Food businesses and trade waste
Food businesses including but not limited to restaurants, cafes, and takeaway shops produce wastewater containing fats, oils, and grease (FOG) which can solidify and block sewer pipes.
The Combined Local Waters Bylaw requires all food businesses to pretreat their wastewater discharge before it enters the wastewater network.
Pre-treatment technology includes grease traps, mechanical grease separators, and grease converters.
Types of Grease Traps
Passive Grease Traps
Passive Grease Traps are the most common and preferred type of pre-treatment devices. They are often found in the ground outside a kitchen’s back door. These devices are typically made up of two or three chambers separated by baffles and filled with cold water. The cold water within the trap cools down any hot wastewater entering it, solidifying the grease which then floats to the top. Any solid materials that are washed into the trap will settle to the bottom, forming sediment.
Maintenance requirements for Passive Grease Traps
Maintenance involves removing both the layer of fat from the top and the sediment from the bottom of the grease trap. This requires the entire contents of the trap to be sucked out along with scraping down the walls and baffles. All cleaning water must be sucked out. The final important step involves re-filling the trap with cold water to allow the trap to get back to work separating the grease from the wastewater.
Mechanical Grease Separators
A mechanical grease separator works by first passing the wastewater through a strainer basket to remove any solids. The grease is then separated by a paddlewheel which has been coated to allow the grease to stick as it spins through the wastewater. As the wheel leaves the water, a wiper blade scrapes the fat and oil from the surface of the wheel. The grease is channelled into a container on the side of the device to be emptied. A heater makes sure the grease remains liquid during the process to aid separation and transfer.
Maintenance Requirements for Mechanical Grease Separators
Every day:
Once a week:
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Clean the wiper blades and grease outlet through
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Check the timer is set properly – 15 minutes minimum, 1 hour maximum
Once a month:
Grease Converters
No new or replacement Grease Trap Converters can be connected to the Council Wastewater Network.
If your business currently has a Grease Converter installed you can continue to use it, but when you replace it you will need to install a passive grease trap.
Maintenance requirements for Grease Converters
A certified and registered installer must carry out the servicing. Grease converters should NOT be cleaned out like passive traps as this disrupts the bacteria which break down the oil and grease.
Inspections
The Trade Waste officer will check all types of grease trap at least once a year.
If we find the grease trap isn’t doing its job, or cleaning records aren’t complete, we will ask you to remedy the situation and will carry out another inspection a short time later.
If we still find problems on the second inspection:
Recycling cooking oil
You might be able to recycle your cooking oil. The recycling company will give you containers for the used oil and will pick them up when they’re full. Grease removal systems also usually produce used oils that can be recycled. Keep your used fat or oil in a sealed container and away from food, to stop any smells or pests. Make sure the area is clean and tidy.
Apply for a Trade Waste Consent as a Food Business
Anyone who operates a business or organisation at a trade premises within the Horowhenua District will need to register with Council on our Register for Trade Waste Customer page. This applies even to businesses which are not connected to the council wastewater network. We will assess the type and volume of trade waste (if any) that your business is discharging. Depending on how the business is classified a trade waste consent might be needed.
You can find out more about the registration and classification process on our Trade Waste page.