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EN 1825 Overview
EN1825 is the British and European design standard for Grease Traps and Separators. BS EN 1825 also mandates the minimum size for a greasetrap.
Four main factors are considered. They are:
The EN1825 calculation is complicated. The good news is we can work it all out for you as part of our free survey.
We’ll work out all the variables from Maximum Flow Rate of Wastewater (Qs) – or how much waste water you produce; the Temperature Factor (ft) – hotter water reduces the efficiency of grease separators; the Density Factor (fd) of FOGs produced – this depends on what you’re cooking and how; and the Detergent and Rinsing Agent Factor (fr) – detergents, including dishwasher powders and rinsing aids will impair the separating effect – especially if plumbed in ‘upstream of’ a grease separator.
We’ll give you a full report and detailed EN1825 calculation completely free and without obligation. Chances are we can save you some money – but even if you don’t choose to act on the survey report you’ll know where you stand and you’ll know where we are if you need us.
1. Calculating Waste Water Volume per Day (V)
Qs is calculated according to the following formula: V = Vm x m where Vm is the volume of water used for food preparation – this is a coefficient determined by the EN 1825 Standard and m is the number of meals per day.
2. Calculating Waste Water Volume Qs
Qs is calculated according to the following formula: Qs = (V x F) / (3,600 x t) where Qs = maximum wastewater flow rate in litres per second, V = average volume of wastewater per day in litres, F = hourly inequality coefficient which depends on the type of establishment and t = average time of system operation per day in hours.
3. Other Factors
There are other constants and coefficients required by the Standard:
Putting It All Together…
Once all the above have been calculated we use the formula NS = Qs x Ft x Fd x Fr. This ‘nominal Size’ (NS) is then multiplied by 1,400 to give the minimum volume in litres. Or just contact us and we’ll do it all for free!
Read more about our Bio Drain Management – it makes undersized grease traps compliant plus reducing disposal and emptying costs and risk of blockage.
Grease Trap Physics
A greasetrap (or gravity grease interceptor) is quite simple in design. It is a metal or plastic box that is usually found under a sink in the kitchen, or underground either inside or outside the building.
Grease traps have a series of chambers to slow down waste water to allow fats, oils and greases to rise to the surface – because oil is lighter than water and so floats on it.
| Substance | Specific Gravity |
|---|---|
| Butter | 0.87 |
| Lard | 0.88 |
| Olive Oil | 0.91 |
| Water | 1.00 |
| Glycerine | 1.26 |
These captured FOGs need to be removed periodically (at least weekly as a rule) and taken away for disposal by a Licenced Waste Contractor. You can’t throw away FOGs in the general waste. It’s against the law.
The problem is greastraps need to be of sufficient size for the volume going through them – there is a European and British Standard to calculate this – or they get clogged with FOGs. If this happens they are rendered ineffective and the FOGs escape to the sewer – and you risk blockages and fines.
Grease poured into a still water will rise very quickly to the surface based on the size of the globules formed, their specific gravity, their viscosity and the temperature of the grease and water. The rise rates of the bubbles is predicted by Stokes Law. But the difference between a static body of water and a grease interceptor is that the water in the grease trap is not static. It flows. This is why the effectiveness of grease interception is affected by the amount of detergent, the flow rate and the temperature.
Questions? We can audit your FOG management with our free, no obligation survey and our Bio Drain Management system might help save you money and avoid blockages and fines.
They wake up when needed…
The active ingredient in our formulations are living bacteria.
They are in spore format. A spore is to a bacterium what a seed it to a plant; they are dormant until the conditions are correct for growth then they germinate.
These bacteria have been selected from nature for specific capabilities and then adapted to maximise those capabilities in drains, grease traps, urinals, washrooms – our technicians develop the correct mix of bacteria to digest specific types of soiling and these highly developed strains are blended in a synergistic combination, whereby different strains complement each other to maximise their effectiveness.
What’s In A Wee?
You might not think about urine too much. But we do. We’re geeky biologists and find such things fascinating. Urine is about 95% water. It’s the other 5% that’s fascinating…
The 5% of stuff that isn’t water is made up of waste matter cleaned from the bloodstream:
In humans (and most animals) day-to-day metabolism generates by-products rich in nitrogen that must be cleared from the bloodstream. Your kidneys take care of this and the result is urine – which flows from the kidneys through the ureters to the (urinary) bladder. Urine is the primary method for excreting water-soluble chemicals from the body. These include urea, uric acid, and creatinine.
