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Seeing Through the FOG

15 January 2009

Fats, Oils and Grease (FOG) is a solid problem for the foodservice and catering industry. According to Geoff Ward, fat traps are a potential health hazard if not located and maintained properly. Caterers need to examine their equipment, processes and training

OUR DRAINAGE SYSTEM AND PUBLIC WATER SUPPLIES network are the single most important factors revolutionising our public health historically. While this public health gain was hard won, it is today becoming rapidly eroded by the conflicting and competing requirements of today’s society. We are eating too much fat with adverse consequences for our life expectancy. We are also obsessive about hygiene and use too many chemicals, often without regard to long-term effects. The increasing trend towards fast food and eating out is leading to more drainage problems. Every year there are around 200,000 sewer blockages in the UK, of which up to 75 per cent are caused by fats, oils and greases (FOG). Thames Water Company alone experiencing around 65,000 stoppages each year.

The catering industry is being pressured to become more environmentally friendly and sustainable while keeping up with the pace of change in legislation – food safety, health and safety, fire safety, planning and employment law, and now environmental and climate change law.

The current technology for dealing with FOG in catering premises is hardly rocket science. It includes solutions such as installing grease traps, treatment of effluent with microbes that digest grease and the age-old measure of not letting FOG go down the drains in the first place. Experience shows that grease traps offer a false sense of security to the caterer that the problem has been effectively dealt with. It is effectively an internal septic tank and the last place a kitchen porter would want to clean on a regular basis. It does not take long before the trap is a living hell of rancid foul smelling gunk which overpowers the senses, penetrating every corner of the catering environment once the cover is removed.

Fat traps probably give a false sense of security and more FOG enters the system in the belief that the trap will deal with it. What is often overlooked is the fact that grease traps should only be emptied and cleaned out by licensed waste contractors, who have the correct equipment. The content of traps is hazardous waste under the Hazardous Waste Regulation 2005.

Grease traps are also often undersized, badly located and rarely installed to intercept all the waste from grease-producing equipment. DIN EN 1825-1 & 2 is the relevant standard if a grease trap is going to be used, but this specifies extremely large grease separators and often there simply is not sufficient space in the kitchen, and nowhere suitable outside of the kitchen to site an appropriately sized grease trap.

Under-sizing can also be caused by cost considerations as well as space constraints through modern kitchen design. There is rarely cold water in the trap to cause the FOG to solidify and rise to the surface. Much of the FOG remains in solution, passing straight through the inefficient trap to solidify in the cold sewer.

Replacement traps
Often grease traps are installed in the kitchen under the sink because there is no suitable outside area. Under these circumstances the real nightmare for hygiene begins. The problem is that part H of The Building Regulations 2000 requires that any ‘hot food operation should fit a grease separator, or other means of grease removal’. Grease traps are then regularly installed inside the catering premises. How can the necessary cleaning and maintenance of these septic tanks be safely and regularly carried out without effectively closing the kitchen – something the proprietor is unwilling to do? As a result, the task is often not done, rendering the trap useless within a few weeks of its installation. Some companies to their credit offer a service involving the removal and replacement of the trap with cleaning undertaken off-site. This seems to provide a very realistic alternative to fixed traps.

There is also the possibility of FOG recovery and bio-fuel production that could help businesses with their future sustainability plans. In a modest-sized high street catering business, such as a Chinese takeaway, the annual cost of recovery is around £700-800 per year, reasonable compared to what a properly sized trap plus a maintenance contract would cost. The replaceable traps also have the advantage that they will normally remain sealed until they have left the premises, making under-sink traps an acceptable option.

Fixed traps, however, tend to act as a ‘sump’ for all kitchen waste and effluent discharge to collect and putrefy. The trap is likely to become the focus of infestation and environmental contamination particularly cockroaches, flies and maggots. If the lid is regularly removed for cleaning and maintenance, it invariably never quite go back the same, such that the seal is never truly gas and water-tight. This has the potential for ongoing adverse odours and allows for ready access and egress of pests. Grease traps are a serious source of potential contamination and pest breeding – in the very heart of the kitchen.

It could even be that many grease traps in kitchens are in fact illegal. The British Standard on drainage systems BS EN 12056-1:2000 - Drainage Systems Inside Buildings includes a number of requirements that raises compliance issues with regards to grease traps inside kitchens. For example, any drainage system must not allow odours or fetid air to be released inside buildings. How can a grease trap fitted inside a kitchen, or inside any part of a building with its foul waste content possibly comply with this? Secondly, and most appropriately from a food hygiene perspective, European regulation EC 852 has many references that would make grease traps an unsatisfactory design feature in any foodservice operation.

EC 852 requires that “All waste is to be eliminated in a hygienic and environmentally friendly way in accordance with Community legislation applicable to that effect, and is not to constitute a direct or indirect source of contamination.” The installation of grease traps in kitchens has the potential for a legacy of issues and potential legislative non-compliance.

So is it back to the drawing board? Possibly not. Traps do work if they are correctly sized, and correctly located. This would point to having traps that are fitted externally and underground, to provide the necessary volume and operating temperature to allow the system to work properly. But to start digging up high streets up and down the country to install such devices is going to take some considerable encouragement and funding and is probably a non-starter.

Alternatively, the use of bacteria or enzymes to break down FOGs permanently is a practical solution. Sewage treatment plants rely on bacteria to digest sewage, breaking down the long molecular chains of fats, oils and greases and producing sludge. The sewage sludge cake is said to be almost innocuous and odourless. These treatment systems are becoming more readily available, are clearly easy to use and clean, and should take up no floor space. However, the effectiveness of the bioremediation process is dependent on a number of factors including the dwell time in drainage, the make up and quality of the fluid that is being introduced to the drainage system and the volume and types of bacteria/enzymes.

The real answer to catering FOG is not to let it into the drains in the first place. It is yet another management system to live with in the kitchen but it is achievable with common sense and training. It is illegal under the Water Industry Act “…. to put anything down into the sewer which might impede its flow.” Therefore all FOG should be collected and regularly taken away by a licensed contractor. All plates, utensils and equipment should be scraped prior to washing and any fat residues also collected from roasting trays and grill pans. It is a matter of staff awareness. Certainly this is an issue that’s not going to go away and if the industry does not get its act together, it is an area the legislators could really get their teeth into, increasing the regulatory burden further.

We cannot allow the public health infrastructure to be damaged such that there is increased risk of flooding and risk to health. We cannot cause food risks through bad design and installation of equipment that contributes to food safety risks.


BS EN 12056-1:2000 - Drainage Systems Inside Buildings

(EC) 852/2004 Hygiene of Foodstuffs

The Building Regulations 2000 part H: Drainage and waste disposal

DIN EN 1825-1&2:2004 Grease Separators

The Hazardous Waste (England & Wales) Regulations 2005

● Geoff Ward, TD, FCIEH, CMIOSH, FCSI, is a consultant with Connaught Compliance Services.

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