A large amount of fat, oil and grease (FOG) is produced by commercial kitchens and food establishments every day. If left untreated or not removed before joining the main sewage system, it can cause major issues with main sewers and a huge amount of disruption to businesses as it is cleared. In many countries, it is a legal requirement to install a suitable grease treatment system for effective removal of this material from wastewater from commercial hot food premises.

Grease Traps separate out solid material and fats from the water draining from dishwashers and sinks. They are installed between the sink or dishwasher and the drains, so that the wastewater flows through them and any solids and fats are stopped from entering the drainage or sewer system. Pre-Treatment Technologies diagram

How Does A Grease Trap Work?

When the waste water from your kitchen enters the trap, it flows first through a sediment basket which removes larger solid particles. The grease in the water is less dense (“lighter”) than water and doesn’t mix with it, so it floats to the top. This allows the FOG to be separated from the water and the grease trap then lets the “cleaned” waste water flow to the drains.
Walmart collects and recycles yellow grease for use as bio fuel

Grease traps have to be cleaned regularly to remove these FOGS, otherwise, they build-up, and can eventually overflow through the outlet and even back-up through the inlet. This is why it is best NOT to use a waste disposal machine on the dish washing sinks, as this sends ground up food, including FOGs into the waste water system, which then has to be cleared using a grease trap. It is more effective to scrape any waste food into a bin before washing the dishes or adding them to the dishwasher. The FOG material can be disposed of or recycled. Walmart recycles the yellow grease from chicken rotisseries and this is converted to bio fuel. Alternatively, special cleaning materials can be used to reduce or prevent FOG build-up in internal piping. You should check whether these are allowed in your area, before using them. Not all water authorities allow their use.

Stainless Steel Grease Traps

Grease can eventually be corrosive to metals used in grease traps, this is why it is best to use stainless steel grease traps as these do not corrode and will last many years provided they are cleaned regularly.