But urine isn’t just waste – it has a role in the earth’s nitrogen cycle helping plants to grow. It’s also been used in gunpowder production, household cleaning, tanning of leather and dyeing of textiles.
What’s the Problem?
The organic wastes carried in urine are a nitrogen-rich food source for many organisms and the ultimate breakdown product of these compounds is ammonia (NH3) – which is the major contributor to malodours in urinals.
But that’s not all. Ammonia is highly alkaline when dissolved in water which leads to blockages – but not from uric acid ‘scale’ or crystals as many people claim. What’s actually happening is fascinating and problematic in equal measure. Let’s look at the chemistry that turns urea into ammonia:
Many sources attribute urinal pipe sludge and blockages to ‘uric acid salts’. This explanation is unlikely; uric acid and its salts are but minor constituents in urine (massively outweighed by urea) and while acidic conditions do promote uric acid scale buildup, the environmant in most urinal waste pipes is alkaline. Here’s why.
As we’ve already said even though urine is a waste product it still contains nutrients that all manner of biology can happily live on. Bacteria, algae, protozoa can use urine – and each other – as food sources. So, a urinal and its associated pipework supports a complex and diverse ecosystem – a ‘rainforest’ of microbial life.
Unfortunately, some of its residents can be rather antisocial. Many of the smells associated with urinals are caused by microbes breaking down urea into ammonia, particularly organisms such as Pseudomonas, Proteus, Klebsiella, staph and Mycoplasma. These all produce an enzyme called urease which speeds up the breakdown of urea into ammonia, which causes conditions to be alkaline.
Alkalinity is crucial. It triggers the crystallization of calcium and phosphate-containing stones such as struvite, hydroxyapatite, and calcite. This is also how kidney and bladder stones form, usually precipitated by a water infection with the above organisms. These are complex reactions and many factors are involved as well as pH – for example the type and amount of water hardness. As the pH rises calcium and magnesium compounds, previously in solution as bicarbonates, are deposited as insoluble carbonates. Dilution with tap water increases this fraction by providing the limiting calcium and magnesium ions. Copper ions from water pipes can also have an effect.
A biological waterless system can help. By seeding the system with the correct bacteria balance and a neutral pH can be restored. It’s important to remember bacteria are neither plumbers nor civil engineers and so can’t be expected to remove severe blockages, but many customers find blockages and slow running pipes improve.
In some cases drainage may initially slow down as scale and precipitation are broken down but this can usually be flushed away with a litre or two of warm water.
Not all bugs are bad…
Our products are very safe. The strains of bacteria we choose for our products are not hazardous to people or pets. Bacteria of the same species are sold as a dietary supplement in some countries!
Like many domestic detergents some formulations may be considered eye and skin irritants due to some of the components used. It is not recommended to expose skin to the product for excessive periods of time and hands should be washed after handling product and always read the Safety Data Sheet (SDS).
And not all bacteria are bad; far from it. Many are actually good for our health – they help us digest our food, produce vitamins and protect us against germs. And without microorganisms we would have no bread, beer or cheese not to mention they’ve been digesting our waste for millions of years – it’s microorganisms that do all the heavy lifting in sewage treatment plants.
There are some harmful ones – the ones that can make us sick – but the vast majority aren’t just harmless, they are positively beneficial.
Microbiology Basics
Bacteria
Bacteria are microscopic living organisms, usually one-celled, that can be found everywhere. A few types can be dangerous – such as when they cause infection – but most are completely harmless or beneficial. Examples are the production of yogurt, cheese or salami. Microbes also produce beer and wine but that’s yeast; it’s still a single-celled organism but from a different branch of the evolutionary tree.
Enzymes
Enzymes are biological catalysts – catalysts make chemical reactions happen faster but in the case of enzymes they’re far more complex than anything chemists use. Enzymes do all the heavy lifting in all biological processes. They are complex proteins and each one catalyses a very specific reaction – and does it extremely well. Which isn’t surprising: they’ve had 3.8 billion years of evolutionary refinement behind them.
