Undrestanding Kitchen Drainage

Blocked drains can be caused by wastewater full of fats, oils, grease (FOGS) and/or starches, and possibly the build up of food waste that washes off dirty plates, as well as fat spilled on the floor or by bad kitchen practice. It is unlikely to be the result of the new dishwash machine, although build up of other waste product down the drain could also be a cause.

A key kitchen discipline is a good 'waste' management policy. Food waste should be disposed of properly into containers for collection and not pushed through drains. If using a Food Waste Disposer, ensure that a good run on time is allowed to ensure that macerated food waste is flushed through the drains with cold water only to avoid settlement in local waste pipelines. Excess grease and any excess fats, oils or grease (FOGs) should be deposited into a sealable container for collection. But no matter how well the plates are scraped, some FOGs will inevitably escape down the drains during pre-rinsing or washing. The potential for blockages can be avoided by :

Fitting a suitably sized grease trap or fat separation unit to the water outflow system, preferably outside the Kitchen.

Installing a biological method of treating and permanently breaking down fats, oils and grease called bioremediation .
Flushing using cold water only – hot water will separate the fat from food particles, allowing it to congregate and cause congestion.

NOTE on building regulations. Both mechanical grease traps and bioremediation systems comply with H-regs, according to the body which publishes building regulations: “Drainage serving (commercial) kitchens should be fitted with a grease separator complying with prEN 1825-1 and designed in accordance with prEN 1825-2 or other effective means of grease removal.”

A grease trap works by slowing down the flow of warm or hot greasy water coming out of a dishwasher and allowing it to cool. As the water cools, the grease and oil should separate and float to the top of the grease trap. The cooler water, containing less grease, continues to flow down the pipe to the sewer. The grease is trapped by baffles which cover the inlet and outlet of the tank, preventing grease from flowing out of the trap. The baffles and strainer baskets need to be regularly removed for cleaning, at which point any collected grease should be disposed of properly.

Most importantly, a grease trap has to be sited sufficiently far away from the dishwasher to allow the emulsified fat to cool and separate out from the water. Wastewater from dishwashers, combi ovens and pot wash areas can range from 40ºC to 95ºC. If the temperature is too high and the grease trap too close, FOGs remain in solution and can be flushed through traps, causing problems in the drainage system when the effluent has cooled and the FOGs start to coagulate. Because of the nature of the Grease Trap contents, and to encourage better working, it is preferable that the trap is sited outside of the Kitchen environment.

An alternative to grease traps is bioremediation. Bioremediation is a Biological drain maintenance system whereby the drains are regularly dosed (usually overnight) with a multi-strain grease degrading bacterial solution that breaks down the FOGs and other food waste matter and keeps the drains free running. Such systems work very well alone or can be used along with grease traps - it's up to the operator.

There are many different commercial bioremediation fluid products on the market with different properties and strengths. Multi-strain grease degrading formulations seem to be the most effective as the multi-strain formulation will work on complex multiple strains of fatty acids and food material in the wastewater from different kinds of foods. Some fatty acids are complex and can be very difficult to break down, so Multi-Strain varieties can provide a far more effective solution. As with most things in life, you may pay a little more for something that in the long run is far more effective. When working along with grease traps, Bioremediation treatment of the grease trap should mean that the trap should not have to be serviced as often with costly interruptions to operations - Engineer visits should be reduced, cleaning time reduced and the the trap's efficiency improved.

Talk to your dishwasher supplier / equipment distributor or the manufacturer to find out the best way to fit a grease trap and/or include a bioremediation system at your site. The good news is that it's a relatively simple procedure and shouldn't be too expensive.

14/08/2008 13:35:34