

There are two basic types of drainage systems: those with a grease trap (interceptor) and those without a greasetrap; either can also include a wet well prior to pumping to the main sewer.

greasetrap fogsMany establishments use grease traps. These are can be anything from a plastic or metal box under the sink to prefabricated pits of varying size and construction. All depend on the basic principle of oil floating on water.  Effluent enters the trap where a dip pipe or baffle plates slow the flow so the FOGs rise allowing relatively clean water to be discharged. Find out more here.

Problems begin to occur if they are not regularly cleaned. FOG build-up can result in backing up of pipes, restricting flow and causing blockages.  Other common problems are:

  • Undersizing: the grease trap was too small when fitted or has not kept pace with increased volume. This results in overloading and necessitates more frequent emptying / unblocking.

  • Food Debris: many interceptors are fitted with baskets to catch food scraps and other debris. The food particles cause blockages if not emptied regularly. This can be fixed with more regular emptying but staff training is vital: preventing food getting in there by proper pre-scrapping is key.

  • Poor Layout / Design: if the interceptor is in the wrong place, there are issues with groundworks / drains or large amounts of surfactant (e.g. from a dishwasher) are being discharged this can also have a huge impact on performance.

It’s not just that grease collects around corners, low gradient pipes, manholes etc leading to – at best – the emission of unpleasant odours from rancid fats and – worse – blockages and foul water flood, it is a legal requirement to have a system to deal with FOGs. This can be a grease trap, a biological system or a combination.

Wet wells are holding sumps for gravity-flow sewer systems. These are generally used in larger premises where access to mains drainage is challenging. Most often wet wells are employed either when the main sewer is distant and effluent needs the help of a pump, or if – for example – the kitchen or lavatories are in the basement and below the level of the main sewer. In this case thee wet well pumps the effluent up to the sewer.

The principle is quite simple: all the effluent goes to the lowest point in the establishment where it drains to the wet well and is periodically pumped away / up to the main sewer. As sewage enters the wet well and the water level rises, pumps are engaged to pump out the sewage to the main sewer.

Wet wells are essentially very large grease traps. If not maintained properly FOGs can jam the trip switches. This has two possible outcomes: the pump doesn’t switch off and burns out (expensive) or doesn’t actuate at all. In both these cases you end up with a foul water flood which is as unpleasant as it is costly.

So, dealing with effluent is replete with issues both operational and legal. Even with a well-managed system there is still the issue of malodours and the potential for blockage as well as the day-to-day expense of emptying and licenced waste costs.

Help is at hand…

A Bio Drain Management System automatically doses a naturally occurring microbe blend that releases enzymes to break down the FOGs that cause multiple issues in drainage systems. The microbes form a biofilm on the walls of the drainage system which continuously releases enzymes, forming an effective barrier to solid grease deposits.

  • With grease traps: odour elimination, FOG reduction, no more emptying, legal compliance if undersized;

  • No grease trap: immediate legal compliance, no more odours, eliminate any existing build-ups and help prevent future problems.

  • Wet Wells: regular dosing will reduce the build up of fats, extending pump life and preventing trip switch fouling. This can be via liquid dosing or a wet well block.

What’s the Cost?

A Bio Drain Management System can cost as little as 2p per meal. But you need to consider your current cost base too. Consider the following:

A single greasetrap takes an hour to clean and a whole system can take a day. Whether it’s a third-party provider or your own staff this is a significant cost. Also FOGs are licenced waste and need to be disposed of by a specialist contractor. Again, a material expense.

Is the kitchen out of service while this occurs? Even if it isn’t there’s still the opportunity cost of staff performing the task.

If you have kitchen staff emptying and/or cleaning the grease trap this is a significant control point under HACCP. Drains and grease traps are replete with Gram-negatives and other organisms involved in foodborne intoxication and infection.

Are the Environment Agency enforcing discharge consents and charging a levy based on the nature of the effluent. This is normally based on BOD and COD – which can be  reduced by up to 75% with a biological system.

How long are drain runs? How old are they? The older they are the more likely they are to deteriorate when rodded or jetted. Also long drain runs are more likely to block – and more expensive to fix.

If you have your own treatment plant problem effluents can have a dramatic effect on efficiency. A biological system will ‘fine tune’ the biomass and make the system work much more efficiently leading to reduced sludge build up, fewer desilts and lower costs.

Where’s the Catch?

A Bio Drain Management System can’t solve everything. If you’ve got collapsed drains or other problems that need a civil engineering fix the friendly bugs can’t solve that. They’re brilliant at dealing with FOGs, odours and keeping the drains running free – but they’re not brickies or plumbers and they can’t deal with toothpicks, cocktail sticks, wet wipes, sanitary towels, your ex’s favourite jumper or your broken dreams. Sorry.

But they will keep waste pipes, drains and grease traps as slick as a buttered dolphin. Contact us for a free, no obligation survey.

Are you compliant? If you’re discharging FOGs to the sewer you are liable to fines and prosecution. Contact us for a free, no obligation survey to see where you stand. You can read more about FOG management here or search our FAQs.

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