In our products we put them to work by breaking apart large, complex compounds (substrates) into smaller, more readily absorbed nutrients that the bacteria can absorb. Each enzyme is designed to unlock and break down a specific food source.
The Link…
Bacteria produce enzymes to digest food around them. They don’t have a digestive tract like we do – they’re only a single cell, after all, so they need to digest their food externally into molecules small enough to pass across their cell membrane.
The clever bit is they will produce the correct suite of enzymes to digest whatever is around them. We just need to find the right bacteria that are best suited to a particular task. Think of them as minute factories producing the correct natural enzymes to digest whatever is around them, be it starch on a food factory floor or fats, oils and greases in a drain or sewer.
Enzymes produced by the friendly bacteria in our products include:
The ability of bacteria to produce the precise enzymes needed for degradation has been honed over billions of years of evolution so it’s hardly surprising they’re so much more effective than industrial chemicals at many tasks.
Try this…
You can try this test to see – well, taste – enzymes at work. Take a piece of cream cracker and start chewing. Don’t swallow. Cream crackers taste pretty bland because they’re mostly starch. Starch is a long molecule made up of lots of sugar molecules (maltose and glucose) joined end-to-end.
As you chew it will start to taste sweeter. And sweeter. This is because of an enzyme called ptyalin (or salivary amylase) in your saliva which is breaking down the starch into its constituent sugars, hence the increasing sweetness.
Requirement for Greasetraps
If you run a business producing food of any sort (whether you’re a factory, pub, restaurant, hotel or care home) the law says you need to have a ‘system‘ in place to deal with Fats, Oils and Greases (FOGs). If you discharge FOGs to the sewer you are breaking the law. The principal requirements can be found in the building regulations and the Water Industry Act 1991. There is a more comprehensive section on the law later but the Water Industry Act 1991 states:
No person shall throw, empty or turn, or suffer or permit to be thrown or emptied or to pass, into any public sewer, or into any drain or sewer communicating with a public sewer, any matter likely to injure the sewer or drain, to interfere with the free flow of its contents or to affect prejudicially the treatment and disposal of its contents.
This includes contamination by FOGs. Approved Document H to the Building Regulations 2000 (amended April 2002) says that the requirement for an adequate drainage system should minimise the risk of blockage or leakage. It goes on to state that one way of meeting this level of performance is for:
Drainage serving kitchens in commercial hot food premises should be fitted with a grease separator complying with BS EN1825-1 and designed in accordance with BS EN1825-2 or other effective means of grease removal.
This ‘system’ is often a grease trap but doesn’t need to be; you can also use a biological system either in place of a grease trap or to improve your existing grease trap’s performance. Click here for our guide to grease trap law.
There is a legal minimum size for a grease trap depending on the type of business you’re running. Calculating this is defined by BS EN1825 and it’s complicated – but we’ll happily do a survey and the calculation for free. Just get in touch and we’ll give you a free report with no obligation whatsoever. A coffee would be nice, though.
If you like how we work and we can help, great. If not, at least you’ll know where you stand and where we are when you need us.
Size Matters…
Because Fats, Oils and Greases (FOGs) are such an issue there are many laws preventing their release to sewers.
In terms of the requirement for grease interception, approved Document H to the Building Regulations 2000, as amended April 2002, says that the requirement for an adequate drainage system should minimize the risk of blockage or leakage of FOGs. It goes on to state that one way of meeting this level of performance is for:
“Drainage serving kitchens in commercial hot food premises should be fitted with a grease separator complying with BS EN1825-1 and designed in accordance with BS EN1825-2 or other effective means of grease removal.”
EN1825 is the European standard for commercial gravity grease separators. “Other effective means” include mechanical grease removal equipment and biological or bacterial dosing systems which break down grease.
So, if you have a grease trap EN 1825 stipulates its minimum size. If it’s less than that it’s advisable to augment it with a biological management system which will almost always be cheaper than installing a larger grease trap. It also reduces emptying cost and odours.
If you don’t have a greasetrap you need to fit a ‘system’ – either a grease trap or a biological system.
Saving Water Saves CO2 Too!
According to their trade association, Water UK, every day the UK’s 12 water companies supply us with about 20 billion litres of potable water. That’s about 7 cubic kilometres. We send about 60% of that back to them via the sewer network for processing. Unsurprisingly turning sewage back into potable water requires a fair amount of energy. And then they have to push it through over 400,000 km of pipes to send it back to us.
Don’t forget it’s not just about CO2 equivalents. It’s more about preventing the depletion of natural resources than simply reducing emissions. The ‘elephant in the room’ is the really wasteful part – the 30% of all UK mains water lost via network leaks…
Water UK estimates that the industry currently uses about 2-3% of all the electricity purchased in the UK and produces about 0.5% of the country’s greenhouse gas emissions. This amounts to about 4 million tonnes of ‘CO2 equivalents’ – a standardised measure of contribution to global warming.
To calculate the carbon cost of getting that water to you we use the official DEFRA / BEIS Greenhouse Gas Reporting conversion factors. The 2019 figures for embodied carbon in tap water are 0.344kg CO2e/m3 for water supply plus 0.708kg CO2e/m3 for water treatment.
These factors apply to UK-based organisations of all sizes, and for international organisations reporting on UK operations. The Streamlined Energy and Carbon Reporting (SECR) regulations now require many organisations to formally report their UK energy use and associated greenhouse gas emissions using these figures.
These are big numbers but when you divide it all up a litre of water has a footprint of just over a gram of CO2 equivalents. So, having a 150 litre bath every day for a year would generate about 60kg of greenhouse gas emissions. And a bath this size would cost you about 90p – 30p for the water, and 60p to heat it.
This can become a very big number quite quickly if you have a lot of urinals, hence the popularity of our eco-friendly waterless urinal system.
Discharges to drains and sewers are tightly controlled and enforced.
Summary: the law says you are responsible for the waste you produce and you can’t just chuck anything down the drain, and should they need to local authorities and utility providers can rely on a number of strategies to force businesses to process their wastes sensibly and responsibly. The ever-escalating stories about ‘fatbergs’ and the public’s increasing concern about environmental issues means this is not an issue that is going to go away.
Fortunately this is one of those rare case where the cost of non-compliance can be very high but the cost of compliance can be very low. Using a biological drain management system can often eliminate FOGs and odours, keep you on the right side of the law – and cut costs as well.
The principal pieces of legislation regarding your responsibilities for FOG management are listed in our article – including the new Environmental Permitting Regulations.
Calculating Water Use
Usually you’ll find a single cistern feeding 2-4 urinals. You can get a ‘back of the envelope’ figure for water use and potential savings quite simply.
1. Measure the Cistern
Measure the cistern in centimetres. Try to account for the thickness of the construction material and that the water won’t go all the way to the top – it’s the internal dimensions we need. then multiply H x W x D so a cistern that’s 30cm high x 4ocm across x 19cm deep = 22,800. Divide that by 1,000 to get the value in litres – 22.8 litres. Let’s round that up to 23.
2. How Often Does It Flush?
There’s no shortcut to this one. You need to time the interval between flushes. Let’s say it’s 18 minutes. One day is 24hrs x 60mins = 1,440 minutes per day. So, 1,440 divided by 18 = 80 flushes per day.
80 flushes per day x 23 litres = 1,840 litres. Per year that’s a staggering 671,600 litres. Which is 671.6 tons. Or 671.6m3.
Check the water / sewerage charges for your area. Each provider has a slightly different rate but it’s generally around the £2 / m3 mark. Multiply that out and that’s £1,343.20 per year. Four urinals: £335.80 each.
3. What Can I Save?
Obviously we’d need to do a proper survey but our waterless urinal system is about £1 per urinal per week. So that’s a cash saving of £1,135.20 plus nearly 700 tons of one of Nature’s most precious resources.
Where’s the Catch?
There isn’t one. No capital cost, no plumbing changes – just a simple urinal cake full of friendly bacteria that are slowly released into the urinal drain plus the biological cleaning fluid that goes with it – bacteria are alive and so bleach or harsh cleaning chemicals will kill them and you’ll need to start again. Just spray on and leave.
What Else Do I Need to Know?
Just that the friendly bacteria in the urinal cakes and spray are brilliant at removing the source of odours; use them for all toilet cleaning and you’ll get rid of all the whiffs without the need for expensive, ozone-depleting aerosols.
Our Bio Drain System Uses Green Biotechnology
Environmental biotechnology is the branch of biotechnology that addresses environmental problems such as the removal of pollution, renewable energy generation or biomass production by exploiting biological processes – in our case, microbiology.
We use living, ‘friendly’ bacteria for a number of tasks including saving water in waterless urinals and remediating waste but a mainstay of our business is digesting FOGs discharged by food businesses. To put it simply, hungry (but harmeless) bacteria are automatically dosed into the kitchen greasetrap / drain system each night to digest FOGs.
They digest FOGs by releasing natural catalysts called enzymes. Because bacteria are simple, single-celled organisms they don’t have a digestive tract like we do. They need to break down any potential food source around them until it’s small enough to absorb through their cell walls.
Pretty much all animal and vegetable fats are triglycerides – three fatty acids (of varying length) attached to a glycerol ‘backbone’. The microbes in biological products produce enzymes to cleave the fatty acids from the glycerol backbone – so they can use them as food. Here’s how it works:
Most animal and vegetable fats are triglycerides – three fatty acids (of varying length) attached to a glycerol ‘backbone’. The microbes in biological products produce enzymes to cleave the fatty acids from the glycerol backbone – so they can use them as food.
The glycerol and fatty acids are water-soluble and small enough to pass through the bacterial cell wall.
But an important point is that they cannot recombine and turn back into fat – that breaks the laws of chemistry – so a biological system actually digests fats rather than just emulsifying them (as a detergent would) so they can cause trouble further down the line.
Over time the grease-digesting bacteria will work their way up and around the inside of the pipe forming a ‘biofilm’ – a microbial city – preventing FOGs causing blockages.
A properly set-up biological system is incredibly effective at its job; far more so than anything that can be accomplished with toxic chemicals. This is because the bacteria we choose have evolved over billions of years (about 3.8 billion according to evolutionary biologists) so they’ve had plenty of time to become very efficient.
The Undersizing Epidemic
If your greasetrap is too small to comply with the legal requirements of EN1825 you can be prosecuted under Section 85 of the Water Resources Act 1991 or Section 59 of the Building Act 1984.
If you have a blockage you will be subject to sanction under Section 35 of the Local Government (Misc Provisions) Act 1982 or Section 343 of the Public Health Act 1936. If it’s a new build or extension Part H Section 2.21 of the Building Regulations 2000 also applies.
If your grease trap is undersized you need improve your system for dealing with FOGs. You can fit a larger grease interceptor or add a biological system. Fitting a biological system can eliminate FOGs and odours as well as significantly decreasing the requirement for sludging. It’s also cheaper and less disruptive to install and run than a new, larger grease interceptor.
Contact us for a free survey so you know where you stand. We can probably save you money with a biological system even if your grease trap is of the correct size. (But most aren’t…)
Automatic Dosing. Fully Managed.
There are many ways to dose the bacteria. We can suspend a Wet Well Block that gradually dissolves and releases bacteria, our Waterless Urinal system uses the same principle in microcosm, but our Drain Management System automatically doses the friendly bacteria in a liquid format every night via a battery-operated automatic pump.
Don’t the bacteria get washed away?
Not once they get established. We dose them late at night to give them the maximum time to get to work. Bacteria tend not to be ‘planktonic’ swimming about at random. What they prefer is stick to surfaces. Like the inner walls of pipes and grease traps. The do this in the body too on the walls of our gut or – if they get into the wrong place – causing cystitis.
In drains and grease traps they form a ‘biofilm’ – it looks like slime but it’s a microbial city, teeming with life. The resident bacteria are protected by the biofilm and produce the FOG-digesting enzymes so they can feed.
The biofilm will keep growing along the waste pipes as time progresses. Biofilms are impossibly thin but tougher than Teflon. So, over time it’s not just the grease trap that benefits from billions of hungry bacteria, the whole drain system will.
Quantifying the waste in waste water
When effluent is treated at a water treatment plant it goes though a number of stages. One of these stages – ‘secondary treatment’ – is where the effluent is placed in to large tanks and air is pumped through. This allows aerobic bacteria and protozoa to digest much of the organic material in the effluent. ‘Aerobic’ describes microorganisms that require oxygen, so an indirect measure of how much organic matter is in effluent is the amount of oxygen required to remediate it. Extra processing costs time and money so if you’re producing effluent with high BOD and COD you are likely to have to pay a surcharge.
Biological Oxygen Demand (BOD)
BOD is a measure of the biodegradability of the effluent. The higher the value, the more oxygen needed to break this down.
Chemical Oxygen Demand (COD)
COD is a measure of total strength of the effluent. This includes chemicals, biological compounds, organics and inorganic chemicals and suspended solids. COD is less specific than BOD since it measures everything that can be chemically oxidized, rather than just levels of biodegradable organic matter.
Link Between BOD and COD
This depends on the industry but as a rule COD is 3 – 4x BOD. The introduction of a biological system will initially increase BOD but that will then decrease, bringing the COD down with it. A biological dosing system can reduce the COD by up to 60 %.
BOD and COD values are most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C. The higher the value the more waste treatment costs.
Total Suspended Solids (TSS)
TSS is the dry weight of suspended particles remaining undissolved in a sample of water that can be trapped by a filter that is subsequently analysed. It is another water quality parameter used to assess the quality of a specimen of water. It lacks the specificity of BOD and COD because will always be variables such as type of filter paper used but it is still a useful measure when properly controlled.
First, let’s define GMO…
The short answer is ‘no’ but there’s a bigger and more nuanced answer – and it’s important.
What Are GMOs?
In its broadest sense, humans genetically modifying organisms is nothing new.
We’ve been doing it to plants and animals for thousands of years. Whether it’s domesticating the wolf into dogs of all shapes and sizes to cross-breeding different types of corn, we’ve been creating new varieties of organism for ages. this can involve cross-pollination to create a hybrid species trying to get the best traits from closely related species.
Countless varieties of common plants have been genetically engineered in this way: orange carrots were developed by a lucky mutation resulting in high levels of beta-carotine and carrots became an important staple crop and source of vitamin A.
Then about a century ago we came up with ‘mutation breeding’ – exposing plants to chemicals or to radiation that increases their genetic mutation rate. This led to 2,540 mutagenic plant varietals being released between 1930 and 2007. It’s not just the carrot, there is not a single thing we eat today that is ‘natural’ in that we’ve been cross-breeding, forcing mutations and all sorts of other techniques to increase yield, flavour or whatever else we wanted for a very long time.
But all this changed in 1969 when Herb Boyer, Stanley Cohen and Paul Berg discovered a means to splice a gene from one organism and insert it into another, and have its new host express the gene as its own. Herb Boyer continued with the research and he and in August 1978 he produced synthetic insulin using his new ‘transgenic’ genetically modified bacteria, followed in 1979 by growth hormone.
Just let that sink in. Until that point Type 1 diabetics only had access to bovine or porcine insulin. Suddenly it was possible to brew pure human insulin in exactly the same way you would wine or beer. Since then there have been many advances in the field. For the genetic pedants out there (they exist, we have one safely locked away in the lab here) the ability to swap genetic material between different species does occur in nature too.
So, for the purposes of this answer we will define GMOs as:
Organisms where one or more specific genes from a distant species – even from different kingdoms of life – has been artificially inserted; for example putting a gene from a bacterium into a plant or vice versa.
Glad we’ve cleared that up.
So what’s the answer?
We do not use any GMO / transgenic organisms in our products.
Why not?
Quite simply because we don’t need to. There are plenty of naturally-occurring strains out there that do the sort of green biotech tasks we need them to, and they do it rather well.
But we aren’t fence-sitters on GMOs: yes, it’s a powerful technique and needs to be used responsibly but if we’re going to feed the planet’s ever-increasing population it’s difficult to see how we can do it without using these technologies. Better yields, less pesticide use, the list goes on.
If you’re curious about GMOs and what the fuss is about there is an excellent book by Mark Lynas called Seeds of Science. He was a very active anti-GMO campaigner and activist in the 1980s. He then studied the subject in great depth and was brave enough to change his views when – after much research – he couldn’t find any evidence to show harm – quite the opposite.